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Sample records for achieve efficient conversion

  1. Evaluating Energy Conversion Efficiency

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    Devices that convert solar radiation directly into storable chemical or electrical energy, have characteristic energy absorption spectrum; specifically, each of these devices has energy threshold. The conversion efficiency of generalized system that emcompasses all threshold devices is analyzed, resulting in family of curves for devices of various threshold energies operating at different temperatures.

  2. ADEPT: Efficient Power Conversion

    SciTech Connect

    2011-01-01

    ADEPT Project: In today’s increasingly electrified world, power conversion—the process of converting electricity between different currents, voltage levels, and frequencies—forms a vital link between the electronic devices we use every day and the sources of power required to run them. The 14 projects that make up ARPA-E’s ADEPT Project, short for “Agile Delivery of Electrical Power Technology,” are paving the way for more energy efficient power conversion and advancing the basic building blocks of power conversion: circuits, transistors, inductors, transformers, and capacitors.

  3. Enhanced Conversion Efficiencies in Dye-Sensitized Solar Cells Achieved through Self-Assembled Platinum(II) Metallacages

    PubMed Central

    He, Zuoli; Hou, Zhiqiang; Xing, Yonglei; Liu, Xiaobin; Yin, Xingtian; Que, Meidan; Shao, Jinyou; Que, Wenxiu; Stang, Peter J.

    2016-01-01

    Two-component self-assembly supramolecular coordination complexes with particular photo-physical property, wherein unique donors are combined with a single metal acceptor, can be utilized for many applications including in photo-devices. In this communication, we described the synthesis and characterization of two-component self-assembly supramolecular coordination complexes (SCCs) bearing triazine and porphyrin faces with promising light-harvesting properties. These complexes were obtained from the self-assembly of a 90° Pt(II) acceptor with 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPyT) or 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine (TPyP). The greatly improved conversion efficiencies of the dye-sensitized TiO2 solar cells were 6.79 and 6.08 respectively, while these SCCs were introduced into the TiO2 nanoparticle film photoanodes. In addition, the open circuit voltage (Voc) of dye-sensitized solar cells was also increased to 0.769 and 0.768 V, which could be ascribed to the inhibited interfacial charge recombination due to the addition of SCCs. PMID:27404912

  4. Enhanced Conversion Efficiencies in Dye-Sensitized Solar Cells Achieved through Self-Assembled Platinum(II) Metallacages

    NASA Astrophysics Data System (ADS)

    He, Zuoli; Hou, Zhiqiang; Xing, Yonglei; Liu, Xiaobin; Yin, Xingtian; Que, Meidan; Shao, Jinyou; Que, Wenxiu; Stang, Peter J.

    2016-07-01

    Two-component self-assembly supramolecular coordination complexes with particular photo-physical property, wherein unique donors are combined with a single metal acceptor, can be utilized for many applications including in photo-devices. In this communication, we described the synthesis and characterization of two-component self-assembly supramolecular coordination complexes (SCCs) bearing triazine and porphyrin faces with promising light-harvesting properties. These complexes were obtained from the self-assembly of a 90° Pt(II) acceptor with 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPyT) or 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine (TPyP). The greatly improved conversion efficiencies of the dye-sensitized TiO2 solar cells were 6.79 and 6.08 respectively, while these SCCs were introduced into the TiO2 nanoparticle film photoanodes. In addition, the open circuit voltage (Voc) of dye-sensitized solar cells was also increased to 0.769 and 0.768 V, which could be ascribed to the inhibited interfacial charge recombination due to the addition of SCCs.

  5. Enhanced Conversion Efficiencies in Dye-Sensitized Solar Cells Achieved through Self-Assembled Platinum(II) Metallacages.

    PubMed

    He, Zuoli; Hou, Zhiqiang; Xing, Yonglei; Liu, Xiaobin; Yin, Xingtian; Que, Meidan; Shao, Jinyou; Que, Wenxiu; Stang, Peter J

    2016-01-01

    Two-component self-assembly supramolecular coordination complexes with particular photo-physical property, wherein unique donors are combined with a single metal acceptor, can be utilized for many applications including in photo-devices. In this communication, we described the synthesis and characterization of two-component self-assembly supramolecular coordination complexes (SCCs) bearing triazine and porphyrin faces with promising light-harvesting properties. These complexes were obtained from the self-assembly of a 90° Pt(II) acceptor with 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPyT) or 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphine (TPyP). The greatly improved conversion efficiencies of the dye-sensitized TiO2 solar cells were 6.79 and 6.08 respectively, while these SCCs were introduced into the TiO2 nanoparticle film photoanodes. In addition, the open circuit voltage (Voc) of dye-sensitized solar cells was also increased to 0.769 and 0.768 V, which could be ascribed to the inhibited interfacial charge recombination due to the addition of SCCs. PMID:27404912

  6. Upside-Down Solar Cell Achieves Record Efficiencies (Fact Sheet)

    SciTech Connect

    Not Available

    2010-12-01

    The inverted metamorphic multijunction (IMM) solar cell is an exercise in efficient innovation - literally, as the technology boasted the highest demonstrated efficiency for converting sunlight into electrical energy at its debut in 2005. Scientists at the National Renewable Energy Laboratory (NREL) inverted the conventional photovoltaic (PV) structure to revolutionary effect, achieving solar conversion efficiencies of 33.8% and 40.8% under one-sun and concentrated conditions, respectively.

  7. SAFARI-1: Achieving conversion to LEU - A local challenge

    SciTech Connect

    Piani, C.S.B.

    2008-07-15

    Two years have passed since the South African Department of Minerals and Energy authorised the conversion from High Enriched Uranium (HEU) to Low Enriched Uranium (LEU) of the South African Research Reactor (SAFARI-1) and the associated fuel manufacturing at Pelindaba. The scheduling, as originally proposed, allowed approximately three years for the full conversion of the reactor, anticipating simultaneous manufacturing ability from the fuel production plant. Due to technical difficulties experienced in the conversion of the local manufacturing plant from HEU (UAl alloy) to LEU (U Silicide) and the uncertainty as to costing and scheduling of such an achievement, the conversion of SAFARI-1 based on local supply has been allocated a lower priority. The acquisition in mid-2006 of 2 LEU silicide elements of SA design, manufactured by AREVA- CERCA and irradiated as test elements in SAFARI-1 to burn-ups of {approx}65% each; was successfully accomplished within 9 cycles of irradiation each. Furthermore, four 'Hybrid' elements (AREVA-CERCA plates assembled locally at Pelindaba) are ready for irradiation and have received regulatory authorisation to load. This will enable the SAFARI-1 conversion program to continue systematically according to an agreed schedule. This paper will trace the developments of the above and reflect the current status and the rescheduled conversion phases of the reactor according to latest expectations. (author)

  8. Perfect Photon-to-Hydrogen Conversion Efficiency.

    PubMed

    Kalisman, Philip; Nakibli, Yifat; Amirav, Lilac

    2016-03-01

    We report a record 100% photon-to-hydrogen production efficiency, under visible light illumination, for the photocatalytic water-splitting reduction half-reaction. This result was accomplished by utilization of nanoparticle-based photocatalysts, composed of Pt-tipped CdSe@CdS rods, with a hydroxyl anion-radical redox couple operating as a shuttle to relay the holes. The implications of such record efficiency for the prospects of realizing practical over all water splitting and solar-to-fuel energy conversion are discussed. PMID:26788824

  9. Frequency doubling conversion efficiencies for deep space optical communications

    NASA Technical Reports Server (NTRS)

    Robinson, D. L.; Shelton, R. L.

    1987-01-01

    The theory of optical frequency doubling conversion efficiency is analyzed for the small signal input case along with the strong signal depleted input case. Angle phase matching and beam focus spot size are discussed and design trades are described which maximize conversion efficiency. Experimental conversion efficiencies from the literature, which are less than theoretical results at higher input intensities due to saturation, reconversion, and higher order processes, are applied to a case study of an optical communications link from Saturn. Double pass conversion efficiencies as high as 45 percent are expected. It is believed that even higher conversion efficiencies can be obtained using multipass conversion.

  10. Photovoltaic panel having enhanced conversion efficiency stability

    SciTech Connect

    Cannella, V. D.

    1985-10-01

    A photovoltaic panel for converting light into electrical energy has enhanced energy conversion efficiency stability. The panel includes a photovoltaic device having an active region formed from a semiconductor material which exhibits an energy conversion efficiency stability directly related to the operating temperature of the device. The panel also includes means for maintaining the operating temperature of the device upon exposure to light at an elevated temperature above the ambient temperature external to the device. The active region semiconductor material is preferably an amorphous semiconductor alloy such as, for example, an amorphous silicon alloy. The operating temperature elevating means can include a thermal insulating material such as glass wool, styrofoam, or cork applied to the back side of the device to minimize heat conduction from the device. The panel can also include an enclosure for enclosing the device having a transparent cover overlying the device to seal the enclosure and provide a still air space adjacent the device. The panel is thereby arranged to maintain the operating temperature of the device at a temperature which is from about twenty degrees Centigrade to about one hundred and fifty degrees Centigrade above the ambient temperature external to the device.

  11. High efficiency GaP power conversion for Betavoltaic applications

    NASA Technical Reports Server (NTRS)

    Sims, Paul E.; Dinetta, Louis C.; Barnett, Allen M.

    1994-01-01

    AstroPower is developing a gallium phosphide (GaP) based energy converter optimized for radio luminescent light-based power supplies. A 'two-step' or 'indirect' process is used where a phosphor is excited by radioactive decay products to produce light that is then converted to electricity by a photovoltaic energy converter. This indirect conversion of beta-radiation to electrical energy can be realized by applying recent developments in tritium based radio luminescent (RL) light sources in combination with the high conversion efficiencies that can be achieved under low illumination with low leakage, gallium phosphide based devices. This tritium to light approach is inherently safer than battery designs that incorporate high activity radionuclides because the beta particles emitted by tritium are of low average energy and are easily stopped by a thin layer of glass. GaP layers were grown by liquid phase epitaxy and p/n junction devices were fabricated and characterized for low light intensity power conversion. AstroPower has demonstrated the feasibility of the GaP based energy converter with the following key results: 23.54 percent conversion efficiency under 968 muW/sq cm 440 nm blue light, 14.59 percent conversion efficiency for 2.85 muW/sq cm 440 nm blue light, and fabrication of working 5 V array. We have also determined that at least 20 muW/sq cm optical power is available for betavoltaic power systems. Successful developments of this device is an enabling technology for low volume, safe, high voltage, milliwatt power supplies with service lifetimes in excess of 12 years.

  12. Theoretical efficiency limits for thermoradiative energy conversion

    SciTech Connect

    Strandberg, Rune

    2015-02-07

    A new method to produce electricity from heat called thermoradiative energy conversion is analyzed. The method is based on sustaining a difference in the chemical potential for electron populations above and below an energy gap and let this difference drive a current through an electric circuit. The difference in chemical potential originates from an imbalance in the excitation and de-excitation of electrons across the energy gap. The method has similarities to thermophotovoltaics and conventional photovoltaics. While photovoltaic cells absorb thermal radiation from a body with higher temperature than the cell itself, thermoradiative cells are hot during operation and emit a net outflow of photons to colder surroundings. A thermoradiative cell with an energy gap of 0.25 eV at a temperature of 500 K in surroundings at 300 K is found to have a theoretical efficiency limit of 33.2%. For a high-temperature thermoradiative cell with an energy gap of 0.4 eV, a theoretical efficiency close to 50% is found while the cell produces 1000 W/m{sup 2} has a temperature of 1000 K and is placed in surroundings with a temperature of 300 K. Some aspects related to the practical implementation of the concept are discussed and some challenges are addressed. It is, for example, obvious that there is an upper boundary for the temperature under which solid state devices can work properly over time. No conclusions are drawn with regard to such practical boundaries, because the work is aimed at establishing upper limits for ideal thermoradiative devices.

  13. Managing Conversations: The Medium for Achieving "Breakthrough" Results.

    ERIC Educational Resources Information Center

    Bolton, Robert

    1998-01-01

    Unlike traditional management development, use of conversations in coaching high-performance work teams addresses core processes of speaking and listening. Management of conversations aims to create learning that will lead to breakthroughs in team performance. (SK)

  14. Enhancing The Mode Conversion Efficiency In JET Plasmas With Multiple Mode Conversion Layers

    SciTech Connect

    Van Eester, D.; Lerche, E.; Ongena, J.; Mayoral, M.-L.; Beaumont, P.; Blackman, T.; Brennan, D.; Brett, A.; Coffey, I.; Coyne, A.; Felton, R.; Giroud, C.; Jacquet, P.; Kiptily, V.; Knipe, S.; Monakhov, I.; Noble, C.; Pangioni, L.

    2011-12-23

    The constructive interference effect described by Fuchs et al. [1] shows that the mode conversion and thereby the overall heating efficiency can be enhanced significantly when an integer number of fast wave wavelengths can be folded in between the high field side fast wave cutoff and the ion-ion hybrid layer(s) at which the ion Bernstein or ion cyclotron waves are excited. This effect was already experimentally identified in ({sup 3}He)-D plasmas [2] and was recently tested in ({sup 3}He)-H JET plasmas. The latter is an 'inverted' scenario, which differs significantly from the ({sup 3}He)-D scenarios since the mode-conversion layer is positioned between the low field side edge of the plasma and the ion-cyclotron layer of the minority {sup 3}He ions (whereas the order in which a wave entering the plasma from the low field side encounters these layers is inverted in a 'regular' scenario), and because much lower {sup 3}He concentrations are needed to achieve the mode-conversion heating regime. The presence of small amounts of {sup 4}He and D in the discharges gave rise to an additional mode conversion layer on top of the expected one associated with {sup 3}He-H, which made the interpretation of the results more complex but also more interesting: Three different regimes could be distinguished as a function of X[{sup 3}He], and the differing dynamics at the various concentrations could be traced back to the presence of these two mode conversion layers and their associated fast wave cutoffs. Whereas (1-D and 2-D) numerical modeling yields quantitative information on the RF absorptivity, recent analytical work by Kazakov [3] permits to grasp the dominant underlying wave interaction physics.

  15. Limits to Photovoltaic Energy Conversion Efficiency

    NASA Astrophysics Data System (ADS)

    Green, Martin A.

    2015-10-01

    The following sections are included: * Introduction * Photovoltaic converters: essential requirements * Thermodynamic properties of sunlight * `Top-down' thermodynamic efficiency limits * Single-cell efficiency limits * Multiple-junction devices * Other high-efficiency options * Summary * Acknowledgement * References

  16. Conversion efficiency of skutterudite-based thermoelectric modules.

    PubMed

    Salvador, James R; Cho, Jung Y; Ye, Zuxin; Moczygemba, Joshua E; Thompson, Alan J; Sharp, Jeffrey W; Koenig, Jan D; Maloney, Ryan; Thompson, Travis; Sakamoto, Jeffrey; Wang, Hsin; Wereszczak, Andrew A

    2014-06-28

    Presently, the only commercially available power generating thermoelectric (TE) modules are based on bismuth telluride (Bi2Te3) alloys and are limited to a hot side temperature of 250 °C due to the melting point of the solder interconnects and/or generally poor power generation performance above this point. For the purposes of demonstrating a TE generator or TEG with higher temperature capability, we selected skutterudite based materials to carry forward with module fabrication because these materials have adequate TE performance and are mechanically robust. We have previously reported the electrical power output for a 32 couple skutterudite TE module, a module that is type identical to ones used in a high temperature capable TEG prototype. The purpose of this previous work was to establish the expected power output of the modules as a function of varying hot and cold side temperatures. Recent upgrades to the TE module measurement system built at the Fraunhofer Institute for Physical Measurement Techniques allow for the assessment of not only the power output, as previously described, but also the thermal to electrical energy conversion efficiency. Here we report the power output and conversion efficiency of a 32 couple, high temperature skutterudite module at varying applied loading pressures and with different interface materials between the module and the heat source and sink of the test system. We demonstrate a 7% conversion efficiency at the module level when a temperature difference of 460 °C is established. Extrapolated values indicate that 7.5% is achievable when proper thermal interfaces and loading pressures are used. PMID:24830880

  17. Achieving energy efficiency during collective communications

    SciTech Connect

    Sundriyal, Vaibhav; Sosonkina, Masha; Zhang, Zhao

    2012-09-13

    Energy consumption has become a major design constraint in modern computing systems. With the advent of petaflops architectures, power-efficient software stacks have become imperative for scalability. Techniques such as dynamic voltage and frequency scaling (called DVFS) and CPU clock modulation (called throttling) are often used to reduce the power consumption of the compute nodes. To avoid significant performance losses, these techniques should be used judiciously during parallel application execution. For example, its communication phases may be good candidates to apply the DVFS and CPU throttling without incurring a considerable performance loss. They are often considered as indivisible operations although little attention is being devoted to the energy saving potential of their algorithmic steps. In this work, two important collective communication operations, all-to-all and allgather, are investigated as to their augmentation with energy saving strategies on the per-call basis. The experiments prove the viability of such a fine-grain approach. They also validate a theoretical power consumption estimate for multicore nodes proposed here. While keeping the performance loss low, the obtained energy savings were always significantly higher than those achieved when DVFS or throttling were switched on across the entire application run

  18. Single-cell concepts for obtaining photovoltaic conversion efficiency over 30 percent

    NASA Technical Reports Server (NTRS)

    Fan, John C. C.

    1985-01-01

    Although solar photovoltaic conversion efficiencies over 30 percent (one sun, AM1) can be expected for multiple-cell configurations using spectral splitting techniques, the highest practical single-cell conversion efficiency that can be attained using present concepts is estimated to be about 27-28 percent. To achieve conversion efficiencies above 30 percent using single-cell configurations it will be necessary to employ different concepts, such as spectral compression and broad-band detection. The implementation of these concepts would require major breakthroughs that are not anticipated in the near future.

  19. A high-efficiency energy conversion system

    SciTech Connect

    Belcher, A.E.

    1996-12-31

    A fundamentally new method for converting pressure into rotative motion is introduced. A historical background is given and an idealized non-turbine Brayton cycle engine and associated equations are described. Salient features are explained, together with suggested applications. Concerns over global warming, unacceptable levels of air pollution, and the need for more efficient utilization of nonrenewable energy resources, are issues which continue to plague us. The situation is further exacerbated by the possibility that underdeveloped countries, under pressure to expand their economies, might adopt power generating systems which could produce high levels of emissions. This scenario could easily develop if equipment, which once complied with stringent standards, failed to be adequately maintained through the absence of a reliable technical infrastructure. The Brayton cycle manometric engine has the potential for eliminating, or at least mitigating, many of the above issues. It is therefore of considerable importance to all populations, irrespective of demographic or economic considerations. This engine is inherently simple--the engine proper has only one moving part. It has no pistons, vanes, or other such conventional occlusive devices, yet it is a positive displacement machine. Sealing is achieved by what can best be described as a series of traveling U-tube manometers. Its construction does not require precision engineering nor the use of exotic materials, making it easy to maintain with the most rudimentary resources. Rotational velocity is low, and its normal life cycle is expected to extend to several decades. These advantages more than offset the machine`s large size. It is suited only to large and medium-scale stationary applications.

  20. Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements

    PubMed Central

    Ganeev, R. A.

    2013-01-01

    New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications. PMID:23864818

  1. High conversion efficiency ultraviolet fiber Raman oscillator--amplifier system

    SciTech Connect

    Pini, R.; Salimbeni, R.; Vannini, M.; Haider, A.F.M.Y.; Lin, C.

    1986-04-01

    High efficiency UV frequency conversion by stimulated Raman scattering in a XeCl (lambda = 308-nm) excimer laser-pumped multimode fiber is presented. The system consists of a first piece of fiber as a Stokes generator and a second as a power amplifier. Power conversion efficiencies up to 80% have been measured. Uses of fiber Raman amplifiers in the near UV are also discussed.

  2. Laser-accelerated proton conversion efficiency thickness scaling

    SciTech Connect

    Hey, D. S.; Foord, M. E.; Key, M. H.; LePape, S. L.; Mackinnon, A. J.; Patel, P. K.; Ping, Y.; Akli, K. U.; Stephens, R. B.; Bartal, T.; Beg, F. N.; Fedosejevs, R.; Friesen, H.; Tiedje, H. F.; Tsui, Y. Y.

    2009-12-15

    The conversion efficiency from laser energy into proton kinetic energy is measured with the 0.6 ps, 9x10{sup 19} W/cm{sup 2} Titan laser at the Jupiter Laser Facility as a function of target thickness in Au foils. For targets thicker than 20 {mu}m, the conversion efficiency scales approximately as 1/L, where L is the target thickness. This is explained by the domination of hot electron collisional losses over adiabatic cooling. In thinner targets, the two effects become comparable, causing the conversion efficiency to scale weaker than 1/L; the measured conversion efficiency is constant within the scatter in the data for targets between 5 and 15 {mu}m, with a peak conversion efficiency of 4% into protons with energy greater than 3 MeV. Depletion of the hydrocarbon contaminant layer is eliminated as an explanation for this plateau by using targets coated with 200 nm of ErH{sub 3} on the rear surface. The proton acceleration is modeled with the hybrid-particle in cell code LSP, which reproduced the conversion efficiency scaling observed in the data.

