Coupled optical-thermal-fluid and structural analyses of novel light-trapping tubular panels for concentrating solar power receivers

NASA Astrophysics Data System (ADS)

Ortega, Jesus D.; Christian, Joshua M.; Yellowhair, Julius E.; Ho, Clifford K.

2015-09-01

Traditional tubular receivers used in concentrating solar power are formed using tubes connected to manifolds to form panels; which in turn are arranged in cylindrical or rectangular shapes. Previous and current tubular receivers, such as the ones used in Solar One, Solar Two, and most recently the Ivanpah solar plants, have used a black paint coating to increase the solar absorptance of the receiver. However, these coatings degrade over time and must be reapplied, increasing the receiver maintenance cost. This paper presents the thermal efficiency evaluation of novel receiver tubular panels that have a higher effective solar absorptance due to a light-trapping effect created by arranging the tubes in each panel into unique geometric configurations. Similarly, the impact of the incidence angle on the effective solar absorptance and thermal efficiency is evaluated. The overarching goal of this work is to achieve effective solar absorptances of ~90% and thermal efficiencies above 85% without using an absorptance coating. Several panel geometries were initially proposed and were down-selected based on structural analyses considering the thermal and pressure loading requirements of molten salt and supercritical carbon-dioxide receivers. The effective solar absorptance of the chosen tube geometries and panel configurations were evaluated using the ray-tracing modeling capabilities of SolTrace. The thermal efficiency was then evaluated by coupling computational fluid dynamics with the ray-tracing results using ANSYS Fluent. Compared to the base case analysis (flat tubular panel), the novel tubular panels have shown an increase in effective solar absorptance and thermal efficiency by several percentage points.

Thermal Impacts in Vibration-assisted Laser Deep Penetration Welding of Aluminum

NASA Astrophysics Data System (ADS)

Radel, T.

Mechanical vibrations affect the nucleation and grain growth conditions during welding. In order to understand the vibration-induced influences on the grain formation conditions in laser beam welding of aluminum the thermal impacts of simultaneously applied vibrations are analyzed in this study. Therefore, laser deep penetration welding at vibration frequencies between 0.5 kHz and 5 kHz is investigated. Besides full penetration, partial penetration experiments were carried out. The results show that the thermal and absorption efficiencies are not significantly affected by the applied excitation. The solidification time increases in case of applied excitation which is rather disadvantageous regarding grain refinement. Thus, mechanical-metallurgical and not thermal-metallurgical effects should be responsible for the change in grain nucleation and grain growth conditions in laser beam welding with simultaneously applied vibrations.

Technical assessment of discarded tires gasification as alternative technology for electricity generation.

PubMed

Machin, Einara Blanco; Pedroso, Daniel Travieso; de Carvalho, João Andrade

2017-10-01

Concern about contamination associated with the disposal of tires has led to the search for technologies to reuse discarded tires, which include the use of Tire Derived Fuel (TDF) as fuel in advanced thermal-conversion processes, this allows the energy use of these wastes at affordable costs and reduces the environmental impact on scrap tires disposal. A theoretical assessment of the technical viability of TDF gasification for electric and thermal power generation, from the producer gas combustion in an internal combustion engine and in a gas turbine, was performed. The combustion of producer gas derived from the gasification of TDF in an internal combustion engine driving a generator (ICE-G) appears as the more efficient route for electricity generation when compared with the efficiency obtained with the use of gas turbine (GT-G). A higher global efficiency, considering the electric and thermal generation efficiency can be expected with the use of TDF producer gas in GT-G, where is expected an overall efficiency of 77.49%. The assessment shows that is possible produces up to 7.67MJ and 10.62MJ of electric and thermal energy per kilogram of TDF gasified using an ICE-G and up to 6.06MJ and 13.03MJ of electric and thermal energy respectively per kilogram of gasified TDF using a GT-G. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermal feature extraction of servers in a datacenter using thermal image registration

NASA Astrophysics Data System (ADS)

Liu, Hang; Ran, Jian; Xie, Ting; Gao, Shan

2017-09-01

Thermal cameras provide fine-grained thermal information that enhances monitoring and enables automatic thermal management in large datacenters. Recent approaches employing mobile robots or thermal camera networks can already identify the physical locations of hot spots. Other distribution information used to optimize datacenter management can also be obtained automatically using pattern recognition technology. However, most of the features extracted from thermal images, such as shape and gradient, may be affected by changes in the position and direction of the thermal camera. This paper presents a method for extracting the thermal features of a hot spot or a server in a container datacenter. First, thermal and visual images are registered based on textural characteristics extracted from images acquired in datacenters. Then, the thermal distribution of each server is standardized. The features of a hot spot or server extracted from the standard distribution can reduce the impact of camera position and direction. The results of experiments show that image registration is efficient for aligning the corresponding visual and thermal images in the datacenter, and the standardization procedure reduces the impacts of camera position and direction on hot spot or server features.

Improving the thermal efficiency of a jaggery production module using a fire-tube heat exchanger.

PubMed

La Madrid, Raul; Orbegoso, Elder Mendoza; Saavedra, Rafael; Marcelo, Daniel

2017-12-15

Jaggery is a product obtained after heating and evaporation processes have been applied to sugar cane juice via the addition of thermal energy, followed by the crystallisation process through mechanical agitation. At present, jaggery production uses furnaces and pans that are designed empirically based on trial and error procedures, which results in low ranges of thermal efficiency operation. To rectify these deficiencies, this study proposes the use of fire-tube pans to increase heat transfer from the flue gases to the sugar cane juice. With the aim of increasing the thermal efficiency of a jaggery installation, a computational fluid dynamic (CFD)-based model was used as a numerical tool to design a fire-tube pan that would replace the existing finned flat pan. For this purpose, the original configuration of the jaggery furnace was simulated via a pre-validated CFD model in order to calculate its current thermal performance. Then, the newly-designed fire-tube pan was virtually replaced in the jaggery furnace with the aim of numerically estimating the thermal performance at the same operating conditions. A comparison of both simulations highlighted the growth of the heat transfer rate at around 105% in the heating/evaporation processes when the fire-tube pan replaced the original finned flat pan. This enhancement impacted the jaggery production installation, whereby the thermal efficiency of the installation increased from 31.4% to 42.8%. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development and Life Prediction of Erosion Resistant Turbine Low Conductivity Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

2010-01-01

Future rotorcraft propulsion systems are required to operate under highly-loaded conditions and in harsh sand erosion environments, thereby imposing significant material design and durability issues. The incorporation of advanced thermal barrier coatings (TBC) in high pressure turbine systems enables engine designs with higher inlet temperatures, thus improving the engine efficiency, power density and reliability. The impact and erosion resistance of turbine thermal barrier coating systems are crucial to the turbine coating technology application, because a robust turbine blade TBC system is a prerequisite for fully utilizing the potential coating technology benefit in the rotorcraft propulsion. This paper describes the turbine blade TBC development in addressing the coating impact and erosion resistance. Advanced thermal barrier coating systems with improved performance have also been validated in laboratory simulated engine erosion and/or thermal gradient environments. A preliminary life prediction modeling approach to emphasize the turbine blade coating erosion is also presented.

Environmental impact of thermal insulations: How do natural insulation products differ from synthetic ones?

NASA Astrophysics Data System (ADS)

Dovjak, M.; Košir, M.; Pajek, L.; Iglič, N.; Božiček, D.; Kunič, R.

2017-10-01

As the environmental awareness of the public is rising and at the same time contemporary buildings are becoming more and more energy efficient, the focus is shifting towards the usage of environmentally friendly building products. Human decisions are often driven by emotions and perceptions. Consequently, there exists a strong tendency towards preferring “natural” constructional products to the synthetic ones, especially in the case of thermal insulations. Life cycle assessment (LCA) has enabled an opportunity to widen the meaning of the word “environmentally friendly”, giving researchers and building designers an objective decision making tool to determine the environmental impact of building products, building components and buildings as a whole. The purpose of this study was to compare the environmental impact of various thermal insulations for the cradle to gate life cycle stages, based on a unified functional unit. Overall, 15 most commonly used thermal insulation products were analysed and classified into natural and synthetic groups. Based on the differentiation, we compared the impact in the selected environmental categories and identified the most influential environmental drivers. The results show that in some environmental categoriesnatural thermal insulations perform better (i.e. global warming potential), whilein others (i.e. eutrophication potential) they underperform. However, environmental impact trends can be identified, specifically for the natural and the synthetic materials.

Efficient quantum-classical method for computing thermal rate constant of recombination: application to ozone formation.

PubMed

Ivanov, Mikhail V; Babikov, Dmitri

2012-05-14

Efficient method is proposed for computing thermal rate constant of recombination reaction that proceeds according to the energy transfer mechanism, when an energized molecule is formed from reactants first, and is stabilized later by collision with quencher. The mixed quantum-classical theory for the collisional energy transfer and the ro-vibrational energy flow [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)] is employed to treat the dynamics of molecule + quencher collision. Efficiency is achieved by sampling simultaneously (i) the thermal collision energy, (ii) the impact parameter, and (iii) the incident direction of quencher, as well as (iv) the rotational state of energized molecule. This approach is applied to calculate third-order rate constant of the recombination reaction that forms the (16)O(18)O(16)O isotopomer of ozone. Comparison of the predicted rate vs. experimental result is presented.

Focused technology: Nuclear propulsion

NASA Technical Reports Server (NTRS)

Miller, Thomas J.

1991-01-01

The topics presented are covered in viewgraph form and include: nuclear thermal propulsion (NTP), which challenges (1) high temperature fuel and materials, (2) hot hydrogen environment, (3) test facilities, (4) safety, (5) environmental impact compliance, and (6) concept development, and nuclear electric propulsion (NEP), which challenges (1) long operational lifetime, (2) high temperature reactors, turbines, and radiators, (3) high fuel burn-up reactor fuels, and designs, (4) efficient, high temperature power conditioning, (5) high efficiency, and long life thrusters, (6) safety, (7) environmental impact compliance, and (8) concept development.

Application of multiple-point geostatistics to simulate the effect of small-scale aquifer heterogeneity on the efficiency of aquifer thermal energy storage

NASA Astrophysics Data System (ADS)

Possemiers, Mathias; Huysmans, Marijke; Batelaan, Okke

2015-08-01

Adequate aquifer characterization and simulation using heat transport models are indispensible for determining the optimal design for aquifer thermal energy storage (ATES) systems and wells. Recent model studies indicate that meter-scale heterogeneities in the hydraulic conductivity field introduce a considerable uncertainty in the distribution of thermal energy around an ATES system and can lead to a reduction in the thermal recoverability. In a study site in Bierbeek, Belgium, the influence of centimeter-scale clay drapes on the efficiency of a doublet ATES system and the distribution of the thermal energy around the ATES wells are quantified. Multiple-point geostatistical simulation of edge properties is used to incorporate the clay drapes in the models. The results show that clay drapes have an influence both on the distribution of thermal energy in the subsurface and on the efficiency of the ATES system. The distribution of the thermal energy is determined by the strike of the clay drapes, with the major axis of anisotropy parallel to the clay drape strike. The clay drapes have a negative impact (3.3-3.6 %) on the energy output in the models without a hydraulic gradient. In the models with a hydraulic gradient, however, the presence of clay drapes has a positive influence (1.6-10.2 %) on the energy output of the ATES system. It is concluded that it is important to incorporate small-scale heterogeneities in heat transport models to get a better estimate on ATES efficiency and distribution of thermal energy.

Application of multiple-point geostatistics to simulate the effect of small scale aquifer heterogeneity on the efficiency of Aquifer Thermal Energy Storage (ATES)

NASA Astrophysics Data System (ADS)

Possemiers, Mathias; Huysmans, Marijke; Batelaan, Okke

2015-04-01

Adequate aquifer characterization and simulation using heat transport models are indispensible for determining the optimal design for Aquifer Thermal Energy Storage (ATES) systems and wells. Recent model studies indicate that meter scale heterogeneities in the hydraulic conductivity field introduce a considerable uncertainty in the distribution of thermal energy around an ATES system and can lead to a reduction in the thermal recoverability. In this paper, the influence of centimeter scale clay drapes on the efficiency of a doublet ATES system and the distribution of the thermal energy around the ATES wells are quantified. Multiple-point geostatistical simulation of edge properties is used to incorporate the clay drapes in the models. The results show that clay drapes have an influence both on the distribution of thermal energy in the subsurface and on the efficiency of the ATES system. The distribution of the thermal energy is determined by the strike of the clay drapes, with the major axis of anisotropy parallel to the clay drape strike. The clay drapes have a negative impact (3.3 - 3.6%) on the energy output in the models without a hydraulic gradient. In the models with a hydraulic gradient, however, the presence of clay drapes has a positive influence (1.6 - 10.2%) on the energy output of the ATES system. It is concluded that it is important to incorporate small scale heterogeneities in heat transport models to get a better estimate on ATES efficiency and distribution of thermal energy.

Physiological performance of warm-adapted marine ectotherms: Thermal limits of mitochondrial energy transduction efficiency.

PubMed

Martinez, Eloy; Hendricks, Eric; Menze, Michael A; Torres, Joseph J

2016-01-01

Thermal regimes in aquatic systems have profound implications for the physiology of ectotherms. In particular, the effect of elevated temperatures on mitochondrial energy transduction in tropical and subtropical teleosts may have profound consequences on organismal performance and population viability. Upper and lower whole-organism critical temperatures for teleosts suggest that subtropical and tropical species are not susceptible to the warming trends associated with climate change, but sub-lethal effects on energy transduction efficiency and population dynamics remain unclear. The goal of the present study was to compare the thermal sensitivity of processes associated with mitochondrial energy transduction in liver mitochondria from the striped mojarra (Eugerres plumieri), the whitemouth croaker (Micropogonias furnieri) and the palometa (Trachinotus goodei), to those of the subtropical pinfish (Lagodon rhomboides) and the blue runner (Caranx crysos). Mitochondrial function was assayed at temperatures ranging from 10 to 40°C and results obtained for both tropical and subtropical species showed a reduction in the energy transduction efficiency of the oxidative phosphorylation (OXPHOS) system in most species studied at temperatures below whole-organism critical temperature thresholds. Our results show a loss of coupling between O2 consumption and ATP production before the onset of the critical thermal maxima, indicating that elevated temperature may severely impact the yield of ATP production per carbon unit oxidized. As warming trends are projected for tropical regions, increasing water temperatures in tropical estuaries and coral reefs could impact long-term growth and reproductive performance in tropical organisms, which are already close to their upper thermal limit. Copyright © 2015 Elsevier Inc. All rights reserved.

Environmental assessment of combustion modification controls for stationary internal combustion engines. Final report Sep 78-Jul 79

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lips, H.I.; Gotterba, J.A.; Lim, K.J.

1981-07-01

The report gives results of an environmental assessment of combustion modification techniques for stationary internal combustion engines, with respect to NOx control reduction effectiveness, operational impact, thermal efficiency impact, capital and annualized operating costs, and effects on emissions of pollutants other than NOx.

A combined thermal dissociation and electron impact ionization source for radioactive ion beam generation{sup a}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alton, G.D.; Williams, C.

1996-04-01

The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for radioactive ion beam (RIB) applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, inmore » principle, overcome this handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility, now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article. {copyright} {ital 1996 American Institute of Physics.}« less

A combined thermal dissociation and electron impact ionization source for radioactive ion beam generation (abstract){sup a}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alton, G.D.; Williams, C.

1996-03-01

The probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecular feed materials with conventional, hot-cathode, electron-impact ion sources is low and consequently, the ion beams from these sources often appear as mixtures of several molecular sideband beams. This fragmentation process leads to dilution of the intensity of the species of interest for radioactive ion beam (RIB) applications where beam intensity is at a premium. We have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high ionization efficiency characteristics of an electron impact ionization source that will, inmore » principle, overcome this handicap. The source concept will be evaluated as a potential candidate for use for RIB generation at the Holifield Radioactive Ion Beam Facility, now under construction at the Oak Ridge National Laboratory. The design features and principles of operation of the source are described in this article. {copyright} {ital 1996 American Institute of Physics.}« less

Refractory of Furnaces to Reduce Environmental Impact

NASA Astrophysics Data System (ADS)

Hanzawa, Shigeru

2011-10-01

The energy load of furnaces used in the manufacturing process of ceramics is quite large. Most of the environmental impact of ceramics manufacturing is due to the CO2 produced from this high energy load. To improve this situation, R&D has focused on furnace systems and techniques of control in order to reduce energy load. Since furnaces are comprised of refractory, consideration of their mechanical and thermal characteristics is important. Herein are described several refractory types which were chosen through comparison of the characteristics which contribute to heat capacity reduction, heat insulating reinforcement and high emissivity, thereby improving thermal radiation heat transfer efficiency to the ceramic articles. One selected refractory material which will reduce the environmental impact of a furnace, chosen considering low heat capacity and high emissivity characteristics, is SiC. In this study, thermal radiation heat transfer efficiency improvement and its effect on ceramic articles in the furnace and oxidation behaviour were investigated at 1700K. A high density SiC refractory, built into the furnace at construction, has relatively high oxidation durability and has the ability to reduce environmental impact-CO2 by 10 percent by decreasing the furnace's energy load. However, new oxidation prevention techniques for SiC will be necessary for long-term use in industrial furnaces, because passive to active oxidation transition behaviour of commercial SiC refractory is coming to close ideal.

Fire-tube boiler optimization criteria and efficiency indicators rational values defining

NASA Astrophysics Data System (ADS)

Batrakov, P. A.; Mikhailov, A. G.; Ignatov, V. Yu

2018-01-01

Technical and economic calculations problems solving with the aim of identifying the opportunity to recommend the project for industrial implementation are represented in the paper. One of the main determining factors impacting boiler energy efficiency is the exhaust gases temperature, as well as the furnace volume thermal stress. Fire-tube boilers with different types of furnaces are considered in the study. The fullest analysis of the boiler performance thermal and technical indicators for the following engineering problem: Q=idem, M=idem and evaluation according to η, B is presented. The furnace with the finned ellipse profile application results in the fuel consumption decrease due to a more efficient heat exchange surface of the furnace compared to other examined ones.

Energetic performance analysis of a commercial water-based photovoltaic thermal system (PV/T) under summer conditions

NASA Astrophysics Data System (ADS)

Nardi, I.; Ambrosini, D.; de Rubeis, T.; Paoletti, D.; Muttillo, M.; Sfarra, S.

2017-11-01

In the last years, the importance of integrating the production of electricity with the production of sanitary hot water led to the development of new solutions, i.e. PV/T systems. It is well known that hybrid photovoltaic-thermal systems, able to produce electricity and thermal energy at the same time with better energetic performance in comparison with two separate systems, present many advantages for application in a residential building. A PV/T is constituted generally by a common PV panel with a metallic pipe, in which fluid flows. Pipe accomplishes two roles: it absorbs the heat from the PV panel, thus increasing, or at least maintaining its efficiency; furthermore, it stores the heat for sanitary uses. In this work, the thermal and electrical efficiencies of a commercial PV/T panel have been evaluated during the summer season in different days, to assess the effect of environmental conditions on the system total efficiency. Moreover, infrared thermographic diagnosis in real time has been effected during the operating mode in two conditions: with cooling and without cooling; cooling was obtained by natural flowing water. This analysis gave information about the impact of a non-uniform temperature distribution on the thermal and electrical performance. Furthermore, measurements have been performed in two different operating modes: 1) production of solely electrical energy and 2) simultaneous production of thermal and electrical energy. Finally, total efficiency is largely increased by using a simple solar concentrator nearby the panel.

Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate

PubMed Central

Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

2016-01-01

Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion. PMID:27113558

Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate.

PubMed

Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

2016-04-26

Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion.

Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate

NASA Astrophysics Data System (ADS)

Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

2016-04-01

Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion.

Energy Savings Through Thermally Efficient Crucible Technology: Fundamentals, Process Modeling, and Applications

NASA Astrophysics Data System (ADS)

Shi, Wenwu; Pinto, Brian

2017-12-01

Melting and holding molten metals within crucibles accounts for a large portion of total energy demand in the resource-intensive nonferrous foundry industry. Multivariate mathematical modeling aided by detailed material characterization and advancements in crucible technologies can make a significant impact in the areas of cost-efficiency and carbon footprint reduction. Key thermal properties such as conductivity and specific heat capacity were studied to understand their influence on crucible furnace energy consumption during melting and holding processes. The effects of conductivity on thermal stresses and longevity of crucibles were also evaluated. With this information, accurate theoretical models using finite element analysis were developed to study total energy consumption and melting time. By applying these findings to recent crucible developments, considerable improvements in field performance were reported and documented as case studies in applications such as aluminum melting and holding.

Impact of shade on outdoor thermal comfort—a seasonal field study in Tempe, Arizona

NASA Astrophysics Data System (ADS)

Middel, Ariane; Selover, Nancy; Hagen, Björn; Chhetri, Nalini

2016-12-01

Shade plays an important role in designing pedestrian-friendly outdoor spaces in hot desert cities. This study investigates the impact of photovoltaic canopy shade and tree shade on thermal comfort through meteorological observations and field surveys at a pedestrian mall on Arizona State University's Tempe campus. During the course of 1 year, on selected clear calm days representative of each season, we conducted hourly meteorological transects from 7:00 a.m. to 6:00 p.m. and surveyed 1284 people about their thermal perception, comfort, and preferences. Shade lowered thermal sensation votes by approximately 1 point on a semantic differential 9-point scale, increasing thermal comfort in all seasons except winter. Shade type (tree or solar canopy) did not significantly impact perceived comfort, suggesting that artificial and natural shades are equally efficient in hot dry climates. Globe temperature explained 51 % of the variance in thermal sensation votes and was the only statistically significant meteorological predictor. Important non-meteorological factors included adaptation, thermal comfort vote, thermal preference, gender, season, and time of day. A regression of subjective thermal sensation on physiological equivalent temperature yielded a neutral temperature of 28.6 °C. The acceptable comfort range was 19.1 °C-38.1 °C with a preferred temperature of 20.8 °C. Respondents exposed to above neutral temperature felt more comfortable if they had been in air-conditioning 5 min prior to the survey, indicating a lagged response to outdoor conditions. Our study highlights the importance of active solar access management in hot urban areas to reduce thermal stress.

An assessment of efficient water heating options for an all-electric single family residence in a mixed-humid climate.

PubMed

Balke, Elizabeth C; Healy, William M; Ullah, Tania

2016-12-01

An evaluation of a variety of efficient water heating strategies for an all-electric single family home located in a mixed-humid climate is conducted using numerical modeling. The strategies considered include various combinations of solar thermal, heat pump, and electric resistance water heaters. The numerical model used in the study is first validated against a year of field data obtained on a dual-tank system with a solar thermal preheat tank feeding a heat pump water heater that serves as a backup. Modeling results show that this configuration is the most efficient of the systems studied over the course of a year, with a system coefficient of performance (COP sys ) of 2.87. The heat pump water heater alone results in a COP sys of 1.9, while the baseline resistance water heater has a COP sys of 0.95. Impacts on space conditioning are also investigated by considering the extra energy consumption required of the air source heat pump to remove or add heat from the conditioned space by the water heating system. A modified COP sys that incorporates the heat pump energy consumption shows a significant drop in efficiency for the dual tank configuration since the heat pump water heater draws the most heat from the space in the heating season while the high temperatures in the solar storage tank during the cooling season result in an added heat load to the space. Despite this degradation in the COP sys , the combination of the solar thermal preheat tank and the heat pump water heater is the most efficient option even when considering the impacts on space conditioning.

An assessment of efficient water heating options for an all-electric single family residence in a mixed-humid climate

PubMed Central

Balke, Elizabeth C.; Healy, William M.; Ullah, Tania

2016-01-01

An evaluation of a variety of efficient water heating strategies for an all-electric single family home located in a mixed-humid climate is conducted using numerical modeling. The strategies considered include various combinations of solar thermal, heat pump, and electric resistance water heaters. The numerical model used in the study is first validated against a year of field data obtained on a dual-tank system with a solar thermal preheat tank feeding a heat pump water heater that serves as a backup. Modeling results show that this configuration is the most efficient of the systems studied over the course of a year, with a system coefficient of performance (COPsys) of 2.87. The heat pump water heater alone results in a COPsys of 1.9, while the baseline resistance water heater has a COPsys of 0.95. Impacts on space conditioning are also investigated by considering the extra energy consumption required of the air source heat pump to remove or add heat from the conditioned space by the water heating system. A modified COPsys that incorporates the heat pump energy consumption shows a significant drop in efficiency for the dual tank configuration since the heat pump water heater draws the most heat from the space in the heating season while the high temperatures in the solar storage tank during the cooling season result in an added heat load to the space. Despite this degradation in the COPsys, the combination of the solar thermal preheat tank and the heat pump water heater is the most efficient option even when considering the impacts on space conditioning. PMID:27990058

Evaluation of annual efficiencies of high temperature central receiver concentrated solar power plants with thermal energy storage.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehrhart, Brian David; Gill, David Dennis

The current study has examined four cases of a central receiver concentrated solar power plant with thermal energy storage using the DELSOL and SOLERGY computer codes. The current state-of-the-art base case was compared with a theoretical high temperature case which was based on the scaling of some input parameters and the estimation of other parameters based on performance targets from the Department of Energy SunShot Initiative. This comparison was done for both current and high temperature cases in two configurations: a surround field with an external cylindrical receiver and a north field with a single cavity receiver. There is amore » fairly dramatic difference between the design point and annual average performance, especially in the solar field and receiver subsystems, and also in energy losses due to the thermal energy storage being full to capacity. Additionally, there are relatively small differences (<2%) in annual average efficiencies between the Base and High Temperature cases, despite an increase in thermal to electric conversion efficiency of over 8%. This is due the increased thermal losses at higher temperature and operational losses due to subsystem start-up and shut-down. Thermal energy storage can mitigate some of these losses by utilizing larger thermal energy storage to ensure that the electric power production system does not need to stop and re-start as often, but solar energy is inherently transient. Economic and cost considerations were not considered here, but will have a significant impact on solar thermal electric power production strategy and sizing.« less

Electron acceleration in solar flares and the transition from nonthermal to thermal hard X-ray phases

NASA Technical Reports Server (NTRS)

Smith, D. F.

1985-01-01

Observations are reviewed which indicate that hard X-rays during the impulsive phase of a flare typically start with a primarily nonthermal phase which undergoes a transition to a primarily thermal phase as the flare progresses. Recent theoretical work on the modified two-stream instability as an efficient electron accelerator and modeling of thermal hard X-ray sources is considered. A scenario which is termed the dissipative thermal model is proposed to explain the observations. Fast tearing modes occurring in a loop give rise to cross-field ion motion. This in turn excites the modified two-stream instability which converts about 50 percent of the ion energy into accelerated electrons along the loop as long as the plasma beta is less than 0.3. These electrons impact the chromosphere and boil off a part of it which rises up the loop. This density increase coupled with the temperature increase due to tearing causes the beta to increase beyond 0.3 and efficient electron acceleration ceases. This leads to the primarily thermal phase.

Solar thermal electric hybridization issues

NASA Astrophysics Data System (ADS)

Williams, Tom A.; Bohn, Mark S.; Price, Henry W.

1994-10-01

Solar thermal electric systems have an advantage over many other renewable energy technologies because the former use heat as an intermediate energy carrier. This is an advantage, as it allows for a relatively simple method of hybridization by using heat from fossil-fuel. Hybridization of solar thermal electric systems is a topic that has recently generated significant interest and controversy and has led to many diverse opinions. This paper discusses many of the issues associated with hybridization of solar thermal electric systems such as what role hybridization should play; how it should be implemented; what are the efficiency, environmental, and cost implications; what solar fraction is appropriate; how hybrid systems compete with solar-only systems; and how hybridization can impact commercialization efforts for solar thermal electric systems.

Convergent spray process for environmentally friendly coatings

NASA Technical Reports Server (NTRS)

Scarpa, Jack

1995-01-01

Conventional spray application processes have poor transfer efficiencies, resulting in an exorbitant loss in materials, solvents, and time. Also, with ever tightening Environmental Protection Agency (EPA) regulations and Occupational Safety and Health Administration requirements, the low transfer efficiencies have a significant impact on the quantities of materials and solvents that are released into the environment. High solids spray processes are also limited by material viscosities, thus requiring many passes over the surface to achieve a thickness in the 0.125 -inch range. This results in high application costs and a negative impact on the environment. Until recently, requirements for a 100 percent solid sprayable, environmentally friendly, lightweight thermal protection system that can be applied in a thick (greater than 0.125 inch) single-pass operation exceeded the capability of existing systems. Such coatings must be applied by hand lay-up techniques, especially for thermal and/or fire protection systems. The current formulation of these coatings has presented many problems such as worker safety, environmental hazards, waste, high cost, and application constraints. A system which can apply coatings without using hazardous materials would alleviate many of these problems. Potential applications include the aerospace thermal protective specialty coatings, chemical and petroleum industries that require fire-protection coatings that resist impact, chemicals, and weather. These markets can be penetrated by offering customized coatings applied by automated processes that are environmentally friendly.

Forward-facing cavity and opposing jet combined thermal protection system

NASA Astrophysics Data System (ADS)

Lu, H. B.; Liu, W. Q.

2012-12-01

This paper focuses on the design of a forward-facing cavity and opposing jet combined configuration for thermal protection system (TPS) of hypersonic vehicles. The cooling efficiency of the combined TPS was investigated numerically, and the numerical method was validated by the related experiment in the open literature. The flow field parameters, aerodynamic force, and surface heat flux distribution were obtained. The detailed numerical results show that this kind of combined TPS has an excellent impact on cooling the nose-tip, and it is suitable for the thermal protection of hypersonic vehicles which require long-range and time to cruise.

Benefit or burden? Perceptions of energy efficiency efforts among low-income housing residents in New York City.

PubMed

Hernández, Diana; Phillips, Douglas

2015-07-01

Low-income households contend with high energy costs and poor thermal comfort due to poor structural conditions and energy inefficiencies in their homes. Energy efficiency upgrades can potentially reduce energy expenses and improve thermal comfort, while also addressing problematic issues in the home environment. The present mixed method pilot study explored the impacts of energy efficiency upgrades in 20 households in a low-income community in New York City. Surveys and interviews were administered to the heads of household in a variety of housing types. Interviews were also conducted with landlords of buildings that had recently undergone upgrades. Findings indicate that energy efficiency measures resulted in improved thermal comfort, enhanced health and safety and reduced energy costs. Participants reported largely positive experiences with the upgrades, resulting in direct and indirect benefits. However, results also indicate negative consequences associated with the upgrades and further illustrate that weatherization alone was insufficient to address all of the issues facing low-income households. Moreover, qualitative results revealed differing experiences of low-income renters compared to homeowners. Overall, energy efficiency upgrades are a promising intervention to mitigate the energy and structurally related challenges facing low-income households, but larger scale research is needed to capture the long-term implications of these upgrades.

Benefit or burden? Perceptions of energy efficiency efforts among low-income housing residents in New York City☆

PubMed Central

Hernández, Diana; Phillips, Douglas

2016-01-01

Low-income households contend with high energy costs and poor thermal comfort due to poor structural conditions and energy inefficiencies in their homes. Energy efficiency upgrades can potentially reduce energy expenses and improve thermal comfort, while also addressing problematic issues in the home environment. The present mixed method pilot study explored the impacts of energy efficiency upgrades in 20 households in a low-income community in New York City. Surveys and interviews were administered to the heads of household in a variety of housing types. Interviews were also conducted with landlords of buildings that had recently undergone upgrades. Findings indicate that energy efficiency measures resulted in improved thermal comfort, enhanced health and safety and reduced energy costs. Participants reported largely positive experiences with the upgrades, resulting in direct and indirect benefits. However, results also indicate negative consequences associated with the upgrades and further illustrate that weatherization alone was insufficient to address all of the issues facing low-income households. Moreover, qualitative results revealed differing experiences of low-income renters compared to homeowners. Overall, energy efficiency upgrades are a promising intervention to mitigate the energy and structurally related challenges facing low-income households, but larger scale research is needed to capture the long-term implications of these upgrades. PMID:27054092

Effect of the thermal environment on the efficiency of packed columns in supercritical fluid chromatography.

PubMed

Zauner, Jordan; Lusk, Ryan; Koski, Steven; Poe, Donald P

2012-11-30

When a packed column is operated at temperatures and pressures near the critical point in supercritical fluid chromatography, the thermal environment in which it is placed has a significant impact on retention and efficiency. We measured the retention factors, plate heights, and related parameters for elution of a test mixture of alkylbenzenes with 5% methanol/95% carbon dioxide mobile phase on a 250 mm × 4.6 mm i.d. column packed with 5-micron Luna-C18 particles. Separations were performed at outlet pressures from 100 to 150 bar and a column oven temperature of 323K. For a bare column thermostated with convective air, significant efficiency losses were observed for outlet pressures equal to or less than 120 bar. These large efficiency losses are attributed to radial temperature gradients. Addition of foam insulation resulted in significant improvements in efficiency. Operating the column in still air using a commercially available column heater provided the best overall performance, with no measurable efficiency loss over the entire range of pressures studied. A reduced plate height of 1.88 was obtained at an optimum flow rate of 3.0 mL/min at 100 bar outlet pressure and with the temperature of the incoming mobile phase set approximately 2.3K above the temperature of the column oven. Retention time repeatability for all three thermal conditions was equal to or less than 0.5% RSD. These results demonstrate that it is possible to perform fast, efficient separations with excellent repeatability using SFC under near-critical conditions if the thermal environment is optimized to minimize the generation of radial temperature gradients. Copyright © 2012 Elsevier B.V. All rights reserved.

Impact of initial biodegradability on sludge anaerobic digestion enhancement by thermal pretreatment.

PubMed

Carrère, Hélène; Bougrier, Claire; Castets, Delphine; Delgenès, Jean Philippe

2008-11-01

Thermal treatments with temperature ranging from 60 to 210 degrees C were applied to 6 waste-activated sludge samples originating from high or medium load, extended aeration wastewater treatment processes that treated different wastewaters (urban, urban and industrial or slaughterhouse). COD sludge solubilisation was linearly correlated with the treatment temperature on the whole temperature range and independently of the sludge samples. Sludge batch mesophilic biodegradability increased with treatment temperature up to 190 degrees C. In this temperature range, biodegradability enhancement or methane production increase by thermal hydrolysis was shown to be a function of sludge COD solubilisation but also of sludge initial biodegradability. The lower the initial biodegradability means the higher efficiency of thermal treatment.

Environmental Impacts of a Multi-Borehole Geothermal System: Model Sensitivity Study

NASA Astrophysics Data System (ADS)

Krol, M.; Daemi, N.

2017-12-01

Problems associated with fossil fuel consumption has increased worldwide interest in discovering and developing sustainable energy systems. One such system is geothermal heating, which uses the constant temperature of the ground to heat or cool buildings. Since geothermal heating offers low maintenance, high heating/cooling comfort, and a low carbon footprint, compared to conventional systems, there has been an increasing trend in equipping large buildings with geothermal heating. However, little is known on the potential environmental impact geothermal heating can have on the subsurface, such as the creation of subsurface thermal plumes or changes in groundwater flow dynamics. In the present study, the environmental impacts of a closed-loop, ground source heat pump (GSHP) system was examined with respect to different system parameters. To do this a three-dimensional model, developed using FEFLOW, was used to examine the thermal plumes resulting from ten years of operation of a vertical closed-loop GSHP system with multiple boreholes. A required thermal load typical of an office building located in Canada was calculated and groundwater flow and heat transport in the geological formation was simulated. Consequently, the resulting thermal plumes were studied and a sensitivity analysis was conducted to determine the effect of different parameters like groundwater flow and soil type on the development and movement of thermal plumes. Since thermal plumes can affect the efficiency of a GSHP system, this study provides insight into important system parameters.

Thermal Analysis of a Structural Solution for Sustainable, Modular and Prefabricated Buildings

NASA Astrophysics Data System (ADS)

Isopescu, D. N.; Maxineasa, S. G.; Neculai, O.

2017-06-01

In the construction field, the design principles for an efficient and operational use of buildings and a minimal impact on the environment are essential aspects of sustainable development. In this regard, several aspects must be taken into consideration, such as: durability, easy maintenance, flexibility in interior design, and reduced energy consumption. Decreasing energy consumption in buildings during the service life (heating / cooling / drinking water / electricity) can mean lower costs, but also a lower impact on the environment. The paper presents the thermal analysis for a GF+1F height structure, consisting of several identical, adjacent and / or overlapped metallic cubic modules. The spaces inside this cubes ensemble solve the functionality of a family home building. The good carrying capacity, the rapidity of execution, the superior degree of thermal insulation and the minimum losses of material in execution were the main advantages provided by this structural solution. Regarding the thermal comfort for the users of this constructive system, the thermal analysis showed that the internal temperatures are constant and uniform, without cold surfaces or temperature fluctuations. In addition, humidity is controlled and there is no risk of condensation.

Impact of thermal processing on the activity of gallotannins and condensed tannins from Hamamelis virginiana used as functional ingredients in seafood.

PubMed

González, María Jesús; Torres, Josep Lluís; Medina, Isabel

2010-04-14

Phenolic extracts from witch hazel, Hamamelis virginiana, are efficient antioxidants against fish lipid peroxidation. The impact of fish thermal processes on the hydrolyzable polyphenols from this source was studied. H. virginiana polyphenols included 80% of hydrolyzable tannins, characterized by a mixture of glucose gallates containing from 5 to 10 units of gallic acid, hamamelitannin, and 20% of proanthocyanidins. Structural modifications of the polyphenols during thermal processes were determined by HPLC-MS. Changes in their reducing and free radical scavenging capacities as a result of high temperatures were also determined. Thermal processes triggered a significant breakdown of hydrolyzable tannins with 6-10 galloyl units to give pentagalloyl glucose (PGG). The release of high concentrations of free gallic acid especially in long-term thermally processed samples leads to an increase of the antioxidant ability of heated H. virginiana extracts. Such an increase was evidenced by an increment in the reducing and radical scavenging capacities as well as an improvement in the antioxidant effectiveness for inhibiting lipid oxidation of processed fatty fish muscle.

Thermal pollution impacts on rivers and power supply in the Mississippi River watershed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miara, Ariel; Vorosmarty, Charles J.; Macknick, Jordan E.

Thermal pollution from power plants degrades riverine ecosystems with ramifications beyond the natural environment as it affects power supply. The transport of thermal effluents along river reaches may lead to plant-to-plant interferences by elevating condenser inlet temperatures at downstream locations, which lower thermal efficiencies and trigger regulatory-forced power curtailments. We evaluate thermal pollution impacts on rivers and power supply across 128 plants with once-through cooling technologies in the Mississippi River watershed. By leveraging river network topologies with higher resolutions (0.05 degrees) than previous studies, we reveal the need to address the issue in a more spatially resolved manner, capable ofmore » uncovering diverse impacts across individual plants, river reaches and sub-basins. Results show that the use of coarse river network resolutions may lead to substantial overestimations in magnitude and length of impaired river reaches. Overall, there is a modest limitation on power production due to thermal pollution, given existing infrastructure, regulatory and climate conditions. However, tradeoffs between thermal pollution and electricity generation show important implications for the role of alternative cooling technologies and environmental regulation under current and future climates. Recirculating cooling technologies may nearly eliminate thermal pollution and improve power system reliability under stressed climate-water conditions. Regulatory limits also reduce thermal pollution, but at the expense of significant reductions in electricity generation capacity. However, results show several instances when power production capacity rises at individual plants when regulatory limits reduce upstream thermal pollution. Furthermore, these dynamics across energy-water systems highlight the need for high-resolution simulations and the value of coherent planning and optimization across infrastructure with mutual dependencies on natural resources to overcome climate-water constraints on productivity and bring to fruition energy and environmental win-win opportunities.« less

Thermal pollution impacts on rivers and power supply in the Mississippi River watershed

DOE PAGES

Miara, Ariel; Vorosmarty, Charles J.; Macknick, Jordan E.; ...

2018-03-08

Thermal pollution from power plants degrades riverine ecosystems with ramifications beyond the natural environment as it affects power supply. The transport of thermal effluents along river reaches may lead to plant-to-plant interferences by elevating condenser inlet temperatures at downstream locations, which lower thermal efficiencies and trigger regulatory-forced power curtailments. We evaluate thermal pollution impacts on rivers and power supply across 128 plants with once-through cooling technologies in the Mississippi River watershed. By leveraging river network topologies with higher resolutions (0.05 degrees) than previous studies, we reveal the need to address the issue in a more spatially resolved manner, capable ofmore » uncovering diverse impacts across individual plants, river reaches and sub-basins. Results show that the use of coarse river network resolutions may lead to substantial overestimations in magnitude and length of impaired river reaches. Overall, there is a modest limitation on power production due to thermal pollution, given existing infrastructure, regulatory and climate conditions. However, tradeoffs between thermal pollution and electricity generation show important implications for the role of alternative cooling technologies and environmental regulation under current and future climates. Recirculating cooling technologies may nearly eliminate thermal pollution and improve power system reliability under stressed climate-water conditions. Regulatory limits also reduce thermal pollution, but at the expense of significant reductions in electricity generation capacity. However, results show several instances when power production capacity rises at individual plants when regulatory limits reduce upstream thermal pollution. Furthermore, these dynamics across energy-water systems highlight the need for high-resolution simulations and the value of coherent planning and optimization across infrastructure with mutual dependencies on natural resources to overcome climate-water constraints on productivity and bring to fruition energy and environmental win-win opportunities.« less

Thermal pollution impacts on rivers and power supply in the Mississippi River watershed

NASA Astrophysics Data System (ADS)

Miara, Ariel; Vörösmarty, Charles J.; Macknick, Jordan E.; Tidwell, Vincent C.; Fekete, Balazs; Corsi, Fabio; Newmark, Robin

2018-03-01

Thermal pollution from power plants degrades riverine ecosystems with ramifications beyond the natural environment as it affects power supply. The transport of thermal effluents along river reaches may lead to plant-to-plant interferences by elevating condenser inlet temperatures at downstream locations, which lower thermal efficiencies and trigger regulatory-forced power curtailments. We evaluate thermal pollution impacts on rivers and power supply across 128 plants with once-through cooling technologies in the Mississippi River watershed. By leveraging river network topologies with higher resolutions (0.05°) than previous studies, we reveal the need to address the issue in a more spatially resolved manner, capable of uncovering diverse impacts across individual plants, river reaches and sub-basins. Results show that the use of coarse river network resolutions may lead to substantial overestimations in magnitude and length of impaired river reaches. Overall, there is a modest limitation on power production due to thermal pollution, given existing infrastructure, regulatory and climate conditions. However, tradeoffs between thermal pollution and electricity generation show important implications for the role of alternative cooling technologies and environmental regulation under current and future climates. Recirculating cooling technologies may nearly eliminate thermal pollution and improve power system reliability under stressed climate-water conditions. Regulatory limits also reduce thermal pollution, but at the expense of significant reductions in electricity generation capacity. However, results show several instances when power production capacity rises at individual plants when regulatory limits reduce upstream thermal pollution. These dynamics across energy-water systems highlight the need for high-resolution simulations and the value of coherent planning and optimization across infrastructure with mutual dependencies on natural resources to overcome climate-water constraints on productivity and bring to fruition energy and environmental win-win opportunities.

Impact of shade on outdoor thermal comfort-a seasonal field study in Tempe, Arizona.

PubMed

Middel, Ariane; Selover, Nancy; Hagen, Björn; Chhetri, Nalini

2016-12-01

Shade plays an important role in designing pedestrian-friendly outdoor spaces in hot desert cities. This study investigates the impact of photovoltaic canopy shade and tree shade on thermal comfort through meteorological observations and field surveys at a pedestrian mall on Arizona State University's Tempe campus. During the course of 1 year, on selected clear calm days representative of each season, we conducted hourly meteorological transects from 7:00 a.m. to 6:00 p.m. and surveyed 1284 people about their thermal perception, comfort, and preferences. Shade lowered thermal sensation votes by approximately 1 point on a semantic differential 9-point scale, increasing thermal comfort in all seasons except winter. Shade type (tree or solar canopy) did not significantly impact perceived comfort, suggesting that artificial and natural shades are equally efficient in hot dry climates. Globe temperature explained 51 % of the variance in thermal sensation votes and was the only statistically significant meteorological predictor. Important non-meteorological factors included adaptation, thermal comfort vote, thermal preference, gender, season, and time of day. A regression of subjective thermal sensation on physiological equivalent temperature yielded a neutral temperature of 28.6 °C. The acceptable comfort range was 19.1 °C-38.1 °C with a preferred temperature of 20.8 °C. Respondents exposed to above neutral temperature felt more comfortable if they had been in air-conditioning 5 min prior to the survey, indicating a lagged response to outdoor conditions. Our study highlights the importance of active solar access management in hot urban areas to reduce thermal stress.

Experimental evidence of impact ignition: 100-fold increase of neutron yield by impactor collision.

PubMed

Azechi, H; Sakaiya, T; Watari, T; Karasik, M; Saito, H; Ohtani, K; Takeda, K; Hosoda, H; Shiraga, H; Nakai, M; Shigemori, K; Fujioka, S; Murakami, M; Nagatomo, H; Johzaki, T; Gardner, J; Colombant, D G; Bates, J W; Velikovich, A L; Aglitskiy, Y; Weaver, J; Obenschain, S; Eliezer, S; Kodama, R; Norimatsu, T; Fujita, H; Mima, K; Kan, H

2009-06-12

We performed integrated experiments on impact ignition, in which a portion of a deuterated polystyrene (CD) shell was accelerated to about 600 km/s and was collided with precompressed CD fuel. The kinetic energy of the impactor was efficiently converted into thermal energy generating a temperature of about 1.6 keV. We achieved a two-order-of-magnitude increase in the neutron yield by optimizing the timing of the impact collision, demonstrating the high potential of impact ignition for fusion energy production.

Die attach dimension and material on thermal conductivity study for high power COB LED

NASA Astrophysics Data System (ADS)

Sarukunaselan, K.; Ong, N. R.; Sauli, Z.; Mahmed, N.; Kirtsaeng, S.; Sakuntasathien, S.; Suppiah, S.; Alcain, J. B.; Retnasamy, V.

2017-09-01

High power LED began to gain popularity in the semiconductor market due to its efficiency and luminance. Nonetheless, along with the increased in efficiency, there was an increased in the junction temperature too. The alleviating junction temperature is undesirable since the performances and lifetime will be degraded over time. Therefore, it is crucial to solve this thermal problem by maximizing the heat dissipation to the ambience. Improvising the die attach (DA) layer would be the best option because this layer is sandwiched between the chip (heat source) and the substrate (channel to the ambient). In this paper, the impact of thickness and thermal conductivity onto the junction temperature and Von Mises stress is analyzed. Results obtained showed that the junction temperature is directly proportional to the thickness but the stress was inversely proportional to the thickness of the DA. The thermal conductivity of the materials did affect the junction temperature as there was not much changes once the thermal conductivity reached 20W/mK. However, no significant changes were observed on the Von Mises stress caused by the thermal conductivity. Material with the second highest thermal conductivity had the lowest stress, whereas the highest conductivity material had the highest stress value at 20 µm. Overall, silver sinter provided the best thermal dissipation compared to the other materials.

Impact of rough potentials in rocked ratchet performance

NASA Astrophysics Data System (ADS)

Camargo, S.; Anteneodo, C.

2018-04-01

We consider thermal ratchets modeled by overdamped Brownian motion in a spatially periodic potential with a tilting process, both unbiased on average. We investigate the impact of the introduction of roughness in the potential profile, over the flux and efficiency of the ratchet. Both amplitude and wavelength that characterize roughness are varied. We show that depending on the ratchet parameters, rugosity can either spoil or enhance the ratchet performance.

Final Report: Utilizing Alternative Fuel Ignition Properties to Improve SI and CI Engine Efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wooldridge, Margaret; Boehman, Andre; Lavoie, George

Experimental and modeling studies were completed to explore leveraging physical and chemical fuel properties for improved thermal efficiency of internal combustion engines. Fundamental studies of the ignition chemistry of ethanol and iso-octane blends and constant volume spray chamber studies of gasoline and diesel sprays supported the core research effort which used several reciprocating engine platforms. Single cylinder spark ignition (SI) engine studies were carried out to characterize the impact of ethanol/gasoline, syngas (H 2 and CO)/gasoline and other oxygenate/gasoline blends on engine performance. The results of the single-cylinder engine experiments and other data from the literature were used to trainmore » a GT Power model and to develop a knock criteria based on reaction chemistry. The models were used to interpret the experimental results and project future performance. Studies were also carried out using a state of the art, direct injection (DI) turbocharged multi- cylinder engine with piezo-actuated fuel injectors to demonstrate the promising spray and spark timing strategies from single-cylinder engine studies on the multi-cylinder engine. Key outcomes and conclusions of the studies were: 1. Efficiency benefits of ethanol and gasoline fuel blends were consistent and substantial (e.g. 5-8% absolute improvement in gross indicated thermal efficiency (GITE)). 2. The best ethanol/gasoline blend (based on maximum thermal efficiency) was determined by the engine hardware and limits based on component protection (e.g. peak in-cylinder pressure or maximum turbocharger inlet temperature) – and not by knock limits. Blends with <50% ethanol delivered significant thermal efficiency gains with conventional SI hardware while maintain good safety integrity to the engine hardware. 3. Other compositions of fuel blends including syngas (H 2 and CO) and other dilution strategies provided significant efficiency gains as well (e.g. 5% absolute improvement in ITE). 4. When the combination of engine and fuel system is not knock limited, multiple fuel injection events maintain thermal efficiency while improving engine-out emissions (e.g. CO, UHC, and particulate number).« less

Design Considerations of a Solid State Thermal Energy Storage

NASA Astrophysics Data System (ADS)

Janbozorgi, Mohammad; Houssainy, Sammy; Thacker, Ariana; Ip, Peggy; Ismail, Walid; Kavehpour, Pirouz

2016-11-01

With the growing governmental restrictions on carbon emission, renewable energies are becoming more prevalent. A reliable use of a renewable source however requires a built-in storage to overcome the inherent intermittent nature of the available energy. Thermal design of a solid state energy storage has been investigated for optimal performance. The impact of flow regime, laminar vs. turbulent, on the design and sizing of the system is also studied. The implications of low thermal conductivity of the storage material are discussed and a design that maximizes the round trip efficiency is presented. This study was supported by Award No. EPC-14-027 Granted by California Energy Commission (CEC).

Thermal effects in an ultrafast BiB 3O 6 optical parametric oscillator at high average powers

DOE PAGES

Petersen, T.; Zuegel, J. D.; Bromage, J.

2017-08-15

An ultrafast, high-average-power, extended-cavity, femtosecond BiB 3O 6 optical parametric oscillator was constructed as a test bed for investigating the scalability of infrared parametric devices. Despite the high pulse energies achieved by this system, the reduction in slope efficiency near the maximum-available pump power prompted the investigation of thermal effects in the crystal during operation. Furthermore, the local heating effects in the crystal were used to determine the impact on both phase matching and thermal lensing to understand limitations that must be overcome to achieve microjoule-level pulse energies at high repetition rates.

Thermal effects in an ultrafast BiB 3O 6 optical parametric oscillator at high average powers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petersen, T.; Zuegel, J. D.; Bromage, J.

An ultrafast, high-average-power, extended-cavity, femtosecond BiB 3O 6 optical parametric oscillator was constructed as a test bed for investigating the scalability of infrared parametric devices. Despite the high pulse energies achieved by this system, the reduction in slope efficiency near the maximum-available pump power prompted the investigation of thermal effects in the crystal during operation. Furthermore, the local heating effects in the crystal were used to determine the impact on both phase matching and thermal lensing to understand limitations that must be overcome to achieve microjoule-level pulse energies at high repetition rates.

A HYBRID THERMAL VIDEO AND FTTR SPECTROMETER FOR RAPIDLY LOCATING AND CHARACTERIZING GAS LEAKS

EPA Science Inventory

Undiscovered gas leaks, known as fugitive emissions, in chemical plants and refinery operations can impact regional air quality as well as being a public health problem. Surveying a facility for potential gas leaks can be a daunting task. An efficient, accurate and cost-effecti...

Some Basics for Teaching and Evaluating Energy Conservation in the Home

ERIC Educational Resources Information Center

McColl, Robert W.

1978-01-01

Examines methods for determining thermal efficiency and measuring heat loss in the home. Suggests ways to conserve energy based upon (1) climatic environment and its impact on a structure, (2) physical location of buildings and their microclimate, and (3) behavior modification of the inhabitants. (Author)

Problems of Technology of Energy-Saving Buildings and Their Impact on Energy Efficiency in Buildings

NASA Astrophysics Data System (ADS)

Kwasnowski, Pawel; Fedorczak-Cisak, Malgorzata; Knap, Katarzyna

2017-10-01

Introduction of EPBD in legislation of the EU member states caused that buildings must meet very stringent requirements of thermal protection and energy efficiency. On the basis of EPBD provisions, EU Member States introduce standard of NZEB (Nearly Zero-Energy Buildings). Such activities cause a need for new, innovative materials and technologies, and new approaches to design, construction and retrofitting of buildings. Indispensable is the precise coordination of the design of structure and technical installations of building, which may be provided in an integrated design process in the system BIM. Good coordination and cooperation of all contractors during the construction phase is also necessary. The article presents the problems and the new methodology for the design, construction and use of energy efficient buildings in terms of energy saving technologies, including discussion of the significant impact of the automation of technical installations on the building energy efficiency.

Thermodynamic analysis of performance improvement by reheat on the CO2 transcritical power cycle

NASA Astrophysics Data System (ADS)

Tuo, Hanfei

2012-06-01

The CO2 transcritical rankine power cycle has been widely investigated recently, because of its better temperature glide matching between sensible heat source and working fluid in vapor generator, and its desirable qualities, such as moderate critical point, little environment impact and low cost. A reheat CO2 transcritical power cycle with two stage expansion is presented to improve baseline cycle performance in this paper. Energy and exergy analysis are carried out to investigate effects of important parameters on cycle performance. The main results show that reheat cycle performance is sensitive to the variation of medium pressures and the optimum medium pressures exist for maximizing work output and thermal efficiency, respectively. Reheat cycle is compared to baseline cycle under the same conditions. More significant improvements by reheat are obtained at lower turbine inlet temperatures and larger high cycle pressure. Work output improvement is much higher than thermal efficiency improvement, because extra waste heat is required to reheat CO2. Based on second law analysis, exergy efficiency of reheat cycle is also higher than that of baseline cycle, because more useful work is converted from waste heat. Reheat with two stage expansion has great potential to improve thermal efficiency and especially net work output of a CO2 transcritical power cycle using a low-grade heat source.

Can storage reduce electricity consumption? A general equation for the grid-wide efficiency impact of using cooling thermal energy storage for load shifting

NASA Astrophysics Data System (ADS)

Deetjen, Thomas A.; Reimers, Andrew S.; Webber, Michael E.

2018-02-01

This study estimates changes in grid-wide, energy consumption caused by load shifting via cooling thermal energy storage (CTES) in the building sector. It develops a general equation for relating generator fleet fuel consumption to building cooling demand as a function of ambient temperature, relative humidity, transmission and distribution current, and baseline power plant efficiency. The results present a graphical sensitivity analysis that can be used to estimate how shifting load from cooling demand to cooling storage could affect overall, grid-wide, energy consumption. In particular, because power plants, air conditioners and transmission systems all have higher efficiencies at cooler ambient temperatures, it is possible to identify operating conditions such that CTES increases system efficiency rather than decreasing it as is typical for conventional storage approaches. A case study of the Dallas-Fort Worth metro area in Texas, USA shows that using CTES to shift daytime cooling load to nighttime cooling storage can reduce annual, system-wide, primary fuel consumption by 17.6 MWh for each MWh of installed CTES capacity. The study concludes that, under the right circumstances, cooling thermal energy storage can reduce grid-wide energy consumption, challenging the perception of energy storage as a net energy consumer.

Multiphysics Computational Analysis of a Solid-Core Nuclear Thermal Engine Thrust Chamber

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Canabal, Francisco; Cheng, Gary; Chen, Yen-Sen

2007-01-01

The objective of this effort is to develop an efficient and accurate computational heat transfer methodology to predict thermal, fluid, and hydrogen environments for a hypothetical solid-core, nuclear thermal engine - the Small Engine. In addition, the effects of power profile and hydrogen conversion on heat transfer efficiency and thrust performance were also investigated. The computational methodology is based on an unstructured-grid, pressure-based, all speeds, chemically reacting, computational fluid dynamics platform, while formulations of conjugate heat transfer were implemented to describe the heat transfer from solid to hydrogen inside the solid-core reactor. The computational domain covers the entire thrust chamber so that the afore-mentioned heat transfer effects impact the thrust performance directly. The result shows that the computed core-exit gas temperature, specific impulse, and core pressure drop agree well with those of design data for the Small Engine. Finite-rate chemistry is very important in predicting the proper energy balance as naturally occurring hydrogen decomposition is endothermic. Locally strong hydrogen conversion associated with centralized power profile gives poor heat transfer efficiency and lower thrust performance. On the other hand, uniform hydrogen conversion associated with a more uniform radial power profile achieves higher heat transfer efficiency, and higher thrust performance.

Impact of Photovoltaic Canopy Shade on Outdoor Thermal Comfort in a Hot Desert City

NASA Astrophysics Data System (ADS)

Middel, Ariane; Selover, Nancy; Hagen, Björn; Chhetri, Nalini

2016-04-01

Shade plays an important role in designing pedestrian-friendly outdoor spaces in hot desert cities. This study investigates the impact of photovoltaic canopy shade on thermal comfort through microclimate observations and field surveys at a pedestrian mall on Arizona State University's Tempe campus. Six stationary sensors under solar canopies and in nearby sun-exposed and tree-shaded locations monitored 5-min temperature and humidity for a year. On selected clear calm days representative of each season, we conducted hourly microclimate transects from 7:00AM to 6:00PM and surveyed 1284 people about their thermal perception, comfort, and preferences. Shade lowered thermal sensation votes by approximately 1 point on the Likert scale, increasing thermal comfort in all seasons except winter. The shade type (tree or solar canopy) did not significantly impact perceived comfort, suggesting that artificial and natural shade are equally efficient in semi-arid desert environments. Globe temperature explained 50% of the variance in thermal sensation votes and was the only statistically significant meteorological predictor. Important non-meteorological factors include adaptation level, gender, thermal comfort vote, thermal preference, season, and time of day. A regression of perceived comfort on Physiological Equivalent Temperature yielded a neutral temperature of 28.6°C. The acceptable comfort range was 19.1°C-38.1°C with a preferred temperature of 20.8°C. Respondents exposed to above neutral temperatures felt more comfortable if they had been in air-conditioning 5 minutes prior to the survey, indicating a lagged response to outdoor conditions. Our study highlights the importance of active solar access management in hot urban areas.

Strategies towards an optimized use of the shallow geothermal potential

NASA Astrophysics Data System (ADS)

Schelenz, S.; Firmbach, L.; Kalbacher, T.; Goerke, U.; Kolditz, O.; Dietrich, P.; Vienken, T.

2013-12-01

Thermal use of the shallow subsurface for heat generation, cooling and thermal energy storage is increasingly gaining importance in reconsideration of future energy supplies, e.g. in the course of German energy transition, with application shifting from isolated to intensive use. The planning and dimensioning of (geo-)thermal applications is strongly influenced by the availability of exploration data. Hence, reliable site-specific dimensioning of systems for the thermal use of the shallow subsurface will contribute to an increase in resource efficiency, cost reduction during installation and operation, as well as reduction of environmental impacts and prevention of resource over-exploitation. Despite large cumulative investments that are being made for the utilization of the shallow thermal potential, thermal energy is in many cases exploited without prior on-site exploration and investigation of the local geothermal potential, due to the lack of adequate and cost-efficient exploration techniques. We will present new strategies for an optimized utilization of urban thermal potential, showcased at a currently developed residential neighborhood with high demand for shallow geothermal applications, based on a) enhanced site characterization and b) simulation of different site specific application scenarios. For enhanced site characterization, surface geophysics and vertical high resolution direct push-profiling were combined for reliable determination of aquifer structure and aquifer parameterization. Based on the site characterization, different site specific geothermal application scenarios, including different system types and system configurations, were simulated using OpenGeoSys to guarantee an environmental and economic sustainable thermal use of the shallow subsurface.

Interfacial Effects in Solid-Liquid Electrolytes for Improved Stability and Performance of Dye-Sensitized Solar Cells.

PubMed

Bella, Federico; Popovic, Jelena; Lamberti, Andrea; Tresso, Elena; Gerbaldi, Claudio; Maier, Joachim

2017-11-01

With the purpose of achieving stable dye-sensitized solar cells (DSSCs) with high efficiency, a new type of soft matter electrolyte is tested in which specific amounts of nanosized silica particles are finely dispersed in short-chained polyethylene glycol dimethylether encompassing an iodide/triiodide redox mediator. This results in a solid-liquid composite having synergistic electrical and favorable mechanical properties. The combination of interfacial effects and particle network formation promotes enhanced ion transport, which directly impacts the short-circuit photocurrent density. Thorough analysis reveals that this newly elaborated class of electrolytes is able to improve, at the same time, the thermal and long-term stability of DSSCs, as well as power conversion efficiency under standard and lower irradiation intensities. Lab-scale devices with champion efficiency exceeding 11% under attenuated sunlight (20 mW cm -2 , with a compact TiO 2 blocking layer) are obtained, along with impressively stable performance under both thermal stress and light soaking in an indoor environment (>96% performance retention after 2500 h of accelerated aging under full sun alternated with thermal ramps), matching the durability criteria applied to silicon solar cells for outdoor applications. The new findings might foster widespread practical application of DSSCs.

Cold homes, fuel poverty and energy efficiency improvements: A longitudinal focus group approach.

PubMed

Grey, Charlotte N B; Schmieder-Gaite, Tina; Jiang, Shiyu; Nascimento, Christina; Poortinga, Wouter

2017-08-01

Cold homes and fuel poverty have been identified as factors in health and social inequalities that could be alleviated through energy efficiency interventions. Research on fuel poverty and the health impacts of affordable warmth initiatives have to date primarily been conducted using quantitative and statistical methods, limiting the way how fuel poverty is understood. This study took a longitudinal focus group approach that allowed exploration of lived experiences of fuel poverty before and after an energy efficiency intervention. Focus group discussions were held with residents from three low-income communities before (n = 28) and after (n = 22) they received energy efficiency measures funded through a government-led scheme. The results show that improving the energy efficiency of homes at risk of fuel poverty has a profound impact on wellbeing and quality of life, financial stress, thermal comfort, social interactions and indoor space use. However, the process of receiving the intervention was experienced by some as stressful. There is a need for better community engagement and communication to improve the benefits delivered by fuel poverty programmes, as well as further qualitative exploration to better understand the wider impacts of fuel poverty and policy-led intervention schemes.

Cold homes, fuel poverty and energy efficiency improvements: A longitudinal focus group approach

PubMed Central

Grey, Charlotte N. B.; Schmieder-Gaite, Tina; Jiang, Shiyu; Nascimento, Christina

2017-01-01

Cold homes and fuel poverty have been identified as factors in health and social inequalities that could be alleviated through energy efficiency interventions. Research on fuel poverty and the health impacts of affordable warmth initiatives have to date primarily been conducted using quantitative and statistical methods, limiting the way how fuel poverty is understood. This study took a longitudinal focus group approach that allowed exploration of lived experiences of fuel poverty before and after an energy efficiency intervention. Focus group discussions were held with residents from three low-income communities before (n = 28) and after (n = 22) they received energy efficiency measures funded through a government-led scheme. The results show that improving the energy efficiency of homes at risk of fuel poverty has a profound impact on wellbeing and quality of life, financial stress, thermal comfort, social interactions and indoor space use. However, the process of receiving the intervention was experienced by some as stressful. There is a need for better community engagement and communication to improve the benefits delivered by fuel poverty programmes, as well as further qualitative exploration to better understand the wider impacts of fuel poverty and policy-led intervention schemes. PMID:28890663

Application of integrated fluid-thermal-structural analysis methods

NASA Technical Reports Server (NTRS)

Wieting, Allan R.; Dechaumphai, Pramote; Bey, Kim S.; Thornton, Earl A.; Morgan, Ken

1988-01-01

Hypersonic vehicles operate in a hostile aerothermal environment which has a significant impact on their aerothermostructural performance. Significant coupling occurs between the aerodynamic flow field, structural heat transfer, and structural response creating a multidisciplinary interaction. Interfacing state-of-the-art disciplinary analysis methods is not efficient, hence interdisciplinary analysis methods integrated into a single aerothermostructural analyzer are needed. The NASA Langley Research Center is developing such methods in an analyzer called LIFTS (Langley Integrated Fluid-Thermal-Structural) analyzer. The evolution and status of LIFTS is reviewed and illustrated through applications.

Metamaterial Receivers for High Efficiency Concentrated Solar Energy Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yellowhair, Julius E.; Kwon, Hoyeong; Alu, Andrea

Operation of concentrated solar power receivers at higher temperatures (>700°C) would enable supercritical carbon dioxide (sCO 2) power cycles for improved power cycle efficiencies (>50%) and cost-effective solar thermal power. Unfortunately, radiative losses at higher temperatures in conventional receivers can negatively impact the system efficiency gains. One approach to improve receiver thermal efficiency is to utilize selective coatings that enhance absorption across the visible solar spectrum while minimizing emission in the infrared to reduce radiative losses. Existing coatings, however, tend to degrade rapidly at elevated temperatures. In this report, we report on the initial designs and fabrication of spectrally selectivemore » metamaterial-based absorbers for high-temperature, high-thermal flux environments important for solarized sCO 2 power cycles. Metamaterials are structured media whose optical properties are determined by sub-wavelength structural features instead of bulk material properties, providing unique solutions by decoupling the optical absorption spectrum from thermal stability requirements. The key enabling innovative concept proposed is the use of structured surfaces with spectral responses that can be tailored to optimize the absorption and retention of solar energy for a given temperature range. In this initial study through the Academic Alliance partnership with University of Texas at Austin, we use Tungsten for its stability in expected harsh environments, compatibility with microfabrication techniques, and required optical performance. Our goal is to tailor the optical properties for high (near unity) absorptivity across the majority of the solar spectrum and over a broad range of incidence angles, and at the same time achieve negligible absorptivity in the near infrared to optimize the energy absorbed and retained. To this goal, we apply the recently developed concept of plasmonic Brewster angle to suitably designed nanostructured Tungsten surfaces. We predict that this will improve the receiver thermal efficiencies by at least 10% over current solar receivers.« less

Benefits of high aerodynamic efficiency to orbital transfer vehicles

NASA Technical Reports Server (NTRS)

Andrews, D. G.; Norris, R. B.; Paris, S. W.

1984-01-01

The benefits and costs of high aerodynamic efficiency on aeroassisted orbital transfer vehicles (AOTV) are analyzed. Results show that a high lift to drag (L/D) AOTV can achieve significant velocity savings relative to low L/D aerobraked OTV's when traveling round trip between low Earth orbits (LEO) and alternate orbits as high as geosynchronous Earth orbit (GEO). Trajectory analysis is used to show the impact of thermal protection system technology and the importance of lift loading coefficient on vehicle performance. The possible improvements in AOTV subsystem technologies are assessed and their impact on vehicle inert weight and performance noted. Finally, the performance of high L/D AOTV concepts is compared with the performances of low L/D aeroassisted and all propulsive OTV concepts to assess the benefits of aerodynamic efficiency on this class of vehicle.

Cycling excitation process: An ultra efficient and quiet signal amplification mechanism in semiconductor

NASA Astrophysics Data System (ADS)

Liu, Yu-Hsin; Yan, Lujiang; Zhang, Alex Ce; Hall, David; Niaz, Iftikhar Ahmad; Zhou, Yuchun; Sham, L. J.; Lo, Yu-Hwa

2015-08-01

Signal amplification, performed by transistor amplifiers with its merit rated by the efficiency and noise characteristics, is ubiquitous in all electronic systems. Because of transistor thermal noise, an intrinsic signal amplification mechanism, impact ionization was sought after to complement the limits of transistor amplifiers. However, due to the high operation voltage (30-200 V typically), low power efficiency, limited scalability, and, above all, rapidly increasing excess noise with amplification factor, impact ionization has been out of favor for most electronic systems except for a few applications such as avalanche photodetectors and single-photon Geiger detectors. Here, we report an internal signal amplification mechanism based on the principle of the phonon-assisted cycling excitation process (CEP). Si devices using this concept show ultrahigh gain, low operation voltage, CMOS compatibility, and, above all, quantum limit noise performance that is 30 times lower than devices using impact ionization. Established on a unique physical effect of attractive properties, CEP-based devices can potentially revolutionize the fields of semiconductor electronics.