  3. Direct Carbon Conversion: Application to the Efficient Conversion of Fossil Fuels to Electricity

    SciTech Connect

    Cooper, J F; Cherepy, N; Berry, G; Pasternak, A; Surles, T; Steinberg, M

    2001-03-07

    We introduce a concept for efficient conversion of fossil fuels to electricity that entails the decomposition of fossil-derived hydrocarbons into carbon and hydrogen, and electrochemical conversion of these fuels in separate fuel cells. Carbon/air fuel cells have the advantages of near zero entropy change and associated heat production (allowing 100% theoretical conversion efficiency). The activities of the C fuel and CO{sub 2} product are invariant, allowing constant EMF and full utilization of fuel in single pass mode of operation. System efficiency estimates were conducted for several routes involving sequential extraction of a hydrocarbon from the fossil resource by (hydro) pyrolysis followed by thermal decomposition. The total energy conversion efficiencies of the processes were estimated to be (1) 80% for direct conversion of petroleum coke; (2) 67% HHV for CH{sub 4}; (3) 72% HHV for heavy oil (modeled using properties of decane); (4) 75.5% HHV (83% LHV) for natural gas conversion with a Rankine bottoming cycle for the H{sub 2} portion; and (5) 69% HHV for conversion of low rank coals and lignite through hydrogenation and pyrolysis of the CH{sub 4} intermediate. The cost of carbon fuel is roughly $7/GJ, based on the cost of the pyrolysis step in the industrial furnace black process. Cell hardware costs are estimated to be less than $500/kW.

  4. Achieving Energy Efficiency Through Real-Time Feedback

    SciTech Connect

    Nesse, Ronald J.

    2011-09-01

    Through the careful implementation of simple behavior change measures, opportunities exist to achieve strategic gains, including greater operational efficiencies, energy cost savings, greater tenant health and ensuing productivity and an improved brand value through sustainability messaging and achievement.

  5. A new apparatus to evaluate thermophotovoltaic conversion efficiency

    NASA Astrophysics Data System (ADS)

    Demichelis, F.; Macera, L.; Minetti-Mezzetti, E.; Tagliaferro, A.; Tresso, E.

    A new simulator for thermophotovoltaic conversion is presented. The radiator which is a black body cavity surrounded by an Al2O3 cylinder, is in a vacuum chamber. By means of an interferential filter the light of suitable wavelength is reflected onto a cell, while IR radiation is recycled through a gold mirror system. The conversion efficiency, and the location and the magnitude of energy losses in a real TPV converter can be assessed by this apparatus.

  6. Using the network to achieve energy efficiency

    SciTech Connect

    Giglio, M.

    1995-12-01

    Novell, the third largest software company in the world, has developed Netware Embedded Systems Technology (NEST). NEST will take the network deeper into non-traditional computing environments and will imbed networking into more intelligent devices. Ultimately, this will lead to energy efficiencies in the office. NEST can make point-of-sale terminals, alarm systems, televisions, traffic controls, printers, lights, fax machines, copiers, HVAC controls, PBX machines, etc., either intelligent or more intelligent than they are currently. The mission statement for this particular group is to integrate over 30 million new intelligent devices into the workplace and the home with Novell networks by 1997. Computing trends have progressed from mainframes in the 1960s to keys, security systems, and airplanes in the year 2000. In fact, the new Boeing 777 has NEST in it, and it also has network servers on board. NEST enables the embedded network with the ability to put intelligence into devices. This gives one more control of the devices from wherever one is. For example, the pharmaceutical industry could use NEST to coordinate what the consumer is buying, what is in the warehouse, what the manufacturing plant is tooled for, and so on. Through NEST technology, the pharmaceutical industry now uses a camera that takes pictures of the pills. It can see whether an {open_quotes}overdose{close_quotes} or {open_quotes}underdose{close_quotes} of a particular type of pill is being manufactured. The plant can be shut down and corrections made immediately.

  7. High efficiency in mode-selective frequency conversion.

    PubMed

    Quesada, Nicolás; Sipe, J E

    2016-01-15

    Frequency conversion (FC) is an enabling process in many quantum information protocols. Recently, it has been observed that upconversion efficiencies in single-photon, mode-selective FC are limited to around 80%. In this Letter, we argue that these limits can be understood as time-ordering corrections (TOCs) that modify the joint conversion amplitude of the process. Furthermore, using a simple scaling argument, we show that recently proposed cascaded FC protocols that overcome the aforementioned limitations act as "attenuators" of the TOCs. This observation allows us to argue that very similar cascaded architectures can be used to attenuate TOCs in photon generation via spontaneous parametric downconversion. Finally, by using the Magnus expansion, we argue that the TOCs, which are usually considered detrimental for FC efficiency, can also be used to increase the efficiency of conversion in partially mode-selective FC. PMID:26766715

  8. Low cost and efficient photovoltaic conversion by nanocrystalline solar cells

    SciTech Connect

    Graetzel, M.

    1996-09-01

    Solar cells are expected to provide environmentally friendly solutions to the world`s energy supply problem. Learning from the concepts used by green plants we have developed a molecular photovoltaic device whose overall efficiency for AM 1.5 solar light to electricity has already attained 8-11%. The system is based on the sensitization of nanocrystalline oxide films by transition metal charge transfer sensitizers. In analogy to photosynthesis, the new chemical solar cell achieves the separation of the light absorption and charge carrier transport processes. Extraordinary yields for the conversion of incident photons into electric current are obtained, exceeding 90% for transition metal complexes within the wavelength range of their absorption band. The use of molten salt electrolytes together with coordination complexes of ruthenium as sensitizers and adequate sealing technology has endowed these cells with a remarkable stability making practical applications feasible. Seven industrial cooperations are presently involved in the development to bring these cells to the market. The first cells will be applied to supply electric power for consumer electronic devices. The launching of production of several products of this type is imminent and they should be on the market within the next two years. Quite aside from their intrinsic merits as photovoltaic device, the mesoscopic oxide semiconductor films developed in our laboratory offer attractive possibilities for a number of other applications. Thus, the first example of a nanocrystalline rocking chair battery will be demonstrated and its principle briefly discussed.

  9. Plasmolysis for efficient CO2 -to-fuel conversion

    NASA Astrophysics Data System (ADS)

    van Rooij, Gerard

    2015-09-01

    The strong non-equilibrium conditions provided by the plasma phase offer the opportunity to beat traditional thermal process energy efficiencies via preferential excitation of molecular vibrational modes. It is therefore a promising option for creating artificial solar fuels from CO2as raw material using (intermittently available) sustainable energy surpluses, which can easily be deployed within the present infrastructure for conventional fossil fuels. In this presentation, a common microwave reactor approach is evaluated experimentally with Rayleigh scattering and Fourier transform infrared spectroscopy to assess gas temperatures and conversion degrees, respectively. The results are interpreted on basis of estimates of the plasma dynamics obtained with electron energy distribution functions calculated with a Boltzmann solver. It indicates that the intrinsic electron energies are higher than is favourable for preferential vibrational excitation due to dissociative excitation, which causes thermodynamic equilibrium chemistry still to dominate the initial experiments. Novel reactor approaches are proposed to tailor the plasma dynamics to achieve the non-equilibrium in which vibrational excitation is dominant. In collaboration with Dirk van den Bekerom, Niek den Harder, Teofil Minea, Dutch Institute For Fundamental Energy Research, Eindhoven, Netherlands; Gield Berden, Institute for Molecules and Materials, FELIX facility, Radboud University, Nijmegen, Netherlands; Richard Engeln, Applied Physics, Plasma en Materials Processing, Eindhoven University of Technology; and Waldo Bongers, Martijn Graswinckel, Erwin Zoethout, Richard van de Sanden, Dutch Institute For Fundamental Energy Research, Eindhoven, Netherlands.

  10. Relationship between thermoelectric figure of merit and energy conversion efficiency

    PubMed Central

    Kim, Hee Seok; Liu, Weishu; Chen, Gang; Chu, Ching-Wu; Ren, Zhifeng

    2015-01-01

    The formula for maximum efficiency (ηmax) of heat conversion into electricity by a thermoelectric device in terms of the dimensionless figure of merit (ZT) has been widely used to assess the desirability of thermoelectric materials for devices. Unfortunately, the ηmax values vary greatly depending on how the average ZT values are used, raising questions about the applicability of ZT in the case of a large temperature difference between the hot and cold sides due to the neglect of the temperature dependences of the material properties that affect ZT. To avoid the complex numerical simulation that gives accurate efficiency, we have defined an engineering dimensionless figure of merit (ZT)eng and an engineering power factor (PF)eng as functions of the temperature difference between the cold and hot sides to predict reliably and accurately the practical conversion efficiency and output power, respectively, overcoming the reporting of unrealistic efficiency using average ZT values. PMID:26100905

  11. Efficient vibrational Raman conversion in O2 and N2 cells by use of superfluorescence seeding

    NASA Technical Reports Server (NTRS)

    Zhang, Barry; Lempert, Walter R.; Miles, R. B.; Diskin, Glenn

    1993-01-01

    We report first-Stokes vibrational conversion efficiency of 21 percent and 35 percent, respectively, in high-pressure O2- and N2-stimulated Raman cells. Broadband superfluorescence is employed to seed these Raman cells, significantly increasing the conversion efficiences with no measured effect on the Raman spectrum. The addition of helium buffer gas reduces competition from stimulated Brillouin scattering and improves the pulse-to-pulse stability and spatial mode quality by increasing the thermal conductivity. Further improvement of the spatial mode quality is achieved by use of gentle heating on the bottom of the cell to induce convection.

  12. Experiments to Determine the Efficiency of Various Energy Conversions.

    ERIC Educational Resources Information Center

    Curtis, D.; Goodwin, R. D.

    1980-01-01

    Described are experiments used in the "Physical Science and Man" course at Hartley CAE which enable determinations of efficiencies of two energy conversion processes, namely, electricity into heat and burning gas to produce heat. Activities for comparing the processes are suggested. (DS)

  13. Conversion Tower for Dispatchable Solar Power: High-Efficiency Solar-Electric Conversion Power Tower

    SciTech Connect

    2012-01-11

    HEATS Project: Abengoa Solar is developing a high-efficiency solar-electric conversion tower to enable low-cost, fully dispatchable solar energy generation. Abengoa’s conversion tower utilizes new system architecture and a two-phase thermal energy storage media with an efficient supercritical carbon dioxide (CO2) power cycle. The company is using a high-temperature heat-transfer fluid with a phase change in between its hot and cold operating temperature. The fluid serves as a heat storage material and is cheaper and more efficient than conventional heat-storage materials, like molten salt. It also allows the use of a high heat flux solar receiver, advanced high thermal energy density storage, and more efficient power cycles.

  14. Platinum nanoparticle decorated silicon nanowires for efficient solar energy conversion.

    PubMed

    Peng, Kui-Qing; Wang, Xin; Wu, Xiao-Ling; Lee, Shuit-Tong

    2009-11-01

    High-density aligned n-type silicon nanowire (SiNW) arrays decorated with discrete 5-10 nm platinum nanoparticles (PtNPs) have been fabricated by aqueous electroless Si etching followed by an electroless platinum deposition process. Coating of PtNPs on SiNW sidewalls yielded a substantial enhancement in photoconversion efficiency and an apparent energy conversion efficiency of up to 8.14% for the PtNP-decorated SiNW-based photoelectrochemical solar cell using a liquid electrolyte containing Br(-)/Br(2) redox couple. The results demonstrate PtNP-decorated SiNWs to be a promising hybrid system for solar energy conversion. PMID:19807069

  15. Saturation and energy-conversion efficiency of auroral kilometric radiation

    NASA Technical Reports Server (NTRS)

    Wu, C. S.; Tsai, S. T.; Xu, M. J.; Shen, J. W.

    1981-01-01

    A quasi-linear theory is used to study the saturation level of the auroral kilometric radiation. The investigation is based on the assumption that the emission is due to a cyclotron maser instability as suggested by Wu and Lee and Lee et al. The thermodynamic bound on the radiation energy is also estimated separately. The energy-conversion efficiency of the radiation process is discussed. The results are consistent with observations.

  16. Conversion of far ultraviolet to visible radiation: absolute measurements of the conversion efficiency of tetraphenyl butadiene

    NASA Astrophysics Data System (ADS)

    Vest, Robert E.; Coplan, Michael A.; Clark, Charles W.

    Far ultraviolet (FUV) scintillation of noble gases is used in dark matter and neutrino research and in neutron detection. Upon collisional excitation, noble gas atoms recombine into excimer molecules that decay by FUV emission. Direct detection of FUV is difficult. Another approach is to convert it to visible light using a wavelength-shifting medium. One such medium, tetraphenyl butadiene (TPB) can be vapor-deposited on substrates. Thus the quality of thin TPB films can be tightly controlled. We have measured the absolute efficiency of FUV-to-visible conversion by 1 μm-thick TPB films vs. FUV wavelengths between 130 and 300 nm, with 1 nm resolution. The energy efficiency of FUV to visible conversion varies between 1% and 5%. We make comparisons with other recent results. Work performed at the NIST SURF III Synchrotron Ultraviolet Radiation Facility,.

  17. Efficient and broadband polarization conversion with the coupled metasurfaces.

    PubMed

    Huang, Cheng-ping

    2015-12-14

    Coupled metasurfaces may refer to a composite plasmonic structure, which consists of multilayered but usually different metasurfaces. A pair of orthogonal plasmonic polarizers, which represents one of such systems, can induce a transmission of light and 90-degree polarization rotation. We explored the effect systematically and found that such effect may be highly efficient and broadband in the near-infrared region. By combining the low-loss metal (silver), the longer operating wavelength, and a work style using propagating waveguide mode, conversion efficiency more than 80% has been suggested near the telecom wavelength. We also suggested that, by overlapping the internal surface-plasmon (2, 0) and (1, 1) modes, an efficient and wideband polarization rotation can be realized. The maximal efficiency is 83% around the wavelength 1340 nm, and the working bandwidth reaches 300 nm. Similar effect has also been revealed in the THz band. The results are useful for constructing compact and high-performance polarization rotators. PMID:26698992

  18. Half-Heusler Alloys for Efficient Thermoelectric Power Conversion

    NASA Astrophysics Data System (ADS)

    Chen, Long; Zeng, Xiaoyu; Tritt, Terry M.; Poon, S. Joseph

    2016-07-01

    Half-Heusler (HH) phases (space group F43m, Clb) are increasingly gaining attention as promising thermoelectric materials in view of their thermal stability and environmental benignity as well as efficient power output. Until recently, the verifiable dimensionless figure of merit (ZT) of HH phases has remained moderate near 1, which limits the power conversion efficiency of these materials. We report herein ZT ˜ 1.3 in n-type (Hf,Zr)NiSn alloys near 850 K developed through elemental substitution and simultaneous embedment of nanoparticles in the HH matrix, obtained by annealing the samples close to their melting temperatures. Introduction of mass fluctuation and scattering centers play a key role in the high ZT measured, as shown by the reduction of thermal conductivity and increase of thermopower. Based on computation, the power conversion efficiency of a n-p couple module based on the new n-type (Hf,Zr,Ti)NiSn particles-in-matrix composite and recently reported high-ZT p-type HH phases is expected to reach 13%, comparable to that of state-of-the-art materials, but with the mentioned additional materials and environmental attributes. Since the high efficiency is obtained without tuning the microstructure of the HH phases, it leaves room for further optimization.

  19. Quantum Coherence in Photosynthesis for Efficient Solar Energy Conversion

    PubMed Central

    Romero, Elisabet; Augulis, Ramunas; Novoderezhkin, Vladimir I.; Ferretti, Marco; Thieme, Jos; Zigmantas, Donatas; van Grondelle, Rienk

    2014-01-01

    The crucial step in the conversion of solar to chemical energy in Photosynthesis takes place in the reaction center where the absorbed excitation energy is converted into a stable charge separated state by ultrafast electron transfer events. However, the fundamental mechanism responsible for the near unity quantum efficiency of this process is unknown. Here we elucidate the role of coherence in determining the efficiency of charge separation in the plant photosystem II reaction centre (PSII RC) by comprehensively combining experiment (two-dimensional electronic spectroscopy) and theory (Redfield theory). We reveal the presence of electronic coherence between excitons as well as between exciton and charge transfer states which we argue to be maintained by vibrational modes. Furthermore, we present evidence for the strong correlation between the degree of electronic coherence and efficient and ultrafast charge separation. We propose that this coherent mechanism will inspire the development of new energy technologies. PMID:26870153

  20. Development of a solar receiver for a high-efficiency thermionic/thermoelectric conversion system

    SciTech Connect

    Naito, H.; Kohsaka, Y.; Cooke, D.; Arashi, H.

    1996-10-01

    Solar energy is one of the most promising energy resources on Earth and in space, because it is clean and inexhaustible. Therefore, we have been developing a solar-powered high-efficiency thermionic-thermoelectric conversion system which combines a thermionic converter (TIC) with a thermoelectric converter (TEC) to use thermal energy efficiently and to achieve high efficiency conversion. The TIC emitter must uniformly heat up to 1800 K. The TIC emitter can be heated using thermal radiation from a solar receiver maintained at a high temperature by concentrated solar irradiation. A cylindrical cavity-type solar receiver constructed from graphite was designed and heated in a vacuum by using the solar concentrator at Tohoku University. The maximum temperature of the solar receiver enclosed by a molybdenum cup reached 1965 K, which was sufficiently high to heat a TIC emitter using thermal radiation from the receiver. 4 refs., 6 figs., 1 tab.

  1. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; Baldasaro, Paul F.; DePoy, David M.

    2010-09-07

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  2. Tandem filters using frequency selective surfaces for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Dziendziel, Randolph J.; DePoy, David Moore; Baldasaro, Paul Francis

    2007-01-23

    This invention relates to the field of thermophotovoltaic (TPV) direct energy conversion. In particular, TPV systems use filters to minimize parasitic absorption of below bandgap energy. This invention constitutes a novel combination of front surface filters to increase TPV conversion efficiency by reflecting useless below bandgap energy while transmitting a very high percentage of the useful above bandgap energy. In particular, a frequency selective surface is used in combination with an interference filter. The frequency selective surface provides high transmission of above bandgap energy and high reflection of long wavelength below bandgap energy. The interference filter maintains high transmission of above bandgap energy and provides high reflection of short wavelength below bandgap energy and a sharp transition from high transmission to high reflection.

  3. The Effect of Mobile Learning on Students' Achievement and Conversational Skills

    ERIC Educational Resources Information Center

    Elfeky, Abdellah Ibrahim Mohammed; Masadeh, Thouqan Saleem Yakoub

    2016-01-01

    The present study aimed to examine the effect of Mobile Learning, which is a kind of E-learning that uses mobile devices, on the development of the academic achievement and conversational skills of English language specialty students at Najran University. The study used the quasi-experimental approach. Participants consisted of (50) students who…

  4. Coping with Achievement-Related Failure: An Examination of Conversations between Friends

    ERIC Educational Resources Information Center

    Altermatt, Ellen Rydell; Broady, Elizabeth F.

    2009-01-01

    Prior research has identified ways in which parents and teachers contribute to learned helpless responses to failure, but little is known about the role that interactions with peers might play. In this study, the conversations of fourth- through sixth- grade children and their friends were observed after children experienced an achievement-related…

  5. Riverbed methanotrophy sustained by high carbon conversion efficiency.

    PubMed

    Trimmer, Mark; Shelley, Felicity C; Purdy, Kevin J; Maanoja, Susanna T; Chronopoulou, Panagiota-Myrsini; Grey, Jonathan; Jonathan, Grey

    2015-10-01

    Our understanding of the role of freshwaters in the global carbon cycle is being revised, but there is still a lack of data, especially for the cycling of methane, in rivers and streams. Unravelling the role of methanotrophy is key to determining the fate of methane in rivers. Here we focus on the carbon conversion efficiency (CCE) of methanotrophy, that is, how much organic carbon is produced per mole of CH4 oxidised, and how this is influenced by variation in methanotroph communities. First, we show that the CCE of riverbed methanotrophs is consistently high (~50%) across a wide range of methane concentrations (~10-7000 nM) and despite a 10-fold span in the rate of methane oxidation. Then, we show that this high conversion efficiency is largely conserved (50%± confidence interval 44-56%) across pronounced variation in the key functional gene (70 operational taxonomic units (OTUs)), particulate methane monooxygenase (pmoA), and marked shifts in the abundance of Type I and Type II methanotrophs in eight replicate chalk streams. These data may suggest a degree of functional redundancy within the variable methanotroph community inhabiting these streams and that some of the variation in pmoA may reflect a suite of enzymes of different methane affinities which enables such a large range of methane concentrations to be oxidised. The latter, coupled to their high CCE, enables the methanotrophs to sustain net production throughout the year, regardless of the marked temporal and spatial changes that occur in methane. PMID:26057842

  6. AMTEC: High efficiency static conversion for space power

    NASA Technical Reports Server (NTRS)

    Bankston, C. P.; Shirbacheh, M.

    1986-01-01

    Future manned and unmanned space missions will require reliable, high efficiency energy conversion systems. For a manned Mars mission, power levels in the range of 10 to 100 kWe will be needed. The Alkali Metal Thermoelectric Converter (AMTEC) is a direct energy conversion technology with the potential to meet these needs. The AMTEC is a thermally regenerative electrochemical device that derives its operation from the sodium ion conducting properties of beta-alumina solid electrolyte (BASE). To date, an efficiency of 19%, area power density of 1 W/sq cm, and a lifetime of 10,000 hours at high temperature were demonstrated in laboratory devices. Systems studies show that projected AMTEC systems equal or surpass the performance of other static or dynamic systems in applications of 1 kWe-1 MWe. Thus, the laboratory experiments and applications studies conducted to date have shown that the AMTEC posseses great potential. In order to bring this technology to the stage where prototype units can be built and operated, several technical issues must be addressed. These include the need for long life, high power electrodes, minimization of radiative parasitic losses, and high temperature seals. In summary, the evidence shows that if AMTEC is developed, it can play a significant role in future space power applications.

  7. Efficient computerized model for dynamic analysis of energy conversion systems

    NASA Technical Reports Server (NTRS)

    Hughes, R. D.; Lansing, F. L.; Khan, I. R.

    1983-01-01

    In searching for the optimum parameters that minimize the total life cycle cost of an energy conversion system, various combinations of components are examined and the resulting system performance and associated economics are studied. The systems performance and economics simulation computer program (SPECS) was developed to fill this need. The program simulates the fluid flow, thermal, and electrical characteristics of a system of components on a quasi-steady state basis for a variety of energy conversion systems. A unique approach is used in which the set of characteristic equations is solved by the Newton-Raphson technique. This approach eliminates the tedious iterative loops which are found in comparable programs such as TRNSYS or SOLTES-1. Several efficient features were also incorporated such as the centralized control and energy management scheme, and analogous treatment of energy flow in electrical and mechanical components, and the modeling of components of similar fundamental characteristics using generic subroutines. Initial tests indicate that this model can be used effectively with a relatively small number of time steps and low computer cost.

  8. Efficient computerized model for dynamic analysis of energy conversion systems

    NASA Astrophysics Data System (ADS)

    Hughes, R. D.; Lansing, F. L.; Khan, I. R.

    1983-02-01

    In searching for the optimum parameters that minimize the total life cycle cost of an energy conversion system, various combinations of components are examined and the resulting system performance and associated economics are studied. The systems performance and economics simulation computer program (SPECS) was developed to fill this need. The program simulates the fluid flow, thermal, and electrical characteristics of a system of components on a quasi-steady state basis for a variety of energy conversion systems. A unique approach is used in which the set of characteristic equations is solved by the Newton-Raphson technique. This approach eliminates the tedious iterative loops which are found in comparable programs such as TRNSYS or SOLTES-1. Several efficient features were also incorporated such as the centralized control and energy management scheme, and analogous treatment of energy flow in electrical and mechanical components, and the modeling of components of similar fundamental characteristics using generic subroutines. Initial tests indicate that this model can be used effectively with a relatively small number of time steps and low computer cost.

  9. Tandem photovoltaic solar cells and increased solar energy conversion efficiency

    NASA Technical Reports Server (NTRS)

    Loferski, J. J.

    1976-01-01

    Tandem photovoltaic cells, as proposed by Jackson (1955) to increase the efficiency of solar energy conversion, involve the construction of a system of stacked p/n homojunction photovoltaic cells composed of different semiconductors. It had been pointed out by critics, however, that the total power which could be extracted from the cells in the stack placed side by side was substantially greater than the power obtained from the stacked cells. A reexamination of the tandem cell concept in view of the development of the past few years is conducted. It is concluded that the use of tandem cell systems in flat plate collectors, as originally envisioned by Jackson, may yet become feasible as a result of the development of economically acceptable solar cells for large scale terrestrial power generation.

  10. Riverbed methanotrophy sustained by high carbon conversion efficiency

    PubMed Central

    Trimmer, Mark; Shelley, Felicity C; Purdy, Kevin J; Maanoja, Susanna T; Chronopoulou, Panagiota-Myrsini; Grey, Jonathan

    2015-01-01

    Our understanding of the role of freshwaters in the global carbon cycle is being revised, but there is still a lack of data, especially for the cycling of methane, in rivers and streams. Unravelling the role of methanotrophy is key to determining the fate of methane in rivers. Here we focus on the carbon conversion efficiency (CCE) of methanotrophy, that is, how much organic carbon is produced per mole of CH4 oxidised, and how this is influenced by variation in methanotroph communities. First, we show that the CCE of riverbed methanotrophs is consistently high (~50%) across a wide range of methane concentrations (~10–7000 nM) and despite a 10-fold span in the rate of methane oxidation. Then, we show that this high conversion efficiency is largely conserved (50%± confidence interval 44–56%) across pronounced variation in the key functional gene (70 operational taxonomic units (OTUs)), particulate methane monooxygenase (pmoA), and marked shifts in the abundance of Type I and Type II methanotrophs in eight replicate chalk streams. These data may suggest a degree of functional redundancy within the variable methanotroph community inhabiting these streams and that some of the variation in pmoA may reflect a suite of enzymes of different methane affinities which enables such a large range of methane concentrations to be oxidised. The latter, coupled to their high CCE, enables the methanotrophs to sustain net production throughout the year, regardless of the marked temporal and spatial changes that occur in methane. PMID:26057842

  11. Enhanced conversion efficiency in perovskite solar cells by effectively utilizing near infrared light.

    PubMed

    Que, Meidan; Que, Wenxiu; Yin, Xingtian; Chen, Peng; Yang, Yawei; Hu, Jiaxing; Yu, Boyan; Du, Yaping

    2016-08-14

    Up-conversion β-NaYF4:Yb(3+),Tm(3+)/NaYF4 core-shell nanoparticles (NYF NPs) with a high luminous intensity in the visible light region were synthesized by a hydrothermal reaction process. Photocurrent densities of the mesoscopic perovskite solar cells fabricated by incorporating up-conversion NYF NPs into the electron transporting layer are effectively enhanced. The effects of the thicknesses of the electron transporting layer and the weight ratio of up-conversion NYF NPs/TiO2 on the power conversion efficiency (PCE) of the as-fabricated devices were also investigated. The results indicate that the PCE of the optimized device achieves 16.9%, which is 20% higher than that of the device without introducing NYF NPs, and the steady-state PCE of the as-fabricated devices is close to its transient-state PCE. The up-conversion effect of NYF NPs is conducive to higher device performance rather than the nanoparticles as scattering centers to increase possible light absorption of the perovskite film or the electronic effect of the NaYF4 shell surface. These results can be further confirmed by finite-difference time-domain simulation. Photoluminescence results suggest that the multiphonon-assistance can accelerate the nonradiative recombination process at a lower temperature. Incorporating NYF NPs into the electron transporting layer opens a new approach to a promising family of electron transporting materials for mesoscopic perovskite solar cells. PMID:27406678

  12. Overall energy conversion efficiency of a photosynthetic vesicle

    PubMed Central

    Sener, Melih; Strumpfer, Johan; Singharoy, Abhishek; Hunter, C Neil; Schulten, Klaus

    2016-01-01

    The chromatophore of purple bacteria is an intracellular spherical vesicle that exists in numerous copies in the cell and that efficiently converts sunlight into ATP synthesis, operating typically under low light conditions. Building on an atomic-level structural model of a low-light-adapted chromatophore vesicle from Rhodobacter sphaeroides, we investigate the cooperation between more than a hundred protein complexes in the vesicle. The steady-state ATP production rate as a function of incident light intensity is determined after identifying quinol turnover at the cytochrome bc1 complex (cytb⁢c1) as rate limiting and assuming that the quinone/quinol pool of about 900 molecules acts in a quasi-stationary state. For an illumination condition equivalent to 1% of full sunlight, the vesicle exhibits an ATP production rate of 82 ATP molecules/s. The energy conversion efficiency of ATP synthesis at illuminations corresponding to 1%–5% of full sunlight is calculated to be 0.12–0.04, respectively. The vesicle stoichiometry, evolutionarily adapted to the low light intensities in the habitat of purple bacteria, is suboptimal for steady-state ATP turnover for the benefit of protection against over-illumination. DOI: http://dx.doi.org/10.7554/eLife.09541.001 PMID:27564854

  13. Overall energy conversion efficiency of a photosynthetic vesicle.

    PubMed

    Sener, Melih; Strumpfer, Johan; Singharoy, Abhishek; Hunter, C Neil; Schulten, Klaus

    2016-01-01

    The chromatophore of purple bacteria is an intracellular spherical vesicle that exists in numerous copies in the cell and that efficiently converts sunlight into ATP synthesis, operating typically under low light conditions. Building on an atomic-level structural model of a low-light-adapted chromatophore vesicle from Rhodobacter sphaeroides, we investigate the cooperation between more than a hundred protein complexes in the vesicle. The steady-state ATP production rate as a function of incident light intensity is determined after identifying quinol turnover at the cytochrome bc1 complex (cytb⁢c1) as rate limiting and assuming that the quinone/quinol pool of about 900 molecules acts in a quasi-stationary state. For an illumination condition equivalent to 1% of full sunlight, the vesicle exhibits an ATP production rate of 82 ATP molecules/s. The energy conversion efficiency of ATP synthesis at illuminations corresponding to 1%-5% of full sunlight is calculated to be 0.12-0.04, respectively. The vesicle stoichiometry, evolutionarily adapted to the low light intensities in the habitat of purple bacteria, is suboptimal for steady-state ATP turnover for the benefit of protection against over-illumination. PMID:27564854

  14. Improving the sunlight-to-biomass conversion efficiency in microalgal biofactories.

    PubMed

    Wobbe, Lutz; Remacle, Claire

    2015-05-10

    Microalgae represent promising organisms for the sustainable production of commodities, chemicals or fuels. Future use of such systems, however, requires increased productivity of microalgal mass cultures in order to reach an economic viability for microalgae-based production schemes. The efficiency of sunlight-to-biomass conversion that can be observed in bulk cultures is generally far lower (35-80%) than the theoretical maximum, because energy losses occur at multiple steps during the light-driven conversion of carbon dioxide to organic carbon. The light-harvesting system is a major source of energy losses and thus a prime target for strain engineering. Truncation of the light-harvesting antenna in the algal model organism Chlamydomonas reinhardtii was shown to be an effective way of increasing culture productivity at least under saturating light conditions. Furthermore engineering of the Calvin-Benson cycle or the creation of photorespiratory bypasses in A. thaliana proved to be successful in terms of achieving higher biomass productivities. An efficient generation of novel microalgal strains with improved sunlight conversion efficiencies by targeted engineering in the future will require an expanded molecular toolkit. In the meantime random mutagenesis coupled to high-throughput screening for desired phenotypes can be used to provide engineered microalgae. PMID:25160918

  15. Bilayer Polymer Solar Cells with Improved Power Conversion Efficiency and Enhanced Spectrum Coverage

    SciTech Connect

    Kekuda, Dhananjaya; Chu, Chih-Wei

    2011-10-20

    We demonstrate the construction of an efficient bilayer polymer solar cell comprising of Poly(3-hexylthiophene)(P3HT) as a p-type semiconductor and asymmetric fullerene (C{sub 70}) as n-type counterparts. The bilayer configuration was very efficient compared to the individual layer performance and it behaved like a regular p-n junction device. The photovoltaic characteristic of the bilayers were studied under AM 1.5 solar radiation and the optimized device parameters are the following: Voc = 0.5V, Jsc = 10.1 mA/cm{sup 2}, FF = 0.60 and power conversion efficiency of 3.6 %. A high fill factor of {approx}0.6 was achieved, which is only slightly reduced at very intense illumination. Balanced mobility between p-and n-layers is achieved which is essential for achieving high device performance. Correlation between the crystallinity, morphology and the transport properties of the active layers is established. The External quantum efficiency (EQE) spectral distribution of the bilayer devices with different processing solvents correlates well with the trends of short circuit current densities (J{sub sc}) measured under illumination. Efficiency of the bilayer devices with rough P3HT layer was found to be about 3 times higher than those with a planar P3HT surface. Hence it is desirable to have a larger grains with a rough surface of P3HT layer for providing larger interfacial area for the exciton dissociation.

  16. Efficiency evaluation of oxygen enrichment in energy conversion processes

    SciTech Connect

    Bomelburg, H.J.

    1983-12-01

    The extent to which energy conversion efficiencies can be increased by using oxygen or oxygen-enriched air for combustion was studied. Combustion of most fuels with oxygen instead of air was found to have five advantages: increases combustion temperature and efficiency, improves heat transfer at high temperatures, reduces nitrous oxide emissions, permits a high ration of exhaust gas recirculation and allows combustion of certain materials not combustible in air. The same advantages, although to a lesser degree, are apparent with oxygen-enriched air. The cost-effectiveness of the process must necessarily be improved by about 10% when using oxygen instead of air before such use could become justifiable on purely economic terms. Although such a modest increase appears to be attainable in real situations, this study ascertained that it is not possible to generally assess the economic gains. Rather, each case requires its own evaluation. For certain processes industry has already proven that the use of oxygen leads to more efficient plant operation. Several ideas for essentially new applications are described. Specifically, when oxygen is used with exhaust gas recirculation in external or internal combustion engines. It appears also that the advantages of pulse combustion can be amplified further if oxygen is used. When burning wet fuels with oxygen, direct steam generation becomes possible. Oxygen combustion could also improve processes for in situ gasification of coals, oil shales, peats, and other wet fuels. Enhanced oil recovery by fire flooding methods might also become more effective if oxygen is used. The cold energy contained in liquid oxygen can be substantially recovered in the low end of certain thermodynamic cycles. Further efforts to develop certain schemes for using oxygen for combustion appear to be justified from both the technical and economic viewpoints.

  17. Thermodynamic and achievable efficiencies for solar-driven electrochemical reduction of carbon dioxide to transportation fuels

    NASA Astrophysics Data System (ADS)

    Singh, Meenesh R.; Clark, Ezra L.; Bell, Alexis T.

    2015-11-01

    Thermodynamic, achievable, and realistic efficiency limits of solar-driven electrochemical conversion of water and carbon dioxide to fuels are investigated as functions of light-absorber composition and configuration, and catalyst composition. The maximum thermodynamic efficiency at 1-sun illumination for adiabatic electrochemical synthesis of various solar fuels is in the range of 32-42%. Single-, double-, and triple-junction light absorbers are found to be optimal for electrochemical load ranges of 0-0.9 V, 0.9-1.95 V, and 1.95-3.5 V, respectively. Achievable solar-to-fuel (STF) efficiencies are determined using ideal double- and triple-junction light absorbers and the electrochemical load curves for CO2 reduction on silver and copper cathodes, and water oxidation kinetics over iridium oxide. The maximum achievable STF efficiencies for synthesis gas (H2 and CO) and Hythane (H2 and CH4) are 18.4% and 20.3%, respectively. Whereas the realistic STF efficiency of photoelectrochemical cells (PECs) can be as low as 0.8%, tandem PECs and photovoltaic (PV)-electrolyzers can operate at 7.2% under identical operating conditions. We show that the composition and energy content of solar fuels can also be adjusted by tuning the band-gaps of triple-junction light absorbers and/or the ratio of catalyst-to-PV area, and that the synthesis of liquid products and C2H4 have high profitability indices.

  18. Thermodynamic and achievable efficiencies for solar-driven electrochemical reduction of carbon dioxide to transportation fuels.

    PubMed

    Singh, Meenesh R; Clark, Ezra L; Bell, Alexis T

    2015-11-10

    Thermodynamic, achievable, and realistic efficiency limits of solar-driven electrochemical conversion of water and carbon dioxide to fuels are investigated as functions of light-absorber composition and configuration, and catalyst composition. The maximum thermodynamic efficiency at 1-sun illumination for adiabatic electrochemical synthesis of various solar fuels is in the range of 32-42%. Single-, double-, and triple-junction light absorbers are found to be optimal for electrochemical load ranges of 0-0.9 V, 0.9-1.95 V, and 1.95-3.5 V, respectively. Achievable solar-to-fuel (STF) efficiencies are determined using ideal double- and triple-junction light absorbers and the electrochemical load curves for CO2 reduction on silver and copper cathodes, and water oxidation kinetics over iridium oxide. The maximum achievable STF efficiencies for synthesis gas (H2 and CO) and Hythane (H2 and CH4) are 18.4% and 20.3%, respectively. Whereas the realistic STF efficiency of photoelectrochemical cells (PECs) can be as low as 0.8%, tandem PECs and photovoltaic (PV)-electrolyzers can operate at 7.2% under identical operating conditions. We show that the composition and energy content of solar fuels can also be adjusted by tuning the band-gaps of triple-junction light absorbers and/or the ratio of catalyst-to-PV area, and that the synthesis of liquid products and C2H4 have high profitability indices. PMID:26504215

  19. Thermodynamic and achievable efficiencies for solar-driven electrochemical reduction of carbon dioxide to transportation fuels

    PubMed Central

    Singh, Meenesh R.; Clark, Ezra L.; Bell, Alexis T.

    2015-01-01

    Thermodynamic, achievable, and realistic efficiency limits of solar-driven electrochemical conversion of water and carbon dioxide to fuels are investigated as functions of light-absorber composition and configuration, and catalyst composition. The maximum thermodynamic efficiency at 1-sun illumination for adiabatic electrochemical synthesis of various solar fuels is in the range of 32–42%. Single-, double-, and triple-junction light absorbers are found to be optimal for electrochemical load ranges of 0–0.9 V, 0.9–1.95 V, and 1.95–3.5 V, respectively. Achievable solar-to-fuel (STF) efficiencies are determined using ideal double- and triple-junction light absorbers and the electrochemical load curves for CO2 reduction on silver and copper cathodes, and water oxidation kinetics over iridium oxide. The maximum achievable STF efficiencies for synthesis gas (H2 and CO) and Hythane (H2 and CH4) are 18.4% and 20.3%, respectively. Whereas the realistic STF efficiency of photoelectrochemical cells (PECs) can be as low as 0.8%, tandem PECs and photovoltaic (PV)-electrolyzers can operate at 7.2% under identical operating conditions. We show that the composition and energy content of solar fuels can also be adjusted by tuning the band-gaps of triple-junction light absorbers and/or the ratio of catalyst-to-PV area, and that the synthesis of liquid products and C2H4 have high profitability indices. PMID:26504215

  20. A polymer tandem solar cell with 10.6% power conversion efficiency

    PubMed Central

    You, Jingbi; Dou, Letian; Yoshimura, Ken; Kato, Takehito; Ohya, Kenichiro; Moriarty, Tom; Emery, Keith; Chen, Chun-Chao; Gao, Jing; Li, Gang; Yang, Yang

    2013-01-01

    An effective way to improve polymer solar cell efficiency is to use a tandem structure, as a broader part of the spectrum of solar radiation is used and the thermalization loss of photon energy is minimized. In the past, the lack of high-performance low-bandgap polymers was the major limiting factor for achieving high-performance tandem solar cell. Here we report the development of a high-performance low bandgap polymer (bandgap <1.4 eV), poly[2,7-(5,5-bis-(3,7-dimethyloctyl)-5H-dithieno[3,2-b:2′,3′-d]pyran)-alt-4,7-(5,6-difluoro-2,1,3-benzothia diazole)] with a bandgap of 1.38 eV, high mobility, deep highest occupied molecular orbital. As a result, a single-junction device shows high external quantum efficiency of >60% and spectral response that extends to 900 nm, with a power conversion efficiency of 7.9%. The polymer enables a solution processed tandem solar cell with certified 10.6% power conversion efficiency under standard reporting conditions (25 °C, 1,000 Wm−2, IEC 60904-3 global), which is the first certified polymer solar cell efficiency over 10%. PMID:23385590

  1. Some methods for achieving more efficient performance of fuel assemblies

    NASA Astrophysics Data System (ADS)

    Boltenko, E. A.

    2014-07-01

    More efficient operation of reactor plant fuel assemblies can be achieved through the use of new technical solutions aimed at obtaining more uniform distribution of coolant over the fuel assembly section, more intense heat removal on convex heat-transfer surfaces, and higher values of departure from nucleate boiling ratio (DNBR). Technical solutions using which it is possible to obtain more intense heat removal on convex heat-transfer surfaces and higher DNBR values in reactor plant fuel assemblies are considered. An alternative heat removal arrangement is described using which it is possible to obtain a significantly higher power density in a reactor plant and essentially lower maximal fuel rod temperature.