Supercritical CO2 Power Cycles: Design Considerations for Concentrating Solar Power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neises, Ty; Turchi, Craig

2014-09-01

A comparison of three supercritical CO2 Brayton cycles: the simple cycle, recompression cycle and partial-cooling cycle indicates the partial-cooling cycle is favored for use in concentrating solar power (CSP) systems. Although it displays slightly lower cycle efficiency versus the recompression cycle, the partial-cooling cycle is estimated to have lower total recuperator size, as well as a lower maximum s-CO2 temperature in the high-temperature recuperator. Both of these effects reduce recuperator cost. Furthermore, the partial-cooling cycle provides a larger temperature differential across the turbine, which translates into a smaller, more cost-effective thermal energy storage system. The temperature drop across the turbinemore » (and by extension, across a thermal storage system) for the partial-cooling cycle is estimated to be 23% to 35% larger compared to the recompression cycle of equal recuperator conductance between 5 and 15 MW/K. This reduces the size and cost of the thermal storage system. Simulations by NREL and Abengoa Solar indicate the partial-cooling cycle results in a lower LCOE compared with the recompression cycle, despite the former's slightly lower cycle efficiency. Advantages of the recompression cycle include higher thermal efficiency and potential for a smaller precooler. The overall impact favors the use of a partial-cooling cycle for CSP compared to the more commonly analyzed recompression cycle.« less

Suppressed power saturation due to optimized optical confinement in 9xx nm high-power diode lasers that use extreme double asymmetric vertical designs

NASA Astrophysics Data System (ADS)

Kaul, T.; Erbert, G.; Maaßdorf, A.; Knigge, S.; Crump, P.

2018-03-01

Broad area lasers with novel extreme double asymmetric structure (EDAS) vertical designs featuring increased optical confinement in the quantum well, Γ, are shown to have improved temperature stability without compromising series resistance, internal efficiency or losses. Specifically, we present here vertical design considerations for the improved continuous wave (CW) performance of devices operating at 940 nm, based on systematically increasing Γ from 0.26% to 1.1%, and discuss the impact on power saturation mechanisms. The results indicate that key power saturation mechanisms at high temperatures originate in high threshold carrier densities, which arise in the quantum well at low Γ. The characteristic temperatures, T 0 and T 1, are determined under short pulse conditions and are used to clarify the thermal contribution to power limiting mechanisms. Although increased Γ reduces thermal power saturation, it is accompanied by increased optical absorption losses in the active region, which has a significant impact on the differential external quantum efficiency, {η }{{diff}}. To quantify the impact of internal optical losses contributed by the quantum well, a resonator length-dependent simulation of {η }{{diff}} is performed and compared to the experiment, which also allows the estimation of experimental values for the light absorption cross sections of electrons and holes inside the quantum well. Overall, the analysis enables vertical designs to be developed, for devices with maximized power conversion efficiency at high CW optical power and high temperatures, in a trade-off between absorption in the well and power saturation. The best balance to date is achieved in devices using EDAS designs with {{Γ }}=0.54 % , which deliver efficiencies of 50% at 14 W optical output power at an elevated junction temperature of 105 °C.

Evaluation of the variability of wind speed at different heights and its impact on the receiver efficiency of central receiver systems

NASA Astrophysics Data System (ADS)

Delgado, A.; Gertig, C.; Blesa, E.; Loza, A.; Hidalgo, C.; Ron, R.

2016-05-01

Typical plant configurations for Central Receiver Systems (CRS) are comprised of a large field of heliostats which concentrate solar irradiation onto the receiver, which is elevated hundreds of meters above the ground. Wind speed changes with altitude above ground, impacting on the receiver thermal efficiency due to variations of the convective heat losses. In addition, the physical properties of air vary at high altitudes to a significant degree, which should be considered in the thermal losses calculation. DNV GL has long-reaching experience in wind energy assessment with reliable methodologies to reduce the uncertainty of the determination of the wind regime. As a part of this study, DNV GL estimates the wind speed at high altitude for different sites using two methods, a detailed estimation applying the best practices used in the wind energy sector based on measurements from various wind sensors and a simplified estimation applying the power law (1, 2) using only one wind measurement and a representative value for the surface roughness. As a result of the study, a comparison of the wind speed estimation considering both methods is presented and the impact on the receiver performance for the evaluated case is estimated.

Electricity storage using a thermal storage scheme

NASA Astrophysics Data System (ADS)

White, Alexander

2015-01-01

The increasing use of renewable energy technologies for electricity generation, many of which have an unpredictably intermittent nature, will inevitably lead to a greater demand for large-scale electricity storage schemes. For example, the expanding fraction of electricity produced by wind turbines will require either backup or storage capacity to cover extended periods of wind lull. This paper describes a recently proposed storage scheme, referred to here as Pumped Thermal Storage (PTS), and which is based on "sensible heat" storage in large thermal reservoirs. During the charging phase, the system effectively operates as a high temperature-ratio heat pump, extracting heat from a cold reservoir and delivering heat to a hot one. In the discharge phase the processes are reversed and it operates as a heat engine. The round-trip efficiency is limited only by process irreversibilities (as opposed to Second Law limitations on the coefficient of performance and the thermal efficiency of the heat pump and heat engine respectively). PTS is currently being developed in both France and England. In both cases, the schemes operate on the Joule-Brayton (gas turbine) cycle, using argon as the working fluid. However, the French scheme proposes the use of turbomachinery for compression and expansion, whereas for that being developed in England reciprocating devices are proposed. The current paper focuses on the impact of the various process irreversibilities on the thermodynamic round-trip efficiency of the scheme. Consideration is given to compression and expansion losses and pressure losses (in pipe-work, valves and thermal reservoirs); heat transfer related irreversibility in the thermal reservoirs is discussed but not included in the analysis. Results are presented demonstrating how the various loss parameters and operating conditions influence the overall performance.

DUCT RETROFIT STRATEGY TO COMPLEMENT A MODULATING FURNACE.

DOE Office of Scientific and Technical Information (OSTI.GOV)

ANDREWS,J.W.

2002-10-02

Some recent work (Walker 2001, Andrews 2002) has indicated that installing a modulating furnace in a conventional duct system may, in many cases, result in a significant degradation in thermal distribution efficiency. The fundamental mechanism was pointed out nearly two decades ago (Andrews and Krajewski 1985). The problem occurs in duct systems that are less-than-perfectly insulated (e.g., R-4 duct wrap) and are located outside the conditioned space. It stems from the fact that when the airflow rate is reduced, as it will be when the modulating furnace reduces its heat output rate, the supply air will have a longer residencemore » time in the ducts and will therefore lose a greater percentage of its heat by conduction than it did at the higher airflow rate. The impact of duct leakage, on the other hand, is not expected to change very much under furnace modulation. The pressures in the duct system will be reduced when the airflow rate is reduced, thus reducing the leakage per unit time. This is balanced by the fact that the operating time will increase in order to meet the same heating load as with the conventional furnace operating at higher output and airflow rates. The balance would be exact if the exponent in the pressure vs. airflow equation were the same as that in the pressure vs. duct leakage equation. Since the pressure-airflow exponent is usually {approx}0.5 and the pressure-leakage exponent is usually {approx}0.6, the leakage loss as a fraction of the load should be slightly lower for the modulating furnace. The difference, however, is expected to be small, determined as it is by a function with an exponent equal to the difference between the above two exponents, or {approx}0.1. The negative impact of increased thermal conduction losses from the duct system may be partially offset by improved efficiency of the modulating furnace itself. Also, the modulating furnace will cycle on and off less often than a single-capacity model, and this may add a small amount (probably in the range 1%-3%) to the thermal distribution efficiency. Nevertheless, the effect of furnace modulation on thermal distribution efficiency, both as calculated and as measured in the laboratory, is quite significant. Although exact quantification of the impact will depend on factors such as climate and the location of the ducts within the structure, impacts in the 15%-25% range are to be expected for ducts located outside the conditioned space, as most residential duct systems are. This is too large a handicap to ignore.« less

Triphenylamine-Thienothiophene Organic Charge-Transport Molecular Materials: Effect of Substitution Pattern on their Thermal, Photoelectrochemical, and Photovoltaic Properties.

PubMed

Le, Thi Huong; Dao, Quang-Duy; Nghiêm, Mai-Phuong; Péralta, Sébastien; Guillot, Regis; Pham, Quoc Nghi; Fujii, Akihiko; Ozaki, Masanori; Goubard, Fabrice; Bui, Thanh-Tuân

2018-04-25

Two readily accessible thienothiophene-triphenylamine charge-transport materials have been synthesized by simply varying the substitution pattern of the triphenylamine groups on a central thienothiophene π-linker. The impact of the substitution pattern on the thermal, photoelectrochemical, and photovoltaic properties of these materials was evaluated and, based on theoretical and experimental studies, we found that the isomer in which the triphenylamine groups were located at the 2,5-positions of the thienothiophene core (TT-2,5-TPA) had better π-conjugation than the 3,6-isomer (TT-3,6-TPA). Whilst the thermal, morphological, and hydrophobic properties of the two materials were similar, their optoelectrochemical and photovoltaic properties were noticeably impacted. When applied as hole-transport materials in hybrid perovskite solar cells, the 2,5-isomer exhibited a power-conversion efficiency of 13.6 %, much higher than that of its 3,6-counterpart (0.7 %) under the same standard conditions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Employment of single-diode model to elucidate the variations in photovoltaic parameters under different electrical and thermal conditions

PubMed Central

Hameed, Shilan S.; Aziz, Fakhra; Sulaiman, Khaulah; Ahmad, Zubair

2017-01-01

In this research work, numerical simulations are performed to correlate the photovoltaic parameters with various internal and external factors influencing the performance of solar cells. Single-diode modeling approach is utilized for this purpose and theoretical investigations are compared with the reported experimental evidences for organic and inorganic solar cells at various electrical and thermal conditions. Electrical parameters include parasitic resistances (Rs and Rp) and ideality factor (n), while thermal parameters can be defined by the cells temperature (T). A comprehensive analysis concerning broad spectral variations in the short circuit current (Isc), open circuit voltage (Voc), fill factor (FF) and efficiency (η) is presented and discussed. It was generally concluded that there exists a good agreement between the simulated results and experimental findings. Nevertheless, the controversial consequence of temperature impact on the performance of organic solar cells necessitates the development of a complementary model which is capable of well simulating the temperature impact on these devices performance. PMID:28793325

Capacity Adequacy and Revenue Sufficiency in Electricity Markets With Wind Power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levin, Todd; Botterud, Audun

2015-05-01

We present a computationally efficient mixed-integer program (MIP) that determines optimal generator expansion decisions, as well as periodic unit commitment and dispatch. The model is applied to analyze the impact of increasing wind power capacity on the optimal generation mix and the profitability of thermal generators. In a case study, we find that increasing wind penetration reduces energy prices while the prices for operating reserves increase. Moreover, scarcity pricing for operating reserves through reserve shortfall penalties significantly impacts the prices and profitability of thermal generators. Without scarcity pricing, no thermal units are profitable, however scarcity pricing can ensure profitability formore » peaking units at high wind penetration levels. Capacity payments can also ensure profitability, but the payments required for baseload units to break even increase with the amount of wind power. The results indicate that baseload units are most likely to experience revenue sufficiency problems when wind penetration increases and new baseload units are only developed when natural gas prices are high and wind penetration is low.« less

Thermal modelling approaches to enable mitigation measures implementation for salmonid gravel stages in hydropeaking rivers

NASA Astrophysics Data System (ADS)

Casas-Mulet, R.; Alfredsen, K. T.

2016-12-01

The dewatering of salmon spawning redds can lead to early life stages mortality due to hydropeaking operations, with higher impact on the alevins stages as they have lower tolerance to dewatering than the eggs. Targeted flow-related mitigations measures can reduce such mortality, but it is essential to understand how hydropeaking change thermal regimes in rivers and may impact embryo development; only then optimal measures can be implemented at the right development stage. We present a set of experimental approaches and modelling tools for the estimation of hatch and swim-up dates based on water temperature data in the river Lundesokna (Norway). We identified critical periods for gravel-stages survival and through comparing hydropeaking vs unregulated thermal and hydrological regimes, we established potential flow-release measures to minimise mortality. Modelling outcomes were then used assess the cost-efficiency of each measure. The combinations of modelling tools used in this study were overall satisfactory and their application can be useful especially in systems where little field data is available. Targeted measures built on well-informed modelling approaches can be pre-tested based on their efficiency to mitigate dewatering effects vs. the hydropower system capacity to release or conserve water for power production. Overall, environmental flow releases targeting specific ecological objectives can provide better cost-effective options than conventional operational rules complying with general legislation.

Monitoring trends in civil engineering and their effect on indoor radon.

PubMed

Ringer, W

2014-07-01

In this paper, the importance of monitoring new building concepts is discussed. The effect of energy-efficient construction technologies on indoor radon is presented in more detail. Comparing the radon levels of about 100 low-energy and passive houses in Austria with radon levels in conventional new houses show that, in energy-efficient new houses, the radon level is about one-third lower than in conventional new houses. Nevertheless, certain features or bad practice may cause high radon levels in energy-efficient new houses. Recommendations to avoid adverse effects were set up. Furthermore, the paper deals with the effect of thermal retrofitting on indoor radon. Results from a Swiss study where 163 dwellings were measured before and after thermal retrofit yield an increase of the radon level of 26% in average. Among the various retrofit measures, replacing windows has the greatest impact on the indoor radon level. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Structures and Dynamics Division research and technology plans, FY 1982

NASA Technical Reports Server (NTRS)

Bales, K. S.

1982-01-01

Computational devices to improve efficiency for structural calculations are assessed. The potential of large arrays of microprocessors operating in parallel for finite element analysis is defined, and the impact of specialized computer hardware on static, dynamic, thermal analysis in the optimization of structural analysis and design calculations is determined. General aviation aircraft crashworthiness and occupant survivability is also considered. Mechanics technology required for design coefficient, fault tolerant advanced composite aircraft components subject to combined loads, impact, postbuckling effects and local discontinuities are developed.

Thermal radiation from large bolides and impact plumes

NASA Astrophysics Data System (ADS)

Svetsov, V.; Shuvalov, V.

2017-09-01

Numerical simulations of the impacts of asteroids and comets from 20 m to 3 km in diameter have been carried out and thermal radiation fluxes on the ground and luminous efficiencies of the impacts have been calculated. It was assumed that the cosmic objects have no strength, deform, fragment, and vaporize in the atmosphere. After the impact on the ground, formation of craters and plumes was simulated taking into account internal friction of destroyed rocks and a wake formed in the atmosphere. The equations of radiative transfer, added to the equations of gas dynamics, were used in the approximation of radiative heat diffusion or, if the Rosseland optical depth of a radiating volume of gas and vapor was less than unity, in the approximation of volume emission. Radiation fluxes on the Earth's surface were calculated by integrating the equation of radiative transfer along rays passing through a luminous area. Direct thermal radiation from fireballs and impact plumes produced by asteroids and comets larger than 50 m in diameter is dangerous for people, animals, plants, economic objects. Forest fires can be ignited on the ground within a radius of roughly 1000 times the body's diameter (for diameters of the order or smaller than 1 km), 50-m-diameter bodies can ignite forest fires within a radius of up to 40 km and 3-km asteroids - within 1700 km.

Phonon bottleneck identification in disordered nanoporous materials

NASA Astrophysics Data System (ADS)

Romano, Giuseppe; Grossman, Jeffrey C.

2017-09-01

Nanoporous materials are a promising platform for thermoelectrics in that they offer high thermal conductivity tunability while preserving good electrical properties, a crucial requirement for high-efficiency thermal energy conversion. Understanding the impact of the pore arrangement on thermal transport is pivotal to engineering realistic materials, where pore disorder is unavoidable. Although there has been considerable progress in modeling thermal size effects in nanostructures, it has remained a challenge to screen such materials over a large phase space due to the slow simulation time required for accurate results. We use density functional theory in connection with the Boltzmann transport equation to perform calculations of thermal conductivity in disordered porous materials. By leveraging graph theory and regressive analysis, we identify the set of pores representing the phonon bottleneck and obtain a descriptor for thermal transport, based on the sum of the pore-pore distances between such pores. This approach provide a simple tool to estimate phonon suppression in realistic porous materials for thermoelectric applications and enhance our understanding of heat transport in disordered materials.

Thermal lensing and microchip laser performance of N g-cut Tm3+:KY(WO4)2 crystal

NASA Astrophysics Data System (ADS)

Gaponenko, M. S.; Loiko, P. A.; Gusakova, N. V.; Yumashev, K. V.; Kuleshov, N. V.; Pavlyuk, A. A.

2012-09-01

The thermal lensing effect was characterized in the diode-pumped monoclinic N g-cut Tm:KYW crystal under laser operation conditions at the wavelength of 1.94 μm. The thermal lens was found to be slightly astigmatic; its optical power D being positive for rays lying in all meridional planes. Thermal lens sensitivity factors M= dD/ dP abs equal 11.8 m-1/W and 8.8 m-1/W (with respect to the absorbed pump power P abs) for principal meridional planes containing N p and N m axes. Nearly athermal behavior of N g-cut crystal is associated with the mutual compensation of different impacts to the thermal lens optical power that arise from temperature dependence of the refractive index dn/ dT and anisotropic thermal expansion. It was utilized to produce passively cooled diode-pumped 0.65 W cw Tm:KYW microchip laser with slope efficiency of 44 % and low thermo-optic aberrations.

New PDC cutters improve drilling efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mensa-Wilmot, G.

1997-10-27

New polycrystalline diamond compact (PDC) cutters increase penetration rates and cumulative footage through improved abrasion, impact, interface strength, thermal stability, and fatigue characteristics. Studies of formation characterization, vibration analysis, hydraulic layouts, and bit selection continue to improve and expand PDC bit applications. The paper discusses development philosophy, performance characteristics and requirements, Types A, B, and C cutters, and combinations.

Modeling of neutral entrainment in an FRC thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brackbill, Jeremiah; Gimelshein, Natalia; Gimelshein, Sergey

2012-11-27

Neutral entrainment in a field reversed configuration thruster is modeled numerically with an implicit PIC code extended to include thermal and chemical interactions between plasma and neutral particles. The contribution of charge exchange and electron impact ionization reactions is analyzed, and the sensitivity of the entrainment efficiency to the plasmoid translation velocity and neutral density is evaluated.

Fuel Cell Auxiliary Power Study Volume 1: RASER Task Order 5

NASA Technical Reports Server (NTRS)

Mak, Audie; Meier, John

2007-01-01

This study evaluated the feasibility of a hybrid solid oxide fuel cell (SOFC) auxiliary power unit (APU) and the impact in a 90-passenger More-Electric Regional Jet application. The study established realistic hybrid SOFC APU system weight and system efficiencies, and evaluated the impact on the aircraft total weight, fuel burn, and emissions from the main engine and the APU during cruise, landing and take-off (LTO) cycle, and at the gate. Although the SOFC APU may be heavier than the current conventional APU, its weight disadvantage can be offset by fuel savings in the higher SOFC APU system efficiencies against the main engine bleed and extraction during cruise. The higher SOFC APU system efficiency compared to the conventional APU on the ground can also provide considerable fuel saving and emissions reduction, particularly at the gate, but is limited by the fuel cell stack thermal fatigue characteristic.

Thermal oil recovery method using self-contained windelectric sets

NASA Astrophysics Data System (ADS)

Belsky, A. A.; Korolyov, I. A.

2018-05-01

The paper reviews challenges associated with questions of efficiency of thermal methods of impact on productive oil strata. The concept of using electrothermal complexes with WEG power supply for the indicated purposes was proposed and justified, their operating principles, main advantages and disadvantages, as well as a schematechnical solution for the implementation of the intensification of oil extraction, were considered. A mathematical model for finding the operating characteristics of WEG is presented and its main energy parameters are determined. The adequacy of the mathematical model is confirmed by laboratory simulation stand tests with nominal parameters.

Development of Metallic Thermal Protection Systems for the Reusable Launch Vehicle

NASA Technical Reports Server (NTRS)

Blosser, Max L.

1996-01-01

A reusable Thermal Protection System (TPS) that is not only lightweight, but durable, operable and cost effective is one of the technologies required by the Reusable Launch Vehicle (RLV) to achieve the goal of drastically reducing the cost of delivering payload to orbit. Metallic TPS is one of the systems being developed to meet this challenge. Current efforts involve improving the superalloy honeycomb TPS concept, which consists of a foil-gage metallic box encapsulating a low density fibrous insulation, and evaluating it for RLV requirements. The superalloy honeycomb TPS concept is mechanically attached to the vehicle structure. Improvements include more efficient internal insulation, a simpler, lighter weight configuration, and a quick-release fastener system for easier installation and removal. Evaluation includes thermal and structural analysis, fabrication and testing of both coupons and TPS panels under conditions simulating RLV environments. Coupons of metallic honeycomb sandwich, representative of the outer TPS surface, were subjected to low speed impact, hypervelocity impact, and rain erosion testing as well as subsequent arcjet exposure. Arrays of TPS panels have been subjected to radiant heating in a thermal/vacuum facility, aerodynamic heating in an arcjet facility and acoustic loading.

7 CFR 3300.13 - Determination of the efficiency of the thermal appliances as installed in the insulated body.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 15 2011-01-01 2011-01-01 false Determination of the efficiency of the thermal... Determination of the efficiency of the thermal appliances as installed in the insulated body. In determining the efficiency of a thermal appliance with respect to maintaining a prescribed temperature inside the body, the...

Büttiker probes for dissipative phonon quantum transport in semiconductor nanostructures

NASA Astrophysics Data System (ADS)

Miao, K.; Sadasivam, S.; Charles, J.; Klimeck, G.; Fisher, T. S.; Kubis, T.

2016-03-01

Theoretical prediction of phonon transport in modern semiconductor nanodevices requires atomic resolution of device features and quantum transport models covering coherent and incoherent effects. The nonequilibrium Green's function method is known to serve this purpose well but is numerically expensive in simulating incoherent scattering processes. This work extends the efficient Büttiker probe approach widely used in electron transport to phonons and considers salient implications of the method. Different scattering mechanisms such as impurity, boundary, and Umklapp scattering are included, and the method is shown to reproduce the experimental thermal conductivity of bulk Si and Ge over a wide temperature range. Temperature jumps at the lead/device interface are captured in the quasi-ballistic transport regime consistent with results from the Boltzmann transport equation. Results of this method in Si/Ge heterojunctions illustrate the impact of atomic relaxation on the thermal interface conductance and the importance of inelastic scattering to activate high-energy channels for phonon transport. The resultant phonon transport model is capable of predicting the thermal performance in the heterostructure efficiently.

Modeling magnetic field amplification in nonlinear diffusive shock acceleration

NASA Astrophysics Data System (ADS)

Vladimirov, Andrey

2009-02-01

This research was motivated by the recent observations indicating very strong magnetic fields at some supernova remnant shocks, which suggests in-situ generation of magnetic turbulence. The dissertation presents a numerical model of collisionless shocks with strong amplification of stochastic magnetic fields, self-consistently coupled to efficient shock acceleration of charged particles. Based on a Monte Carlo simulation of particle transport and acceleration in nonlinear shocks, the model describes magnetic field amplification using the state-of-the-art analytic models of instabilities in magnetized plasmas in the presence of non-thermal particle streaming. The results help one understand the complex nonlinear connections between the thermal plasma, the accelerated particles and the stochastic magnetic fields in strong collisionless shocks. Also, predictions regarding the efficiency of particle acceleration and magnetic field amplification, the impact of magnetic field amplification on the maximum energy of accelerated particles, and the compression and heating of the thermal plasma by the shocks are presented. Particle distribution functions and turbulence spectra derived with this model can be used to calculate the emission of observable nonthermal radiation.

Thermal remediation alters soil properties - a review.

PubMed

O'Brien, Peter L; DeSutter, Thomas M; Casey, Francis X M; Khan, Eakalak; Wick, Abbey F

2018-01-15

Contaminated soils pose a risk to human and ecological health, and thermal remediation is an efficient and reliable way to reduce soil contaminant concentration in a range of situations. A primary benefit of thermal treatment is the speed at which remediation can occur, allowing the return of treated soils to a desired land use as quickly as possible. However, this treatment also alters many soil properties that affect the capacity of the soil to function. While extensive research addresses contaminant reduction, the range and magnitude of effects to soil properties have not been explored. Understanding the effects of thermal remediation on soil properties is vital to successful reclamation, as drastic effects may preclude certain post-treatment land uses. This review highlights thermal remediation studies that have quantified alterations to soil properties, and it supplements that information with laboratory heating studies to further elucidate the effects of thermal treatment of soil. Notably, both heating temperature and heating time affect i) soil organic matter; ii) soil texture and mineralogy; iii) soil pH; iv) plant available nutrients and heavy metals; v) soil biological communities; and iv) the ability of the soil to sustain vegetation. Broadly, increasing either temperature or time results in greater contaminant reduction efficiency, but it also causes more severe impacts to soil characteristics. Thus, project managers must balance the need for contaminant reduction with the deterioration of soil function for each specific remediation project. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis, Processing, and Thermoelectric Properties of Germanium-Antimony-Tellurium Based Compounds and Alloys

NASA Astrophysics Data System (ADS)

Williams, Jared Brett

Society has become increasingly more aware of the negative impacts which nonrenewable energy sources have on the environment, and therefore the search for new and more efficient means of energy production has become an important research endeavor. Thermoelectric modules possess the unique ability to convert wasted heat into useful electrical energy via solid state processes, which could vastly improve the efficiency of a number of applications. The materials which accomplish this are typically comprised of semiconductors which exhibit high electrical conductivity, Seebeck coefficient, and thermal resistivity. Together these properties give us a gauge for the overall efficiency of the thermal to electrical energy conversion. Phase change materials are a class of materials primarily used for optical data storage in CDs, DVDs, and Blu-Ray discs. Today's state of the art phase change materials are based on alloys of GeTe and Sb2Te3. These materials have also been found to exhibit high thermoelectric efficiencies. These high efficiencies stem from their complex crystal structure and degenerate semiconducting nature. The purpose of this work was to study and engineer the thermoelectric properties of various alloys and compounds which belong to this family of materials. Specifically studied were the compounds Ge4SbTe5 and Ge17Sb2Te20. In each case various synthesis and processing strategies were implemented to increase the thermoelectric performance and better understand the fundamental electrical and thermal properties. Finally various proposals for future work on these materials are presented, all of which are based on the findings described herein.

Energy efficient engine, high pressure turbine thermal barrier coating. Support technology report

NASA Technical Reports Server (NTRS)

Duderstadt, E. C.; Agarwal, P.

1983-01-01

This report describes the work performed on a thermal barrier coating support technology task of the Energy Efficient Engine Component Development Program. A thermal barrier coating (TBC) system consisting of a Ni-Cr-Al-Y bond cost layer and ZrO2-Y2O3 ceramic layer was selected from eight candidate coating systems on the basis of laboratory tests. The selection was based on coating microstructure, crystallographic phase composition, tensile bond and bend test results, erosion and impact test results, furnace exposure, thermal cycle, and high velocity dynamic oxidation test results. Procedures were developed for applying the selected TBC to CF6-50, high pressure turbine blades and vanes. Coated HPT components were tested in three kinds of tests. Stage 1 blades were tested in a cascade cyclic test rig, Stage 2 blades were component high cycle fatigue tested to qualify thermal barrier coated blades for engine testing, and Stage 2 blades and Stage 1 and 2 vanes were run in factory engine tests. After completion of the 1000 cycle engine test, the TBC on the blades was in excellent condition over all of the platform and airfoil except at the leading edge above midspan on the suction side of the airfoil. The coating damage appeared to be caused by particle impingement; adjacent blades without TBC also showed evidence of particle impingement.

Cycling excitation process: An ultra efficient and quiet signal amplification mechanism in semiconductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yu-Hsin; Yan, Lujiang; Zhang, Alex Ce

2015-08-03

Signal amplification, performed by transistor amplifiers with its merit rated by the efficiency and noise characteristics, is ubiquitous in all electronic systems. Because of transistor thermal noise, an intrinsic signal amplification mechanism, impact ionization was sought after to complement the limits of transistor amplifiers. However, due to the high operation voltage (30-200 V typically), low power efficiency, limited scalability, and, above all, rapidly increasing excess noise with amplification factor, impact ionization has been out of favor for most electronic systems except for a few applications such as avalanche photodetectors and single-photon Geiger detectors. Here, we report an internal signal amplification mechanismmore » based on the principle of the phonon-assisted cycling excitation process (CEP). Si devices using this concept show ultrahigh gain, low operation voltage, CMOS compatibility, and, above all, quantum limit noise performance that is 30 times lower than devices using impact ionization. Established on a unique physical effect of attractive properties, CEP-based devices can potentially revolutionize the fields of semiconductor electronics.« less

Novel thermal efficiency-based model for determination of thermal conductivity of membrane distillation membranes

DOE PAGES

Vanneste, Johan; Bush, John A.; Hickenbottom, Kerri L.; ...

2017-11-21

Development and selection of membranes for membrane distillation (MD) could be accelerated if all performance-determining characteristics of the membrane could be obtained during MD operation without the need to recur to specialized or cumbersome porosity or thermal conductivity measurement techniques. By redefining the thermal efficiency, the Schofield method could be adapted to describe the flux without prior knowledge of membrane porosity, thickness, or thermal conductivity. A total of 17 commercially available membranes were analyzed in terms of flux and thermal efficiency to assess their suitability for application in MD. The thermal-efficiency based model described the flux with an average %RMSEmore » of 4.5%, which was in the same range as the standard deviation on the measured flux. The redefinition of the thermal efficiency also enabled MD to be used as a novel thermal conductivity measurement device for thin porous hydrophobic films that cannot be measured with the conventional laser flash diffusivity technique.« less

Novel thermal efficiency-based model for determination of thermal conductivity of membrane distillation membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanneste, Johan; Bush, John A.; Hickenbottom, Kerri L.

Development and selection of membranes for membrane distillation (MD) could be accelerated if all performance-determining characteristics of the membrane could be obtained during MD operation without the need to recur to specialized or cumbersome porosity or thermal conductivity measurement techniques. By redefining the thermal efficiency, the Schofield method could be adapted to describe the flux without prior knowledge of membrane porosity, thickness, or thermal conductivity. A total of 17 commercially available membranes were analyzed in terms of flux and thermal efficiency to assess their suitability for application in MD. The thermal-efficiency based model described the flux with an average %RMSEmore » of 4.5%, which was in the same range as the standard deviation on the measured flux. The redefinition of the thermal efficiency also enabled MD to be used as a novel thermal conductivity measurement device for thin porous hydrophobic films that cannot be measured with the conventional laser flash diffusivity technique.« less

Impacts of convection on high-temperature aquifer thermal energy storage

NASA Astrophysics Data System (ADS)

Beyer, Christof; Hintze, Meike; Bauer, Sebastian

2016-04-01

Seasonal subsurface heat storage is increasingly used in order to overcome the temporal disparities between heat production from renewable sources like solar thermal installations or from industrial surplus heat and the heat demand for building climatisation or hot water supply. In this context, high-temperature aquifer thermal energy storage (ATES) is a technology to efficiently store and retrieve large amounts of heat using groundwater wells in an aquifer to inject or withdraw hot or cold water. Depending on the local hydrogeology and temperature amplitudes during high-temperature ATES, density differences between the injected hot water and the ambient groundwater may induce significant convective flow components in the groundwater flow field. As a consequence, stored heat may accumulate at the top of the storage aquifer which reduces the heat recovery efficiency of the ATES system. Also, an accumulation of heat at the aquifer top will induce increased emissions of heat to overlying formations with potential impacts on groundwater quality outside of the storage. This work investigates the impacts of convective heat transport on the storage efficiency of a hypothetical high-temperature ATES system for seasonal heat storage as well as heat emissions to neighboring formations by numerical scenario simulations. The coupled groundwater flow and heat transport code OpenGeoSys is used to simulate a medium scale ATES system operating in a sandy aquifer of 20 m thickness with an average groundwater temperature of 10°C and confining aquicludes at top and bottom. Seasonal heat storage by a well doublet (i.e. one fully screened "hot" and "cold" well, respectively) is simulated over a period of 10 years with biannual injection / withdrawal cycles at pumping rates of 15 m³/h and for different scenarios of the temperature of the injected water (20, 35, 60 and 90 °C). Simulation results show, that for the simulated system significant convective heat transport sets in when injection temperatures exceed 35°C. Convection results in an accumulation of heat below the upper confining layer. The consequential increase of the heat plume contact area with this formation results in increased conductive heat transfer. Also, thermal gradients between the heat plume and the ambient groundwater increase with injection temperature, which increases heat conduction within the aquifer. Both effects reduce the thermal recovery of the ATES system. At the end of the 10th injection / withdrawal cycle the efficiency of thermal recovery thus reaches about 76 % for the 20°C scenario, 74% for 35°C, 71 % for 60°C and 66 % for the 90 °C scenario. Sensitivity analysis indicates that permeability in horizontal and vertical directions are controlling factors for the extent of convective heat displacement. Also, heat plume dimensions are influenced by permeability, and to a lesser extent by heat capacity and porosity of the aquifer. The planning of high-temperature ATES at a specific site hence requires a careful investigation of hydraulic and heat transport properties. Acknowledgments: This work is part of the ANGUS+ project (www.angusplus.de) and funded by the German Federal Ministry of Education and Research (BMBF) as part of the energy storage initiative "Energiespeicher".

METAShield: Hot Metallic Aeroshell Concept for RLV/SOV

NASA Technical Reports Server (NTRS)

Scotti, Stephen J.; Poteet, Carl C.; Daryabeigi, Kamran; Nowak, Robert J.; Hsu, Su-Yuen; Schmidt, Irvin H.; Ku, Shih-Huei P.

2003-01-01

An innovative fuselage design approach that combines many desirable operational features with a simple and efficient structural approach is being developed by NASA. The approach, named METAShield for MEtallic TransAtmospheric Shield, utilizes lightly loaded, hot aeroshell structures surrounding integral propellant tanks that carry the primary structural loads. The aeroshells are designed to withstand the local pressure loads, transmitting them to the tanks with minimal restraint of thermal growth. No additional thermal protection system protects the METAShield, and a fibrous or multilayer insulation blanket, located in the space between the aeroshell and the tanks, serves as both high temperature and cryogenic insulation for the tanks. The concept is described in detail, and the performance and operational features are highlighted. Initial design results and analyses of the structural, thermal, and thermal-structural performance are described. Computational results evaluating resistance to hypervelocity impact damage, as well as some supporting aerothermal wind tunnel results. are also presented. Future development needs are summarized.

Impact of vacancy ordering on thermal transport in crystalline phase-change materials.

PubMed

Siegert, K S; Lange, F R L; Sittner, E R; Volker, H; Schlockermann, C; Siegrist, T; Wuttig, M

2015-01-01

Controlling thermal transport in solids is of paramount importance for many applications. Often thermal management is crucial for a device's performance, as it affects both reliability and power consumption. A number of intricate concepts have been developed to address this challenge, such as diamond-like coatings to enhance the thermal conductivity or low symmetry complex super-structures to reduce it. Here, a different approach is pursued, where we explore the potential of solids with a high yet controllable degree of disorder. Recently, it has been demonstrated that an unconventionally high degree of structural disorder characterizes a number of crystalline phase-change materials (PCMs). This disorder strongly impacts electronic transport and even leads to disorder induced localization (Anderson localization). This raises the question how thermal transport is affected by such conditions. Here thermal transport in highly disordered crystalline Ge-Sb-Te (GST) based PCMs is investigated. Glass-like thermal properties are observed for several crystalline PCMs, which are attributed to strong scattering by disordered point defects. A systematic study of different compounds along the pseudo-binary line between GeTe and Sb2Te3 reveals that disordered vacancies act as point defects responsible for pronounced phonon scattering. Annealing causes a gradual ordering of the vacancies and leads to a more 'crystal-like' thermal conductivity. While both vibrational and electronic degrees of freedom are affected by disorder, the consequences differ for different stoichiometries. This opens up a pathway to tune electrical and thermal transport by controlling the degree of disorder. Materials with tailored transport properties may not only help to improve power efficiency and scaling in upcoming phase-change memories but are also of fundamental interest in the field of thermoelectric materials.

Impact of vacancy ordering on thermal transport in crystalline phase-change materials

NASA Astrophysics Data System (ADS)

Siegert, K. S.; Lange, F. R. L.; Sittner, E. R.; Volker, H.; Schlockermann, C.; Siegrist, T.; Wuttig, M.

2015-01-01

Controlling thermal transport in solids is of paramount importance for many applications. Often thermal management is crucial for a device's performance, as it affects both reliability and power consumption. A number of intricate concepts have been developed to address this challenge, such as diamond-like coatings to enhance the thermal conductivity or low symmetry complex super-structures to reduce it. Here, a different approach is pursued, where we explore the potential of solids with a high yet controllable degree of disorder. Recently, it has been demonstrated that an unconventionally high degree of structural disorder characterizes a number of crystalline phase-change materials (PCMs). This disorder strongly impacts electronic transport and even leads to disorder induced localization (Anderson localization). This raises the question how thermal transport is affected by such conditions. Here thermal transport in highly disordered crystalline Ge-Sb-Te (GST) based PCMs is investigated. Glass-like thermal properties are observed for several crystalline PCMs, which are attributed to strong scattering by disordered point defects. A systematic study of different compounds along the pseudo-binary line between GeTe and Sb2Te3 reveals that disordered vacancies act as point defects responsible for pronounced phonon scattering. Annealing causes a gradual ordering of the vacancies and leads to a more ‘crystal-like’ thermal conductivity. While both vibrational and electronic degrees of freedom are affected by disorder, the consequences differ for different stoichiometries. This opens up a pathway to tune electrical and thermal transport by controlling the degree of disorder. Materials with tailored transport properties may not only help to improve power efficiency and scaling in upcoming phase-change memories but are also of fundamental interest in the field of thermoelectric materials.

Analysis of the Dependence between Energy Demand Indicators in Buildings Based on Variants for Improving Energy Efficiency in a School Building

NASA Astrophysics Data System (ADS)

Skiba, Marta; Rzeszowska, Natalia

2017-09-01

One of the five far-reaching goals of the European Union is climate change and sustainable energy use. The first step in the implementation of this task is to reduce energy demand in buildings to a minimum by 2021, and in the case of public buildings by 2019. This article analyses the possibility of improving energy efficiency in public buildings, the relationship between particular indicators of the demand for usable energy (UE), final energy (FE) and primary energy (PE) in buildings and the impact of these indicators on the assessment of energy efficiency in public buildings, based on 5 variants of extensive thermal renovation of a school building. The analysis of the abovementioned variants confirms that the thermal renovation of merely the outer envelope of the building is insufficient and requires the use of additional energy sources, for example RES. Moreover, each indicator of energy demand in the building plays a key role in assessing the energy efficiency of the building. For this reason it is important to analyze each of them individually, as well as the dependencies between them.

Mathematical modeling of photovoltaic thermal PV/T system with v-groove collector

NASA Astrophysics Data System (ADS)

Zohri, M.; Fudholi, A.; Ruslan, M. H.; Sopian, K.

2017-07-01

The use of v-groove in solar collector has a higher thermal efficiency in references. Dropping the working heat of photovoltaic panel was able to raise the electrical efficiency performance. Electrical and thermal efficiency were produced by photovoltaic thermal (PV/T) system concurrently. Mathematical modeling based on steady-state thermal analysis of PV/T system with v-groove was conducted. With matrix inversion method, the energy balance equations are explained by means of the investigative method. The comparison results show that in the PV/T system with the V-groove collector is higher temperature, thermal and electrical efficiency than other collectors.

The equivalence of minimum entropy production and maximum thermal efficiency in endoreversible heat engines.

PubMed

Haseli, Y

2016-05-01

The objective of this study is to investigate the thermal efficiency and power production of typical models of endoreversible heat engines at the regime of minimum entropy generation rate. The study considers the Curzon-Ahlborn engine, the Novikov's engine, and the Carnot vapor cycle. The operational regimes at maximum thermal efficiency, maximum power output and minimum entropy production rate are compared for each of these engines. The results reveal that in an endoreversible heat engine, a reduction in entropy production corresponds to an increase in thermal efficiency. The three criteria of minimum entropy production, the maximum thermal efficiency, and the maximum power may become equivalent at the condition of fixed heat input.

Ensuring Food Security Through Enhancing Microbiological Food Safety

NASA Astrophysics Data System (ADS)

Mikš-Krajnik, Marta; Yuk, Hyun-Gyun; Kumar, Amit; Yang, Yishan; Zheng, Qianwang; Kim, Min-Jeong; Ghate, Vinayak; Yuan, Wenqian; Pang, Xinyi

2015-10-01

Food safety and food security are interrelated concepts with a profound impact on the quality of human life. Food security describes the overall availability of food at different levels from global to individual household. While, food safety focuses on handling, preparation and storage of foods in order to prevent foodborne illnesses. This review focuses on innovative thermal and non-thermal technologies in the area of food processing as the means to ensure food security through improving food safety with emphasis on the reduction and control of microbiological risks. The antimicrobial efficiency and mechanism of new technologies to extend the shelf life of food product were also discussed.

Apparatus for encapsulating a photovoltaic module

DOEpatents

Albright, Scot P.; Dugan, Larry M.

1995-10-24

The subject inventions concern various photovoltaic module designs to protect the module from horizontal and vertical impacts and degradation of solar cell efficiency caused by moisture. In one design, a plurality of panel supports that are positioned adjacent to the upper panel in a photovoltaic module absorb vertical forces exerted along an axis perpendicular to the upper panel. Other designs employ layers of glass and tempered glass, respectively, to protect the module from vertical impacts. A plurality of button-shaped channels is used around the edges of the photovoltaic module to absorb forces applied to the module along an axis parallel to the module and direct moisture away from the module that could otherwise penetrate the module and adversely affect the cells within the module. A spacer is employed between the upper and lower panels that has a coefficient of thermal expansion substantially equivalent to the coefficient of thermal expansion of at least one of the panels.

Levers for Thermoelectric Properties in Titania-Based Ceramics

NASA Astrophysics Data System (ADS)

Backhaus-Ricoult, Monika; Rustad, James R.; Vargheese, Deenamma; Dutta, Indrajit; Work, Kim

2012-06-01

While the beneficial impact of nanostructural engineering on thermoelectric performance has been demonstrated for many semiconducting materials (SiGe, skutterudites, PbTe2, etc.), no significant advantages have been reported for oxide nanomaterials. In this study, titania is used as a model material to compare the impact of grain size, doping and substitution, second-phase nanodispersion, and crystallographic defects on the electronic and thermal properties. It is shown that the lattice thermal conductivity can be most efficiently reduced by high densities of crystallographic planar defects in the Magnéli phases, while modification of grain size or introduction of second phases on length scales of 20 nm to 100 nm introduces only minor improvement. For the electronic properties, donor dopants such as niobium provide improvement of the power factor, but are not able to compete with the enhanced carrier concentration that is reached through oxygen vacancy introduction.

Efficient Solar-Thermal Energy Harvest Driven by Interfacial Plasmonic Heating-Assisted Evaporation.

PubMed

Chang, Chao; Yang, Chao; Liu, Yanming; Tao, Peng; Song, Chengyi; Shang, Wen; Wu, Jianbo; Deng, Tao

2016-09-07

The plasmonic heating effect of noble nanoparticles has recently received tremendous attention for various important applications. Herein, we report the utilization of interfacial plasmonic heating-assisted evaporation for efficient and facile solar-thermal energy harvest. An airlaid paper-supported gold nanoparticle thin film was placed at the thermal energy conversion region within a sealed chamber to convert solar energy into thermal energy. The generated thermal energy instantly vaporizes the water underneath into hot vapors that quickly diffuse to the thermal energy release region of the chamber to condense into liquids and release the collected thermal energy. The condensed water automatically flows back to the thermal energy conversion region under the capillary force from the hydrophilic copper mesh. Such an approach simultaneously realizes efficient solar-to-thermal energy conversion and rapid transportation of converted thermal energy to target application terminals. Compared to conventional external photothermal conversion design, the solar-thermal harvesting device driven by the internal plasmonic heating effect has reduced the overall thermal resistance by more than 50% and has demonstrated more than 25% improvement of solar water heating efficiency.

Analysis of the impact of modification of cold crucible design on the efficiency of the cold crucible induction furnace

NASA Astrophysics Data System (ADS)

Przylucki, R.; Golak, S.; Bulinski, P.; Smolka, J.; Palacz, M.; Siwiec, G.; Lipart, J.; Blacha, L.

2018-05-01

The article includes numerical simulation results for two induction furnace with cold crucible (IFCC). Induction furnaces differ in cold crucible design, while the inductor geometry was preserved for both variants. Numerical simulations were conducted as three dimensional one, with coupled analysis of electromagnetic, thermal and fluid dynamics fields. During the experiment, six calculation variants, differ in amount of molten titanium (three different weights of titanium for each type of cold crucible) were considered. Main parameters controlled during the calculations were: electrical efficiency of the IFCC and the meniscus shape of liquid metal.

JWST ISIM Harness Thermal Evaluation

NASA Technical Reports Server (NTRS)

Kobel, Mark; Glazer, Stuart; Tuttle, Jim; Martins, Mario; Ruppel, Sean

2008-01-01

The James Webb Space Telescope (JWST) will be a large infrared telescope with a 6.5-meter primary mirror. Launch is planned for 2013. JWST wl1 be the premier observatory of the next decade serving thousands of astronomers worldwide. The Integrated Science Instrument Module (ISIM) is the unit that will house thc four main JWST instruments. The ISIM enclosure passively cooled to 37 Kelvin and has a tightly managed thermal budget. A significant portion of the ISIM heat load is due to parasitic heat gains from the instrument harnesses. These harnesses provide a thermal path from the Instrument Electronics Control (IEC) to the ISIM. Because of the impact of this load to the ISIM thermal design, understanding the harness parasitic heat gains is critical. To this effect, a thermal test program has been conducted in order to characterize these parasitic loads and verify harness thermal models. Recent parasitic heat loads tests resulted in the addition of a dedicated multiple stage harness radiator. In order for the radiator to efficiently reject heat from the harness, effective thermal contact conductance values for multiple harnesses had to be determined. This presentation will describe the details and the results of this test program.

Recycled Thermal Energy from High Power Light Emitting Diode Light Source.

PubMed

Ji, Jae-Hoon; Jo, GaeHun; Ha, Jae-Geun; Koo, Sang-Mo; Kamiko, Masao; Hong, JunHee; Koh, Jung-Hyuk

2018-09-01

In this research, the recycled electrical energy from wasted thermal energy in high power Light Emitting Diode (LED) system will be investigated. The luminous efficiency of lights has been improved in recent years by employing the high power LED system, therefore energy efficiency was improved compared with that of typical lighting sources. To increase energy efficiency of high power LED system further, wasted thermal energy should be re-considered. Therefore, wasted thermal energy was collected and re-used them as electrical energy. The increased electrical efficiency of high power LED devices was accomplished by considering the recycled heat energy, which is wasted thermal energy from the LED. In this work, increased electrical efficiency will be considered and investigated by employing the high power LED system, which has high thermal loss during the operating time. For this research, well designed thermoelement with heat radiation system was employed to enhance the collecting thermal energy from the LED system, and then convert it as recycled electrical energy.

Thermal management and design for optical refrigeration

NASA Astrophysics Data System (ADS)

Symonds, G.; Farfan, B. G.; Ghasemkhani, M. R.; Albrecht, A. R.; Sheik-Bahae, M.; Epstein, R. I.

2016-03-01

We present our recent work in developing a robust and versatile optical refrigerator. This work focuses on minimizing parasitic energy losses through efficient design and material optimization. The cooler's thermal linkage system and housing are studied using thermal analysis software to minimize thermal gradients through the device. Due to the extreme temperature differences within the device, material selection and characterization are key to constructing an efficient device. We describe the design constraints and material selections necessary for thermally efficient and durable optical refrigeration.

Hierarchical Graphene Foam for Efficient Omnidirectional Solar-Thermal Energy Conversion.

PubMed

Ren, Huaying; Tang, Miao; Guan, Baolu; Wang, Kexin; Yang, Jiawei; Wang, Feifan; Wang, Mingzhan; Shan, Jingyuan; Chen, Zhaolong; Wei, Di; Peng, Hailin; Liu, Zhongfan

2017-10-01

Efficient solar-thermal energy conversion is essential for the harvesting and transformation of abundant solar energy, leading to the exploration and design of efficient solar-thermal materials. Carbon-based materials, especially graphene, have the advantages of broadband absorption and excellent photothermal properties, and hold promise for solar-thermal energy conversion. However, to date, graphene-based solar-thermal materials with superior omnidirectional light harvesting performances remain elusive. Herein, hierarchical graphene foam (h-G foam) with continuous porosity grown via plasma-enhanced chemical vapor deposition is reported, showing dramatic enhancement of broadband and omnidirectional absorption of sunlight, which thereby can enable a considerable elevation of temperature. Used as a heating material, the external solar-thermal energy conversion efficiency of the h-G foam impressively reaches up to ≈93.4%, and the solar-vapor conversion efficiency exceeds 90% for seawater desalination with high endurance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Active control of thermoacoustic amplification in a thermo-acousto-electric engine

NASA Astrophysics Data System (ADS)

Olivier, Come; Penelet, Guillaume; Poignand, Gaelle; Lotton, Pierrick

2014-05-01

In this paper, a new approach is proposed to control the operation of a thermoacoustic Stirling electricity generator. This control basically consists in adding an additional acoustic source to the device, connected through a feedback loop to a reference microphone, a phase-shifter, and an audio amplifier. Experiments are performed to characterize the impact of the feedback loop (and especially that of the controlled phase-shift) on the overall efficiency of the thermal to electric energy conversion performed by the engine. It is demonstrated that this external forcing of thermoacoustic self-sustained oscillations strongly impacts the performance of the engine, and that it is possible under some circumstances to improve the efficiency of the thermo-electric transduction, compared to the one reached without active control. Applicability and further directions of investigation are also discussed.

Electric Motor Thermal Management R&D. Annual Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennion, Kevin

With the push to reduce component volumes, lower costs, and reduce weight without sacrificing performance or reliability, the challenges associated with thermal management increase for power electronics and electric motors. Thermal management for electric motors will become more important as the automotive industry continues the transition to more electrically dominant vehicle propulsion systems. The transition to more electrically dominant propulsion systems leads to higher-power duty cycles for electric drive systems. Thermal constraints place significant limitations on how electric motors ultimately perform, and as thermal management improves, there will be a direct trade-off between motor performance, efficiency, cost, and the sizingmore » of electric motors to operate within the thermal constraints. The goal of this research project is to support broad industry demand for data, analysis methods, and experimental techniques to improve and better understand motor thermal management. Work in FY15 focused on two areas related to motor thermal management: passive thermal performance and active convective cooling. Passive thermal performance emphasized the thermal impact of materials and thermal interfaces among materials within an assembled motor. The research tasks supported the publication of test methods and data for thermal contact resistances and direction-dependent thermal conductivity within an electric motor. Active convective cooling focused on measuring convective heat-transfer coefficients using automatic transmission fluid (ATF). Data for average convective heat transfer coefficients for direct impingement of ATF jets was published. Also, experimental hardware for mapping local-scale and stator-scale convective heat transfer coefficients for ATF jet impingement were developed.« less

10 CFR 429.43 - Commercial heating, ventilating, air conditioning (HVAC) equipment.

Code of Federal Regulations, 2012 CFR

2012-01-01

... seasonal energy efficiency ratio (SEER in British thermal units per Watt-hour (Btu/Wh)), the heating...) Package terminal air conditioners: The energy efficiency ratio (EER in British thermal units per Watt-hour... package vertical air conditioner: The energy efficiency ratio (EER in British thermal units per Watt-hour...

10 CFR 429.43 - Commercial heating, ventilating, air conditioning (HVAC) equipment.

Code of Federal Regulations, 2013 CFR

2013-01-01

... seasonal energy efficiency ratio (SEER in British thermal units per Watt-hour (Btu/Wh)), the heating...) Package terminal air conditioners: The energy efficiency ratio (EER in British thermal units per Watt-hour... package vertical air conditioner: The energy efficiency ratio (EER in British thermal units per Watt-hour...

Systems Analysis of GPS Electrical Power System Redesign

DTIC Science & Technology

1995-12-01

Table 8 - System Efficiencies & Multipliers for Solar Direct Model (12:102; 15:864) Component Efficiency AMTEC 0.180 Receiver and Thermal Energy Storage...and low temperatures of the working fluid. Extreme high and low temperatures provide a greater efficiency , but require extensive thermal control and...direct conversion category. The Alkali Metal Thermal -to-Electric Converter ( AMTEC ) shows mass and cost savings due to efficiencies significantly higher

Climate Change Impacts on Rivers and Implications for Electricity Generation in the United States

NASA Astrophysics Data System (ADS)

Miara, A.; Vorosmarty, C. J.; Macknick, J.; Corsi, F.; Cohen, S. M.; Tidwell, V. C.; Newmark, R. L.; Prousevitch, A.

2015-12-01

The contemporary power sector in the United States is heavily reliant on water resources to provide cooling water for thermoelectric generation. Efficient thermoelectric plant operations require large volumes of water at sufficiently cool temperatures for their cooling process. The total amount of water that is withdrawn or consumed for cooling and any potential declines in efficiencies are determined by the sector's fuel mix and cooling technologies. As such, the impact of climate change, and the extent of impact, on the power sector is shaped by the choice of electricity generation technologies that will be built over the coming decades. In this study, we model potential changes in river discharge and temperature in the contiguous US under a set of climate scenarios to year 2050 using the Water Balance Model-Thermoelectric Power and Thermal Pollution Model (WBM-TP2M). Together, these models quantify, in high-resolution (3-min), river temperatures, discharge and power plant efficiency losses associated with changes in available cooling water that incorporates climate, hydrology, river network dynamics and multi-plant impacts, on both single power plant and regional scales. Results are used to assess the aptness and vulnerability of contemporary and alternative electricity generation pathways to changes in climate and water availability for cooling purposes, and the concomitant impacts on power plant operating efficiencies. We assess the potential impacts by comparing six regions (Northeast, Southeast, Midwest, Great Plains, Southwest, Northwest as in the National Climate Assessment (2014)) across the US. These experiments allow us to assess tradeoffs among electricity-water-climate to provide useful insight for decision-makers managing regional power production and aquatic environments.

Gadolinia doped hafnia (Gd2O3- HfO 2) thermal barrier coatings for gas turbine applications

NASA Astrophysics Data System (ADS)

Gullapalli, Satya Kiran

Thermal efficiency of the gas turbines is influenced by the operating temperature of the hot gas path components. The material used for the hot gas path components can only withstand temperature up to a certain limit. Thermal barrier coatings (TBC) provide the additional thermal protection for these components and help the gas turbine achieve higher firing temperatures. Traditionally available yttria stabilized zirconia (YSZ) TBCs have a limitation up to 1200 C due to their phase transformation. The present work focuses on gadolinia based hafnia (GSH) TBCs to study their potential to replace the YSZ coatings. Different compositions of gadolinia doped hafnia coatings have been deposited using electron beam physical vapor deposition (EB-PVD) technique and characterized using x-ray diffraction (XRD) and scanning electron microscope (SEM). The crystal structure analysis performed using XRD confirmed the stabilization of the high temperature cubic phase of hafnia. Cross sectional analysis confirmed the presence of columnar structure in the coatings which is a signature of the EB-PVD coatings. Mechanical properties of the coatings were investigated using nanoindentation and nano impact testing at both room temperature and high temperature. Indentation tests indicate a reduction in hardness with an increase in temperature and gadolinia content in hafnia. Impact testing reveals the fracture resistance of the coatings as a function of stabilizer content and heat treatment. Thermal measurements and impedance testing was performed on the bulk material to study the effect of gadolinia content. Thermal cycling was performed to study the spallation behavior of the as deposited and aged samples. Finite element models were developed to study the interfacial stress development in the coatings subjected to thermal cycling.

Mechanism of the Thermal Decomposition of Ethanethiol and Dimethylsulfide

NASA Astrophysics Data System (ADS)

Melhado, William Francis; Whitman, Jared Connor; Kong, Jessica; Anderson, Daniel Easton; Vasiliou, AnGayle (AJ)

2016-06-01

Combustion of organosulfur contaminants in petroleum-based fuels and biofuels produces sulfur oxides (SO_x). These pollutants are highly regulated by the EPA because they have been linked to poor respiratory health and negative environmental impacts. Therefore much effort has been made to remove sulfur compounds in petroleum-based fuels and biofuels. Currently desulfurization methods used in the fuel industry are costly and inefficient. Research of the thermal decomposition mechanisms of organosulfur species can be implemented via engineering simulations to modify existing refining technologies to design more efficient sulfur removal processes. We have used a resistively-heated SiC tubular reactor to study the thermal decomposition of ethanethiol (CH_3CH_2SH) and dimethylsulfide (CH_3SCH_3). The decomposition products are identified by two independent techniques: 118.2 nm VUV photoionization mass spectroscopy and infrared spectroscopy. The thermal cracking products for CH_3CH_2SH are CH_2CH_2, SH, and H_2S and the thermal cracking products from CH_3SCH_3 are CH_3S, CH_2S, and CH_3.

Window performance and building energy use: Some technical options for increasing energy efficiency

NASA Astrophysics Data System (ADS)

Selkowitz, Stephen

1985-11-01

Window system design and operation has a major impact on energy use in buildings as well as on occupants' thermal and visual comfort. Window performance will be a function of optical and thermal properties, window management strategies, climate and orientation, and building type and occupancy. In residences, heat loss control is a primary concern, followed by sun control in more southerly climates. In commercial buildings, the daylight provided by windows may be the major energy benefits but solar gain must be controlled so that increased cooling loads do not exceed daylighting savings. Reductions in peak electrical demand and HVAC system size may also be possible in well-designed daylighted buildings.

Potential impact of ZT = 4 thermoelectric materials on solar thermal energy conversion technologies.

PubMed

Xie, Ming; Gruen, Dieter M

2010-11-18

State-of-the-art methodologies for the conversion of solar thermal power to electricity are based on conventional electromagnetic induction techniques. If appropriate ZT = 4 thermoelectric materials were available, it is likely that conversion efficiencies of 30-40% could be achieved. The availability of all solid state electricity generation would be a long awaited development in part because of the elimination of moving parts. This paper presents a preliminary examination of the potential performance of ZT = 4 power generators in comparison with Stirling engines taking into account specific mass, volume and cost as well as system reliability. High-performance thermoelectrics appear to have distinct advantages over magnetic induction technologies.

Energy Efficient Glazing for Adaptive Solar Control Fabricated with Photothermotropic Hydrogels Containing Graphene Oxide

PubMed Central

Kim, Dowan; Lee, Eunsu; Lee, Heon Sang; Yoon, Jinhwan

2015-01-01

Glazing for adaptive solar control is the most promising for energy efficient development, because the use of this technology in buildings can be expected to significantly impact energy use and efficiency by screening sunlight that enters a building in summer. To achieve autonomous adjustable transparency, we have developed photothermotropic material system by combining photothermal materials with thermotropic hydrogels. We found that graphene oxide dispersed within a hydrogel matrix effectively converts the photo energy of sunlight into thermal energy, providing the efficient means to trigger transparency of thermotropic hydrogels. Therefore, we could develop switchable glazing of novel photothermotropic mechanism that screen strong sunlight and heat radiation in response to the sunlight intensity, as well as the temperature. Furthermore, in this study, a prototype device was manufactured with developed materials and successfully operated in outdoor testing. PMID:25561372

10 CFR 429.43 - Commercial heating, ventilating, air conditioning (HVAC) equipment.

Code of Federal Regulations, 2014 CFR

2014-01-01

... conditioners: The energy efficiency ratio (EER in British thermal units per Watt-hour (Btu/Wh)), the cooling...) Package terminal heat pumps: The energy efficiency ratio (EER in British thermal units per Watt-hour (Btu...: The energy efficiency ratio (EER in British thermal units per Watt-hour (Btu/Wh)) and the cooling...

USING TIME VARIANT VOLTAGE TO CALCULATE ENERGY CONSUMPTION AND POWER USE OF BUILDING SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makhmalbaf, Atefe; Augenbroe , Godfried

2015-12-09

Buildings are the main consumers of electricity across the world. However, in the research and studies related to building performance assessment, the focus has been on evaluating the energy efficiency of buildings whereas the instantaneous power efficiency has been overlooked as an important aspect of total energy consumption. As a result, we never developed adequate models that capture both thermal and electrical characteristics (e.g., voltage) of building systems to assess the impact of variations in the power system and emerging technologies of the smart grid on buildings energy and power performance and vice versa. This paper argues that the powermore » performance of buildings as a function of electrical parameters should be evaluated in addition to systems’ mechanical and thermal behavior. The main advantage of capturing electrical behavior of building load is to better understand instantaneous power consumption and more importantly to control it. Voltage is one of the electrical parameters that can be used to describe load. Hence, voltage dependent power models are constructed in this work and they are coupled with existing thermal energy models. Lack of models that describe electrical behavior of systems also adds to the uncertainty of energy consumption calculations carried out in building energy simulation tools such as EnergyPlus, a common building energy modeling and simulation tool. To integrate voltage-dependent power models with thermal models, the thermal cycle (operation mode) of each system was fed into the voltage-based electrical model. Energy consumption of systems used in this study were simulated using EnergyPlus. Simulated results were then compared with estimated and measured power data. The mean square error (MSE) between simulated, estimated, and measured values were calculated. Results indicate that estimated power has lower MSE when compared with measured data than simulated results. Results discussed in this paper will illustrate the significance of enhancing building energy models with electrical characteristics. This would support different studies such as those related to modernization of the power system that require micro scale building-grid interaction, evaluating building energy efficiency with power efficiency considerations, and also design and control decisions that rely on accuracy of building energy simulation results.« less

Measuring and analyzing thermal deformations of the primary reflector of the Tianma radio telescope

NASA Astrophysics Data System (ADS)

Dong, Jian; Fu, Li; Liu, Qinghui; Shen, Zhiqiang

2018-06-01

The primary reflector of the Tianma Radio Telescope (TMRT) distorts due to the varying thermal conditions, which dramatically reduces the aperture efficiency of Q-band observations. To evaluate and overcome the thermal effects, a thermal deformations measurement system has been established based on the extended Out-of-Focus holography (e-OOF). The thermal deformations can be measured in approximately 20 min with an illumination-weighted surface root mean square (RMS) accuracy of approximately 50 μm. We have measured the thermal deformations when the backup and front structure were heated by the sun respectively, and used the active surface system to correct the thermal deformations immediately to confirm the measurements. The thermal deformations when the backup structure is heated are larger than those when the front structure is heated. The values of half power beam width (HPBW) are related to the illumination-weighted surface RMS, and can be used to check the thermal deformations. When the backup structure is heated, the aperture efficiencies can remain above 90% of the maximum efficiency at 40 GHz for approximately two hours after one adjustment. While the front structure is heated, the aperture efficiencies can remain above 90% of the maximum efficiency at 40 GHz, and above 95% after one adjustment in approximately three hours.

Self-Heating Effects In Polysilicon Source Gated Transistors

PubMed Central

Sporea, R. A.; Burridge, T.; Silva, S. R. P.

2015-01-01

Source-gated transistors (SGTs) are thin-film devices which rely on a potential barrier at the source to achieve high gain, tolerance to fabrication variability, and low series voltage drop, relevant to a multitude of energy-efficient, large-area, cost effective applications. The current through the reverse-biased source barrier has a potentially high positive temperature coefficient, which may lead to undesirable thermal runaway effects and even device failure through self-heating. Using numerical simulations we show that, even in highly thermally-confined scenarios and at high current levels, self-heating is insufficient to compromise device integrity. Performance is minimally affected through a modest increase in output conductance, which may limit the maximum attainable gain. Measurements on polysilicon devices confirm the simulated results, with even smaller penalties in performance, largely due to improved heat dissipation through metal contacts. We conclude that SGTs can be reliably used for high gain, power efficient analog and digital circuits without significant performance impact due to self-heating. This further demonstrates the robustness of SGTs. PMID:26351099

Thermodynamic Performance and Cost Optimization of a Novel Hybrid Thermal-Compressed Air Energy Storage System Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Houssainy, Sammy; Janbozorgi, Mohammad; Kavehpour, Pirouz

Compressed Air Energy Storage (CAES) can potentially allow renewable energy sources to meet electricity demands as reliably as coal-fired power plants. However, conventional CAES systems rely on the combustion of natural gas, require large storage volumes, and operate at high pressures, which possess inherent problems such as high costs, strict geological locations, and the production of greenhouse gas emissions. A novel and patented hybrid thermal-compressed air energy storage (HT-CAES) design is presented which allows a portion of the available energy, from the grid or renewable sources, to operate a compressor and the remainder to be converted and stored in themore » form of heat, through joule heating in a sensible thermal storage medium. The HT-CAES design incudes a turbocharger unit that provides supplementary mass flow rate alongside the air storage. The hybrid design and the addition of a turbocharger have the beneficial effect of mitigating the shortcomings of conventional CAES systems and its derivatives by eliminating combustion emissions and reducing storage volumes, operating pressures, and costs. Storage efficiency and cost are the two key factors, which upon integration with renewable energies would allow the sources to operate as independent forms of sustainable energy. The potential of the HT-CAES design is illustrated through a thermodynamic optimization study, which outlines key variables that have a major impact on the performance and economics of the storage system. The optimization analysis quantifies the required distribution of energy between thermal and compressed air energy storage, for maximum efficiency, and for minimum cost. This study provides a roundtrip energy and exergy efficiency map of the storage system and illustrates a trade off that exists between its capital cost and performance.« less

Utilizing of inner porous structure in injection moulds for application of special cooling method

NASA Astrophysics Data System (ADS)

Seidl, M.; Bobek, J.; Šafka, J.; Habr, J.; Nováková, I.; Běhálek, L.

2016-04-01

The article is focused on impact evaluation of controlled inner structure of production tools and new cooling method on regulation of thermal processes for injection moulding technology. The mould inserts with porous structure were cooled by means of liquid CO2 which is very progressive cooling method and enables very fast and intensive heat transfer among the plastic product, the production tool and cooling medium. The inserts were created using rapid prototype technology (DLSM) and they had a bi-component structure consisting of thin compact surface layer and defined porous inner structure of open cell character where liquid CO2 was flowing through. This analyse includes the evaluation of cooling efficiency for different inner structures and different time profiles for dosing of liquid CO2 into the porous structure. The thermal processes were monitored using thermocouples and IR thermal analyse of product surface and experimental device. Intensive heat removal influenced also the final structure and the shape and dimensional accuracy of the moulded parts that were made of semi-crystalline polymer. The range of final impacts of using intensive cooling method on the plastic parts was defined by DSC and dimensional analyses.

Changes in physical-thermal properties of soil related to very shallow geothermal systems in urban areas

NASA Astrophysics Data System (ADS)

Di Sipio, Eloisa; Psyk, Mario; Popp, Thomas; Bertermann, David

2016-04-01

In the near future the population living in urban areas is expected to increase. This worldwide trend will lead to a high concentrations of infrastructures in confined areas, whose impact on land use and shallow subsurface must be well evaluated. Since shallow geothermal energy resource is becoming increasingly important as renewable energy resource, due to its huge potential in providing thermal energy for residential and tertiary buildings and in contributing to reduce greenhouse gas emission, the number of installed geothermal systems is expected to continue to rise in the near future. However, a leading question concerns the short and long-term effect of an intensive thermal use of the shallow subsurface for heat generation, cooling and thermal energy storage. From an environmental and technical point of view, changes on ground temperatures can influence the physical-thermal properties of soil and groundwater as well as their chemical and biological features. In this study the preliminary results of ITER Project are presented. This project, funded by European Union, focuses on improving heat transfer efficiency of very shallow geothermal systems, as horizontal collector systems or special forms (i.e. helix system), interesting the first 2 m of depth from ground level. Given the heterogeneity of sedimentary deposits in alluvial plain and the uncertainties related to the estimation of thermal parameters for unconsolidated material affected by thermal use, physical-thermal parameters (i.e. moisture content, bulk density, thermal conductivity...) where determined in laboratory for sand, clay and loamy sand samples. In addition, preliminary results from a field test site located within an urban area will be also shown. The main aim is to improve our knowledge of heat transfer process in the soil body in order (i) to create a reference database to compare subsequently the impact of temperature variations on the same properties and (ii) to provide reliable data for model parameterization.

Energy Operation Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Energy Operation Model (EOM) simulates the operation of the electric grid at the zonal scale, including inter-zonal transmission constraints. It generates the production cost, power generation by plant and category, fuel usage, and locational marginal price (LMP) with a flexible way to constrain the power production by environmental constraints, e.g. heat waves, drought conditions). Different from commercial software such as PROMOD IV where generator capacity and heat rate efficiency can only be adjusted on a monthly basis, EOM calculates capacity impacts and plant efficiencies based on hourly ambient conditions (air temperature and humidity) and cooling water availability for thermal plants.more » What is missing is a hydro power dispatch.« less

A general method to analyze the thermal performance of multi-cavity concentrating solar power receivers

DOE PAGES

Fleming, Austin; Folsom, Charles; Ban, Heng; ...

2015-11-13

Concentrating solar power (CSP) with thermal energy storage has potential to provide grid-scale, on-demand, dispatachable renewable energy. As higher solar receiver output temperatures are necessary for higher thermal cycle efficiency, current CSP research is focused on high outlet temperature and high efficiency receivers. Here, the objective of this study is to provide a simplified model to analyze the thermal efficiency of multi-cavity concentrating solar power receivers.

The Northeastern United States Energy-Water Nexus: Climate Change Impacts and Alternative Water Management Strategies for the Power Sector

NASA Astrophysics Data System (ADS)

Miara, A.; Macknick, J.; Vorosmarty, C. J.; Cohen, S. M.; Rosenzweig, B.

2014-12-01

The Northeastern United States (NE) relies heavily on thermoelectric power plants (90% of total capacity) to provide electricity to more than 70 million people. This region's power plants require consistent, large volumes of water at sufficiently cold temperatures to generate electricity efficiently, and withdraw approximately 10.5 trillion gallons of water annually. Previous findings indicate that assessments of future electricity pathways must account for water availability, water temperature and the changing climate, as changes in these conditions may limit operational efficiency in the future. To account for such electric system vulnerabilities, we have created a link between an electricity system capacity expansion model (ReEDS) and a hydrologic model that is coupled to a power plant simulation model (FrAMES-TP2M) that allows for a new approach to analyze electricity system development, performance, and environmental impacts. Together, these coupled tools allow us to estimate electricity development and operations in the context of a changing climate and impacts on the seasonal spatial and temporal variability of water resources, downstream thermal effluents that cause plant-to-plant interferences and harm aquatic habitat, economic costs of water conservation methods and associated carbon emissions. In this study, we test and compare a business-as-usual strategy with three alternative water management scenarios that include changes in cooling technologies and water sources utilized for the years 2014-2050. Results of these experiments can provide useful insight into the feasibility of the electricity expansion scenarios in terms of associated water use and thermal impacts, carbon emissions, the cost of generating electricity, and also highlight the importance of accounting for water resources in future power sector planning and performance assessments.

Towards explaining the health impacts of residential energy efficiency interventions - A realist review. Part 1: Pathways.

PubMed

Willand, Nicola; Ridley, Ian; Maller, Cecily

2015-05-01

This paper is Part 1 of a realist review that tries to explain the impacts of residential energy efficiency interventions (REEIs) on householder health. According to recent systematic reviews residential energy efficiency interventions may benefit health. It is argued that home energy improvement are complex interventions and that a better understanding of the latent mechanisms and contextual issues that may shape the outcome of interventions is needed for effective intervention design. This realist review synthesises the results of 28 energy efficiency improvement programmes. This first part provides a review of the explanatory factors of the three key pathways, namely warmth in the home, affordability of fuel and psycho-social factors, and the pitfall of inadequate indoor air quality. The review revealed that REEIs improved winter warmth and lowered relative humidity with benefits for cardiovascular and respiratory health. In addition, residential energy efficiency improvements consolidated the meaning of the home as a safe haven, strengthened the householder's perceived autonomy and enhanced social status. Although satisfaction with the home proved to be an important explanation for positive mental health outcomes, financial considerations seemed to have played a secondary role. Evidence for negative impacts was rare but the risk should not be dismissed. Comprehensive refurbishments were not necessarily more effective than thermal retrofits or upgrades. A common protocol for the quantitative and qualitative evaluation of interventions would facilitate the synthesis of future studies. Householder and contextual influences are addressed in Part 2. Copyright © 2015 Elsevier Ltd. All rights reserved.

Towards co-packaging of photonics and microelectronics in existing manufacturing facilities

NASA Astrophysics Data System (ADS)

Janta-Polczynski, Alexander; Cyr, Elaine; Bougie, Jerome; Drouin, Alain; Langlois, Richard; Childers, Darrell; Takenobu, Shotaro; Taira, Yoichi; Lichoulas, Ted W.; Kamlapurkar, Swetha; Engelmann, Sebastian; Fortier, Paul; Boyer, Nicolas; Barwicz, Tymon

2018-02-01

The impact of integrated photonics on optical interconnects is currently muted by challenges in photonic packaging and in the dense integration of photonic modules with microelectronic components on printed circuit boards. Single mode optics requires tight alignment tolerance for optical coupling and maintaining this alignment in a cost-efficient package can be challenging during thermal excursions arising from downstream microelectronic assembly processes. In addition, the form factor of typical fiber connectors is incompatible with the dense module integration expected on printed circuit boards. We have implemented novel approaches to interfacing photonic chips to standard optical fibers. These leverage standard high throughput microelectronic assembly tooling and self-alignment techniques resulting in photonic packaging that is scalable in manufacturing volume and in the number of optical IOs per chip. In addition, using dense optical fiber connectors with space-efficient latching of fiber patch cables results in compact module size and efficient board integration, bringing the optics closer to the logic chip to alleviate bandwidth bottlenecks. This packaging direction is also well suited for embedding optics in multi-chip modules, including both photonic and microelectronic chips. We discuss the challenges and rewards in this type of configuration such as thermal management and signal integrity.

7 CFR 3300.13 - Determination of the efficiency of the thermal appliances as installed in the insulated body.

Code of Federal Regulations, 2010 CFR

2010-01-01

... appliances as installed in the insulated body. 3300.13 Section 3300.13 Agriculture Regulations of the... Determination of the efficiency of the thermal appliances as installed in the insulated body. In determining the efficiency of a thermal appliance with respect to maintaining a prescribed temperature inside the body, the...

Product Chemistry and Process Efficiency of Biomass Torrefaction, Pyrolysis and Gasification Studied by High-Throughput Techniques and Multivariate Analysis

NASA Astrophysics Data System (ADS)

Xiao, Li

Despite the great passion and endless efforts on development of renewable energy from biomass, the commercialization and scale up of biofuel production is still under pressure and facing challenges. New ideas and facilities are being tested around the world targeting at reducing cost and improving product value. Cutting edge technologies involving analytical chemistry, statistics analysis, industrial engineering, computer simulation, and mathematics modeling, etc. keep integrating modern elements into this classic research. One of those challenges of commercializing biofuel production is the complexity from chemical composition of biomass feedstock and the products. Because of this, feedstock selection and process optimization cannot be conducted efficiently. This dissertation attempts to further evaluate biomass thermal decomposition process using both traditional methods and advanced technique (Pyrolysis Molecular Beam Mass Spectrometry). Focus has been made on data base generation of thermal decomposition products from biomass at different temperatures, finding out the relationship between traditional methods and advanced techniques, evaluating process efficiency and optimizing reaction conditions, comparison of typically utilized biomass feedstock and new search on innovative species for economical viable feedstock preparation concepts, etc. Lab scale quartz tube reactors and 80il stainless steel sample cups coupled with auto-sampling system were utilized to simulate the complicated reactions happened in real fluidized or entrained flow reactors. Two main high throughput analytical techniques used are Near Infrared Spectroscopy (NIR) and Pyrolysis Molecular Beam Mass Spectrometry (Py-MBMS). Mass balance, carbon balance, and product distribution are presented in detail. Variations of thermal decomposition temperature range from 200°C to 950°C. Feedstocks used in the study involve typical hardwood and softwood (red oak, white oak, yellow poplar, loblolly pine), fast growing energy crops (switchgrass), and popular forage crop (alfalfa), as well as biochar derived from those materials and their mixtures. It demonstrated that Py-MBMS coupled with MVA could be used as fast analytical tools for the study of not only biomass composition but also its thermal decomposition behaviors. It found that the impact of biomass composition heavily depends on the thermal decomposition temperature because at different temperature, the composition of biomass decomposed and the impact of minerals on the decomposition reaction varies. At low temperature (200-500°C), organic compounds attribute to the majority of variation in thermal decomposition products. At higher temperature, inorganics dramatically changed the pyrolysis pathway of carbohydrates and possibly lignin. In gasification, gasification tar formation is also observed to be impacted by ash content in vapor and char. In real reactor, biochar structure also has interactions with other fractions to make the final pyrolysis and gasification product. Based on the evaluation of process efficiencies during torrefaction, temperature ranging from 275°C to 300°C with short residence time (<10min) are proposed to be optimal torrefaction conditions. 500°C is preferred to 700°C as primary pyrolysis temperature in two stage gasification because higher primary pyrolysis temperature resulted in more tar and less gasification char. Also, in terms of carbon yield, more carbon is lost in tar while less carbon is retained in gas product using 700°C as primary pyrolysis temperature. In addition, pyrolysis char is found to produce less tar and more gas during steam gasification compared with gasification of pyrolysis vapor. Thus it is suggested that torrefaction might be an efficient pretreatment for biomass gasification because it can largely improve the yield of pyrolysis char during the primary pyrolysis step of gasification thus reduce the total tar of the overall gasification products. Future work is suggested in the end.

Energy-Efficient Management of Mechanical Ventilation and Relative Humidity in Hot-Humid Climates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Withers, Jr., Charles R.

2016-12-01

In hot and humid climates, it is challenging to energy-efficiently maintain indoor RH at acceptable levels while simultaneously providing required ventilation, particularly in high performance low cooling load homes. The fundamental problem with solely relying on fixed capacity central cooling systems to manage moisture during low sensible load periods is that they are oversized for cooler periods of the year despite being 'properly sized' for a very hot design cooling day. The primary goals of this project were to determine the impact of supplementing a central space conditioning system with 1) a supplemental dehumidifier and 2) a ductless mini-split onmore » seasonal energy use and summer peak power use as well as the impact on thermal distribution and humidity control inside a completely furnished lab home that was continuously ventilated in accordance with ASHRAE 62.2-2013.« less

Building America Case Study: Energy Efficient Management of Mechanical Ventilation and Relative Humidity in Hot-Humid Climates, Cocoa, Florida

DOE Office of Scientific and Technical Information (OSTI.GOV)

2017-01-01

In hot and humid climates, it is challenging to energy-efficiently maintain indoor RH at acceptable levels while simultaneously providing required ventilation, particularly in high performance low cooling load homes. The fundamental problem with solely relying on fixed capacity central cooling systems to manage moisture during low sensible load periods is that they are oversized for cooler periods of the year despite being 'properly sized' for a very hot design cooling day. The primary goals of this project were to determine the impact of supplementing a central space conditioning system with 1) a supplemental dehumidifier and 2) a ductless mini-split onmore » seasonal energy use and summer peak power use as well as the impact on thermal distribution and humidity control inside a completely furnished lab home that was continuously ventilated in accordance with ASHRAE 62.2-2013.« less

MPT_DOE Final Report 12-15-16 rev1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bunce, Michael

The goal of this project was to achieve breakthrough thermal efficiency on a light duty passenger car engine, with minimal impact to emissions. The enabling technology or technologies were to be relatively low cost and integrateable into existing production processes. Through the use of Turbulent Jet Ignition (TJI), an enabling technology for ultra-lean engine operation, the project team was able to meet or exceed all technical goals of this program.

Quantum engine efficiency bound beyond the second law of thermodynamics.

PubMed

Niedenzu, Wolfgang; Mukherjee, Victor; Ghosh, Arnab; Kofman, Abraham G; Kurizki, Gershon

2018-01-11

According to the second law, the efficiency of cyclic heat engines is limited by the Carnot bound that is attained by engines that operate between two thermal baths under the reversibility condition whereby the total entropy does not increase. Quantum engines operating between a thermal and a squeezed-thermal bath have been shown to surpass this bound. Yet, their maximum efficiency cannot be determined by the reversibility condition, which may yield an unachievable efficiency bound above unity. Here we identify the fraction of the exchanged energy between a quantum system and a bath that necessarily causes an entropy change and derive an inequality for this change. This inequality reveals an efficiency bound for quantum engines energised by a non-thermal bath. This bound does not imply reversibility, unless the two baths are thermal. It cannot be solely deduced from the laws of thermodynamics.

Harvesting waste thermal energy using a carbon-nanotube-based thermo-electrochemical cell.

PubMed

Hu, Renchong; Cola, Baratunde A; Haram, Nanda; Barisci, Joseph N; Lee, Sergey; Stoughton, Stephanie; Wallace, Gordon; Too, Chee; Thomas, Michael; Gestos, Adrian; Cruz, Marilou E Dela; Ferraris, John P; Zakhidov, Anvar A; Baughman, Ray H

2010-03-10

Low efficiencies and costly electrode materials have limited harvesting of thermal energy as electrical energy using thermo-electrochemical cells (or "thermocells"). We demonstrate thermocells, in practical configurations (from coin cells to cells that can be wrapped around exhaust pipes), that harvest low-grade thermal energy using relatively inexpensive carbon multiwalled nanotube (MWNT) electrodes. These electrodes provide high electrochemically accessible surface areas and fast redox-mediated electron transfer, which significantly enhances thermocell current generation capacity and overall efficiency. Thermocell efficiency is further improved by directly synthesizing MWNTs as vertical forests that reduce electrical and thermal resistance at electrode/substrate junctions. The efficiency of thermocells with MWNT electrodes is shown to be as high as 1.4% of Carnot efficiency, which is 3-fold higher than for previously demonstrated thermocells. With the cost of MWNTs decreasing, MWNT-based thermocells may become commercially viable for harvesting low-grade thermal energy.

Study of weather and thermal comfort influence on sport performance: prognostic analysis applied to Rio de Janeiro's city marathon

NASA Astrophysics Data System (ADS)

Pallotta, M.; Herdies, D. L.; Gonçalves, L. G.

2013-05-01

There is nowadays a growing interest in the influence and impacts of weather and climate in human life. The weather conditions analysis shows the utility of this type of tool when applied in sports. These conditions act as a differential in strategy and training, especially for outdoor sports. This study had as aim objective develop weather forecast and thermal comfort evaluation targeted to sports, and hoped that the results can be used to the development of products and weather service in the Olympic Games 2016 in Rio de Janeiro City. The use of weather forecast applied to the sport showed to be efficient for the case of Rio de Janeiro City Marathon, especially due to the high spatial resolution. The WRF simulations for the three marathons studied showed good results for temperature, atmospheric pressure, and relative humidity. On the other hand, the forecast of the wind showed a pattern of overestimation of the real situation in all cases. It was concluded that the WRF model provides, in general, more representative simulations from 36 hours in advance, and with 18 hours of integration they were even better, describing efficiently the synoptic situation that would be found. A review of weather conditions and thermal comfort at specific points of the marathon route showed that there are significant differences between the stages of the marathon, which makes possible to plan the competition strategy under the thermal comfort. It was concluded that a relationship between a situation more thermally comfortable (uncomfortable) and the best (worst) time in Rio de Janeiro City Marathon

Effect of intrinsic surface roughness on the efficiency of intermodal phase matching in silica optical nanofibers.

PubMed

Khudus, Muhammad I M Abdul; Lee, Timothy; Horak, Peter; Brambilla, Gilberto

2015-04-01

We investigate the effect of intrinsic surface roughness associated to frozen thermal oscillations from the fiber fabrication process on the efficiency of third-harmonic generation via intermodal phase matching in silica nanofibers. Already a periodic wave with roughness of 0.2 nm reduces the efficiency by roughly 50% in a 1-mm optical nanofiber, with the divergence growing quadratically with distance. The surface wave period does not exhibit a large impact on the efficiency, due to averaging effects. However, both the location of the surface waves with respect to the phase matching radius as well as the surface wave amplitude have substantial effect on the efficiency, with the former presenting the possibility of transferring the power back to the pump wavelength. Simulations with a realistic superposition of random surface waves indicate that the conversion efficiency increases only for a few mm of propagation and reaches a maximum of less than 1%.

Effect of Thermal Storage on the Performance of a Wood Pellet-fired Residential Boiler

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Butcher

Interest in the direct use of biomass for thermal applications as a renewable technology is increasing as is also focus on air pollutant emissions from these sources and methods to minimize the impact. This work has focused on wood pellet-fired residential boilers, which are the cleanest fuel in this category. In the residential application the load varies strongly over the course of a year and a high fraction of the load is typically under 15% of the maximum boiler capacity. Thermal storage can be used even with boilers which have modulation capacity typically to 30% of the boiler maximum. Onemore » common pellet boiler was tested at full load and also at the minimum load used in the U.S. certification testing (15%). In these tests the load was steady over the test period. Testing was also done with an emulated load profile for a home in Albany, N.Y. on a typical January, March, and April day. In this case the load imposed on the boiler varied hourly under computer control, based on the modeled load for the example case used. The boiler used has a nominal output of 25 kW and a common mixed hardwood/softwood commercial pellet was used. Moisture content was 3.77%. A dilution tunnel approach was used for the measurement of particulate emissions, in accordance with U.S. certification testing requirements. The test results showed that the use of storage strongly reduces cycling rates under part load conditions. The transients which occur as these boilers cycle contribute to increased particulate emissions and reduced efficiency. The time period of a full cycle at a given load condition can be increased by increasing the storage tank volume and/or increasing the control differential range. It was shown that increasing the period strongly increased the measured efficiency and reduced the particulate emission (relative to the no storage case). The impact was most significant at the low load levels. Storage tank heat loss is shown to be a significant factor in thermal efficiency, particularly at low load. Different methods to measure this heat loss were explored. For one of the tanks evaluated the efficiency loss at the 15% load point was found to be as high as 7.9%. Where storage is used good insulation on the tank, insulation on the piping, and attention to fittings are recommended.« less

From photoluminescence to thermal emission: Thermally-enhanced PL (TEPL) for efficient PV (Conference Presentation)

NASA Astrophysics Data System (ADS)

Manor, Assaf; Kruger, Nimrod; Martin, Leopoldo L.; Rotschild, Carmel

2016-09-01

The Shockley-Queisser efficiency limit of 40% for single-junction photovoltaic (PV) cells is mainly caused by the heat dissipation accompanying the process of electro-chemical potential generation. Concepts such as solar thermo-photovoltaics (STPV) aim to harvest this heat loss by the use of a primary absorber which acts as a mediator between the sun and the PV, spectrally shaping the light impinging on the cell. However, this approach is challenging to realize due to the high operating temperatures of above 2000K required in order to generate high thermal emission fluxes. After over thirty years of STPV research, the record conversion efficiency for STPV device stands at 3.2% for 1285K operating temperature. In contrast, we recently demonstrated how thermally-enhanced photoluminescence (TEPL) is an optical heat-pump, in which photoluminescence is thermally blue-shifted upon heating while the number of emitted photons is conserved. This process generates energetic photon-rates which are comparable to thermal emission in significantly reduced temperatures, opening the way for a TEPL based energy converter. In such a device, a photoluminescent low bandgap absorber replaces the STPV thermal absorber. The thermalization heat induces a temperature rise and a blue-shifted emission, which is efficiently harvested by a higher bandgap PV. We show that such an approach can yield ideal efficiencies of 70% at 1140K, and realistic efficiencies of almost 50% at moderate concentration levels. As an experimental proof-of-concept, we demonstrate 1.4% efficient TEPL energy conversion of an Nd3+ system coupled to a GaAs cell, at 600K.

Energy Efficiency of Low-Temperature Deaeration of Makeup Water for a District Heating System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharapov, V. I., E-mail: vlad-sharapov2008@yandex.ru; Kudryavtseva, E. V.

2016-07-15

It is shown that the temperature of makeup water in district heating systems has a strong effect on the energy efficiency of turbines of thermal power plants. A low-temperature deaeration process that considerably improves the energy efficiency of thermal power plants is developed. The desorbing agent is the gas supplied to the burners of the boiler. The energy efficiency of the process for a typical unit of thermal power plant is assessed.

Effect of powder compaction on radiation-thermal synthesis of lithium-titanium ferrites

NASA Astrophysics Data System (ADS)

Surzhikov, A. P.; Lysenko, E. N.; Vlasov, V. A.; Malyshev, A. V.; Korobeynikov, M. V.; Mikhailenko, M. A.

2017-01-01

Effect of powder compaction on the efficiency of thermal and radiation-thermal synthesis of lithium-substituted ferrites was investigated by X-Ray diffraction and specific magnetization analysis. It was shown that the radiation-thermal heating of compacted powder reagents mixture leads to an increase in efficiency of lithium-titanium ferrites synthesis.

Riverine ecosystem services and the thermoelectric sector: strategic issues facing the Northeastern United States

NASA Astrophysics Data System (ADS)

Miara, A.; Vorosmarty, C. J.; Stewart, R.; Wollheim, W. M.; Rosenzweig, B.

2013-12-01

Major strategic issues facing the global thermoelectric sector include environmental regulation, climate change and increasing electricity demand. We have addressed such issues by modeling thermoelectric generation in the Northeastern United States that is reliant on cooling under five sensitivity tests to evaluate losses/gains in power production, thermal pollution and suitable aquatic habitat, comparing the contemporary baseline (2000-2010) with potential future states. Integral to the analysis, we developed a methodology to quantify river water availability for cooling, which we define as an ecosystem service. Projected climate conditions reduce river water available for efficient power plant operations and the river's capacity to absorb waste heat, causing a loss of regional thermoelectric generation (RTG) (2.5%) in some summers that, compared to the contemporary baseline, is equal to the summertime electricity consumption of 1.3 million Northeastern US homes. Vulnerabilities to warm temperatures and thermal pollution can be alleviated through the use of more efficient natural gas (NG) power plants that have a reduced reliance on cooling water. Conversion of once-through (OT) to cooling tower (CT) systems and the Clean Water Act (CWA) temperature limit regulation, both of which reduce efficiencies at the single plant level, show potential to yield beneficial increases in RTG. This is achieved by obviating the need for large volumes of river water, thereby reducing plant-to-plant interferences through lowering the impact of upstream thermal pollution and preserving a minimum standard of cooling water. The results and methodology framework presented here, which can be extrapolated to other regional assessments with contrasting climates and thermoelectric profiles, can identify opportunities and support decision-making to achieve more efficient energy systems and riverine ecosystem protection.

Riverine ecosystem services and the thermoelectric sector: strategic issues facing the Northeastern United States

NASA Astrophysics Data System (ADS)

Miara, Ariel; Vörösmarty, Charles J.; Stewart, Robert J.; Wollheim, Wilfred M.; Rosenzweig, Bernice

2013-06-01

Major strategic issues facing the global thermoelectric sector include environmental regulation, climate change and increasing electricity demand. We have addressed such issues by modeling thermoelectric generation in the Northeastern United States that is reliant on cooling under five sensitivity tests to evaluate losses/gains in power production, thermal pollution and suitable aquatic habitat, comparing the contemporary baseline (2000-2010) with potential future states. Integral to the analysis, we developed a methodology to quantify river water availability for cooling, which we define as an ecosystem service. Projected climate conditions reduce river water available for efficient power plant operations and the river’s capacity to absorb waste heat, causing a loss of regional thermoelectric generation (RTG) (2.5%) in some summers that, compared to the contemporary baseline, is equal to the summertime electricity consumption of 1.3 million Northeastern US homes. Vulnerabilities to warm temperatures and thermal pollution can be alleviated through the use of more efficient natural gas (NG) power plants that have a reduced reliance on cooling water. Conversion of once-through (OT) to cooling tower (CT) systems and the Clean Water Act (CWA) temperature limit regulation, both of which reduce efficiencies at the single plant level, show potential to yield beneficial increases in RTG. This is achieved by obviating the need for large volumes of river water, thereby reducing plant-to-plant interferences through lowering the impact of upstream thermal pollution and preserving a minimum standard of cooling water. The results and methodology framework presented here, which can be extrapolated to other regional assessments with contrasting climates and thermoelectric profiles, can identify opportunities and support decision-making to achieve more efficient energy systems and riverine ecosystem protection.

Nickel-Graphite Composite Compliant Interface and/or Hot Shoe Material

NASA Technical Reports Server (NTRS)

Firdosy, Samad A.; Chun-Yip Li, Billy; Ravi, Vilupanur A.; Fleurial, Jean-Pierre; Caillat, Thierry; Anjunyan, Harut

2013-01-01

Next-generation high-temperature thermoelectric-power-generating devices will employ segmented architectures and will have to reliably withstand thermally induced mechanical stresses produced during component fabrication, device assembly, and operation. Thermoelectric materials have typically poor mechanical strength, exhibit brittle behavior, and possess a wide range of coefficient of thermal expansion (CTE) values. As a result, the direct bonding at elevated temperatures of these materials to each other to produce segmented leg components is difficult, and often results in localized microcracking at interfaces and mec hanical failure due to the stresses that arise from the CTE mismatch between the various materials. Even in the absence of full mechanical failure, degraded interfaces can lead to increased electrical and thermal resistances, which adversely impact conversion efficiency and power output. The proposed solution is the insertion of a mechanically compliant layer, with high electrical and thermal conductivity, between the low- and high-temperature segments to relieve thermomechanical stresses during device fabrication and operation. This composite material can be used as a stress-relieving layer between the thermoelectric segments and/or between a thermoelectric segment and a hot- or cold-side interconnect material. The material also can be used as a compliant hot shoe. Nickel-coated graphite powders were hot-pressed to form a nickel-graphite composite material. A freestanding thermoelectric segmented leg was fabricated by brazing the compliant pad layer between the high-temperature p- Zintl and low-temperature p-SKD TE segments using Cu-Ag braze foils. The segmented leg stack was heated in vacuum under a compressive load to achieve bonding. The novelty of the innovation is the use of composite material that re duces the thermomechanical stresses en - countered in the construction of high-efficiency, high-temperature therm - o-electric devices. The compliant pad enables the bonding of dissimilar thermoelectric materials while maintaining the desired electrical and thermal properties essential for efficient device operation. The modulus, CTE, electrical, and thermal conductances of the composite can be controlled by varying the ratio of nickel to graphite.

Imaging Spatial Variations in the Dissipation and Transport of Thermal Energy within Individual Silicon Nanowires Using Ultrafast Microscopy.

PubMed

Cating, Emma E M; Pinion, Christopher W; Van Goethem, Erika M; Gabriel, Michelle M; Cahoon, James F; Papanikolas, John M

2016-01-13

Thermal management is an important consideration for most nanoelectronic devices, and an understanding of the thermal conductivity of individual device components is critical for the design of thermally efficient systems. However, it can be difficult to directly probe local changes in thermal conductivity within a nanoscale system. Here, we utilize the time-resolved and diffraction-limited imaging capabilities of ultrafast pump-probe microscopy to determine, in a contact-free configuration, the local thermal conductivity in individual Si nanowires (NWs). By suspending single NWs across microfabricated trenches in a quartz substrate, the properties of the same NW both on and off the substrate are directly compared. We find the substrate has no effect on the recombination lifetime or diffusion length of photogenerated charge carriers; however, it significantly impacts the thermal relaxation properties of the NW. In substrate-supported regions, thermal energy deposited into the lattice by the ultrafast laser pulse dissipates within ∼10 ns through thermal diffusion and coupling to the substrate. In suspended regions, the thermal energy persists for over 100 ns, and we directly image the time-resolved spatial motion of the thermal signal. Quantitative analysis of the transient images permits direct determination of the NW's local thermal conductivity, which we find to be a factor of ∼4 smaller than in bulk Si. Our results point to the strong potential of pump-probe microscopy to be used as an all-optical method to quantify the effects of localized environment and morphology on the thermal transport characteristics of individual nanostructured components.

FY2016 Propulsion Materials Annual Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

None, None

The Propulsion Materials Program actively supports the energy security and reduction of greenhouse emissions goals of VTO by investigating and identifying the materials properties that are most essential for continued development of cost-effective, highly efficient, and environmentally friendly next-generation heavy and light-duty powertrains. The technical approaches available to enhance propulsion systems focus on improvements in both vehicle efficiency and fuel substitution, both of which must overcome the performance limitations of the materials currently in use. Propulsion Materials Program activities work with national laboratories, industry experts, and VTO powertrain systems (e.g., Advanced Combustion Engines and Fuels) teams to develop strategies thatmore » overcome materials limitations in future powertrain performance. The technical maturity of the portfolio of funded projects ranges from basic science to subsystem prototype validation. Projects within a Propulsion Materials Program activity address materials concerns that directly impact critical technology barriers within each of the above programs, including barriers that impact fuel efficiency, thermal management, emissions reduction, improved reliability, and reduced manufacturing costs. The program engages only the barriers that result from material property limitations and represent fundamental, high-risk materials issues.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davlin, Thomas

The overall deliverable from the project is the design, construction and commissioning of a detention facility heating and cooling system that minimizes ownership costs and maximizes efficiency (and therefore minimizes environmental impact). The primary deliverables were the proof of concept for the application of geothermal systems for an institutional facility and the ongoing, quarterly system operating data downloads to the Department of Energy . The primary advantage of geothermal based heat pump systems is the higher efficiency of the system compared to a conventional chiller, boiler, cooling tower based system. The higher efficiency results in a smaller environmental foot printmore » and lower energy costs for the detention facility owner, Lancaster County. The higher efficiency for building cooling is primarily due to a more constant compressor condensing temperature with the geothermal well field acting as a thermal “sink” (in place of the conventional system’s cooling tower). In the heating mode, Ground Couple Heat Pump (GCHP) systems benefits from the advantage of a heat pump Coefficient of Performance (COP) of approximately 3.6, significantly better than a conventional gas boiler. The geothermal well field acting as a thermal “source” allows the heat pumps to operate efficiently in the heating mode regardless of ambient temperatures. The well field is partially located in a wetland with a high water table so, over time, the project will be able to identify the thermal loading characteristics of a well field located in a high water table location. The project demonstrated how a large geothermal well field can be installed in a wetland area in an economical and environmentally sound manner. Finally, the SW 40th Street Thermal Energy Plant project demonstrates the benefits of providing domestic hot water energy, as well as space heating, to help balance well filed thermal loading in a cooling dominated application. During the period of August 2012 thru March 2014, with the detention facility occupied for the final seven months, the well field supply water temperatures to the heat pumps dropped to a minimum of 39°F and reached a maximum temperature of 68 °F while providing 15,819 MMBtu of cooling energy and 27,467 MMBtu of heating energy. During this period the peak recorded system cooling load was 610 tons and the peak heating load was 8.4 MMBtu. The DEC is currently evaluating the most beneficial electric rate for plant operations. Total project cost of $16.9 million was approximately $3.2 million less than the estimate provided in the grant application. The reduction in project costs were primarily due to favorable construction material prices as well as strong competition in the local construction contractor market. The DEC plant reached the substantial completion milestone in December 2011 and began providing thermal service to the detention facility in January 2012 when the building’s HVAC system was ready to accept heating service. The plant reached commercial operating status on August 1, 2012. However, due to construction delays, the detention facility was not occupied until September of 2013. The detention facility construction delays also impacted the installation and commissioning of the project’s dedicated domestic hot water heat pump. Final coordination with the detention facility’s building management system vendor to establish network links for the exchange of date is currently being completed. This will allow the development of control sequences for the optimal operation of the domestic hot water system.« less

Use of a Geothermal-Solar Hybrid Power Plant to Mitigate Declines in Geothermal Resource Productivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dan Wendt; Greg Mines

2014-09-01

Many, if not all, geothermal resources are subject to decreasing productivity manifested in the form of decreasing brine temperature, flow rate, or both during the life span of the associated power generation project. The impacts of resource productivity decline on power plant performance can be significant; a reduction in heat input to a power plant not only decreases the thermal energy available for conversion to electrical power, but also adversely impacts the power plant conversion efficiency. The reduction in power generation is directly correlated to a reduction in revenues from power sales. Further, projects with Power Purchase Agreement (PPA) contractsmore » in place may be subject to significant economic penalties if power generation falls below the default level specified. A potential solution to restoring the performance of a power plant operating from a declining productivity geothermal resource involves the use of solar thermal energy to restore the thermal input to the geothermal power plant. There are numerous technical merits associated with a renewable geothermal-solar hybrid plant in which the two heat sources share a common power block. The geo-solar hybrid plant could provide a better match to typical electrical power demand profiles than a stand-alone geothermal plant. The hybrid plant could also eliminate the stand-alone concentrated solar power plant thermal storage requirement for operation during times of low or no solar insolation. This paper identifies hybrid plant configurations and economic conditions for which solar thermal retrofit of a geothermal power plant could improve project economics. The net present value of the concentrated solar thermal retrofit of an air-cooled binary geothermal plant is presented as functions of both solar collector array cost and electricity sales price.« less

Effect of Heat Treatment on Microstructure and Hot Impact Toughness of Various Zones of P91 Welded Pipes

NASA Astrophysics Data System (ADS)

Pandey, C.; Mahapatra, M. M.

2016-06-01

The new generation super critical thermal power plants are required to operate at enhanced thermal efficiency of over 50% to reduce the fuel consumption and environmental pollution. Creep strength-enhanced ferritic steels, commonly known as Cr-Mo alloys such as P91 (X10CrMoVNb 9-1) are such material of choice for the next generation power plants. The operating requirement of these next generation power plants is that steam temperature of around 650 °C is maintained. For such high-temperature application, creep strength of material is the primary consideration together with adequate weld heat-affected zone (HAZ) toughness. Present work deals with the effect of high service temperature on impact toughness of P91 (X10CrMoVNb 9-1) base material, weld fusion zone, and HAZ. The impact toughness of HAZ for conventional weld groove design and narrow weld groove design has been evaluated experimentally in as-welded and at different post-weld heat treatment conditions. Fractography of the impact toughness specimens of base metal, weld fusion zone, and HAZ was carried out using scanning electron microscope. The effects of heat treatment schemes on the percentage of element present at the fracture surface were also studied.

Thermal conductivity engineering in width-modulated silicon nanowires and thermoelectric efficiency enhancement

NASA Astrophysics Data System (ADS)

Zianni, Xanthippi

2018-03-01

Width-modulated nanowires have been proposed as efficient thermoelectric materials. Here, the electron and phonon transport properties and the thermoelectric efficiency are discussed for dimensions above the quantum confinement regime. The thermal conductivity decreases dramatically in the presence of thin constrictions due to their ballistic thermal resistance. It shows a scaling behavior upon the width-modulation rate that allows for thermal conductivity engineering. The electron conductivity also decreases due to enhanced boundary scattering by the constrictions. The effect of boundary scattering is weaker for electrons than for phonons and the overall thermoelectric efficiency is enhanced. A ZT enhancement by a factor of 20-30 is predicted for width-modulated nanowires compared to bulk silicon. Our findings indicate that width-modulated nanostructures are promising for developing silicon nanostructures with high thermoelectric efficiency.

Efficient thermal diode with ballistic spacer

NASA Astrophysics Data System (ADS)

Chen, Shunda; Donadio, Davide; Benenti, Giuliano; Casati, Giulio

2018-03-01

Thermal rectification is of importance not only for fundamental physics, but also for potential applications in thermal manipulations and thermal management. However, thermal rectification effect usually decays rapidly with system size. Here, we show that a mass-graded system, with two diffusive leads separated by a ballistic spacer, can exhibit large thermal rectification effect, with the rectification factor independent of system size. The underlying mechanism is explained in terms of the effective size-independent thermal gradient and the match or mismatch of the phonon bands. We also show the robustness of the thermal diode upon variation of the model's parameters. Our finding suggests a promising way for designing realistic efficient thermal diodes.

Climate impact analysis of waste treatment scenarios--thermal treatment of commercial and pretreated waste versus landfilling in Austria.

PubMed

Ragossnig, A M; Wartha, C; Pomberger, R

2009-11-01

A major challenge for modern waste management lies in a smart integration of waste-to-energy installations in local energy systems in such a way that the energy efficiency of the waste-to-energy plant is optimized and that the energy contained in the waste is, therefore, optimally utilized. The extent of integration of thermal waste treatment processes into regular energy supply systems plays a major role with regard to climate control. In this research, the specific waste management situation looked at scenarios aiming at maximizing the energy recovery from waste (i.e. actual scenario and waste-to-energy process with 75% energy efficiency [22.5% electricity, 52.5% heat]) yield greenhouse gas emission savings due to the fact that more greenhouse gas emissions are avoided in the energy sector than caused by the various waste treatment processes. Comparing dedicated waste-to-energy-systems based on the combined heat and power (CHP) process with concepts based on sole electricity production, the energy efficiency proves to be crucial with regard to climate control. This underlines the importance of choosing appropriate sites for waste-to-energy-plants. This research was looking at the effect with regard to the climate impact of various waste management scenarios that could be applied alternatively by a private waste management company in Austria. The research is, therefore, based on a specific set of data for the waste streams looked at (waste characteristics, logistics needed, etc.). Furthermore, the investigated scenarios have been defined based on the actual available alternatives with regard to the usage of treatment plants for this specific company. The standard scenarios for identifying climate impact implications due to energy recovery from waste are based on the respective marginal energy data for the power and heat generation facilities/industrial processes in Austria.

Effectiveness of Flame Retardants in TufFoam.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abelow, Alexis Elizabeth; Nissen, April; Massey, Lee Taylor

An investigation of polyurethane foam filled with known flame retardant fillers including hydroxides, melamine, phosphate-containing compounds, and melamine phosphates was carried out to produce a low-cost material with high flame retardant efficiency. The impact of flame retardant fillers on the physical properties such a s composite foam density, glass transition temperature, storage modulus, and thermal expansion of composite foams was investigated with the goal of synthesizing a robust rigid foam with excellent flame retardant properties.

Impact of Thermal Annealing on Organic Photovoltaic Cells Using Regioisomeric Donor-Acceptor-Acceptor Molecules.

PubMed

Zhang, Tao; Han, Han; Zou, Yunlong; Lee, Ying-Chi; Oshima, Hiroya; Wong, Ken-Tsung; Holmes, Russell J

2017-08-02

We report a promising set of donor-acceptor-acceptor (D-A-A) electron-donor materials based on coplanar thieno[3,2-b]/[2,3-b]indole, benzo[c][1,2,5]thiadiazole, and dicyanovinylene, which are found to show broadband absorption with high extinction coefficients. The role of the regioisomeric electron-donating thienoindole moiety on the physical and structural properties is examined. Bulk heterojunction (BHJ) organic photovoltaic cells (OPVs) based on the thieno[2,3-b]indole-based electron donor NTU-2, using C 70 as an electron acceptor, show a champion power conversion efficiency of 5.2% under AM 1.5G solar simulated illumination. This efficiency is limited by a low fill factor (FF), as has previously been the case in D-A-A systems. In order to identify the origin of the limited FF, further insight into donor layer charge-transport behavior is realized by examining planar heterojunction OPVs, with emphasis on the evolution of film morphology with thermal annealing. Compared to as-deposited OPVs that exhibit insufficient donor crystallinity, crystalline OPVs based on annealed thin films show an increase in the short-circuit current density, FF, and power conversion efficiency. These results suggest that that the crystallization of D-A-A molecules might not be realized spontaneously at room temperature and that further processing is needed to realize efficient charge transport in these materials.

Battery cell thermal-conductive coating increases efficiency

NASA Technical Reports Server (NTRS)

Doyle, H. M.

1973-01-01

Thin coating of high-temperature epoxy resin provides necessary electrical insulation, as well as good thermal conductivity between battery cells. Insulation increases efficiency of nickel-cadmium battery, as it would any multicell battery assembly in which cell-to-cell thermal balance is critical.

Fractal-Like Materials Design with Optimized Radiative Properties for High-Efficiency Solar Energy Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Clifford K.; Ortega, Jesus D.; Christian, Joshua Mark

Novel designs to increase light trapping and thermal efficiency of concentrating solar receivers at multiple length scales have been conceived, designed, and tested. The fractal-like geometries and features are introduced at both macro (meters) and meso (millimeters to centimeters) scales. Advantages include increased solar absorptance, reduced thermal emittance, and increased thermal efficiency. Radial and linear structures at the meso (tube shape and geometry) and macro (total receiver geometry and configuration) scales redirect reflected solar radiation toward the interior of the receiver for increased absorptance. Hotter regions within the interior of the receiver can reduce thermal emittance due to reduced localmore » view factors to the environment, and higher concentration ratios can be employed with similar surface irradiances to reduce the effective optical aperture, footprint, and thermal losses. Coupled optical/fluid/thermal models have been developed to evaluate the performance of these designs relative to conventional designs. Modeling results showed that fractal-like structures and geometries can increase the effective solar absorptance by 5 – 20% and the thermal efficiency by several percentage points at both the meso and macro scales, depending on factors such as intrinsic absorptance. Meso-scale prototypes were fabricated using additive manufacturing techniques, and a macro-scale bladed receiver design was fabricated using Inconel 625 tubes. On-sun tests were performed using the solar furnace and solar tower at the National Solar Thermal Test facility. The test results demonstrated enhanced solar absorptance and thermal efficiency of the fractal-like designs.« less

Thermally enhanced photoluminescence for heat harvesting in photovoltaics

PubMed Central

Manor, Assaf; Kruger, Nimrod; Sabapathy, Tamilarasan; Rotschild, Carmel

2016-01-01

The maximal Shockley–Queisser efficiency limit of 41% for single-junction photovoltaics is primarily caused by heat dissipation following energetic-photon absorption. Solar-thermophotovoltaics concepts attempt to harvest this heat loss, but the required high temperatures (T>2,000 K) hinder device realization. Conversely, we have recently demonstrated how thermally enhanced photoluminescence is an efficient optical heat-pump that operates in comparably low temperatures. Here we theoretically and experimentally demonstrate such a thermally enhanced photoluminescence based solar-energy converter. Here heat is harvested by a low bandgap photoluminescent absorber that emits thermally enhanced photoluminescence towards a higher bandgap photovoltaic cell, resulting in a maximum theoretical efficiency of 70% at a temperature of 1,140 K. We experimentally demonstrate the key feature of sub-bandgap photon thermal upconversion with an efficiency of 1.4% at only 600 K. Experiments on white light excitation of a tailored Cr:Nd:Yb glass absorber suggest that conversion efficiencies as high as 48% at 1,500 K are in reach. PMID:27762271

Solar power from satellites

NASA Technical Reports Server (NTRS)

Glaser, P. E.

1977-01-01

Microwave beaming of satellite-collected solar energy to earth for conversion to useful industrial power is evaluated for feasibility, with attention given to system efficiencies and costs, ecological impact, hardware to be employed, available options for energy conversion and transmission, and orbiting and assembly. Advantages of such a power generation and conversion system are listed, plausible techniques for conversion of solar energy (thermionic, thermal electric, photovoltaic) and transmission to earth (lasers, arrays of mirrors, microwave beams) are compared. Structural fatigue likely to result from brief daily eclipses, 55% system efficiency at the present state of the art, present projections of system costs, and projected economic implications of the technology are assessed. Two-stage orbiting and assembly plans are described.

Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former

NASA Astrophysics Data System (ADS)

Medřický, Jan; Curry, Nicholas; Pala, Zdenek; Vilemova, Monika; Chraska, Tomas; Johansson, Jimmy; Markocsan, Nicolaie

2015-04-01

Yttria-stabilized zirconia thermal barrier coatings are extensively used in turbine industry; however, increasing performance requirements have begun to make conventional air plasma sprayed coatings insufficient for future needs. Since the thermal conductivity of bulk material cannot be lowered easily; the design of highly porous coatings may be the most efficient way to achieve coatings with low thermal conductivity. Thus the approach of fabrication of coatings with a high porosity level based on plasma spraying of ceramic particles of dysprosia-stabilized zirconia mixed with polymer particles, has been tested. Both polymer and ceramic particles melt in plasma and after impact onto a substrate they form a coating. When the coating is subjected to heat treatment, polymer burns out and a complex structure of pores and cracks is formed. In order to obtain desired porosity level and microstructural features in coatings; a design of experiments, based on changes in spray distance, powder feeding rate, and plasma-forming atmosphere, was performed. Acquired coatings were evaluated for thermal conductivity and thermo-cyclic fatigue, and their morphology was assessed using scanning electron microscopy. It was shown that porosity level can be controlled by appropriate changes in spraying parameters.

Investigating Solutions to Wind Washing Issues in Two-Story Florida Homes, Phase 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Withers, Charles R.; Kono, Jamie

2015-04-13

With U.S. Department of Energy goals of reducing existing home energy use by 30% and new home energy use by 50%, it is imperative to focus on several energy efficiency measures, including the quality of air and thermal barriers. This report provides results from a second-phase research study of a phenomenon generally referred to as wind washing. Wind washing is the movement of unconditioned air around or through building thermal barriers in such a way as to diminish or nullify the intended thermal performance. In some cases, thermal and air barriers are installed very poorly or not at all, andmore » air can readily move from unconditioned attic spaces into quasi-conditioned interstitial spaces. This study focused on the impact of poorly sealed and insulated floor cavities adjacent to attic spaces in Florida homes. In these cases, unconditioned attic air can be transferred into floor cavities through pathways driven by natural factors such as wind, or by thermal differences between the floor cavity and the attic. Air can also be driven into a floor cavity through mechanical forces imposed by return duct leakage in the floor cavity.« less

Impact of the Loess Plateau on the atmospheric boundary layer structure and air quality in the North China Plain: a case study.

PubMed

Hu, Xiao-Ming; Ma, ZhiQiang; Lin, Weili; Zhang, Hongliang; Hu, Jianlin; Wang, Ying; Xu, Xiaobin; Fuentes, Jose D; Xue, Ming

2014-11-15

The North China Plain (NCP), to the east of the Loess Plateau, experiences severe regional air pollution. During the daytime in the summer, the Loess Plateau acts as an elevated heat source. The impacts of such a thermal effect on meteorological phenomena (e.g., waves, precipitation) in this region have been discussed. However, its impacts on the atmospheric boundary layer structure and air quality have not been reported. It is hypothesized that the thermal effect of the Plateau likely modulates the boundary layer structure and ambient concentrations of pollutants over the NCP under certain meteorological conditions. Thus, this study investigates such effect and its impacts using measurements and three-dimensional model simulations. It is found that in the presence of daytime westerly wind in the lower troposphere (~1 km above the NCP), warmer air above the Loess Plateau was transported over the NCP and imposed a thermal inversion above the mixed boundary layer, which acted as a lid and suppressed the mixed layer growth. As a result, pollutants accumulated in the shallow mixed layer and ozone was efficiently produced. The downward branch of the thermally-induced Mountain-Plains Solenoid circulation over the NCP contributed to enhancing the capping inversion and exacerbating air pollution. Previous studies have reported that low mixed layer, a factor for elevated pollution in the NCP, may be caused by aerosol scattering and absorption of solar radiation, frontal inversion, and large scale subsidence. The present study revealed a different mechanism (i.e., westerly warm advection) for the suppression of the mixed layer in summer NCP, which caused severe O3 pollution. This study has important implications for understanding the essential meteorological factors for pollution episodes in this region and forecasting these severe events. Copyright © 2014 Elsevier B.V. All rights reserved.

Building-Integrated Solar Energy Devices based on Wavelength Selective Films

NASA Astrophysics Data System (ADS)

Ulavi, Tejas

A potentially attractive option for building integrated solar is to employ hybrid solar collectors which serve dual purposes, combining solar thermal technology with either thin film photovoltaics or daylighting. In this study, two hybrid concepts, a hybrid photovoltaic/thermal (PV/T) collector and a hybrid 'solar window', are presented and analyzed to evaluate technical performance. In both concepts, a wavelength selective film is coupled with a compound parabolic concentrator (CPC) to reflect and concentrate the infrared portion of the solar spectrum onto a tubular absorber. The visible portion of the spectrum is transmitted through the concentrator to either a thin film Cadmium Telluride (CdTe) solar panel for electricity generation or into the interior space for daylighting. Special attention is given to the design of the hybrid devices for aesthetic building integration. An adaptive concentrator design based on asymmetrical truncation of CPCs is presented for the hybrid solar window concept. The energetic and spectral split between the solar thermal module and the PV or daylighting module are functions of the optical properties of the wavelength selective film and the concentrator geometry, and are determined using a Monte Carlo Ray-Tracing (MCRT) model. Results obtained from the MCRT can be used in conjugation with meteorological data for specific applications to study the impact of CPC design parameters including the half-acceptance angle thetac, absorber diameter D and truncation on the annual thermal and PV/daylighting efficiencies. The hybrid PV/T system is analyzed for a rooftop application in Phoenix, AZ. Compared to a system of the same area with independent solar thermal and PV modules, the hybrid PV/T provides 20% more energy, annually. However, the increase in total delivered energy is due solely to the addition of the thermal module and is achieved at an expense of a decrease in the annual electrical efficiency from 8.8% to 5.8% due to shading by the absorber tubes. For this reason, the PV/T hybrid is not recommended over other options in new installations. The hybrid solar window is evaluated for a horizontal skylight and south and east facing vertical windows in Minneapolis, MN. The predicted visible transmittance for the solar window is 0.66 to 0.73 for single glazed systems and 0.61 to 0.67 for double glazed systems. The solar heat gain coefficient and the U-factor for the window are comparable to existing glazing technology. Annual thermal efficiencies of up to 24% and 26% are predicted for the vertical window and the horizontal skylight respectively. Experimental measurements of the solar thermal component of the window confirm the trends of the model. In conclusion, the hybrid solar window combines the functionality of an energy efficient fenestration system with hybrid thermal energy generation to provide a compelling solution towards sustainable design of the built environment.

Spectral, thermal and optical-electrical properties of the layer-by-layer deposited thin film of nano Zn(II)-8-hydroxy-5-nitrosoquinolate complex.

PubMed

Haggag, Sawsan M S; Farag, A A M; Abdelrafea, Mohamed

2013-06-01

Zinc(II)-8-hydroxy-5-nitrosoquinolate, [Zn(II)-(HNOQ)2], was synthesized and assembled as a deposited thin film of nano-metal complex by a rapid, direct, simple and efficient procedure based on layer-by-layer chemical deposition technique. Stoichiometric identification and structural characterization of [Zn(II)-(HNOQ)2] were confirmed by electron impact mass spectrometry (EI-MS) and Fourier Transform infrared spectroscopy (FT-IR). Surface morphology was studied by using a scanning electron microscope imaging (SEM) and the particle size was found to be in the range of 23-49 nm. Thermal stability of [Zn(II)-(HNOQ)2] was studied and the thermal parameters were evaluated using thermal gravimetric analysis (TGA). The current density-voltage measurements showed that the current flow is dominated by a space charge limited and influenced by traps under high bias. The optical properties of [Zn(II)-(HNOQ)2] thin films were found to exhibit two direct allowed transitions at 2.4 and 1.0 eV, respectively. Copyright © 2013 Elsevier B.V. All rights reserved.

Trajectory Optimization of Electric Aircraft Subject to Subsystem Thermal Constraints

NASA Technical Reports Server (NTRS)

Falck, Robert D.; Chin, Jeffrey C.; Schnulo, Sydney L.; Burt, Jonathan M.; Gray, Justin S.

2017-01-01

Electric aircraft pose a unique design challenge in that they lack a simple way to reject waste heat from the power train. While conventional aircraft reject most of their excess heat in the exhaust stream, for electric aircraft this is not an option. To examine the implications of this challenge on electric aircraft design and performance, we developed a model of the electric subsystems for the NASA X-57 electric testbed aircraft. We then coupled this model with a model of simple 2D aircraft dynamics and used a Legendre-Gauss-Lobatto collocation optimal control approach to find optimal trajectories for the aircraft with and without thermal constraints. The results show that the X-57 heat rejection systems are well designed for maximum-range and maximum-efficiency flight, without the need to deviate from an optimal trajectory. Stressing the thermal constraints by reducing the cooling capacity or requiring faster flight has a minimal impact on performance, as the trajectory optimization technique is able to find flight paths which honor the thermal constraints with relatively minor deviations from the nominal optimal trajectory.

Modelling and simulation of heat pipes with TAIThermIR (Conference Presentation)

NASA Astrophysics Data System (ADS)

Winkelmann, Max E.

2016-10-01

Regarding thermal camouflage usually one has to reduce the surface temperature of an object. All vehicles and installations having a combustion engine usually produce a lot of heat with results on hot spots on the surface which are highly conspicuous. Using heat pipes to transfer this heat to another place on the surface more efficiently might be a way to reduce those hotspots and the overall conspicuity. In a first approach, a model for the Software TAIThermIR was developed to test which parameters of the heat pipes are relevant and what effects can be achieved. It will be shown, that the thermal resistivity of contact zones are quite relevant and the thermal coupling of the engine (source of heat) defines if the alteration of the thermal signature is large or not. Furthermore the impact of the use of heat pipes in relation to surface material is discussed. The influence of different weather scenarios on the change of signatures due to the use of heat pipes is of minor relevance and depends on the choice of the surface material. Finally application issues for real systems are discussed.

Modeling warming predicts a physiological threshold for the extinction of the living fossil frog Calyptocephalella gayi.

PubMed

Vidal, Marcela A; Novoa-Muñoz, Francisco; Werner, Enrique; Torres, Cristian; Nova, Ricardo

2017-10-01

Global climate change will have a greater impact on ectotherms in tropical and subtropical communities than at higher latitudes, because ambient temperatures are closer to the upper thermal limits of species. Amphibian species are highly dependent on external weather conditions, and the effect of global warming on these has been evaluated recently. The Great Chilean frog (Calyptocephalella gayi) is an endemic, monotypic species and genus whose conservation status is considered Vulnerable because of high extraction pressure for human consumption, lack of regulatory measures and comprehension by its consumers. Their populations have also declined due to the loss and destruction of their habitats. C. gayi has not been considered as an object of physiological study, so this large species is not known as one that can adapt to current environmental changes. In this study we analyze the thermoregulatory capacity and thermal efficiency of C. gayi to determine its potential for climatic adaptation. The results indicate that this species is strictly a thermal-conformer; its thermal efficiency and its ability to withstand high temperatures allow it to sustain itself under a climate change scenario, however, it has thermal constraints that do not allow it to withstand temperatures greater than 30°C. By modeling its ontogenetic conditions mathematically, we project that the larvae are not in danger, although there is a group of around 4% which is very close to 30°C, which is the highest temperature recorded for the species. However, about 40% of subadults and approximately 47% of adult frogs will not survive the change of ~7°C projected for the following 85 years, which will affect future generations. Copyright © 2017 Elsevier Ltd. All rights reserved.

HeatWave: the next generation of thermography devices

NASA Astrophysics Data System (ADS)

Moghadam, Peyman; Vidas, Stephen

2014-05-01

Energy sustainability is a major challenge of the 21st century. To reduce environmental impact, changes are required not only on the supply side of the energy chain by introducing renewable energy sources, but also on the demand side by reducing energy usage and improving energy efficiency. Currently, 2D thermal imaging is used for energy auditing, which measures the thermal radiation from the surfaces of objects and represents it as a set of color-mapped images that can be analysed for the purpose of energy efficiency monitoring. A limitation of such a method for energy auditing is that it lacks information on the geometry and location of objects with reference to each other, particularly across separate images. Such a limitation prevents any quantitative analysis to be done, for example, detecting any energy performance changes before and after retrofitting. To address these limitations, we have developed a next generation thermography device called Heat Wave. Heat Wave is a hand-held 3D thermography device that consists of a thermal camera, a range sensor and color camera, and can be used to generate precise 3D model of objects with augmented temperature and visible information. As an operator holding the device smoothly waves it around the objects of interest, Heat Wave can continuously track its own pose in space and integrate new information from the range and thermal and color cameras into a single, and precise 3D multi-modal model. Information from multiple viewpoints can be incorporated together to improve the accuracy, reliability and robustness of the global model. The approach also makes it possible to reduce any systematic errors associated with the estimation of surface temperature from the thermal images.

Efficiency and its bounds for thermal engines at maximum power using Newton's law of cooling.

PubMed

Yan, H; Guo, Hao

2012-01-01

We study a thermal engine model for which Newton's cooling law is obeyed during heat transfer processes. The thermal efficiency and its bounds at maximum output power are derived and discussed. This model, though quite simple, can be applied not only to Carnot engines but also to four other types of engines. For the long thermal contact time limit, new bounds, tighter than what were known before, are obtained. In this case, this model can simulate Otto, Joule-Brayton, Diesel, and Atkinson engines. While in the short contact time limit, which corresponds to the Carnot cycle, the same efficiency bounds as that from Esposito et al. [Phys. Rev. Lett. 105, 150603 (2010)] are derived. In both cases, the thermal efficiency decreases as the ratio between the heat capacities of the working medium during heating and cooling stages increases. This might provide instructions for designing real engines. © 2012 American Physical Society

Facile thiol-ene thermal crosslinking reaction facilitated hole-transporting layer for highly efficient and stable perovskite solar cells

DOE PAGES

Li, Zhong'an; Zhu, Zonglong; Chueh, Chu -Chen; ...

2016-08-08

A crosslinked organic hole-transporting layer (HTL) is developed to realize highly efficient and stable perovskite solar cells via a facile thiol-ene thermal reaction. This crosslinked HTL not only facilitates hole extraction from perovskites, but also functions as an effective protective barrier. Lastly, a high-performance (power conversion efficiency: 18.3%) device is demonstrated to show respectable photo and thermal stability without encapsulation.

Integrated photovoltaic-thermal solar energy conversion systems

NASA Technical Reports Server (NTRS)

Samara, G. A.

1975-01-01

A combined photovoltaic/thermal collector has been built and is now being tested. Initial tests have concentrated on evaluating the thermal efficiency of the collector before and after the silicon cells are mounted. With likely improvements in bonding between cells and receiver and in the absorptivity of the cells, thermal efficiencies greater than 50% can be expected for the combined receiver operating at 100 C.

Study on optoelectronic properties of Spiro-CN for developing an efficient OLED

NASA Astrophysics Data System (ADS)

Mishra, Ashok Kumar

2018-05-01

There are a class of organic molecules and polymers which exhibit semiconductor behavior because of nearly free conjugate π-electrons. Hopping of these electrons in molecules forms different excited singlet and triplet states named as excitons. Some of these organic molecules can be set to emit photons by triplet-singlet excitonic transition via a process called Thermally Activated Delayed Fluorescence (TADF) which is exploited for designing the Organic Light Emitting diode (OLED.) Spiro-CN (spirobifluorene skeletons) Spiro is one of these reported noble metal-free TADF molecules which offers unique optical and electronic properties arising from the efficient transition and reverse intersystem crossing between the lowest singlet (S) and triplet (T) excited states. Its ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T→S) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic device. In the present study, the Spiro-CN compounds have been taken up for the investigation of various optoelectronic properties including the thermally activated delayed fluorescence (TADF) by using the Koopmans Method and Density Functional Theory. The present study discusses the utility of the Spiro-CN organic semiconductor as a suitable TADF material essential for developing an efficient Organic Light Emitting Diode (OLED).

A study of Ground Source Heat Pump based on a heat infiltrates coupling model established with FEFLOW

NASA Astrophysics Data System (ADS)

Chen, H.; Hu, C.; Chen, G.; Zhang, Q.

2017-12-01

Geothermal heat is a viable source of energy and its environmental impact in terms of CO2 emissions is significantly lower than conventional fossil fuels. it is vital that engineers acquire a proper understanding about the Ground Source Heat Pump (GSHP). In this study, the model of the borehole exchanger under conduction manners and heat infiltrates coupling manners was established with FEFLOW. The energy efficiency, heat transfer endurance and heat transfer in the unit depth were introduced to quantify the energy efficient and the endurance period. The performance of a the Borehole Exchanger (BHE) in soil with and without groundwater seepage was analyzed of heat transfer process between the soil and the working fluid. Basing on the model, the varied regularity of energy efficiency performance an heat transfer endurance with the conditions including the different configuration of the BHE, the soil properties, thermal load characteristic were discussed. Focus on the heat transfer process in multi-layer soil which one layer exist groundwater flow. And an investigation about thermal dispersivity was also analyzed its influence on heat transfer performance. The final result proves that the model of heat infiltrates coupling model established in this context is reasonable, which can be applied to engineering design.

Magnetically Enhanced Solid-Liquid Separation

NASA Astrophysics Data System (ADS)

Rey, C. M.; Keller, K.; Fuchs, B.

2005-07-01

DuPont is developing an entirely new method of solid-liquid filtration involving the use of magnetic fields and magnetic field gradients. The new hybrid process, entitled Magnetically Enhanced Solid-Liquid Separation (MESLS), is designed to improve the de-watering kinetics and reduce the residual moisture content of solid particulates mechanically separated from liquid slurries. Gravitation, pressure, temperature, centrifugation, and fluid dynamics have dictated traditional solid-liquid separation for the past 50 years. The introduction of an external field (i.e. the magnetic field) offers the promise to manipulate particle behavior in an entirely new manner, which leads to increased process efficiency. Traditional solid-liquid separation typically consists of two primary steps. The first is a mechanical step in which the solid particulate is separated from the liquid using e.g. gas pressure through a filter membrane, centrifugation, etc. The second step is a thermal drying process, which is required due to imperfect mechanical separation. The thermal drying process is over 100-200 times less energy efficient than the mechanical step. Since enormous volumes of materials are processed each year, more efficient mechanical solid-liquid separations can be leveraged into dramatic reductions in overall energy consumption by reducing downstream drying requirements have a tremendous impact on energy consumption. Using DuPont's MESLS process, initial test results showed four very important effects of the magnetic field on the solid-liquid filtration process: 1) reduction of the time to reach gas breakthrough, 2) less loss of solid into the filtrate, 3) reduction of the (solids) residual moisture content, and 4) acceleration of the de-watering kinetics. These test results and their potential impact on future commercial solid-liquid filtration is discussed. New applications can be found in mining, chemical and bioprocesses.

Semiconducting lithium indium diselenide: Charge-carrier properties and the impacts of high flux thermal neutron irradiation

NASA Astrophysics Data System (ADS)

Hamm, Daniel S.; Rust, Mikah; Herrera, Elan H.; Matei, Liviu; Buliga, Vladimir; Groza, Michael; Burger, Arnold; Stowe, Ashley; Preston, Jeff; Lukosi, Eric D.

2018-06-01

This paper reports on the charge carrier properties of several lithium indium diselenide (LISe) semiconductors. It was found that the charge collection efficiency of LISe was improved after high flux thermal neutron irradiation including the presence of a typically unobservable alpha peak from hole-only collection. Charge carrier trap energies of the irradiated sample were measured using photo-induced current transient spectroscopy. Compared to previous studies of this material, no significant differences in trap energies were observed. Through trap-filled limited voltage measurements, neutron irradiation was found to increase the density of trap states within the bulk of the semiconductor, which created a polarization effect under alpha exposure but not neutron exposure. Further, the charge collection efficiency of the irradiated sample was higher (14-15 fC) than that of alpha particles (3-5 fC), indicating that an increase in hole signal contribution resulted from the neutron irradiation. Finally, it was observed that significant charge loss takes place near the point of generation, producing a significant scintillation response and artificially inflating the W-value of all semiconducting LISe crystals.

On the Roles of Upper- versus Lower-level Thermal Forcing in Shifting the Eddy-Driven Jet

NASA Astrophysics Data System (ADS)

Zhang, Y.; Nie, Y.; Chen, G.; Yang, X. Q.

2017-12-01

One most drastic atmospheric change in the global warming scenario is the increase in temperature over tropical upper-troposphere and polar surface. The strong warming over those two area alters the spacial distributions of the baroclinicity in the upper-troposphere of subtropics and in the lower-level of subpolar region, with competing effects on the mid-latitude atmospheric circulation. The final destination of the eddy-driven jet in future climate could be "a tug of war" between the impacts of such upper- versus lower-level thermal forcing. In this study, the roles of upper- versus lower-level thermal forcing in shifting the eddy-driven jet are investigated using a nonlinear multi-level quasi-geostrophic channel model. All of our sensitivity experiments show that the latitudinal position of the eddy-driven jet is more sensitive to the upper-level thermal forcing. Such upper-level dominance over the lower-level forcing can be attributed to the different mechanisms through which eddy-driven jet responses to them. The upper-level thermal forcing induces a jet shift mainly by affecting the baroclinic generation of eddies, which supports the latitudinal shift of the eddy momentum flux convergence. The jet response to the lower-level thermal forcing, however, is strongly "eddy dissipation control". The lower-level forcing, by changing the baroclinicity in the lower troposphere, induces a direct thermal zonal wind response in the upper level thus modifies the nonlinear wave breaking and the resultant irreversible eddy mixing, which amplifies the latitudinal shift of the eddy-driven jet. Whether the eddy response is "generation control" or "dissipation control" may strongly depend on the eddy behavior in its baroclinic processes. Only the anomalous eddy generation that penetrates into the upper troposphere can have a striking impact on the eddy momentum flux, which pushes the jet shift more efficiently and dominates the eddy response.

A study of power cycles using supercritical carbon dioxide as the working fluid

NASA Astrophysics Data System (ADS)

Schroder, Andrew Urban

A real fluid heat engine power cycle analysis code has been developed for analyzing the zero dimensional performance of a general recuperated, recompression, precompression supercritical carbon dioxide power cycle with reheat and a unique shaft configuration. With the proposed shaft configuration, several smaller compressor-turbine pairs could be placed inside of a pressure vessel in order to avoid high speed, high pressure rotating seals. The small compressor-turbine pairs would share some resemblance with a turbocharger assembly. Variation in fluid properties within the heat exchangers is taken into account by discretizing zero dimensional heat exchangers. The cycle analysis code allows for multiple reheat stages, as well as an option for the main compressor to be powered by a dedicated turbine or an electrical motor. Variation in performance with respect to design heat exchanger pressure drops and minimum temperature differences, precompressor pressure ratio, main compressor pressure ratio, recompression mass fraction, main compressor inlet pressure, and low temperature recuperator mass fraction have been explored throughout a range of each design parameter. Turbomachinery isentropic efficiencies are implemented and the sensitivity of the cycle performance and the optimal design parameters is explored. Sensitivity of the cycle performance and optimal design parameters is studied with respect to the minimum heat rejection temperature and the maximum heat addition temperature. A hybrid stochastic and gradient based optimization technique has been used to optimize critical design parameters for maximum engine thermal efficiency. A parallel design exploration mode was also developed in order to rapidly conduct the parameter sweeps in this design space exploration. A cycle thermal efficiency of 49.6% is predicted with a 320K [47°C] minimum temperature and 923K [650°C] maximum temperature. The real fluid heat engine power cycle analysis code was expanded to study a theoretical recuperated Lenoir cycle using supercritical carbon dioxide as the working fluid. The real fluid cycle analysis code was also enhanced to study a combined cycle engine cascade. Two engine cascade configurations were studied. The first consisted of a traditional open loop gas turbine, coupled with a series of recuperated, recompression, precompression supercritical carbon dioxide power cycles, with a predicted combined cycle thermal efficiency of 65.0% using a peak temperature of 1,890K [1,617°C]. The second configuration consisted of a hybrid natural gas powered solid oxide fuel cell and gas turbine, coupled with a series of recuperated, recompression, precompression supercritical carbon dioxide power cycles, with a predicted combined cycle thermal efficiency of 73.1%. Both configurations had a minimum temperature of 306K [33°C]. The hybrid stochastic and gradient based optimization technique was used to optimize all engine design parameters for each engine in the cascade such that the entire engine cascade achieved the maximum thermal efficiency. The parallel design exploration mode was also utilized in order to understand the impact of different design parameters on the overall engine cascade thermal efficiency. Two dimensional conjugate heat transfer (CHT) numerical simulations of a straight, equal height channel heat exchanger using supercritical carbon dioxide were conducted at various Reynolds numbers and channel lengths.

Chapter 14: Chiller Evaluation Protocol. The Uniform Methods Project: Methods for Determining Energy Efficiency Savings for Specific Measures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurnik, Charles W; Tiessen, Alex

This protocol defines a chiller measure as a project that directly impacts equipment within the boundary of a chiller plant. A chiller plant encompasses a chiller - or multiple chillers - and associated auxiliary equipment. This protocol primarily covers electric-driven chillers and chiller plants. It does not include thermal energy storage and absorption chillers fired by natural gas or steam, although a similar methodology may be applicable to these chilled water system components.

Effect of ultrasonication in synthesis of gold nano fluid for thermal applications

NASA Astrophysics Data System (ADS)

Nath, G.; Giri, R.

2018-02-01

Ultrasonically synthesized nanofluids are efficient coolant and heat exchanger material has demonstrated its potential in various fields and thermal engineering. The computation of different acoustical parameter using the ultrasonic velocity data of gold nanofluids are taken in estimation of thermal conductivity. The computational and experimental measured values of thermal conductivity are well agrees. The results execute ultrasonically synthesized gold nanofluids is an economic and efficient technology for explaining the increase of thermal conductivity of nanofluids in suitable optimum conditions.

A new mechanism for the formation of regolith on asteroids

NASA Astrophysics Data System (ADS)

Delbo, Marco; Libourel, Guy; Wilkerson, Justin; Murdoch, Naomi; Michel, Patrick; Ramesh, Kt; Ganino, Clement; Verati, Chrystele; Marchi, Simone

2014-11-01

The soil of asteroids, like that of the Moon, and other rocky, airless bodies in the Solar System, is made of a layer of pebbles, sand, and dust called regolith.Previous works suggested that the regolith on asteroids is made from material ejected from impacts and re-accumulated on the surface and from surface rocks that are broken down by micrometeoroid impacts. However, this regolith formation process has problems to explain the regolith on km-sized and smaller asteroids: it is known that impact fragments can reach escape velocities and breaks free from the gravitational forces of these small asteroids, indicating the impact mechanism is not the dominant process for regolith creation. Other studies also reveal that there is too much regolith on small asteroids’ surfaces to have been deposited there solely by impacts over the millions of years of asteroids’ evolution.We proposed that another process is capable of gently breaking rocks at the surface of asteroids: thermal fatigue by temperature cycling. As asteroids spin about their rotation axes, their surfaces go in and out of shadow resulting in large surface temperature variations. The rapid heating and cooling creates thermal expansion and contraction in the asteroid material, initiating cracking and propagating existing cracks. As the process is repeated over and over, the crack damage increases with time, leading eventually to rock fragmentation (and production of new regolith).To study this process, in the laboratory, we subjected meteorites, used as asteroid material analogs, to 37 days of thermal cycles similar to those occurring on asteroids. We measured cracks widening at an average rate of 0.5 mm/y. Some fragments were also produced, indicating meteorite fragmentation. To scale our results to asteroid lifetime, we incorporated our measurements into a fracture model and we deduced that thermal cycling is more efficient than micrometeorite bombardment at fragmenting rock over millions of years on asteroids (see Delbo et al. 2014. Nature 508, 233-236).This work was supported by the French Agence National de la Recherche (ANR) SHOCKS,

Optically Transparent Thermally Insulating Silica Aerogels for Solar Thermal Insulation.