  2. First-Generation Subporphyrinatoboron(III) Sensitizers Surpass the 10 % Power Conversion Efficiency Threshold.

    PubMed

    Copley, Graeme; Hwang, Daesub; Kim, Dongho; Osuka, Atsuhiro

    2016-08-22

    Subporphyrinatoboron(III) (SubB) sensitizers were synthesized for use in dye-sensitized solar cells (DSSCs). The prototype, which comprises a sterically demanding 3,5-di-tert-butylphenyl scaffold, a meso-ethynylphenyl spacer, and a cyanoacrylic acid anchoring group, achieved an open-circuit voltage VOC of 836 mV, short-circuit current density JSC of 15.3 mA cm(-2) , fill factor of 0.786, and a photon-to-current conversion efficiency of 10.1 %. Such astonishing figures suggest that a bright future lies ahead for SubB in the realm of DSSCs. PMID:27482949

  3. Polymerization efficiency of curing lamps: a universal energy conversion relationship predictive of conversion of resin-based composite.

    PubMed

    Halvorson, Rolf H; Erickson, Robert L; Davidson, Carel L

    2004-01-01

    A universal energy-conversion relationship (ECRu) predictive of conversion of a resin-based composite (RBC) polymerized with any light source has been described. This relationship was derived from an energy conversion relationship for RBC polymerized with a tungsten-halogen lamp and the lamp's efficiency relative to a hypothetical standard lamp. The ECRu was then used to predict conversion throughout RBC polymerized with an LED lamp using the lamp's relative efficiency compared to the standard lamp. The universal energy scale has also been described as predictive of scrape-back lengths for this RBC family when polymerized with any light source. Despite a 31% greater relative efficiency, scrape-back lengths from RBC polymerized using the LED lamp were predicted to be only 6% greater than those polymerized with the tungsten-halogen lamp when RBC is polymerized on an equal energy basis. This result was experimentally verified. PMID:14753341

  4. Theoretical maximum efficiency of solar energy conversion in plasmonic metal-semiconductor heterojunctions.

    PubMed

    Cushing, Scott K; Bristow, Alan D; Wu, Nianqiang

    2015-11-28

    Plasmonics can enhance solar energy conversion in semiconductors by light trapping, hot electron transfer, and plasmon-induced resonance energy transfer (PIRET). The multifaceted response of the plasmon and multiple interaction pathways with the semiconductor makes optimization challenging, hindering design of efficient plasmonic architectures. Therefore, in this paper we use a density matrix model to capture the interplay between scattering, hot electrons, and dipole-dipole coupling through the plasmon's dephasing, including both the coherent and incoherent dynamics necessary for interactions on the plasmon's timescale. The model is extended to Shockley-Queisser limit calculations for both photovoltaics and solar-to-chemical conversion, revealing the optimal application of each enhancement mechanism based on plasmon energy, semiconductor energy, and plasmon dephasing. The results guide application of plasmonic solar-energy harvesting, showing which enhancement mechanism is most appropriate for a given semiconductor's weakness, and what nanostructures can achieve the maximum enhancement. PMID:26497739

  5. Improving solar cell efficiencies by down-conversion of high-energy photons

    NASA Astrophysics Data System (ADS)

    Trupke, T.; Green, M. A.; Wurfel, P.

    2002-08-01

    One of the major loss mechanisms leading to low energy conversion efficiencies of solar cells is the thermalization of charge carriers generated by the absorption of high-energy photons. These losses can largely be reduced in a solar cell if more than one electron-hole pair can be generated per incident photon. A method to realize multiple electron-hole pair generation per incident photon is proposed in this article. Incident photons with energies larger than twice the band gap of the solar cell are absorbed by a luminescence converter, which transforms them into two or more lower energy photons. The theoretical efficiency limit of this system for nonconcentrated sunlight is determined as a function of the solar cell's band gap using detailed balance calculations. It is shown that a maximum conversion efficiency of 39.63% can be achieved for a 6000 K blackbody spectrum and for a luminescence converter with one intermediate level. This is a substantial improvement over the limiting efficiency of 30.9%, which a solar cell exposed directly to nonconcentrated radiation may have under the same assumption of radiative recombination only.

  6. Multipass configuration to achieve high-frequency conversion in Li2B4O7 crystals

    NASA Astrophysics Data System (ADS)

    Chatterjee, Udit; Gangopadhyay, Sudipta; Ghosh, Chittaranjan; Bhar, Gopal C.

    2005-02-01

    A multipass configuration for second-harmonic generation of Nd:YAG laser radiation is demonstrated to produce, for the first time to the authors' knowledge in twin lithium tetraborate crystals, as much as 21% conversion efficiency even though the effective nonlinear coefficient of the crystal is as low as 1/6th that of KDP. Apart from crystals that have large walk-off angles, low effective nonlinear coefficients, or both, the simple experimental setup would also be quite suitable for those crystals, especially infrared crystals, that have large effective nonlinear coefficients but low laser damage thresholds.

  7. Multipass configuration to achieve high-frequency conversion in Li2B4O7 crystals.

    PubMed

    Chatterjee, Udit; Gangopadhyay, Sudipta; Ghosh, Chittaranjan; Bhar, Gopal C

    2005-02-10

    A multipass configuration for second-harmonic generation of Nd:YAG laser radiation is demonstrated to produce, for the first time to the authors' knowledge in twin lithium tetraborate crystals, as much as 21% conversion efficiency even though the effective nonlinear coefficient of the crystal is as low as 1/6th that of KDP. Apart from crystals that have large walk-off angles, low effective nonlinear coefficients, or both, the simple experimental setup would also be quite suitable for those crystals, especially infrared crystals, that have large effective nonlinear coefficients but low laser damage thresholds. PMID:15751864

  8. Enhanced conversion efficiency in perovskite solar cells by effectively utilizing near infrared light

    NASA Astrophysics Data System (ADS)

    Que, Meidan; Que, Wenxiu; Yin, Xingtian; Chen, Peng; Yang, Yawei; Hu, Jiaxing; Yu, Boyan; Du, Yaping

    2016-07-01

    Up-conversion β-NaYF4:Yb3+,Tm3+/NaYF4 core-shell nanoparticles (NYF NPs) with a high luminous intensity in the visible light region were synthesized by a hydrothermal reaction process. Photocurrent densities of the mesoscopic perovskite solar cells fabricated by incorporating up-conversion NYF NPs into the electron transporting layer are effectively enhanced. The effects of the thicknesses of the electron transporting layer and the weight ratio of up-conversion NYF NPs/TiO2 on the power conversion efficiency (PCE) of the as-fabricated devices were also investigated. The results indicate that the PCE of the optimized device achieves 16.9%, which is 20% higher than that of the device without introducing NYF NPs, and the steady-state PCE of the as-fabricated devices is close to its transient-state PCE. The up-conversion effect of NYF NPs is conducive to higher device performance rather than the nanoparticles as scattering centers to increase possible light absorption of the perovskite film or the electronic effect of the NaYF4 shell surface. These results can be further confirmed by finite-difference time-domain simulation. Photoluminescence results suggest that the multiphonon-assistance can accelerate the nonradiative recombination process at a lower temperature. Incorporating NYF NPs into the electron transporting layer opens a new approach to a promising family of electron transporting materials for mesoscopic perovskite solar cells.Up-conversion β-NaYF4:Yb3+,Tm3+/NaYF4 core-shell nanoparticles (NYF NPs) with a high luminous intensity in the visible light region were synthesized by a hydrothermal reaction process. Photocurrent densities of the mesoscopic perovskite solar cells fabricated by incorporating up-conversion NYF NPs into the electron transporting layer are effectively enhanced. The effects of the thicknesses of the electron transporting layer and the weight ratio of up-conversion NYF NPs/TiO2 on the power conversion efficiency (PCE) of the as

  9. Porous Pd nanoparticles with high photothermal conversion efficiency for efficient ablation of cancer cells

    NASA Astrophysics Data System (ADS)

    Xiao, Jia-Wen; Fan, Shi-Xuan; Wang, Feng; Sun, Ling-Dong; Zheng, Xiao-Yu; Yan, Chun-Hua

    2014-03-01

    Nanoparticle (NP) mediated photothermal effect shows great potential as a noninvasive method for cancer therapy treatment, but the development of photothermal agents with high photothermal conversion efficiency, small size and good biocompatibility is still a big challenge. Herein, we report Pd NPs with a porous structure exhibiting enhanced near infrared (NIR) absorption as compared to Pd nanocubes with a similar size (almost two-fold enhancement with a molar extinction coefficient of 6.3 × 107 M-1 cm-1), and the porous Pd NPs display monotonically rising absorbance from NIR to UV-Vis region. When dispersed in water and illuminated with an 808 nm laser, the porous Pd NPs give a photothermal conversion efficiency as high as 93.4%, which is comparable to the efficiency of Au nanorods we synthesized (98.6%). As the porous Pd NPs show broadband NIR absorption (650-1200 nm), this allows us to choose multiple laser wavelengths for photothermal therapy. In vitro photothermal heating of HeLa cells in the presence of porous Pd NPs leads to 100% cell death under 808 nm laser irradiation (8 W cm-2, 4 min). For photothermal heating using 730 nm laser, 70% of HeLa cells were killed after 4 min irradiation at a relative low power density of 6 W cm-2. These results demonstrated that the porous Pd nanostructure is an attractive photothermal agent for cancer therapy.Nanoparticle (NP) mediated photothermal effect shows great potential as a noninvasive method for cancer therapy treatment, but the development of photothermal agents with high photothermal conversion efficiency, small size and good biocompatibility is still a big challenge. Herein, we report Pd NPs with a porous structure exhibiting enhanced near infrared (NIR) absorption as compared to Pd nanocubes with a similar size (almost two-fold enhancement with a molar extinction coefficient of 6.3 × 107 M-1 cm-1), and the porous Pd NPs display monotonically rising absorbance from NIR to UV-Vis region. When dispersed in water

  10. Building aggressively duty-cycled platforms to achieve energy efficiency

    NASA Astrophysics Data System (ADS)

    Agarwal, Yuvraj

    Managing power consumption and improving energy efficiency is a key driver in the design of computing devices today. This is true for both battery-powered mobile devices as well as mains-powered desktop PCs and servers. In case of mobile devices, the focus of optimization is on energy efficiency to maximize battery lifetime. In case of mains-powered devices, we seek to optimize power consumption to reduce energy costs, thermal and environmental concerns. Traditionally, there are two main mechanisms to improve energy efficiency in systems: slowdown techniques that seek to reduce processor speed or radio power against the rate of work done, and shutdown techniques that seek to shut down specific components or subsystems -- such as processor, radio, memory -- to reduce power used by these components when not in use. The adverse effect of using these techniques is either reduced performance (e.g., increase in latency) and/or usability or loss of functionality. The thesis behind this dissertation is that improved energy efficiency can be achieved through system architectures that seek to design and exploit "collaboration" among heterogeneous but functionally similar subsystems. For instance, multiple radio interfaces with different power/performance characteristics can collaborate to provide an energy-efficient wireless communication subsystem. Furthermore, we show that in systems where such heterogeneity is not naturally present, we can introduce heterogeneous components to improve overall energy efficiency. We show that using collaboration, individual subsystems and even entire platforms can be shut down more aggressively to reduce energy consumption, while reducing adverse impacts on performance or usability. We have used collaboration to do energy efficient operation in several contexts. For battery powered mobile devices we show that wireless radios are the dominant power consumers, and then describe several techniques that use various heterogeneous radios present

  11. Efficient electrochemical CO2 conversion powered by renewable energy

    DOE PAGESBeta

    Kauffman, Douglas R.; Thakkar, Jay; Siva, Rajan; Matranga, Christopher; Ohodnicki, Paul R.; Zeng, Chenjie; Jin, Rongchao

    2015-06-29

    Here, the catalytic conversion of CO2 into industrially relevant chemicals is one strategy for mitigating greenhouse gas emissions. Along these lines, electrochemical CO2 conversion technologies are attractive because they can operate with high reaction rates at ambient conditions. However, electrochemical systems require electricity, and CO2 conversion processes must integrate with carbon-free, renewable-energy sources to be viable on larger scales. We utilize Au25 nanoclusters as renewably powered CO2 conversion electrocatalysts with CO2 → CO reaction rates between 400 and 800 L of CO2 per gram of catalytic metal per hour and product selectivities between 80 and 95%. These performance metrics correspondmore » to conversion rates approaching 0.8–1.6 kg of CO2 per gram of catalytic metal per hour. We also present data showing CO2 conversion rates and product selectivity strongly depend on catalyst loading. Optimized systems demonstrate stable operation and reaction turnover numbers (TONs) approaching 6 × 106 mol CO2 molcatalyst–1 during a multiday (36 hours total hours) CO2electrolysis experiment containing multiple start/stop cycles. TONs between 1 × 106 and 4 × 106 molCO2 molcatalyst–1 were obtained when our system was powered by consumer-grade renewable-energy sources. Daytime photovoltaic-powered CO2 conversion was demonstrated for 12 h and we mimicked low-light or nighttime operation for 24 h with a solar-rechargeable battery. This proof-of-principle study provides some of the initial performance data necessary for assessing the scalability and technical viability of electrochemical CO2 conversion technologies. Specifically, we show the following: (1) all electrochemical CO2 conversion systems will produce a net increase in CO2 emissions if they do not integrate with renewable-energy sources, (2) catalyst loading vs activity trends can be used to tune process rates and product distributions, and (3) state-of-the-art renewable-energy technologies

  12. Efficient electrochemical CO2 conversion powered by renewable energy.

    PubMed

    Kauffman, Douglas R; Thakkar, Jay; Siva, Rajan; Matranga, Christopher; Ohodnicki, Paul R; Zeng, Chenjie; Jin, Rongchao

    2015-07-22

    The catalytic conversion of CO2 into industrially relevant chemicals is one strategy for mitigating greenhouse gas emissions. Along these lines, electrochemical CO2 conversion technologies are attractive because they can operate with high reaction rates at ambient conditions. However, electrochemical systems require electricity, and CO2 conversion processes must integrate with carbon-free, renewable-energy sources to be viable on larger scales. We utilize Au25 nanoclusters as renewably powered CO2 conversion electrocatalysts with CO2 → CO reaction rates between 400 and 800 L of CO2 per gram of catalytic metal per hour and product selectivities between 80 and 95%. These performance metrics correspond to conversion rates approaching 0.8-1.6 kg of CO2 per gram of catalytic metal per hour. We also present data showing CO2 conversion rates and product selectivity strongly depend on catalyst loading. Optimized systems demonstrate stable operation and reaction turnover numbers (TONs) approaching 6 × 10(6) molCO2 molcatalyst(-1) during a multiday (36 h total hours) CO2 electrolysis experiment containing multiple start/stop cycles. TONs between 1 × 10(6) and 4 × 10(6) molCO2 molcatalyst(-1) were obtained when our system was powered by consumer-grade renewable-energy sources. Daytime photovoltaic-powered CO2 conversion was demonstrated for 12 h and we mimicked low-light or nighttime operation for 24 h with a solar-rechargeable battery. This proof-of-principle study provides some of the initial performance data necessary for assessing the scalability and technical viability of electrochemical CO2 conversion technologies. Specifically, we show the following: (1) all electrochemical CO2 conversion systems will produce a net increase in CO2 emissions if they do not integrate with renewable-energy sources, (2) catalyst loading vs activity trends can be used to tune process rates and product distributions, and (3) state-of-the-art renewable-energy technologies are sufficient

  13. Measurements of Conversion Efficiency for a Flat Plate Thermophotovoltaic System Using a Photonic Cavity Test System

    SciTech Connect

    E.J. Brown; C.T. Ballinger; S.R. Burger; G.W. Charache; L.R. Danielson; D.M. DePoy; T.J. Donovan; M. LoCascio

    2000-05-30

    The performance of a 1 cm{sup 2} thermophotovoltaic (TPV) module was recently measured in a photonic cavity test system. A conversion efficiency of 11.7% was measured at a radiator temperature of 1076 C and a module temperature of 29.9 C. This experiment achieved the highest direct measurement of efficiency for an integrated TPV system. Efficiency was calculated from the ratio of the peak (load matched) electrical power output and the heat absorption rate. Measurements of these two parameters were made simultaneously to assure the validity of the measured efficiency value. This test was conducted in a photonic cavity which mimicked a typical flat-plate TPV system. The radiator was a large, flat graphite surface. The module was affixed to the top of a copper pedestal for heat absorption measurements. The heat absorption rate was proportional to the axial temperature gradient in the pedestal under steady-state conditions. The test was run in a vacuum to eliminate conductive and convective heat transfer mechanisms. The photonic cavity provides the optimal test environment for TPV efficiency measurements because it incorporates all important physical phenomena found in an integrated TPV system: high radiator emissivity and blackbody spectral shape, photon recycling, Lambertian distribution of incident radiation and complex geometric effects. Furthermore, the large aspect ratio between radiating surface area and radiator/module spacing produces a view factor approaching unity with minimal photon leakage.

  14. Ecological conversion efficiency and its influencers in twelve species of fish in the Yellow Sea Ecosystem

    NASA Astrophysics Data System (ADS)

    Tang, Qisheng; Guo, Xuewu; Sun, Yao; Zhang, Bo

    2007-09-01

    The ecological conversion efficiencies in twelve species of fish in the Yellow Sea Ecosystem, i.e., anchovy ( Engraulis japonicus), rednose anchovy ( Thrissa kammalensis), chub mackerel ( Scomber japonicus), halfbeak ( Hyporhamphus sajori), gizzard shad ( Konosirus punctatus), sand lance ( Ammodytes personatus), red seabream ( Pagrus major), black porgy ( Acanthopagrus schlegeli), black rockfish ( Sebastes schlegeli), finespot goby ( Chaeturichthys stigmatias), tiger puffer ( Takifugu rubripes), and fat greenling ( Hexagrammos otakii), were estimated through experiments conducted either in situ or in a laboratory. The ecological conversion efficiencies were significantly different among these species. As indicated, the food conversion efficiencies and the energy conversion efficiencies varied from 12.9% to 42.1% and from 12.7% to 43.0%, respectively. Water temperature and ration level are the main factors influencing the ecological conversion efficiencies of marine fish. The higher conversion efficiency of a given species in a natural ecosystem is acquired only under the moderate environment conditions. A negative relationship between ecological conversion efficiency and trophic level among ten species was observed. Such a relationship indicates that the ecological efficiency in the upper trophic levels would increase after fishing down marine food web in the Yellow Sea ecosystem.

  15. Optimal oxide-aperture for improving the power conversion efficiency of VCSEL arrays

    NASA Astrophysics Data System (ADS)

    Wang, Wen-Juan; Li, Chong; Zhou, Hong-Yi; Wu, Hua; Luan, Xin-Xin; Shi, Lei; Guo, Xia

    2015-02-01

    The maximum power conversion efficiencies of the top-emitting, oxide-confined, two-dimensional integrated 2×2 and 4×4 vertical-cavity surface-emitting laser (VCSEL) arrays with the oxide-apertures of 6 μm, 16 μm, 19 μm, 26 μm, 29 μm, 36 μm, 39 μm, and 46 μm are fabricated and characterized, respectively. The maximum power conversion efficiencies increase rapidly with the augment of oxide-aperture at the beginning and then decrease slowly. A maximum value of 27.91% at an oxide-aperture of 18.6 μm is achieved by simulation. The experimental data are well consistent with the simulation results, which are analyzed by utilizing an empirical model. Project supported by the National Natural Science Foundation of China (Grant Nos. 61222501 and 61335004) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111103110019)

  16. Ultra-broadband and high-efficiency polarization conversion metasurface with multiple plasmon resonance modes

    NASA Astrophysics Data System (ADS)

    Dong, Guo-Xiang; Shi, Hong-Yu; Xia, Song; Li, Wei; Zhang, An-Xue; Xu, Zhuo; Wei, Xiao-Yong

    2016-08-01

    In this paper, we present a novel metasurface design that achieves a high-efficiency ultra-broadband cross polarization conversion. The metasurface is composed of an array of unit resonators, each of which combines an H-shaped structure and two rectangular metallic patches. Different plasmon resonance modes are excited in unit resonators and allow the polarization states to be manipulated. The bandwidth of the cross polarization converter is 82% of the central frequency, covering the range from 15.7 GHz to 37.5 GHz. The conversion efficiency of the innovative new design is higher than 90%. At 14.43 GHz and 40.95 GHz, the linearly polarized incident wave is converted into a circularly polarized wave. Project supported by the National Natural Science Foundation of China (Grant Nos. 61471292, 61331005, 61471388, 51277012, 41404095, and 61501365), the 111 Project, China (Grant No. B14040), the National Basic Research Program of China (Grant No. 2015CB654602), and the China Postdoctoral Science Foundation ( Grant No. 2015M580849).