PubMed

Günay, A Alperen; Kim, Hannah; Nagarajan, Naveen; Lopez, Mateusz; Kantharaj, Rajath; Alsaati, Albraa; Marconnet, Amy; Lenert, Andrej; Miljkovic, Nenad

2018-04-18

Rooftop solar thermal collectors have the potential to meet residential heating demands if deployed efficiently at low solar irradiance (i.e., 1 sun). The efficiency of solar thermal collectors depends on their ability to absorb incoming solar energy and minimize thermal losses. Most techniques utilize a vacuum gap between the solar absorber and the surroundings to eliminate conduction and convection losses, in combination with surface coatings to minimize reradiation losses. Here, we present an alternative approach that operates at atmospheric pressure with simple, black, absorbing surfaces. Silica based aerogels coated on black surfaces have the potential to act as simple and inexpensive solar thermal collectors because of their high transmission to solar radiation and low transmission to thermal radiation. To demonstrate their heat-trapping properties, we fabricated tetramethyl orthosilicate-based silica aerogels. A hydrophilic aerogel with a thickness of 1 cm exhibited a solar-averaged transmission of 76% and thermally averaged transmission of ≈1% (at 100 °C). To minimize unwanted solar absorption by O-H groups, we functionalized the aerogel to be hydrophobic, resulting in a solar-averaged transmission of 88%. To provide a deeper understanding of the link between aerogel properties and overall efficiency, we developed a coupled radiative-conductive heat transfer model and used it to predict solar thermal performance. Instantaneous solar thermal efficiencies approaching 55% at 1 sun and 80 °C were predicted. This study sheds light on the applicability of silica aerogels on black coatings for solar thermal collectors and offers design priorities for next-generation solar thermal aerogels.

Modern maize hybrids in Northeast China exhibit increased yield potential and resource use efficiency despite adverse climate change.

PubMed

Chen, Xiaochao; Chen, Fanjun; Chen, Yanling; Gao, Qiang; Yang, Xiaoli; Yuan, Lixing; Zhang, Fusuo; Mi, Guohua

2013-03-01

The impact of global changes on food security is of serious concern. Breeding novel crop cultivars adaptable to climate change is one potential solution, but this approach requires an understanding of complex adaptive traits for climate-change conditions. In this study, plant growth, nitrogen (N) uptake, and yield in relation to climatic resource use efficiency of nine representative maize cultivars released between 1973 and 2000 in China were investigated in a 2-year field experiment under three N applications. The Hybrid-Maize model was used to simulate maize yield potential in the period from 1973 to 2011. During the past four decades, the total thermal time (growing degree days) increased whereas the total precipitation and sunshine hours decreased. This climate change led to a reduction of maize potential yield by an average of 12.9% across different hybrids. However, the potential yield of individual hybrids increased by 118.5 kg ha(-1)  yr(-1) with increasing year of release. From 1973 to 2000, the use efficiency of sunshine hours, thermal time, and precipitation resources increased by 37%, 40%, and 41%, respectively. The late developed hybrids showed less reduction in yield potential in current climate conditions than old cultivars, indicating some adaptation to new conditions. Since the mid-1990s, however, the yield impact of climate change exhibited little change, and even a slight worsening for new cultivars. Modern breeding increased ear fertility and grain-filling rate, and delayed leaf senescence without modification in net photosynthetic rate. The trade-off associated with delayed leaf senescence was decreased grain N concentration rather than increased plant N uptake, therefore N agronomic efficiency increased simultaneously. It is concluded that modern maize hybrids tolerate the climatic changes mainly by constitutively optimizing plant productivity. Maize breeding programs in the future should pay more attention to cope with the limiting climate factors specifically. © 2012 Blackwell Publishing Ltd.

Experimental investigations of hybrid PV/Spiral flow thermal collector system performance using Al2O3/water nanofluid

NASA Astrophysics Data System (ADS)

Gangadevi, R.; Vinayagam, B. K.; Senthilraja, S.

2017-05-01

In this paper, the PV/T (Photovoltaic thermal unit) system is investigated experimentally to examine the thermal, electrical and overall efficiency by circulating Al2O3/water nanofluid of 1wt% and 2wt% with an optimum flow rate of 40L/H. The overall efficiency of PVT system is largely influenced by various factors such as heat due to photovoltaic action; energy radiated at the infrared wavelength of the solar spectrum, solar irradiance, mounting structure, tilt angle, wind speed direction, Ambient temperature and panel material composition. However, the major factor is considered in this study to extract the heat generated in the PV panel by using nanofluid as a coolant to increase the overall system efficiency. Therefore, the result shows that by using 2 wt% Al2O3/water nanofluid the electrical efficiency, thermal efficiency and overall efficiency of the PVT system enhanced by 13%, 45%, and 58% respectively compared with water.

Energy Engineering Analysis Program. Lighting Survey of Selected Buildings, Pine Bluff Arsenal, Pine Bluff, Arkansas. Volume 2A: Appendices

DTIC Science & Technology

1995-06-01

Energy efficient, 30 and 40 watt ballasts are Rapid Start, thermally protected, automatic resetting. Class P, high or low power factor as required...BALLASTS Energy efficient, 30 ana 40 watt Rapic Start, thermally protected, automatic resetting. Class P. high power factor, CEM, sound rated A. unless...BALLASTS Energy efficient, 40 Watt Rapid Start, thermally protected, automatic resetting, Class P, high power factor, CBM, sound rated A, unless

Thermally regenerative hydrogen/oxygen fuel cell power cycles

NASA Technical Reports Server (NTRS)

Morehouse, J. H.

1986-01-01

Two innovative thermodynamic power cycles are analytically examined for future engineering feasibility. The power cycles use a hydrogen-oxygen fuel cell for electrical energy production and use the thermal dissociation of water for regeneration of the hydrogen and oxygen. The TDS (thermal dissociation system) uses a thermal energy input at over 2000 K to thermally dissociate the water. The other cycle, the HTE (high temperature electrolyzer) system, dissociates the water using an electrolyzer operating at high temperature (1300 K) which receives its electrical energy from the fuel cell. The primary advantages of these cycles is that they are basically a no moving parts system, thus having the potential for long life and high reliability, and they have the potential for high thermal efficiency. Both cycles are shown to be classical heat engines with ideal efficiency close to Carnot cycle efficiency. The feasibility of constructing actual cycles is investigated by examining process irreversibilities and device efficiencies for the two types of cycles. The results show that while the processes and devices of the 2000 K TDS exceed current technology limits, the high temperature electrolyzer system appears to be a state-of-the-art technology development. The requirements for very high electrolyzer and fuel cell efficiencies are seen as determining the feasbility of the HTE system, and these high efficiency devices are currently being developed. It is concluded that a proof-of-concept HTE system experiment can and should be conducted.

Efficient solar-driven synthesis, carbon capture, and desalinization, STEP: solar thermal electrochemical production of fuels, metals, bleach.

PubMed

Licht, S

2011-12-15

STEP (solar thermal electrochemical production) theory is derived and experimentally verified for the electrosynthesis of energetic molecules at solar energy efficiency greater than any photovoltaic conversion efficiency. In STEP the efficient formation of metals, fuels, chlorine, and carbon capture is driven by solar thermal heated endothermic electrolyses of concentrated reactants occuring at a voltage below that of the room temperature energy stored in the products. One example is CO(2) , which is reduced to either fuels or storable carbon at a solar efficiency of over 50% due to a synergy of efficient solar thermal absorption and electrochemical conversion at high temperature and reactant concentration. CO(2) -free production of iron by STEP, from iron ore, occurs via Fe(III) in molten carbonate. Water is efficiently split to hydrogen by molten hydroxide electrolysis, and chlorine, sodium, and magnesium from molten chlorides. A pathway is provided for the STEP decrease of atmospheric carbon dioxide levels to pre-industial age levels in 10 years. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A dual-stage sodium thermal electrochemical converter (Na-TEC)

NASA Astrophysics Data System (ADS)

Limia, Alexander; Ha, Jong Min; Kottke, Peter; Gunawan, Andrey; Fedorov, Andrei G.; Lee, Seung Woo; Yee, Shannon K.

2017-12-01

The sodium thermal electrochemical converter (Na-TEC) is a heat engine that generates electricity through the isothermal expansion of sodium ions. The Na-TEC is a closed system that can theoretically achieve conversion efficiencies above 45% when operating between thermal reservoirs at 1150 K and 550 K. However, thermal designs have confined previous single-stage devices to thermal efficiencies below 20%. To mitigate some of these limitations, we consider dividing the isothermal expansion into two stages; one at the evaporator temperature (1150 K) and another at an intermediate temperature (650 K-1050 K). This dual-stage Na-TEC takes advantage of regeneration and reheating, and could be amenable to better thermal management. Herein, we demonstrate how the dual-stage device can improve the efficiency by up to 8% points over the best performing single-stage device. We also establish an application regime map for the single- and dual-stage Na-TEC in terms of the power density and the total thermal parasitic loss. Generally, a single-stage Na-TEC should be used for applications requiring high power densities, whereas a dual-stage Na-TEC should be used for applications requiring high efficiency.

Study on cold head structure of a 300 Hz thermoacoustically driven pulse tube cryocooler

NASA Astrophysics Data System (ADS)

Yu, G. Y.; Wang, X. T.; Dai, W.; Luo, E. C.

2012-04-01

High reliability, compact size and potentially high thermal efficiency make the high frequency thermoacoustically-driven pulse tube cryocooler quite promising for space use. With continuous efforts, the lowest temperature and the thermal efficiency of the coupled system have been greatly improved. So far, a cold head temperature below 60 K has been achieved on such kind of cryocooler with the operation frequency of around 300 Hz. To further improve the thermal efficiency and expedite its practical application, this work focuses on studying the influence of cold head structure on the system performance. Substantial numerical simulations were firstly carried out, which revealed that the cold head structure would greatly influence the cooling power and the thermal efficiency. To validate the predictions, a lot of experiments have been done. The experiments and calculations are in reasonable agreement. With 500 W heating power input into the engine, a no-load temperature of 63 K and a cooling power of 1.16 W at 80 K have been obtained with parallel-plate cold head, indicating encouraging improvement of the thermal efficiency.

Study of the electrical and thermal performances of photovoltaic thermal collector-compound parabolic concentrated

NASA Astrophysics Data System (ADS)

Jaaz, Ahed Hameed; Sopian, Kamaruzzaman; Gaaz, Tayser Sumer

2018-06-01

The importance of utilizing the solar energy as a very suitable source among multi-source approaches to replace the conventional energy is on the rise in the last four decades. The invention of the photovoltaic module (PV) could be the corner stone in this process. However, the limited amount of energy obtained from PV was and still the main challenge of full utilization of the solar energy. In this paper, the use of the compound parabolic concentrator (CPC) along with the thermal photovoltaic module (PVT) where the cooling process of the CPC is conducted using a novel technique of water jet impingement has applied experimentally and physically tested. The test includes the effect of water jet impingement on the total power, electrical efficiency, thermal efficiency, and total efficiency on CPC-PVT system. The cooling process at the maximum irradiation by water jet impingement resulted in improving the electrical efficiency by 7%, total output power by 31% and the thermal efficiency by 81%. These results outperform the recent highest results recorded by the most recent work.

Evaluating the efficacy of a thermal exposure chamber designed for assessing workers' thermal hazard.

PubMed

Tsai, Perng-Jy; Lo, Chuh-Lun; Sun, Yih-Min; Juang, Yow-Jer; Liu, Hung-Hsin; Chen, Wang-Yi; Yeh, Wen-Yu

2003-05-01

This study was conducted on a thermal exposure chamber designed for assessing workers' thermal hazard. In order to assess the efficacy of the studied chamber, three environmental conditions were selected to simulate high, middle and low thermal impact situations, with air temperatures (Ta) of 43.12, 36.23 and 25.77 masculine C, globe temperatures (Tg) of 44.41, 41.07 and 29.24 masculine C, relative humidity (RH) of 77, 59 and 39%, and air flow velocities (Va) of 1.70, 0.91 and 0.25 m/s, respectively. For the three specified thermal impact conditions, results show that the coefficients of variation (CVs) for Ta, Tg, RH and Va measured in the chamber studied were consistently less than 10%, except for Va under the low thermal impact condition (=50%). For each specified thermal impact condition, we generated 1,000 environmental combinations by using the Monte Carlo simulation approach according to the variations obtained from the four environmental factors. We directly adopted the ISO 7933 approach to estimate the allowable exposure time (AET) for each simulated environmental condition. This study yielded a range in the 95% confidence interval (95% CI) of the estimated AETs for the three specified thermal impact conditions which were consistently less than 5 min. We further conducted the sensitivity analysis to examine the effect of the four environmental factors on estimating AETs. We found Va was the least important factor in estimating AETs for any specified thermal impact condition. In conclusion, although Va was found with great variation for the chamber specified in the low thermal impact condition, the exposure chamber studied can still be regarded as a feasible one for assessing workers' thermal hazard.

Acceleration efficiency in nonthermal sources and the soft gamma rays from NGC 4151 observed by OSSE and SIGMA

NASA Technical Reports Server (NTRS)

Zdziarski, Andrzej A.; Lightman, Alan P.; Maciolek-Niedzwiecki, Andrzej

1993-01-01

We show that the recent observations of the Seyfert galaxy NGC 4151 in hard X-rays and soft gamma rays by the OSSE and SIGMA detectors on board CGRO and GRANAT, respectively, are well explained by a nonthermal model with acceleration of relativistic electrons at an efficiency of less than 50 percent and with the remaining power dissipated thermally in the source (the standard nonthermal e(+/-) pair model assumed 100 percent efficiency). Such an acceleration efficiency is generally expected on physical grounds. The resulting model unifies previously proposed purely thermal and purely nonthermal models. The pure nonthermal model for NGC 4151 appears to be ruled out. The pure thermal model gives a worse fit to the data than our hybrid nonthermal/thermal model.

Estimation of the temperature spatial variability in confined spaces based on thermal imaging

NASA Astrophysics Data System (ADS)

Augustyn, Grzegorz; Jurasz, Jakub; Jurczyk, Krzysztof; Korbiel, Tomasz; Mikulik, Jerzy; Pawlik, Marcin; Rumin, Rafał

2017-11-01

In developed countries the salaries of office workers are several times higher than the total cost of maintaining and operating the building. Therefore even a small improvement in human work productivity and performance as a result of enhancing the quality of their work environment may lead to a meaningful economic benefits. The air temperature is the most commonly used indicator in assessing the indoor environment quality. What is more, it is well known that thermal comfort has the biggest impact on employees performance and their ability to work efficiently. In majority of office buildings, indoor temperature is managed by heating, ventilation and air conditioning (HVAC) appliances. However the way how they are currently managed and controlled leads to the nonhomogeneous distribution of temperature in certain space. An approach to determining the spatial variability of temperature in confined spaces was introduced based on thermal imaging temperature measurements. The conducted research and obtained results enabled positive verification of the method and creation of surface plot illustrating the temperature variability.

Evaluation of dispersion strengthened nickel-base alloy heat shields for space shuttle application

NASA Technical Reports Server (NTRS)

Johnson, R., Jr.; Killpatrick, D. H.

1976-01-01

The results obtained in a program to evaluate dispersion-strengthened nickel-base alloys for use in a metallic radiative thermal protection system operating at surface temperatures to 1477 K for the space shuttle were presented. Vehicle environments having critical effects on the thermal protection system are defined; TD Ni-20Cr characteristics of material used in the current study are compared with previous results; cyclic load, temperature, and pressure effects on sheet material residual strength are investigated; the effects of braze reinforcement in improving the efficiency of spotwelded joints are evaluated; parametric studies of metallic radiative thermal protection systems are reported; and the design, instrumentation, and testing of full scale subsize heat shield panels in two configurations are described. Initial tests of full scale subsize panels included simulated meteoroid impact tests, simulated entry flight aerodynamic heating, programmed differential pressure loads and temperatures simulating mission conditions, and acoustic tests simulating sound levels experienced during boost flight.

Efficiency and its bounds for a quantum Einstein engine at maximum power.

PubMed

Yan, H; Guo, Hao

2012-11-01

We study a quantum thermal engine model for which the heat transfer law is determined by Einstein's theory of radiation. The working substance of the quantum engine is assumed to be a two-level quantum system of which the constituent particles obey Maxwell-Boltzmann (MB), Fermi-Dirac (FD), or Bose-Einstein (BE) distributions, respectively, at equilibrium. The thermal efficiency and its bounds at maximum power of these models are derived and discussed in the long and short thermal contact time limits. The similarity and difference between these models are discussed. We also compare the efficiency bounds of this quantum thermal engine to those of its classical counterpart.

Limits to solar power conversion efficiency with applications to quantum and thermal systems

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Buoncristiani, A. M.; Smith, B. T.

1983-01-01

An analytical framework is presented that permits examination of the limit to the efficiency of various solar power conversion devices. Thermodynamic limits to solar power efficiency are determined for both quantum and thermal systems, and the results are applied to a variety of devices currently considered for use in space systems. The power conversion efficiency for single-threshold energy quantum systems receiving unconcentrated air mass zero solar radiation is limited to 31 percent. This limit applies to photovoltaic cells directly converting solar radiation, or indirectly, as in the case of a thermophotovoltaic system. Photoelectrochemical cells rely on an additional chemical reaction at the semiconductor-electrolyte interface, which introduces additional second-law demands and a reduction of the solar conversion efficiency. Photochemical systems exhibit even lower possible efficiencies because of their relatively narrow absorption bands. Solar-powered thermal engines in contact with an ambient reservoir at 300 K and operating at maximum power have a peak conversion efficiency of 64 percent, and this occurs for a thermal reservoir at a temperature of 2900 K. The power conversion efficiency of a solar-powered liquid metal magnetohydrodydnamic generator, a solar-powered steam turbine electric generator, and an alkali metal thermoelectric converter is discussed.

The thermal impact of aquifer thermal energy storage (ATES) systems: a case study in the Netherlands, combining monitoring and modeling

NASA Astrophysics Data System (ADS)

Visser, Philip W.; Kooi, Henk; Stuyfzand, Pieter J.

2015-05-01

Results are presented of a comprehensive thermal impact study on an aquifer thermal energy storage (ATES) system in Bilthoven, the Netherlands. The study involved monitoring of the thermal impact and modeling of the three-dimensional temperature evolution of the storage aquifer and over- and underlying units. Special attention was paid to non-uniformity of the background temperature, which varies laterally and vertically in the aquifer. Two models were applied with different levels of detail regarding initial conditions and heterogeneity of hydraulic and thermal properties: a fine-scale heterogeneity model which construed the lateral and vertical temperature distribution more realistically, and a simplified model which represented the aquifer system with only a limited number of homogeneous layers. Fine-scale heterogeneity was shown to be important to accurately model the ATES-impacted vertical temperature distribution and the maximum and minimum temperatures in the storage aquifer, and the spatial extent of the thermal plumes. The fine-scale heterogeneity model resulted in larger thermally impacted areas and larger temperature anomalies than the simplified model. The models showed that scattered and scarce monitoring data of ATES-induced temperatures can be interpreted in a useful way by groundwater and heat transport modeling, resulting in a realistic assessment of the thermal impact.

Nano-engineered Multiwall Carbon Nanotube-copper Composite Thermal Interface Material for Efficient Heat Conduction

NASA Technical Reports Server (NTRS)

Ngo, Quoc; Cruden, Brett A.; Cassell, Alan M.; Sims, Gerard; Li, Jun; Meyyappa, M.; Yang, Cary Y.

2005-01-01

Efforts in integrated circuit (IC) packaging technologies have recently been focused on management of increasing heat density associated with high frequency and high density circuit designs. While current flip-chip package designs can accommodate relatively high amounts of heat density, new materials need to be developed to manage thermal effects of next-generation integrated circuits. Multiwall carbon nanotubes (MWNT) have been shown to significantly enhance thermal conduction in the axial direction and thus can be considered to be a candidate for future thermal interface materials by facilitating efficient thermal transport. This work focuses on fabrication and characterization of a robust MWNT-copper composite material as an element in IC package designs. We show that using vertically aligned MWNT arrays reduces interfacial thermal resistance by increasing conduction surface area, and furthermore, the embedded copper acts as a lateral heat spreader to efficiently disperse heat, a necessary function for packaging materials. In addition, we demonstrate reusability of the material, and the absence of residue on the contacting material, both novel features of the MWNT-copper composite that are not found in most state-of-the-art thermal interface materials. Electrochemical methods such as metal deposition and etch are discussed for the creation of the MWNT-Cu composite, detailing issues and observations with using such methods. We show that precise engineering of the composite surface affects the ability of this material to act as an efficient thermal interface material. A thermal contact resistance measurement has been designed to obtain a value of thermal contact resistance for a variety of different thermal contact materials.

Transparent layered YAG ceramics with structured Yb doping produced via tape casting

NASA Astrophysics Data System (ADS)

Hostaša, Jan; Piancastelli, Andreana; Toci, Guido; Vannini, Matteo; Biasini, Valentina

2017-03-01

The flexibility of the ceramic production process, in particular in terms of shaping and spatial control of distribution of active ions, is one of the strong points in favor of transparent ceramics. In high power lasers in particular, where thermal management is a critical issue, the finely controlled design of spatial distribution of the doping ions within the laser gain media can reduce undesired thermally induced effects and large temperature gradients, and thus enhance the efficiency and laser beam quality especially under increased thermal load. In the present work transparent structured YAG ceramics with Yb doping were produced by tape casting followed by thermal compression of assembled tapes and sintered under high vacuum. The thermal compression of variously doped tape cast layers is a very promising method because it allows a high precision and good control over dopant distribution in the sintered material. After sintering, the distribution of Yb across the layers was characterized by SEM-EDX and the thickness of Yb diffusion zones between the layers with different Yb content was measured. Optical homogeneity was assessed by means of optical transmittance mapping of the samples and by 2D scanning of laser output. The effect of structured dopant distribution on laser performance was measured in quasi-CW and CW regime with different duty factors. Slope efficiency values higher than 50% were measured both in quasi-CW and in CW lasing conditions. The results are in good agreement with previously calculated predictions, confirming the beneficial effect of structured doping on laser performances and enlightening the impact of the residual scattering losses. Compared to other processing methods, such as the pressing of granulated powders, tape casting followed by thermal compression leads to straight and narrow interfaces between layers with different composition and allows to build structures composed of extremely thin layers with defined dopant content.

The Development of Erosion and Impact Resistant Turbine Airfoil Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

2007-01-01

Thermal barrier coatings are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments and extend component lifetimes. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Advanced erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the doped thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion and impact damage mechanisms of the thermal barrier coatings will also be discussed.

COMPARISON OF THERMAL EFFICIENCIES FOR A MERCURY-STEAM BINARY VAPOR CYCLE AND THE RANKINE CYCLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prem, L.L.

1961-05-19

A comparison of the thermal efficiencies of the mercurysteam binary vapor cycle and the Rankine cycle shows that the binary cycle efficiency is greater. A temperatureentropy diagram and a schematic layout of the binary cycle are presented for clarity. (N.W.R.)

Dynamic Geospatial Modeling of the Building Stock to Project Urban Energy Demand.

PubMed

Breunig, Hanna Marie; Huntington, Tyler; Jin, Ling; Robinson, Alastair; Scown, Corinne Donahue

2018-06-26

In the United States, buildings account for more than 40 percent of total energy consumption, and the evolution of the urban form will impact the effectiveness of strategies to reduce energy use and mitigate emissions. This paper presents a broadly applicable approach for modeling future commercial, residential, and industrial floorspace, thermal consumption (heating and cooling), and associated GHG emissions at the tax assessor land parcel level. The approach accounts for changing building standards and retrofitting, climate change, and trends in housing and industry. We demonstrate the automated workflow for California, and project building stock, thermal energy consumption, and associated GHG emissions out to 2050. Our results suggest that if buildings in California have long lifespans, and minimal energy efficiency improvements compared to building codes reflective of 2008, then the state will face a 20% or higher increase in thermal energy consumption by 2050. Baseline annual GHG emissions associated with thermal energy consumption in the modeled building stock in 2016 is 34% below 1990 levels (110 Mt CO2eq/y).While the 2020 targets for the reduction of GHG emissions set by the California Senate Bill 350 have already been met, none of our scenarios achieve >80% reduction from 1990 levels by 2050, despite assuming an 86% reduction in electricity carbon intensity in our "Low Carbon" scenario. The results highlight the challenge California faces in meeting its new energy efficiency targets unless the State's building stock undergoes timely and strategic turnover, paired with deep retrofitting of existing buildings and natural gas equipment.

Thermally efficient and highly scalable In2Se3 nanowire phase change memory

NASA Astrophysics Data System (ADS)

Jin, Bo; Kang, Daegun; Kim, Jungsik; Meyyappan, M.; Lee, Jeong-Soo

2013-04-01

The electrical characteristics of nonvolatile In2Se3 nanowire phase change memory are reported. Size-dependent memory switching behavior was observed in nanowires of varying diameters and the reduction in set/reset threshold voltage was as low as 3.45 V/6.25 V for a 60 nm nanowire, which is promising for highly scalable nanowire memory applications. Also, size-dependent thermal resistance of In2Se3 nanowire memory cells was estimated with values as high as 5.86×1013 and 1.04×106 K/W for a 60 nm nanowire memory cell in amorphous and crystalline phases, respectively. Such high thermal resistances are beneficial for improvement of thermal efficiency and thus reduction in programming power consumption based on Fourier's law. The evaluation of thermal resistance provides an avenue to develop thermally efficient memory cell architecture.

Thermal Coatings Seminar Series Training Part 1: Properties of Thermal Coatings

NASA Technical Reports Server (NTRS)

Triolo, Jack

2015-01-01

This course will present an overview of a variety of thermal coatings-related topics, including: coating types and availability, thermal properties measurements, environmental testing (lab and in-flight), environmental impacts, contamination impacts, contamination liabilities, determination of BOLEOL values, and what does specularity mean to the thermal engineer.

Effect of multi-tank thermal energy storage, recuperator effectiveness, and solar receiver conductance on the performance of a concentrated solar supercritical CO 2-based power plant operating under different seasonal conditions

DOE PAGES

Osorio, Julian D.; Hovsapian, Rob; Ordonez, Juan C.

2016-09-13

Renewable energy technologies based on solar energy concentration are important alternatives to supply the rising energy demand in the world and to mitigate the negative environmental impact caused by the extensive use of fossil-fuels. In this work, a thermodynamic model based on energy and exergy analyses is developed to study the transient behavior of a Concentrated Solar Power (CSP) supercritical CO2 plant operating under different seasonal conditions. The system analyzed is composed of a central receiver, hot and cold thermal energy storage units, a heat exchanger, a recuperator, and three-stage compression and expansion subsystems with intercoolers between compressors and reheatersmore » between turbines, respectively. From the exergy analysis, the recuperator, the hot thermal energy storage, and the solar receiver were identified as the main sources for exergy destruction with more than 70% of the total lost work in the plant. These components offer an important potential to improve the system’s performance via design optimization. With reference parameters, the system reaches efficiencies of about 18.5%. These efficiencies are increased with a combination of improved design parameters, reaching values of between 24.1% and 26.2%, depending on the season, which are relatively good for CSP plants.« less

Effect of multi-tank thermal energy storage, recuperator effectiveness, and solar receiver conductance on the performance of a concentrated solar supercritical CO 2-based power plant operating under different seasonal conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osorio, Julian D.; Hovsapian, Rob; Ordonez, Juan C.

Renewable energy technologies based on solar energy concentration are important alternatives to supply the rising energy demand in the world and to mitigate the negative environmental impact caused by the extensive use of fossil-fuels. In this work, a thermodynamic model based on energy and exergy analyses is developed to study the transient behavior of a Concentrated Solar Power (CSP) supercritical CO2 plant operating under different seasonal conditions. The system analyzed is composed of a central receiver, hot and cold thermal energy storage units, a heat exchanger, a recuperator, and three-stage compression and expansion subsystems with intercoolers between compressors and reheatersmore » between turbines, respectively. From the exergy analysis, the recuperator, the hot thermal energy storage, and the solar receiver were identified as the main sources for exergy destruction with more than 70% of the total lost work in the plant. These components offer an important potential to improve the system’s performance via design optimization. With reference parameters, the system reaches efficiencies of about 18.5%. These efficiencies are increased with a combination of improved design parameters, reaching values of between 24.1% and 26.2%, depending on the season, which are relatively good for CSP plants.« less

FY2014 Propulsion Materials R&D Annual Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The Propulsion Materials Program actively supports the energy security and reduction of greenhouse emissions goals of VTO by investigating and identifying the materials properties that are most essential for continued development of cost-effective, highly efficient, and environmentally friendly next-generation heavy and light-duty powertrains. The technical approaches available to enhance propulsion systems focus on improvements in both vehicle efficiency and fuel substitution, both of which must overcome the performance limitations of the materials currently in use. Propulsion Materials Program activities work with national laboratories, industry experts, and VTO powertrain systems (e.g., Advanced Combustion Engines [ACE], Advanced Power Electronics and Electrical Machinesmore » [APEEM], and fuels) teams to develop strategies that overcome materials limitations in future powertrain performance. The technical maturity of the portfolio of funded projects ranges from basic science to subsystem prototype validation. Projects within a Propulsion Materials Program activity address materials concerns that directly impact critical technology barriers within each of the above programs, including barriers that impact fuel efficiency, thermal management, emissions reduction, improved reliability, and reduced manufacturing costs. The program engages only the barriers that result from material property limitations and represent fundamental, high-risk materials issues.« less

FY2015 Propulsion Materials Annual Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

None, None

The Propulsion Materials Program actively supports the energy security and reduction of greenhouse emissions goals of VTO by investigating and identifying the materials properties that are most essential for continued development of cost-effective, highly efficient, and environmentally friendly next-generation heavy and light-duty powertrains. The technical approaches available to enhance propulsion systems focus on improvements in both vehicle efficiency and fuel substitution, both of which must overcome the performance limitations of the materials currently in use. Propulsion Materials Program activities work with national laboratories, industry experts, and VTO powertrain systems (e.g., Advanced Combustion Engines [ACE], Advanced Power Electronics and Electrical Machinesmore » [APEEM], and fuels) teams to develop strategies that overcome materials limitations in future powertrain performance. The technical maturity of the portfolio of funded projects ranges from basic science to subsystem prototype validation. Projects within a Propulsion Materials Program activity address materials concerns that directly impact critical technology barriers within each of the above programs, including barriers that impact fuel efficiency, thermal management, emissions reduction, improved reliability, and reduced manufacturing costs. The program engages only the barriers that result from material property limitations and represent fundamental, high-risk materials issues.« less

Hot kinetic model as a guide to improve organic photovoltaic materials.

PubMed

Sosorev, Andrey Yu; Godovsky, Dmitry Yu; Paraschuk, Dmitry Yu

2018-01-31

The modeling of organic solar cells (OSCs) can provide a roadmap for their further improvement. Many OSC models have been proposed in recent years; however, the impact of the key intermediates from photons to electricity-hot charge-transfer (CT) states-on the OSC efficiency is highly ambiguous. In this study, we suggest an analytical kinetic model for OSC that considers a two-step charge generation via hot CT states. This hot kinetic model allowed us to evaluate the impact of different material parameters on the OSC performance: the driving force for charge separation, optical bandgap, charge mobility, geminate recombination rate, thermalization rate, average electron-hole separation distance in the CT state, dielectric permittivity, reorganization energy and charge delocalization. In contrast to a widespread trend of lowering the material bandgap, the model predicts that this approach is only efficient along with improvement of the other material properties. The most promising ways to increase the OSC performance are decreasing the reorganization energy, i.e., an energy change accompanying CT from the donor molecule to the acceptor, increasing the dielectric permittivity and charge delocalization. The model suggests that there are no fundamental limitations that can prevent achieving the OSC efficiency above 20%.

Impact of cell design and operating conditions on the performances of SOFC fuelled with methane

NASA Astrophysics Data System (ADS)

Laurencin, J.; Lefebvre-Joud, F.; Delette, G.

An in-house-model has been developed to study the thermal and electrochemical behaviour of a planar SOFC fed directly with methane and incorporated in a boiler. The usual Ni-YSZ cermet has been considered for the anode material. It has been found that methane reforming into hydrogen occurs only at the cell inlet in a limited depth within the anode. A sensitivity analysis has allowed establishing that anode thicknesses higher than ∼400-500 μm are required to achieve both the optimal methane conversion and electrochemical performances. The direct internal reforming (DIR) mechanisms and the impact of operating conditions on temperature gradients and SOFC electrical efficiencies have been investigated considering the anode supported cell configuration. It has been shown that the temperature gradient is minimised in the autothermal mode of cell operation. Thermal equilibrium in the stack has been found to be strongly dependent on radiative heat losses with the stack envelope. Electrochemical performance and cell temperature maps have been established as a function of methane flow rates and cell voltages.

Influential factors on thermoacoustic efficiency of multilayered graphene film loudspeakers for optimal design

NASA Astrophysics Data System (ADS)

Xing, Qianhe; Li, Shuang; Fan, Xueliang; Bian, Anhua; Cao, Shi-Jie; Li, Cheng

2017-09-01

Graphene thermoacoustic loudspeakers, composed of a graphene film on a substrate, generate sound with heat. Improving thermoacoustic efficiency of graphene speakers is a goal for optimal design. In this work, we first modified the existing TA model with respect to small thermal wavelengths, and then built an acoustic platform for model validation. Additionally, sensitivity analyses for influential factors on thermoacoustic efficiency were performed, including the thickness of multilayered graphene films, the thermal effusivity of substrates, and the characteristics of inserted gases. The higher sensitivity coefficients result in the stronger effects on thermoacoustic efficiency. We find that the thickness (5 nm-15 nm) of graphene films plays a trivial role in efficiency, resulting in the sensitivity coefficient less than 0.02. The substrate thermal effusivity, however, has significant effects on efficiency, with the sensitivity coefficient around 1.7. Moreover, substrates with a lower thermal effusivity show better acoustic performances. For influences of ambient gases, the sensitivity coefficients of density ρg, thermal conductivity κg, and specific heat cp,g are 2.7, 0.98, and 0.8, respectively. Furthermore, large magnitudes of both ρg and κg lead to a higher efficiency and the sound pressure level generated by graphene films is approximately proportional to the inverse of cp,g. These findings can refer to the optimal design for graphene thermoacoustic speakers.

Thermally stable, highly efficient, ultraflexible organic photovoltaics

PubMed Central

Xu, Xiaomin; Fukuda, Kenjiro; Karki, Akchheta; Park, Sungjun; Kimura, Hiroki; Jinno, Hiroaki; Watanabe, Nobuhiro; Yamamoto, Shuhei; Shimomura, Satoru; Kitazawa, Daisuke; Yokota, Tomoyuki; Umezu, Shinjiro; Nguyen, Thuc-Quyen; Someya, Takao

2018-01-01

Flexible photovoltaics with extreme mechanical compliance present appealing possibilities to power Internet of Things (IoT) sensors and wearable electronic devices. Although improvement in thermal stability is essential, simultaneous achievement of high power conversion efficiency (PCE) and thermal stability in flexible organic photovoltaics (OPVs) remains challenging due to the difficulties in maintaining an optimal microstructure of the active layer under thermal stress. The insufficient thermal capability of a plastic substrate and the environmental influences cannot be fully expelled by ultrathin barrier coatings. Here, we have successfully fabricated ultraflexible OPVs with initial efficiencies of up to 10% that can endure temperatures of over 100 °C, maintaining 80% of the initial efficiency under accelerated testing conditions for over 500 hours in air. Particularly, we introduce a low-bandgap poly(benzodithiophene-cothieno[3,4-b]thiophene) (PBDTTT) donor polymer that forms a sturdy microstructure when blended with a fullerene acceptor. We demonstrate a feasible way to adhere ultraflexible OPVs onto textiles through a hot-melt process without causing severe performance degradation. PMID:29666257

Prediction and design of efficient exciplex emitters for high-efficiency, thermally activated delayed-fluorescence organic light-emitting diodes.

PubMed

Liu, Xiao-Ke; Chen, Zhan; Zheng, Cai-Jun; Liu, Chuan-Lin; Lee, Chun-Sing; Li, Fan; Ou, Xue-Mei; Zhang, Xiao-Hong

2015-04-08

High-efficiency, thermally activated delayed-fluorescence organic light-emitting diodes based on exciplex emitters are demonstrated. The best device, based on a TAPC:DPTPCz emitter, shows a high external quantum efficiency of 15.4%. Strategies for predicting and designing efficient exciplex emitters are also provided. This approach allow prediction and design of efficient exciplex emitters for achieving high-efficiency organic light-emitting diodes, for future use in displays and lighting applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A hot-electron thermophotonic solar cell demonstrated by thermal up-conversion of sub-bandgap photons

PubMed Central

Farrell, Daniel J.; Sodabanlu, Hassanet; Wang, Yunpeng; Sugiyama, Masakazu; Okada, Yoshitaka

2015-01-01

The direct conversion of solar energy to electricity can be broadly separated into two main categories: photovoltaics and thermal photovoltaics, where the former utilizes gradients in electrical potential and the latter thermal gradients. Conventional thermal photovoltaics has a high theoretical efficiency limit (84%) but in practice cannot be easily miniaturized and is limited by the engineering challenges of sustaining large (>1,000 K) temperature gradients. Here we show a hot-carrier-based thermophotonic solar cell, which combines the compact nature of photovoltaic devices with the potential to reach the high-efficiency regime of thermal photovoltaics. In the device, a thermal gradient of 500 K is established by hot electrons, under Stokes illumination, rather than by raising the temperature of the material itself. Under anti-Stokes (sub-bandgap) illumination we observe a thermal gradient of ∼20 K, which is maintained by steady-state Auger heating of carriers and corresponds to a internal thermal up-conversion efficiency of 30% between the collector and solar cell. PMID:26541415

Thermal analysis elements of liquefied gas storage tanks

NASA Astrophysics Data System (ADS)

Yanvarev, I. A.; Krupnikov, A. V.

2017-08-01

Tasks of solving energy and resource efficient usage problems, both for oil producing companies and for companies extracting and transporting natural gas, are associated with liquefied petroleum gas technology development. Improving the operation efficiency of liquefied products storages provides for conducting structural, functional, and appropriate thermal analysis of tank parks in the general case as complex dynamic thermal systems.

The thermal consequences of river-level variations in an urban groundwater body highly affected by groundwater heat pumps.

PubMed

García-Gil, Alejandro; Vázquez-Suñe, Enric; Schneider, Eduardo Garrido; Sánchez-Navarro, José Ángel; Mateo-Lázaro, Jesús

2014-07-01

The extensive implementation of ground source heat pumps in urban aquifers is an important issue related to groundwater quality and the future economic feasibility of existent geothermal installations. Although many cities are in the immediate vicinity of large rivers, little is known about the thermal river-groundwater interaction at a kilometric-scale. The aim of this work is to evaluate the thermal impact of river water recharges induced by flood events into an urban alluvial aquifer anthropogenically influenced by geothermal exploitations. The present thermal state of an urban aquifer at a regional scale, including 27 groundwater heat pump installations, has been evaluated. The thermal impacts of these installations in the aquifer together with the thermal impacts from "cold" winter floods have also been spatially and temporally evaluated to ensure better geothermal management of the aquifer. The results showed a variable direct thermal impact from 0 to 6 °C depending on the groundwater-surface water interaction along the river trajectory. The thermal plumes far away from the riverbed also present minor indirect thermal impacts due to hydraulic gradient variations. Copyright © 2014 Elsevier B.V. All rights reserved.

Flashlamp radiation recycling for enhanced pumping efficiency and reduced thermal load

DOEpatents

Jancaitis, Kenneth S.; Powell, Howard T.

1989-01-01

A method for recycling laser flashlamp radiation in selected wavelength ranges to decrease thermal loading of the solid state laser matrix while substantially maintaining the pumping efficiency of the flashlamp.

Numerical Study of a 10 K Two Stage Pulse Tube Cryocooler with Precooling Inside the Pulse Tube

NASA Astrophysics Data System (ADS)

Xiaomin, Pang; Xiaotao, Wang; Wei, Dai; Jianyin, Hu; Ercang, Luo

2017-02-01

High efficiency cryocoolers working below 10 K have many applications such as cryo-pump, superconductor cooling and cryogenic electronics. This paper presents a thermally coupled two-stage pulse tube cryocooler system and its numeric analysis. The simulation results indicate that temperature distribution in the pulse tube has a significant impact on the system performance. So a precooling heat exchanger is put inside the second stage pulse tube for a deep investigation on its influence on the system performance. The influences of operating parameters such as precooling temperature, location of the precooling heat exchanger are discussed. Comparison of energy losses apparently show the advantages of the configuration which leads to an improvement on the efficiency. Finally, the cryocooler is predicted to be able to reach a relative Carnot efficiency of 10.7% at 10 K temperature.

An Efficient Algorithm for Server Thermal Fault Diagnosis Based on Infrared Image

NASA Astrophysics Data System (ADS)

Liu, Hang; Xie, Ting; Ran, Jian; Gao, Shan

2017-10-01

It is essential for a data center to maintain server security and stability. Long-time overload operation or high room temperature may cause service disruption even a server crash, which would result in great economic loss for business. Currently, the methods to avoid server outages are monitoring and forecasting. Thermal camera can provide fine texture information for monitoring and intelligent thermal management in large data center. This paper presents an efficient method for server thermal fault monitoring and diagnosis based on infrared image. Initially thermal distribution of server is standardized and the interest regions of the image are segmented manually. Then the texture feature, Hu moments feature as well as modified entropy feature are extracted from the segmented regions. These characteristics are applied to analyze and classify thermal faults, and then make efficient energy-saving thermal management decisions such as job migration. For the larger feature space, the principal component analysis is employed to reduce the feature dimensions, and guarantee high processing speed without losing the fault feature information. Finally, different feature vectors are taken as input for SVM training, and do the thermal fault diagnosis after getting the optimized SVM classifier. This method supports suggestions for optimizing data center management, it can improve air conditioning efficiency and reduce the energy consumption of the data center. The experimental results show that the maximum detection accuracy is 81.5%.

A new concept of hybrid photovoltaic thermal (PVT) collector with natural circulation

NASA Astrophysics Data System (ADS)

Lu, Longsheng; Wang, Xiaowu; Wang, Shuai; Liu, Xiaokang

2017-07-01

Hybrid photovoltaic thermal (PVT) technology refers to the integration of a photovoltaic module into a conventional solar thermal collector. Generally, the traditional design of a PVT collector has solar cells fixed on the top surface of an absorber in a flat-plate solar thermal collector. In this work, we presented a new concept of water-based PVT collector in which solar cells were directly placed on the bottom surface of its glass cover. A dynamic numerical model of this new PVT is developed and validated by experimental tests. With numerical analysis, it is found that at same covering factor, the electricity conversion efficiency of solar cells of the new PVT exceed that of the traditional PVT by nearly 10% while its thermal efficiency is approximately 30% lower than that of the traditional PVT. When the covering factor changes from 0.05 to 1, the thermal efficiency of the new PVT drops nearly 70%. The thermal efficiency of both the new PVT and the traditional PVT rise up as the water mass in tank increases. Meanwhile, the final water temperature in tank of the traditional PVT collector declines more than 17 °C, whereas that of the new PVT declines less than 6 °C, when the water mass increases from 100 to 300 kg.

Enhanced phonon scattering by nanovoids in high thermoelectric power factor polysilicon thin films

NASA Astrophysics Data System (ADS)

Dunham, Marc T.; Lorenzi, Bruno; Andrews, Sean C.; Sood, Aditya; Asheghi, Mehdi; Narducci, Dario; Goodson, Kenneth E.

2016-12-01

The ability to tune the thermal conductivity of semiconductor materials is of interest for thermoelectric applications, in particular, for doped silicon, which can be readily integrated in electronic microstructures and have a high thermoelectric power factor. Here, we examine the impact of nanovoids on the thermal conductivity of highly doped, high-power factor polysilicon thin films using time-domain thermoreflectance. Voids are formed through ion implantation and annealing, evolving from many small (˜4 nm mean diameter) voids after 500 °C anneal to fewer, larger (˜29 nm mean diameter) voids with a constant total volume fraction after staged thermal annealing to 1000 °C. The thermal conductivity is reduced to 65% of the non-implanted reference film conductivity after implantation and 500 °C anneal, increasing with anneal temperature until fully restored after 800 °C anneal. The void size distributions are determined experimentally using small-angle and wide-angle X-ray scattering. While we believe multiple physical mechanisms are at play, we are able to corroborate the positive correlation between measurements of thermal conductivity and void size with Monte Carlo calculations and a scattering probability based on Matthiessen's rule. The data suggest an opportunity for thermal conductivity suppression combined with the high power factor for increased material zT and efficiency of nanostructured polysilicon as a thermoelectric material.

A Decision Support System for Mitigating Stream Temperature Impacts in the Sacramento River

NASA Astrophysics Data System (ADS)

Caldwell, R. J.; Zagona, E. A.; Rajagopalan, B.

2014-12-01

Increasing demands on the limited and variable water supply across the West can result in insufficient streamflow to sustain healthy fish habitat. We develop an integrated decision support system (DSS) for modeling and mitigating stream temperature impacts and demonstrate it on the Sacramento River system in California. Water management in the Sacramento River is a complex task with a diverse set of demands ranging from municipal supply to mitigation of fisheries impacts due to high water temperatures. Current operations utilize the temperature control device (TCD) structure at Shasta Dam to mitigate these high water temperatures downstream at designated compliance points. The TCD structure at Shasta Dam offers a rather unique opportunity to mitigate water temperature violations through adjustments to both release volume and temperature. In this study, we develop and evaluate a model-based DSS with four broad components that are coupled to produce the decision tool for stream temperature mitigation: (i) a suite of statistical models for modeling stream temperature attributes using hydrology and climate variables of critical importance to fish habitat; (ii) a reservoir thermal model for modeling the thermal structure and, consequently, the water release temperature, (iii) a stochastic weather generator to simulate weather sequences consistent with seasonal outlooks; and, (iv) a set of decision rules (i.e., 'rubric') for reservoir water releases in response to outputs from the above components. Multiple options for modifying releases at Shasta Dam were considered in the DSS, including mixing water from multiple elevations through the TCD and using different acceptable levels of risk. The DSS also incorporates forecast uncertainties and reservoir operating options to help mitigate stream temperature impacts for fish habitat, while efficiently using the reservoir water supply and cold pool storage. The use of these coupled tools in simulating impacts of future climate on stream temperature variability is also demonstrated. Results indicate that the DSS could substantially reduce the number of violations of thermal criteria, while ensuring maintenance of the cold pool storage throughout the summer.

Thermally enhanced photoluminescence for energy harvesting: from fundamentals to engineering optimization

NASA Astrophysics Data System (ADS)

Kruger, N.; Kurtulik, M.; Revivo, N.; Manor, A.; Sabapathy, T.; Rotschild, C.

2018-05-01

The radiance of thermal emission, as described by Planck’s law, depends only on the emissivity and temperature of a body, and increases monotonically with the temperature rise at any emitted wavelength. Non-thermal radiation, such as photoluminescence (PL), is a fundamental light–matter interaction that conventionally involves the absorption of an energetic photon, thermalization, and the emission of a redshifted photon. Such a quantum process is governed by rate conservation, which is contingent on the quantum efficiency. In the past, the role of rate conservation for significant thermal excitation had not been studied. Recently, we presented the theory and an experimental demonstration that showed, in contrast to thermal emission, that the PL rate is conserved when the temperature increases while each photon is blueshifted. A further rise in temperature leads to an abrupt transition to thermal emission where the photon rate increases sharply. We also demonstrated how such thermally enhanced PL (TEPL) generates orders of magnitude more energetic photons than thermal emission at similar temperatures. These findings show that TEPL is an ideal optical heat pump that can harvest thermal losses in photovoltaics with a maximal theoretical efficiency of 70%, and practical concepts potentially reaching 45% efficiency. Here we move the TEPL concept onto the engineering level and present Cr:Nd:YAG as device grade PL material, absorbing solar radiation up to 1 μm wavelength and heated by thermalization of energetic photons. Its blueshifted emission, which can match GaAs cells, is 20% of the absorbed power. Based on a detailed balance simulation, such a material coupled with proper photonic management can reach 34% power conversion efficiency. These results raise confidence in the potential of TEPL becoming a disruptive technology in photovoltaics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreno, Gilbert; Bennion, Kevin

This project will develop thermal management strategies to enable efficient and high-temperature wide-bandgap (WBG)-based power electronic systems (e.g., emerging inverter and DC-DC converter designs). The use of WBG-based devices in automotive power electronics will improve efficiency and increase driving range in electric-drive vehicles; however, the implementation of this technology is limited, in part, due to thermal issues. This project will develop system-level thermal models to determine the thermal limitations of current automotive power modules under elevated device temperature conditions. Additionally, novel cooling concepts and material selection will be evaluated to enable high-temperature silicon and WBG devices in power electronics components.more » WBG devices (silicon carbide [SiC], gallium nitride [GaN]) promise to increase efficiency, but will be driven as hard as possible. This creates challenges for thermal management and reliability.« less

Thermally Activated Delayed Fluorescence in Polymers: A New Route toward Highly Efficient Solution Processable OLEDs.

PubMed

Nikolaenko, Andrey E; Cass, Michael; Bourcet, Florence; Mohamad, David; Roberts, Matthew

2015-11-25

Efficient intermonomer thermally activated delayed fluorescence is demonstrated for the first time, opening a new route to achieving high-efficiency solution processable polymer light-emitting device materials. External quantum efficiency (EQE) of up to 10% is achieved in a simple fully solution-processed device structure, and routes for further EQE improvement identified. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study on key technologies of optimization of big data for thermal power plant performance

NASA Astrophysics Data System (ADS)

Mao, Mingyang; Xiao, Hong

2018-06-01

Thermal power generation accounts for 70% of China's power generation, the pollutants accounted for 40% of the same kind of emissions, thermal power efficiency optimization needs to monitor and understand the whole process of coal combustion and pollutant migration, power system performance data show explosive growth trend, The purpose is to study the integration of numerical simulation of big data technology, the development of thermal power plant efficiency data optimization platform and nitrogen oxide emission reduction system for the thermal power plant to improve efficiency, energy saving and emission reduction to provide reliable technical support. The method is big data technology represented by "multi-source heterogeneous data integration", "large data distributed storage" and "high-performance real-time and off-line computing", can greatly enhance the energy consumption capacity of thermal power plants and the level of intelligent decision-making, and then use the data mining algorithm to establish the boiler combustion mathematical model, mining power plant boiler efficiency data, combined with numerical simulation technology to find the boiler combustion and pollutant generation rules and combustion parameters of boiler combustion and pollutant generation Influence. The result is to optimize the boiler combustion parameters, which can achieve energy saving.

Improvement of thermal management in the composite Yb:YAG/YAG thin-disk laser

NASA Astrophysics Data System (ADS)

Kuznetsov, I. I.; Mukhin, I. B.; Palashov, O. V.

2016-04-01

To improve the thermal management in the composite Yb:YAG/YAG thin-disk laser a new design of laser head is developed. Thermal-induced phase distortions, small signal gain and lasing in the upgraded laser head are investigated and compared with previously published results. A substantial decrease of the thermal lens optical power and phase aberrations and increase of the laser slope efficiency are observed. A continuous-wave laser with 440 W average power and 44% slope efficiency is constructed.

Design of energy efficient building with radiant slab cooling

NASA Astrophysics Data System (ADS)

Tian, Zhen

2007-12-01

Air-conditioning comprises a substantial fraction of commercial building energy use because of compressor-driven refrigeration and fan-driven air circulation. Core regions of large buildings require year-round cooling due to heat gains from people, lights and equipment. Negative environmental impacts include CO2 emissions from electric generation and leakage of ozone-depleting refrigerants. Some argue that radiant cooling simultaneously improves building efficiency and occupant thermal comfort, and that current thermal comfort models fail to reflect occupant experience with radiant thermal control systems. There is little field evidence to test these claims. The University of Calgary's Information and Communications Technology (ICT) Building, is a pioneering radiant slab cooling installation in North America. Thermal comfort and energy performance were evaluated. Measurements included: (1) heating and cooling energy use, (2) electrical energy use for lighting and equipment, and (3) indoor temperatures. Accuracy of a whole building energy simulation model was evaluated with these data. Simulation was then used to compare the radiant slab design with a conventional (variable air volume) system. The radiant system energy performance was found to be poorer mainly due to: (1) simultaneous cooling by the slab and heating by other systems, (2) omission of low-exergy (e.g., groundwater) cooling possible with the high cooling water temperatures possible with radiant slabs and (3) excessive solar gain and conductive heat loss due to the wall and fenestration design. Occupant thermal comfort was evaluated through questionnaires and concurrent measurement of workstation comfort parameters. Analysis of 116 sets of data from 82 occupants showed that occupant assessment was consistent with estimates based on current thermal comfort models. The main thermal comfort improvements were reductions in (1) local discomfort from draft and (2) vertical air temperature stratification. The analysis showed that integrated architectural and mechanical design is required to achieve the potential benefits of radiant slab cooling, including: (1) reduction of peak solar gain via windows through (a) avoiding large window-to-wall ratios and/or (b) exterior shading of windows, (2) use of low-quality cooling sources such as cooling towers and ground water, especially in cold, dry climates, and (3) coordination of system control to avoid simultaneous heating and cooling.

Estimation of Thermoelectric Generator Performance by Finite Element Modeling

NASA Astrophysics Data System (ADS)

Ziolkowski, P.; Poinas, P.; Leszczynski, J.; Karpinski, G.; Müller, E.

2010-09-01

Prediction of thermoelectric performance parameters by numerical methods is an inherent part of thermoelectric generator (TEG) development and allows for time- and cost-saving assessment of material combinations and variations of crucial design parameters (e.g., shape, pellet length, and thermal coupling). Considering the complexity of a TEG system and its numerous affecting factors, the clarity and the flexibility of a mathematical treatment comes to the fore. Comfortable tools are provided by commercial finite element modeling (FEM) software offering powerful geometry interfaces, mesh generators, solvers, and postprocessing options. We describe the level of development and the simulation results of a three dimensional (3D) TEG FEM. Using ANSYS 11.0, we implemented and simulated a TEG module geometry under various conditions. Comparative analytical one dimensional (1D) results and a direct comparison with inhouse-developed TEG simulation software show the consistency of results. Several pellet aspect ratios and contact property configurations (thermal/electrical interface resistance) were evaluated for their impact on the TEG performance as well as parasitic effects such as convection, radiation, and conductive heat bypass. The scenarios considered revealed the highest efficiency decay for convectionally loaded setups (up to 4.8%pts), followed by the impacts of contact resistances (up to 4.8%pts), by radiation (up to 0.56%pts), and by thermal conduction of a solid filling material within the voids of the module construction (up to 0.14%pts).

Repeatability of gradient ultrahigh pressure liquid chromatography-tandem mass spectrometry methods in instrument-controlled thermal environments.

PubMed

Grinias, James P; Wong, Jenny-Marie T; Kennedy, Robert T

2016-08-26

The impact of viscous friction on eluent temperature and column efficiency in liquid chromatography is of renewed interest as the need for pressures exceeding 1000bar to use with columns packed with sub-2μm particles has grown. One way the development of axial and radial temperature gradients that arise due to viscous friction can be affected is by the thermal environment the column is placed in. In this study, a new column oven integrated into an ultrahigh pressure liquid chromatograph that enables both still-air and forced-air operating modes is investigated to find the magnitude of the effect of the axial thermal gradient that forms in 2.1×100mm columns packed with sub-2μm particles in these modes. Temperature increases of nearly 30K were observed when the generated power of the column exceeded 25W/m. The impact of the heating due to viscous friction on the repeatability of peak capacity, elution time, and peak area ratio to an internal standard for a gradient UHPLC-MS/MS method to analyze neurotransmitters was found to be limited. This result indicates that high speed UHPLC-MS/MS gradient methods under conditions of high viscous friction may be possible without the negative effects typically observed with isocratic separations under similar conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Tighten water-chemistry control after boiler layup

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brestel, L.

1994-01-01

The potential for internal deposition and corrosion can affect boiler reliability by reducing thermal efficiency, tube integrity, and the time between chemical cleanings. While chemical control specifications for normal operation have been developed by consensus of manufacturers and industry, their impact on shutdowns, layups, and startups is not always appreciated. The discussion of chemical-control options applies to boiler systems operating in the medium- and high-pressure ranges. Identification and correction of root causes underlying the chemistry problems encountered and application of the principles involved should result in shorter startup times, improved control over phosphate hideout, and reduced need for chemical cleaning.more » Each of these has a significant cost impact; together, they are the true measure of a successful chemistry-control program.« less

Adaptive Development

NASA Technical Reports Server (NTRS)

2005-01-01

The goal of this research is to develop and demonstrate innovative adaptive seal technologies that can lead to dramatic improvements in engine performance, life, range, and emissions, and enhance operability for next generation gas turbine engines. This work is concentrated on the development of self-adaptive clearance control systems for gas turbine engines. Researchers have targeted the high-pressure turbine (HPT) blade tip seal location for following reasons: Current active clearance control (ACC) systems (e.g., thermal case-cooling schemes) cannot respond to blade tip clearance changes due to mechanical, thermal, and aerodynamic loads. As such they are prone to wear due to the required tight running clearances during operation. Blade tip seal wear (increased clearances) reduces engine efficiency, performance, and service life. Adaptive sealing technology research has inherent impact on all envisioned 21st century propulsion systems (e.g. distributed vectored, hybrid and electric drive propulsion concepts).

Pore structure modification of diatomite as sulfuric acid catalyst support by high energy electron beam irradiation and hydrothermal treatment

NASA Astrophysics Data System (ADS)

Li, Chong; Zhang, Guilong; Wang, Min; Chen, Jianfeng; Cai, Dongqing; Wu, Zhengyan

2014-08-01

High energy electron beam (HEEB) irradiation and hydrothermal treatment (HT), were applied in order to remove the impurities and enlarge the pore size of diatomite, making diatomite more suitable to be a catalyst support. The results demonstrated that, through thermal, charge, impact and etching effects, HEEB irradiation could make the impurities in the pores of diatomite loose and remove some of them. Then HT could remove rest of them from the pores and contribute significantly to the modification of the pore size distribution of diatomite due to thermal expansion, water swelling and thermolysis effects. Moreover, the pore structure modification improved the properties (BET (Brunauer-Emmett-Teller) specific surface area, bulk density and pore volume) of diatomite and the catalytic efficiency of the catalyst prepared from the treated diatomite.

Improving urban district heating systems and assessing the efficiency of the energy usage therein

NASA Astrophysics Data System (ADS)

Orlov, M. E.; Sharapov, V. I.

2017-11-01

The report describes issues in connection with improving urban district heating systems from combined heat power plants (CHPs), to propose the ways for improving the reliability and the efficiency of the energy usage (often referred to as “energy efficiency”) in such systems. The main direction of such urban district heating systems improvement suggests transition to combined heating systems that include structural elements of both centralized and decentralized systems. Such systems provide the basic part of thermal power via highly efficient methods for extracting thermal power plants turbines steam, while peak loads are covered by decentralized peak thermal power sources to be mounted at consumers’ locations, with the peak sources being also reserve thermal power sources. The methodology was developed for assessing energy efficiency of the combined district heating systems, implemented as a computer software product capable of comparatively calculating saving on reference fuel for the system.

Solar thermal plant impact analysis and requirements definition study

NASA Technical Reports Server (NTRS)

1982-01-01

The technology and economics of solar thermal electric systems (STES) for electric power production is discussed. The impacts of and requirements for solar thermal electric power systems were evaluated.

Diamond Thin-Film Thermionic Generator

NASA Astrophysics Data System (ADS)

Clewell, J. M.; Ordonez, C. A.; Perez, J. M.

1997-03-01

Since the eighteen-hundreds scientists have sought to develop the highest thermal efficiency in heat engines such as thermionic generators. Modern research in the emerging diamond film industry has indicated the work functions of diamond thin-films can be much less than one electron volt, compelling fresh investigation into their capacity as thermionic generators and inviting new methodology for determining that efficiency. Our objective is to predict the efficiency of a low-work-function, degenerate semiconductor (diamond film) thermionic generator operated as a heat engine between two constant-temperature thermal reservoirs. Our presentation will focus on a theoretical model which predicts the efficiency of the system by employing a Monte Carlo computational technique from which we report results for the thermal efficiency and the thermionic current densities of diamond thin-films.

Chapter 23: Combined Heat and Power Evaluation Protocol. The Uniform Methods Project: Methods for Determining Energy Efficiency Savings for Specific Measures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurnik, Charles W.; Simons, George; Barsun, Stephan

The main focus of most evaluations is to determine the energy-savings impacts of the installed measure. This protocol defines a combined heat and power (CHP) measure as a system that sequentially generates both electrical energy and useful thermal energy from one fuel source at a host customer's facility or residence. This protocol is aimed primarily at regulators and administrators of ratepayer-funded CHP programs; however, project developers may find the protocol useful to understand how CHP projects are evaluated.

Evaporative cooling by a pulsed jet spray of binary ethanol-water mixture

NASA Astrophysics Data System (ADS)

Karpov, P. N.; Nazarov, A. D.; Serov, A. F.; Terekhov, V. I.

2015-07-01

We have experimentally studied the heat transfer under conditions of pulsed multinozzle jet spray impact onto a vertical surface. The working coolant fluid was aqueous ethanol solution in a range of concentrations K 1 = 0-96%. The duration of spray pulses was τ = 2, 4, and 10 ms at a repetition frequency of 10 Hz. The maximum heat transfer coefficient was achieved at an ethanol solution concentration within 50-60%. The thermal efficiency of pulsed spray cooling grows with increasing ethanol concentration and decreasing jet spray pulse duration.

Sustainability Impact of Nanomaterial Enhanced Lithium Ion Batteries

NASA Astrophysics Data System (ADS)

Ganter, Matthew

Energy storage devices are becoming an integral part of sustainable energy technology adoption, particularly, in alternative transportation (electric vehicles) and renewable energy technologies (solar and wind which are intermittent). The most prevalent technology exhibiting near-term impact are lithium ion batteries, especially in portable consumer electronics and initial electric vehicle models like the Chevy Volt and Nissan Leaf. However, new technologies need to consider the full life-cycle impacts from material production and use phase performance to the end-of-life management (EOL). This dissertation investigates the impacts of nanomaterials in lithium ion batteries throughout the life cycle and develops strategies to improve each step in the process. The embodied energy of laser vaporization synthesis and purification of carbon nanotubes (CNTs) was calculated to determine the environmental impact of the novel nanomaterial at beginning of life. CNTs were integrated into lithium ion battery electrodes as conductive additives, current collectors, and active material supports to increase power, energy, and thermal stability in the use phase. A method was developed to uniformly distribute CNT conductive additives in composites. Cathode composites with CNT additives had significant rate improvements (3x the capacity at a 10C rate) and higher thermal stability (40% reduction in exothermic energy released upon overcharge). Similar trends were also measured with CNTs in anode composites. Advanced free-standing anodes incorporating CNTs with high capacity silicon and germanium were measured to have high capacities where surface area reduction improved coulombic efficiencies and thermal stability. A thermal stability plot was developed that compares the safety of traditional composites with free-standing electrodes, relating the results to thermal conductivity and surface area effects. The EOL management of nanomaterials in lithium ion batteries was studied and a novel recycling technique, referred to as refunctionalization , for lithium ion cathode materials was developed. Refunctionalization is the treatment of active materials in order to regain electrochemical performance at EOL which eliminates the need to recycle to the elemental level and can lead to greater environmental and economic savings. The lithium ion capacity of EOL lithium iron phosphate (LiFePO4) nanomaterial cathode was regained through chemical and electrochemical re-lithiation techniques. The embodied energy of refunctionalized LiFePO4 was calculated to be 50% less than cathode synthesized from virgin materials. Overall, these results contribute to an improved understanding of the life cycle impacts for nanomaterials in batteries. The CNT embodied energy calculation established the first life cycle inventory for laser vaporization CNTs, whereas the novel refunctionalization strategies established a new EOL pathway to recover cathodes at a higher value state than traditional recycling. At the same time, CNT enhanced battery electrodes increased power and energy in the use phase while demonstrating the unique ability to engineer electrodes to control thermal stability, which enables better performing and safer batteries.

Slotting Fins of Heat Exchangers to Provide Thermal Breaks

NASA Technical Reports Server (NTRS)

Scull, Timothy D.

2003-01-01

Heat exchangers that include slotted fins (in contradistinction to continuous fins) have been invented. The slotting of the fins provides thermal breaks that reduce thermal conduction along flow paths (longitudinal thermal conduction), which reduces heat-transfer efficiency. By increasing the ratio between transverse thermal conduction (the desired heat-transfer conduction) and longitudinal thermal conduction, slotting of the fins can be exploited to (1) increase heat-transfer efficiency (thereby reducing operating cost) for a given heat-exchanger length or to (2) reduce the length (thereby reducing the weight and/or cost) of the heat exchanger needed to obtain a given heat transfer efficiency. By reducing the length of a heat exchanger, one can reduce the pressure drop associated with the flow through it. In a case in which slotting enables the use of fins with thermal conductivity greater than could otherwise be tolerated on the basis of longitudinal thermal conduction, one can exploit the conductivity to make the fins longer (in the transverse direction) than they otherwise could be, thereby making it possible to make a heat exchanger that contains fewer channels and therefore, that weighs less, contains fewer potential leak paths, and can be constructed from fewer parts and, hence, reduced cost.

Investigation of the charge boost technology for the efficiency increase of closed sorption thermal energy storage systems

NASA Astrophysics Data System (ADS)

Rohringer, C.; Engel, G.; Köll, R.; Wagner, W.; van Helden, W.

2017-10-01

The inclusion of solar thermal energy into energy systems requires storage possibilities to overcome the gap between supply and demand. Storage of thermal energy with closed sorption thermal energy systems has the advantage of low thermal losses and high energy density. However, the efficiency of these systems needs yet to be increased to become competitive on the market. In this paper, the so-called “charge boost technology” is developed and tested via experiments as a new concept for the efficiency increase of compact thermal energy storages. The main benefit of the charge boost technology is that it can reach a defined state of charge for sorption thermal energy storages at lower temperature levels than classic pure desorption processes. Experiments are conducted to provide a proof of principle for this concept. The results show that the charge boost technology does function as predicted and is a viable option for further improvement of sorption thermal energy storages. Subsequently, a new process application is developed by the author with strong focus on the utilization of the advantages of the charge boost technology over conventional desorption processes. After completion of the conceptual design, the theoretical calculations are validated via experiments.

Advanced oxidation technology for H2S odor gas using non-thermal plasma

NASA Astrophysics Data System (ADS)

Tao, ZHU; Ruonan, WANG; Wenjing, BIAN; Yang, CHEN; Weidong, JING

2018-05-01

Non-thermal plasma technology is a new type of odor treatment processing. We deal with H2S from waste gas emission using non-thermal plasma generated by dielectric barrier discharge. On the basis of two criteria, removal efficiency and absolute removal amount, we deeply investigate the changes in electrical parameters and process parameters, and the reaction process of the influence of ozone on H2S gas removal. The experimental results show that H2S removal efficiency is proportional to the voltage, frequency, power, residence time and energy efficiency, while it is inversely proportional to the initial concentration of H2S gas, and ozone concentration. This study lays the foundations of non-thermal plasma technology for further commercial application.

Study of the thermal-optics parameters of Nd3+-doped phosphate glass as a function of temperature

NASA Astrophysics Data System (ADS)

Filho, J. C.; Pilla, V.; Messias, D. N.; Lourenço, S. A.; Silva, A. C. A.; Dantas, N. O.; Andrade, A. A.

2017-02-01

The spectroscopic properties of rare earth ions in many different hosts have been investigated, including surveys of Nd3+ in silicate, phosphate, fluorophosphates and fluoride glasses. Some of the thermal-optical properties of materials are influenced by temperature change, such as thermal diffusivity, specific heat and luminescence quantum efficiency. In this work the luminescence quantum efficiency of PANK: Nd3+, as a function of temperature (80- 480 K), was investigated using the normalized lifetime thermal lens technique. This system presents high quantum efficiency at low Nd3+ concentration and at ambient temperature, 100%, which decrease as temperature increase. Below room temperature the effects are not in accord with the maximum value of η, which must be unity.

Thermal and Electrical Recharging of Sodium/Sulfur Cells

NASA Technical Reports Server (NTRS)

Richter, Robert

1987-01-01

Efficiency as high as 60 percent achieved. Proposed thermal and electrical recharging scheme expected to increase overall energy efficiency of battery of sodium/sulfur cells (beta cells). Takes advantage of peculiarity in chemical kinetics of recharge portion of operating cycle to give thermal assist to electrically driven chemical reactions. Future application include portable power supplies and energy storage in commercial power systems during offpeak periods.

Thermal Coatings Seminar Series Training Part 2: Environmental Effects

NASA Technical Reports Server (NTRS)

Triolo, Jack

2015-01-01

This course will present an overview of a variety of thermal coatings-related topics, including: coating types and availability, thermal properties measurements, environmental testing (lab and in-flight), environmental impacts, contamination impacts, contamination liabilities, determination of BOLEOL values, and what does specularity mean to the thermal engineer.

MATLAB Simulation of Photovoltaic and Photovoltaic/Thermal Systems Performance

NASA Astrophysics Data System (ADS)

Nasir, Farah H. M.; Husaini, Yusnira

2018-03-01

The efficiency of the photovoltaic reduces when the photovoltaic cell temperature increased due to solar irradiance. One solution is come up with the cooling system photovoltaic system. This combination is forming the photovoltaic-thermal (PV/T) system. Not only will it generate electricity also heat at the same time. The aim of this research is to focus on the modeling and simulation of photovoltaic (PV) and photovoltaic-thermal (PV/T) electrical performance by using single-diode equivalent circuit model. Both PV and PV/T models are developed in Matlab/Simulink. By providing the cooling system in PV/T, the efficiency of the system can be increased by decreasing the PV cell temperature. The maximum thermal, electrical and total efficiency values of PV/T in the present research are 35.18%, 15.56% and 50.74% at solar irradiance of 400 W/m2, mass flow rate of 0.05kgs-1 and inlet temperature of 25 °C respectively has been obtained. The photovoltaic-thermal shows that the higher efficiency performance compared to the photovoltaic system.

Development and Performance of Alternative Electricity Sector Pathways Subject to Multiple Climate and Water Projections

NASA Astrophysics Data System (ADS)

Newmark, R. L.; Vorosmarty, C. J.; Miara, A.; Cohen, S.; Macknick, J.; Sun, Y.; Corsi, F.; Fekete, B. M.; Tidwell, V. C.

2017-12-01

Climate change impacts on air temperatures and water availability have the potential to alter future electricity sector investment decisions as well as the reliability and performance of the power sector. Different electricity sector configurations are more or less vulnerable to climate-induced changes. For example, once-through cooled thermal facilities are the most cost-effective and efficient technologies under cooler and wetter conditions, but can be substantially affected by and vulnerable to warmer and drier conditions. Non-thermal renewable technologies, such as PV and wind, are essentially "drought-proof" but have other integration and reliability challenges. Prior efforts have explored the impacts of climate change on electric sector development for a limited set of climate and electricity scenarios. Here, we provide a comprehensive suite of scenarios that evaluate how different electricity sector pathways could be affected by a range of climate and water resource conditions. We use four representative concentration pathway (RCP) scenarios under five global circulation models (GCM) as climate drivers to a Water Balance Model (WBM), to provide twenty separate future climate-water conditions. These climate-water conditions influence electricity sector development from present day to 2050 as determined using the Regional Energy Deployment Systems (ReEDS) model. Four unique electricity sector pathways will be considered, including business-as-usual, carbon cap, high renewable energy technology costs, and coal reliance scenarios. The combination of climate-water and electricity sector pathway scenarios leads to 80 potential future cases resulting in different national and regional electricity infrastructure configurations. The vulnerability of these configurations in relation to climate change (including in-stream thermal pollution impacts and environmental regulations) is evaluated using the Thermoelectric Power and Thermal Pollution (TP2M) model, providing quantitative estimates of the power sector's ability to meet loads, given changes in air temperature, water temperature, and water availability.

Thermal dephasing in second-harmonic generation of an amplified copper-vapor laser beam in beta barium borate.

PubMed

Prakash, Om; Dixit, Sudhir Kumar; Bhatnagar, Rajiva

2005-03-20

The conversion efficiency in second-harmonic generation of an amplified beam in a master-oscillator power amplifier copper-vapor laser (CVL) is lower than that of the oscillator beam alone. This lower efficiency is often vaguely attributed to wave-front degradation in the amplifier. We investigate the role of wave-front degradation and thermal dephasing in the second-harmonic generation of a CVL from a beta-barium borate crystal. Choosing two beams with constant intrapulse divergence, one from a generalized diffraction filtered resonator master oscillator alone and other obtained by amplifying oscillator by use of a power amplifier, we show that at low flux levels the decrease in efficiency is due to wave-front degradation. At a fundamental power above the critical power for thermal dephasing, the decrease is due to increased UV absorption and consequent thermal dephasing. Thermal dephasing is higher for the beam with the lower coherence width.

Microstructured silicon neutron detectors for security applications

NASA Astrophysics Data System (ADS)

Esteban, S.; Fleta, C.; Guardiola, C.; Jumilla, C.; Pellegrini, G.; Quirion, D.; Rodriguez, J.; Lozano, M.

2014-12-01

In this paper we present the design and performance of a perforated thermal neutron silicon detector with a 6LiF neutron converter. This device was manufactured within the REWARD project workplace whose aim is to develop and enhance technologies for the detection of nuclear and radiological materials. The sensor perforated structure results in a higher efficiency than that obtained with an equivalent planar sensor. The detectors were tested in a thermal neutron beam at the nuclear reactor at the Instituto Superior Técnico in Lisbon and the intrinsic detection efficiency for thermal neutrons and the gamma sensitivity were obtained. The Geant4 Monte Carlo code was used to simulate the experimental conditions, i.e. thermal neutron beam and the whole detector geometry. An intrinsic thermal neutron detection efficiency of 8.6%±0.4% with a discrimination setting of 450 keV was measured.

Improved finite element methodology for integrated thermal structural analysis

NASA Technical Reports Server (NTRS)

Dechaumphai, P.; Thornton, E. A.

1982-01-01

An integrated thermal-structural finite element approach for efficient coupling of thermal and structural analysis is presented. New thermal finite elements which yield exact nodal and element temperatures for one dimensional linear steady state heat transfer problems are developed. A nodeless variable formulation is used to establish improved thermal finite elements for one dimensional nonlinear transient and two dimensional linear transient heat transfer problems. The thermal finite elements provide detailed temperature distributions without using additional element nodes and permit a common discretization with lower order congruent structural finite elements. The accuracy of the integrated approach is evaluated by comparisons with analytical solutions and conventional finite element thermal structural analyses for a number of academic and more realistic problems. Results indicate that the approach provides a significant improvement in the accuracy and efficiency of thermal stress analysis for structures with complex temperature distributions.

Vertically Aligned and Interconnected SiC Nanowire Networks Leading to Significantly Enhanced Thermal Conductivity of Polymer Composites.

PubMed

Yao, Yimin; Zhu, Xiaodong; Zeng, Xiaoliang; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

2018-03-21

Efficient heat removal via thermal management materials has become one of the most critical challenges in the development of modern microelectronic devices. However, previously reported polymer composites exhibit limited enhancement of thermal conductivity, even when highly loaded with thermally conductive fillers, because of the lack of efficient heat transfer pathways. Herein, we report vertically aligned and interconnected SiC nanowire (SiCNW) networks as efficient fillers for polymer composites, achieving significantly enhanced thermal conductivity. The SiCNW networks are produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to consolidate the nanowire junctions, exhibiting a hierarchical architecture in which honeycomb-like SiCNW layers are aligned. The composite obtained by infiltrating SiCNW networks with epoxy resin, at a relatively low SiCNW loading of 2.17 vol %, represents a high through-plane thermal conductivity (1.67 W m -1 K -1 ) compared to the pure matrix, which is equivalent to a significant enhancement of 406.6% per 1 vol % loading. The orderly SiCNW network which can act as a macroscopic expressway for phonon transport is believed to be the main contributor for the excellent thermal performance. This strategy provides insights for the design of high-performance composites with potential to be used in advanced thermal management materials.

Remote sensing study of the impact of vegetation on thermal environment in different contexts

NASA Astrophysics Data System (ADS)

Xie, Qijiao; Wu, Yingjiao; Zhou, Zhixiang; Wang, Zhengxiang

2018-02-01

Satellite remote sensing technology provides informative data for detecting the land surface temperature (LST) distribution and urban heat island (UHI) effect remotely and regionally. In this study, two Landsat Thematic Mapper (TM) images acquired on September 26, 1987 and September 17, 2013 were used to derive LST and the normalized difference vegetation index (NDVI) values in Wuhan, China. The relationships between NDVI and LST were examined in different contexts, namely built-up area, farmland, grassland and forest. Results showed that negative correlations between the mean NDVI and LST were detected in all observed land covers, which meant that vegetation was efficient in decreasing surface temperatures and mitigating UHI effect. The cooling efficiency of vegetation on thermal environment varied with different contexts. As mean NDVI increased at each 0.1, the decreased LST values in built-up area, farmland, grassland and forest were 1.4 °C, 1.4 °C, 1.1 °C, 1.9 °C in 1987 and 1.4 °C, 1.7 °C, 1.3 °C, 1.8 °C in 2013, respectively. This finding encourages urban planners and greening designers to devote more efforts in protecting urban forests.

Study of design and technology factors influencing gas turbine blade cooling

NASA Astrophysics Data System (ADS)

Shevchenko, I. V.; Garanin, I. V.; Rogalev, A. N.; Kindra, V. O.; Khudyakova, V. P.

2017-11-01

The knowledge of aerodynamic and thermal parameters of turbulators used in order to design an efficient blade cooling system. However, all experimental tests of the hydraulic and thermal characteristics of the turbulators were conducted on the rectangular shape channels with a strongly defined air flow direction. The actual blades have geometry of the channels that essentially differs from the rectangular shape. Specifically, the air flow in the back cavity of a blade with one and half-pass cooling channel changes its direction throughout the feather height. In most cases the ribs and pins are made with a tilt to the channel walls, which is determined by the moving element design of a mould for the ceramic rod element fabrication. All of the factors described above may result in the blade thermohydraulic model being developed failing to fully simulate the air flow and the heat exchange processes in some sections of the cooling path. Hence, the design temperature field will differ from the temperature field of an actual blade. This article studied the numerical data of design and technology factors influencing heat transfer in the cooling channels. The results obtained showed their substantial impact on the blade cooling efficiency.

Design of a thermosyphon-based thermal valve for controlled high-temperature heat extraction

DOE PAGES

Oshman, Christopher; Hardin, Corey; Rea, Jonathan; ...

2017-01-16

Conventional concentrated solar power (CSP) is a reliable alternative energy source that uses the sun’s heat to drive a heat engine to produce electrical power. An advantage of CSP is its ability to store thermal energy for use during off-sun hours which is typically done by storing sensible heat in molten salts. Alternatively, thermal energy may be stored as latent heat in a phase-change material (PCM), which stores large quantities of thermal energy in an isothermal process. On-sun, the PCM melts, storing energy. Off-sun, the latent heat is extracted to produce dispatchable electrical power. Here, this paper presents the designmore » of a thermosyphon-based device with sodium working fluid that is able to extract heat from a source as demand requires. A prototype has been designed to transfer 37 kW of thermal energy from a 600°C molten PCM tank to an array of 9% efficient thermoelectric generators (TEGs) to produce 3 kW of usable electrical energy for 5 h. This “thermal valve” design incorporates a funnel to collect condensate and a central shut-off valve to control condensate gravity return to the evaporator. Three circumferential tubes allow vapour transport up to the condenser. Pressure and a thermal resistance models were developed to predict the performance of the thermal valve. The pressure model predicts that the thermal valve will function as designed. The thermal resistance model predicts a 5500× difference in total thermal resistance between “on” and “off” states. The evaporator and condenser walls comprise 96% of the “on” thermal resistance, while the small parasitic heat transfer in the “off” state is primarily (77%) due to radiation losses. Lastly, this simple and effective technology can have a strong impact on the feasibility, scalability, and dispatchability of CSP latent storage. In addition, other industrial and commercial applications can benefit from this thermal valve concept.« less

Design of a thermosyphon-based thermal valve for controlled high-temperature heat extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oshman, Christopher; Hardin, Corey; Rea, Jonathan

Conventional concentrated solar power (CSP) is a reliable alternative energy source that uses the sun’s heat to drive a heat engine to produce electrical power. An advantage of CSP is its ability to store thermal energy for use during off-sun hours which is typically done by storing sensible heat in molten salts. Alternatively, thermal energy may be stored as latent heat in a phase-change material (PCM), which stores large quantities of thermal energy in an isothermal process. On-sun, the PCM melts, storing energy. Off-sun, the latent heat is extracted to produce dispatchable electrical power. Here, this paper presents the designmore » of a thermosyphon-based device with sodium working fluid that is able to extract heat from a source as demand requires. A prototype has been designed to transfer 37 kW of thermal energy from a 600°C molten PCM tank to an array of 9% efficient thermoelectric generators (TEGs) to produce 3 kW of usable electrical energy for 5 h. This “thermal valve” design incorporates a funnel to collect condensate and a central shut-off valve to control condensate gravity return to the evaporator. Three circumferential tubes allow vapour transport up to the condenser. Pressure and a thermal resistance models were developed to predict the performance of the thermal valve. The pressure model predicts that the thermal valve will function as designed. The thermal resistance model predicts a 5500× difference in total thermal resistance between “on” and “off” states. The evaporator and condenser walls comprise 96% of the “on” thermal resistance, while the small parasitic heat transfer in the “off” state is primarily (77%) due to radiation losses. Lastly, this simple and effective technology can have a strong impact on the feasibility, scalability, and dispatchability of CSP latent storage. In addition, other industrial and commercial applications can benefit from this thermal valve concept.« less

Detection of impact damage on thermal protection systems using thin-film piezoelectric sensors for integrated structural health monitoring

NASA Astrophysics Data System (ADS)

Na, Jeong K.; Kuhr, Samuel J.; Jata, Kumar V.

2008-03-01

Thermal Protection Systems (TPS) can be subjected to impact damage during flight and/or during ground maintenance and/or repair. AFRL/RXLP is developing a reliable and robust on-board sensing/monitoring capability for next generation thermal protection systems to detect and assess impact damage. This study was focused on two classes of metallic thermal protection tiles to determine threshold for impact damage and develop sensing capability of the impacts. Sensors made of PVDF piezoelectric film were employed and tested to evaluate the detectability of impact signals and assess the onset or threshold of impact damage. Testing was performed over a range of impact energy levels, where the sensors were adhered to the back of the specimens. The PVDF signal levels were analyzed and compared to assess damage, where digital microscopy, visual inspection, and white light interferometry were used for damage verification. Based on the impact test results, an assessment of the impact damage thresholds for each type of metallic TPS system was made.

Could thermal sensitivity of mitochondria determine species distribution in a changing climate?

PubMed

Iftikar, Fathima I; MacDonald, Julia R; Baker, Daniel W; Renshaw, Gillian M C; Hickey, Anthony J R

2014-07-01

For many aquatic species, the upper thermal limit (Tmax) and the heart failure temperature (THF) are only a few degrees away from the species' current environmental temperatures. While the mechanisms mediating temperature-induced heart failure (HF) remain unresolved, energy flow and/or oxygen supply disruptions to cardiac mitochondria may be impacted by heat stress. Recent work using a New Zealand wrasse (Notolabrus celidotus) found that ATP synthesis capacity of cardiac mitochondria collapses prior to T(HF). However, whether this effect is limited to one species from one thermal habitat remains unknown. The present study confirmed that cardiac mitochondrial dysfunction contributes to heat stress-induced HF in two additional wrasses that occupy cold temperate (Notolabrus fucicola) and tropical (Thalassoma lunare) habitats. With exposure to heat stress, T. lunare had the least scope to maintain heart function with increasing temperature. Heat-exposed fish of all species showed elevated plasma succinate, and the heart mitochondria from the cold temperate N. fucicola showed decreased phosphorylation efficiencies (depressed respiratory control ratio, RCR), cytochrome c oxidase (CCO) flux and electron transport system (ETS) flux. In situ assays conducted across a range of temperatures using naive tissues showed depressed complex II (CII) and CCO capacity, limited ETS reserve capacities and lowered efficiencies of pyruvate uptake in T. lunare and N. celidotus. Notably, alterations of mitochondrial function were detectable at saturating oxygen levels, indicating that cardiac mitochondrial insufficiency can occur prior to HF without oxygen limitation. Our data support the view that species distribution may be related to the thermal limits of mitochondrial stability and function, which will be important as oceans continue to warm. © 2014. Published by The Company of Biologists Ltd.

Interlayer electron-hole pair multiplication by hot carriers in atomic layer semiconductor heterostructures

NASA Astrophysics Data System (ADS)

Barati, Fatemeh; Grossnickle, Max; Su, Shanshan; Lake, Roger; Aji, Vivek; Gabor, Nathaniel

Two-dimensional heterostructures composed of atomically thin transition metal dichalcogenides provide the opportunity to design novel devices for the study of electron-hole pair multiplication. We report on highly efficient multiplication of interlayer electron-hole pairs at the interface of a tungsten diselenide / molybdenum diselenide heterostructure. Electronic transport measurements of the interlayer current-voltage characteristics indicate that layer-indirect electron-hole pairs are generated by hot electron impact excitation. Our findings, which demonstrate an efficient energy relaxation pathway that competes with electron thermalization losses, make 2D semiconductor heterostructures viable for a new class of hot-carrier energy harvesting devices that exploit layer-indirect electron-hole excitations. SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Air Force Office of Scientific Research.

Impact of physics and technology innovations on compact tokamak fusion pilot plants

NASA Astrophysics Data System (ADS)

Menard, Jonathan

2016-10-01

For magnetic fusion to be economically attractive and have near-term impact on the world energy scene it is important to focus on key physics and technology innovations that could enable net electricity production at reduced size and cost. The tokamak is presently closest to achieving the fusion conditions necessary for net electricity at acceptable device size, although sustaining high-performance scenarios free of disruptions remains a significant challenge for the tokamak approach. Previous pilot plant studies have shown that electricity gain is proportional to the product of the fusion gain, blanket thermal conversion efficiency, and auxiliary heating wall-plug efficiency. In this work, the impact of several innovations is assessed with respect to maximizing fusion gain. At fixed bootstrap current fraction, fusion gain varies approximately as the square of the confinement multiplier, normalized beta, and major radius, and varies as the toroidal field and elongation both to the third power. For example, REBCO high-temperature superconductors (HTS) offer the potential to operate at much higher toroidal field than present fusion magnets, but HTS cables are also beginning to access winding pack current densities up to an order of magnitude higher than present technology, and smaller HTS TF magnet sizes make low-aspect-ratio HTS tokamaks potentially attractive by leveraging naturally higher normalized beta and elongation. Further, advances in kinetic stabilization and feedback control of resistive wall modes could also enable significant increases in normalized beta and fusion gain. Significant reductions in pilot plant size will also likely require increased plasma energy confinement, and control of turbulence and/or low edge recycling (for example using lithium walls) would have major impact on fusion gain. Reduced device size could also exacerbate divertor heat loads, and the impact of novel divertor solutions on pilot plant configurations is addressed. For missions including tritium breeding, high-thermal-efficiency liquid metal breeding blankets are attractive, and novel immersion blankets offer the potential for simplified fabrication and maintenance and reduced cost. Lastly, the optimal aspect ratio for a tokamak pilot plant is likely a function of the device mission and associated cost, with low aspect ratio favored for minimizing TF magnet mass and higher aspect ratio favored for minimizing blanket mass. The interplay between a range of physics and technology innovations for enabling compact pilot plants will be described. This work was supported by U.S. DOE Contract Number DE-AC02-09CH11466.

Effective Energy Simulation and Optimal Design of Side-lit Buildings with Venetian Blinds

NASA Astrophysics Data System (ADS)

Cheng, Tian

Venetian blinds are popularly used in buildings to control the amount of incoming daylight for improving visual comfort and reducing heat gains in air-conditioning systems. Studies have shown that the proper design and operation of window systems could result in significant energy savings in both lighting and cooling. However, there is no convenient computer tool that allows effective and efficient optimization of the envelope of side-lit buildings with blinds now. Three computer tools, Adeline, DOE2 and EnergyPlus widely used for the above-mentioned purpose have been experimentally examined in this study. Results indicate that the two former tools give unacceptable accuracy due to unrealistic assumptions adopted while the last one may generate large errors in certain conditions. Moreover, current computer tools have to conduct hourly energy simulations, which are not necessary for life-cycle energy analysis and optimal design, to provide annual cooling loads. This is not computationally efficient, particularly not suitable for optimal designing a building at initial stage because the impacts of many design variations and optional features have to be evaluated. A methodology is therefore developed for efficient and effective thermal and daylighting simulations and optimal design of buildings with blinds. Based on geometric optics and radiosity method, a mathematical model is developed to reasonably simulate the daylighting behaviors of venetian blinds. Indoor illuminance at any reference point can be directly and efficiently computed. They have been validated with both experiments and simulations with Radiance. Validation results show that indoor illuminances computed by the new models agree well with the measured data, and the accuracy provided by them is equivalent to that of Radiance. The computational efficiency of the new models is much higher than that of Radiance as well as EnergyPlus. Two new methods are developed for the thermal simulation of buildings. A fast Fourier transform (FFT) method is presented to avoid the root-searching process in the inverse Laplace transform of multilayered walls. Generalized explicit FFT formulae for calculating the discrete Fourier transform (DFT) are developed for the first time. They can largely facilitate the implementation of FFT. The new method also provides a basis for generating the symbolic response factors. Validation simulations show that it can generate the response factors as accurate as the analytical solutions. The second method is for direct estimation of annual or seasonal cooling loads without the need for tedious hourly energy simulations. It is validated by hourly simulation results with DOE2. Then symbolic long-term cooling load can be created by combining the two methods with thermal network analysis. The symbolic long-term cooling load can keep the design parameters of interest as symbols, which is particularly useful for the optimal design and sensitivity analysis. The methodology is applied to an office building in Hong Kong for the optimal design of building envelope. Design variables such as window-to-wall ratio, building orientation, and glazing optical and thermal properties are included in the study. Results show that the selected design values could significantly impact the energy performance of windows, and the optimal design of side-lit buildings could greatly enhance energy savings. The application example also demonstrates that the developed methodology significantly facilitates the optimal building design and sensitivity analysis, and leads to high computational efficiency.

Thermal Conductivity and Erosion Durability of Composite Two-Phase Air Plasma Sprayed Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Schmitt, Michael P.; Rai, Amarendra K.; Zhu, Dongming; Dorfman, Mitchell R.; Wolfe, Douglas E.

2015-01-01

To enhance efficiency of gas turbines, new thermal barrier coatings (TBCs) must be designed which improve upon the thermal stability limit of 7 wt% yttria stabilized zirconia (7YSZ), approximately 1200 C. This tenant has led to the development of new TBC materials and microstructures capable of improved high temperature performance. This study focused on increasing the erosion durability of cubic zirconia based TBCs, traditionally less durable than the metastable t' zirconia based TBCs. Composite TBC microstructures composed of a low thermal conductivity/high temperature stable cubic Low-k matrix phase and a durable t' Low-k secondary phase were deposited via APS. Monolithic coatings composed of cubic Low-k and t' Low-k were also deposited, in addition to a 7YSZ benchmark. The thermal conductivity and erosion durability were then measured and it was found that both of the Low-k materials have significantly reduced thermal conductivities, with monolithic t' Low-k and cubic Low-k improving upon 7YSZ by approximately 13 and approximately 25%, respectively. The 40 wt% t' Low-k composite (40 wt% t' Low-k - 60 wt% cubic Low-k) showed a approximately 22% reduction in thermal conductivity over 7YSZ, indicating even at high levels, the t' Low-k secondary phase had a minimal impact on thermal in the composite coating. It was observed that a mere 20 wt% t' Low-k phase addition can reduce the erosion of a cubic Low-k matrix phase composite coating by over 37%. Various mixing rules were then investigated to assess this non-linear composite behavior and suggestions were made to further improve erosion durability.

Predictive Optimal Control of Active and Passive Building Thermal Storage Inventory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gregor P. Henze; Moncef Krarti

2005-09-30

Cooling of commercial buildings contributes significantly to the peak demand placed on an electrical utility grid. Time-of-use electricity rates encourage shifting of electrical loads to off-peak periods at night and weekends. Buildings can respond to these pricing signals by shifting cooling-related thermal loads either by precooling the building's massive structure or the use of active thermal energy storage systems such as ice storage. While these two thermal batteries have been engaged separately in the past, this project investigated the merits of harnessing both storage media concurrently in the context of predictive optimal control. To pursue the analysis, modeling, and simulationmore » research of Phase 1, two separate simulation environments were developed. Based on the new dynamic building simulation program EnergyPlus, a utility rate module, two thermal energy storage models were added. Also, a sequential optimization approach to the cost minimization problem using direct search, gradient-based, and dynamic programming methods was incorporated. The objective function was the total utility bill including the cost of reheat and a time-of-use electricity rate either with or without demand charges. An alternative simulation environment based on TRNSYS and Matlab was developed to allow for comparison and cross-validation with EnergyPlus. The initial evaluation of the theoretical potential of the combined optimal control assumed perfect weather prediction and match between the building model and the actual building counterpart. The analysis showed that the combined utilization leads to cost savings that is significantly greater than either storage but less than the sum of the individual savings. The findings reveal that the cooling-related on-peak electrical demand of commercial buildings can be considerably reduced. A subsequent analysis of the impact of forecasting uncertainty in the required short-term weather forecasts determined that it takes only very simple short-term prediction models to realize almost all of the theoretical potential of this control strategy. Further work evaluated the impact of modeling accuracy on the model-based closed-loop predictive optimal controller to minimize utility cost. The following guidelines have been derived: For an internal heat gain dominated commercial building, reasonable geometry simplifications are acceptable without a loss of cost savings potential. In fact, zoning simplification may improve optimizer performance and save computation time. The mass of the internal structure did not show a strong effect on the optimization. Building construction characteristics were found to impact building passive thermal storage capacity. It is thus advisable to make sure the construction material is well modeled. Zone temperature setpoint profiles and TES performance are strongly affected by mismatches in internal heat gains, especially when they are underestimated. Since they are a key factor in determining the building cooling load, efforts should be made to keep the internal gain mismatch as small as possible. Efficiencies of the building energy systems affect both zone temperature setpoints and active TES operation because of the coupling of the base chiller for building precooling and the icemaking TES chiller. Relative efficiencies of the base and TES chillers will determine the balance of operation of the two chillers. The impact of mismatch in this category may be significant. Next, a parametric analysis was conducted to assess the effects of building mass, utility rate, building location and season, thermal comfort, central plant capacities, and an economizer on the cost saving performance of optimal control for active and passive building thermal storage inventory. The key findings are: (1) Heavy-mass buildings, strong-incentive time-of-use electrical utility rates, and large on-peak cooling loads will likely lead to attractive savings resulting from optimal combined thermal storage control. (2) By using economizer to take advantage of the cool fresh air during the night, the building electrical cost can be reduced by using less mechanical cooling. (3) Larger base chiller and active thermal storage capacities have the potential of shifting more cooling loads to off-peak hours and thus higher savings can be achieved. (4) Optimal combined thermal storage control with a thermal comfort penalty included in the objective function can improve the thermal comfort levels of building occupants when compared to the non-optimized base case. Lab testing conducted in the Larson HVAC Laboratory during Phase 2 showed that the EnergyPlus-based simulation was a surprisingly accurate prediction of the experiment. Therefore, actual savings of building energy costs can be expected by applying optimal controls from simulation results.« less

A Study of the Effects of Altitude on Thermal Ice Protection System Performance

NASA Technical Reports Server (NTRS)

Addy, Gene; Oleskiw, Myron; Broeren, Andy P.; Orchard, David

2013-01-01

Thermal ice protection systems use heat energy to prevent a dangerous buildup of ice on an aircraft. As aircraft become more efficient, less heat energy is available to operate a thermal ice protections system. This requires that thermal ice protection systems be designed to more exacting standards so as to more efficiently prevent a dangerous ice buildup without adversely affecting aircraft safety. While the effects of altitude have always beeing taked into account in the design of thermal ice protection systems, a better understanding of these effects is needed so as to enable more exact design, testing, and evaluation of these systems.

The Effect of Core Configuration on Thermal Barrier Thermal Performance

NASA Technical Reports Server (NTRS)

DeMange, Jeffrey J.; Bott, Robert H.; Druesedow, Anne S.

2015-01-01

Thermal barriers and seals are integral components in the thermal protection systems (TPS) of nearly all aerospace vehicles. They are used to minimize heat transfer through interfaces and gaps and protect underlying temperature-sensitive components. The core insulation has a significant impact on both the thermal and mechanical properties of compliant thermal barriers. Proper selection of an appropriate core configuration to mitigate conductive, convective and radiative heat transfer through the thermal barrier is challenging. Additionally, optimization of the thermal barrier for thermal performance may have counteracting effects on mechanical performance. Experimental evaluations have been conducted to better understand the effect of insulation density on permeability and leakage performance, which can significantly impact the resistance to convective heat transfer. The effect of core density on mechanical performance was also previously investigated and will be reviewed. Simple thermal models were also developed to determine the impact of various core parameters on downstream temperatures. An extended understanding of these factors can improve the ability to design and implement these critical TPS components.

Refractive Secondary Concentrators for Solar Thermal Applications

NASA Technical Reports Server (NTRS)

Wong, Wayne A.; Macosko, Robert P.

1999-01-01

The NASA Glenn Research Center is developing technologies that utilize solar energy for various space applications including electrical power conversion, thermal propulsion, and furnaces. Common to all of these applications is the need for highly efficient, solar concentration systems. An effort is underway to develop the innovative single crystal refractive secondary concentrator, which uses refraction and total internal reflection to efficiently concentrate and direct solar energy. The refractive secondary offers very high throughput efficiencies (greater than 90%), and when used in combination with advanced primary concentrators, enables very high concentration ratios (10,0(X) to 1) and very high temperatures (greater than 2000 K). Presented is an overview of the refractive secondary concentrator development effort at the NASA Glenn Research Center, including optical design and analysis techniques, thermal modeling capabilities, crystal materials characterization testing, optical coatings evaluation, and component testing. Also presented is a discussion of potential future activity and technical issues yet to be resolved. Much of the work performed to date has been in support of the NASA Marshall Space Flight Center's Solar Thermal Propulsion Program. The many benefits of a refractive secondary concentrator that enable efficient, high temperature thermal propulsion system designs, apply equally well to other solar applications including furnaces and power generation systems such as solar dynamics, concentrated thermal photovoltaics, and thermionics.

Incorporating Water Boiling in the Numerical Modelling of Thermal Remediation by Electrical Resistance Heating

NASA Astrophysics Data System (ADS)

Molnar, I. L.; Krol, M.; Mumford, K. G.

2017-12-01

Developing numerical models for subsurface thermal remediation techniques - such as Electrical Resistive Heating (ERH) - that include multiphase processes such as in-situ water boiling, gas production and recovery has remained a significant challenge. These subsurface gas generation and recovery processes are driven by physical phenomena such as discrete and unstable gas (bubble) flow as well as water-gas phase mass transfer rates during bubble flow. Traditional approaches to multiphase flow modeling soil remain unable to accurately describe these phenomena. However, it has been demonstrated that Macroscopic Invasion Percolation (MIP) can successfully simulate discrete and unstable gas transport1. This has lead to the development of a coupled Electro Thermal-MIP Model2 (ET-MIP) capable of simulating multiple key processes in the thermal remediation and gas recovery process including: electrical heating of soil and groundwater, water flow, geological heterogeneity, heating-induced buoyant flow, water boiling, gas bubble generation and mobilization, contaminant mass transport and removal, and additional mechanisms such as bubble collapse in cooler regions. This study presents the first rigorous validation of a coupled ET-MIP model against two-dimensional water boiling and water/NAPL co-boiling experiments3. Once validated, the model was used to explore the impact of water and co-boiling events and subsequent gas generation and mobilization on ERH's ability to 1) generate, expand and mobilize gas at boiling and NAPL co-boiling temperatures, 2) efficiently strip contaminants from soil during both boiling and co-boiling. In addition, a quantification of the energy losses arising from steam generation during subsurface water boiling was examined with respect to its impact on the efficacy of thermal remediation. While this study specifically targets ERH, the study's focus on examining the fundamental mechanisms driving thermal remediation (e.g., water boiling) renders these results applicable to a wide range of thermal and gas-based remediation techniques. 1. Mumford, K. G., et al. (2010), Adv. Water Resour. 2010, 33 (4), 504-513. 2. Krol, M. M., et al. (2011), Adv. Water Resour. 2011, 34 (4), 537-549. 3. Hegele, P. R. and Mumford, K. G. Journal of Contaminant Hydrology 2014, 165, 24-36.

Pressure and current effects on the thermal efficiency of an MPD arc used as a plasma source

NASA Technical Reports Server (NTRS)

Pivirotto, T. J.

1972-01-01

Measurements of arc voltage and energy loss to the cooled electrodes of a magnetoplasmadynamic (MPD) arc, operating without an applied magnetic field, were made at chamber pressures of 26 to 950 torr, argon mass flow rates of 0.08 to 44 g/s and current of 200 to 2000 A. The resulting arc thermal efficiency varied from 22% at a chamber pressure of 26 torr to 88% at 950 torr. Thermal efficiency was only weakly dependent on arc current. It is concluded that the MPD arc operating without an applied magnetic field and at higher pressure than normally used in thruster applications is a reliable and efficient steady-state plasma source.

High-performance radial AMTEC cell design for ultra-high-power solar AMTEC systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hendricks, T.J.; Huang, C.

1999-07-01

Alkali Metal Thermal to Electric Conversion (AMTEC) technology is rapidly maturing for potential application in ultra-high-power solar AMTEC systems required by potential future US Air Force (USAF) spacecraft missions in medium-earth and geosynchronous orbits (MEO and GEO). Solar thermal AMTEC power systems potentially have several important advantages over current solar photovoltaic power systems in ultra-high-power spacecraft applications for USAF MEO and GEO missions. This work presents key aspects of radial AMTEC cell design to achieve high cell performance in solar AMTEC systems delivering larger than 50 kW(e) to support high power USAF missions. These missions typically require AMTEC cell conversionmore » efficiency larger than 25%. A sophisticated design parameter methodology is described and demonstrated which establishes optimum design parameters in any radial cell design to satisfy high-power mission requirements. Specific relationships, which are distinct functions of cell temperatures and pressures, define critical dependencies between key cell design parameters, particularly the impact of parasitic thermal losses on Beta Alumina Solid Electrolyte (BASE) area requirements, voltage, number of BASE tubes, and system power production for both maximum power-per-BASE-area and optimum efficiency conditions. Finally, some high-level system tradeoffs are demonstrated using the design parameter methodology to establish high-power radial cell design requirements and philosophy. The discussion highlights how to incorporate this methodology with sophisticated SINDA/FLUINT AMTEC cell modeling capabilities to determine optimum radial AMTEC cell designs.« less

Micro rectennas: Brownian ratchets for thermal-energy harvesting

NASA Astrophysics Data System (ADS)

Pan, Y.; Powell, C. V.; Song, A. M.; Balocco, C.

2014-12-01

We experimentally demonstrated the operation of a rectenna for harvesting thermal (blackbody) radiation and converting it into dc electric power. The device integrates an ultrafast rectifier, the self-switching nanodiode, with a wideband log-periodic spiral microantenna. The radiation from the thermal source drives the rectenna out of thermal equilibrium, permitting the rectification of the excess thermal fluctuations from the antenna. The power conversion efficiency increases with the source temperatures up to 0.02% at 973 K. The low efficiency is attributed mainly to the impedance mismatch between antenna and rectifier, and partially to the large field of view of the antenna. Our device not only opens a potential solution for harvesting thermal energy but also provides a platform for experimenting with Brownian ratchets.

Comparing stream-specific to generalized temperature models to guide salmonid management in a changing climate

USGS Publications Warehouse

Andrew K. Carlson,; William W. Taylor,; Hartikainen, Kelsey M.; Dana M. Infante,; Beard, Douglas; Lynch, Abigail

2017-01-01

Global climate change is predicted to increase air and stream temperatures and alter thermal habitat suitability for growth and survival of coldwater fishes, including brook charr (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss). In a changing climate, accurate stream temperature modeling is increasingly important for sustainable salmonid management throughout the world. However, finite resource availability (e.g. funding, personnel) drives a tradeoff between thermal model accuracy and efficiency (i.e. cost-effective applicability at management-relevant spatial extents). Using different projected climate change scenarios, we compared the accuracy and efficiency of stream-specific and generalized (i.e. region-specific) temperature models for coldwater salmonids within and outside the State of Michigan, USA, a region with long-term stream temperature data and productive coldwater fisheries. Projected stream temperature warming between 2016 and 2056 ranged from 0.1 to 3.8 °C in groundwater-dominated streams and 0.2–6.8 °C in surface-runoff dominated systems in the State of Michigan. Despite their generally lower accuracy in predicting exact stream temperatures, generalized models accurately projected salmonid thermal habitat suitability in 82% of groundwater-dominated streams, including those with brook charr (80% accuracy), brown trout (89% accuracy), and rainbow trout (75% accuracy). In contrast, generalized models predicted thermal habitat suitability in runoff-dominated streams with much lower accuracy (54%). These results suggest that, amidst climate change and constraints in resource availability, generalized models are appropriate to forecast thermal conditions in groundwater-dominated streams within and outside Michigan and inform regional-level salmonid management strategies that are practical for coldwater fisheries managers, policy makers, and the public. We recommend fisheries professionals reserve resource-intensive stream-specific models for runoff-dominated systems containing high-priority fisheries resources (e.g. trophy individuals, endangered species) that will be directly impacted by projected stream warming.

The effect of multispectral image fusion enhancement on human efficiency.

PubMed

Bittner, Jennifer L; Schill, M Trent; Mohd-Zaid, Fairul; Blaha, Leslie M

2017-01-01

The visual system can be highly influenced by changes to visual presentation. Thus, numerous techniques have been developed to augment imagery in an attempt to improve human perception. The current paper examines the potential impact of one such enhancement, multispectral image fusion, where imagery captured in varying spectral bands (e.g., visible, thermal, night vision) is algorithmically combined to produce an output to strengthen visual perception. We employ ideal observer analysis over a series of experimental conditions to (1) establish a framework for testing the impact of image fusion over the varying aspects surrounding its implementation (e.g., stimulus content, task) and (2) examine the effectiveness of fusion on human information processing efficiency in a basic application. We used a set of rotated Landolt C images captured with a number of individual sensor cameras and combined across seven traditional fusion algorithms (e.g., Laplacian pyramid, principal component analysis, averaging) in a 1-of-8 orientation task. We found that, contrary to the idea of fused imagery always producing a greater impact on perception, single-band imagery can be just as influential. Additionally, efficiency data were shown to fluctuate based on sensor combination instead of fusion algorithm, suggesting the need for examining multiple factors to determine the success of image fusion. Our use of ideal observer analysis, a popular technique from the vision sciences, provides not only a standard for testing fusion in direct relation to the visual system but also allows for comparable examination of fusion across its associated problem space of application.

Technique for Configuring an Actively Cooled Thermal Shield in a Flight System

NASA Technical Reports Server (NTRS)

Barkfknecht, Peter; Mustafi, Shuvo

2011-01-01

Broad area cooling shields are a mass-efficient alternative to conductively cooled thermal radiation shielding. The shield would actively intercept a large portion of incident thermal radiation and transport the heat away using cryogenic helium gas. The design concept consists of a conductive and conformable surface that maximizes heat transfer and formability. Broad Area Cooled (BAC) shields could potentially provide considerable mass savings for spaceflight applications by eliminating the need for a rigid thermal radiation shield for cryogen tanks. The BAC consists of a network of capillary tubes that are thermally connected to a conductive shield material. Chilled helium gas is circulated through the network and transports unwanted heat away from the cryogen tanks. The cryogenic helium gas is pumped and chilled simultaneously using a specialized pulse-tube cryocooler, which further improves the mass efficiency of the system. By reducing the thermal environment temperature from 300 to 100 K, the radiative heat load on a cryogen tank could be reduced by an order of magnitude. For a cryogenic liquid propellant scenario of oxygen and hydrogen, the boiloff of hydrogen would be significantly reduced and completely eliminated for oxygen. A major challenge in implementing this technology on large tanks is that the BAC system must be easily scalable from lab demonstrations to full-scale missions. Also, the BAC shield must be conformable to complex shapes like spheres without losing the ability to maintain constant temperature throughout. The initial design maximizes thermal conductivity between the capillary tube and the conductive radiation shielding by using thin, corrugated aluminum foil with the tube running transverse to the folds. This configuration has the added benefit of enabling the foil to stretch and contract longitudinally. This allows the BAC to conform to the complex curvature of a cryogen tank, which is key to its success. To demonstrate a BAC shield system with minimal impact to current cryogen tank designs, the shielding must be applied after the final assembly of the tank and supporting structure. One method is to pre-fabricate the shield in long strips. A spool of corrugated aluminum foil with a thermally sunk aluminum capillary running through the center could then be simply wound around the cryogen tanks and encapsulated within the multi-layer insulation (MLI) blanket. Then, on orbit, the BAC would intercept thermal radiation coming in through the MLI and transport it away from the cryogen tanks. An optimization of the design could be done to take into account mass savings from thinner MLI blankets, eliminating solid thermal shields, and ultimately, a reduction in the required cryogen tank size.

Process Parameters for Successful Synthesis of Carbon Nanotubes by Chemical Vapor Deposition: Implications for Chemical Mechanisms and Life-cycle Assessment

NASA Astrophysics Data System (ADS)

Xue, Ke

Manufacturing of carbon nanotubes (CNTs) via chemical vapor deposition (CVD) calls for thermal treatment associated with gas-phase rearrangement and catalyst deposition to achieve high cost efficiency and limited influence on environmental impact. Taking advantage of higher degree of structure control and economical efficiency, catalytic chemical vapor deposition (CCVD) has currently become the most prevailing synthesis approach for the synthesis of large-scale pure CNTs in past years. Because the synthesis process of CNTs dominates the potential ecotoxic impacts, materials consumption, energy consumption and greenhouse gas emissions should be further limited to efficiently reduce life cycle ecotoxicity of carbon naotubes. However, efforts to reduce energy and material requirements in synthesis of CNTs by CCVD are hindered by a lack of mechanistic understanding. In this thesis, the effect of operating parameters, especially the temperature, carbon source concentration, and residence time on the synthesis were studied to improve the production efficiency in a different angle. Thus, implications on the choice of operating parameters could be provided to help the synthesis of carbon nanotubes. Here, we investigated the typical operating parameters in conditions that have yielded successful CNT production in the published academic literature of over seventy articles. The data were filtered by quality of the resultant product and deemed either "successful" or "unsuccessful" according to the authors. Furthermore, growth rate data were tabulated and used as performance metric for the process whenever possible. The data provided us an opportunity to prompt possible and common methods for practioners in the synthesis of CNTs and motivate routes to achieve energy and material minimization. The statistical analysis revealed that methane and ethylene often rely on thermal conversion process to form direct carbon precursor; further, methane and ethylene could not be the direct CNT precursors by themselves. Acetylene does not show an additional energy demand or thermal conversion in the synthesis, and it could be the direct CNT precursors by itself; or at least, it would be most easily to get access to carbon nanotube growth while minimizing synthesis temperature. In detail, methane employs more energy demand (Tavg=883°C) than ethylene (Tavg=766°C), which in turn demands more energy than acetylene (Tavg=710°C) to successfully synthesize carbon nanotubes. The distinction in energy demand could be the result of kinetic energy requirements by the thermal conversion process of methane and ethylene to form direct CNT precursors, and methane employs the highest activation demand among three hydrocarbons. Thus, these results support the hypothesis that methane and ethylene could be thermally converted to form acetylene before CNT incorporation. In addition, methane and ethylene show the demand for hydrogen in thermal conversion process before CNT incorporation; whereas, hydrogen does not contribute to the synthesis via acetylene before CNT incorporation, except the reduction of catalyst. At relatively low hydrogen concentration, this work suggests that hydrogen prompts growth of carbon nanotubes via methane and ethylene, probably by reducing the catalysts or participating thermal reactions. In addition, "polymerization-like formation mechanism" could be supported by the higher growth rate of CNTs via ethylene than acetylene. There could be an optimum residence time to maintain a relatively higher growth rate. At too low residence time, carbon source could not be accumulated, causing a waste of material; while too high residence time may cause the limitation of carbon source supplement and accumulation of byproducts. At last, high concentration of carbon source and hydrogen could cause more energy consumption, while it helps to achieve a high growth rate, due to the more presence of direct carbon precursor.

Generation of a Parabolic Trough Collector Efficiency Curve from Separate Measurements of Outdoor Optical Efficiency and Indoor Receiver Heat Loss

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kutscher, C.; Burkholder, F.; Stynes, J. K.

2012-02-01

The thermal efficiency of a parabolic trough collector is a function of both the fraction of direct normal radiation absorbed by the receiver (the optical efficiency) and the heat lost to the environment when the receiver is at operating temperature. The thermal efficiency can be determined by testing the collector under actual operating conditions or by separately measuring these two components. This paper describes how outdoor measurement of the optical efficiency is combined with laboratory measurements of receiver heat loss to obtain the thermal efficiency curve. This paper describes this approach and also makes the case that there are advantagesmore » to plotting collector efficiency versus the difference between the operating temperature and the ambient temperature at which the receiver heat loss was measured divided by radiation to a fractional power (on the order of 1/3 but obtained via data regression) - as opposed to the difference between operating and ambient temperatures divided by the radiation. The results are shown to be robust over wide ranges of ambient temperature, sky temperature, and wind speed.« less

Photon-stimulated desorption as a substantial source of sodium in the lunar atmosphere.

PubMed

Yakshinskiy, B V; Madey, T E

1999-08-12

Mercury and the Moon both have tenuous atmospheres that contain atomic sodium and potassium. These chemicals must be continuously resupplied, as neither body can retain the atoms for more than a few hours. The mechanisms proposed to explain the resupply include sputtering of the surface by the solar wind, micrometeorite impacts, thermal desorption and photon-stimulated desorption. But there are few data and no general agreement about which processes dominate. Here we report laboratory studies of photon-stimulated desorption of sodium from surfaces that simulate lunar silicates. We find that bombardment of such surfaces at temperatures of approximately 250 K by ultraviolet photons (wavelength lambda < 300 nm) causes very efficient desorption of sodium atoms, induced by electronic excitations rather than by thermal processes or momentum transfer. The flux at the lunar surface of ultraviolet photons from the Sun is sufficient to ensure that photon-stimulated desorption of sodium contributes substantially to the Moon's atmosphere. On Mercury, solar heating of the surface implies that thermal desorption will also be an important source of atmospheric sodium.

Diamond grinding wheels production study with the use of the finite element method.

PubMed

Kundrák, J; Fedorovich, V; Markopoulos, A P; Pyzhov, I; Kryukova, N

2016-11-01

Research results on 3D modeling of the diamond grain and its bearing layer when sintering diamond grinding wheels are provided in this paper. The influence of the main characteristics of the wheel materials and the wheel production process, namely the quantity of metallic phase within diamond grain, coefficient of thermal expansion of the metallic phase, the modulus of elasticity of bond material and sintering temperature, on the internal stresses arising in grains is investigated. The results indicate that the stresses in the grains are higher in the areas around the metallic phase. Additionally, sintering temperature has the greatest impact on the stresses of the grain-metallic phase-bond system regardless of the type of the bond. Furthermore, by employing factorial design for the carried out finite element model, a mathematical model that reflects the impact of these factors on the deflected mode of the diamond grain-metallic phase-bond material system is obtained. The results of the analysis allow for the identification of optimal conditions for the efficient production of improved diamond grinding wheels. More specifically, the smallest stresses are observed when using the metal bond with modulus of elasticity 204 GPa, the quantity of metallic phase in diamond grain of not higher than 7% and coefficient of thermal expansion of 1.32 × 10 -5  1/K or lower. The results obtained from the proposed 3D model can lead to the increase in the diamond grains utilization and improve the overall efficiency of diamond grinding.

Impact of Reflow on the Output Characteristics of Piezoelectric Microelectromechanical System Devices

NASA Astrophysics Data System (ADS)

Nogami, Hirofumi; Kobayashi, Takeshi; Okada, Hironao; Masuda, Takashi; Maeda, Ryutaro; Itoh, Toshihiro

2012-09-01

An animal health monitoring system and a wireless sensor node aimed at preventing the spread of animal-transmitted diseases and improving pastoral efficiency which are especially suitable for chickens, were developed. The sensor node uses a piezoelectric microelectromechanical system (MEMS) device and an event-driven system that is activated by the movements of a chicken. The piezoelectric MEMS device has two functions: a) it measures the activity of a chicken and b) switches the micro-control unit (MCU) of the wireless sensor node from the sleep mode. The piezoelectric MEMS device is required to produce high output voltages when the chicken moves. However, after the piezoelectric MEMS device was reflowed to the wireless sensor node, the output voltages of the piezoelectric MEMS device decreased. The main reason for this might be the loss of residual polarization, which is affected by the thermal load during the reflow process. After the reflow process, we were not able to apply a voltage to the piezoelectric MEMS device; thus, the piezoelectric output voltage was not increased by repoling the piezoelectric MEMS device. To address the thermal load of the reflow process, we established a thermal poling treatment, which achieves a higher temperature than the reflow process. We found that on increasing the thermal poling temperature, the piezoelectric output voltages did not decreased low significantly. Thus, we considered that a thermal poling temperature higher than that of the reflow process prevents the piezoelectric output voltage reduction caused by the thermal load.

Geometrical effects on the concentrated behavior of heat flux in metamaterials thermal harvesting devices

NASA Astrophysics Data System (ADS)

Xu, Guoqiang; Zhang, Haochun; Xie, Ming; Jin, Yan

2017-10-01

Thermal harvesting devices based on transformation optics, which can manipulate the heat flux concentration significantly through rational arrangements of the conductivities, have attracted considerable interest owing to several great potential applications of the technique for high-efficiency thermal conversion and collection. However, quantitative studies on the geometrical effects, particularly wedge angles, on the harvesting behaviors are rare. In this paper, we adopt wedge structure-based thermal harvesting schemes, and focus on the effects of the geometrical parameters including the radii ratios and wedge angles on the harvesting performance. The temperature deformations at the boundaries of the compressional region and temperature gradients for the different schemes with varying design parameters are investigated. Moreover, a concept for temperature stabilization was derived to evaluate the fluctuation in the energy distributions. In addition, the effects of interface thermal resistances have been investigated. Considering the changes in the radii ratios and wedge angles, we proposed a modification of the harvesting efficiency to quantitatively assess the concentration performance, which was verified through random tests and previously fabricated devices. In general, this study indicates that a smaller radii ratio contributes to a better harvesting behavior, but causes larger perturbations in the thermal profiles owing to a larger heat loss. We also find that a smaller wedge angle is beneficial to ensuring a higher concentration efficiency with less energy perturbations. These findings can be used to guide the improvement of a thermal concentrator with a high efficiency in reference to its potential applications as novel heat storage, thermal sensors, solar cells, and thermoelectric devices.

Energetic Materials Center Report--Small-Scale Safety and Thermal Testing Evaluation of Butyl Nitrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, Peter C.; Reynolds, John G.

2013-04-26

Butyl Nitrate (BN) was examined by Small-Scale Safety and Thermal (SSST) Testing techniques to determine its sensitivity to impact, friction, spark and thermal exposure simulating handling and storage conditions. Under the conditions tested, the BN exhibits thermal sensitivity above 150 °C, and does not exhibit sensitive to impact, friction or spark.

Integration Research on Gas Turbine and Tunnel Kiln Combined System

NASA Astrophysics Data System (ADS)

Shi, Hefei; Ma, Liangdong; Liu, Mingsheng

2018-04-01

Through the integrated modeling of gas turbine and tunnel kiln combined system, a thermodynamic calculation method of combined system is put forward, and the combined system operation parameters are obtained. By this method, the optimization of the combined system is analyzed and the optimal configuration of the gas turbine is calculated. At the same time, the thermal efficiency of the combined system is analyzed, and the heat distribution and thermal efficiency of the system before and after the improvement are explained. Taking the 1500 kg/h ceramic production as an example, pointed out that if the tunnel kiln has a gas turbine with a power of 342 kw. The amount of electricity of the combined system that produced per unit volume of the fuel which consumes more than it used to will be 7.19 kwh, the system thermal efficiency will reach 57.49%, which higher than the individual gas turbine’s cycle thermal efficiency 20% at least.

Hierarchical thermoelectrics: crystal grain boundaries as scalable phonon scatterers

NASA Astrophysics Data System (ADS)

Selli, Daniele; Boulfelfel, Salah Eddine; Schapotschnikow, Philipp; Donadio, Davide; Leoni, Stefano

2016-02-01

Thermoelectric materials are strategically valuable for sustainable development, as they allow for the generation of electrical energy from wasted heat. In recent years several strategies have demonstrated some efficiency in improving thermoelectric properties. Dopants affect carrier concentration, while thermal conductivity can be influenced by alloying and nanostructuring. Features at the nanoscale positively contribute to scattering phonons, however those with long mean free paths remain difficult to alter. Here we use the concept of hierarchical nano-grains to demonstrate thermal conductivity reduction in rocksalt lead chalcogenides. We demonstrate that grains can be obtained by taking advantage of the reconstructions along the phase transition path that connects the rocksalt structure to its high-pressure form. Since grain features naturally change as a function of size, they impact thermal conductivity over different length scales. To understand this effect we use a combination of advanced molecular dynamics techniques to engineer grains and to evaluate thermal conductivity in PbSe. By affecting grain morphologies only, i.e. at constant chemistry, two distinct effects emerge: the lattice thermal conductivity is significantly lowered with respect to the perfect crystal, and its temperature dependence is markedly suppressed. This is due to an increased scattering of low-frequency phonons by grain boundaries over different size scales. Along this line we propose a viable process to produce hierarchical thermoelectric materials by applying pressure via a mechanical load or a shockwave as a novel paradigm for material design.

Safe atmosphere entry of an isotope heat source with a single stable trim attitude at hypersonic speeds

NASA Technical Reports Server (NTRS)

Levy, L. L., Jr.; Burns, R. K.

1972-01-01

A theoretical investigation has been made to design an isotope heat source capable of satisfying the conflicting thermal requirements of steady-state operation and atmosphere entry. The isotope heat source must transfer heat efficiently to a heat exchange during normal operation with a power system in space, and in the event of a mission abort, it must survive the thermal environment of atmosphere entry and ground impact without releasing radioactive material. A successful design requires a compatible integration of the internal components of the heat source with the external aerodynamic shape. To this end, configurational, aerodynamic, motion, and thermal analyses were coupled and iterated during atmosphere entries at suborbital through superorbital velocities at very shallow and very steep entry angles. Results indicate that both thermal requirements can be satisfied by a heat source which has a single stable aerodynamic orientation at hypersonic speeds. For such a design, the insulation material required to adequately protect the isotope fuel from entry heating need extend only half way around the fuel capsule on the aerodynamically stable (wind-ward) side of the heat source. Thus, a low-thermal-resistance, conducting heat path is provided on the opposite side of the heat source through which heat can be transferred to an adjacent heat exchanger during normal operation without exceeding specified temperature limits.

Experimental Investigations, Modeling, and Analyses of High-Temperature Devices for Space Applications. Part 2

DTIC Science & Technology

1999-01-01

AMTEC cell during operation is essential to maximize the thermal -to- electric conversion efficiency of the device. The cell efficiency , rQ, is defined...the cell current is relatively high (usually above 2 A), and we found that the former thermal model of the conical evaporator wick underpredicted... high temperature, sodium vapor environment in a typical multi-tube AMTEC cell , where thermal radiation exchange is significant, an

Evaluation of the Efficiency of Liquid Cooling Garments using a Thermal Manikin

DTIC Science & Technology

2005-05-01

temperatures. The software also calculates thermal resistances and evaporative resistances. TM tests were run dry (i.e. no sweating ) and wet (i.e...REPORT DOCUMENTATION PAGE Form ApprovedOMB No . 0704-0188 SECURITY CLASSIFICATION OF REPORT SECURITY CLASSIFICATION OF THIS PAGE SECURITY CLASSIFICATION...OF ABSTRACT 8. M05-17 1. AGENCY USE ONLY (Leave blank) 4. TITLE AND SUBTITLE EVALUATION OF THE EFFICIENCY OF LIQUID COOLING GARMENTS USING A THERMAL

Thermal-hydraulic behavior of a mixed chevron single-pass plate-and-frame heat exchanger

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manglik, R.M.; Muley, A.

1995-12-31

Effective heat exchange is very critical for improving the process efficiency and operating economy of chemical and process plants. Here, experimental friction factor and heat transfer data for single-phase water flows in a plate-and-frame heat exchanger are presented. A mixed chevron plate arrangement with {beta} = 30{degree}/60{degree} in a single-pass U-type, counterflow configuration is employed. The friction factor and heat transfer data are for isothermal flow and cooling conditions, respectively, and the flow rates correspond to transition and turbulent flow regimes (300 < Re < 6,000 and 2.4 < Pr < 4.5). Based on these data, Nusselt number and frictionmore » factor correlations for fully developed turbulent flows (Re {ge} 1,000) are presented. The results highlight the effects of {beta} on the thermal-hydraulic performance, transition to turbulent flows, and the relative impact of using symmetric or mixed chevron plate arrangements.« less

Foam Core Shielding for Spacecraft

NASA Technical Reports Server (NTRS)

Adams, Marc

2007-01-01

A foam core shield (FCS) system is now being developed to supplant multilayer insulation (MLI) systems heretofore installed on spacecraft for thermal management and protection against meteoroid impacts. A typical FCS system consists of a core sandwiched between a face sheet and a back sheet. The core can consist of any of a variety of low-to-medium-density polymeric or inorganic foams chosen to satisfy application-specific requirements regarding heat transfer and temperature. The face sheet serves to shock and thereby shatter incident meteoroids, and is coated on its outer surface to optimize its absorptance and emittance for regulation of temperature. The back sheet can be dimpled to minimize undesired thermal contact with the underlying spacecraft component and can be metallized on the surface facing the component to optimize its absorptance and emittance. The FCS systems can perform better than do MLI systems, at lower mass and lower cost and with greater volumetric efficiency.

Effects of atamp-charging coke making on strength and high temperature thermal properties of coke.

PubMed

Zhang, Yaru; Bai, Jinfeng; Xu, Jun; Zhong, Xiangyun; Zhao, Zhenning; Liu, Hongchun

2013-12-01

The stamp-charging coke making process has some advantages of improving the operation environment, decreasing fugitive emission, higher gas collection efficiency as well as less environmental pollution. This article describes the different structure strength and high temperature thermal properties of 4 different types of coke manufactured using a conventional coking process and the stamp-charging coke making process. The 4 kinds of cokes were prepared from the mixture of five feed coals blended by the petrography blending method. The results showed that the structure strength indices of coke prepared using the stamp-charging coke method increase sharply. In contrast with conventional coking process, the stamp-charging process improved the coke strength after reaction but had little impact on the coke reactivity index. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

On the Injection Molding Processing Parameters of HDPE-TiO2 Nanocomposites

PubMed Central

Mourad, Abdel-Hamid I.; Mozumder, Mohammad Sayem; Mairpady, Anusha; Pervez, Hifsa; Kannuri, Uma Maheshwara

2017-01-01

In recent years, the development and use of polymeric nanocomposites in creating advanced materials has expanded exponentially. A substantial amount of research has been done in order to design polymeric nanocomposites in a safe and efficient manner. In the present study, the impact of processing parameters, such as, barrel temperature, and residence time on the mechanical and thermal properties of high density polyethylene (HDPE)-TiO2 nanocomposites were investigated. Additionally, scanning electron microscopy and X-ray diffraction spectroscopy were used to analyze the dispersion, location, and phase morphology of TiO2 on the HDPE matrix. Mechanical tests revealed that tensile strength of the fabricated HDPE-TiO2 nanocomposites ranged between 22.53 and 26.30 MPa, while the Young’s modulus showed a consistent increase as the barrel temperature increased from 150 °C to 300 °C. Moreover, the thermal stability decreased as the barrel temperature increased. PMID:28772444

On the Injection Molding Processing Parameters of HDPE-TiO₂ Nanocomposites.

PubMed

Mourad, Abdel-Hamid I; Mozumder, Mohammad Sayem; Mairpady, Anusha; Pervez, Hifsa; Kannuri, Uma Maheshwara

2017-01-20

In recent years, the development and use of polymeric nanocomposites in creating advanced materials has expanded exponentially. A substantial amount of research has been done in order to design polymeric nanocomposites in a safe and efficient manner. In the present study, the impact of processing parameters, such as, barrel temperature, and residence time on the mechanical and thermal properties of high density polyethylene (HDPE)-TiO₂ nanocomposites were investigated. Additionally, scanning electron microscopy and X-ray diffraction spectroscopy were used to analyze the dispersion, location, and phase morphology of TiO₂ on the HDPE matrix. Mechanical tests revealed that tensile strength of the fabricated HDPE-TiO₂ nanocomposites ranged between 22.53 and 26.30 MPa, while the Young's modulus showed a consistent increase as the barrel temperature increased from 150 °C to 300 °C. Moreover, the thermal stability decreased as the barrel temperature increased.

Simulation of the Effects of Cooling Techniques on Turbine Blade Heat Transfer

NASA Astrophysics Data System (ADS)

Shaw, Vince; Fatuzzo, Marco

Increases in the performance demands of turbo machinery has stimulated the development many new technologies over the last half century. With applications that spread beyond marine, aviation, and power generation, improvements in gas turbine technologies provide a vast impact. High temperatures within the combustion chamber of the gas turbine engine are known to cause an increase in thermal efficiency and power produced by the engine. However, since operating temperatures of these engines reach above 1000 K within the turbine section, the need for advances in material science and cooling techniques to produce functioning engines under these high thermal and dynamic stresses is crucial. As with all research and development, costs related to the production of prototypes can be reduced through the use of computational simulations. By making use of Ansys Simulation Software, the effects of turbine cooling techniques were analyzed. Simulation of the Effects of Cooling Techniques on Turbine Blade Heat Transfer.

Enhanced enzymatic saccharification of pretreated biomass using glycerol thermal processing (GTP).

PubMed

Zhang, Wei; Sathitsuksanoh, Noppadon; Barone, Justin R; Renneckar, Scott

2016-01-01

Biomass was heated (200-240°C) in the presence of glycerol, for 4-12 min, under shear to disrupt the native cell wall architecture. The impact of this method, named glycerol thermal processing (GTP), on saccharification efficiency of the hardwood Liquidambar styraciflua, and a control cellulose sample was studied as a function of treatment severity. Furthermore, the enzymatic conversion of samples with varying compositions was studied after extraction of the structural polymers. Interestingly, the sweet gum processed materials crystallinity index increased by 10% of the initial value. The experiments revealed that the residual lignin was not a barrier to limiting the digestibility of cellulose after pretreatment yielding up to 70% glucose based on the starting wood material. Further xylan removal greatly improved the cellulose hydrolysis rate, converting nearly 70% of the cellulose into glucose within 24h, and reaching 78% of ultimate glucan digestibility after 72 h. Copyright © 2015 Elsevier Ltd. All rights reserved.

Air-borne shape measurement of parabolic trough collector fields

NASA Astrophysics Data System (ADS)

Prahl, Christoph; Röger, Marc; Hilgert, Christoph

2017-06-01

The optical and thermal efficiency of parabolic trough collector solar fields is dependent on the performance and assembly accuracy of its components such as the concentrator and absorber. For the purpose of optical inspection/approval, yield analysis, localization of low performing areas, and optimization of the solar field, it is essential to create a complete view of the optical properties of the field. Existing optical measurement tools are based on ground based cameras, facing restriction concerning speed, volume and automation. QFly is an airborne qualification system which provides holistic and accurate information on geometrical, optical, and thermal properties of the entire solar field. It consists of an unmanned aerial vehicle, cameras and related software for flight path planning, data acquisition and evaluation. This article presents recent advances of the QFly measurement system and proposes a methodology on holistic qualification of the complete solar field with minimum impact on plant operation.

Thermodynamic characteristics of a novel wind-solar-liquid air energy storage system

NASA Astrophysics Data System (ADS)

Ji, W.; Zhou, Y.; Sun, Y.; Zhang, W.; Pan, C. Z.; Wang, J. J.

2017-12-01

Due to the nature of fluctuation and intermittency, the utilization of wind and solar power will bring a huge impact to the power grid management. Therefore a novel hybrid wind-solar-liquid air energy storage (WS-LAES) system was proposed. In this system, wind and solar power are stored in the form of liquid air by cryogenic liquefaction technology and thermal energy by solar thermal collector, respectively. Owing to the high density of liquid air, the system has a large storage capacity and no geographic constraints. The WS-LAES system can store unstable wind and solar power for a stable output of electric energy and hot water. Moreover, a thermodynamic analysis was carried out to investigate the best system performance. The result shows that the increases of compressor adiabatic efficiency, turbine inlet pressure and inlet temperature all have a beneficial effect.

Organic geochemistry of impactites from the Haughton impact structure, Devon Island, Nunavut, Canada

NASA Astrophysics Data System (ADS)

Parnell, John; Bowden, Stephen A.; Osinski, Gordon R.; Lee, Pascal; Green, Paul; Taylor, Colin; Baron, Martin

2007-04-01

Organic matter in impactites from the 24 km wide and 39 Ma old Haughton impact structure, Canadian High Arctic, is a mixture of fossil and modern biological components. The fossil component represents a conventional oil that was generated from Lower Palaeozoic marine source material before impact and permeates bedrock dolomites. Biomarker maturity parameters record the thermal effect of the mid-Tertiary impact. Maturity-influenced sterane, rearranged hopanoid, and triaromatic steroid ratios all increase towards the centre of the impact structure, where thermal alteration was greatest. The heating was probably dominated by an impact-related hydrothermal system, as such systems last long enough for kinetically-based thermal alteration to occur. Kinetically-related biomarker data suggest that the hydrothermal heating lasted for c. 5000 years. Biomarkers are also preserved in dolomite clasts within impact melt breccia, and indicate strong thermal alteration. Modern biological contamination of the rocks is responsible for the superposition of two geochemical signatures (which could be cyanobacteria, non-marine algae, or higher plant matter) onto the fossil component, but they can be recognized and distinguished. The data show that the impact structure system holds a record of both the pre-impact organic signature and the thermal signature of the impact, and thereby indicates that organic geochemistry is a valuable tool in documenting the response of rocks to impacts.

Operational and environmental performance in China's thermal power industry: Taking an effectiveness measure as complement to an efficiency measure.

PubMed

Wang, Ke; Zhang, Jieming; Wei, Yi-Ming

2017-05-01

The trend toward a more fiercely competitive and strictly environmentally regulated electricity market in several countries, including China has led to efforts by both industry and government to develop advanced performance evaluation models that adapt to new evaluation requirements. Traditional operational and environmental efficiency measures do not fully consider the influence of market competition and environmental regulations and, thus, are not sufficient for the thermal power industry to evaluate its operational performance with respect to specific marketing goals (operational effectiveness) and its environmental performance with respect to specific emissions reduction targets (environmental effectiveness). As a complement to an operational efficiency measure, an operational effectiveness measure not only reflects the capacity of an electricity production system to increase its electricity generation through the improvement of operational efficiency, but it also reflects the system's capability to adjust its electricity generation activities to match electricity demand. In addition, as a complement to an environmental efficiency measure, an environmental effectiveness measure not only reflects the capacity of an electricity production system to decrease its pollutant emissions through the improvement of environmental efficiency, but it also reflects the system's capability to adjust its emissions abatement activities to fulfill environmental regulations. Furthermore, an environmental effectiveness measure helps the government regulator to verify the rationality of its emissions reduction targets assigned to the thermal power industry. Several newly developed effectiveness measurements based on data envelopment analysis (DEA) were utilized in this study to evaluate the operational and environmental performance of the thermal power industry in China during 2006-2013. Both efficiency and effectiveness were evaluated from the three perspectives of operational, environmental, and joint adjustments to each electricity production system. The operational and environmental performance changes over time were also captured through an effectiveness measure based on the global Malmquist productivity index. Our empirical results indicated that the performance of China's thermal power industry experienced significant progress during the study period and that policies regarding the development and regulation of the thermal power industry yielded the expected effects. However, the emissions reduction targets assigned to China's thermal power industry are loose and conservative. Copyright © 2017 Elsevier Ltd. All rights reserved.

In situ assessment of phytotechnologies for multicontaminated soil management.

PubMed

Ouvrard, S; Barnier, C; Bauda, P; Beguiristain, T; Biache, C; Bonnard, M; Caupert, C; Cébron, A; Cortet, J; Cotelle, S; Dazy, M; Faure, P; Masfaraud, J F; Nahmani, J; Palais, F; Poupin, P; Raoult, N; Vasseur, P; Morel, J L; Leyval, C

2011-01-01

Due to human activities, large volumes of soils are contaminated with organic pollutants such as polycyclic aromatic hydrocarbons, and very often by metallic pollutants as well. Multipolluted soils are therefore a key concern for remediation. This work presents a long-term evaluation of the fate and environmental impact of the organic and metallic contaminants of an industrially polluted soil under natural and plant-assisted conditions. A field trial was followed for four years according to six treatments in four replicates: unplanted, planted with alfalfa with or without mycorrhizal inoculation, planted with Noccaea caerulescens, naturally colonized by indigenous plants, and thermally treated soil planted with alfalfa. Leaching water volumes and composition, PAH concentrations in soil and solutions, soil fauna and microbial diversity, soil and solution toxicity using standardized bioassays, plant biomass, mycorrhizal colonization, were monitored. Results showed that plant cover alone did not affect total contaminant concentrations in soil. However, it was most efficient in improving the contamination impact on the environment and in increasing the biological diversity. Leaching water quality remained an issue because of its high toxicity shown by micro-algae testing. In this matter, prior treatment of the soil by thermal desorption proved to be the only effective treatment.

Modeling and optimization of a concentrated solar supercritical CO2 power plant

NASA Astrophysics Data System (ADS)

Osorio, Julian D.