  17. Hydrogen and oxygen production by photosynthetic water splitting: Energy and quantum conversion efficiencies

    SciTech Connect

    Greenbaum, E.

    1985-01-01

    Absolute energy and quantum conversion efficiencies based on incident radiation have been measured for five species of green algae. Experiments have been performed with broadband illumination and monochromatic illumination. Maximum efficiencies were obtained in the linear low-intensity portion of the light saturation curve. At these intensities, equivalent solar energy conversion efficiencies of 2-3% were obtained with Chlamydomonas reinhardtil 137C(+). Although this efficiency decreased to less than 0.01% at equivalent incident solar irradiances above 100 w/m)sup)2)), a knowledge of the structure of photosynthetic units and the turnover time of photosynthesis suggest a procedure to overcome this limitation. Using monochromatic illumination at 700 nm, quantum efficiencies were computed from measured energy conversion efficiencies. The maximum measured quantum efficiency for photobiological hydrogen production was 6.3% in the marine species Chlamydomonas D. This value is about 25% of the maximum theoretical value of the quantum efficiency of photobiological hydrogen production. 19 refs., 6 figs.

  18. Enhanced Conversion Efficiency of Cu(In,Ga)Se2 Solar Cells via Electrochemical Passivation Treatment.

    PubMed

    Tsai, Hung-Wei; Thomas, Stuart R; Chen, Chia-Wei; Wang, Yi-Chung; Tsai, Hsu-Sheng; Yen, Yu-Ting; Hsu, Cheng-Hung; Tsai, Wen-Chi; Wang, Zhiming M; Chueh, Yu-Lun

    2016-03-30

    Defect control in Cu(In,Ga)Se2 (CIGS) materials, no matter what the defect type or density, is a significant issue, correlating directly to PV performance. These defects act as recombination centers and can be briefly categorized into interface recombination and Shockley-Read-Hall (SRH) recombination, both of which can lead to reduced PV performance. Here, we introduce an electrochemical passivation treatment for CIGS films that can lower the oxygen concentration at the CIGS surface as observed by X-ray photoelectron spectrometer analysis. Temperature-dependent J-V characteristics of CIGS solar cells reveal that interface recombination is suppressed and an improved rollover condition can be achieved following our electrochemical treatment. As a result, the surface defects are passivated, and the power conversion efficiency performance of the solar cell devices can be enhanced from 4.73 to 7.75%. PMID:26815164

  19. Thermoelectric conversion efficiency in IV-VI semiconductors with reduced thermal conductivity

    NASA Astrophysics Data System (ADS)

    Ishida, Akihiro; Thao, Hoang Thi Xuan; Yamamoto, Hidenari; Kinoshita, Yohei; Ishikiriyama, Mamoru

    2015-10-01

    Mid-temperature thermoelectric conversion efficiencies of the IV-VI materials were calculated under the Boltzmann transport theory of carriers, taking the Seebeck, Peltier, and Thomson effects into account. The conversion efficiency was discussed with respect to the lattice thermal conductivity, keeping other parameters such as Seebeck coefficient and electrical conductivity to the same values. If room temperature lattice thermal conductivity is decreased up to 0.5W/mK, the conversion efficiency of a PbS based material becomes as high as 15% with the temperature difference of 500K between 800K and 300K.

  20. Highly efficient industrial large-area black silicon solar cells achieved by surface nanostructured modification

    NASA Astrophysics Data System (ADS)

    Li, Ping; Wei, Yi; Zhao, Zengchao; Tan, Xin; Bian, Jiming; Wang, Yuxuan; Lu, Chunxi; Liu, Aimin

    2015-12-01

    Traditional black silicon solar cells show relatively low efficiencies due to the high surface recombination occurring at the front surfaces. In this paper, we present a surface modification process to suppress surface recombination and fabricate highly efficient industrial black silicon solar cells. The Ag-nanoparticle-assisted etching is applied to realize front surface nanostructures on silicon wafers in order to reduce the surface reflectance. Through a further tetramethylammonium hydroxide (TMAH) treatment, the carrier recombination at and near the surface is greatly suppressed, due to a lower surface dopant concentration after the surface modification. This modified surface presents a low reflectivity in a range of 350-1100 nm. Large-area solar cells with an average conversion efficiency of 19.03% are achieved by using the TMAH treatment of 30 s. This efficiency is 0.18% higher than that of standard silicon solar cells with pyramidal surfaces, and also a remarkable improvement compared with black silicon solar cells without TMAH modifications.

  1. Design of a highly stable, high-conversion-efficiency, optical parametric chirped-pulse amplification system with good beam quality.

    PubMed

    Guardalben, M; Keegan, J; Waxer, L; Bagnoud, V; Begishev, I; Puth, J; Zuegel, J

    2003-10-01

    An optical parametric chirped-pulse amplifier (OPCPA) design that provides 40% pump-to-signal conversion efficiency and over-500-mJ signal energy at 1054 nm for front-end injection into a Nd:glass amplifier chain is presented. This OPCPA system is currently being built as the prototype front end for the OMEGA EP (extended performance) laser system at the University of Rochester's Laboratory for Laser Energetics. Using a three-dimensional spatial and temporal numerical model, several design considerations necessary to achieve high conversion efficiency, good output stability, and good beam quality are discussed. The dependence of OPCPA output on the pump beam's spatiotemporal shape and the relative size of seed and pump beams is described. This includes the effects of pump intensity modulation and pump-signal walk-off. The trade-off among efficiency, stability, and low output beam intensity modulation is discussed. PMID:19471364

  2. Efficiency dilution: long-term exergy conversion trends in Japan.

    PubMed

    Williams, Eric; Warr, Benjamin; Ayres, Robert U

    2008-07-01

    This analysis characterizes century-scale trends in exergy efficiency in Japan. Exergy efficiency captures the degree to which energy inputs (such as coal) are converted into useful work (such as electricity or power to move a vehicle). This approach enables the estimation of net efficiencies which aggregate different technologies. Sectors specifically analyzed are electricity generation, transport, steel production, and residential space heating. One result is that the aggregate exergy efficiency of the Japanese economy declined slightly over the last half of the 20th century, reaching a high of around 38% in the late 1970s and falling to around 33% by 1998. The explanation for this is that while individual technologies improved dramatically over the century, less exergy-efficient ones were progressively adopted, yielding a net stabilization or decline. In the electricity sector, for instance, adoption of hydropower was followed by fossil-fired plants and then by nuclear power, each technology being successively less efficient from an exergy perspective. The underlying dynamic of this trend is analogous to declining ore grades in the mining sector. Increasing demand for exergy services requires expended utilization of resources from which it is more difficult to extract utility (e.g., falling water versus coal). We term this phenomenon efficiency dilution. PMID:18678034

  3. Efficient conversion from polysialogangliosides to monosialotetrahexosylganglioside using Oerskovia xanthineolytica YZ-2.

    PubMed

    Zhang, Jianguo; Cao, Dan; Shen, Danhong; Wang, Xuedong; Wei, Dongzhi

    2011-05-01

    A new sialidase-producing strain isolated from soil was identified as Oerskovia xanthineolytica YZ-2. Sialidase was produced when Oerskovia xanthineolytica YZ-2 was exposed to polysialogangliosides. The sialidase of Oerskovia xanthineolytica YZ-2 hydrolyzed sialic acid linkages in polysialogangliosides, and released monosialotetrahexosylganglioside (GM1). The sialidase had the capability of product specificity because it did not attack the sialic acid linkage in GM1. Therefore, Oerskovia xanthineolytica YZ-2 was used for GM1 production from polysialogangliosides. In flasks cultivation phase, it was proved that Oerskovia xanthineolytica YZ-2 could convert polysialogangliosides to GM1 efficiently. Scaling-up the bioprocess with 8% crude ganglioside, polysialogangliosides was converted to GM1 by Oerskovia xanthineolytica YZ-2 in 30 L bioreactor after 18 h. The relative content of GM1 increased from 16.3% in crude ganglioside to 83.7% after Oerskovia xanthineolytica YZ-2 conversion. Therefore, a simple, large-scale conversion process for GM1 production from polysialogangliosides was achieved using Oerskovia xanthineolytica YZ-2 as a biocatalyst. PMID:21153421

  4. Multiscale Modeling of Plasmon-Enhanced Power Conversion Efficiency in Nanostructured Solar Cells.

    PubMed

    Meng, Lingyi; Yam, ChiYung; Zhang, Yu; Wang, Rulin; Chen, GuanHua

    2015-11-01

    The unique optical properties of nanometallic structures can be exploited to confine light at subwavelength scales. This excellent light trapping is critical to improve light absorption efficiency in nanoscale photovoltaic devices. Here, we apply a multiscale quantum mechanics/electromagnetics (QM/EM) method to model the current-voltage characteristics and optical properties of plasmonic nanowire-based solar cells. The QM/EM method features a combination of first-principles quantum mechanical treatment of the photoactive component and classical description of electromagnetic environment. The coupled optical-electrical QM/EM simulations demonstrate a dramatic enhancement for power conversion efficiency of nanowire solar cells due to the surface plasmon effect of nanometallic structures. The improvement is attributed to the enhanced scattering of light into the photoactive layer. We further investigate the optimal configuration of the nanostructured solar cell. Our QM/EM simulation result demonstrates that a further increase of internal quantum efficiency can be achieved by scattering light into the n-doped region of the device. PMID:26722976

  5. Buckled graphene for efficient energy harvest, storage and conversion.

    PubMed

    Jiang, Jin-Wu

    2016-10-01

    Buckling is one of the most common phenomena in atom-thick layered structures like graphene. While the buckling phenomenon usually causes disaster for most nanodevices, we illustrate one positive application of buckled graphene for energy harvest, storage and conversion. More specifically, we perform molecular dynamical simulations to show that buckled graphene can be used to collect wasted mechanical energy and store the energy in the form of internal knotting potential. Through strain engineering, the knotting potential can be converted into useful kinetic (thermal) energy that is highly concentrated at the free edges of buckled graphene. The present study demonstrates potential applications of buckled graphene for converting dispersed wasted mechanical energy into concentrated useful kinetic (thermal) energy. PMID:27581194

  6. Increasing Biomass Conversion Efficiencies to Ethanol by Engineering Energy Crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The United States Government has targeted aggressive development of bioethanol as one route for decreasing oil dependence and lowering greenhouse gas emissions. Achieving future production targets depends on expanding feedstock sources beyond corn and towards lignocellulose. This is expected to in...

  7. Theoretical investigation of the spectrum and conversion efficiency of short wavelength extreme-ultraviolet light sources based on terbium plasmas

    SciTech Connect

    Sasaki, Akira; Nishihara, Katsunobu; Sunahara, Atsushi; Furukawa, Hiroyuki; Nishikawa, Takeshi; Koike, Fumihiro

    2010-12-06

    The emission spectrum and conversion efficiency of laser-produced terbium plasmas are theoretically investigated on the basis of computational atomic data. The theoretically calculated spectrum reproduces the main peak of observed spectrum at {lambda}=6.5 nm, which originates from 4d-4f transitions of near palladiumlike ions (Tb{sup 19+}). A simple model of the isothermal expansion of terbium plasma suggests that efficient emission can be achieved by pumping the plasma with a laser pulse at an intensity of approximately one order of magnitude greater than that used with tin sources at {lambda}=13.5 nm.

  8. Tuning charge balance in PHOLEDs with ambipolar host materials to achieve high efficiency

    SciTech Connect

    Padmaperuma, Asanga B.; Koech, Phillip K.; Cosimbescu, Lelia; Polikarpov, Evgueni; Swensen, James S.; Chopra, Neetu; So, Franky; Sapochak, Linda S.; Gaspar, Daniel J.

    2009-08-27

    The efficiency and stability of blue organic light emitting devices (OLEDs) continue to be a primary roadblock to developing organic solid state white lighting. For OLEDs to meet the high power conversion efficiency goal, they will require both close to 100% internal quantum efficiency and low operating voltage in a white light emitting device.1 It is generally accepted that such high quantum efficiency, can only be achieved with the use of organometallic phosphor doped OLEDs. Blue OLEDs are particularly important for solid state lighting. The simplest (and therefore likely the lowest cost) method of generating white light is to down convert part of the emission from a blue light source with a system of external phosphors.2 A second method of generating white light requires the superposition of the light from red, green and blue OLEDs in the correct ratio. Either of these two methods (and indeed any method of generating white light with a high color rendering index) critically depends on a high efficiency blue light component.3 A simple OLED generally consists of a hole-injecting anode, a preferentially hole transporting organic layer (HTL), an emissive layer that contains the recombination zone and ideally transports both holes and electrons, a preferentially electron-transporting layer (ETL) and an electron-injecting cathode. Color in state-of-the-art OLEDs is generated by an organometallic phosphor incorporated by co-sublimation into the emissive layer (EML).4 New materials functioning as hosts, emitters, charge transporting, and charge blocking layers have been developed along with device architectures leading to electrophosphorescent based OLEDs with high quantum efficiencies near the theoretical limit. However, the layers added to the device architecture to enable high quantum efficiencies lead to higher operating voltages and correspondingly lower power efficiencies. Achievement of target luminance power efficiencies will require new strategies for lowering

  9. Efficient Conversation: The Talk between Pilots and Air Traffic Controllers.

    ERIC Educational Resources Information Center

    Simmons, James L.

    Two-way radio communications between air traffic controllers using radar on the ground to give airplane pilots instructions are of interest within the developing framework of the sociology of language. The main purpose of air traffic control language is efficient communication to promote flight safety. This study describes the standardized format…

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1983-12-01

    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.

  12. Estimation of frequency conversion efficiency of THz devices using a ballistic electron wave swing circuit model

    NASA Astrophysics Data System (ADS)

    Schildbach, Christian; Ong, Duu Sheng; Hartnagel, Hans; Schmidt, Lorenz-Peter

    2016-06-01

    The ballistic electron wave swing device has previously been presented as a possible candidate for a simple power conversion technique to the THz -domain. This paper gives a simulative estimation of the power conversion efficiency. The harmonic balance simulations use an equivalent circuit model, which is also derived in this work from a mechanical model. To verify the validity of the circuit model, current waveforms are compared to Monte Carlo simulations of identical setups. Model parameters are given for a wide range of device configurations. The device configuration exhibiting the most conforming waveform is used further for determining the best conversion efficiency. The corresponding simulation setup is described. Simulation results implying a conversion efficiency of about 22% are presented.

  13. Air Force Achieves Fuel Efficiency through Industry Best Practices

    SciTech Connect

    2012-12-01

    The U.S. Air Force’s Air Mobility Command (AMC) is changing the way it does business. It is saving energy and money through an aircraft fleet fuel-efficiency program inspired by private industry best practices and ideas resulting from the empowered fuel savings culture.

  14. Fabrication of Natural Sensitizer Extracted from Mixture of Purple Cabbage, Roselle, Wormwood and Seaweed with High Conversion Efficiency for DSSC.

    PubMed

    Chang, Ho; Lai, Xuan-Rong

    2016-02-01

    This study aims to deal with the influence of different solvent in extraction of natural sensitizer and different thickness of photoelectrode thin film on the photoelectric conversion efficiency and the electron transport properties for the prepared dye-sensitized solar cells (DSSC). The natural dyes of anthocyanin and chlorophyll dyes are extracted from mixture of purple cabbage and roselle and mixture of wormwood and seaweed, respectively. The experimental results show the cocktail dye extracted with ethanol and rotating speed of spin coating at 1000 rpm can achieve the greatest photoelectric conversion efficiency up to 1.85%. Electrochemical impedance result shows that the effective diffusion coefficient for the prepared DSSC with the thickness of photoelectrode thin film at 21 microm are 5.23 x 10(-4) cm2/s. PMID:27433731

  15. An efficient algorithm for geocentric to geodetic coordinate conversion

    SciTech Connect

    Toms, R.M.

    1995-09-01

    The problem of performing transformations from geocentric to geodetic coordinates has received an inordinate amount of attention in the literature. Numerous approximate methods have been published. Almost none of the publications address the issue of efficiency and in most cases there is a paucity of error analysis. Recently there has been a surge of interest in this problem aimed at developing more efficient methods for real time applications such as DIS. Iterative algorithms have been proposed that are not of optimal efficiency, address only one error component and require a small but uncertain number of relatively expensive iterations for convergence. In this paper a well known rapidly convergent iterative approach is modified to eliminate intervening trigonometric function evaluations. A total error metric is defined that accounts for both angular and altitude errors. The initial guess is optimized to minimize the error for one iteration. The resulting algorithm yields transformations correct to one centimeter for altitudes out to one million kilometers. Due to the rapid convergence only one iteration is used and no stopping test is needed. This algorithm is discussed in the context of machines that have FPUs and legacy machines that utilize mathematical subroutine packages.

  16. Telescoping Solar Array Concept for Achieving High Packaging Efficiency

    NASA Technical Reports Server (NTRS)

    Mikulas, Martin; Pappa, Richard; Warren, Jay; Rose, Geoff

    2015-01-01

    Lightweight, high-efficiency solar arrays are required for future deep space missions using high-power Solar Electric Propulsion (SEP). Structural performance metrics for state-of-the art 30-50 kW flexible blanket arrays recently demonstrated in ground tests are approximately 40 kW/cu m packaging efficiency, 150 W/kg specific power, 0.1 Hz deployed stiffness, and 0.2 g deployed strength. Much larger arrays with up to a megawatt or more of power and improved packaging and specific power are of interest to mission planners for minimizing launch and life cycle costs of Mars exploration. A new concept referred to as the Compact Telescoping Array (CTA) with 60 kW/cu m packaging efficiency at 1 MW of power is described herein. Performance metrics as a function of array size and corresponding power level are derived analytically and validated by finite element analysis. Feasible CTA packaging and deployment approaches are also described. The CTA was developed, in part, to serve as a NASA reference solar array concept against which other proposed designs of 50-1000 kW arrays for future high-power SEP missions could be compared.

  17. Segregated tandem filter for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Brown, Edward J.; Baldasaro, Paul F.; Dziendziel, Randolph J.

    1997-01-01

    A filter system to transmit short wavelength radiation and reflect long wavelength radiation for a thermophotovoltaic energy conversion cell comprises an optically transparent substrate segregation layer with at least one coherent wavelength in optical thickness; a dielectric interference filter deposited on one side of the substrate segregation layer, the interference filter being disposed toward the source of radiation, the interference filter including a plurality of alternating layers of high and low optical index materials adapted to change from transmitting to reflecting at a nominal wavelength .lambda..sub.IF approximately equal to the bandgap wavelength .lambda..sub.g of the thermophotovoltaic cell, the interference filter being adapted to transmit incident radiation from about 0.5.lambda..sub.IF to .lambda..sub.IF and reflect from .lambda..sub.IF to about 2.lambda..sub.IF ; and a high mobility plasma filter deposited on the opposite side of the substrate segregation layer, the plasma filter being adapted to start to become reflecting at a wavelength of about 1.5.lambda..sub.IF.

  18. Segregated tandem filter for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    DOEpatents

    Brown, E.J.; Baldasaro, P.F.; Dziendziel, R.J.

    1997-12-23

    A filter system to transmit short wavelength radiation and reflect long wavelength radiation for a thermophotovoltaic energy conversion cell comprises an optically transparent substrate segregation layer with at least one coherent wavelength in optical thickness; a dielectric interference filter deposited on one side of the substrate segregation layer, the interference filter being disposed toward the source of radiation, the interference filter including a plurality of alternating layers of high and low optical index materials adapted to change from transmitting to reflecting at a nominal wavelength {lambda}{sub IF} approximately equal to the bandgap wavelength {lambda}{sub g} of the thermophotovoltaic cell, the interference filter being adapted to transmit incident radiation from about 0.5{lambda}{sub IF} to {lambda}{sub IF} and reflect from {lambda}{sub IF} to about 2{lambda}{sub IF}; and a high mobility plasma filter deposited on the opposite side of the substrate segregation layer, the plasma filter being adapted to start to become reflecting at a wavelength of about 1.5{lambda}{sub IF}. 10 figs.

  19. Segregated tandem filter for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

    SciTech Connect

    Brown, E.J.; Baldasaro, P.F.; Dziendziel, R.J.

    1996-12-31

    A filter system to transmit short wavelength radiation and reflect long wavelength radiation for a thermophotovoltaic energy conversion cell comprises an optically transparent substrate segregation layer with at least one coherent wavelength in optical thickness; a dielectric interference filter deposited on one side of the substrate segregation layer, the interference filter being disposed toward the source of radiation, the interference filter including a plurality of alternating layers of high and low optical index materials adapted to change from transmitting to reflecting at a nominal wavelength {lambda}{sub IF} approximately equal to the bandgap wavelength {lambda}{sub g} of the thermophotovoltaic cell, the interference filter being adapted to transmit incident radiation from about 0.5{lambda}{sub IF} to {lambda}{sub IF} and reflect from {lambda}{sub IF} to about 2{lambda}{sub IF}; and a high mobility plasma filter deposited on the opposite side of the substrate segregation layer, the plasma filter being adapted to start to become reflecting at a wavelength of about 1.5{lambda}{sub IF}.

  20. Achieving improved cycle efficiency via pressure gain combustors

    SciTech Connect

    Gemmen, R.S.; Janus, M.C.; Richards, G.A.; Norton, T.S.; Rogers, W.A.

    1995-04-01

    As part of the Department of Energy`s Advanced Gas Turbine Systems Program, an investigation is being performed to evaluate ``pressure gain`` combustion systems for gas turbine applications. This paper presents experimental pressure gain and pollutant emission data from such combustion systems. Numerical predictions for certain combustor geometries are also presented. It is reported that for suitable aerovalved pulse combustor geometries studied experimentally, an overall combustor pressure gain of nearly 1 percent can be achieved. It is also shown that for one combustion system operating under typical gas turbine conditions, NO{sub x} and CO emmissions, are about 30 ppmv and 8 ppmv, respectively.

  1. 10 CFR 433.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Water used to achieve energy efficiency. 433.7 Section 433.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR NEW FEDERAL COMMERCIAL AND MULTI-FAMILY HIGH-RISE RESIDENTIAL BUILDINGS § 433.7 Water used to achieve energy efficiency....

  2. 10 CFR 433.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Water used to achieve energy efficiency. 433.7 Section 433.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR NEW FEDERAL COMMERCIAL AND MULTI-FAMILY HIGH-RISE RESIDENTIAL BUILDINGS § 433.7 Water used to achieve energy efficiency....

  3. 10 CFR 433.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Water used to achieve energy efficiency. 433.7 Section 433.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR THE DESIGN AND... achieve energy efficiency....

  4. 10 CFR 433.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 false Water used to achieve energy efficiency. 433.7 Section 433.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR NEW FEDERAL COMMERCIAL AND MULTI-FAMILY HIGH-RISE RESIDENTIAL BUILDINGS § 433.7 Water used to achieve energy efficiency....

  5. 10 CFR 433.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 3 2011-01-01 2011-01-01 false Water used to achieve energy efficiency. 433.7 Section 433.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR THE DESIGN AND... achieve energy efficiency....

  6. Experimental feasibility of the airborne measurement of absolute oil fluorescence spectral conversion efficiency

    NASA Technical Reports Server (NTRS)

    Hoge, F. E.; Swift, R. N.

    1983-01-01

    Airborne lidar oil spill experiments carried out to determine the practicability of the AOFSCE (absolute oil fluorescence spectral conversion efficiency) computational model are described. The results reveal that the model is suitable over a considerable range of oil film thicknesses provided the fluorescence efficiency of the oil does not approach the minimum detection sensitivity limitations of the lidar system. Separate airborne lidar experiments to demonstrate measurement of the water column Raman conversion efficiency are also conducted to ascertain the ultimate feasibility of converting such relative oil fluorescence to absolute values. Whereas the AOFSCE model is seen as highly promising, further airborne water column Raman conversion efficiency experiments with improved temporal or depth-resolved waveform calibration and software deconvolution techniques are thought necessary for a final determination of suitability.

  7. High Conversion Efficiency and Power Stability of 532 nm Generation from an External Frequency Doubling Cavity

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Lin, Bai-Ke; Li, Ye; Zhang, Hong-Xi; Cao, Jian-Ping; Fang, Zhan-Jun; Li, Tian-Chu; Zang, Er-Jun

    2012-09-01

    We present a high-efficiency 532 nm green light conversion from an external cavity-enhanced second harmonic generation (SHG) with a periodically poled KTP crystal (PPKTP). The cavity is a bow-tie ring configuration with a unitized structure. When the impedance matching is optimized, the coupling efficiency of the fundamental is as high as 95%. Taking into account both the high power output of the second harmonic and the stability of the system, we obtain over 500 mW green passing through the output cavity mirror, corresponding to a net conversion efficiency higher than 75.2%. Under these operating conditions, the power stability is better than ±0.25% during 5 h. It is the highest conversion efficiency and power stability ever produced in the bow-tie ring cavity with PPKTP for 532 nm generation.

  8. Maximum efficiency of state-space models of nanoscale energy conversion devices

    NASA Astrophysics Data System (ADS)

    Einax, Mario; Nitzan, Abraham

    2016-07-01

    The performance of nano-scale energy conversion devices is studied in the framework of state-space models where a device is described by a graph comprising states and transitions between them represented by nodes and links, respectively. Particular segments of this network represent input (driving) and output processes whose properly chosen flux ratio provides the energy conversion efficiency. Simple cyclical graphs yield Carnot efficiency for the maximum conversion yield. We give general proof that opening a link that separate between the two driving segments always leads to reduced efficiency. We illustrate these general result with simple models of a thermoelectric nanodevice and an organic photovoltaic cell. In the latter an intersecting link of the above type corresponds to non-radiative carriers recombination and the reduced maximum efficiency is manifested as a smaller open-circuit voltage.

  9. Maximum efficiency of state-space models of nanoscale energy conversion devices.

    PubMed

    Einax, Mario; Nitzan, Abraham

    2016-07-01

    The performance of nano-scale energy conversion devices is studied in the framework of state-space models where a device is described by a graph comprising states and transitions between them represented by nodes and links, respectively. Particular segments of this network represent input (driving) and output processes whose properly chosen flux ratio provides the energy conversion efficiency. Simple cyclical graphs yield Carnot efficiency for the maximum conversion yield. We give general proof that opening a link that separate between the two driving segments always leads to reduced efficiency. We illustrate these general result with simple models of a thermoelectric nanodevice and an organic photovoltaic cell. In the latter an intersecting link of the above type corresponds to non-radiative carriers recombination and the reduced maximum efficiency is manifested as a smaller open-circuit voltage. PMID:27394100

  10. Barriers to Achieving Textbook Multigrid Efficiency (TME) in CFD

    NASA Technical Reports Server (NTRS)

    Brandt, Achi

    1998-01-01

    As a guide to attaining this optimal performance for general CFD problems, the table below lists every foreseen kind of computational difficulty for achieving that goal, together with the possible ways for resolving that difficulty, their current state of development, and references. Included in the table are staggered and nonstaggered, conservative and nonconservative discretizations of viscous and inviscid, incompressible and compressible flows at various Mach numbers, as well as a simple (algebraic) turbulence model and comments on chemically reacting flows. The listing of associated computational barriers involves: non-alignment of streamlines or sonic characteristics with the grids; recirculating flows; stagnation points; discretization and relaxation on and near shocks and boundaries; far-field artificial boundary conditions; small-scale singularities (meaning important features, such as the complete airplane, which are not visible on some of the coarse grids); large grid aspect ratios; boundary layer resolution; and grid adaption.

  11. Solar energy conversion via hot electron internal photoemission in metallic nanostructures: Efficiency estimates

    SciTech Connect

    Leenheer, Andrew J.; Narang, Prineha; Atwater, Harry A.; Lewis, Nathan S.

    2014-04-07

    Collection of hot electrons generated by the efficient absorption of light in metallic nanostructures, in contact with semiconductor substrates can provide a basis for the construction of solar energy-conversion devices. Herein, we evaluate theoretically the energy-conversion efficiency of systems that rely on internal photoemission processes at metal-semiconductor Schottky-barrier diodes. In this theory, the current-voltage characteristics are given by the internal photoemission yield as well as by the thermionic dark current over a varied-energy barrier height. The Fowler model, in all cases, predicts solar energy-conversion efficiencies of <1% for such systems. However, relaxation of the assumptions regarding constraints on the escape cone and momentum conservation at the interface yields solar energy-conversion efficiencies as high as 1%–10%, under some assumed (albeit optimistic) operating conditions. Under these conditions, the energy-conversion efficiency is mainly limited by the thermionic dark current, the distribution of hot electron energies, and hot-electron momentum considerations.

  12. Non-native Co-, Mn-, and Ti-oxyhydroxide nanocrystals in ferritin for high efficiency solar energy conversion.

    PubMed

    Erickson, S D; Smith, T J; Moses, L M; Watt, R K; Colton, J S

    2015-01-01

    Quantum dot solar cells seek to surpass the solar energy conversion efficiencies achieved by bulk semiconductors. This new field requires a broad selection of materials to achieve its full potential. The 12 nm spherical protein ferritin can be used as a template for uniform and controlled nanocrystal growth, and to then house the nanocrystals for use in solar energy conversion. In this study, precise band gaps of titanium, cobalt, and manganese oxyhydroxide nanocrystals within ferritin were measured, and a change in band gap due to quantum confinement effects was observed. The range of band gaps obtainable from these three types of nanocrystals is 2.19-2.29 eV, 1.93-2.15 eV, and 1.60-1.65 eV respectively. From these measured band gaps, theoretical efficiency limits for a multi-junction solar cell using these ferritin-enclosed nanocrystals are calculated and found to be 38.0% for unconcentrated sunlight and 44.9% for maximally concentrated sunlight. If a ferritin-based nanocrystal with a band gap similar to silicon can be found (i.e. 1.12 eV), the theoretical efficiency limits are raised to 51.3% and 63.1%, respectively. For a current matched cell, these latter efficiencies become 41.6% (with an operating voltage of 5.49 V), and 50.0% (with an operating voltage of 6.59 V), for unconcentrated and maximally concentrated sunlight respectively. PMID:25490522

  13. 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.

  14. High-efficiency microwave photonic harmonic down-conversion with tunable and reconfigurable filtering.

    PubMed

    Liao, Jinxin; Zheng, Xiaoping; Li, Shangyuan; Zhang, Hanyi; Zhou, Bingkun

    2014-12-01

    A new optical-frequency comb-based microwave photonic harmonic down-convertor with tunable and reconfigurable filtering is proposed and experimentally demonstrated. The coherent evenly spaced optical carriers offer harmonic down-conversion for ultrahigh radio frequency signals with low-frequency local oscillator, and construct a tunable and reconfigurable bandpass filter for the intermediate-frequency (IF) signal combined with dispersion. This implementation features high conversion efficiency. Experimental results show the filtered output IF signal has a clean spectrum with high quality. Measured conversion loss is 8.3 dB without extra electrical amplification. PMID:25490622

  15. Efficient conversion of solar energy to biomass and electricity

    PubMed Central

    2014-01-01

    The Earth receives around 1000 W.m−2 of power from the Sun and only a fraction of this light energy is able to be converted to biomass (chemical energy) via the process of photosynthesis. Out of all photosynthetic organisms, microalgae, due to their fast growth rates and their ability to grow on non-arable land using saline water, have been identified as potential source of raw material for chemical energy production. Electrical energy can also be produced from this same solar resource via the use of photovoltaic modules. In this work we propose a novel method of combining both of these energy production processes to make full utilisation of the solar spectrum and increase the productivity of light-limited microalgae systems. These two methods of energy production would appear to compete for use of the same energy resource (sunlight) to produce either chemical or electrical energy. However, some groups of microalgae (i.e. Chlorophyta) only require the blue and red portions of the spectrum whereas photovoltaic devices can absorb strongly over the full range of visible light. This suggests that a combination of the two energy production systems would allow for a full utilization of the solar spectrum allowing both the production of chemical and electrical energy from the one facility making efficient use of available land and solar energy. In this work we propose to introduce a filter above the algae culture to modify the spectrum of light received by the algae and redirect parts of the spectrum to generate electricity. The electrical energy generated by this approach can then be directed to running ancillary systems or producing extra illumination for the growth of microalgae. We have modelled an approach whereby the productivity of light-limited microalgae systems can be improved by at least 4% through using an LED array to increase the total amount of illumination on the microalgae culture. PMID:24976951

  16. Using silver nanowire antennas to enhance the conversion efficiency of photoresponsive DNA nanomotors

    PubMed Central

    Yuan, Quan; Zhang, Yunfei; Chen, Yan; Wang, Ruowen; Du, Chaoling; Yasun, Emir; Tan, Weihong

    2011-01-01

    Plasmonic near-field coupling can induce the enhancement of photoresponsive processes by metal nanoparticles. Advances in nanostructured metal synthesis and theoretical modeling have kept surface plasmons in the spotlight. Previous efforts have resulted in significant intensity enhancement of organic dyes and quantum dots and increased absorption efficiency of optical materials used in solar cells. Here, we report that silver nanostructures can enhance the conversion efficiency of an interesting type of photosensitive DNA nanomotor through coupling with incorporated azobenzene moieties. Spectral overlap between the azobenzene absorption band and plasmonic resonances of silver nanowires increases light absorption of photon-sensitive DNA motor molecules, leading to 85% close-open conversion efficiency. The experimental results are consistent with our theoretical calculations of the electric field distribution. This enhanced conversion of DNA nanomotors holds promise for the development of new types of molecular nanodevices for light manipulative processes and solar energy harvesting. PMID:21596999

  17. High electrokinetic energy conversion efficiency in charged nanoporous nitrocellulose/sulfonated polystyrene membranes.

    PubMed

    Haldrup, Sofie; Catalano, Jacopo; Hansen, Michael Ryan; Wagner, Manfred; Jensen, Grethe Vestergaard; Pedersen, Jan Skov; Bentien, Anders

    2015-02-11

    The synthesis, characterization, and electrokinetic energy conversion performance have been investigated experimentally in a charged polymeric membrane based on a blend of nitrocellulose and sulfonated polystyrene. The membrane is characterized by a moderate ion exchange capacity and a relatively porous structure with average pore diameter of 11 nm. With electrokinetic energy conversion, pressure can be converted directly into electric energy and vice versa. From the electrokinetic transport properties, a remarkably large intrinsic maximum efficiency of 46% is found. It is anticipated that the results are an experimental verification of theoretical models that predict high electrokinetic energy conversion efficiency in pores with high permselectivity and hydrodynamic slip flow. Furthermore, the result is a promising step for obtaining efficient low-cost electrokinetic generators and pumps for small or microscale applications. PMID:25555128

  18. Resolving Anomalies in Predicting Electrokinetic Energy Conversion Efficiencies of Nanofluidic Devices

    PubMed Central

    Majumder, Sagardip; Dhar, Jayabrata; Chakraborty, Suman

    2015-01-01

    We devise a new approach for capturing complex interfacial interactions over reduced length scales, towards predicting electrokinetic energy conversion efficiencies of nanofluidic devices. By embedding several aspects of intermolecular interactions in continuum based formalism, we show that our simple theory becomes capable of representing complex interconnections between electro-mechanics and hydrodynamics over reduced length scales. The predictions from our model are supported by reported experimental data, and are in excellent quantitative agreement with molecular dynamics simulations. The present model, thus, may be employed to rationalize the discrepancies between low energy conversion efficiencies of nanofluidic channels that have been realized from experiments, and the impractically high energy conversion efficiencies that have been routinely predicted by the existing theories. PMID:26437925

  19. Conversion efficiency in the process of copolarized spontaneous four-wave mixing

    SciTech Connect

    Garay-Palmett, Karina; U'Ren, Alfred B.; Rangel-Rojo, Raul

    2010-10-15

    We study the process of copolarized spontaneous four-wave mixing in single-mode optical fibers, with an emphasis on an analysis of the conversion efficiency. We consider both the monochromatic-pump and pulsed-pump regimes, as well as both the degenerate-pump and nondegenerate-pump configurations. We present analytical expressions for the conversion efficiency, which are given in terms of double integrals. In the case of pulsed pumps we take these expressions to closed analytical form with the help of certain approximations. We present results of numerical simulations, and compare them to values obtained from our analytical expressions, for the conversion efficiency as a function of several key experimental parameters.

  20. Advances with vertical epitaxial heterostructure architecture (VEHSA) phototransducers for optical to electrical power conversion efficiencies exceeding 50 percent

    NASA Astrophysics Data System (ADS)

    Fafard, S.; Proulx, F.; York, M. C. A.; Wilkins, M.; Valdivia, C. E.; Bajcsy, M.; Ban, D.; Jaouad, A.; Bouzazi, B.; Arès, R.; Aimez, V.; Hinzer, K.; Masson, D. P.

    2016-03-01

    A monolithic compound semiconductor phototransducer optimized for narrow-band light sources was designed for and has achieved conversion efficiencies exceeding 50%. The III-V heterostructure was grown by MOCVD, based on the vertical stacking of a number of partially absorbing GaAs n/p junctions connected in series with tunnel junctions. The thicknesses of the p-type base layers of the diodes were engineered for optimal absorption and current matching for an optical input with wavelengths centered in the 830 nm to 850 nm range. The device architecture allows for improved open-circuit voltage in the individual base segments due to efficient carrier extraction while simultaneously maintaining a complete absorption of the input photons with no need for complicated fabrication processes or reflecting layers. Progress for device outputs achieving in excess of 12 V is reviewed in this study.

  1. Recovery Act: Integrated DC-DC Conversion for Energy-Efficient Multicore Processors

    SciTech Connect

    Shepard, Kenneth L

    2013-03-31

    In this project, we have developed the use of thin-film magnetic materials to improve in energy efficiency of digital computing applications by enabling integrated dc-dc power conversion and management with on-chip power inductors. Integrated voltage regulators also enables fine-grained power management, by providing dynamic scaling of the supply voltage in concert with the clock frequency of synchronous logic to throttle power consumption at periods of low computational demand. The voltage converter generates lower output voltages during periods of low computational performance requirements and higher output voltages during periods of high computational performance requirements. Implementation of integrated power conversion requires high-capacity energy storage devices, which are generally not available in traditional semiconductor processes. We achieve this with integration of thin-film magnetic materials into a conventional complementary metal-oxide-semiconductor (CMOS) process for high-quality on-chip power inductors. This project includes a body of work conducted to develop integrated switch-mode voltage regulators with thin-film magnetic power inductors. Soft-magnetic materials and inductor topologies are selected and optimized, with intent to maximize efficiency and current density of the integrated regulators. A custom integrated circuit (IC) is designed and fabricated in 45-nm CMOS silicon-on-insulator (SOI) to provide the control system and power-train necessary to drive the power inductors, in addition to providing a digital load for the converter. A silicon interposer is designed and fabricated in collaboration with IBM Research to integrate custom power inductors by chip stacking with the 45-nm CMOS integrated circuit, enabling power conversion with current density greater than 10A/mm2. The concepts and designs developed from this work enable significant improvements in performance-per-watt of future microprocessors in servers, desktops, and mobile

  2. Electrode Build-Up of Reducible Metal Composites toward Achievable Electrochemical Conversion of Carbon Dioxide.

    PubMed

    Lee, Seunghwa; Lee, Jaeyoung

    2016-02-19

    At the beginning of the 21st century, our world is faced with a global-warming problem due to the continuous increase in carbon dioxide emission, and thus, the development of novel experimental techniques is needed. The electrochemical conversion of carbon dioxide into high-value organic compounds could be of vital importance to solve this issue. The biggest challenge has always been to develop an electrocatalyst that is chemically active and structurally stable. Herein, previous studies, recent approaches, and current points of view on the electrode structure of metal oxide composites for the advanced electrochemical conversion of carbon dioxide are reviewed. PMID:26610065

  3. Efficient multicast routing in wavelength-division-multiplexing networks with light splitting and wavelength conversion

    NASA Astrophysics Data System (ADS)

    Zheng, Sheng; Tian, Jinwen; Liu, Jian

    2005-04-01

    We propose wavelength-division-multiplexing (WDM) networks with light splitting and wavelength conversion that can efficiently support multicast routing between nodes. Our iterative algorithm analyzes the original multicast routing network by decomposing it into multicast subgroups. These subgroups have the same wavelength, and the individual subgroup is combined to build a multicast tree. From the multicast tree, we can compute efficiently to multicast for short paths. Numerical results obtained for the ARPANET show that our algorithm can greatly reduce the optical blocking probability and the number of required wavelength conversions.