Renewable energy sources are fundamental alternatives to supply the rising energy demand in the world and to reduce or replace fossil fuel technologies. In order to make renewable-based technologies suitable for commercial and industrial applications, two main challenges need to be solved: the design and manufacture of highly efficient devices and reliable systems to operate under intermittent energy supply conditions. In particular, power generation technologies based on solar energy are one of the most promising alternatives to supply the world energy demand and reduce the dependence on fossil fuel technologies. In this dissertation, the dynamic behavior of a Concentrated Solar Power (CSP) supercritical CO2 cycle is studied under different seasonal conditions. The system analyzed is composed of a central receiver, hot and cold thermal energy storage units, a heat exchanger, a recuperator, and multi-stage compression-expansion subsystems with intercoolers and reheaters between compressors and turbines respectively. The effects of operating and design parameters on the system performance are analyzed. Some of these parameters are the mass flow rate, intermediate pressures, number of compression-expansion stages, heat exchangers' effectiveness, multi-tank thermal energy storage, overall heat transfer coefficient between the solar receiver and the environment and the effective area of the recuperator. Energy and exergy models for each component of the system are developed to optimize operating parameters in order to lead to maximum efficiency. From the exergy analysis, the components with high contribution to exergy destruction were identified. These components, which represent an important potential of improvement, are the recuperator, the hot thermal energy storage tank and the solar receiver. Two complementary alternatives to improve the efficiency of concentrated solar thermal systems are proposed in this dissertation: the optimization of the system's operating parameters and optimization of less efficient components. The parametric optimization is developed for a 1MW reference CSP system with CO2 as the working fluid. The component optimization, focused on the less efficient components, comprises some design modifications to the traditional component configuration for the recuperator, the hot thermal energy storage tank and the solar receiver. The proposed optimization alternatives include the heat exchanger's effectiveness enhancement by optimizing fins shapes, multi-tank thermal energy storage configurations for the hot thermal energy storage tank and the incorporation of a transparent insulation material into the solar receiver. Some of the optimizations are conducted in a generalized way, using dimensionless models to be applicable no only to the CSP but also to other thermal systems. This project is therefore an effort to improve the efficiency of power generation systems based on solar energy in order to make them competitive with conventional fossil fuel power generation devices. The results show that the parametric optimization leads the system to an efficiency of about 21% and a maximum power output close to 1.5 MW. The process efficiencies obtained in this work, of more than 21%, are relatively good for a solar-thermal conversion system and are also comparable with efficiencies of conversion of high performance PV panels. The thermal energy storage allows the system to operate for several hours after sunset. This operating time is approximately increased from 220 to 480 minutes after optimization. The hot and cold thermal energy storage also lessens the temperature fluctuations by providing smooth changes of temperatures at the turbines' and compressors' inlets. Additional improvements in the overall system efficiency are possible by optimizing the less efficient components. In particular, the fin's effectiveness can be improved in more than 5% after its shape is optimized, increments in the efficiency of the thermal energy storage of about 5.7% are possible when the mass is divided into four tanks, and solar receiver efficiencies up to 70% can be maintained for high operating temperatures (~ 1200°C) when a transparent insulation material is incorporated to the receiver. The results obtained in this dissertation indicate that concentrated solar systems using supercritical CO2 could be a viable alternative to satisfying energy needs in desert areas with scarce water and fossil fuel resources.

Influence of moisture content of combusted wood on the thermal efficiency of a boiler

NASA Astrophysics Data System (ADS)

Dzurenda, Ladislav; Banski, Adrián

2017-03-01

In the paper the influence of moisture content of wood on the heat losses and thermal efficiency of a boiler is analysed. The moisture content of wood has a negative effect, especially on flue gas loss. The mathematical dependence of the thermal efficiency of a boiler is presented for the following boundary conditions: the moisture content of wood 10-60%, range of temperatures of emitted flue gases from the boiler into the atmosphere 120-200 C, the emissions meeting the emission standards: carbon monoxide 250 mgm-3, fly ash 50 mgm-3 and the heat power range 30-100%.

Thermal Protection for Mars Sample Return Earth Entry Vehicle: A Grand Challenge for Design Methodology and Reliability Verification

NASA Technical Reports Server (NTRS)

Venkatapathy, Ethiraj; Gage, Peter; Wright, Michael J.

2017-01-01

Mars Sample Return is our Grand Challenge for the coming decade. TPS (Thermal Protection System) nominal performance is not the key challenge. The main difficulty for designers is the need to verify unprecedented reliability for the entry system: current guidelines for prevention of backward contamination require that the probability of spores larger than 1 micron diameter escaping into the Earth environment be lower than 1 million for the entire system, and the allocation to TPS would be more stringent than that. For reference, the reliability allocation for Orion TPS is closer to 11000, and the demonstrated reliability for previous human Earth return systems was closer to 1100. Improving reliability by more than 3 orders of magnitude is a grand challenge indeed. The TPS community must embrace the possibility of new architectures that are focused on reliability above thermal performance and mass efficiency. MSR (Mars Sample Return) EEV (Earth Entry Vehicle) will be hit with MMOD (Micrometeoroid and Orbital Debris) prior to reentry. A chute-less aero-shell design which allows for self-righting shape was baselined in prior MSR studies, with the assumption that a passive system will maximize EEV robustness. Hence the aero-shell along with the TPS has to take ground impact and not break apart. System verification will require testing to establish ablative performance and thermal failure but also testing of damage from MMOD, and structural performance at ground impact. Mission requirements will demand analysis, testing and verification that are focused on establishing reliability of the design. In this proposed talk, we will focus on the grand challenge of MSR EEV TPS and the need for innovative approaches to address challenges in modeling, testing, manufacturing and verification.

A New Regime of Nanoscale Thermal Transport: Collective Diffusion Increases Dissipation Efficiency

DTIC Science & Technology

2015-04-21

including thermal management in nanoelectronics and optoelectronics, thermoelectric devices, nanoenhanced photovoltaics , and nanoparticle-mediated...applications including thermoelectrics for energyharvesting, nanoparticle-mediated thermal therapy, nano- enhanced photovoltaics , and thermal... thermoelectric devices, nanoparticle- mediated thermal therapies, and nanoenhanced photovoltaics for improving clean-energy technologies. Author contributions

Reappraisal of solid selective emitters

NASA Technical Reports Server (NTRS)

Chubb, Donald L.

1990-01-01

New rare earth oxide emitters show greater efficiency than previous emitters. As a result, based on a simple model the efficiency of these emitters was calculated. Results indicate that the emission band of the selective emitter must be at relatively low energy (less than or equal to .52 eV) to obtain maximum efficiency at moderate emitter temperatures (less than or equal to 1500 K). Thus low bandgap energy PV materials are required to obtain an efficient thermophotovoltaic (TPV) system. Of the 4 specific rare earths (Nd, Ho, Er, Yb) studied Ho has the largest efficiency at moderate temperatures (72 percent at 1500 K). A comparison was made between a selective emitter TPV system and a TPV system that uses a thermal emitter plus a band pass filter to make the thermal emitter behave like a selective emitter. Results of the comparison indicate that only for very optimistic filter and thermal emitter properties will the filter TPV system have a greater efficiency than the selective emitter system.

Photon energy upconversion through thermal radiation with the power efficiency reaching 16%.

PubMed

Wang, Junxin; Ming, Tian; Jin, Zhao; Wang, Jianfang; Sun, Ling-Dong; Yan, Chun-Hua

2014-11-28

The efficiency of many solar energy conversion technologies is limited by their poor response to low-energy solar photons. One way for overcoming this limitation is to develop materials and methods that can efficiently convert low-energy photons into high-energy ones. Here we show that thermal radiation is an attractive route for photon energy upconversion, with efficiencies higher than those of state-of-the-art energy transfer upconversion under continuous wave laser excitation. A maximal power upconversion efficiency of 16% is achieved on Yb(3+)-doped ZrO2. By examining various oxide samples doped with lanthanide or transition metal ions, we draw guidelines that materials with high melting points, low thermal conductivities and strong absorption to infrared light deliver high upconversion efficiencies. The feasibility of our upconversion approach is further demonstrated under concentrated sunlight excitation and continuous wave 976-nm laser excitation, where the upconverted white light is absorbed by Si solar cells to generate electricity and drive optical and electrical devices.

Thin film CdTe based neutron detectors with high thermal neutron efficiency and gamma rejection for security applications

NASA Astrophysics Data System (ADS)

Smith, L.; Murphy, J. W.; Kim, J.; Rozhdestvenskyy, S.; Mejia, I.; Park, H.; Allee, D. R.; Quevedo-Lopez, M.; Gnade, B.

2016-12-01

Solid-state neutron detectors offer an alternative to 3He based detectors, but suffer from limited neutron efficiencies that make their use in security applications impractical. Solid-state neutron detectors based on single crystal silicon also have relatively high gamma-ray efficiencies that lead to false positives. Thin film polycrystalline CdTe based detectors require less complex processing with significantly lower gamma-ray efficiencies. Advanced geometries can also be implemented to achieve high thermal neutron efficiencies competitive with silicon based technology. This study evaluates these strategies by simulation and experimentation and demonstrates an approach to achieve >10% intrinsic efficiency with <10-6 gamma-ray efficiency.

10 CFR Appendix P to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Pool Heaters

Code of Federal Regulations, 2013 CFR

2013-01-01

... least three significant figures shall be reported. 4.3Off mode. 4.3.1Pool heaters with a seasonal off... significant figures shall be reported. 5.Calculations. 5.1Thermal efficiency. Calculate the thermal efficiency...

Performance Evaluation of Dual-axis Tracking System of Parabolic Trough Solar Collector

NASA Astrophysics Data System (ADS)

Ullah, Fahim; Min, Kang

2018-01-01

A parabolic trough solar collector with the concentration ratio of 24 was developed in the College of Engineering; Nanjing Agricultural University, China with the using of the TracePro software an optical model built. Effects of single-axis and dual-axis tracking modes, azimuth and elevating angle tracking errors on the optical performance were investigated and the thermal performance of the solar collector was experimentally measured. The results showed that the optical efficiency of the dual-axis tracking was 0.813% and its year average value was 14.3% and 40.9% higher than that of the eat-west tracking mode and north-south tracking mode respectively. Further, form the results of the experiment, it was concluded that the optical efficiency was affected significantly by the elevation angle tracking errors which should be kept below 0.6o. High optical efficiency could be attained by using dual-tracking mode even though the tracking precision of one axis was degraded. The real-time instantaneous thermal efficiency of the collector reached to 0.775%. In addition, the linearity of the normalized efficiency was favorable. The curve of the calculated thermal efficiency agreed well with the normalized instantaneous efficiency curve derived from the experimental data and the maximum difference between them was 10.3%. This type of solar collector should be applied in middle-scale thermal collection systems.

Graphene oxide-based efficient and scalable solar desalination under one sun with a confined 2D water path

PubMed Central

Li, Xiuqiang; Xu, Weichao; Tang, Mingyao; Zhou, Lin; Zhu, Bin; Zhu, Shining; Zhu, Jia

2016-01-01

Because it is able to produce desalinated water directly using solar energy with minimum carbon footprint, solar steam generation and desalination is considered one of the most important technologies to address the increasingly pressing global water scarcity. Despite tremendous progress in the past few years, efficient solar steam generation and desalination can only be achieved for rather limited water quantity with the assistance of concentrators and thermal insulation, not feasible for large-scale applications. The fundamental paradox is that the conventional design of direct absorber−bulk water contact ensures efficient energy transfer and water supply but also has intrinsic thermal loss through bulk water. Here, enabled by a confined 2D water path, we report an efficient (80% under one-sun illumination) and effective (four orders salinity decrement) solar desalination device. More strikingly, because of minimized heat loss, high efficiency of solar desalination is independent of the water quantity and can be maintained without thermal insulation of the container. A foldable graphene oxide film, fabricated by a scalable process, serves as efficient solar absorbers (>94%), vapor channels, and thermal insulators. With unique structure designs fabricated by scalable processes and high and stable efficiency achieved under normal solar illumination independent of water quantity without any supporting systems, our device represents a concrete step for solar desalination to emerge as a complementary portable and personalized clean water solution. PMID:27872280

Graphene oxide-based efficient and scalable solar desalination under one sun with a confined 2D water path.

PubMed

Li, Xiuqiang; Xu, Weichao; Tang, Mingyao; Zhou, Lin; Zhu, Bin; Zhu, Shining; Zhu, Jia

2016-12-06

Because it is able to produce desalinated water directly using solar energy with minimum carbon footprint, solar steam generation and desalination is considered one of the most important technologies to address the increasingly pressing global water scarcity. Despite tremendous progress in the past few years, efficient solar steam generation and desalination can only be achieved for rather limited water quantity with the assistance of concentrators and thermal insulation, not feasible for large-scale applications. The fundamental paradox is that the conventional design of direct absorber-bulk water contact ensures efficient energy transfer and water supply but also has intrinsic thermal loss through bulk water. Here, enabled by a confined 2D water path, we report an efficient (80% under one-sun illumination) and effective (four orders salinity decrement) solar desalination device. More strikingly, because of minimized heat loss, high efficiency of solar desalination is independent of the water quantity and can be maintained without thermal insulation of the container. A foldable graphene oxide film, fabricated by a scalable process, serves as efficient solar absorbers (>94%), vapor channels, and thermal insulators. With unique structure designs fabricated by scalable processes and high and stable efficiency achieved under normal solar illumination independent of water quantity without any supporting systems, our device represents a concrete step for solar desalination to emerge as a complementary portable and personalized clean water solution.

On the thermal efficiency of power cycles in finite time thermodynamics

NASA Astrophysics Data System (ADS)

Momeni, Farhang; Morad, Mohammad Reza; Mahmoudi, Ashkan

2016-09-01

The Carnot, Diesel, Otto, and Brayton power cycles are reconsidered endoreversibly in finite time thermodynamics (FTT). In particular, the thermal efficiency of these standard power cycles is compared to the well-known results in classical thermodynamics. The present analysis based on FTT modelling shows that a reduction in both the maximum and minimum temperatures of the cycle causes the thermal efficiency to increase. This is antithetical to the existing trend in the classical references. Under the assumption of endoreversibility, the relation between the efficiencies is also changed to {η }{{Carnot}}\\gt {η }{{Brayton}}\\gt {η }{{Diesel}}\\gt {η }{{Otto}}, which is again very different from the corresponding classical results. The present results benefit a better understanding of the important role of irreversibility on heat engines in classical thermodynamics.

The reaction efficiency of thermal energy oxygen atoms with polymeric materials

NASA Technical Reports Server (NTRS)

Koontz, S. L.; Nordine, Paul

1990-01-01

The reaction efficiency of several polymeric materials with thermal-energy (0.04 eV translational energy), ground-state (O3P) oxygen atoms was determined by exposing the materials to a room temperature gas containing a known concentration of atomic oxygen. The reaction efficiency measurements were conducted in two flowing afterglow systems of different configuration. Atomic oxygen concentration measurements, flow, transport and surface dose analysis is presented in this paper. The measured reaction efficiencies of Kapton, Mylar, polyethylene, D4-polyethylene and Tedlar are .001 to .0001 those determined with high-energy ground-state oxygen atoms in low earth orbit or in a high-velocity atom beam. D4-polyethylene exhibits a large kinetic isotope effect with atomic oxygen at thermal but not hyperthermal atom energies.

Micro rectennas: Brownian ratchets for thermal-energy harvesting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Y.; Powell, C. V.; Balocco, C., E-mail: claudio.balocco@durham.ac.uk

2014-12-22

We experimentally demonstrated the operation of a rectenna for harvesting thermal (blackbody) radiation and converting it into dc electric power. The device integrates an ultrafast rectifier, the self-switching nanodiode, with a wideband log-periodic spiral microantenna. The radiation from the thermal source drives the rectenna out of thermal equilibrium, permitting the rectification of the excess thermal fluctuations from the antenna. The power conversion efficiency increases with the source temperatures up to 0.02% at 973 K. The low efficiency is attributed mainly to the impedance mismatch between antenna and rectifier, and partially to the large field of view of the antenna. Our devicemore » not only opens a potential solution for harvesting thermal energy but also provides a platform for experimenting with Brownian ratchets.« less

Applicability of advanced automotive heat engines to solar thermal power

NASA Technical Reports Server (NTRS)

Beremand, D. G.; Evans, D. G.; Alger, D. L.

1981-01-01

The requirements of a solar thermal power system are reviewed and compared with the predicted characteristics of automobile engines under development. A good match is found in terms of power level and efficiency when the automobile engines, designed for maximum powers of 65-100 kW (87 to 133 hp) are operated to the nominal 20-40 kW electric output requirement of the solar thermal application. At these reduced power levels it appears that the automotive gas turbine and Stirling engines have the potential to deliver the 40+ percent efficiency goal of the solar thermal program.

Applicability of advanced automotive heat engines to solar thermal power

NASA Astrophysics Data System (ADS)

Beremand, D. G.; Evans, D. G.; Alger, D. L.

The requirements of a solar thermal power system are reviewed and compared with the predicted characteristics of automobile engines under development. A good match is found in terms of power level and efficiency when the automobile engines, designed for maximum powers of 65-100 kW (87 to 133 hp) are operated to the nominal 20-40 kW electric output requirement of the solar thermal application. At these reduced power levels it appears that the automotive gas turbine and Stirling engines have the potential to deliver the 40+ percent efficiency goal of the solar thermal program.

Thermoelectric power generator for variable thermal power source

DOEpatents

Bell, Lon E; Crane, Douglas Todd

2015-04-14

Traditional power generation systems using thermoelectric power generators are designed to operate most efficiently for a single operating condition. The present invention provides a power generation system in which the characteristics of the thermoelectrics, the flow of the thermal power, and the operational characteristics of the power generator are monitored and controlled such that higher operation efficiencies and/or higher output powers can be maintained with variably thermal power input. Such a system is particularly beneficial in variable thermal power source systems, such as recovering power from the waste heat generated in the exhaust of combustion engines.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreno, Gilbert

The objective for this project is to develop thermal management strategies to enable efficient and high-temperature wide-bandgap (WBG)-based power electronic systems (e.g., emerging inverter and DC-DC converter). Device- and system-level thermal analyses are conducted to determine the thermal limitations of current automotive power modules under elevated device temperature conditions. Additionally, novel cooling concepts and material selection will be evaluated to enable high-temperature silicon and WBG devices in power electronics components. WBG devices (silicon carbide [SiC], gallium nitride [GaN]) promise to increase efficiency, but will be driven as hard as possible. This creates challenges for thermal management and reliability.

Advanced Power Sources for Space Missions

DTIC Science & Technology

1989-01-01

Range indicate that extremely high power levels hav- ing fast time-ramping capabilities must be provided during the tests. Only highly efficient prime...system efficiency results from advantages in thermal storage versus battery storage and from the increased conversion efficiency of a solar-dynamic... thermal manage- ment, power flow, and voltage levels, and may be in the same power range already experienced in the very- high -power radar and fusion

High-power 671  nm laser by second-harmonic generation with 93% efficiency in an external ring cavity.

PubMed

Cui, Xing-Yang; Shen, Qi; Yan, Mei-Chen; Zeng, Chao; Yuan, Tao; Zhang, Wen-Zhuo; Yao, Xing-Can; Peng, Cheng-Zhi; Jiang, Xiao; Chen, Yu-Ao; Pan, Jian-Wei

2018-04-15

Second-harmonic generation (SHG) is useful for obtaining single-frequency continuous-wave laser sources at various wavelengths for applications ranging from biology to fundamental physics. Using an external power-enhancement cavity is an effective approach to improve the frequency conversion efficiency. However, thermal effects limit the efficiency, particularly, in high-power operation. Therefore, reducing thermal effects is important when designing a cavity. This Letter reports the use of an external ring cavity for SHG, yielding a 5.2 W, 671 nm laser light with a conversion efficiency of 93.8±0.8% which, to the best of our knowledge, is a new record of conversion efficiency for an external ring cavity. It is achieved using a 10 mm length periodically poled potassium titanyl phosphate crystal and a 65 μm radius beam waist in the cavity so as to minimize thermal dephasing and thermal lensing. Furthermore, a method is developed to determine a conversion efficiency more accurately based on measuring the pump depletion using a photodiode detector and a maximum pump depletion up to 97% is recorded. In this method, the uncertainty is much less than that achieved in a common method by direct measuring with a power meter.

Thermal modeling of high efficiency AMTEC cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanenok, J.F. III; Sievers, R.K.; Crowley, C.J.

1995-12-31

Remotely condensed Alkali Metal Thermal to Electric Conversion (AMTEC) cells achieve high efficiency by thermally isolating the hot {beta} Alumina Solid Electrolyte (BASE) tube from the cold condensing region. In order to design high efficiency AMTEC cells the designer must understand the heat losses associated with the AMTEC process. The major parasitic heat losses are due to conduction and radiation, and significant coupling of the two mechanisms occurs. This paper describes an effort to characterize the thermal aspects of the model PL-6 AMTEC cell and apply this understanding to the design of a higher efficiency AMTEC cell, model PL-8. Twomore » parallel analyses were used to model the thermal characteristics of PL-6. The first was a lumped node model using the classical electric circuit analogy and the second was a detailed finite-difference model. The lumped node model provides high speed and reasonable accuracy, and the detailed finite-difference model provides a more accurate, as well as visual, description of the cell temperature profiles. The results of the two methods are compared to the as-measured PL-6 data. PL-6 was the first cell to use a micromachined condenser to lower the radiation losses to the condenser, and it achieved a conversion efficiency of 15% (3 W output/20 W Input) at a temperature of 1050 K.« less

Concentrating Solar Power Projects - Crescent Dunes Solar Energy Project |

Science.gov Websites

: None Thermal Storage Storage Type: 2-tank direct Storage Capacity: 10 hours Thermal Storage Description : Thermal energy storage achieved by raising salt temperature from 550 to 1050 F. Thermal storage efficiency

Thermal comfort of people in the hot and humid area of China-impacts of season, climate, and thermal history.

PubMed

Zhang, Y; Chen, H; Wang, J; Meng, Q

2016-10-01

We conducted a climate chamber study on the thermal comfort of people in the hot and humid area of China. Sixty subjects from naturally ventilated buildings and buildings with split air conditioners participated in the study, and identical experiments were conducted in a climate chamber in both summer and winter. Psychological and physiological responses were observed over a wide range of conditions, and the impacts of season, climate, and thermal history on human thermal comfort were analyzed. Seasonal and climatic heat acclimatization was confirmed, but they were found to have no significant impacts on human thermal sensation and comfort. The outdoor thermal history was much less important than the indoor thermal history in regard to human thermal sensation, and the indoor thermal history in all seasons of a year played a key role in shaping the subjects' sensations in a wide range of thermal conditions. A warmer indoor thermal history in warm seasons produced a higher neutral temperature, a lower thermal sensitivity, and lower thermal sensations in warm conditions. The comfort and acceptable conditions were identified for people in the hot and humid area of China. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Determination of temperature and residual laser energy on film fiber-optic thermal converter for diode laser surgery.

PubMed

Liu, Weichao; Kong, Yaqun; Shi, Xiafei; Dong, Xiaoxi; Wang, Hong; Zhao, Jizhi; Li, Yingxin

2017-12-01

The diode laser was utilized in soft tissue incision of oral surgery based on the photothermic effect. The contradiction between the ablation efficiency and the thermal damage has always been in diode laser surgery, due to low absorption of its radiation in the near infrared region by biological tissues. Fiber-optic thermal converters (FOTCs) were used to improve efficiency for diode laser surgery. The purpose of this study was to determine the photothermic effect by the temperature and residual laser energy on film FOTCs. The film FOTC was made by a distal end of optical fiber impacting on paper. The external surface of the converter is covered by a film contained amorphous carbon. The diode laser with 810 nm worked at the different rated power of 1.0 W, 1.5 W, 2.0 W, 3.0 W, 4.0 W, 5.0 W, 6.0 W, 7.0 W, 8.0 W in continuous wave (CW)and pulse mode. The temperature of the distal end of optical fiber was recorded and the power of the residual laser energy from the film FOTC was measured synchronously. The temperature, residual power and the output power were analyzed by linear or exponential regression model and Pearson correlations analysis. The residual power has good linearity versus output power in CW and pulse modes (R 2  = 0.963, P < 0.01 for both). The temperature on film FOTCs increases exponentially with adjusted R 2  = 0.959 in continuous wave mode, while in pulsed mode with adjusted R 2  = 0.934. The temperature was elevated up to about 210 °C and eventually to be a stable state. Film FOTCs centralized approximately 50% of laser energy on the fiber tip both in CW and pulsed mode while limiting the ability of the laser light to interact directly with target tissue. Film FOTCs can concentrate part of laser energy transferred to heat on distal end of optical fiber, which have the feasibility of improving efficiency and reducing thermal damage of deep tissue.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romero, R.; Singh, R.P.; Brown, D.

A thermal-energy accounting study was conducted at an apple processing plant. An analysis is given of thermal energy use and thermal efficiencies of an apple-juice single-effect evaporator and an apple-sauce cooker. 3 refs.

Study of Using Solar Thermal Power for the Margarine Melting Heat Process.

PubMed

Sharaf Eldean, Mohamed A; Soliman, A M

2015-04-01

The heating process of melting margarine requires a vast amount of thermal energy due to its high melting point and the size of the reservoir it is contained in. Existing methods to heat margarine have a high hourly cost of production and use fossil fuels which have been shown to have a negative impact on the environment. Thus, we perform an analytical feasibility study of using solar thermal power as an alternative energy source for the margarine melting process. In this study, the efficiency and cost effectiveness of a parabolic trough collector (PTC) solar field are compared with that of a steam boiler. Different working fluids (water vapor and Therminol-VP1 heat transfer oil (HTO)) through the solar field are also investigated. The results reveal the total hourly cost ($/h) by the conventional configuration is much greater than the solar applications regardless of the type of working fluid. Moreover, the conventional configuration causes a negative impact to the environment by increasing the amount of CO 2 , CO, and NO 2 by 117.4 kg/day, 184 kg/day, and 74.7 kg/day, respectively. Optimized period of melt and tank volume parameters at temperature differences not exceeding 25 °C are found to be 8-10 h and 100 m 3 , respectively. The solar PTC operated with water and steam as the working fluid is recommended as a vital alternative for the margarine melting heating process.

Heat engine development for solar thermal power systems

NASA Technical Reports Server (NTRS)

Pham, H. Q.; Jaffe, L. D.

1981-01-01

The technical status of three heat engines (Stirling, high-temperature Brayton, and Combined cycle) for use in solar thermal power systems is presented. Performance goals necessary to develop a system competitive with conventional power requirements include an external heated engine output less than 40 kW, and efficiency power conversion subsystem at least 40% at rated output, and a half-power efficiency of at least 37%. Results show that the Stirling engine can offer a 39% efficiency with 100 hours of life, and a 20% efficiency with 10,000 hours of life, but problems with seals and heater heads exist. With a demonstrated efficiency near 31% at 1500 F and a minimum lifetime of 100,000 hours, the Brayton engine does not offer sufficient engine lifetime, efficiency, and maintenance for solar thermal power systems. Examination of the Rankine bottoming cycle of the Combined cycle engine reveals a 30 year lifetime, but a low efficiency. Additional development of engines for solar use is primarily in the areas of components to provide a long lifetime, high reliability, and low maintenance (no more than $0.001/kW-hr).

High efficient bone ablation with diode pumped Erbium and Thulium lasers including different delivery fibers: a comparative in vitro study

NASA Astrophysics Data System (ADS)

Stock, Karl; Hausladen, Florian; Stegmayer, Thomas; Wurm, Holger

2018-02-01

Er:YAG lasers (3μm) allow efficient bone ablation caused by the strong absorption in water. Unfortunately, there are only a few and comparable expensive fiber materials for this wavelength available which are suitable for high laser power. The bone ablation efficiency of the Tm:YAG laser is minor (2μm) but inexpensive silica fibers can be used. The aim of this study was to investigate the bone ablation, using novel diode pumped high power Er:YAG (laser power 40W) and Tm:YAG laser system (60W) and adaptive fiber delivery systems. Expected advantage of these lasers is the longer lifetime of the fibers because of the high repetition rate and low pulse energy compared to the flash lamp pumped laser systems. The bare fiber output ends of a sapphire fiber (Er:YAG laser) and of a silica fiber (Tm:YAG laser) were attached under water and a water filled container including the fixed sample (bovine bone slices) was moved by a computer controlled translation stage. In a second set-up we provided a focusing unit and appropriate water spray unit. The generated cut kerfs were analyzed by light microcopy and laser scanning microscopy. The results show that with the diode pumped Er:YAG laser and sapphire fiber a particular high efficient bone ablation (> 0.16mm2/J) is possible both with bare fiber under water and focusing unit with water spray. The higher power of the Tm:YAG laser also results in high ablation rates but causes enlarged thermal damages. In conclusion, this study demonstrates that efficient bone ablation is possible with both diode pumped laser systems. In terms of efficiency the Er:YAG laser is outstanding. The Tm:YAG laser also allows fast bone ablation, provided that the thermal impact is limited by effective cooling and high movement velocity of the laser spot, for example by using an automatic scanner.

The Modulation of Crustal Magmatic Systems by Tectonic Forcing

NASA Astrophysics Data System (ADS)

Karakas, O.; Dufek, J.

2010-12-01

The amount, location and residence time of melt in the crust significantly impacts crustal structure and influences the composition, frequency, and volume of eruptive products. In this study, we develop a two dimensional model that simulates the response of the crust to prolonged mantle-derived intrusions in arc environments. The domain includes the entire crustal section and upper mantle and focuses on the evolving thermal structure due to intrusions and external tectonic forcing. Magmatic intrusion into the crust can be accommodated by extension or thickening of the crust or some combination of both mechanisms. Additionally, external tectonic forcing can generate thicker crustal sections, while tectonic extension can significantly thin the crust. We monitor the thermal response, melt fraction and surface heat flux for different tectonic conditions and melt flux from the mantle. The amount of crustal melt versus fractionated primary mantle melts present in the crustal column helps determine crustal structure and growth through time. We express the amount of crustal melting in terms of an efficiency; we define the melting efficiency as the ratio of the melted volume of crustal material to the volume of melt expected from a strict enthalpy balance as explained by Dufek and Bergantz (2005). Melting efficiencies are less than 1 in real systems because heat diffuses to sections of the crust that never melt. In general, thick crust and crust experiencing extended compressional regimes results in an increased melting efficiency; and thin crust and crust with high extension rates have lower efficiency. In most settings, maximum efficiencies are less than 0.05-0.10. We also observe that with a geophysically estimated flux, the mantle-derived magma bodies build up isolated magma pods that are distributed in the crust. One of the aspects of this work is to monitor the location and size of these magma chambers in the crustal column. We further investigate the rheological, stress and pre-existing structure control on the longevity of the individual magmatic systems.

Thermal Modeling of a Hybrid Thermoelectric Solar Collector with a Compound Parabolic Concentrator

NASA Astrophysics Data System (ADS)

Lertsatitthanakorn, C.; Jamradloedluk, J.; Rungsiyopas, M.

2013-07-01

In this study radiant light from the sun is used by a hybrid thermoelectric (TE) solar collector and a compound parabolic concentrator (CPC) to generate electricity and thermal energy. The hybrid TE solar collector system described in this report is composed of transparent glass, an air gap, an absorber plate, TE modules, a heat sink to cool the water, and a storage tank. Incident solar radiation falls on the CPC, which directs and reflects the radiation to heat up the absorber plate, creating a temperature difference across the TE modules. The water, which absorbs heat from the hot TE modules, flows through the heat sink to release its heat. The results show that the electrical power output and the conversion efficiency depend on the temperature difference between the hot and cold sides of the TE modules. A maximum power output of 1.03 W and a conversion efficiency of 0.6% were obtained when the temperature difference was 12°C. The thermal efficiency increased as the water flow rate increased. The maximum thermal efficiency achieved was 43.3%, corresponding to a water flow rate of 0.24 kg/s. These experimental results verify that using a TE solar collector with a CPC to produce both electrical power and thermal energy seems to be feasible. The thermal model and calculation method can be applied for performance prediction.

Experimental Studies on the Effect of Enhanced Thermal Conductivity of SiC+Water Nanofluid in the Performance of Small Scale Solar Parabolic Dish Receiver

NASA Astrophysics Data System (ADS)

Rajendran, D. R.; Sundaram, E. Ganapathy; Jawahar, P.

In this experimental study, exergy efficiencies of water and SiC+water nanofluid, prepared from 50nm particle size and 1% of volume fraction were compared based on the effect of thermal conductivities by a dish reflector receiver system. The average temperature difference between the receiver walls and heat transfer fluids have been studied to understand the thermal performance of the system with respect to the important properties of thermal conductivities and specific heat capacities. The enhanced thermal conductivity of 0.800115W/mK with the Keff/Kb ratio of 1.1759 was determined by the Koo and Kleinstreuer correlation which is considering both the Maxwell correlation and Brownian motion. The attained higher average exergy efficiencies for water and SiC+water nanofluid are 21.08% and 37.06.%, respectively with the enhanced nanofluid exergy efficiency of 75.80% than that of water at the flow rate of 0.5lpm. The result also shows that the system with SiC+water nanofluid produced higher exergy efficiency, because the rates of energy and exergy carried by the nanofluid are 0.2378kW and 0.7593kW higher than that of water for all the flow rates except at 0.2lpm, due to the enhanced thermal conductivity of the nanofluid.

An Environmental Management Model of Thermal Waters in Entre Ríos Province, Argentina

NASA Astrophysics Data System (ADS)

Pablo, Mársico Daniel; Luís, Díaz Eduardo; Ivana, Zecca; Oscar, Dallacosta; Antonio, Paz-González

2015-04-01

Deep exploratory drillings, i.e. those with more than 500 meters depth, have been performed in the Entre Ríos province, Argentina, in order to ascertain the presence of thermal water. Drilling began in 1994, and until now there have been 18 polls with very variable results in terms of mineralization, resource flow, and temperature. The aim of this study was to present a management model, which should allow operators of thermal complexes to further develop procedures for safeguarding the biodiversity of the ecosystems involved, both during exploration and exploitation activities. The environmental management Plan proposed is constituted by a set of technical procedures that are formulated and should be performed during the stages of exploration and exploitation of the resource, and consists of: environmental monitoring, environmental audit, public information and contingency programs. This Plan describes the measures and proposals aimed at protecting environmental quality in the area of influence of a thermal complex project, ensuring that its execution remains environmentally responsibly, and allowing implementation of specific actions to prevent or correct environmental impacts, as predicted in the evaluation of the Environmental Program. The audit of environmental impact includes and takes into account natural factors, such as water, soil, atmosphere, flora and fauna, and also cultural factors. The technical audit Plan was prepared in order to get a systematic structure and organization of the verification process, and also with regard to document the degree of implementation of the proposed mitigation measures. Finally, an environmental contingency program was implemented, and its objective was to consider the safeguarding of life and its natural environment. Thus, a guide has been developed with the main actions to be taken on a contingency, since forecast increases the efficiency of the response. The methodology developed here was adopted as the procedure required by the authority for the application and regulation of the hydro-geo-thermal resources of the province of Entre Ríos, and it is also useful for the control and protection of the resource.

Factors Of Environmental Safety And Environmentally Efficient Technologies Transportation Facilities Gas Transportation Industry

NASA Astrophysics Data System (ADS)

Vasiliev, Bogdan U.

2017-01-01

The stable development of the European countries depends on a reliable and efficient operation of the gas transportation system (GTS). With high reliability of GTS it is necessary to ensure its industrial and environmental safety. In this article the major factors influencing on an industrial and ecological safety of GTS are analyzed, sources of GTS safety decreasing is revealed, measures for providing safety are proposed. The article shows that use of gas-turbine engines of gas-compressor units (GCU) results in the following phenomena: emissions of harmful substances in the atmosphere; pollution by toxic waste; harmful noise and vibration; thermal impact on environment; decrease in energy efficiency. It is shown that for the radical problem resolution of an industrial and ecological safety of gas-transmission system it is reasonable to use gas-compressor units driven by electric motors. Their advantages are shown. Perspective technologies of these units and experience of their use in Europe and the USA are given in this article.

First evidence of bioflocculant from Shinella albus with flocculation activity on harvesting of Chlorella vulgaris biomass.

PubMed

Li, Yi; Xu, Yanting; Liu, Lei; Jiang, Xiaobing; Zhang, Kun; Zheng, Tianling; Wang, Hailei

2016-10-01

Bioflocculant from Shinella albus xn-1 could be used to harvest energy-producing microalga Chlorella vulgaris biomass for the first time. In this study, we investigated the flocculation activity and mode of strain xn-1, the characteristics of bioflocculant, the effect of flocculation conditions and optimized the flocculation efficiency. The results indicated that strain xn-1 exhibited flocculation activity through secreting bioflocculant; the bioflocculant with high thermal stability, pH stability and low molecular weight was proved to be not protein and polysaccharide, and flocculation active component was confirmed to contain triple bond and cumulated double bonds; algal pH, temperature and metal ions showed great impacts on the flocculation efficiency of bioflocculant; the maximum flocculation activity of bioflocculant reached 85.65% after the response surface optimization. According to the results, the bioflocculant from S. albus xn-1 could be a good potential in applications for high-efficiency harvesting of microalgae. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparative Kinetic Study and Microwaves Non-Thermal Effects on the Formation of Poly(amic acid) 4,4′-(Hexafluoroisopropylidene)diphthalic Anhydride (6FDA) and 4,4′-(Hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (BAPHF). Reaction Activated by Microwave, Ultrasound and Conventional Heating

PubMed Central

Tellez, Hugo Mendoza; Alquisira, Joaquín Palacios; Alonso, Carlos Rius; Cortés, José Guadalupe López; Toledano, Cecilio Alvarez

2011-01-01

Green chemistry is the design of chemical processes that reduce or eliminate negative environmental impacts. The use and production of chemicals involve the reduction of waste products, non-toxic components, and improved efficiency. Green chemistry applies innovative scientific solutions in the use of new reagents, catalysts and non-classical modes of activation such as ultrasounds or microwaves. Kinetic behavior and non-thermal effect of poly(amic acid) synthesized from (6FDA) dianhydride and (BAPHF) diamine in a low microwave absorbing p-dioxane solvent at low temperature of 30, 50, 70 °C were studied, under conventional heating (CH), microwave (MW) and ultrasound irradiation (US). Results show that the polycondensation rate decreases (MW > US > CH) and that the increased rates observed with US and MW are due to decreased activation energies of the Arrhenius equation. Rate constant for a chemical process activated by conventional heating declines proportionally as the induction time increases, however, this behavior is not observed under microwave and ultrasound activation. We can say that in addition to the thermal microwave effect, a non-thermal microwave effect is present in the system. PMID:22072913

Comparative kinetic study and microwaves non-thermal effects on the formation of poly(amic acid) 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4'-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (BAPHF). Reaction activated by microwave, ultrasound and conventional heating.

PubMed

Tellez, Hugo Mendoza; Alquisira, Joaquín Palacios; Alonso, Carlos Rius; Cortés, José Guadalupe López; Toledano, Cecilio Alvarez

2011-01-01

Green chemistry is the design of chemical processes that reduce or eliminate negative environmental impacts. The use and production of chemicals involve the reduction of waste products, non-toxic components, and improved efficiency. Green chemistry applies innovative scientific solutions in the use of new reagents, catalysts and non-classical modes of activation such as ultrasounds or microwaves. Kinetic behavior and non-thermal effect of poly(amic acid) synthesized from (6FDA) dianhydride and (BAPHF) diamine in a low microwave absorbing p-dioxane solvent at low temperature of 30, 50, 70 °C were studied, under conventional heating (CH), microwave (MW) and ultrasound irradiation (US). Results show that the polycondensation rate decreases (MW > US > CH) and that the increased rates observed with US and MW are due to decreased activation energies of the Arrhenius equation. Rate constant for a chemical process activated by conventional heating declines proportionally as the induction time increases, however, this behavior is not observed under microwave and ultrasound activation. We can say that in addition to the thermal microwave effect, a non-thermal microwave effect is present in the system.

Impact Foam Testing for Multi-Mission Earth Entry Vehicle Applications

NASA Technical Reports Server (NTRS)

Glaab, Louis J.; Agrawal, Paul; Hawbaker, James

2013-01-01

Multi-Mission Earth Entry Vehicles (MMEEVs) are blunt-body vehicles designed with the purpose of transporting payloads from outer space to the surface of the Earth. To achieve high-reliability and minimum weight, MMEEVs avoid use of limited-reliability systems, such as parachutes and retro-rockets, instead using built-in impact attenuators to absorb energy remaining at impact to meet landing loads requirements. The Multi-Mission Systems Analysis for Planetary Entry (M-SAPE) parametric design tool is used to facilitate the design of MMEEVs and develop the trade space. Testing was conducted to characterize the material properties of several candidate impact foam attenuators to enhance M-SAPE analysis. In the current effort, two different Rohacell foams were tested to determine their thermal conductivity in support of MMEEV design applications. These applications include thermal insulation during atmospheric entry, impact attenuation, and post-impact thermal insulation in support of thermal soak analysis. Results indicate that for these closed-cell foams, the effect of impact is limited on thermal conductivity due to the venting of the virgin material gas and subsequent ambient air replacement. Results also indicate that the effect of foam temperature is significant compared to data suggested by manufacturer's specifications.

Effective and efficient agricultural drainage pipe mapping with UAS thermal infrared imagery: a case study

USDA-ARS?s Scientific Manuscript database

Effective and efficient methods are needed to map agricultural subsurface drainage systems. Visible (VIS), near infrared (NIR), and/or thermal infrared (TIR) imagery obtained by unmanned aircraft systems (UAS) may provide a means for determining drainage pipe locations. Preliminary UAS surveys wit...

Enhanced Charge Extraction of Li-Doped TiO₂ for Efficient Thermal-Evaporated Sb₂S₃ Thin Film Solar Cells.

PubMed

Lan, Chunfeng; Luo, Jingting; Lan, Huabin; Fan, Bo; Peng, Huanxin; Zhao, Jun; Sun, Huibin; Zheng, Zhuanghao; Liang, Guangxing; Fan, Ping

2018-02-28

We provided a new method to improve the efficiency of Sb₂S₃ thin film solar cells. The TiO₂ electron transport layers were doped by lithium to improve their charge extraction properties for the thermal-evaporated Sb₂S₃ solar cells. The Mott-Schottky curves suggested a change of energy band and faster charge transport in the Li-doped TiO₂ films. Compared with the undoped TiO₂, Li-doped mesoporous TiO₂ dramatically improved the photo-voltaic performance of the thermal-evaporated Sb₂S₃ thin film solar cells, with the average power conversion efficiency ( PCE ) increasing from 1.79% to 4.03%, as well as the improved open-voltage ( V oc ), short-circuit current ( J sc ) and fill factors. The best device based on Li-doped TiO₂ achieved a power conversion efficiency up to 4.42% as well as a V oc of 0.645 V, which are the highest values among the reported thermal-evaporated Sb₂S₃ solar cells. This study showed that Li-doping on TiO₂ can effectively enhance the charge extraction properties of electron transport layers, offering a new strategy to improve the efficiency of Sb₂S₃-based solar cells.

Efficient 2-μm Tm:YAP Q-switched and CW lasers

NASA Astrophysics Data System (ADS)

Hays, A. D.; Cole, Brian; King, Vernon; Goldberg, Lew

2018-02-01

Highly efficient, diode pumped Tm:YAP lasers generating emission in the 1.85-1.94 μm range are demonstrated and characterized. Laser optical efficiencies of 51% and 45%, and electrical efficiencies of 31% and 25% are achieved under CW and Q-switched operation, respectively. Laser performance was characterized for maximum average powers up to 20W with various cavity configurations, all using an intra-cavity lens to compensate for thermal lensing in the Tm:YAP crystal. Q-switched lasers incorportating a Cr:ZnS saturable absorber (SA), resonant mechanical mirror scanner, or acousto-optic modulator were characterized. To enable higher average output powers, measurements of the thermal lens were conducted for the Tm:YAP crystal as a function of pump power and were compared to values predicted by a finiteelement- analysis (FEA) thermal-optical model of the Tm:YAP crystal. A resonator model is developed to incorporate this calculated thermal lens and its effect on laser performance. This paper will address approaches for improving the performance of Tm:YAP lasers, and means for achieving increased average output powers while maintaining high optical efficiency for both SA and mechanical Q-switching.

Full-spectrum volumetric solar thermal conversion via photonic nanofluids.

PubMed

Liu, Xianglei; Xuan, Yimin

2017-10-12

Volumetric solar thermal conversion is an emerging technique for a plethora of applications such as solar thermal power generation, desalination, and solar water splitting. However, achieving broadband solar thermal absorption via dilute nanofluids is still a daunting challenge. In this work, full-spectrum volumetric solar thermal conversion is demonstrated over a thin layer of the proposed 'photonic nanofluids'. The underlying mechanism is found to be the photonic superposition of core resonances, shell plasmons, and core-shell resonances at different wavelengths, whose coexistence is enabled by the broken symmetry of specially designed composite nanoparticles, i.e., Janus nanoparticles. The solar thermal conversion efficiency can be improved by 10.8% compared with core-shell nanofluids. The extinction coefficient of Janus dimers with various configurations is also investigated to unveil the effects of particle couplings. This work provides the possibility to achieve full-spectrum volumetric solar thermal conversion, and may have potential applications in efficient solar energy harvesting and utilization.

Well-preserved low thermal inertia ejecta deposits surrounding young secondary impact craters on Mars

NASA Astrophysics Data System (ADS)

Hill, J. R.; Christensen, P. R.

2017-06-01

Following the most recent updates to the Mars Odyssey Thermal Emission Imaging System daytime and nighttime infrared global mosaics, a colorized global map was produced that combines the thermophysical information from the nighttime infrared global mosaic with the morphologic context of the daytime infrared global mosaic. During the validation of this map, large numbers of low thermal inertia ejecta deposits surrounding small young impact craters were observed. A near-global survey (60°N-60°S) identified 4024 of these low thermal inertia ejecta deposits, which were then categorized based on their apparent state of degradation. Mapping their locations revealed that they occur almost exclusively in regions with intermediate-to-high thermal inertias, with distinct clusters in northern Terra Sirenum, Solis Planum, and southwestern Daedalia Planum. High-Resolution Imaging Science Experiment images show that the thermophysically distinct facies of the deposits are well correlated with the estimated average ejecta grain sizes, which decrease with radial distance from the crater. Comparisons with recent primary impact craters and secondary impact craters surrounding Zunil Crater show that the low thermal inertia ejecta deposits very closely resemble the secondary craters, but not the primary craters. We conclude that the low thermal inertia ejecta deposits are secondary impact crater ejecta deposits, many of which originated from the rayed crater primary impact events, and are both well preserved and easily identifiable due to the absence of dust cover and aeolian modification that would otherwise reduce the thermal contrast between the ejecta facies and the surrounding terrain.

Thermophotovoltaic Energy Conversion Development Program

NASA Technical Reports Server (NTRS)

Shukla, Kailash; Doyle, Edward; Becker, Frederick

1998-01-01

Completely integrated thermophotovoltaic (TPV) power sources in the range of 100 to 500 watts are being developed. The technical approach taken in this project focuses on optimizing the integrated performance of the primary subsystems in order to yield high energy conversion efficiency and cost effectiveness. An important aspect of the approach is the use of a narrow band fibrous emitter radiating to a bandgap matched photovoltaic array to minimize thermal and optical recuperation requirements, as well as the non-recoverable heat losses. For the prototype system, fibrous ytterbia emitters radiating in a narrow band centered at 980 nm are matched with high efficiency silicon photoconverters. The integrated system includes a dielectric stack filter for optical energy recovery and a ceramic recuperator for thermal energy recovery. The prototype TPV system uses a rapid mix distributed fuel delivery system with controlled feeding of the fuel and heated air into a flame at the surface of the emitter. This makes it possible to operate at air preheat temperatures well above the auto-ignition temperature of the fuel thereby substantially increasing the system efficiency. The system has been operated with air preheat temperatures up to 1367 K and has produced a uniform narrow band radiation over the surface of the emitter with this approach. The design of the system is described and test data for the system and some of the key components are presented. The results from a system model, which show the impact of various parameters on system performance, are also discussed.

In-situ comparison of thermal measurement technologies for interpretation of PV module temperature de-rating effects

NASA Astrophysics Data System (ADS)

Elwood, Teri; Bennett, Whit; Lai, Teh; Simmons-Potter, Kelly

2016-09-01

It is well known that the efficiency of a photovoltaic (PV) module is strongly impacted by its temperature such that higher temperatures lead to lower energy conversion efficiencies. An accurate measurement of the temperature de-rating effect, therefore, is vital to the correct interpretation of PV module performance under varied environmental conditions. The current work investigates and compares methods for performing measurements of module temperature both in the lab and in field-test environments. A comparison of several temperature measurement devices was made in order to establish the ideal sensor configuration for quantifying module operating temperature. Sensors were also placed in various locations along a string of up to eight photovoltaic modules to examine the variance in operating temperature with position in the string and within a larger array of strings.

Thermal model for impact breccia lithification - Manicouagan and the moon

NASA Technical Reports Server (NTRS)

Simonds, C. H.; Warner, J. L.; Phinney, W. C.; Mcgee, P. E.

1976-01-01

The thermal model of Simonds (1975) is extended to the full spectrum of impact-produced rocks ranging from fragmental breccias to impact melts, with reference to the Manicouagan impact structure in Quebec. This is done by relating the basic textural features of impact-lithified rocks to variations in the mixture of superheated impact-fused material originating near the point of impact and much cooler fragmented debris originating farther from the point of impact.

Efficient thermal noise removal of Sentinel-1 image and its impacts on sea ice applications

NASA Astrophysics Data System (ADS)

Park, Jeong-Won; Korosov, Anton; Babiker, Mohamed

2017-04-01

Wide swath SAR observation from several spaceborne SAR missions played an important role in studying sea ice in the polar region. Sentinel 1A and 1B are producing dual-polarization observation data with the highest temporal resolution ever. For a proper use of dense time-series, radiometric properties must be qualified. Thermal noise is often neglected in many sea ice applications, but is impacting seriously the utility of dual-polarization SAR data. Sentinel-1 TOPSAR image intensity is disturbed by additive thermal noise particularly in cross-polarization channel. Although ESA provides calibrated noise vectors for noise power subtraction, residual noise contribution is significant considering relatively narrow backscattering distribution of cross-polarization channel. In this study, we investigate the noise characteristics and propose an efficient method for noise reduction based on three types of correction: azimuth de-scalloping, noise scaling, and inter-swath power balancing. The core idea is to find optimum correction coefficients resulting in the most noise-uncorrelated gentle backscatter profile over homogeneous region and to combine them with scalloping gain for reconstruction of complete two-dimensional noise field. Denoising is accomplished by subtracting the reconstructed noise field from the original image. The resulting correction coefficients determined by extensive experiments showed different noise characteristics for different Instrument Processing Facility (IPF) versions of Level 1 product generation. Even after thermal noise subtraction, the image still suffers from residual noise, which distorts local statistics. Since this residual noise depends on local signal-to-noise ratio, it can be compensated by variance normalization with coefficients determined from an empirical model. Denoising improved not only visual interpretability but also performances in SAR intensity-based sea ice applications. Results from two applications showed the effectiveness of the proposed method: feature tracking based sea ice drift and texture analysis based sea ice classification. For feature tracking, large spatial asymmetry of keypoint distribution caused by higher noise level in the nearest subswath was decresed so that the matched features to be selected evenly in space. For texture analysis, inter-subswath texture differences caused by different noise equivalent sigma zero were normalized so that the texture features estimated in any subswath have similar value with those in other subswaths.

Recombination activity associated with thermal donor generation in monocrystalline silicon and effect on the conversion efficiency of heterojunction solar cells

NASA Astrophysics Data System (ADS)

Tomassini, M.; Veirman, J.; Varache, R.; Letty, E.; Dubois, S.; Hu, Y.; Nielsen, Ø.

2016-02-01

The recombination properties of the carrier lifetime-limiting center formed during the generation of oxygen-related thermal donors (so called "old" thermal donors) in n-type Czochralski silicon were determined over a wide range of thermal donors' concentrations. The procedure involved (1) determining the various energy levels associated with dopants with the help of temperature Hall effect measurements, (2) clarifying which energy level limits the carrier lifetime by temperature lifetime spectroscopy, and (3) determining the recombination parameters of the involved defect from room-temperature carrier lifetime curves. Our results support the fact that a deep energy level in the range of 0.2-0.3 eV below the conduction band limits the carrier lifetime. The second family of thermal donors, featuring bistable properties, was tentatively identified as the corresponding defect. From the obtained experimental data, the influence of the defect on the amorphous/crystalline silicon heterojunction solar cell conversion efficiency was simulated. It is observed that for extended donor generation, the carrier lifetime is reduced by orders-of-magnitude, leading to unacceptable losses in photovoltaic conversion efficiency. A key result is that even for samples with thermal donor concentrations of 1015 cm-3—often met in seed portions of commercial ingots—simulations reveal efficiency losses greater than 1% absolute for state-of-the-art cells, in agreement with recent experimental studies from our group. This result indicates to crystal growers the importance to mitigate the formation of thermal donors or to develop cost-effective processes to suppress them at the ingot/wafer scale. This is even more critical as ingot cool-down is likely to be slower for future larger ingots, thus promoting the formation of thermal donors.

Impact of tensile strain on the thermal transport of zigzag hexagonal boron nitride nanoribbon: An equilibrium molecular dynamics study

NASA Astrophysics Data System (ADS)

Navid, Ishtiaque Ahmed; Intisar Khan, Asir; Subrina, Samia

2018-02-01

The thermal conductivity of single layer strained hexagonal boron nitride nanoribbon (h-BNNR) has been computed using the Green—Kubo formulation of Equilibrium Molecular Dynamics (EMD) simulation. We have investigated the impact of strain on thermal transport of h-BNNR by varying the applied tensile strain from 1% upto 5% through uniaxial loading. The thermal conductivity of h-BNNR decreases monotonically with the increase of uniaxial tensile strain keeping the sample size and temperature constant. The thermal conductivity can be reduced upto 86% for an applied uniaxial tensile strain of 5%. The impact of temperature and width variation on the thermal conductivity of h-BNNR has also been studied under different uniaxial tensile strain conditions. With the increase in temperature, the thermal conductivity of strained h-BNNR exhibits a decaying characteristics whereas it shows an opposite pattern with the increasing width. Such study would provide a good insight on the strain tunable thermal transport for the potential device application of boron nitride nanostructures.

Thermal-Responsive Polymers for Enhancing Safety of Electrochemical Storage Devices.

PubMed

Yang, Hui; Leow, Wan Ru; Chen, Xiaodong

2018-03-01

Thermal runway constitutes the most pressing safety issue in lithium-ion batteries and supercapacitors of large-scale and high-power density due to risks of fire or explosion. However, traditional strategies for averting thermal runaway do not enable the charging-discharging rate to change according to temperature or the original performance to resume when the device is cooled to room temperature. To efficiently control thermal runaway, thermal-responsive polymers provide a feasible and reversible strategy due to their ability to sense and subsequently act according to a predetermined sequence when triggered by heat. Herein, recent research progress on the use of thermal-responsive polymers to enhance the thermal safety of electrochemical storage devices is reviewed. First, a brief discussion is provided on the methods of preventing thermal runaway in electrochemical storage devices. Subsequently, a short review is provided on the different types of thermal-responsive polymers that can efficiently avoid thermal runaway, such as phase change polymers, polymers with sol-gel transitions, and polymers with positive temperature coefficients. The results represent the important development of thermal-responsive polymers toward the prevention of thermal runaway in next-generation smart electrochemical storage devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impact excitation and electron-hole multiplication in graphene and carbon nanotubes.

PubMed

Gabor, Nathaniel M

2013-06-18

In semiconductor photovoltaics, photoconversion efficiency is governed by a simple competition: the incident photon energy is either transferred to the crystal lattice (heat) or transferred to electrons. In conventional materials, energy loss to the lattice is more efficient than energy transferred to electrons, thus limiting the power conversion efficiency. Quantum electronic systems, such as quantum dots, nanowires, and two-dimensional electronic membranes, promise to tip the balance in this competition by simultaneously limiting energy transfer to the lattice and enhancing energy transfer to electrons. By exploring the optical, thermal, and electronic properties of quantum materials, we may perhaps find an ideal optoelectronic material that provides low cost fabrication, facile systems integration, and a means to surpass the standard limit for photoconversion efficiency. Nanoscale carbon materials, such as graphene and carbon nanotubes, provide ideal experimental quantum systems in which to explore optoelectronic behavior for applications in solar energy harvesting. Within essentially the same material, researchers can achieve a broad spectrum of energetic configurations, from a gapless semimetal to a large band-gap semiconducting nanowire. Owing to their nanoscale dimensions, graphene and carbon nanotubes exhibit electronic and optical properties that reflect strong electron-electron interactions. Such strong interactions may lead to exotic low-energy electron transport behavior and high-energy electron scattering processes such as impact excitation and the inverse process of Auger recombination. High-energy processes, which become very important under photoexcitation, may be particularly efficient in nanoscale carbon materials due to the relativistic-like, charged particle band structure and sensitivity to the dielectric environment. In addition, due to the covalently bonded carbon framework that makes up these materials, electron-phonon coupling is very weak. In carbon nanomaterials, strong electron-electron interactions combined with weak electron-phonon interactions results in excellent optical, thermal and electronic properties, the exploration of which promises to reveal fundamentally new physical processes and deliver advanced nanotechnologies. In this Account, we review the results of novel optoelectronic experiments that explore the intrinsic photoresponse of carbon nanomaterials integrated into nanoscale devices. By fabricating gate voltage-controlled photodetectors composed of atomically thin sheets of graphene and individual carbon nanotubes, we are able to fully explore electron transport in these systems under optical illumination. We find that strong electron-electron interactions play a key role in the intrinsic photoresponse of both materials, as evidenced by hot carrier transport in graphene and highly efficient multiple electron-hole pair generation in nanotubes. In both of these quantum systems, photoexcitation leads to high-energy electron-hole pairs that relax energy predominantly into the electronic system, rather than heating the lattice. Due to highly efficient energy transfer from photons into electrons, graphene and carbon nanotubes may be ideal materials for solar energy harvesting devices with efficiencies that could exceed the Shockley-Queisser limit.

Neutronic and thermal-hydraulic analysis of fission molybdenum-99 production at Tehran Research Reactor using LEU plate targets.

PubMed

Abedi, Ebrahim; Ebrahimkhani, Marzieh; Davari, Amin; Mirvakili, Seyed Mohammad; Tabasi, Mohsen; Maragheh, Mohammad Ghannadi

2016-12-01

Efficient and safe production of molybdenum-99 ( 99 Mo) radiopharmaceutical at Tehran Research Reactor (TRR) via fission of LEU targets is studied. Neutronic calculations are performed to evaluate produced 99 Mo activity, core neutronic safety parameters and also the power deposition values in target plates during a 7 days irradiation interval. Thermal-hydraulic analysis has been also carried out to obtain thermal behavior of these plates. Using Thermal-hydraulic analysis, it can be concluded that the safety parameters are satisfied in the current study. Consequently, the present neutronic and thermal-hydraulic calculations show efficient 99 Mo production is accessible at significant activity values in TRR current core configuration. Copyright © 2016 Elsevier Ltd. All rights reserved.

Reduced thermal conductivity of nanotwinned random layer structures: a promising nanostructuring towards efficient Si and Si/Ge thermoelectric materials

NASA Astrophysics Data System (ADS)

Samaraweera, Nalaka; Chan, Kin L.; Mithraratne, Kumar

2018-05-01

Si and Si/Ge based nanostructures of reduced lattice thermal conductivity are widely attractive for developing efficient thermoelectric materials. In this study, we demonstrate the reduced thermal conductivity of Si nanotwinned random layer (NTRL) structures over corresponding superlattice and twin-free counterparts. The participation ratio analysis of vibrational modes shows that a possible cause of thermal conductivity reduction is phonon localization due to the random arrangement of twin boundaries. Via non-equilibrium molecular dynamic simulations, it is shown that ~23 and ~27% reductions over superlattice counterparts and ~55 and 53% over twin-free counterparts can be attained for the structures of total lengths of 90 and 170 nm, respectively. Furthermore, a random twin boundary distribution is applied for Si/Ge random layer structures seeking further reduction of thermal conductivity. A significant reduction in thermal conductivity of Si/Ge structures exceeding the thermal insulating performance of the corresponding amorphous Si structure by ~31% for a total length of 90 nm can be achieved. This reduction is as high as ~98% compared to the twin-free Si counterpart. It is demonstrated that application of randomly organised nanoscale twin boundaries is a promising nanostructuring strategy towards developing efficient Si and Si/Ge based thermoelectric materials in the future.

Power Electronics Thermal Management Research: Annual Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreno, Gilberto

The objective for this project is to develop thermal management strategies to enable efficient and high-temperature wide-bandgap (WBG)-based power electronic systems (e.g., emerging inverter and DC-DC converter). Reliable WBG devices are capable of operating at elevated temperatures (≥ 175 °Celsius). However, packaging WBG devices within an automotive inverter and operating them at higher junction temperatures will expose other system components (e.g., capacitors and electrical boards) to temperatures that may exceed their safe operating limits. This creates challenges for thermal management and reliability. In this project, system-level thermal analyses are conducted to determine the effect of elevated device temperatures on invertermore » components. Thermal modeling work is then conducted to evaluate various thermal management strategies that will enable the use of highly efficient WBG devices with automotive power electronic systems.« less

Molecular thermal transistor: Dimension analysis and mechanism

NASA Astrophysics Data System (ADS)

Behnia, S.; Panahinia, R.

2018-04-01

Recently, large challenge has been spent to realize high efficient thermal transistors. Outstanding properties of DNA make it as an excellent nano material in future technologies. In this paper, we introduced a high efficient DNA based thermal transistor. The thermal transistor operates when the system shows an increase in the thermal flux despite of decreasing temperature gradient. This is what called as negative differential thermal resistance (NDTR). Based on multifractal analysis, we could distinguish regions with NDTR state from non-NDTR state. Moreover, Based on dimension spectrum of the system, it is detected that NDTR state is accompanied by ballistic transport regime. The generalized correlation sum (analogous to specific heat) shows that an irregular decrease in the specific heat induces an increase in the mean free path (mfp) of phonons. This leads to the occurrence of NDTR.

Fuels for high-compression engines

NASA Technical Reports Server (NTRS)

Sparrow, Stanwood W

1926-01-01

From theoretical considerations one would expect an increase in power and thermal efficiency to result from increasing the compression ratio of an internal combustion engine. In reality it is upon the expansion ratio that the power and thermal efficiency depend, but since in conventional engines this is equal to the compression ratio, it is generally understood that a change in one ratio is accompanied by an equal change in the other. Tests over a wide range of compression ratios (extending to ratios as high as 14.1) have shown that ordinarily an increase in power and thermal efficiency is obtained as expected provided serious detonation or preignition does not result from the increase in ratio.

High efficiency thermal to electric energy conversion using selective emitters and spectrally tuned solar cells

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Flood, Dennis J.; Lowe, Roland A.

1992-01-01

Thermophotovoltaic (TPV) systems are attractive possibilities for direct thermal-to-electric energy conversion, but have typically required the use of black body radiators operating at high temperatures. Recent advances in both the understanding and performance of solid rare-earth oxide selective emitters make possible the use of TPV at temperatures as low as 1500 K. Depending on the nature of parasitic losses, overall thermal-to-electric conversion efficiencies greater than 20 percent are feasible.

Self-powered microthermionic converter

DOEpatents

Marshall, Albert C.; King, Donald B.; Zavadil, Kevin R.; Kravitz, Stanley H.; Tigges, Chris P.; Vawter, Gregory A.

2004-08-10

A self-powered microthermionic converter having an internal thermal power source integrated into the microthermionic converter. These converters can have high energy-conversion efficiencies over a range of operating temperatures. Microengineering techniques are used to manufacture the converter. The utilization of an internal thermal power source increases potential for mobility and incorporation into small devices. High energy efficiency is obtained by utilization of micron-scale interelectrode gap spacing. Alpha-particle emitting radioisotopes can be used for the internal thermal power source, such as curium and polonium isotopes.

Use of updated material properties in parametric optimization of spaceborne mirrors

NASA Astrophysics Data System (ADS)

Hull, Tony; Westerhoff, Thomas; Weidmann, Guenter; Kirchhoff, Rule

2016-07-01

Spaceborne sensor mirrors need to be both structurally efficient and to maintain figure through thermal transients. Both properties can be represented in a plot showing structural efficiency on one axis and thermal transient resilience on the other. For material selection, engineers have effectively used such charts. However in some cases thermal attributes have improved considerably. Using contemporary values, this comparison chart looks differently. We will discuss how lines of equal merit may be formulated differently depending on the orbit of the mission.

Spin Seebeck effect and thermal spin galvanic effect in Ni80Fe20/p-Si bilayers

NASA Astrophysics Data System (ADS)

Bhardwaj, Ravindra G.; Lou, Paul C.; Kumar, Sandeep

2018-01-01

The development of spintronics and spin-caloritronics devices needs efficient generation, detection, and manipulation of spin current. The thermal spin current from the spin-Seebeck effect has been reported to be more energy efficient than the electrical spin injection methods. However, spin detection has been the one of the bottlenecks since metals with large spin-orbit coupling is an essential requirement. In this work, we report an efficient thermal generation and interfacial detection of spin current. We measured a spin-Seebeck effect in Ni80Fe20 (25 nm)/p-Si (50 nm) (polycrystalline) bilayers without a heavy metal spin detector. p-Si, having a centrosymmetric crystal structure, has insignificant intrinsic spin-orbit coupling, leading to negligible spin-charge conversion. We report a giant inverse spin-Hall effect, essential for the detection of spin-Seebeck effects, in the Ni80Fe20/p-Si bilayer structure, which originates from Rashba spin orbit coupling due to structure inversion asymmetry at the interface. In addition, the thermal spin pumping in p-Si leads to spin current from p-Si to the Ni80Fe20 layer due to the thermal spin galvanic effect and the spin-Hall effect, causing spin-orbit torques. The thermal spin-orbit torques lead to collapse of magnetic hysteresis of the 25 nm thick Ni80Fe20 layer. The thermal spin-orbit torques can be used for efficient magnetic switching for memory applications. These scientific breakthroughs may give impetus to the silicon spintronics and spin-caloritronics devices.

Lobate impact melt flows within the extended ejecta blanket of Pierazzo crater

NASA Astrophysics Data System (ADS)

Bray, Veronica J.; Atwood-Stone, Corwin; Neish, Catherine D.; Artemieva, Natalia A.; McEwen, Alfred S.; McElwaine, Jim N.

2018-02-01

Impact melt flows are observed within the continuous and discontinuous ejecta blanket of the 9 km lunar crater Pierazzo, from the crater rim to more than 40 km away from the center of the crater. Our mapping, fractal analysis, and thermal modeling suggest that melt can be emplaced ballistically and, upon landing, can become separated from solid ejecta to form the observed flow features. Our analysis is based on the identification of established melt morphology for these in-ejecta flows and supported by fractal analysis and thermal modeling. We computed the fractal dimension for the flow boundaries and found values of D = 1.05-1.17. These are consistent with terrestrial basaltic lava flows (D = 1.06-1.2) and established lunar impact melt flows (D = 1.06-1.18), but inconsistent with lunar dry granular flows (D = 1.31-1.34). Melt flows within discontinuous ejecta deposits are noted within just 1.5% of the mapping area, suggesting that the surface expression of impact melt in the extended ejecta around craters of this size is rare, most likely due to the efficient mixing of melts with solid ejecta and local target rocks. However, if the ejected fragments (both, molten and solid) are large enough, segregation of melt and its consequent flow is possible. As most of the flows mapped in this work occur on crater-facing slopes, the development of defined melt flows within ejecta deposits might be facilitated by high crater-facing topography restricting the flow of ejecta soon after it makes ground contact, limiting the quenching of molten ejecta through turbulent mixing with solid debris. Our study confirms the idea that impact melt can travel far beyond the continuous ejecta blanket, adding to the lunar regolith over an extensive area.

Experimental study of heat transfer and thermal performance with longitudinal fins of solar air heater

PubMed Central

Chabane, Foued; Moummi, Noureddine; Benramache, Said

2013-01-01

The thermal performance of a single pass solar air heater with five fins attached was investigated experimentally. Longitudinal fins were used inferior the absorber plate to increase the heat exchange and render the flow fluid in the channel uniform. The effect of mass flow rate of air on the outlet temperature, the heat transfer in the thickness of the solar collector, and the thermal efficiency were studied. Experiments were performed for two air mass flow rates of 0.012 and 0.016 kg s−1. Moreover, the maximum efficiency values obtained for the 0.012 and 0.016 kg s−1 with and without fins were 40.02%, 51.50% and 34.92%, 43.94%, respectively. A comparison of the results of the mass flow rates by solar collector with and without fins shows a substantial enhancement in the thermal efficiency. PMID:25685486

Experimental study of heat transfer and thermal performance with longitudinal fins of solar air heater.

PubMed

Chabane, Foued; Moummi, Noureddine; Benramache, Said

2014-03-01

The thermal performance of a single pass solar air heater with five fins attached was investigated experimentally. Longitudinal fins were used inferior the absorber plate to increase the heat exchange and render the flow fluid in the channel uniform. The effect of mass flow rate of air on the outlet temperature, the heat transfer in the thickness of the solar collector, and the thermal efficiency were studied. Experiments were performed for two air mass flow rates of 0.012 and 0.016 kg s(-1). Moreover, the maximum efficiency values obtained for the 0.012 and 0.016 kg s(-1) with and without fins were 40.02%, 51.50% and 34.92%, 43.94%, respectively. A comparison of the results of the mass flow rates by solar collector with and without fins shows a substantial enhancement in the thermal efficiency.