  4. THz pulse shaping and improved optical-to-THz conversion efficiency using a binary phase mask.

    PubMed

    Ropagnol, Xavier; Morandotti, Roberto; Ozaki, Tsuneyuki; Reid, Matt

    2011-07-15

    We demonstrate improved optical-to-terahertz (THz) conversion efficiency and THz pulse shaping from an interdigitated GaAs large area photoconductive antenna by using a binary phase mask. The binary phase mask results in a time-delayed excitation of the adjacent antennas, which allows subsequent antennas to produce an additive field, thus resulting in a quasi-single-cycle THz pulse. We demonstrate control over the temporal profile of the THz waveform to maximize optical-to-THz conversion efficiency. PMID:21765501

  5. Polymer:fullerene solar cells: materials, processing issues, and cell layouts to reach power conversion efficiency over 10%, a review

    NASA Astrophysics Data System (ADS)

    Etxebarria, Ikerne; Ajuria, Jon; Pacios, Roberto

    2015-01-01

    In spite of the impressive development achieved by organic photovoltaics throughout the last decades, especially in terms of reported power conversion efficiencies, there are still important technological and fundamental obstacles to circumvent before they can be implemented into reliable and long-lasting applications. Regarding device processing, the synthesis of highly soluble polymeric semiconductors first, and then fullerene derivatives, was initially considered as an important breakthrough that would definitely change the fabrication of photovoltaics once and for all. The potential and the expectation raised by this technology is such that it is very difficult to keep track of the most significant progresses being now published in different and even monographic journals. In this paper, we review the development of polymeric solar cells from its origin to the most efficient devices published to date. We separate these achievements into three different categories traditionally followed by the scientific community to push devices over 10% power conversion efficiency: active materials, strategies-fabrication/processing procedures-that can mainly modify the active film morphology, and all the different cell layout/architectures that have been used in order to extract as high a photocurrent as possible from the Sun. The synthesis of new donors, the use of additives and postprocessing techniques, buffer interlayers, inverted and tandem designs are some of the most important aspects that are reviewed in detail in this paper. All have equally contributed to develop this technology and bring it at the doors of commercialization.

  6. Efficient dense blur map estimation for automatic 2D-to-3D conversion

    NASA Astrophysics Data System (ADS)

    Vosters, L. P. J.; de Haan, G.

    2012-03-01

    Focus is an important depth cue for 2D-to-3D conversion of low depth-of-field images and video. However, focus can be only reliably estimated on edges. Therefore, Bea et al. [1] first proposed an optimization based approach to propagate focus to non-edge image portions, for single image focus editing. While their approach produces accurate dense blur maps, the computational complexity and memory requirements for solving the resulting sparse linear system with standard multigrid or (multilevel) preconditioning techniques, are infeasible within the stringent requirements of the consumer electronics and broadcast industry. In this paper we propose fast, efficient, low latency, line scanning based focus propagation, which mitigates the need for complex multigrid or (multilevel) preconditioning techniques. In addition we propose facial blur compensation to compensate for false shading edges that cause incorrect blur estimates in people's faces. In general shading leads to incorrect focus estimates, which may lead to unnatural 3D and visual discomfort. Since visual attention mostly tends to faces, our solution solves the most distracting errors. A subjective assessment by paired comparison on a set of challenging low-depth-of-field images shows that the proposed approach achieves equal 3D image quality as optimization based approaches, and that facial blur compensation results in a significant improvement.

  7. Homogeneous Photosensitization of Complex TiO2 Nanostructures for Efficient Solar Energy Conversion

    PubMed Central

    Luo, Jingshan; Karuturi, Siva Krishna; Liu, Lijun; Su, Liap Tat; Tok, Alfred Iing Yoong; Fan, Hong Jin

    2012-01-01

    TiO2 nanostructures-based photoelectrochemical (PEC) cells are under worldwide attentions as the method to generate clean energy. For these devices, narrow-bandgap semiconductor photosensitizers such as CdS and CdSe are commonly used to couple with TiO2 in order to harvest the visible sunlight and to enhance the conversion efficiency. Conventional methods for depositing the photosensitizers on TiO2 such as dip coating, electrochemical deposition and chemical-vapor-deposition suffer from poor control in thickness and uniformity, and correspond to low photocurrent levels. Here we demonstrate a new method based on atomic layer deposition and ion exchange reaction (ALDIER) to achieve a highly controllable and homogeneous coating of sensitizer particles on arbitrary TiO2 substrates. PEC tests made to CdSe-sensitized TiO2 inverse opal photoanodes result in a drastically improved photocurrent level, up to ~15.7 mA/cm2 at zero bias (vs Ag/AgCl), more than double that by conventional techniques such as successive ionic layer adsorption and reaction. PMID:22693653

  8. Efficient and low-noise single-photon-level frequency conversion interfaces using silicon nanophotonics

    NASA Astrophysics Data System (ADS)

    Li, Qing; Davanço, Marcelo; Srinivasan, Kartik

    2016-06-01

    Optical frequency conversion has applications ranging from tunable light sources to telecommunications-band interfaces for quantum information science. Here, we demonstrate efficient, low-noise frequency conversion on a nanophotonic chip through four-wave-mixing Bragg scattering in compact (footprint <0.5 × 10–4 cm2) Si3N4 microring resonators. We investigate three frequency conversion configurations: spectral translation over a few nanometres within the 980 nm band; upconversion from 1,550 nm to 980 nm and downconversion from 980 nm to 1,550 nm. With conversion efficiencies ranging from 25% for the first process to >60% for the last two processes, a signal conversion bandwidth of >1 GHz, a required continuous-wave pump power of <60 mW and background noise levels between a few femtowatts and a few picowatts, these devices are suitable for quantum frequency conversion of single-photon states from InAs/GaAs quantum dots. Simulations based on coupled mode equations and the Lugiato–Lefever equation are used to model device performance, and show quantitative agreement with measurements.

  9. Efficient ortho-para conversion of H2 on interstellar grain surfaces

    NASA Astrophysics Data System (ADS)

    Bron, Emeric; Le Petit, Franck; Le Bourlot, Jacques

    2016-04-01

    Context. Fast surface conversion between ortho- and para-H2 has been observed in laboratory studies, and it has been proposed that this mechanism plays a role in the control of the ortho-para ratio in the interstellar medium. Observations of rotational lines of H2 in photo-dissociation regions (PDRs) have indeed found significantly lower ortho-para ratios than expected at equilibrium. The mechanisms controlling the balance of the ortho-para ratio in the interstellar medium thus remain incompletely understood, while this ratio can affect the thermodynamical properties of the gas (equation of state, cooling function). Aims: We aim to build an accurate model of ortho-para conversion on dust surfaces based on the most recent experimental and theoretical results, and to validate it by comparison to observations of H2 rotational lines in PDRs. Methods: We propose a statistical model of ortho-para conversion on dust grains with fluctuating dust temperatures. It is based on a master equation approach. This computation is then coupled to full PDR models and compared to PDR observations. Results: We show that the observations of rotational H2 lines indicate a high conversion efficiency on dust grains and that this high efficiency can be accounted for if taking dust temperature fluctuations into account with our statistical model of surface conversion. Simpler models that neglect the dust temperature fluctuations do not reach the high efficiency deduced from the observations. Moreover, this high efficiency induced by dust temperature fluctuations is very insensitive to the values of the model's microphysical parameters. Conclusions: Ortho-para conversion on grains is thus an efficient mechanism in most astrophysical conditions and can play a significant role in controlling the ortho-para ratio.

  10. Efficient and coherent frequency conversions and nonlinear interference in optical parametric and atomic Raman processes

    NASA Astrophysics Data System (ADS)

    Ding, Yu

    By implementing a parametric down-conversion process with a strong signal field injection, we demonstrate that frequency down-conversion from pump photons to idler photons can be a coherent process. Contrary to a common misconception, we show that the process can be free of quantum noise. With an interference experiment, we demonstrate that coherence is preserved in the conversion process. This technique could lead to a high-fidelity quantum state transfer from a high-frequency photon to a low-frequency photon and connect a missing link in quantum networks. Coherent and efficient nonlinear interaction and frequency conversion are of great interest in many areas of quantum optics. Traditionally, the low efficiency of Raman scattering is improved by a high-finesse optical resonator or stimulated Raman conversion. It was recently found that the atomic spin wave initially built through electromagnetically induced transparency or a weak Raman process can actively enhance the Raman frequency conversion. An experimental demonstration of an efficient Raman conversion scheme with coherent feedback of both pump and Stokes fields is presented. The temporal profile of the generated Raman pulse shows that the coherence time of the atomic spin wave is ˜1.8 ms. A laser-like power threshold is observed and its low threshold is attributed to the long coherence time of the atomic spin wave. The mechanism of the conversion enhancement process is discussed and the conversion efficiency of a single pass of the beams is compared with that of double passes. Finally, a beat signal is observed between the two Stokes fields and its Fourier transform shows that the frequency difference is caused by the AC Stark effect. Precision phase measurement is traditionally restricted by the standard quantum limit. However, this limit is not as fundamental as the Heisenberg limit and can be circumvented by use of nonclassical quantum states and structure modification of the interferometers. Several

  11. Power conversion efficiency of semiconductor injection lasers and laser arrays in CW operation

    NASA Technical Reports Server (NTRS)

    Katz, J.

    1985-01-01

    The problem of optimizing power conversion efficiency of semiconductor lasers and laser arrays and minimizing efficiency degradation due to temperature effects is treated. A method for calculating this efficiency is described and some calculated results are presented and discussed. Under some conditions, a small increase in the thermal resistance of the device can result in a large reduction of its efficiency. Temperature effects are important in high-power semiconductor laser, and in particular in laser arrays, where low thermal resistance heat sinking may be crucial to the device operation.

  12. Efficient conversion of light to charge and spin in Hall-bar microdevices

    NASA Astrophysics Data System (ADS)

    Nádvorník, L.; Haigh, J. A.; Olejník, K.; Irvine, A. C.; Novák, V.; Jungwirth, T.; Wunderlich, J.

    2015-03-01

    We report an experimental study of the direct conversion of light into electrical signals in GaAs/AlGaAs Hall-bar microdevices. Our approach, based on different modulation frequencies of the intensity and polarization of the laser beam, allows us to disentangle the charge- and spin-dependent parts of the induced electrical signal and to link them to the incident light intensity and polarization, respectively. We demonstrate that the efficiency of the light to spin conversion in our electrical polarimeter is strongly enhanced by adding a drift component to the transport of the spin-polarized photocarriers, as compared to a purely diffusive transport regime of the device. For a micron-size focused laser beam, the experiments demonstrate that the light to charge and spin conversion efficiency depends on the precise position of the light spot, reflecting the spatially dependent response function of the Hall cross.

  13. Improvement of power conversion efficiency of phthalocyanine/C60 heterojunction solar cells by inserting a lithium phthalocyanine layer at the indium-tin oxide/phthalocyanine interface

    NASA Astrophysics Data System (ADS)

    Tanaka, Senku; Hanada, Toshiyuki; Ono, Koji; Watanabe, Kazuya; Yoshino, Katsumi; Hiromitsu, Ichiro

    2010-12-01

    Improvement of power conversion efficiency of a zinc phthalocyanine (ZnPc)/C60 heterojunction solar cell was achieved by inserting a lithium phthalocyanine (LiPc) layer at the indium-tin oxide (ITO)/ZnPc interface. The results of photoelectron spectroscopy suggest that the barrier height for the hole transport at the ITO/ZnPc interface is reduced by the LiPc layer. A similar improvement of the power conversion efficiency by the insertion of a LiPc layer was also observed in M-phthalocyanine (M=H2, Cu, and TiO)/C60 cells.

  14. Study of Transport Behavior and Conversion Efficiency in Pillar Structured Neutron Detectors

    SciTech Connect

    Nikolic, R

    2007-04-26

    Room temperature, high efficiency and scalable radiation detectors can be realized by manipulating materials at the micro scale. With micro-semiconductor-pillars, we will advance the thermal neutron detection efficiency of semiconductor detectors to over 70% with 50 mm in detector thickness. New material science, new transport behavior, neutron to alpha conversion dynamics and their relationship with neutron detection will be discovered with the proposed structures.

  15. Efficient amplitude-modulated pulses for triple- to single-quantum coherence conversion in MQMAS NMR.

    PubMed

    Colaux, Henri; Dawson, Daniel M; Ashbrook, Sharon E

    2014-08-01

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed "too challenging". PMID:25047226

  16. Influence of stimulated Raman scattering on the conversion efficiency in four wave mixing

    SciTech Connect

    Wunderlich, R.; Moore, M.A.; Garrett, W.R.; Payne, M.G.

    1988-01-01

    Secondary nonlinear optical effects following parametric four wave mixing in sodium vapor are investigated. The generated ultraviolet radiation induces stimulated Raman scattering and other four wave mixing process. Population transfer due to Raman transitions strongly influences the phase matching conditions for the primary mixing process. Pulse shortening and a reduction in conversion efficiency are observed. 8 refs., 3 figs.

  17. Hybrid organic/inorganic thin-film multijunction solar cells exceeding 11% power conversion efficiency.

    PubMed

    Roland, Steffen; Neubert, Sebastian; Albrecht, Steve; Stannowski, Bernd; Seger, Mark; Facchetti, Antonio; Schlatmann, Rutger; Rech, Bernd; Neher, Dieter

    2015-02-18

    Hybrid multijunction solar cells comprising hydrogenated amorphous silicon and an organic bulk heterojunction are presented, reaching 11.7% power conversion efficiency. The benefits of merging inorganic and organic subcells are pointed out, the optimization of the cells, including optical modeling predictions and tuning of the recombination contact are described, and an outlook of this technique is given. PMID:25581318

  18. Effect of end reflections on conversion efficiency of coaxial relativistic backward wave oscillator

    NASA Astrophysics Data System (ADS)

    Teng, Yan; Chen, Changhua; Sun, Jun; Shi, Yanchao; Ye, Hu; Wu, Ping; Li, Shuang; Xiong, Xiaolong

    2015-11-01

    This paper theoretically investigates the effect of end reflections on the operation of the coaxial relativistic backward wave oscillator (CRBWO). It is found that the considerable enhancement of the end reflection at one end increases the conversion efficiency, but excessively large end reflections at both ends weaken the asynchronous wave-beam interaction and thus reduce the conversion efficiency. Perfect reflection at the post end significantly improves the interaction between the electron beam and the asynchronous harmonic so that the conversion efficiency is notably increased. Based on the theoretical research, the diffraction-CRBWO with the generated microwave diffracted and output through the front end of the coaxial slow wave structure cavity is proposed. The post end is conductively closed to provide the perfect reflection. This promotes the amplitude and uniformity of the longitudinal electric field on the beam transmission line and improves the asynchronous wave-beam interaction. In numerical simulations under the diode voltage and current of 450 kV and 5.84 kA, microwave generation with the power of 1.45 GW and the conversion efficiency of 55% are obtained at the frequency of 7.45 GHz.

  19. Effect of end reflections on conversion efficiency of coaxial relativistic backward wave oscillator

    SciTech Connect

    Teng, Yan; Chen, Changhua; Sun, Jun; Shi, Yanchao; Ye, Hu; Wu, Ping; Li, Shuang; Xiong, Xiaolong

    2015-11-07

    This paper theoretically investigates the effect of end reflections on the operation of the coaxial relativistic backward wave oscillator (CRBWO). It is found that the considerable enhancement of the end reflection at one end increases the conversion efficiency, but excessively large end reflections at both ends weaken the asynchronous wave-beam interaction and thus reduce the conversion efficiency. Perfect reflection at the post end significantly improves the interaction between the electron beam and the asynchronous harmonic so that the conversion efficiency is notably increased. Based on the theoretical research, the diffraction-CRBWO with the generated microwave diffracted and output through the front end of the coaxial slow wave structure cavity is proposed. The post end is conductively closed to provide the perfect reflection. This promotes the amplitude and uniformity of the longitudinal electric field on the beam transmission line and improves the asynchronous wave-beam interaction. In numerical simulations under the diode voltage and current of 450 kV and 5.84 kA, microwave generation with the power of 1.45 GW and the conversion efficiency of 55% are obtained at the frequency of 7.45 GHz.

  20. Efficient Amplitude-Modulated Pulses for Triple- to Single-Quantum Coherence Conversion in MQMAS NMR

    PubMed Central

    2014-01-01

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed “too challenging”. PMID:25047226

  1. Fiber-Shaped Perovskite Solar Cells with High Power Conversion Efficiency.

    PubMed

    Qiu, Longbin; He, Sisi; Yang, Jiahua; Deng, Jue; Peng, Huisheng

    2016-05-01

    A perovskite solar cell fiber is created with a high power conversion efficiency of 7.1% through a controllable deposition method. A combination of aligned TiO2 nanotubes, a uniform perovskite layer, and transparent aligned carbon nanotube sheet contributes to the high photovoltaic performance. It is flexible and stable, and can be woven into smart clothes for wearable applications. PMID:27002590

  2. Courageous Conversations about Race: A Field Guide for Achieving Equity in Schools

    ERIC Educational Resources Information Center

    Singleton, Glenn E.; Linton, Curtis

    2005-01-01

    Educators are acutely aware of the statistical gaps in achievement between different racial groups. Considering the rapidly changing racial composition of student populations, how can educators reach a level of cultural proficiency necessary to eliminate this disparity? Examining the achievement gap through the prism of race, this comprehensive…

  3. 10 CFR 435.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Water used to achieve energy efficiency. 435.7 Section 435.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR NEW FEDERAL LOW-RISE RESIDENTIAL BUILDINGS Mandatory Energy Efficiency Standards for Federal Low-Rise...

  4. 10 CFR 435.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Water used to achieve energy efficiency. 435.7 Section 435.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR NEW FEDERAL LOW-RISE RESIDENTIAL BUILDINGS Mandatory Energy Efficiency Standards for Federal Low-Rise...

  5. 10 CFR 435.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Water used to achieve energy efficiency. 435.7 Section 435.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR NEW FEDERAL LOW-RISE RESIDENTIAL BUILDINGS Mandatory Energy Efficiency Standards for Federal Low-Rise...

  6. 10 CFR 435.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 3 2011-01-01 2011-01-01 false Water used to achieve energy efficiency. 435.7 Section 435.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR NEW FEDERAL LOW-RISE RESIDENTIAL BUILDINGS Mandatory Energy Efficiency Standards for Federal Low-Rise...

  7. 10 CFR 435.7 - Water used to achieve energy efficiency. [Reserved

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 false Water used to achieve energy efficiency. 435.7 Section 435.7 Energy DEPARTMENT OF ENERGY ENERGY CONSERVATION ENERGY EFFICIENCY STANDARDS FOR NEW FEDERAL LOW-RISE RESIDENTIAL BUILDINGS Mandatory Energy Efficiency Standards for Federal Low-Rise...

  8. Genetic Modification of Short Rotation Poplar Biomass Feedstock for Efficient Conversion to Ethanol

    SciTech Connect

    Dinus, R.J.

    2000-08-30

    The Bioenergy Feedstock Development Program, Environmental Sciences Division, Oak Ridge National Laboratory is developing poplars (Populus species and hybrids) as sources of renewable energy, i.e., ethanol. Notable increases in adaptability, volume productivity, and pest/stress resistance have been achieved via classical selection and breeding and intensified cultural practices. Significant advances have also been made in the efficiencies of harvesting and handling systems. Given these and anticipated accomplishments, program leaders are considering shifting some attention to genetically modifying feedstock physical and chemical properties, so as to improve the efficiency with which feedstocks can be converted to ethanol. This report provides an in-depth review and synthesis of opportunities for and feasibilities of genetically modifying feedstock qualities via classical selection and breeding, marker-aided selection and breeding, and genetic transformation. Information was collected by analysis of the literature, with emphasis on that published since 1995, and interviews with prominent scientists, breeders, and growers. Poplar research is well advanced, and literature is abundant. The report therefore primarily reflects advances in poplars, but data from other species, particularly other shortrotation hardwoods, are incorporated to fill gaps. An executive summary and recommendations for research, development, and technology transfer are provided immediately after the table of contents. The first major section of the report describes processes most likely to be used for conversion of poplar biomass to ethanol, the various physical and chemical properties of poplar feedstocks, and how such properties are expected to affect process efficiency. The need is stressed for improved understanding of the impact of change on both overall process and individual process step efficiencies. The second part documents advances in trait measurement instrumentation and methodology

  9. The impact of low-Z impurities on x-ray conversion efficiency from laser-produced plasmas of low-density gold foam targets

    SciTech Connect

    Dong, Yunsong; Department of Engineering Physics, Tsinghua University, Beijing 100084 ; Shang, Wanli; Yang, Jiamin; Zhang, Lu; Zhang, Wenhai; Li, Zhichao; Guo, Liang; Zhan, Xiayu; Du, Huabing; Deng, Bo; Pu, Yikang

    2013-12-15

    It is an important approach to improve the x-ray conversion efficiency of laser-ablated high-Z plasmas by using low initial density materials for various applications. However, unavoidable low-Z impurities in the manufacture process of low-density high-Z foam targets will depress this effect. A general easy-to-use analytical model based on simulations was developed to evaluate the quantitative impact of impurities within the gold foam target on laser to x-ray conversion efficiency. In addition, the x-ray conversion efficiencies of 1 g/cm{sup 3} gold foams with two different initial contents of impurities were experimentally investigated. Good agreements have been achieved between the model results and experiments.

  10. 76 FR 6488 - Notice of Submission of Proposed Information Collection to OMB Conversion of Efficiency Units to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-04

    ... URBAN DEVELOPMENT Notice of Submission of Proposed Information Collection to OMB Conversion of... and forms to permit the conversion of efficiencies to one-bedrooms provided it can be demonstrated that the conversion is warranted by local demands and results in the long- term financial and...