Indirect measurement of the thermal-acoustic efficiency spectrum of a long turbulent burner

NASA Technical Reports Server (NTRS)

Mahan, J. R.; Jones, J. D.; Blevins, L. R.; Cline, J. G.

1983-01-01

A new method is described for deducing the thermal-acoustic efficiency spectrum (defined as the fraction of combustion heat release converted to acoustic energy at a given frequency) of a long turbulent burner from the sound spectrum measured in the far field. The method, which is based on a one-dimensional model of the unsteady flow in the burner, is applied to a tubular diffusion-flame hydrogen burner whose length is large compared to its diameter. The results for thermal powers ranging from 4.5 to 22.3 kW show that the thermal-acoustic efficiency is relatively insensitive to the burner power level, decreasing from a value of around 0.0001 at 150 Hz with a slope of about 20 dB per decade. Evidence is presented indicating that acoustic agitation of the flame below 500 Hz, especially in the neighborhood of the resonant frequencies of the burner, is a significant acoustic source.

Using copper substrate to enhance the thermal conductivity of top-emission organic light-emitting diodes for improving the luminance efficiency and lifetime

NASA Astrophysics Data System (ADS)

Tsai, Yu-Sheng; Wang, Shun-Hsi; Chen, Chuan-Hung; Cheng, Chien-Lung; Liao, Teh-Chao

2009-12-01

The influence of heat dissipation on the performances of organic light-emitting diode (OLED) is investigated by measuring junction temperature and by calculating the rate of heat flow. The calculated rate of heat flow reveals that the key factors include the thermal conductivity, the substrate thickness, and the UV glue. Moreover, the use of copper substrate can effectively dissipate the joule heat, which then reduces the temperature gradient. Finally, it is shown that the use of a high thermal conductivity thinner substrate can enhance the thermal conductivity of OLED and the luminance efficiency as well.

Significant thermal conductivity reduction of silicon nanowire forests through discrete surface doping of germanium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Ying; Hong, Guo; Raja, Shyamprasad N.

2015-03-02

Silicon nanowires (SiNWs) are promising materials for the realization of highly-efficient and cost effective thermoelectric devices. Reduction of the thermal conductivity of such materials is a necessary and viable pathway to achieve sufficiently high thermoelectric efficiencies, which are inversely proportional to the thermal conductivity. In this article, vertically aligned forests of SiNW and germanium (Ge)-doped SiNW with diameters around 100 nm have been fabricated, and their thermal conductivity has been measured. The results show that discrete surface doping of Ge on SiNW arrays can lead to 23% reduction in thermal conductivity at room temperature compared to uncoated SiNWs. Such reduction canmore » be further enhanced to 44% following a thermal annealing step. By analyzing the binding energy changes of Ge-3d and Si-2p using X-ray photoelectron spectroscopy, we demonstrate that surface doped Ge interacts strongly with Si, enhancing phonon scattering at the Si-Ge interface as has also been shown in non-equilibrium molecular dynamics studies of single nanowires. Overall, our results suggest a viable pathway to improve the energy conversion efficiency of nanowire-forest thermoelectric nanomaterials.« less

Reliability and Heat Transfer Performance of a Miniature High-Temperature Thermosyphon-Based Thermal Valve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alleman, Jeffrey L; Olsen, Michele L; Glatzmaier, Gregory C

Latent heat thermal energy storage systems have the advantages of near isothermal heat release and high energy density compared to sensible heat, generally resulting in higher power block efficiencies. Until now, there has been no highly effective and reliable method to passively extract that stored latent energy. Most modern attempts rely on external power supplied to a pump to move viscous heat transfer fluids from the phase change material (PCM) to the power block. In this work, the problem of latent heat dispatchability has been addressed with a redesigned thermosyphon geometry that can act as a 'thermal valve' capable ofmore » passively and efficiently controlling the release of heat from a thermal reservoir. A bench-scale prototype with a stainless steel casing and sodium working fluid was designed and tested to be reliable for more than fifty 'on/off' cycles at an operating temperature of 600 degrees C. The measured thermal resistances in the 'on' and 'off' states were 0.0395 K/W and 11.0 K/W respectively. This device demonstrated efficient, fast, reliable, and passive heat extraction from a PCM and may have application to other fields and industries using thermal processing.« less

AISI/DOE Technology Roadmap Program: Development of Cost-effective, Energy-efficient Steel Framing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nader R. Elhajj

2003-01-06

Steel members in wall construction form a thermal bridge that interrupts the insulation layer of a wall. This causes higher rate of heat transfer by conduction through the wall framing than through other parts of the wall. One method to reduce the thermal bridging effect is to provide a break, such as insulating sheathing. A thermally efficient slit-web and stud was developed in this program to mitigate the conductivity of steel. The thermal performance of the slit-web stud was evaluated at Oak Ridge National Laboratory using hotbox testing. The thermal test results showed that the prototype slit-web stud performed 17%more » better than the solid-web stud, using R-13 fiber glass batts with exterior OSB sheathing and interior drywall. The structural behavior of this slit-web stud was evaluated in axial, bending, shear, shearwall, and stub-column tests. Test results indicated that the slitweb stud performed similarly or better than the solid-web stud in most structural performance characteristics investigated. Thus, the prototype slit-web stud has been shown to be thermally efficient, economiexecy viable, structurally sound, easily manufactured and usable in a range of residential installations.« less

Heat transfer and thermal management of electric vehicle batteries with phase change materials

NASA Astrophysics Data System (ADS)

Ramandi, M. Y.; Dincer, I.; Naterer, G. F.

2011-07-01

This paper examines a passive thermal management system for electric vehicle batteries, consisting of encapsulated phase change material (PCM) which melts during a process to absorb the heat generated by a battery. A new configuration for the thermal management system, using double series PCM shells, is analyzed with finite volume simulations. A combination of computational fluid dynamics (CFD) and second law analysis is used to evaluate and compare the new system against the single PCM shells. Using a finite volume method, heat transfer in the battery pack is examined and the results are used to analyse the exergy losses. The simulations provide design guidelines for the thermal management system to minimize the size and cost of the system. The thermal conductivity and melting temperature are studied as two important parameters in the configuration of the shells. Heat transfer from the surroundings to the PCM shell in a non-insulated case is found to be infeasible. For a single PCM system, the exergy efficiency is below 50%. For the second case for other combinations, the exergy efficiencies ranged from 30-40%. The second shell content did not have significant influence on the exergy efficiencies. The double PCM shell system showed higher exergy efficiencies than the single PCM shell system (except a case for type PCM-1). With respect to the reference environment, it is found that in all cases the exergy efficiencies decreased, when the dead-state temperatures rises, and the destroyed exergy content increases gradually. For the double shell systems for all dead-state temperatures, the efficiencies were very similar. Except for a dead-state temperature of 302 K, with the other temperatures, the exergy efficiencies for different combinations are well over 50%. The range of exergy efficiencies vary widely between 15 and 85% for a single shell system, and between 30-80% for double shell systems.

UMR’S DESIGN FOR AN ENVIRONMENTAL STEP AHEAD: SOLAR THERMAL ELECTRIC PANELS

EPA Science Inventory

Not only is the STEP hybrid system effective in its aesthetics but also it is more efficient than its two stand-alone counterparts. The estimated overall efficiency of the STEP system is estimated to be 15-45 percent as compared to a separate thermal and separate electric sy...

Energy efficiency in light-frame wood construction

Treesearch

Gerald E. Sherwood; Gunard Hans

1979-01-01

This report presents information needed for design and construction of energy-efficient light-frame wood structures. The opening section discusses improving the thermal performance of a house by careful planning and design. A second section of the report provides technical information on the thermal properties of construction materials, and on the basic engineering...

High-Efficiency Solar Thermal Vacuum Demonstration Completed for Refractive Secondary Concentrator

NASA Technical Reports Server (NTRS)

Wong, Wayne A.

2001-01-01

Common to many of the space applications that utilize solar thermal energy--such as electric power conversion, thermal propulsion, and furnaces--is a need for highly efficient, solar concentration systems. An effort is underway at the NASA Glenn Research Center to develop the refractive secondary concentrator, which uses refraction and total internal reflection to efficiently concentrate and direct solar energy. When used in combination with advanced lightweight primary concentrators, the refractive secondary concentrator enables very high system concentration ratios (10,000 to 1) and very high temperatures (>2000 K). The innovative refractive secondary concentrator offers significant advantages over all other types of secondary concentrators. The refractive secondary offers the highest throughput efficiency, provides for flux tailoring, requires no active cooling, relaxes the pointing and tracking requirements of the primary concentrator, and enables very high system concentration ratios. This technology has broad applicability to any system that requires the conversion of solar energy to heat. Glenn initiated the development of the refractive secondary concentrator in support of Shooting Star, a solar thermal propulsion flight experiment, and continued the development in support of Space Solar Power.

The nature of Stokes efficiency in a rocked ratchet

NASA Astrophysics Data System (ADS)

Sahoo, Mamata; Jayannavar, A. M.

2017-05-01

We have introduced the notion of stochastic Stokes efficiency in thermal ratchets or molecular motors. These ratchet systems comprise of Brownian particles in a nonequilibrium state and they show unidirectional currents in the absence of obvious bias. They convert nonequilibrium fluctuations into useful work. Our study reveals that the average stochastic Stokes efficiency can be very large, however, dominated by the thermal fluctuations. To this end we have obtained the full probability distribution of the stochastic Stokes efficiency, which exhibits novel behaviour as a function of the strength of the external drive. Stokes efficiency decreases as we go from adiabatic to the nonadiabatic regime.

Thermal Characterization of Nanostructures and Advanced Engineered Materials

NASA Astrophysics Data System (ADS)

Goyal, Vivek Kumar

Continuous downscaling of Si complementary metal-oxide semiconductor (CMOS) technology and progress in high-power electronics demand more efficient heat removal techniques to handle the increasing power density and rising temperature of hot spots. For this reason, it is important to investigate thermal properties of materials at nanometer scale and identify materials with the extremely large or extremely low thermal conductivity for applications as heat spreaders or heat insulators in the next generation of integrated circuits. The thin films used in microelectronic and photonic devices need to have high thermal conductivity in order to transfer the dissipated power to heat sinks more effectively. On the other hand, thermoelectric devices call for materials or structures with low thermal conductivity because the performance of thermoelectric devices is determined by the figure of merit Z=S2sigma/K, where S is the Seebeck coefficient, K and sigma are the thermal and electrical conductivity, respectively. Nanostructured superlattices can have drastically reduced thermal conductivity as compared to their bulk counterparts making them promising candidates for high-efficiency thermoelectric materials. Other applications calling for thin films with low thermal conductivity value are high-temperature coatings for engines. Thus, materials with both high thermal conductivity and low thermal conductivity are technologically important. The increasing temperature of the hot spots in state-of-the-art chips stimulates the search for innovative methods for heat removal. One promising approach is to incorporate materials, which have high thermal conductivity into the chip design. Two suitable candidates for such applications are diamond and graphene. Another approach is to integrate the high-efficiency thermoelectric elements for on-spot cooling. In addition, there is strong motivation for improved thermal interface materials (TIMs) for heat transfer from the heat-generating chip to heat-sinking units. This dissertation presents results of the experimental investigation and theoretical interpretation of thermal transport in the advanced engineered materials, which include thin films for thermal management of nanoscale devices, nanostructured superlattices as promising candidates for high-efficiency thermoelectric materials, and improved TIMs with graphene and metal particles as fillers providing enhanced thermal conductivity. The advanced engineered materials studied include chemical vapor deposition (CVD) grown ultrananocrystalline diamond (UNCD) and microcrystalline diamond (MCD) films on Si substrates, directly integrated nanocrystalline diamond (NCD) films on GaN, free-standing polycrystalline graphene (PCG) films, graphene oxide (GOx) films, and "pseudo-superlattices" of the mechanically exfoliated Bi2Te3 topological insulator films, and thermal interface materials (TIMs) with graphene fillers.

Effects of basin-forming impacts on the thermal evolution and magnetic field of Mars

NASA Astrophysics Data System (ADS)

Roberts, J. H.; Arkani-Hamed, J.

2017-11-01

The youngest of the giant impact basins on Mars are either weakly magnetized or completely demagnetized, indicating that a global magnetic field was not present at the time those basins formed. Eight basins are sufficiently large that the impact heating associated with their formation could have penetrated below the core-mantle boundary (CMB). Here we investigate the thermal evolution of the martian interior and the fate of the global magnetic field using 3D mantle convection models coupled to a parameterized 1D core thermal evolution model. We find that the survival of the impact-induced temperature anomalies in the upper mantle is strongly controlled by the mantle viscosity. Impact heating from subsequent impacts can accumulate in stiffer mantles faster than it can be advected away, resulting in a thermal blanket that insulates an entire hemisphere. The impact heating in the core will halt dynamo activity, at least temporarily. If the mantle is initially cold, and the core initially superheated, dynamo activity may resume as quickly as a few Myr after each impact. However unless the lower mantle has either a low viscosity or a high thermal conductivity, this restored dynamo will last for only a few hundred Myr after the end of the sequence of impacts. Thus, we find that the longevity of the magnetic field is more strongly controlled by the lower mantle properties and relatively insensitive to the impact-induced temperature anomalies in the upper mantle.

Effect of Material Composition and Environmental Condition on Thermal Characteristics of Conductive Asphalt Concrete.

PubMed

Pan, Pan; Wu, Shaopeng; Hu, Xiaodi; Liu, Gang; Li, Bo

2017-02-23

Conductive asphalt concrete with high thermal conductivity has been proposed to improve the solar energy collection and snow melting efficiencies of asphalt solar collector (ASC). This paper aims to provide some insight into choosing the basic materials for preparation of conductive asphalt concrete, as well as determining the evolution of thermal characteristics affected by environmental factors. The thermal properties of conductive asphalt concrete were studied by the Thermal Constants Analyzer. Experimental results showed that aggregate and conductive filler have a significant effect on the thermal properties of asphalt concrete, while the effect of asphalt binder was not evident due to its low proportion. Utilization of mineral aggregate and conductive filler with higher thermal conductivity is an efficient method to prepare conductive asphalt concrete. Moreover, change in thermal properties of asphalt concrete under different temperature and moisture conditions should be taken into account to determine the actual thermal properties of asphalt concrete. There was no noticeable difference in thermal properties of asphalt concrete before and after aging. Furthermore, freezing-thawing cycles strongly affect the thermal properties of conductive asphalt concrete, due to volume expansion and bonding degradation.

Effect of Material Composition and Environmental Condition on Thermal Characteristics of Conductive Asphalt Concrete

PubMed Central

Pan, Pan; Wu, Shaopeng; Hu, Xiaodi; Liu, Gang; Li, Bo

2017-01-01

Conductive asphalt concrete with high thermal conductivity has been proposed to improve the solar energy collection and snow melting efficiencies of asphalt solar collector (ASC). This paper aims to provide some insight into choosing the basic materials for preparation of conductive asphalt concrete, as well as determining the evolution of thermal characteristics affected by environmental factors. The thermal properties of conductive asphalt concrete were studied by the Thermal Constants Analyzer. Experimental results showed that aggregate and conductive filler have a significant effect on the thermal properties of asphalt concrete, while the effect of asphalt binder was not evident due to its low proportion. Utilization of mineral aggregate and conductive filler with higher thermal conductivity is an efficient method to prepare conductive asphalt concrete. Moreover, change in thermal properties of asphalt concrete under different temperature and moisture conditions should be taken into account to determine the actual thermal properties of asphalt concrete. There was no noticeable difference in thermal properties of asphalt concrete before and after aging. Furthermore, freezing–thawing cycles strongly affect the thermal properties of conductive asphalt concrete, due to volume expansion and bonding degradation. PMID:28772580

Integrated transient thermal-structural finite element analysis

NASA Technical Reports Server (NTRS)

Thornton, E. A.; Dechaumphai, P.; Wieting, A. R.; Tamma, K. K.

1981-01-01

An integrated thermal structural finite element approach for efficient coupling of transient thermal and structural analysis is presented. Integrated thermal structural rod and one dimensional axisymmetric elements considering conduction and convection are developed and used in transient thermal structural applications. The improved accuracy of the integrated approach is illustrated by comparisons with exact transient heat conduction elasticity solutions and conventional finite element thermal finite element structural analyses.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Blarigan, P.

A hydrogen fueled engine is being developed specifically for the auxiliary power unit (APU) in a series type hybrid vehicle. Hydrogen is different from other internal combustion (IC) engine fuels, and hybrid vehicle IC engine requirements are different from those of other IC vehicle engines. Together these differences will allow a new engine design based on first principles that will maximize thermal efficiency while minimizing principal emissions. The experimental program is proceeding in four steps: (1) Demonstration of the emissions and the indicated thermal efficiency capability of a standard CLR research engine modified for higher compression ratios and hydrogen fueledmore » operation. (2) Design and test a new combustion chamber geometry for an existing single cylinder research engine, in an attempt to improve on the baseline indicated thermal efficiency of the CLR engine. (3) Design and build, in conjunction with an industrial collaborator, a new full scale research engine designed to maximize brake thermal efficiency. Include a full complement of combustion diagnostics. (4) Incorporate all of the knowledge thus obtained in the design and fabrication, by an industrial collaborator, of the hydrogen fueled engine for the hybrid vehicle power train illustrator. Results of the CLR baseline engine testing are presented, as well as preliminary data from the new combustion chamber engine. The CLR data confirm the low NOx produced by lean operation. The preliminary indicated thermal efficiency data from the new combustion chamber design engine show an improvement relative to the CLR engine. Comparison with previous high compression engine results shows reasonable agreement.« less

High-performance noncontact thermal diode via asymmetric nanostructures

NASA Astrophysics Data System (ADS)

Shen, Jiadong; Liu, Xianglei; He, Huan; Wu, Weitao; Liu, Baoan

2018-05-01

Electric diodes, though laying the foundation of modern electronics and information processing industries, suffer from ineffectiveness and even failure at high temperatures. Thermal diodes are promising alternatives to relieve above limitations, but usually possess low rectification ratios, and how to obtain a high-performance thermal rectification effect is still an open question. This paper proposes an efficient contactless thermal diode based on the near-field thermal radiation of asymmetric doped silicon nanostructures. The rectification ratio computed via exact scattering theories is demonstrated to be as high as 10 at a nanoscale gap distance and period, outperforming the counterpart flat-plate diode by more than one order of magnitude. This extraordinary performance mainly lies in the higher forward and lower reverse radiative heat flux within the low frequency band compared with the counterpart flat-plate diode, which is caused by a lower loss and smaller cut-off wavevector of nanostructures for the forward and reversed scheme, respectively. This work opens new routes to realize high performance thermal diodes, and may have wide applications in efficient thermal computing, thermal information processing, and thermal management.

Vertically Aligned Graphene Sheets Membrane for Highly Efficient Solar Thermal Generation of Clean Water.

PubMed

Zhang, Panpan; Li, Jing; Lv, Lingxiao; Zhao, Yang; Qu, Liangti

2017-05-23

Efficient utilization of solar energy for clean water is an attractive, renewable, and environment friendly way to solve the long-standing water crisis. For this task, we prepared the long-range vertically aligned graphene sheets membrane (VA-GSM) as the highly efficient solar thermal converter for generation of clean water. The VA-GSM was prepared by the antifreeze-assisted freezing technique we developed, which possessed the run-through channels facilitating the water transport, high light absorption capacity for excellent photothermal transduction, and the extraordinary stability in rigorous conditions. As a result, VA-GSM has achieved average water evaporation rates of 1.62 and 6.25 kg m -2 h -1 under 1 and 4 sun illumination with a superb solar thermal conversion efficiency of up to 86.5% and 94.2%, respectively, better than that of most carbon materials reported previously, which can efficiently produce the clean water from seawater, common wastewater, and even concentrated acid and/or alkali solutions.

Thermal Transmittance and the Embodied Energy of Timber Frame Lightweight Walls Insulated with Straw and Reed

NASA Astrophysics Data System (ADS)

Miljan, M.; Miljan, J.

2015-11-01

Sustainable energy use has become topical in the whole world. Energy gives us comfort we are used to. EU and national regulations determine energy efficiency of the buildings. This is one side of the problem - energy efficiency of houses during exploitation. But the other side is primary energy content of used materials and more rational use of resources during the whole life cycle of a building. The latter value constitutes about 8 - 20% from the whole energy content. Calculations of energy efficiency of materials lead us to energy efficiency of insulation materials and to comparison of natural and industrial materials taking into account their thermal conductivity as well as their primary energy content. Case study of the test house (built in 2012) insulated with straw bales gave the result that thermal transmittance of investigated straw bale walls was according to the minimum energy efficiency requirements set in Estonia U = 0.12 - 0.22 W/m2K (for walls).

Thermal comfort in air-conditioned buildings in hot and humid climates--why are we not getting it right?

PubMed

Sekhar, S C

2016-02-01

While there are plenty of anecdotal experiences of overcooled buildings in summer, evidence from field studies suggests that there is indeed an issue of overcooling in tropical buildings. The findings suggest that overcooled buildings are not a consequence of occupant preference but more like an outcome of the HVAC system design and operation. Occupants' adaptation in overcooled indoor environments through additional clothing cannot be regarded as an effective mitigating strategy for cold thermal discomfort. In the last two decades or so, several field studies and field environmental chamber studies in the tropics provided evidence for occupants' preference for a warmer temperature with adaptation methods such as elevated air speeds. It is important to bear in mind that indoor humidity levels are not compromised as they could have an impact on the inhaled air condition that could eventually affect perceived air quality. This review article has attempted to track significant developments in our understanding of the thermal comfort issues in air-conditioned office and educational buildings in hot and humid climates in the last 25 years, primarily on occupant preference for thermal comfort in such climates. The issue of overcooled buildings, by design intent or otherwise, is discussed in some detail. Finally, the article has explored some viable adaptive thermal comfort options that show considerable promise for not only improving thermal comfort in tropical buildings but are also energy efficient and could be seen as sustainable solutions. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Refurbishment and Automation of the Thermal/Vacuum Facilities at the Goddard Space Flight Center

NASA Technical Reports Server (NTRS)

Donohue, John T.; Johnson, Chris; Ogden, Rick; Sushon, Janet

1998-01-01

The thermal/vacuum facilities located at the Goddard Space Flight Center (GSFC) have supported both manned and unmanned space flight since the 1960s. Of the 11 facilities, currently 10 of the systems are scheduled for refurbishment and/or replacement as part of a 5-year implementation. Expected return on investment includes the reduction in test schedules, improvements in the safety of facility operations, reduction in the complexity of a test and the reduction in personnel support required for a test. Additionally, GSFC will become a global resource renowned for expertise in thermal engineering, mechanical engineering and for the automation of thermal/vacuum facilities and thermal/vacuum tests. Automation of the thermal/vacuum facilities includes the utilization of Programmable Logic Controllers (PLCs) and the use of Supervisory Control and Data Acquisition (SCADA) systems. These components allow the computer control and automation of mechanical components such as valves and pumps. In some cases, the chamber and chamber shroud require complete replacement while others require only mechanical component retrofit or replacement. The project of refurbishment and automation began in 1996 and has resulted in the computer control of one Facility (Facility #225) and the integration of electronically controlled devices and PLCs within several other facilities. Facility 225 has been successfully controlled by PLC and SCADA for over one year. Insignificant anomalies have occurred and were resolved with minimal impact to testing and operations. The amount of work remaining to be performed will occur over the next four to five years. Fiscal year 1998 includes the complete refurbishment of one facility, computer control of the thermal systems in two facilities, implementation of SCADA and PLC systems to support multiple facilities and the implementation of a Database server to allow efficient test management and data analysis.

External electric field driving the ultra-low thermal conductivity of silicene.

PubMed

Qin, Guangzhao; Qin, Zhenzhen; Yue, Sheng-Ying; Yan, Qing-Bo; Hu, Ming

2017-06-01

The manipulation of thermal transport is in increasing demand as heat transfer plays a critical role in a wide range of practical applications, such as efficient heat dissipation in nanoelectronics and heat conduction hindering in solid-state thermoelectrics. It is well established that the thermal transport in semiconductors and insulators (phonons) can be effectively modulated by structure engineering or materials processing. However, almost all the existing approaches involve altering the original atomic structure of materials, which would be hindered due to either irreversible structure change or limited tunability of thermal conductivity. Motivated by the inherent relationship between phonon behavior and interatomic electrostatic interaction, we comprehensively investigate the effect of external electric field, a widely used gating technique in modern electronics, on the lattice thermal conductivity (κ). Taking two-dimensional silicon (silicene) as a model, we demonstrate that by applying an electric field (E z = 0.5 V Å -1 ) the κ of silicene can be reduced to a record low value of 0.091 W m -1 K -1 , which is more than two orders of magnitude lower than that without an electric field (19.21 W m -1 K -1 ) and is even comparable to that of the best thermal insulation materials. Fundamental insights are gained from observing the electronic structures. With an electric field applied, due to the screened potential resulting from the redistributed charge density, the interactions between silicon atoms are renormalized, leading to phonon renormalization and the modulation of phonon anharmonicity through electron-phonon coupling. Our study paves the way for robustly tuning phonon transport in materials without altering the atomic structure, and would have significant impact on emerging applications, such as thermal management, nanoelectronics and thermoelectrics.

On the possibility of generation of cold and additional electric energy at thermal power stations

NASA Astrophysics Data System (ADS)

Klimenko, A. V.; Agababov, V. S.; Borisova, P. N.

2017-06-01

A layout of a cogeneration plant for centralized supply of the users with electricity and cold (ECCG plant) is presented. The basic components of the plant are an expander-generator unit (EGU) and a vapor-compression thermotransformer (VCTT). At the natural-gas-pressure-reducing stations, viz., gas-distribution stations and gas-control units, the plant is connected in parallel to a throttler and replaces the latter completely or partially. The plant operates using only the energy of the natural gas flow without burning the gas; therefore, it can be classified as a fuelless installation. The authors compare the thermodynamic efficiencies of a centralized cold supply system based on the proposed plant integrated into the thermal power station scheme and a decentralized cold supply system in which the cold is generated by electrically driven vapor-compression thermotransformers installed on the user's premises. To perform comparative analysis, the exergy efficiency was taken as the criterion since in one of the systems under investigation the electricity and the cold are generated, which are energies of different kinds. It is shown that the thermodynamic efficiency of the power supply using the proposed plant proves to be higher within the entire range of the parameters under consideration. The article presents the results of investigating the impact of the gas heating temperature upstream from the expander on the electric power of the plant, its total cooling capacity, and the cooling capacities of the heat exchangers installed downstream from the EGU and the evaporator of the VCTT. The results of calculations are discussed that show that the cold generated at the gas-control unit of a powerful thermal power station can be used for the centralized supply of the cold to the ventilation and conditioning systems of both the buildings of the power station and the neighboring dwelling houses, schools, and public facilities during the summer season.

Electric Motor Thermal Management R&D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennion, Kevin

2016-06-07

Thermal management enables more efficient and cost-effective motors. This Annual Merit Review presentation describes the technical accomplishments and progress in electric motor thermal management R&D over the last year. This project supports a broad industry demand for data, analysis methods, and experimental techniques to improve and better understand motor thermal management.

Electric Motor Thermal Management

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennion, Kevin S

Thermal management enables more efficient and cost-effective motors. This Annual Merit Review presentation describes the technical accomplishments and progress in electric motor thermal management R&D over the last year. This project supports a broad industry demand for data, analysis methods, and experimental techniques to improve and better understand motor thermal management.

Impact effects and regional tectonic insights: Backstripping the Chesapeake Bay impact structure

USGS Publications Warehouse

Hayden, T.; Kominz, M.; Powars, D.S.; Edwards, L.E.; Miller, K.G.; Browning, J.V.; Kulpecz, A.A.

2008-01-01

The Chesapeake Bay impact structure is a ca. 35.4 Ma crater located on the eastern seaboard of North America. Deposition returned to normal shortly after impact, resulting in a unique record of both impact-related and subsequent passive margin sedimentation. We use backstripping to show that the impact strongly affected sedimentation for 7 m.y. through impact-derived crustal-scale tectonics, dominated by the effects of sediment compaction and the introduction and subsequent removal of a negative thermal anomaly instead of the expected positive thermal anomaly. After this, the area was dominated by passive margin thermal subsidence overprinted by periods of regional-scale vertical tectonic events, on the order of tens of meters. Loading due to prograding sediment bodies may have generated these events. ?? 2008 The Geological Society of America.

The Global Rise of Zero Liquid Discharge for Wastewater Management: Drivers, Technologies, and Future Directions.

PubMed

Tong, Tiezheng; Elimelech, Menachem

2016-07-05

Zero liquid discharge (ZLD)-a wastewater management strategy that eliminates liquid waste and maximizes water usage efficiency - has attracted renewed interest worldwide in recent years. Although implementation of ZLD reduces water pollution and augments water supply, the technology is constrained by high cost and intensive energy consumption. In this critical review, we discuss the drivers, incentives, technologies, and environmental impacts of ZLD. Within this framework, the global applications of ZLD in the United States and emerging economies such as China and India are examined. We highlight the evolution of ZLD from thermal- to membrane-based processes, and analyze the advantages and limitations of existing and emerging ZLD technologies. The potential environmental impacts of ZLD, notably greenhouse gas emission and generation of solid waste, are discussed and the prospects of ZLD technologies and research needs are highlighted.

Enhancing low-grade thermal energy recovery in a thermally regenerative ammonia battery using elevated temperatures.

PubMed

Zhang, Fang; LaBarge, Nicole; Yang, Wulin; Liu, Jia; Logan, Bruce E

2015-03-01

A thermally regenerative ammonia battery (TRAB) is a new approach for converting low-grade thermal energy into electricity by using an ammonia electrolyte and copper electrodes. TRAB operation at 72 °C produced a power density of 236 ± 8 Wm(-2), with a linear decrease in power to 95 ± 5 Wm(-2) at 23 °C. The improved power at higher temperatures was due to reduced electrode overpotentials and more favorable thermodynamics for the anode reaction (copper oxidation). The energy density varied with temperature and discharge rates, with a maximum of 650 Wh m(-3) at a discharge energy efficiency of 54% and a temperature of 37 °C. The energy efficiency calculated with chemical process simulation software indicated a Carnot-based efficiency of up to 13% and an overall thermal energy recovery of 0.5%. It should be possible to substantially improve these energy recoveries through optimization of electrolyte concentrations and by using improved ion-selective membranes and energy recovery systems such as heat exchangers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal engineering of FAPbI3 perovskite material via radiative thermal annealing and in situ XRD

PubMed Central

Pool, Vanessa L.; Dou, Benjia; Van Campen, Douglas G.; Klein-Stockert, Talysa R.; Barnes, Frank S.; Shaheen, Sean E.; Ahmad, Md I.; van Hest, Maikel F. A. M.; Toney, Michael F.

2017-01-01

Lead halide perovskites have emerged as successful optoelectronic materials with high photovoltaic power conversion efficiencies and low material cost. However, substantial challenges remain in the scalability, stability and fundamental understanding of the materials. Here we present the application of radiative thermal annealing, an easily scalable processing method for synthesizing formamidinium lead iodide (FAPbI3) perovskite solar absorbers. Devices fabricated from films formed via radiative thermal annealing have equivalent efficiencies to those annealed using a conventional hotplate. By coupling results from in situ X-ray diffraction using a radiative thermal annealing system with device performances, we mapped the processing phase space of FAPbI3 and corresponding device efficiencies. Our map of processing-structure-performance space suggests the commonly used FAPbI3 annealing time, 10 min at 170 °C, can be significantly reduced to 40 s at 170 °C without affecting the photovoltaic performance. The Johnson-Mehl-Avrami model was used to determine the activation energy for decomposition of FAPbI3 into PbI2. PMID:28094249

A Thermally-Regenerative Ammonia-Based Flow Battery for Electrical Energy Recovery from Waste Heat.

PubMed

Zhu, Xiuping; Rahimi, Mohammad; Gorski, Christopher A; Logan, Bruce

2016-04-21

Large amounts of low-grade waste heat (temperatures <130 °C) are released during many industrial, geothermal, and solar-based processes. Using thermally-regenerative ammonia solutions, low-grade thermal energy can be converted to electricity in battery systems. To improve reactor efficiency, a compact, ammonia-based flow battery (AFB) was developed and tested at different solution concentrations, flow rates, cell pairs, and circuit connections. The AFB achieved a maximum power density of 45 W m(-2) (15 kW m(-3) ) and an energy density of 1260 Wh manolyte (-3) , with a thermal energy efficiency of 0.7 % (5 % relative to the Carnot efficiency). The power and energy densities of the AFB were greater than those previously reported for thermoelectrochemical and salinity-gradient technologies, and the voltage or current could be increased using stacked cells. These results demonstrated that an ammonia-based flow battery is a promising technology to convert low-grade thermal energy to electricity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal engineering of FAPbI 3 perovskite material via radiative thermal annealing and in situ XRD

DOE PAGES

Pool, Vanessa L.; Dou, Benjia; Van Campen, Douglas G.; ...

2017-01-17

Lead halide perovskites have emerged as successful optoelectronic materials with high photovoltaic power conversion efficiencies and low material cost. However, substantial challenges remain in the scalability, stability and fundamental understanding of the materials. Here we present the application of radiative thermal annealing, an easily scalable processing method for synthesizing formamidinium lead iodide (FAPbI 3) perovskite solar absorbers. Devices fabricated from films formed via radiative thermal annealing have equivalent efficiencies to those annealed using a conventional hotplate. By coupling results from in situ X-ray diffraction using a radiative thermal annealing system with device performances, we mapped the processing phase space ofmore » FAPbI 3 and corresponding device efficiencies. Our map of processing-structure-performance space suggests the commonly used FAPbI 3 annealing time, 10 min at 170 degrees C, can be significantly reduced to 40 s at 170 degrees C without affecting the photovoltaic performance. Lastly, the Johnson-Mehl-Avrami model was used to determine the activation energy for decomposition of FAPbI 3 into PbI 2.« less

Rapid charging of thermal energy storage materials through plasmonic heating.

PubMed

Wang, Zhongyong; Tao, Peng; Liu, Yang; Xu, Hao; Ye, Qinxian; Hu, Hang; Song, Chengyi; Chen, Zhaoping; Shang, Wen; Deng, Tao

2014-09-01

Direct collection, conversion and storage of solar radiation as thermal energy are crucial to the efficient utilization of renewable solar energy and the reduction of global carbon footprint. This work reports a facile approach for rapid and efficient charging of thermal energy storage materials by the instant and intense photothermal effect of uniformly distributed plasmonic nanoparticles. Upon illumination with both green laser light and sunlight, the prepared plasmonic nanocomposites with volumetric ppm level of filler concentration demonstrated a faster heating rate, a higher heating temperature and a larger heating area than the conventional thermal diffusion based approach. With controlled dispersion, we further demonstrated that the light-to-heat conversion and thermal storage properties of the plasmonic nanocomposites can be fine-tuned by engineering the composition of the nanocomposites.

Hierarchically interconnected porous scaffolds for phase change materials with improved thermal conductivity and efficient solar-to-electric energy conversion.

PubMed

Yang, Jie; Yu, Peng; Tang, Li-Sheng; Bao, Rui-Ying; Liu, Zheng-Ying; Yang, Ming-Bo; Yang, Wei

2017-11-23

An ice-templating self-assembly strategy and a vacuum impregnation method were used to fabricate polyethylene glycol (PEG)/hierarchical porous scaffold composite phase change materials (PCMs). Hierarchically interconnected porous scaffolds of boron nitride (BN), with the aid of a small amount of graphene oxide (GO), endow the composite PCMs with high thermal conductivity, excellent shape-stability and efficient solar-to-electric energy conversion. The formation of a three-dimensional (3D) thermally conductive pathway in the composites contributes to improving the thermal conductivity up to 2.36 W m -1 K -1 at a relatively low content of BN (ca. 23 wt%). This work provides a route for thermally conductive and shape-stabilized composite PCMs used as energy storage materials.

Thermal Conductivity of Carbon Nanotube Composite Films

NASA Technical Reports Server (NTRS)

Ngo, Quoc; Cruden, Brett A.; Cassell, Alan M.; Walker, Megan D.; Koehne, Jessica E.; Meyyappan, M.; Li, Jun; Yang, Cary Y.

2004-01-01

State-of-the-art ICs for microprocessors routinely dissipate power densities on the order of 50 W/sq cm. This large power is due to the localized heating of ICs operating at high frequencies, and must be managed for future high-frequency microelectronic applications. Our approach involves finding new and efficient thermally conductive materials. Exploiting carbon nanotube (CNT) films and composites for their superior axial thermal conductance properties has the potential for such an application requiring efficient heat transfer. In this work, we present thermal contact resistance measurement results for CNT and CNT-Cu composite films. It is shown that Cu-filled CNT arrays enhance thermal conductance when compared to as-grown CNT arrays. Furthermore, the CNT-Cu composite material provides a mechanically robust alternative to current IC packaging technology.

Lightweight thermally efficient composite feedlines, preliminary design and evaluation. [for the space tug propulsion system

NASA Technical Reports Server (NTRS)

Spond, D. E.; Holzworth, R. E.; Hall, C. A.

1974-01-01

Six liquid hydrogen feedline design concepts were developed for the cryogenic space tug. The feedlines include composite and all-metal vacuum jacketed and non-vacuum jacketed concepts, and incorporate the latest technology developments in the areas of thermally efficient vacuum jacket end closures and standoffs, radiation shields in the vacuum annulus, thermal coatings, and lightweight dissimilar metal flanged joints. The feedline design concepts were evaluated on the basis of thermal performance, weight, cost, reliability, and reusability. It is shown that composite tubing provides improved thermal performance and reduced weight for each design concept considered. Approximately 12 kg (26 lb.) can be saved by the use of composite tubing for the LH2 feedline and the other propulsion lines in the space tug.

Rapid Charging of Thermal Energy Storage Materials through Plasmonic Heating

PubMed Central

Wang, Zhongyong; Tao, Peng; Liu, Yang; Xu, Hao; Ye, Qinxian; Hu, Hang; Song, Chengyi; Chen, Zhaoping; Shang, Wen; Deng, Tao

2014-01-01

Direct collection, conversion and storage of solar radiation as thermal energy are crucial to the efficient utilization of renewable solar energy and the reduction of global carbon footprint. This work reports a facile approach for rapid and efficient charging of thermal energy storage materials by the instant and intense photothermal effect of uniformly distributed plasmonic nanoparticles. Upon illumination with both green laser light and sunlight, the prepared plasmonic nanocomposites with volumetric ppm level of filler concentration demonstrated a faster heating rate, a higher heating temperature and a larger heating area than the conventional thermal diffusion based approach. With controlled dispersion, we further demonstrated that the light-to-heat conversion and thermal storage properties of the plasmonic nanocomposites can be fine-tuned by engineering the composition of the nanocomposites. PMID:25175717

Design of Modern Reactors for Synthesis of Thermally Expanded Graphite.

PubMed

Strativnov, Eugene V

2015-12-01

One of the most progressive trends in the development of modern science and technology is the creation of energy-efficient technologies for the synthesis of nanomaterials. Nanolayered graphite (thermally exfoliated graphite) is one of the key important nanomaterials of carbon origin. Due to its unique properties (chemical and thermal stability, ability to form without a binder, elasticity, etc.), it can be used as an effective absorber of organic substances and a material for seal manufacturing for such important industries as gas transportation and automobile. Thermally expanded graphite is a promising material for the hydrogen and nuclear energy industries. The development of thermally expanded graphite production is resisted by high specific energy consumption during its manufacturing and by some technological difficulties. Therefore, the creation of energy-efficient technology for its production is very promising.

Utilizing Radioisotope Power System Waste Heat for Spacecraft Thermal Management

NASA Technical Reports Server (NTRS)

Pantano, David R.; Dottore, Frank; Geng, Steven M.; Schrieber, Jeffrey G.; Tobery, E. Wayne; Palko, Joseph L.

2005-01-01

One of the advantages of using a Radioisotope Power System (RPS) for deep space or planetary surface missions is the readily available waste heat, which can be used to maintain electronic components within a controlled temperature range, to warm propulsion tanks and mobility actuators, and to gasify liquid propellants. Previous missions using Radioisotope Thermoelectric Generators (RTGs) dissipated a very large quantity of waste heat due to the relatively low efficiency of the thermoelectric conversion technology. The next generation RPSs, such as the 110-watt Stirling Radioisotope Generator (SRG110) will have much higher conversion efficiencies than their predecessors and therefore may require alternate approaches to transferring waste heat to the spacecraft. RTGs, with efficiencies of approx. 6 to 7% and 200 C housing surface temperatures, would need to use large and heavy radiator heat exchangers to transfer the waste heat to the internal spacecraft components. At the same time, sensitive spacecraft instruments must be shielded from the thermal radiation by using the heat exchangers or additional shields. The SRG110, with an efficiency around 22% and 50 C nominal housing surface temperature, can use the available waste heat more efficiently by more direct heat transfer methods such as heat pipes, thermal straps, or fluid loops. The lower temperatures allow the SRG110 much more flexibility to the spacecraft designers in configuring the generator without concern of overheating nearby scientific instruments, thereby eliminating the need for thermal shields. This paper will investigate using a high efficiency SRG110 for spacecraft thermal management and outline potential methods in several conceptual missions (Lunar Rover, Mars Rover, and Titan Lander) to illustrate the advantages with regard to ease of assembly, less complex interfaces, and overall mass savings.

Enhanced Charge Extraction of Li-Doped TiO2 for Efficient Thermal-Evaporated Sb2S3 Thin Film Solar Cells

PubMed Central

Lan, Chunfeng; Luo, Jingting; Lan, Huabin; Fan, Bo; Peng, Huanxin; Zhao, Jun; Sun, Huibin; Zheng, Zhuanghao; Liang, Guangxing; Fan, Ping

2018-01-01

We provided a new method to improve the efficiency of Sb2S3 thin film solar cells. The TiO2 electron transport layers were doped by lithium to improve their charge extraction properties for the thermal-evaporated Sb2S3 solar cells. The Mott-Schottky curves suggested a change of energy band and faster charge transport in the Li-doped TiO2 films. Compared with the undoped TiO2, Li-doped mesoporous TiO2 dramatically improved the photo-voltaic performance of the thermal-evaporated Sb2S3 thin film solar cells, with the average power conversion efficiency (PCE) increasing from 1.79% to 4.03%, as well as the improved open-voltage (Voc), short-circuit current (Jsc) and fill factors. The best device based on Li-doped TiO2 achieved a power conversion efficiency up to 4.42% as well as a Voc of 0.645 V, which are the highest values among the reported thermal-evaporated Sb2S3 solar cells. This study showed that Li-doping on TiO2 can effectively enhance the charge extraction properties of electron transport layers, offering a new strategy to improve the efficiency of Sb2S3-based solar cells. PMID:29495612

High efficiency direct thermal to electric energy conversion from radioisotope decay using selective emitters and spectrally tuned solar cells

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Flood, Dennis J.; Lowe, Roland A.

1993-01-01

Thermophotovoltaic (TPV) systems are attractive possibilities for direct thermal-to-electric energy conversion, but have typically required the use of black body radiators operating at high temperatures. Recent advances in both the understanding and performance of solid rare-earth oxide selective emitters make possible the use of TPV at temperatures as low as 1200K. Both selective emitter and filter system TPV systems are feasible. However, requirements on the filter system are severe in order to attain high efficiency. A thin-film of a rare-earth oxide is one method for producing an efficient, rugged selective emitter. An efficiency of 0.14 and power density of 9.2 W/KG at 1200K is calculated for a hypothetical thin-film neodymia (Nd2O3) selective emitter TPV system that uses radioisotope decay as the thermal energy source.

Research of waste heat energy efficiency for absorption heat pump recycling thermal power plant circulating water

NASA Astrophysics Data System (ADS)

Zhang, Li; Zhang, Yu; Zhou, Liansheng; E, Zhijun; Wang, Kun; Wang, Ziyue; Li, Guohao; Qu, Bin

2018-02-01

The waste heat energy efficiency for absorption heat pump recycling thermal power plant circulating water has been analyzed. After the operation of heat pump, the influences on power generation and heat generation of unit were taken into account. In the light of the characteristics of heat pump in different operation stages, the energy efficiency of heat pump was evaluated comprehensively on both sides of benefits belonging to electricity and benefits belonging to heat, which adopted the method of contrast test. Thus, the reference of energy efficiency for same type projects was provided.

The thermal impact of subsurface building structures on urban groundwater resources - A paradigmatic example.

PubMed

Epting, Jannis; Scheidler, Stefan; Affolter, Annette; Borer, Paul; Mueller, Matthias H; Egli, Lukas; García-Gil, Alejandro; Huggenberger, Peter

2017-10-15

Shallow subsurface thermal regimes in urban areas are increasingly impacted by anthropogenic activities, which include infrastructure development like underground traffic lines as well as industrial and residential subsurface buildings. In combination with the progressive use of shallow geothermal energy systems, this results in the so-called subsurface urban heat island effect. This article emphasizes the importance of considering the thermal impact of subsurface structures, which commonly is underestimated due to missing information and of reliable subsurface temperature data. Based on synthetic heat-transport models different settings of the urban environment were investigated, including: (1) hydraulic gradients and conductivities, which result in different groundwater flow velocities; (2) aquifer properties like groundwater thickness to aquitard and depth to water table; and (3) constructional features, such as building depths and thermal properties of building structures. Our results demonstrate that with rising groundwater flow velocities, the heat-load from building structures increase, whereas down-gradient groundwater temperatures decrease. Thermal impacts on subsurface resources therefore have to be related to the permeability of aquifers and hydraulic boundary conditions. In regard to the urban settings of Basel, Switzerland, flow velocities of around 1 md -1 delineate a marker where either down-gradient temperature deviations or heat-loads into the subsurface are more relevant. Furthermore, no direct thermal influence on groundwater resources should be expected for aquifers with groundwater thicknesses larger 10m and when the distance of the building structure to the groundwater table is higher than around 10m. We demonstrate that measuring temperature changes down-gradient of subsurface structures is insufficient overall to assess thermal impacts, particularly in urban areas. Moreover, in areas which are densely urbanized, and where groundwater flow velocities are low, appropriate measures for assessing thermal impacts should specifically include a quantification of heat-loads into the subsurface which result in a more diffuse thermal contamination of urban groundwater resources. Copyright © 2017 Elsevier B.V. All rights reserved.

Design and analysis on thermal adaptive clamping device for PPMgLN crystal used in solid state laser

NASA Astrophysics Data System (ADS)

Yan, Conglin; Chen, Yongliang; Zhang, Wei

2015-02-01

The quality of clamping device for PPMgLN crystal has a vital influence on the optical property of solid-state laser. It has highly requirements of work stability and environmental adaptation ability, especially the thermal adaptation under high temperature differences. To achieve thermal adaptation, structural stiffness will be unavoidably weakened. How to keep both enough stiffness and thermal adaptation as far as possible is the key design point and also difficult point. In this paper, a kind of flexible thermal release unit which can work permanent under 130+/-10°C is studied. Thermal compensation principle and flexible thermal release theory are applied. Analysis results indicate that this device can effectively decreased the thermal stress of the crystal from 85MPa to 0.66MPa. The results of the vibration resistance test on the optical axis direction of the crystal indicate that the device can provide at least 5.62N to resistant 57.2g impact vibration and 18.5g impact vibration in the side direction, well satisfied the requirements of ability to resistant 6g impact vibration.

Effect of temperature-humidity index on live performance in broiler chickens grown from 49 to 63 days of age

USDA-ARS?s Scientific Manuscript database

The thermal environment in poultry housing is a primary influence on production efficiency and live performance. Heavy broilers (body weight > 3.2 kg) typically require high ventilation rates to maintain thermal comfort and production efficiency. However, large birds are observed to pant in mild to ...

Coherent Beam Combining of Fiber Amplifiers via LOCSET (Postprint)

DTIC Science & Technology

2012-07-10

load on final optics , and atmospheric turbulence compensation [20]. More importantly, tiled array systems are being investigated for extension to...compactness, near diffraction limited beam quality, superior thermal- optical properties, and high optical to optical conversion efficiencies. Despite...including: compactness, near diffraction limited beam quality, superior thermal- optical properties, and high optical to optical conversion efficiencies

The effect of dephasing on the thermoelectric efficiency of molecular junctions.

PubMed

Zimbovskaya, Natalya A

2014-07-09

In this work we report the results of theoretical analysis of the effect of the thermal environment on the thermoelectric efficiency of molecular junctions. The environment is represented by two thermal phonon baths associated with the electrodes, which are kept at different temperatures. The analysis is carried out using the Buttiker model within the scattering matrix formalism to compute electron transmission through the system. This approach is further developed so that the dephasing parameters are expressed in terms of relevant energies, including the thermal energy, strengths of coupling between the molecular bridge and the electrodes and characteristic energies of electron-phonon interactions. It is shown that the latter significantly affect thermoelectric efficiency by destroying the coherency of electron transport through the considered system.

Controlling thermal emission with refractory epsilon-near-zero metamaterials via topological transitions

NASA Astrophysics Data System (ADS)

Dyachenko, P. N.; Molesky, S.; Petrov, A. Yu; Störmer, M.; Krekeler, T.; Lang, S.; Ritter, M.; Jacob, Z.; Eich, M.

2016-06-01

Control of thermal radiation at high temperatures is vital for waste heat recovery and for high-efficiency thermophotovoltaic (TPV) conversion. Previously, structural resonances utilizing gratings, thin film resonances, metasurfaces and photonic crystals were used to spectrally control thermal emission, often requiring lithographic structuring of the surface and causing significant angle dependence. In contrast, here, we demonstrate a refractory W-HfO2 metamaterial, which controls thermal emission through an engineered dielectric response function. The epsilon-near-zero frequency of a metamaterial and the connected optical topological transition (OTT) are adjusted to selectively enhance and suppress the thermal emission in the near-infrared spectrum, crucial for improved TPV efficiency. The near-omnidirectional and spectrally selective emitter is obtained as the emission changes due to material properties and not due to resonances or interference effects, marking a paradigm shift in thermal engineering approaches. We experimentally demonstrate the OTT in a thermally stable metamaterial at high temperatures of 1,000 °C.

Controlling thermal emission with refractory epsilon-near-zero metamaterials via topological transitions

PubMed Central

Dyachenko, P. N.; Molesky, S.; Petrov, A. Yu; Störmer, M.; Krekeler, T.; Lang, S.; Ritter, M.; Jacob, Z.; Eich, M.

2016-01-01

Control of thermal radiation at high temperatures is vital for waste heat recovery and for high-efficiency thermophotovoltaic (TPV) conversion. Previously, structural resonances utilizing gratings, thin film resonances, metasurfaces and photonic crystals were used to spectrally control thermal emission, often requiring lithographic structuring of the surface and causing significant angle dependence. In contrast, here, we demonstrate a refractory W-HfO2 metamaterial, which controls thermal emission through an engineered dielectric response function. The epsilon-near-zero frequency of a metamaterial and the connected optical topological transition (OTT) are adjusted to selectively enhance and suppress the thermal emission in the near-infrared spectrum, crucial for improved TPV efficiency. The near-omnidirectional and spectrally selective emitter is obtained as the emission changes due to material properties and not due to resonances or interference effects, marking a paradigm shift in thermal engineering approaches. We experimentally demonstrate the OTT in a thermally stable metamaterial at high temperatures of 1,000 °C. PMID:27263653

Thermal fatigue as the origin of regolith on small asteroids.

PubMed

Delbo, Marco; Libourel, Guy; Wilkerson, Justin; Murdoch, Naomi; Michel, Patrick; Ramesh, K T; Ganino, Clément; Verati, Chrystele; Marchi, Simone

2014-04-10

Space missions and thermal infrared observations have shown that small asteroids (kilometre-sized or smaller) are covered by a layer of centimetre-sized or smaller particles, which constitute the regolith. Regolith generation has traditionally been attributed to the fall back of impact ejecta and by the break-up of boulders by micrometeoroid impact. Laboratory experiments and impact models, however, show that crater ejecta velocities are typically greater than several tens of centimetres per second, which corresponds to the gravitational escape velocity of kilometre-sized asteroids. Therefore, impact debris cannot be the main source of regolith on small asteroids. Here we report that thermal fatigue, a mechanism of rock weathering and fragmentation with no subsequent ejection, is the dominant process governing regolith generation on small asteroids. We find that thermal fragmentation induced by the diurnal temperature variations breaks up rocks larger than a few centimetres more quickly than do micrometeoroid impacts. Because thermal fragmentation is independent of asteroid size, this process can also contribute to regolith production on larger asteroids. Production of fresh regolith originating in thermal fatigue fragmentation may be an important process for the rejuvenation of the surfaces of near-Earth asteroids, and may explain the observed lack of low-perihelion, carbonaceous, near-Earth asteroids.

Constraining the thermal conditions of impact environments through integrated low-temperature thermochronometry and numerical modeling

NASA Astrophysics Data System (ADS)

Kelly, N. M.; Marchi, S.; Mojzsis, S. J.; Flowers, R. M.; Metcalf, J. R.; Bottke, W. F., Jr.

2017-12-01

Impacts have a significant physical and chemical influence on the surface conditions of a planet. The cratering record is used to understand a wide array of impact processes, such as the evolution of the impact flux through time. However, the relationship between impactor size and a resulting impact crater remains controversial (e.g., Bottke et al., 2016). Likewise, small variations in the impact velocity are known to significantly affect the thermal-mechanical disturbances in the aftermath of a collision. Development of more robust numerical models for impact cratering has implications for how we evaluate the disruptive capabilities of impact events, including the extent and duration of thermal anomalies, the volume of ejected material, and the resulting landscape of impacted environments. To address uncertainties in crater scaling relationships, we present an approach and methodology that integrates numerical modeling of the thermal evolution of terrestrial impact craters with low-temperature, (U-Th)/He thermochronometry. The approach uses time-temperature (t-T) paths of crust within an impact crater, generated from numerical simulations of an impact. These t-T paths are then used in forward models to predict the resetting behavior of (U-Th)/He ages in the mineral chronometers apatite and zircon. Differences between the predicted and measured (U-Th)/He ages from a modeled terrestrial impact crater can then be used to evaluate parameters in the original numerical simulations, and refine the crater scaling relationships. We expect our methodology to additionally inform our interpretation of impact products, such as lunar impact breccias and meteorites, providing robust constraints on their thermal histories. In addition, the method is ideal for sample return mission planning - robust "prediction" of ages we expect from a given impact environment enhances our ability to target sampling sites on the Moon, Mars or other solar system bodies where impacts have strongly shaped the surface. Bottke, W.F., Vokrouhlicky, D., Ghent, B., et al. (2016). 47th LPSC, Abstract #2036.

The short-term health and psychosocial impacts of domestic energy efficiency investments in low-income areas: a controlled before and after study.

PubMed

Grey, Charlotte N B; Jiang, Shiyu; Nascimento, Christina; Rodgers, Sarah E; Johnson, Rhodri; Lyons, Ronan A; Poortinga, Wouter

2017-01-31

Research suggests that living in fuel poverty and cold homes contributes to poor physical and mental health, and that interventions targeted at those living in poor quality housing may lead to health improvements. However, little is known about the socio-economic intermediaries and processes that contribute to better health. This study examined the relationship between energy efficiency investments to homes in low-income areas and mental and physical health of residents, as well as a number of psychosocial outcomes likely to be part of the complex relationship between energy efficiency measures and health outcomes. A quasi-experimental field study with a controlled pretest-posttest design was conducted (intervention n = 364; control n = 418) to investigate the short-term health and psychosocial impacts of a domestic energy efficiency programme that took place across Wales between 2013 and 2015. Survey data were collected in the winters before and after installation of energy efficiency measures, including external wall insulation. The study used a multilevel modelling repeated measures approach to analyse the data. The energy efficiency programme was not associated with improvements in physical and mental health (using the SF-12v2 physical and mental health composite scales) or reductions in self-reported respiratory and asthma symptoms. However, the programme was associated with improved subjective wellbeing (B = 0.38, 95% CI 0.12 to 0.65), as well as improvements in a number of psychosocial outcomes, including increased thermal satisfaction (OR = 3.83, 95% CI 2.40 to 5.90), reduced reports of putting up with feeling cold to save heating costs (OR = 0.49, CI = 0.25 to 0.94), fewer financial difficulties (B = -0.15, 95% CI -0.25 to -0.05), and reduced social isolation (OR = 0.32, 95% CI 0.13 to 0.77). The study showed that investing in energy efficiency in low-income communities does not lead to self-reported health improvements in the short term. However, investments increased subjective wellbeing and were linked to a number of psychosocial intermediaries that are conducive to better health. It is likely that better living conditions contribute to improvements in health outcomes in the longer term. Better understanding of the impacts on recipients of energy efficiency schemes, could improve targeting of future fuel poverty policies.

Increasing Black Hole Feedback-induced Quenching with Anisotropic Thermal Conduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kannan, Rahul; Vogelsberger, Mark; Pfrommer, Christoph

Feedback from central supermassive black holes is often invoked to explain the low star formation rates (SFRs) in the massive galaxies at the centers of galaxy clusters. However, the detailed physics of the coupling of the injected feedback energy with the intracluster medium (ICM) is still unclear. Using high-resolution magnetohydrodynamic cosmological simulations of galaxy cluster formation, we investigate the role of anisotropic thermal conduction in shaping the thermodynamic structure of clusters, and in particular, in modifying the impact of black hole feedback. Stratified anisotropically conducting plasmas are formally always unstable, and thus more prone to mixing, an expectation borne outmore » by our results. The increased mixing efficiently isotropizes the injected feedback energy, which in turn significantly improves the coupling between the feedback energy and the ICM. This facilitates an earlier disruption of the cool-core, reduces the SFR by more than an order of magnitude, and results in earlier quenching despite an overall lower amount of feedback energy injected into the cluster core. With conduction, the metallicity gradients and dispersions are lowered, aligning them better with observational constraints. These results highlight the important role of thermal conduction in establishing and maintaining the quiescence of massive galaxies.« less

Influence of Temperature on Nanosecond Pulse Amplification in Thulium Doped Fiber Lasers

NASA Astrophysics Data System (ADS)

Abdulfattah, Ali; Gausmann, Stefan; Sincore, Alex; Bradford, Joshua; Bodnar, Nathan; Cook, Justin; Shah, Lawrence; Richardson, Martin

2018-05-01

Thulium silica doped fiber (TDF) lasers are becoming important laser sources in both research and applications in industry. A key element of all high-power lasers is thermal management and its impact on laser performance. This is particularly important in TDF lasers, which utilize an unusual cross-relation pumping scheme, and are optically less efficient than other types of fiber lasers. The present work describes an experimental investigation of thermal management in a high power, high repetition-rate, pulsed Thulium (Tm) fiber laser. A tunable nanosecond TDF laser system across the 1838 nm – 1948 nm wavelength range, has been built to propagate 2μm signal seed pulses into a TDF amplifier, comprising a polarized large mode area (PLMA) thulium fiber (TDF) with a 793nm laser diode pump source. The PLMA TDF amplifier is thermally managed by a separately controlled cooling system with a temperature varied from 12°C to 36°C. The maximum output energy (∼400 μJ), of the system is achieved at 12°C at 1947 nm wavelength with ∼32 W of absorbed pump power at 20 kHz with a pulse duration of ∼ 74 ns.

Impact of thermal energy storage properties on solar dynamic space power conversion system mass

NASA Technical Reports Server (NTRS)

Juhasz, Albert J.; Coles-Hamilton, Carolyn E.; Lacy, Dovie E.

1987-01-01

A 16 parameter solar concentrator/heat receiver mass model is used in conjunction with Stirling and Brayton Power Conversion System (PCS) performance and mass computer codes to determine the effect of thermal energy storage (TES) material property changes on overall PCS mass as a function of steady state electrical power output. Included in the PCS mass model are component masses as a function of thermal power for: concentrator, heat receiver, heat exchangers (source unless integral with heat receiver, heat sink, regenerator), heat engine units with optional parallel redundancy, power conditioning and control (PC and C), PC and C radiator, main radiator, and structure. Critical TES properties are: melting temperature, heat of fusion, density of the liquid phase, and the ratio of solid-to-liquid density. Preliminary results indicate that even though overalll system efficiency increases with TES melting temperature up to 1400 K for concentrator surface accuracies of 1 mrad or better, reductions in the overall system mass beyond that achievable with lithium fluoride (LiF) can be accomplished only if the heat of fusion is at least 800 kJ/kg and the liquid density is comparable to that of LiF (1880 kg/cu m.

Impact of thermal energy storage properties on solar dynamic space power conversion system mass

NASA Technical Reports Server (NTRS)

Juhasz, Albert J.; Coles-Hamilton, Carolyn E.; Lacy, Dovie E.

1987-01-01

A 16 parameter solar concentrator/heat receiver mass model is used in conjunction with Stirling and Brayton Power Conversion System (PCS) performance and mass computer codes to determine the effect of thermal energy storage (TES) material property changes on overall PCS mass as a function of steady state electrical power output. Included in the PCS mass model are component masses as a function of thermal power for: concentrator, heat receiver, heat exchangers (source unless integral with heat receiver, heat sink, regenerator), heat engine units with optional parallel redundancy, power conditioning and control (PC and C), PC and C radiator, main radiator, and structure. Critical TES properties are: melting temperature, heat of fusion, density of the liquid phase, and the ratio of solid-to-liquid density. Preliminary results indicate that even though overall system efficiency increases with TES melting temperature up to 1400 K for concentrator surface accuracies of 1 mrad or better, reductions in the overall system mass beyond that achievable with lithium fluoride (LiF) can be accomplished only if the heat of fusion is at least 800 kJ/kg and the liquid density is comparable to that of LiF (1800 kg/cu m).

Experimental determination of gamma-ray discrimination in pillar-structured thermal neutron detectors under high gamma-ray flux

DOE PAGES

Shao, Qinghui; Conway, Adam M.; Voss, Lars F.; ...

2015-08-04

Silicon pillar structures filled with a neutron converter material ( 10B) are designed to have high thermal neutron detection efficiency with specific dimensions of 50 μm pillar height, 2 μm pillar diameter and 2 μm spacing between adjacent pillars. In this paper, we have demonstrated such a detector has a high neutron-to-gamma discrimination of 10 6 with a high thermal neutron detection efficiency of 39% when exposed to a high gamma-ray field of 10 9 photons/cm 2s.

Mechanical, Thermal, and Electrical Energy Storage in a Single Working Body: Electrification and Thermal Effects upon Pressure-Induced Water Intrusion-Extrusion in Nanoporous Solids.

PubMed

Grosu, Yaroslav; Mierzwa, Michał; Eroshenko, Valentine A; Pawlus, Sebastian; Chorażewski, Mirosław; Nedelec, Jean-Marie; Grolier, Jean-Pierre E

2017-03-01

This paper presents the first experimental evidence of pronounced electrification effects upon reversible cycle of forced water intrusion-extrusion in nanoporous hydrophobic materials. Recorded generation of electricity combined with high-pressure calorimetric measurements improves the energy balance of {nanoporous solid + nonwetting liquid} systems by compensating mechanical and thermal energy hysteresis in the cycle. Revealed phenomena provide a novel way of "mechanical to electrical" and/or "thermal to electrical" energy transformation with unprecedented efficiency and additionally open a perspective to increase the efficiency of numerous energy applications based on such systems taking advantage of electricity generation during operational cycle.

Efficiency of thermoelectric conversion in ferroelectric film capacitive structures

NASA Astrophysics Data System (ADS)

Volpyas, V. A.; Kozyrev, A. B.; Soldatenkov, O. I.; Tepina, E. R.

2012-06-01

Thermal heating/cooling conditions for metal-insulator-metal structures based on barium strontium titanate ferroelectric films are studied by numerical methods with the aim of their application in capacitive thermoelectric converters. A correlation between the thermal and capacitive properties of thin-film ferroelectric capacitors is considered. The time of the temperature response and the rate of variation of the capacitive properties of the metal-insulator-metal structures are determined by analyzing the dynamics of thermal processes. Thermophysical calculations are carried out that take into consideration the real electrical properties of barium strontium titanate ferroelectric films and allow estimation of thermal modulation parameters and the efficiency of capacitive thermoelectric converters on their basis.

Effect of solvent and subsequent thermal annealing on the performance of phenylenevinylene copolymer: PCBM solar cells.

PubMed

Sharma, G D; Suresh, P; Sharma, S S; Vijay, Y K; Mikroyannidis, John A

2010-02-01

The morphology of the photoactive layer used in the bulk heterojunction photovoltaic devices is crucial for efficient charge generation and their collection at the electrodes. We investigated the solvent vapor annealing and thermal annealing effect of an alternating phenylenevinylene copolymer P:PCBM blend on its morphology and optical properties. The UV-visible absorption spectroscopy shows that both solvent and thermal annealing can result in self-assembling of copolymer P to form an ordered structure, leading to enhanced absorption in the red region and hole transport enhancement. By combining the solvent and thermal annealing of the devices, the power conversion efficiency is improved. This feature was attributed to the fact that the PCBM molecules begin to diffuse into aggregates and together with the ordered copolymer P phase form bicontinuous pathways in the entire layer for efficient charge separation and transport. Furthermore, the measured photocurrent also suggests that the space charges no longer limit the values of the short circuit current (J(sc)) and fill factor (FF) for solvent-treated and thermally annealed devices. These results indicate that the higher J(sc) and PCE for the solvent-treated and thermally annealed devices can be attributed to the phase separation of active layers, which leads to a balanced carrier mobility. The overall PCE of the device based on the combination of solvent annealing and thermal annealing is about 3.7 %.

"METHOD": A tool for mechanical, electrical, thermal, and optical characterization of single lens module design

NASA Astrophysics Data System (ADS)

Besson, Pierre; Dominguez, Cesar; Voarino, Philippe; Garcia-Linares, Pablo; Weick, Clement; Lemiti, Mustapha; Baudrit, Mathieu

2015-09-01

The optical characterization and electrical performance evaluation are essential in the design and optimization of a concentrator photovoltaic system. The geometry, materials, and size of concentrator optics are diverse and different environmental conditions impact their performance. CEA has developed a new concentrator photovoltaic system characterization bench, METHOD, which enables multi-physics optimization studies. The lens and cell temperatures are controlled independently with the METHOD to study their isolated effects on the electrical and optical performance of the system. These influences can be studied in terms of their effect on optical efficiency, focal distance, spectral sensitivity, electrical efficiency, or cell current matching. Furthermore, the irradiance map of a concentrator optic can be mapped to study its variations versus the focal length or the lens temperature. The present work shows this application to analyze the performance of a Fresnel lens linking temperature to optical and electrical performance.

High-Performance Rh 2 P Electrocatalyst for Efficient Water Splitting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Haohong; Li, Dongguo; Tang, Yan

2017-04-05

The search for active, stable, and cost-efficient electrocatalysts for hydrogen production via water splitting could make a substantial impact on energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high-surface-area carbon (Rh2P/C) by a facile solvo-thermal approach. The Rh2P/C NCs exhibit remarkable performance for hydrogen evolution reaction and oxygen evolution reaction compared to Rh/C and Pt/C catalysts. The atomic structure of the Rh2P NCs was directly observed by annular dark-field scanning transmission electron microscopy, which revealed a phosphorus-rich outermostmore » atomic layer. Combined experimental and computational studies suggest that surface phosphorus plays a crucial role in determining the robust catalyst properties.« less

High-Performance Rh 2 P Electrocatalyst for Efficient Water Splitting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Haohong; Li, Dongguo; Tang, Yan

2017-04-05

Search for active, stable and cost-efficient electrocatalysts for hydrogen production via water splitting could make substantial impact to the energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high surface area carbon (Rh2P/C) by a facile solvo-thermal approach. The Rh2P/C NCs exhibit remarkable performance for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) compared to Rh/C and Pt/C catalysts. The atomic structure of the rhodium phosphide nanocubes was directly observed by annular dark-field scanning transmission electron microscopy (ADF-STEM),more » which revealed phosphorous-rich outermost atomic layer. Combined experimental and computational studies suggest that surface phosphorous plays crucial role in determining the robust catalyst properties.« less

Daylighting as a design and energy strategy: Overview of opportunities and conflicts

NASA Astrophysics Data System (ADS)

Selkowitz, S.

1981-06-01

The potentials and problems associated with using daylight both to improve visual performance and interior aesthetics and to reduce electrical lighting energy consumption and peak electric loads are reviewed. Use of daylighting as a design strategy is not always synonymous with effective use of daylighting as an energy-saving strategy unless both approaches are jointly pursued by the design team. Criteria for visual performance, disability and discomfort glare, historical perspectives on daylight utilization, building form as a limit to daylight penetration, beam sunlighting strategies, luminous efficacy of daylight versus efficient electric light sources, comparative thermal impacts, peak load and load management potential, and nonenergy benefits are reviewed. Although the energy benefits of daylighting can be oversold, it is concluded that in most cases a solid understanding of the energy and design issues should produce energy efficiency and pleasing working environments.

Thermal investigation on high power dfb broad area lasers at 975 nm, with 60% efficiency

NASA Astrophysics Data System (ADS)

Mostallino, R.; Garcia, M.; Deshayes, Y.; Larrue, A.; Robert, Y.; Vinet, E.; Bechou, L.; Lecomte, M.; Parillaud, O.; Krakowski, M.

2016-03-01

The demand of high power diode lasers in the range of 910-980nm is regularly growing. This kind of device for many applications, such as fiber laser pumping [1], material processing [1], solid-state laser pumping [1], defense and medical/dental. The key role of this device lies in the efficiency (𝜂𝐸) of converting input electrical power into output optical power. The high value of 𝜂𝐸 allows high power level and reduces the need in heat dissipation. The requirement of wavelength stabilization with temperature is more obvious in the case of multimode 975nm diode lasers used for pumping Yb, Er and Yb/Er co-doped solid-state lasers, due to the narrow absorption line close to this wavelength. Such spectral width property (<1 nm), combined with wavelength thermal stabilization (0.07 𝑛𝑚 • °𝐶-1), provided by a uniform distributed feedback grating (DFB) introduced by etching and re-growth process techniques, is achievable in high power diode lasers using optical feedback. This paper reports on the development of the diode laser structure and the process techniques required to write the gratings taking into account of the thermal dissipation and optical performances. Performances are particularly determined in terms of experimental electro-optical characterizations. One of the main objectives is to determine the thermal resistance of the complete assembly to ensure the mastering of the diode laser temperature for operating condition. The classical approach to determine junction temperature is based on the infrared thermal camera, the spectral measurement and the pulse electrical method. In our case, we base our measurement on the spectral measurement but this approach is not well adapted to the high power diodes laser studied. We develop a new measurement based on the pulse electrical method and using the T3STERequipment. This method is well known for electronic devices and LEDs but is weakly developed for the high power diodes laser. This crucial measurement compared to spectral one is critical for understand the thermal management of diode laser device and improve the structure based on design for reliability. To have a perfect relation between structure, and their modification, and temperature, FEM simulations are performed using COMSOL software. In this case, we can understand the impact of structure on the isothermal distribution and then reveal the sensitive zones in the diode laser. To validate the simulation, we compare the simulation results to the experimental one and develop an analytical model to determine the different contributions of the thermal heating. This paper reports on the development laser structure and the process techniques required to write the gratings. Performances are particularly characterized in terms of experimental electro-optical characterization and spectral response. The extraction of thermal resistance (Rth) is particularly difficult, because of the implicit low value (Rth ≈ 2𝐾/𝑊) and the multimodal nature of the diode laser. In such a context, thermal resistance has been measured using a dedicated equipment namely T3STER©. The results have been compared with those given by the well-known technique achieved from the spectrum of the diode laser (central wavelength variations vs temperature) that is more difficult to apply for multimodal diodes laser. The last section deals with thermal simulations based on finite elements method (FEM) modeling in order to estimate junction temperature . This study represent a significant part of the general Design for Reliability (DfR) effort carried out on such devices to produce efficient and reliable high power devices at the industrial level.

Thermal Analysis of Fluidized Bed and Fixed Bed Latent Heat Thermal Storage System

NASA Astrophysics Data System (ADS)

Beemkumar, N.; Karthikeyan, A.; Shiva Keshava Reddy, Kota; Rajesh, Kona; Anderson, A.

2017-05-01

Thermal energy storage technology is essential because its stores available energy at low cost. Objective of the work is to store the thermal energy in a most efficient method. This work is deal with thermal analysis of fluidized bed and fixed bed latent heat thermal storage (LHTS) system with different encapsulation materials (aluminium, brass and copper). D-Mannitol has been used as phase change material (PCM). Encapsulation material which is in orbicular shape with 4 inch diameter and 2 mm thickness orbicular shaped product is used. Therminol-66 is used as a heat transfer fluid (HTF). Arrangement of encapsulation material is done in two ways namely fluidized bed and fixed bed thermal storage system. Comparison was made between the performance of fixed bed and fluidized bed with different encapsulation material. It is observed that from the economical point of view aluminium in fluidized bed LHTS System has highest efficiency than copper and brass. The thermal energy storage system can be analyzed with fixed bed by varying mass flow rate of oil paves a way to find effective heat energy transfer.

Factors influencing the life cycle burdens of the recovery of energy from residual municipal waste.

PubMed

Burnley, Stephen; Coleman, Terry; Peirce, Adam

2015-05-01

A life cycle assessment was carried out to assess a selection of the factors influencing the environmental impacts and benefits of incinerating the fraction of municipal waste remaining after source-separation for reuse, recycling, composting or anaerobic digestion. The factors investigated were the extent of any metal and aggregate recovery from the bottom ash, the thermal efficiency of the process, and the conventional fuel for electricity generation displaced by the power generated. The results demonstrate that incineration has significant advantages over landfill with lower impacts from climate change, resource depletion, acidification, eutrophication human toxicity and aquatic ecotoxicity. To maximise the benefits of energy recovery, metals, particularly aluminium, should be reclaimed from the residual bottom ash and the energy recovery stage of the process should be as efficient as possible. The overall environmental benefits/burdens of energy from waste also strongly depend on the source of the power displaced by the energy from waste, with coal giving the greatest benefits and combined cycle turbines fuelled by natural gas the lowest of those considered. Regardless of the conventional power displaced incineration presents a lower environmental burden than landfill. Copyright © 2015 Elsevier Ltd. All rights reserved.

The use of salinity contrast for density difference compensation to improve the thermal recovery efficiency in high-temperature aquifer thermal energy storage systems

NASA Astrophysics Data System (ADS)

van Lopik, Jan H.; Hartog, Niels; Zaadnoordijk, Willem Jan

2016-08-01

The efficiency of heat recovery in high-temperature (>60 °C) aquifer thermal energy storage (HT-ATES) systems is limited due to the buoyancy of the injected hot water. This study investigates the potential to improve the efficiency through compensation of the density difference by increased salinity of the injected hot water for a single injection-recovery well scheme. The proposed method was tested through numerical modeling with SEAWATv4, considering seasonal HT-ATES with four consecutive injection-storage-recovery cycles. Recovery efficiencies for the consecutive cycles were investigated for six cases with three simulated scenarios: (a) regular HT-ATES, (b) HT-ATES with density difference compensation using saline water, and (c) theoretical regular HT-ATES without free thermal convection. For the reference case, in which 80 °C water was injected into a high-permeability aquifer, regular HT-ATES had an efficiency of 0.40 after four consecutive recovery cycles. The density difference compensation method resulted in an efficiency of 0.69, approximating the theoretical case (0.76). Sensitivity analysis showed that the net efficiency increase by using the density difference compensation method instead of regular HT-ATES is greater for higher aquifer hydraulic conductivity, larger temperature difference between injection water and ambient groundwater, smaller injection volume, and larger aquifer thickness. This means that density difference compensation allows the application of HT-ATES in thicker, more permeable aquifers and with larger temperatures than would be considered for regular HT-ATES systems.

Analytical evaluation of the impact of broad specification fuels on high bypass turbofan engine combustors

NASA Technical Reports Server (NTRS)

Lohmann, R. P.; Szetela, E. J.; Vranos, A.

1978-01-01

The impact of the use of broad specification fuels on the design, performance durability, emissions and operational characteristics of combustors for commercial aircraft gas turbine engines was assessed. Single stage, vorbix and lean premixed prevaporized combustors, in the JT9D and an advanced energy efficient engine cycle were evaluated when operating on Jet A and ERBS (Experimental Referee Broad Specification) fuels. Design modifications, based on criteria evolved from a literature survey, were introduced and their effectiveness at offsetting projected deficiencies resulting from the use of ERBS was estimated. The results indicate that the use of a broad specification fuel such as ERBS, will necessitate significant technology improvements and redesign if deteriorated performance, durability and emissions are to be avoided. Higher radiant heat loads are projected to seriously compromise liner life while the reduced thermal stability of ERBS will require revisions to the engine-airframe fuel system to reduce the thermal stress on the fuel. Smoke and emissions output are projected to increase with the use of broad specification fuels. While the basic geometry of the single stage and vorbix combustors are compatible with the use of ERBS, extensive redesign of the front end of the lean premixed prevaporized burner will be required to achieve satisfactory operation and optimum emissions.

Impact of Groundwater Flow and Energy Load on Multiple Borehole Heat Exchangers.

PubMed

Dehkordi, S Emad; Schincariol, Robert A; Olofsson, Bo

2015-01-01

The effect of array configuration, that is, number, layout, and spacing, on the performance of multiple borehole heat exchangers (BHEs) is generally known under the assumption of fully conductive transport. The effect of groundwater flow on BHE performance is also well established, but most commonly for single BHEs. In multiple-BHE systems the effect of groundwater advection can be more complicated due to the induced thermal interference between the boreholes. To ascertain the influence of groundwater flow and borehole arrangement, this study investigates single- and multi-BHE systems of various configurations. Moreover, the influence of energy load balance is also examined. The results from corresponding cases with and without groundwater flow as well as balanced and unbalanced energy loads are cross-compared. The groundwater flux value, 10(-7) m/s, is chosen based on the findings of previous studies on groundwater flow interaction with BHEs and thermal response tests. It is observed that multi-BHE systems with balanced loads are less sensitive to array configuration attributes and groundwater flow, in the long-term. Conversely, multi-BHE systems with unbalanced loads are influenced by borehole array configuration as well as groundwater flow; these effects become more pronounced with time, unlike when the load is balanced. Groundwater flow has more influence on stabilizing loop temperatures, compared to array characteristics. Although borehole thermal energy storage (BTES) systems have a balanced energy load function, preliminary investigation on their efficiency shows a negative impact by groundwater which is due to their dependency on high temperature gradients between the boreholes and surroundings. © 2014, National Ground Water Association.

The spectral effects of subsolidus reduction of olivine and pyroxene

NASA Technical Reports Server (NTRS)

Britt, D. T.

1993-01-01

The surfaces of atmosphereless bodies are subjected to a variety of chemical, thermal, accretionary, and shock processes related to their regolith environment. These processes are responsible for a number of alterations that occur in regoliths. Alterations include particle size commutation, implantation of solar wind gases, formation of agglutinates, spectral darkening, and, in the lunar case, the development of the very strong red continuum slope in the visible and near infrared spectra. A great deal of work has pointed to the role of agglutinates as the principal agent for darkening and reddening the lunar soil. The measures of regolith maturity are strongly linked to the accumulation of agglutinates. Recent work has suggested that the finest fractions of agglutinitic glass are major source of the spectral red slope. In particular, the red slope is most strongly associated with the agglutinitic glasses that are rich in blebs of sub-micron sized metal particles. It is thought that these metal particles, because of their size and scattering efficiently relative to the wavelength of light, are responsible for the red continuum slope. This fine fraction of metal particles is produced primarily by reduction of Fe(+2) from silicates. One mechanism for the reduction process is the reaction of solar implanted wind protons with the regolith soil during impact events. In this case the presence of hydrogen creates a reducing environment and the thermal pulse from the impact greatly speeds the reaction kinetics. To explore other reducing and thermal environments a series of experiments were done using samples in evacuated capsules buffered by Tantalum and heated to subsolidus temperatures.

Thermal analysis of cylindrical natural-gas steam reformer for 5 kW PEMFC

NASA Astrophysics Data System (ADS)

Jo, Taehyun; Han, Junhee; Koo, Bonchan; Lee, Dohyung

2016-11-01

The thermal characteristics of a natural-gas based cylindrical steam reformer coupled with a combustor are investigated for the use with a 5 kW polymer electrolyte membrane fuel cell. A reactor unit equipped with nickel-based catalysts was designed to activate the steam reforming reaction without the inclusion of high-temperature shift and low-temperature shift processes. Reactor temperature distribution and its overall thermal efficiency depend on various inlet conditions such as the equivalence ratio, the steam to carbon ratio (SCR), and the fuel distribution ratio (FDR) into the reactor and the combustor components. These experiments attempted to analyze the reformer's thermal and chemical properties through quantitative evaluation of product composition and heat exchange between the combustor and the reactor. FDR is critical factor in determining the overall performance as unbalanced fuel injection into the reactor and the combustor deteriorates overall thermal efficiency. Local temperature distribution also influences greatly on the fuel conversion rate and thermal efficiency. For the experiments, the operation conditions were set as SCR was in range of 2.5-4.0 and FDR was in 0.4-0.7 along with equivalence ratio of 0.9-1.1; optimum results were observed for FDR of 0.63 and SCR of 3.0 in the cylindrical steam reformer.

Neutron sensitivity of 6Li-based suspended foil microstrip neutron detectors using Schott Borofloat® 33 microstrip electrodes

NASA Astrophysics Data System (ADS)

Edwards, Nathaniel S.; Montag, Benjamin W.; Henson, Luke C.; Bellinger, Steven L.; Nichols, Daniel M.; Reichenberger, Michael A.; Fronk, Ryan G.; McGregor, Douglas S.

2018-06-01

6Li foils, each 75-μm thick, were positioned between a Schott Borofloat® 33 microstrip electrode and a planar drift electrode to construct suspended foil microstrip neutron detectors. MCNP6 simulations of two detector configurations, one containing a single 6Li foil and the other containing five 6Li foils, indicated expected maximum intrinsic thermal-neutron detection efficiencies of 18.36% and 54.08%, respectively. For comparison, the intrinsic thermal-neutron detection efficiency as a function of thermal-neutron beam position along the foil span was experimentally measured for both detector configurations. A non-uniform intrinsic thermal-neutron detection efficiency distribution was observed along the span of the 6Li foil(s) between the microstrip and drift electrodes. Maximum intrinsic thermal-neutron detection efficiencies of 12.58 ± 0.15% and 29.75 ± 0.26% for the single and five 6Li foils were measured, respectively. Gamma-ray rejection ratios of 6.46 × 10-5 ± 4.32 × 10-7 and 7.96 × 10-5 ± 4.65 × 10-7 were also measured, respectively, for a 137Cs exposure rate of 50 mR h-1. All measurements were conducted with the 6Li foil(s) contained within a sealed aluminum enclosure pressurized with 10 psig of P-10 gas.

Near Zero Emissions at 50 Percent Thermal Efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

None, None

2012-12-31

Detroit Diesel Corporation (DDC) has successfully completed a 10 year DOE sponsored heavy-duty truck engine program, hereafter referred to as the NZ-50 program. This program was split into two major phases. The first phase was called Near-Zero Emission at 50 Percent Thermal Efficiency, and was completed in 2007. The second phase was initiated in 2006, and this phase was named Advancements in Engine Combustion Systems to Enable High-Efficiency Clean Combustion for Heavy-Duty Engines. This phase was completed in September, 2010. The key objectives of the NZ-50 program for this first phase were to: Quantify thermal efficiency degradation associated with reductionmore » of engine-out NOx emissions to the 2007 regulated level of ~1.1 g/hp-hr. Implement an integrated analytical/experimental development plan for improving subsystem and component capabilities in support of emerging engine technologies for emissions and thermal efficiency goals of the program. Test prototype subsystem hardware featuring technology enhancements and demonstrate effective application on a multi-cylinder, production feasible heavy-duty engine test-bed. Optimize subsystem components and engine controls (calibration) to demonstrate thermal efficiency that is in compliance with the DOE 2005 Joule milestone, meaning greater than 45% thermal efficiency at 2007 emission levels. Develop technology roadmap for meeting emission regulations of 2010 and beyond while mitigating the associated degradation in engine fuel consumption. Ultimately, develop technical prime-path for meeting the overall goal of the NZ-50 program, i.e., 50% thermal efficiency at 2010 regulated emissions. These objectives were successfully met during the course of the NZ-50 program. The most noteworthy achievements in this program are summarized as follows: Demonstrated technologies through advanced integrated experiments and analysis to achieve the technical objectives of the NZ-50 program with 50.2% equivalent thermal efficiency under EPA 2010 emissions regulations. Experimentally demonstrate brake efficiency of 48.5% at EPA 2010 emission level at single steady-state point. Analytically demonstrated additional brake efficiency benefits using advanced aftertreatment configuration concept and air system enhancement including, but not limited to, turbo-compound, variable valve actuator system, and new cylinder head redesign, thus helping to achieve the final program goals. Experimentally demonstrated EPA 2010 emissions over FTP cycles using advanced integrated engine and aftertreatment system. These aggressive thermal efficiency and emissions results were achieved by applying a robust systems technology development methodology. It used integrated analytical and experimental tools for subsystem component optimization encompassing advanced fuel injection system, increased EGR cooling capacity, combustion process optimization, and advanced aftertreatment technologies. Model based controls employing multiple input and output techniques enabled efficient integration of the various subsystems and ensured optimal performance of each system within the total engine package. . The key objective of the NZ-50 program for the second phase was to explore advancements in engine combustion systems using high-efficiency clean combustion (HECC) techniques to minimize cylinder-out emissions, targeting a 10% efficiency improvement. The most noteworthy achievements in this phase of the program are summarized as follows: Experimentally and analytically evaluated numerous air system improvements related to the turbocharger and variable valve actuation. Some of the items tested proved to be very successful and modifications to the turbine discovered in this program have since been incorporated into production hardware. The combustion system development continued with evaluation of various designs of the 2-step piston bowl. Significant improvements in engine emissions have been obtained, but fuel economy improvements have been tougher to realize. Development of a neural network control system progressed to the point that the system was fully functional and showing significant fuel economy gains in transient engine testing. Development of the QuantLogic injector with the capability of both a hollow cone spray during early injection and conventional diesel injection at later injection timings was undertaken and proved to be problematic. This injector was designed to be a key component in a PCCI combustion system, but this innovative fuel injector required significantly more development effort than this programâ's resources or timing would allow.« less

Investigation of Thermal Interface Materials Using Phase-Sensitive Transient Thermoreflectance Technique: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, X.; King, C.; DeVoto, D.

2014-08-01

With increasing power density in electronics packages/modules, thermal resistances at multiple interfaces are a bottleneck to efficient heat removal from the package. In this work, the performance of thermal interface materials such as grease, thermoplastic adhesives and diffusion-bonded interfaces are characterized using the phase-sensitive transient thermoreflectance technique. A multi-layer heat conduction model was constructed and theoretical solutions were derived to obtain the relation between phase lag and the thermal/physical properties. This technique enables simultaneous extraction of the contact resistance and bulk thermal conductivity of the TIMs. With the measurements, the bulk thermal conductivity of Dow TC-5022 thermal grease (70 tomore » 75 um bondline thickness) was 3 to 5 W/(m-K) and the contact resistance was 5 to 10 mm2-K/W. For the Btech thermoplastic material (45 to 80 μm bondline thickness), the bulk thermal conductivity was 20 to 50 W/(m-K) and the contact resistance was 2 to 5 mm2-K/W. Measurements were also conducted to quantify the thermal performance of diffusion-bonded interface for power electronics applications. Results with the diffusion-bonded sample showed that the interfacial thermal resistance is more than one order of magnitude lower than those of traditional TIMs, suggesting potential pathways to efficient thermal management.« less

Advanced Concepts for Pressure-Channel Reactors: Modularity, Performance and Safety

NASA Astrophysics Data System (ADS)

Duffey, Romney B.; Pioro, Igor L.; Kuran, Sermet

Based on an analysis of the development of advanced concepts for pressure-tube reactor technology, we adapt and adopt the pressure-tube reactor advantage of modularity, so that the subdivided core has the potential for optimization of the core, safety, fuel cycle and thermal performance independently, while retaining passive safety features. In addition, by adopting supercritical water-cooling, the logical developments from existing supercritical turbine technology and “steam” systems can be utilized. Supercritical and ultra-supercritical boilers and turbines have been operating for some time in coal-fired power plants. Using coolant outlet temperatures of about 625°C achieves operating plant thermal efficiencies in the order of 45-48%, using a direct turbine cycle. In addition, by using reheat channels, the plant has the potential to produce low-cost process heat, in amounts that are customer and market dependent. The use of reheat systems further increases the overall thermal efficiency to 55% and beyond. With the flexibility of a range of plant sizes suitable for both small (400 MWe) and large (1400 MWe) electric grids, and the ability for co-generation of electric power, process heat, and hydrogen, the concept is competitive. The choice of core power, reheat channel number and exit temperature are all set by customer and materials requirements. The pressure channel is a key technology that is needed to make use of supercritical water (SCW) in CANDU®1 reactors feasible. By optimizing the fuel bundle and fuel channel, convection and conduction assure heat removal using passive-moderator cooling. Potential for severe core damage can be almost eliminated, even without the necessity of activating the emergency-cooling systems. The small size of containment structure lends itself to a small footprint, impacts economics and building techniques. Design features related to Canadian concepts are discussed in this paper. The main conclusion is that development of SCW pressure-channel nuclear reactors is feasible and significant benefits can be expected over other thermal-energy systems.

CO2 Dissociation by Low Current Gliding Discharge in the Reverse Vortex Flow

NASA Astrophysics Data System (ADS)

Gutsol, Alexander

2012-10-01

If performed with high energy efficiency, plasma-chemical dissociation of carbon dioxide can be a way of converting and storing energy when there is an excess of electric energy, for example generated by solar elements of wind turbines. CO2 dissociation with efficiency of up to 90% was reported earlier for low pressure microwave discharge in supersonic flow. A new plasma-chemical system uses a low current gliding discharge in the reverse vortex flow of plasma gas. The system is a development of the Gliding Arc in Tornado reactor. The system was used to study dissociation of CO2 in wide ranges of the following experimental parameters: reactor pressure (15-150 kPa), discharge current (50-500 mA), gas flow rate (3-30 liters per minute), and electrode gap length (1-10 cm). Additionally, the effect of thermal energy recuperation on CO2 dissociation efficiency was tested. Plasma chemical efficiency of CO2 dissociation is very low (about 3%) in a short discharge at low pressures (about 15 kPa) when it is defined by electronic excitation. The highest efficiency (above 40%) was reached at pressures 50-70 kPa in a long discharge with thermal energy recuperation. It means that the process is controlled by thermal dissociation with subsequent effective quenching. Plasma chemical efficiency was determined from the data of chromatographic analysis and oscilloscope electric power integration, and also was checked calorimetrically by the thermal balance of the system.

Burner liner thermal-structural load modeling

NASA Technical Reports Server (NTRS)

Maffeo, R.

1986-01-01

The software package Transfer Analysis Code to Interface Thermal/Structural Problems (TRANCITS) was developed. The TRANCITS code is used to interface temperature data between thermal and structural analytical models. The use of this transfer module allows the heat transfer analyst to select the thermal mesh density and thermal analysis code best suited to solve the thermal problem and gives the same freedoms to the stress analyst, without the efficiency penalties associated with common meshes and the accuracy penalties associated with the manual transfer of thermal data.

More Efficient Solar Thermal-Energy Receiver

NASA Technical Reports Server (NTRS)

Dustin, M. O.

1987-01-01

Thermal stresses and reradiation reduced. Improved design for solar thermal-energy receiver overcomes three major deficiencies of solar dynamic receivers described in literature. Concentrator and receiver part of solar-thermal-energy system. Receiver divided into radiation section and storage section. Concentrated solar radiation falls on boiling ends of heat pipes, which transmit heat to thermal-energy-storage medium. Receiver used in number of applications to produce thermal energy directly for use or to store thermal energy for subsequent use in heat engine.

Fiber laser cleaning of metal mirror surfaces for optical diagnostic systems of the ITER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuznetsov, A. P., E-mail: APKuznetsov@mephi.ru; Alexandrova, A. S.; Buzhinsky, O. I.

2015-12-15

The results of experimental studies into efficiency of removal of films with a complex composition from metal mirrors by pulsed fiber laser irradiation are presented. It is shown that the initial reflectivity of optical elements can be restored by the selection of modes of irradiation impacting the surface with the sputtered film. Effective cleaning is performed by radiation with a power density lower than 10{sup 7} W/cm{sup 2}. The removal of contaminations at such a relatively low power density occurs in a solid phase, owing to which the thermal effect on the mirror is insignificant.

Optimization of insulation of a linear Fresnel collector

NASA Astrophysics Data System (ADS)

Ardekani, Mohammad Moghimi; Craig, Ken J.; Meyer, Josua P.

2017-06-01

This study presents a simulation based optimization study of insulation around the cavity receiver of a Linear Fresnel Collector. This optimization study focuses on minimizing heat losses from a cavity receiver (maximizing plant thermal efficiency), while minimizing insulation cross-sectional area (minimizing material cost and cavity dead load), which leads to a cheaper and thermally more efficient LFC cavity receiver.

High efficiency incandescent lighting

DOEpatents

Bermel, Peter; Ilic, Ognjen; Chan, Walker R.; Musabeyoglu, Ahmet; Cukierman, Aviv Ruben; Harradon, Michael Robert; Celanovic, Ivan; Soljacic, Marin

2014-09-02

Incandescent lighting structure. The structure includes a thermal emitter that can, but does not have to, include a first photonic crystal on its surface to tailor thermal emission coupled to, in a high-view-factor geometry, a second photonic filter selected to reflect infrared radiation back to the emitter while passing visible light. This structure is highly efficient as compared to standard incandescent light bulbs.

Advanced Solar Receivers

NASA Technical Reports Server (NTRS)

Owen, W. A.

1984-01-01

Low thermal efficiencies in solar receivers are discussed in terms of system design. It is recommended that careful attention be given to the overall thermal systems design, especially to conductive losses about the window and areas of relatively thin insulation. If the cavity design is carefully managed to insure a small, minimally reradiating aperture, the goal of a very high efficiency cavity receiver is a realistic one.

Light valve based on nonimaging optics with potential application in cold climate greenhouses

NASA Astrophysics Data System (ADS)

Valerio, Angel A.; Mossman, Michele A.; Whitehead, Lorne A.

2014-09-01

We have evaluated a new concept for a variable light valve and thermal insulation system based on nonimaging optics. The system incorporates compound parabolic concentrators and can readily be switched between an open highly light transmissive state and a closed highly thermally insulating state. This variable light valve makes the transition between high thermal insulation and efficient light transmittance practical and may be useful in plant growth environments to provide both adequate sunlight illumination and thermal insulation as needed. We have measured light transmittance values exceeding 80% for the light valve design and achieved thermal insulation values substantially exceeding those of traditional energy efficient windows. The light valve system presented in this paper represents a potential solution for greenhouse food production in locations where greenhouses are not feasible economically due to high heating cost.

Energy demand and thermal comfort of HVAC systems with thermally activated building systems as a function of user profile

NASA Astrophysics Data System (ADS)

Pałaszyńska, Katarzyna; Bandurski, Karol; Porowski, Mieczysław

2017-11-01

Thermally Activated Building Systems (TABS) are a way to use building structure as a thermal energy storage. As a result, renewable energy sources may be used more efficiently. The paper presents numerical analysis of a HVAC system with TABS energy demand and indoor thermal comfort of a representative room in a non-residential building (governmental, commercial, educational). The purpose of analysis is to investigate the influence of a user profile on system performance. The time span of the analysis is one year - a typical meteorological year. The model was prepared using a generally accepted simulation tool - TRNSYS 17. The results help to better understand the interaction of a user profile with TABS. Therefore they are important for the development of optimal control algorithms for energy efficient buildings equipped with such systems.

Bright Photon Upconversion on Composite Organic Lanthanide Molecules through Localized Thermal Radiation.

PubMed

Ye, Huanqing; Bogdanov, Viktor; Liu, Sheng; Vajandar, Saumitra; Osipowicz, Thomas; Hernández, Ignacio; Xiong, Qihua

2017-12-07

Converting low-energy photons via thermal radiation can be a potential approach for utilizing infrared (IR) photons to improve photovoltaic efficiency. Lanthanide-containing materials have achieved great progress in IR-to-visible photon upconversion (UC). Herein, we first report bright photon, tunable wavelength UC through localized thermal radiation at the molecular scale with low excitation power density (<10 W/cm 2 ) realized on lanthanide complexes of perfluorinated organic ligands. This is enabled by engineering the pathways of nonradiative de-excitation and energy transfer in a composite of ytterbium and terbium perfluoroimidodiphosphinates. The IR-excited thermal UC and wavelength control is realized through the terbium activators sensitized by the ytterbium sensitizers having high luminescence efficiency. The metallic molecular composite thus can be a potential energy material in the use of the IR solar spectrum for thermal photovoltaic applications.

Thermal cloak-concentrator

NASA Astrophysics Data System (ADS)

Shen, Xiangying; Li, Ying; Jiang, Chaoran; Ni, Yushan; Huang, Jiping

2016-07-01

For macroscopically manipulating heat flow at will, thermal metamaterials have opened a practical way, which possesses a single function, such as either cloaking or concentrating the flow of heat even though environmental temperature varies. By developing a theory of transformation heat transfer for multiple functions, here we introduce the concept of intelligent thermal metamaterials with a dual function, which is in contrast to the existing thermal metamaterials with single functions. By assembling homogeneous isotropic materials and shape-memory alloys, we experimentally fabricate a kind of intelligent thermal metamaterials, which can automatically change from a cloak (or concentrator) to a concentrator (or cloak) when the environmental temperature changes. This work paves an efficient way for a controllable gradient of heat, and also provides guidance both for arbitrarily manipulating the flow of heat and for efficiently designing similar intelligent metamaterials in other fields.

Effect of temperature on the release of hexadecane from soil by thermal treatment.

PubMed

Merino, Jerónimo; Bucalá, Verónica

2007-05-08

A natural organic soil (2.5% of total organic carbon) was artificially contaminated with hexadecane, and thermally treated under an inert medium up to different final temperatures (150-800 degrees C) for 30 min to simulate ex situ thermal process conditions. The experiments were conducted using a complete organic soil, instead of the clays or isolated soil fractions that are commonly used. Neat and contaminated samples were separately heated to understand the impact of the soil itself and the contaminant in the release of volatiles. The soil quality as well as the quality and amount of volatile compounds generated during the process were monitored. More than 80-88% of the initial hexadecane content in the soil matrix was recovered in liquids traps after the thermal treatment, therefore the contaminant could be recovered for further recycling. The high amount of hexadecane collected without suffering chemical transformations indicated that the main mechanism for the hexadecane removal was evaporation. The analysis of the light gases released from contaminated samples indicated negligible or null hexadecane pyrolysis reaction rates, confirming that the evaporation/desorption of the contaminant are the processes that governed the removal of the contaminant from the soil. For the soil tested, of a relatively low surface area, good removal efficiencies (higher than 99.9%) were detected at about 300 degrees C, being higher temperatures not necessary to significantly improve the contamination removal.

Absolute efficiency calibration of 6LiF-based solid state thermal neutron detectors

NASA Astrophysics Data System (ADS)

Finocchiaro, Paolo; Cosentino, Luigi; Lo Meo, Sergio; Nolte, Ralf; Radeck, Desiree

2018-03-01

The demand for new thermal neutron detectors as an alternative to 3He tubes in research, industrial, safety and homeland security applications, is growing. These needs have triggered research and development activities about new generations of thermal neutron detectors, characterized by reasonable efficiency and gamma rejection comparable to 3He tubes. In this paper we show the state of the art of a promising low-cost technique, based on commercial solid state silicon detectors coupled with thin neutron converter layers of 6LiF deposited onto carbon fiber substrates. A few configurations were studied with the GEANT4 simulation code, and the intrinsic efficiency of the corresponding detectors was calibrated at the PTB Thermal Neutron Calibration Facility. The results show that the measured intrinsic detection efficiency is well reproduced by the simulations, therefore validating the simulation tool in view of new designs. These neutron detectors have also been tested at neutron beam facilities like ISIS (Rutherford Appleton Laboratory, UK) and n_TOF (CERN) where a few samples are already in operation for beam flux and 2D profile measurements. Forthcoming applications are foreseen for the online monitoring of spent nuclear fuel casks in interim storage sites.

Numerical Analysis of the Temperature Impact on Performance of GaN-Based 460-nm Light-Emitting Diode.

PubMed

Tawfik, Wael Z; Lee, June Key

2018-03-01

The influence of temperature on the characteristics of a GaN-based 460-nm light-emitting diode (LED) prepared on sapphire substrate was simulated using the SiLENSe and SpeCLED software programs. High temperatures impose negative effects on the performance of GaN-based LEDs. As the temperature increases, electrons acquire higher thermal energies, and therefore LEDs may suffer more from high-current loss mechanisms, which in turn causes a reduction in the radiative recombination rate in the active region. The internal quantum efficiency was reduced by about 24% at a current density of 35 A/cm2, and the electroluminescence spectral peak wavelength was redshifted. The LED operated at 260 K and exhibited its highest light output power of ~317.5 mW at a maximum injection current of 350 mA, compared to 212.2 mW for an LED operated at 400 K. However, increasing temperature does not cause a droop in efficiency under high injection conditions. The peak efficiency at 1 mA of injection current decreases more rapidly by ~15% with increasing temperature from 260 to 400 K than the efficiency at high injection current of 350 mA by ~11%.

Energy efficiency façade design in high-rise apartment buildings using the calculation of solar heat transfer through windows with shading devices

NASA Astrophysics Data System (ADS)

Ha, P. T. H.

2018-04-01

The architectural design orientation at the first design stage plays a key role and has a great impact on the energy consumption of a building throughout its life-cycle. To provide designers with a simple and useful tool in quantitatively determining and simply optimizing the energy efficiency of a building at the very first stage of conceptual design, a factor namely building envelope energy efficiency (Khqnl ) should be investigated and proposed. Heat transfer through windows and other glazed areas of mezzanine floors accounts for 86% of overall thermal transfer through building envelope, so the factor Khqnl of high-rise buildings largely depends on shading solutions. The author has established tables and charts to make reference to the values of Khqnl factor in certain high-rise apartment buildings in Hanoi calculated with a software program subject to various inputs including: types and sizes of shading devices, building orientations and at different points of time to be respectively analyzed. It is possible and easier for architects to refer to these tables and charts in façade design for a higher level of energy efficiency.

Impact of Various Compression Ratio on the Compression Ignition Engine with Diesel and Jatropha Biodiesel

NASA Astrophysics Data System (ADS)

Sivaganesan, S.; Chandrasekaran, M.; Ruban, M.

2017-03-01

The present experimental investigation evaluates the effects of using blends of diesel fuel with 20% concentration of Methyl Ester of Jatropha biodiesel blended with various compression ratio. Both the diesel and biodiesel fuel blend was injected at 23º BTDC to the combustion chamber. The experiment was carried out with three different compression ratio. Biodiesel was extracted from Jatropha oil, 20% (B20) concentration is found to be best blend ratio from the earlier experimental study. The engine was maintained at various compression ratio i.e., 17.5, 16.5 and 15.5 respectively. The main objective is to obtain minimum specific fuel consumption, better efficiency and lesser Emission with different compression ratio. The results concluded that full load show an increase in efficiency when compared with diesel, highest efficiency is obtained with B20MEOJBA with compression ratio 17.5. It is noted that there is an increase in thermal efficiency as the blend ratio increases. Biodiesel blend has performance closer to diesel, but emission is reduced in all blends of B20MEOJBA compared to diesel. Thus this work focuses on the best compression ratio and suitability of biodiesel blends in diesel engine as an alternate fuel.

Characterization of Thermal and Mechanical Impact on Aluminum Honeycomb Structures

NASA Technical Reports Server (NTRS)

Robinson, Christen M.

2013-01-01

This study supports NASA Kennedy Space Center's research in the area of intelligent thermal management systems and multifunctional thermal systems. This project addresses the evaluation of the mechanical and thermal properties of metallic cellular solid (MCS) materials; those that are lightweight; high strength, tunable, multifunctional and affordable. A portion of the work includes understanding the mechanical properties of honeycomb structured cellular solids upon impact testing under ambient, water-immersed, liquid nitrogen-cooled, and liquid nitrogen-immersed conditions. Additionally, this study will address characterization techniques of the aluminum honeycomb's ability to resist multiple high-rate loadings or impacts in varying environmental conditions, using various techniques for the quantitative and qualitative determination for commercial applicability.

Development of a Solar Cell Back Sheet with Excellent UV Durability and Thermal Conductivity.

PubMed

Kang, Seong-Hwan; Choi, Jaeho; Lee, Sung-Ho; Song, Young-Hoon; Park, Jong-Se; Jung, In-Sung; Jung, Jin-Su; Kim, Chong-Yeal; Yang, O-Bong

2018-09-01

The back sheet is one of the most important materials in photovoltaic (PV) modules. It plays an important role in protecting the solar cell from the environment by preventing moisture penetration. In the back sheet, the outermost layer is composed of a polyester (PET) film to protect the PV module from moisture, and the opposite layer is composed of a TiO2 + PE material. Nowadays, PV modules are installed in the desert. Therefore, methods to improve the power generation efficiency of PV modules need to be investigated as the efficiency is affected by temperature resulting from the heat radiation effect. Using a back sheet with a high thermal conductivity, the module output efficiency can be increased as heat is efficiently dissipated. In this study, a thermally conductive film was fabricated by mixing a reference film (TiO2 + PE) and a non-metallic material, MgO, with high thermal conductivity. UV irradiation tests of the film were conducted. The thermally conductive film (TiO2 + PE + MgO) showed higher conductivity than a reference film. No visible cracks and low yellowing degree were found in thermally conductive film, confirming its excellent UV durability characteristics. The sample film was bonded to a PET layer, and a back sheet was fabricated. The yellowing of the back sheet was also analyzed after UV irradiation. In addition, mini modules with four solar cell were fabricated using the developed back sheet, and a comparative outdoor test was conducted. The results showed that power generation improved by 1.38%.

Development of an Efficient CFD Model for Nuclear Thermal Thrust Chamber Assembly Design

NASA Technical Reports Server (NTRS)

Cheng, Gary; Ito, Yasushi; Ross, Doug; Chen, Yen-Sen; Wang, Ten-See

2007-01-01

The objective of this effort is to develop an efficient and accurate computational methodology to predict both detailed thermo-fluid environments and global characteristics of the internal ballistics for a hypothetical solid-core nuclear thermal thrust chamber assembly (NTTCA). Several numerical and multi-physics thermo-fluid models, such as real fluid, chemically reacting, turbulence, conjugate heat transfer, porosity, and power generation, were incorporated into an unstructured-grid, pressure-based computational fluid dynamics solver as the underlying computational methodology. The numerical simulations of detailed thermo-fluid environment of a single flow element provide a mechanism to estimate the thermal stress and possible occurrence of the mid-section corrosion of the solid core. In addition, the numerical results of the detailed simulation were employed to fine tune the porosity model mimic the pressure drop and thermal load of the coolant flow through a single flow element. The use of the tuned porosity model enables an efficient simulation of the entire NTTCA system, and evaluating its performance during the design cycle.

Improving methane production from digested manure biofibers by mechanical and thermal alkaline pretreatment.

PubMed

Tsapekos, P; Kougias, Panagiotis G; Frison, A; Raga, R; Angelidaki, I

2016-09-01

Animal manure digestion is associated with limited methane production, due to the high content in fibers, which are hardly degradable lignocellulosic compounds. In this study, different mechanical and thermal alkaline pretreatment methods were applied to partially degradable fibers, separated from the effluent stream of biogas reactors. Batch and continuous experiments were conducted to evaluate the efficiency of these pretreatments. In batch experiments, the mechanical pretreatment improved the degradability up to 45%. Even higher efficiency was shown by applying thermal alkaline pretreatments, enhancing fibers degradability by more than 4-fold. In continuous experiments, the thermal alkaline pretreatment, using 6% NaOH at 55°C was proven to be the most efficient pretreatment method as the methane production was increased by 26%. The findings demonstrated that the methane production of the biogas plants can be increased by further exploiting the fraction of the digested manure fibers which are discarded in the post-storage tank. Copyright © 2016 Elsevier Ltd. All rights reserved.

Potential Evaluation of Solar Heat Assisted Desiccant Hybrid Air Conditioning System

NASA Astrophysics Data System (ADS)

Tran, Thien Nha; Hamamoto, Yoshinori; Akisawa, Atsushi; Kashiwagi, Takao

The solar thermal driven desiccant dehumidification-absorption cooling hybrid system has superior advantage in hot-humid climate regions. The reasonable air processing of desiccant hybrid air conditioning system and the utility of clean and free energy make the system environment friendly and energy efficient. The study investigates the performance of the desiccant dehumidification air conditioning systems with solar thermal assistant. The investigation is performed for three cases which are combinations of solar thermal and absorption cooling systems with different heat supply temperature levels. Two solar thermal systems are used in the study: the flat plate collector (FPC) and the vacuum tube with compound parabolic concentrator (CPC). The single-effect and high energy efficient double-, triple-effect LiBr-water absorption cooling cycles are considered for cooling systems. COP of desiccant hybrid air conditioning systems are determined. The evaluation of these systems is subsequently performed. The single effect absorption cooling cycle combined with the flat plate collector solar system is found to be the most energy efficient air conditioning system.

A highly efficient silole-containing dithienylethene with excellent thermal stability and fatigue resistance: a promising candidate for optical memory storage materials.

PubMed

Chan, Jacky Chi-Hung; Lam, Wai Han; Yam, Vivian Wing-Wah

2014-12-10

Diarylethene compounds are potential candidates for applications in optical memory storage systems and photoswitchable molecular devices; however, they usually show low photocycloreversion quantum yields, which result in ineffective erasure processes. Here, we present the first highly efficient photochromic silole-containing dithienylethene with excellent thermal stability and fatigue resistance. The photochemical quantum yields for photocyclization and photocycloreversion of the compound are found to be high and comparable to each other; the latter of which is rarely found in diarylethene compounds. These would give rise to highly efficient photoswitchable material with effective writing and erasure processes. Incorporation of the silole moiety as a photochromic dithienylethene backbone also was demonstrated to enhance the thermal stability of the closed form, in which the thermal backward reaction to the open form was found to be negligible even at 100 °C, which leads to a promising candidate for use as photoswitchable materials and optical memory storage.

Low Cost High Performance Nanostructured Spectrally Selective Coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Sungho

2017-04-05

Sunlight absorbing coating is a key enabling technology to achieve high-temperature high-efficiency concentrating solar power operation. A high-performance solar absorbing material must simultaneously meet all the following three stringent requirements: high thermal efficiency (usually measured by figure of merit), high-temperature durability, and oxidation resistance. The objective of this research is to employ a highly scalable process to fabricate and coat black oxide nanoparticles onto solar absorber surface to achieve ultra-high thermal efficiency. Black oxide nanoparticles have been synthesized using a facile process and coated onto absorber metal surface. The material composition, size distribution and morphology of the nanoparticle are guidedmore » by numeric modeling. Optical and thermal properties have been both modeled and measured. High temperature durability has been achieved by using nanocomposites and high temperature annealing. Mechanical durability on thermal cycling have also been investigated and optimized. This technology is promising for commercial applications in next-generation high-temperature concentration solar power (CSP) plants.« less

Simulation of Foam Impact Effects on Components of the Space Shuttle Thermal Protection System. Chapter 7

NASA Technical Reports Server (NTRS)

Fahrenthold, Eric P.; Park, Young-Keun

2004-01-01

A series of three dimensional simulations has been performed to investigate analytically the effect of insulating foam impacts on ceramic tile and reinforced carbon-carbon components of the Space Shuttle thermal protection system. The simulations employed a hybrid particle-finite element method and a parallel code developed for use in spacecraft design applications. The conclusions suggested by the numerical study are in general consistent with experiment. The results emphasize the need for additional material testing work on the dynamic mechanical response of thermal protection system materials, and additional impact experiments for use in validating computational models of impact effects.

Insights into a microwave susceptible agent for minimally invasive microwave tumor thermal therapy.

PubMed

Shi, Haitang; Liu, Tianlong; Fu, Changhui; Li, Linlin; Tan, Longfei; Wang, Jingzhuo; Ren, Xiangling; Ren, Jun; Wang, Jianxin; Meng, Xianwei

2015-03-01

This work develops a kind of sodium alginate (SA) microcapsules as microwave susceptible agents for in vivo tumor microwave thermal therapy for the first time. Due to the excellent microwave susceptible properties and low bio-toxicity, excellent therapy efficiency can be achieved with the tumor inhibiting ratio of 97.85% after one-time microwave thermal therapy with ultralow power (1.8 W, 450 MHz). Meanwhile, the mechanism of high microwave heating efficiency was confirmed via computer-simulated model in theory, demonstrating that the spatial confinement efficiency of microcapsule walls endows the inside ions with high microwave susceptible properties. This strategy offers tremendous potential applications in clinical tumor treatment with the benefits of safety, reliability, effectiveness and minimally invasiveness. Copyright © 2014 Elsevier Ltd. All rights reserved.

Characterization factors for thermal pollution in freshwater aquatic environments.

PubMed

Verones, Francesca; Hanafiah, Marlia Mohd; Pfister, Stephan; Huijbregts, Mark A J; Pelletier, Gregory J; Koehler, Annette

2010-12-15

To date the impact of thermal emissions has not been addressed in life cycle assessment despite the narrow thermal tolerance of most aquatic species. A method to derive characterization factors for the impact of cooling water discharges on aquatic ecosystems was developed which uses space and time explicit integration of fate and effects of water temperature changes. The fate factor is calculated with a 1-dimensional steady-state model and reflects the residence time of heat emissions in the river. The effect factor specifies the loss of species diversity per unit of temperature increase and is based on a species sensitivity distribution of temperature tolerance intervals for various aquatic species. As an example, time explicit characterization factors were calculated for the cooling water discharge of a nuclear power plant in Switzerland, quantifying the impact on aquatic ecosystems of the rivers Aare and Rhine. The relative importance of the impact of these cooling water discharges was compared with other impacts in life cycle assessment. We found that thermal emissions are relevant for aquatic ecosystems compared to other stressors, such as chemicals and nutrients. For the case of nuclear electricity investigated, thermal emissions contribute between 3% and over 90% to Ecosystem Quality damage.

Uncovering the intrinsic size dependence of hydriding phase transformations in nanocrystals.

PubMed

Bardhan, Rizia; Hedges, Lester O; Pint, Cary L; Javey, Ali; Whitelam, Stephen; Urban, Jeffrey J

2013-10-01

A quantitative understanding of nanocrystal phase transformations would enable more efficient energy conversion and catalysis, but has been hindered by difficulties in directly monitoring well-characterized nanoscale systems in reactive environments. We present a new in situ luminescence-based probe enabling direct quantification of nanocrystal phase transformations, applied here to the hydriding transformation of palladium nanocrystals. Our approach reveals the intrinsic kinetics and thermodynamics of nanocrystal phase transformations, eliminating complications of substrate strain, ligand effects and external signal transducers. Clear size-dependent trends emerge in nanocrystals long accepted to be bulk-like in behaviour. Statistical mechanical simulations show these trends to be a consequence of nanoconfinement of a thermally driven, first-order phase transition: near the phase boundary, critical nuclei of the new phase are comparable in size to the nanocrystal itself. Transformation rates are then unavoidably governed by nanocrystal dimensions. Our results provide a general framework for understanding how nanoconfinement fundamentally impacts broad classes of thermally driven solid-state phase transformations relevant to hydrogen storage, catalysis, batteries and fuel cells.

High-efficiency impurity activation by precise control of cooling rate during atmospheric pressure thermal plasma jet annealing of 4H-SiC wafer

NASA Astrophysics Data System (ADS)

Maruyama, Keisuke; Hanafusa, Hiroaki; Ashihara, Ryuhei; Hayashi, Shohei; Murakami, Hideki; Higashi, Seiichiro

2015-06-01

We have investigated high-temperature and rapid annealing of a silicon carbide (SiC) wafer by atmospheric pressure thermal plasma jet (TPJ) irradiation for impurity activation. To reduce the temperature gradient in the SiC wafer, a DC current preheating system and the lateral back-and-forth motion of the wafer were introduced. A maximum surface temperature of 1835 °C within 2.4 s without sample breakage was achieved, and aluminum (Al), phosphorus (P), and arsenic (As) activations in SiC were demonstrated. We have investigated precise control of heating rate (Rh) and cooling rate (Rc) during rapid annealing of P+-implanted 4H-SiC and its impact on impurity activation. No dependence of resistivity on Rh was observed, while increasing Rc significantly decreased resistivity. A minimum resistivity of 0.0025 Ω·cm and a maximum carrier concentration of 2.9 × 1020 cm-3 were obtained at Rc = 568 °C/s.

Effect of Spark Plasma Sintering on the Structure and Properties of Ti1−xZrxNiSn Half-Heusler Alloys

PubMed Central

Downie, Ruth A.; Popuri, Srinivas R.; Ning, Huanpo; Reece, Mike J.; Bos, Jan-Willem G.

2014-01-01

XNiSn (X = Ti, Zr and Hf) half-Heusler alloys have promising thermoelectric properties and are attracting enormous interest for use in waste heat recovery. In particular, multiphase behaviour has been linked to reduced lattice thermal conductivities, which enables improved energy conversion efficiencies. This manuscript describes the impact of spark plasma sintering (SPS) on the phase distributions and thermoelectric properties of Ti0.5Zr0.5NiSn based half-Heuslers. Rietveld analysis reveals small changes in composition, while measurement of the Seebeck coefficient and electrical resistivities reveals that all SPS treated samples are electron doped compared to the as-prepared samples. The lattice thermal conductivities fall between 4 W·m−1·K−1 at 350 K and 3 W·m−1·K−1 at 740 K. A maximum ZT = 0.7 at 740 K is observed in a sample with nominal Ti0.5Zr0.5NiSn composition. PMID:28788234

Multispectral optical telescope alignment testing for a cryogenic space environment

NASA Astrophysics Data System (ADS)

Newswander, Trent; Hooser, Preston; Champagne, James

2016-09-01

Multispectral space telescopes with visible to long wave infrared spectral bands provide difficult alignment challenges. The visible channels require precision in alignment and stability to provide good image quality in short wavelengths. This is most often accomplished by choosing materials with near zero thermal expansion glass or ceramic mirrors metered with carbon fiber reinforced polymer (CFRP) that are designed to have a matching thermal expansion. The IR channels are less sensitive to alignment but they often require cryogenic cooling for improved sensitivity with the reduced radiometric background. Finding efficient solutions to this difficult problem of maintaining good visible image quality at cryogenic temperatures has been explored with the building and testing of a telescope simulator. The telescope simulator is an onaxis ZERODUR® mirror, CFRP metered set of optics. Testing has been completed to accurately measure telescope optical element alignment and mirror figure changes in a cryogenic space simulated environment. Measured alignment error and mirror figure error test results are reported with a discussion of their impact on system optical performance.

Flame emissivities - alternative fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarofim, A.F.

1978-01-01

An understanding of radiative heat transfer from combustion products is needed for the prediction of thermal efficiency and heat-flux distribution in furnaces and for the estimation of the thermal punishment of the confining walls in internal combustion engines and gas turbines. The emissivities of combustion products are considered, taking into account carbon dioxide, water vapor, the overlap correction factor, soot, carbonaceous particles, the emissivities of mixtures of solids and gases, furnaces fired with low- or intermediate-Btu gas, the effect of H/C ratio on the nonluminous contribution to emissivity, the emissivity of coal combustion products, diesel engines, and gas turbines. Itmore » is found that the expected shift from petroleum-derived oils to coal-derived liquids would have only a modest effect on the nonluminous contribution to radiation in a large-scale combustor. The greatest potential impact of increases in radiation anticipated with increases in the C/H ratio of fuels is in the design of gas turbine combustors.« less

Strained hybrid perovskite thin films and their impact on the intrinsic stability of perovskite solar cells

PubMed Central

Zhao, Jingjing; Deng, Yehao; Wei, Haotong; Zheng, Xiaopeng; Yu, Zhenhua; Shao, Yuchuan; Shield, Jeffrey E.; Huang, Jinsong

2017-01-01

Organic-inorganic hybrid perovskite (OIHP) solar cells have achieved comparable efficiencies to those of commercial solar cells, although their instability hinders their commercialization. Although encapsulation techniques have been developed to protect OIHP solar cells from external stimuli such as moisture, oxygen, and ultraviolet light, understanding of the origin of the intrinsic instability of perovskite films is needed to improve their stability. We show that the OIHP films fabricated by existing methods are strained and that strain is caused by mismatched thermal expansion of perovskite films and substrates during the thermal annealing process. The polycrystalline films have compressive strain in the out-of-plane direction and in-plane tensile strain. The strain accelerates degradation of perovskite films under illumination, which can be explained by increased ion migration in strained OIHP films. This study points out an avenue to enhance the intrinsic stability of perovskite films and solar cells by reducing residual strain in perovskite films. PMID:29159287

Metallic Junction Thermoelectric Device Simulations

NASA Technical Reports Server (NTRS)

Duzik, Adam J.; Choi, Sang H.

2017-01-01

Thermoelectric junctions made of semiconductors have existed in radioisotope thermoelectric generators (RTG) for deep space missions, but are currently being adapted for terrestrial energy harvesting. Unfortunately, these devices are inefficient, operating at only 7% efficiency. This low efficiency has driven efforts to make high-figure-of-merit thermoelectric devices, which require a high electrical conductivity but a low thermal conductivity, a combination that is difficult to achieve. Lowered thermal conductivity has increased efficiency, but at the cost of power output. An alternative setup is to use metallic junctions rather than semiconductors as thermoelectric devices. Metals have orders of magnitude more electrons and electronic conductivities higher than semiconductors, but thermal conductivity is higher as well. To evaluate the viability of metallic junction thermoelectrics, a two dimensional heat transfer MATLAB simulation was constructed to calculate efficiency and power output. High Seebeck coefficient alloys, Chromel (90%Ni-10%Cr) and Constantan (55%Cu-45%Ni), produced efficiencies of around 20-30%. Parameters such as the number of layers of junctions, lateral junction density, and junction sizes for both series- and parallel-connected junctions were explored.

Thermionic/AMTEC cascade converter concept for high-efficiency space power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagan, T.H. van; Smith, J.N. Jr.; Schuller, M.

1996-12-31

This paper presents trade studies that address the use of the thermionic/AMTEC cell--a cascaded, high-efficiency, static power conversion concept that appears well-suited to space power applications. Both the thermionic and AMTEC power conversion approaches have been shown to be promising candidates for space power. Thermionics offers system compactness via modest efficiency at high heat rejection temperatures, and AMTEC offers high efficiency at modest heat rejection temperature. From a thermal viewpoint the two are ideally suited for cascaded power conversion: thermionic heat rejection and AMTEC heat source temperatures are essentially the same. In addition to realizing conversion efficiencies potentially as highmore » as 35--40%, such a cascade offers the following perceived benefits: survivability; simplicity; technology readiness; and technology growth. Mechanical approaches and thermal/electric matching criteria for integrating thermionics and AMTEC into a single conversion device are described. Focusing primarily on solar thermal space power applications, parametric trends are presented to show the performance and cost potential that should be achievable with present-day technology in cascaded thermionic/AMTEC systems.« less

GIANT IMPACT: AN EFFICIENT MECHANISM FOR THE DEVOLATILIZATION OF SUPER-EARTHS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Shang-Fei; Hori, Yasunori; Lin, D. N. C.

Mini-Neptunes and volatile-poor super-Earths coexist on adjacent orbits in proximity to host stars such as Kepler-36 and Kepler-11. Several post-formation processes have been proposed for explaining the origin of the compositional diversity between neighboring planets: mass loss via stellar XUV irradiation, degassing of accreted material, and in situ accumulation of the disk gas. Close-in planets are also likely to experience giant impacts during the advanced stage of planet formation. This study examines the possibility of transforming volatile-rich super-Earths/mini-Neptunes into volatile-depleted super-Earths through giant impacts. We present the results of three-dimensional hydrodynamic simulations of giant impacts in the accretionary and disruptivemore » regimes. Target planets are modeled with a three-layered structure composed of an iron core, silicate mantle, and hydrogen/helium envelope. In the disruptive case, the giant impact can remove most of the H/He atmosphere immediately and homogenize the refractory material in the planetary interior. In the accretionary case, the planet is able to retain more than half of the original gaseous envelope, while a compositional gradient suppresses efficient heat transfer as the planetary interior undergoes double-diffusive convection. After the giant impact, a hot and inflated planet cools and contracts slowly. The extended atmosphere enhances the mass loss via both a Parker wind induced by thermal pressure and hydrodynamic escape driven by the stellar XUV irradiation. As a result, the entire gaseous envelope is expected to be lost due to the combination of those processes in both cases. Based on our results, we propose that Kepler-36b may have been significantly devolatilized by giant impacts, while a substantial fraction of Kepler-36c’s atmosphere may remain intact. Furthermore, the stochastic nature of giant impacts may account for the observed large dispersion in the mass–radius relationship of close-in super-Earths and mini-Neptunes (at least to some extent)« less

Arcjet Testing of Micro-Meteoroid Impacted Thermal Protection Materials

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Munk, Michelle M.; Glaab, Louis J.

2013-01-01

There are several harsh space environments that could affect thermal protection systems and in turn pose risks to the atmospheric entry vehicles. These environments include micrometeoroid impact, extreme cold temperatures, and ionizing radiation during deep space cruise, all followed by atmospheric entry heating. To mitigate these risks, different thermal protection material samples were subjected to multiple tests, including hyper velocity impact, cold soak, irradiation, and arcjet testing, at various NASA facilities that simulated these environments. The materials included a variety of honeycomb packed ablative materials as well as carbon-based non-ablative thermal protection systems. The present paper describes the results of the multiple test campaign with a focus on arcjet testing of thermal protection materials. The tests showed promising results for ablative materials. However, the carbon-based non-ablative system presented some concerns regarding the potential risks to an entry vehicle. This study provides valuable information regarding the capability of various thermal protection materials to withstand harsh space environments, which is critical to sample return and planetary entry missions.

Numerical Simulations of Single Flow Element in a Nuclear Thermal Thrust Chamber

NASA Technical Reports Server (NTRS)

Cheng, Gary; Ito, Yasushi; Ross, Doug; Chen, Yen-Sen; Wang, Ten-See

2007-01-01

The objective of this effort is to develop an efficient and accurate computational methodology to predict both detailed and global thermo-fluid environments of a single now element in a hypothetical solid-core nuclear thermal thrust chamber assembly, Several numerical and multi-physics thermo-fluid models, such as chemical reactions, turbulence, conjugate heat transfer, porosity, and power generation, were incorporated into an unstructured-grid, pressure-based computational fluid dynamics solver. The numerical simulations of a single now element provide a detailed thermo-fluid environment for thermal stress estimation and insight for possible occurrence of mid-section corrosion. In addition, detailed conjugate heat transfer simulations were employed to develop the porosity models for efficient pressure drop and thermal load calculations.

Single nanowire thermal conductivity measurements by Raman thermography.

PubMed

Doerk, Gregory S; Carraro, Carlo; Maboudian, Roya

2010-08-24

A facile, rapid, and nondestructive technique for determining the thermal conductivity of individual nanowires based on Raman temperature mapping has been demonstrated. Using calculated absorption efficiencies, the thermal conductivities of single cantilevered Si nanowires grown by the vapor-liquid-solid method are measured and the results agree well with values predicted by diffuse phonon boundary scattering. As a measurement performed on the wire, thermal contact effects are avoided and ambient air convection is found to be negligible for the range of diameters measured. The method's versatility is further exemplified in the reverse measurement of a single nanowire absorption efficiency assuming diffuse phonon boundary scattering. The results presented here outline the broad utility that Raman thermography may have for future thermoelectric and photovoltaic characterization of nanostructures.

Investigation of the mixing efficiency of a chaotic micromixer using thermal lens spectrometry.

PubMed

Ghaleb, Khalil Abbas; Stephan, Khaled; Pittet, Patrick; Ferrigno, Rosaria; Georges, Joseph

2006-05-01

This work investigates the efficiency of a chaotic micromixer using thermal lens spectrometry. The outlet of the mixing device was connected to a thermal lens detection head integrating the probe beam optical fibers and the sample capillary. The chaotic micromixer consisted of a Y-shaped poly(dimethylsiloxane) (PDMS) microchip in which ribbed herringbone microstructures were etched on the floor of the main channel. Due to the solvent composition dependence of the thermal lens response, the photothermal method was shown to be highly sensitive to nonhomogeneous mixing compared to fluorescence detection. The apparatus was applied to the determination of Fe2+ with 1,10-phenanthroline using flow injection analysis; a limit of detection of 11 microg L(-1) of iron was obtained.

Power processing and control requirements of dispersed solar thermal electric generation systems

NASA Technical Reports Server (NTRS)

Das, R. L.

1980-01-01

Power Processing and Control requirements of Dispersed Receiver Solar Thermal Electric Generation Systems are presented. Kinematic Stirling Engines, Brayton Engines and Rankine Engines are considered as prime movers. Various types of generators are considered for ac and dc link generations. It is found that ac-ac Power Conversion is not suitable for implementation at this time. It is also found that ac-dc-ac Power Conversion with a large central inverter is more efficient than ac-dc-ac Power Conversion using small dispersed inverters. Ac-link solar thermal electric plants face potential stability and synchronization problems. Research and development efforts are needed in improving component performance characteristics and generation efficiency to make Solar Thermal Electric Generation economically attractive.

An innovative sewage sludge reduction by using a combined mesophilic anaerobic and thermophilic aerobic process with thermal-alkaline treatment and sludge recirculation.

PubMed

Cho, Hyun Uk; Park, Sang Kyu; Ha, Jeong Hyub; Park, Jong Moon

2013-11-15

Lab-scale High Efficiency Digestion (HED) systems containing a Mesophilic Anaerobic Reactor (MAR), Thermophilic Aerobic Reactor (TAR), liquid/solid separation unit, and thermal-alkaline treatment were developed to evaluate the efficiencies of sludge reduction and methane production. The HED process was divided into three phases to examine the influence of sludge pretreatment and pretreated sludge recirculation using TCOD and VSS reduction, COD solubilization, and methane production. The VSS removal with a solid/liquid separation unit, sludge recirculation, and thermal-alkaline treatment drastically increased up to 95% compared to the feed concentration. In addition, the results of COD solubilization and VSS/TSS showed that the solubilization of cells and organic matters by the thermal-alkaline treatment was highly increased, which was also consistent with the SEM images. In particular, the methane production rate increased 24-fold when the feed sludge and recirculated sludge were pretreated together. Collectively, the HED experiments performed with sludge recirculation and thermal-alkaline treatment demonstrated that the HED systems can be successfully employed for highly efficient sewage sludge reduction and methane gas production. Copyright © 2013 Elsevier Ltd. All rights reserved.

Comparison of ozone and thermal hydrolysis combined with anaerobic digestion for municipal and pharmaceutical waste sludge with tetracycline resistance genes.

PubMed

Pei, Jin; Yao, Hong; Wang, Hui; Ren, Jia; Yu, Xiaohua

2016-08-01

Biosolids from wastewater treatment plant (WWTP) are environmental reservoirs of antibiotic resistance genes, which attract great concerns on their efficient treatments. Anaerobic digestion (AD) is widely used for sewage sludge treatment but its effectiveness is limited due to the slow hydrolysis. Ozone and thermal hydrolysis pre-treatment were employed to improve AD efficiency and reduce antibiotic-resistant genes in municipal and pharmaceutical waste sludge (MWS and PWS, respectively) in this study. Sludge solubilization achieved 15.75-25.09% and 14.85-33.92% after ozone and thermal hydrolysis, respectively. Both pre-treatments improved cumulative methane production and the enhancements were greater on PWS than MWS. Five tetracycline-resistant genes (tet(A), tet(G), tet(Q), tet(W), tet(X)) and one mobile element (intI1) were qPCR to assess pre-treatments. AD of pre-treated sludge reduced more tet genes than raw sludge for both ozonation and thermal hydrolysis in PWS and MWS. Thermal hydrolysis pre-treatment was more efficient than ozone for reduction after AD. Results of this study help support management options for reducing the spread of antibiotic resistance from biosolids. Copyright © 2016. Published by Elsevier Ltd.

Modification of Jupiter's Stratosphere Three Weeks After the 2009 Impact

NASA Technical Reports Server (NTRS)

Fast, Kelly E.; Kostiuk, Theodor; Livengood, Timothy A.; Hewagama, Tilak; Annen, John

2011-01-01

Infrared spectroscopy sensitive to thermal emission from Jupiter's stratosphere reveals effects persisting 23 days after the impact of a body in late July 2009. Measurements obtained on 2009 August II UT at the impact latitude of 56 S (planetocentric), using the Goddard Heterodyne Instrument for Planetary Wind and Composition mounted on the NASA Infrared Telescope Facility, reveal increased ethane abundance and the effects of aerosol opacity. An interval of reduced thermal continuum emission at 11. 744 lm is measured 60o-80 towards planetary east of the impact site, estimated to be at 3050 longitude (System Ill). Retrieved stratospheric ethane mole fraction in the near vicinity of the impact site is enhanced by up to -60% relative to quiescent regions at this latitude. Thermal continuum emission at the impact site, and somewhat west of it, is significantly enhanced in the same spectra that retrieve enhanced ethane mole fraction. Assuming that the enhanced continuum brightness near the impact site results from thermalized aerosol debris blocking contribution from the continuum formed in the upper troposphere and indicating the local temperature, then continuum emission by a haze layer can be approximated by an opaque surface inserted at the 45-60 mbar pressure level in the stratosphere in an unperturbed thermal profile, setting an upper limit on the pressure and therefore a lower limit on the altitude of the top of the impact debris at this time. The reduced continuum brightness east of the impact site can be modeled by an opaque surface near the cold tropopause, which is consistent with a lower altitude of ejecta/impactor-formed opacity or significantly lesser column density of opaque haze material. The physical extent of the observed region of reduced continuum implies a minimum average velocity of 21 m/s transporting material prograde (planetary east) from the impact.

On the practical efficiency of shape memory engines

NASA Astrophysics Data System (ADS)

McCormick, P. G.

1987-02-01

The effects of non-ideal behavior, i.e., thermal efficiencies less than perfect, on the efficiency of shape memory (SME) engines are analyzed. Account is taken of the temperature hysteresis between the forward and reverse transformation and the finite elastic compliance of the SM element and the engine. The temperature difference produced by a particular stress cycle and necessary to complete the cycle is quantified, along with the temperature penalty which arises from non-ideal behavior. The hysteresis, elastic compliance and low working strains in cycled materials are shown to yield low thermal efficiencies, e.g., 1.95 pct instead of 6.74 pct in the case of a 20 k hysteresis. Heat recycling can theoretically improve the efficiency to about 3.23 pct.

Energy Efficient Community Development in California: Chula Vista Research Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gas Technology Institute

2009-03-31

In 2007, the U.S. Department of Energy joined the California Energy Commission in funding a project to begin to examine the technical, economic and institutional (policy and regulatory) aspects of energy-efficient community development. That research project was known as the Chula Vista Research Project for the host California community that co-sponsored the initiative. The researches proved that the strategic integration of the selected and economically viable buildings energy efficiency (EE) measures, photovoltaics (PV), distributed generation (DG), and district cooling can produce significant reductions in aggregate energy consumption, peak demand and emissions, compared to the developer/builder's proposed baseline approach. However, themore » central power plant emission reductions achieved through use of the EE-DG option would increase local air emissions. The electric and natural gas utility infrastructure impacts associated with the use of the EE and EE-PV options were deemed relatively insignificant while use of the EE-DG option would result in a significant reduction of necessary electric distribution facilities to serve a large-scale development project. The results of the Chula Vista project are detailed in three separate documents: (1) Energy-Efficient Community Development in California; Chula Vista Research Project report contains a detailed description of the research effort and findings. This includes the methodologies, and tools used and the analysis of the efficiency, economic and emissions impacts of alternative energy technology and community design options for two development sites. Research topics covered included: (a) Energy supply, demand, and control technologies and related strategies for structures; (b) Application of locally available renewable energy resources including solar thermal and PV technology and on-site power generation with heat recovery; (c) Integration of local energy resources into district energy systems and existing energy utility networks; (d) Alternative land-use design and development options and their impact on energy efficiency and urban runoff, emissions and the heat island effect; and (e) Alternative transportation and mobility options and their impact on local emissions. (2) Creating Energy-Efficient Communities in California: A Reference Guide to Barriers, Solutions and Resources report provides the results of an effort to identify the most innovative existing and emerging public policy, incentive and market mechanisms that encourage investment in advanced energy technologies and enabling community design options in the State of California and the nation. The report evaluates each of these mechanisms in light of the preceding research and concludes with a set of recommended mechanisms designed for consideration by relevant California State agencies, development and finance industry associations, and municipal governments. (3) Creating Energy-Efficient Communities in California: A Technical Reference Guide to Building and Site Design report contains a set of selected commercially viable energy technology and community design options for high-efficiency, low-impact community development in California. It includes a summary of the research findings referenced above and recommendations for energy technology applications and energy-efficient development strategies for residential, commercial and institutional structures and supporting municipal infrastructure for planned communities. The document also identifies design options, technology applications and development strategies that are applicable to urban infill projects.« less

Heat Pipe Space Nuclear Reactor Design Assessment. Volume 2. Feasibility Study of Upgrading the SP-100 Heat Pipe Space Nuclear Power System.

DTIC Science & Technology

1985-08-01

system thermal -to-electric energy conversion efficiency quite high (-20-25 percent). c. Fuel system--Figure 6 compares the fuel swelling of U02 , UN... high temperature reservoir. Figure 28 shows a schematic of an AMTEC operation. The efficiency of ANTEC is calculated by: IV IV + 1 (L + C AT) + Qloss... thermal energy to electrical energy. The high efficiency and low specific mass (for large systems) are the common advantages of these active systems. In

Solar-pumped CO laser

NASA Astrophysics Data System (ADS)

Treanor, Charles E.

This paper describes a method of converting thermal radiation directly into laser radiation at a wavelength of about 5 micrometers. The working fluid for the laser operation is a mixture of carbon monoxide and argon. The source of thermal radiation is assumed to be a solar oven or electrical oven operating in the range of 2000 to 2500 K. The use of carbon monoxide as the lasing material presents the advantage that the absorbing lines can be pressure broadened to permit efficient absorption of the thermal radiation without unacceptable increases in vibrational relaxation. Estimates of the efficiency, size, and power loading of such a laser are discussed.