  11. High Photoelectric Conversion Efficiency of Metal Phthalocyanine/Fullerene Heterojunction Photovoltaic Device

    PubMed Central

    Lin, Chi-Feng; Zhang, Mi; Liu, Shun-Wei; Chiu, Tien-Lung; Lee, Jiun-Haw

    2011-01-01

    This paper introduces the fundamental physical characteristics of organic photovoltaic (OPV) devices. Photoelectric conversion efficiency is crucial to the evaluation of quality in OPV devices, and enhancing efficiency has been spurring on researchers to seek alternatives to this problem. In this paper, we focus on organic photovoltaic (OPV) devices and review several approaches to enhance the energy conversion efficiency of small molecular heterojunction OPV devices based on an optimal metal-phthalocyanine/fullerene (C60) planar heterojunction thin film structure. For the sake of discussion, these mechanisms have been divided into electrical and optical sections: (1) Electrical: Modification on electrodes or active regions to benefit carrier injection, charge transport and exciton dissociation; (2) Optical: Optional architectures or infilling to promote photon confinement and enhance absorption. PMID:21339999

  12. High conversion efficiency pumped-cavity second harmonic generation of a diode laser

    SciTech Connect

    Keicher, D.M.

    1994-01-01

    To investigate the feasibility of producing a compact, efficient blue laser source, pumped-cavity second harmonic generation of diode lasers was explored. It is desirable to have such lasers to increase optical disk storage density, for color displays and for under-the-sea green-blue optical signal transmission. Based on assumed cavity losses, a cavity was designed and numerical analysis predicted an overall conversion efficiency to the second harmonic wavelength of 76% from a 75 mW diode laser. The diode laser used in these experiments had a single longitudinal and a single transverse mode output at 860 nm. The best conversion efficiency obtained (26%) was less than optimum due to the 2.5% single-pass linear losses associated with the cavity. However, calculations based on these higher losses are in good agreement with the experimentally determined values. In additions, a factor of 1.65 increase in the second harmonic output power is anticipated by reducing the input mirror reflectivity to better impedance-match the cavity. With this relatively low second harmonic conversion, the power to light conversion is 7.8%.

  13. Improving solar cell efficiencies by up-conversion of sub-band-gap light

    NASA Astrophysics Data System (ADS)

    Trupke, T.; Green, M. A.; Würfel, P.

    2002-10-01

    A system for solar energy conversion using the up-conversion of sub-band-gap photons to increase the maximum efficiency of a single-junction conventional, bifacial solar cell is discussed. An up-converter is located behind a solar cell and absorbs transmitted sub-band-gap photons via sequential ground state absorption/excited state absorption processes in a three-level system. This generates an excited state in the up-converter from which photons are emitted which are subsequently absorbed in the solar cell and generate electron-hole pairs. The solar energy conversion efficiency of this system in the radiative limit is calculated for different cell geometries and different illumination conditions using a detailed balance model. It is shown that in contrast to an impurity photovoltaic solar cell the conditions of photon selectivity and of complete absorption of high-energy photons can be met simultaneously in this system by restricting the widths of the bands in the up-converter. The upper limit of the energy conversion efficiency of the system is found to be 63.2% for concentrated sunlight and 47.6% for nonconcentrated sunlight.

  14. Conversion Efficiency, Spectral And Mode Purities Of A Single Sideband Electro-Optic Modulator

    NASA Astrophysics Data System (ADS)

    Eng, R. S.; Parker, J. K.; Bunis, J. L.; Grimm, J. G.; Harris, N. W.; Wong, D. M.

    The measured single sideband conversion efficiency of a 10.6 μm bulk-type CdTe electro-optic modulator over the 14-18 GHz modulation frequency range is shown to be in close agreement with the coupled-mode and segmented modulator theories. The paper addresses the effects of the rotational orientations of segmented crystals and indirectly proves that a broadband multisection modulator is feasible; it further shows that a modulator with crystals in rotatable segmented circular waveguides is spectrally widely tunable. The effects of mechanical pressure and off-axis beam propagation on conver-sion, mode purity, and beam quality are also discussed.

  15. Conversion efficiency, spectral and mode purities of a single sideband electro-optic modulator

    NASA Astrophysics Data System (ADS)

    Eng, R. S.; Parker, J. K.; Bunis, J. L.; Grimm, J. G.; Harris, N. W.

    1989-06-01

    The measured single sideband conversion efficiency of a 10.6-micron bulk-type CdTe electrooptic modulator over the 14-18 GHz modulation frequency range is shown to be in close agreement with the coupled-mode and segmented modulator theories. The paper addresses the effects of the rotational orientations of segmented crystals and indirectly proves that a broadband multisection modulator is feasible. It is shown that a modulator with crystals in rotatable segmented circular waveguides is spectrally widely tunable. The effects of mechanical pressure and off-axis beam propagation on conversion, mode purity, and beam quality are also discussed.

  16. Fully efficient adiabatic frequency conversion of broadband Ti:sapphire oscillator pulses.

    PubMed

    Moses, Jeffrey; Suchowski, Haim; Kärtner, Franz X

    2012-05-01

    By adiabatic difference-frequency generation in an aperiodically poled nonlinear crystal-a nonlinear optical analog of rapid adiabatic passage in a two-level atomic system-we demonstrate the conversion of a 110 nm band from an octave-spanning Ti:sapphire oscillator to the infrared, spanning 1550 to 2450 nm, with near-100% internal conversion efficiency. The experiment proves the principle of complete Landau-Zener adiabatic transfer in nonlinear optical wave mixing. Our implementation is a practical approach to the seeding of high-energy ultrabroadband optical parametric chirped pulse amplifiers. PMID:22555747

  17. Efficient mode conversion in an optical nanoantenna mediated by quantum emitters

    NASA Astrophysics Data System (ADS)

    Straubel, J.; Filter, R.; Rockstuhl, C.; Słowik, K.

    2016-05-01

    Converting signals between different electromagnetic modes is an asset for future information technologies. In general, slightly asymmetric optical nanoantennas enable the coupling between bright and dark modes sustained by an optical nanoantenna. However, the conversion efficiency might be very low. Here, we show that the additional incorporation of a quantum emitter allows to tremendously enhance this efficiency. The enhanced local density of states cycles the quantum emitter between its upper and lower level at an extremely hight rate; hence converting the energy very efficient. The process is robust with respect to possible experimental tolerances and adds a new ingredient to be exploited while studying and applying coupling phenomena in optical nanosystems.

  18. Courageous Conversations: Achieving the Dream and the Importance of Student Success

    ERIC Educational Resources Information Center

    Change: The Magazine of Higher Learning, 2009

    2009-01-01

    Achieving the Dream: Community Colleges Count is a national initiative dedicated to the premise that community colleges should be as successful at student retention and graduation, particularly for students of color and low-income, as they are at enrollment. On campus, the initiative is focused on creating a culture of evidence, one in which data…

  19. Large-scale cauliflower-shaped hierarchical copper nanostructures for efficient photothermal conversion.

    PubMed

    Fan, Peixun; Wu, Hui; Zhong, Minlin; Zhang, Hongjun; Bai, Benfeng; Jin, Guofan

    2016-08-14

    Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ∼1 kW m(-2). The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area. PMID:27430171

  20. Efficient Energy Conversion of the 14 MeV Neutrons in DT Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Winterberg, F.

    2013-02-01

    In DT fusion 80 % of the energy released goes into 14 MeV neutrons, and only the remaining 20 % into charged particles. Unlike the charged particles, the uncharged neutrons cannot be confined by a magnetic field, and for this reason cannot be used for a direct conversion into electric energy. Instead, the neutrons have to be slowed down in some medium, heating this medium to a temperature of less than 103 K, with the heat removed from this medium to drive a turbo-generator. This conversion of nuclear into electric energy has a Carnot efficiency of about 30 %. For the 80 % of the energy released into neutrons, the efficiency is therefore no more than 24 %. While this low conversion efficiency cannot be overcome in magnetic confinement concepts, it can be overcome in inertial confinement concepts, by surrounding the inertial confinement fusion target with a sufficiently thick layer of liquid hydrogen and a thin outer layer of boron, to create a hot plasma fire ball. The hydrogen layer must be chosen just thick and dense enough to be heated by the neutrons to 100,000 K. The thusly generated, fully ionized, and rapidly expanding fire ball can drive a pulsed magnetohydrodynamic generator at an almost 100 % Carnot efficiency, or possibly be used to generate hydrocarbons.

  1. New method to increase the energy conversion efficiency of thermoacoustic engine

    NASA Astrophysics Data System (ADS)

    Kido, Aiko; Sakamoto, Shin-ichi; Taga, Kazusa; Watanabe, Yoshiaki

    2015-10-01

    Many researches have been reported to improve an energy conversion efficiency of thermoacoustic engine. Proposed improvement methods by our group were a phase adjuster (PA) and expanding phase adjuster (EPA) devices. They act as the amplifier and stabilizer of the system oscillation. However, there are some problems for these devices. Because of the solidified device and located in the thermoacoustic tube, it is difficult to tune and move them to the best setting position during system operation. Therefore, it is necessary to find more easy methods that produce the same amplifier and stabilizer effects of the PA and EPA. In this report, we propose the local heating method. Experiments are carried out using the loop-tube-type thermoacoustic system. Two electric heaters are set on the system, one is for the PM stack and the other is for the proposed heater HPA. The setting position of the HPA is easily changed, and then the HPA is moved to the various positions from the PM stack along the system. Resonant mode was changed depending on the setting position of HPA. As the result of the change of resonant mode, energy conversion efficiency is also changed. Especially the resonant mode is realized in the single wavelength mode, it is confirmed that, the energy conversion efficiency in substantially increased compare with the system without the HPA. These observed phenomena are similar to the behavior of EPA. Therefore, the presented method can be performed as an easier method to perform a high efficiency and stable oscillation.

  2. Conversion efficiency limits and bandgap designs for multi-junction solar cells with internal radiative efficiencies below unity.

    PubMed

    Zhu, Lin; Mochizuki, Toshimitsu; Yoshita, Masahiro; Chen, Shaoqiang; Kim, Changsu; Akiyama, Hidefumi; Kanemitsu, Yoshihiko

    2016-05-16

    We calculated the conversion-efficiency limit ηsc and the optimized subcell bandgap energies of 1 to 5 junction solar cells without and with intermediate reflectors under 1-sun AM1.5G and 1000-sun AM1.5D irradiations, particularly including the impact of internal radiative efficiency (ηint) below unity for realistic subcell materials on the basis of an extended detailed-balance theory. We found that the conversion-efficiency limit ηsc significantly drops when the geometric mean ηint* of all subcell ηint in the stack reduces from 1 to 0.1, and that ηsc degrades linearly to logηint* for ηint* below 0.1. For ηint*<0.1 differences in ηsc due to additional intermediate reflectors became very small if all subcells are optically thick for sun light. We obtained characteristic optimized bandgap energies, which reflect both ηint* decrease and AM1.5 spectral gaps. These results provide realistic efficiency targets and design principles. PMID:27409948

  3. A meta-analysis of responses of canopy photosynthetic conversion efficiency to environmental factors reveal major causes of yield gap

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Improving plant energy conversion efficiency is crucial for increasing food and bioenergy crop production and yields. This study statistically quantifies the effects of climate/weather factors and management techniques on energy conversion efficiency from 140 published studies and provides a quantit...

  4. An Oral Pressure Conversion Ratio as a Predictor of Vocal Efficiency.

    PubMed

    Titze, Ingo R; Maxfield, Lynn; Palaparthi, Anil

    2016-07-01

    Voice production is an inefficient process in terms of energy expended versus acoustic energy produced. A traditional efficiency measure, glottal efficiency, relates acoustic power radiated from the mouth to aerodynamic power produced in the trachea. This efficiency ranges between 0.0001% and 1.0%. It involves lung pressure and hence would appear to be a useful effort measure for a given acoustic output. Difficulty in the combined measurement of lung pressure and tracheal airflow, however, has impeded clinical application of glottal efficiency. This article uses the large data base from Schutte (1980) and a few new measurements to validate a pressure conversion ratio (PCR) as a substitute for glottal efficiency. PCR has the potential for wide application because of low cost and ease of use in clinics and vocal studios. PMID:26164123

  5. Efficiency enhancement of top-emitting organic light-emitting diodes using conversion dyes

    NASA Astrophysics Data System (ADS)

    Schwab, Tobias; Thomschke, Michael; Hofmann, Simone; Furno, Mauro; Leo, Karl; Lüssem, Björn

    2011-10-01

    We report recent results on top-emitting organic light-emitting diodes (OLEDs) using color conversion layers (CCLs) embedded into the electron transport layer of the OLED structure. The method of color conversion provides the possibility to generate a color stable emission with operating lifetime. Due to a constant ratio between absorbed blue emission and converter emission, the spectral shape remains for all time. This guarantees constant color coordinates of the OLED, which is essential for lighting applications. It is shown that OLEDs using conversion layers reach external quantum efficiencies (EQE) which can be higher than the corresponding blue top-emitting OLED. The used conversion layer thickness is below 100 nm, reaching Commission Internationale de l'Éclairage (CIE) coordinates of (0.23; 0.27) close to the Planckian locus at a maximum EQE of 3.16% using a blue fluorescent emitter system. Furthermore, we show that the excitation mechanism of the conversion layer is caused by absorption and no parasitic electrical excitation is taking place. Investigations on the emission color over the lifetime show color-stability over a period of up to 2200 h.

  6. Efficient and high speed depth-based 2D to 3D video conversion

    NASA Astrophysics Data System (ADS)

    Somaiya, Amisha Himanshu; Kulkarni, Ramesh K.

    2013-09-01

    Stereoscopic video is the new era in video viewing and has wide applications such as medicine, satellite imaging and 3D Television. Such stereo content can be generated directly using S3D cameras. However, this approach requires expensive setup and hence converting monoscopic content to S3D becomes a viable approach. This paper proposes a depth-based algorithm for monoscopic to stereoscopic video conversion by using the y axis co-ordinates of the bottom-most pixels of foreground objects. This code can be used for arbitrary videos without prior database training. It does not face the limitations of single monocular depth cues nor does it combine depth cues, thus consuming less processing time without affecting the efficiency of the 3D video output. The algorithm, though not comparable to real-time, is faster than the other available 2D to 3D video conversion techniques in the average ratio of 1:8 to 1:20, essentially qualifying as high-speed. It is an automatic conversion scheme, hence directly gives the 3D video output without human intervention and with the above mentioned features becomes an ideal choice for efficient monoscopic to stereoscopic video conversion. [Figure not available: see fulltext.

  7. The effect of converter efficiency on DEAP-based energy conversion: an overview and optimization method

    NASA Astrophysics Data System (ADS)

    van Kessel, Rick; Wattez, Ambroise; Bauer, Pavol

    2014-03-01

    This work presents an integral approach to the power electronic challenges that are faced in DEAP-based energy conversion, such as wide converter operating ranges and high peak-to-average ratios. It is shown that for small strain cycles, the losses in the Power Electronic Converter (PEC) due to the cyclic charging and discharging are dominant. The efficiency profile of a realistic, high-voltage modular PEC was measured and fed into an optimization algorithm. The current amplitude, phase and shape are optimized, and different cycle types are compared. With optimization results for a wide strain range, it is demonstrated that with properly adapted harvesting cycles, the overall conversion efficiency is significantly improved, especially for small strain cycles.

  8. The effects of prey species on food conversion efficiency and growth of an insectivorous lizard.

    PubMed

    Rich, C Nelson; Talent, Larry G

    2008-05-01

    Little is known about the effects of different prey species on lizard growth. We conducted a 6-week study to determine the relative effects of prey species on growth parameters of hatchling western fence lizards, Sceloporus occidentalis. Lizards were fed house cricket nymphs, Acheta domesticus, or mealworm larvae, Tenebrio molitor. The effects of prey species on growth were determined by measuring prey consumption, gross conversion efficiency of food [gain in mass (g)/food consumed (g)], gain in mass, and gain in snout-vent length. Lizards grew well on both the prey species. However, lizards that fed on crickets consumed a significantly higher percentage of their body mass per day than those fed mealworms. Nevertheless, lizards that consumed mealworms ingested significantly more metabolizable energy, had significantly higher food conversion efficiencies, significantly higher daily gains in mass, and significantly greater total growth in mass than lizards that fed on crickets. PMID:19360616

  9. Efficient photovoltaic conversion of graphene-carbon nanotube hybrid films grown from solid precursors

    NASA Astrophysics Data System (ADS)

    Gan, Xin; Lv, Ruitao; Bai, Junfei; Zhang, Zexia; Wei, Jinquan; Huang, Zheng-Hong; Zhu, Hongwei; Kang, Feiyu; Terrones, Mauricio

    2015-09-01

    Large-area (e.g. centimeter size) graphene sheets are usually synthesized via pyrolysis of gaseous carbon precursors (e.g. methane) on metal substrates like Cu using chemical vapor deposition (CVD), but the presence of grain boundaries and the residual polymers during transfer deteriorates significantly the properties of the CVD graphene. If carbon nanotubes (CNTs) can be covalently bonded to graphene, the hybrid system could possess excellent electrical conductivity, transparency and mechanical strength. In this work, conducting and transparent CNT-graphene hybrid films were synthesized by a facile solid precursor pyrolysis method. Furthermore, the synthesized CNT-graphene hybrid films display enhanced photovoltaic conversion efficiency when compared to devices based on CNT membranes or graphene sheets. Upon chemical doping, the graphene-CNT/Si solar cells reveal power conversion efficiencies up to 8.50%.

  10. 8.5 W VECSEL output at 1270 nm with conversion efficiency of 59%.

    PubMed

    Keller, S T; Sirbu, A; Iakovlev, V; Caliman, A; Mereuta, A; Kapon, E

    2015-06-29

    We report on 1270 nm vertical-external-cavity surface-emitting lasers (VECSELs) with up to 59% conversion efficiency and maximum output power of 8.5 W (pump limited), at 5°C heat sink temperature. These VECSELs comprised wafer-fused gain mirrors in the flip-chip (thin-disk) heat dissipation scheme. The reflected pump light from the gain mirror surface was found to depend considerably on temperature and pump power. PMID:26191752

  11. Effects of scattering and absorbing medium in the fluorescence conversion efficiency of physical tissue models

    NASA Astrophysics Data System (ADS)

    Anand, Suresh; Sujatha, N.

    2015-03-01

    Auto-fluorescence spectroscopy based on spectral line shape and intensity has been in use as a promising technique for detecting varying degrees of tissue malignancy. Tissue is a turbid medium with multi-layered structure constituting of different fluorophores, absorbers and scattering molecules. Tumor progression in tissues is ac- companied by varying degrees of biochemical and morphological changes. These include changes in nuclear size and density, epithelial thickness and increase in the hemoglobin (Hb) concentration associated with changes in metabolic activity. These variations in overall tissue scattering and absorption properties in turn modulate the fluorescence spectrum emitted and derived from tissues. Estimation of fluorescence conversion efficiency in the turbid tissue needs to take into account these effects of absorption and scattering in order to be evolved as a parameter for tissue discrimination. In this study, we set to investigate the factors affecting tissue fluorescence conversion efficiency by making use of physical models of the tissue. Liquid tissue models were prepared with different concentrations of absorbing and scattering media to simulate biological tissues of various degrees of malignancy. The results indicate that emitted fluorescence from the tissue model is subjected to variations by multiple scattering events and absorption. The fluorescence conversion efficiency of the models were derived and correlated to the experimental results with possible diagnostic significance.

  12. Large-scale cauliflower-shaped hierarchical copper nanostructures for efficient photothermal conversion

    NASA Astrophysics Data System (ADS)

    Fan, Peixun; Wu, Hui; Zhong, Minlin; Zhang, Hongjun; Bai, Benfeng; Jin, Guofan

    2016-07-01

    Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ~1 kW m-2. The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area.Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent

  13. Absorption spectra and sunlight conversion efficiency in fullerene bonded supramolecules on nanostructured ZnO

    NASA Astrophysics Data System (ADS)

    Zakhidov, Erkin; Kokhkharov, Abdumutallib; Kuvondikov, Vakhobjon; Nematov, Sherzod; Nusretov, Rafael

    2015-10-01

    The efficiency of solar radiation conversion in a model system of artificial photosynthesis, the porphyrin-fullerene assembly, is analyzed. A study of the optical absorption spectra of the porphyrin and the fullerene molecules, as well as their assembly in organic solutions, made it possible to estimate the energy efficiency of the conversion. Numerical values of the energy efficiency, defined as the fraction of the light quantum energy converted to the chemical potential of separated charges, are calculated for low- and high-concentration solutions of such a supramolecular system. The possibility of the efficient utilization of long-wavelength solar radiation in the high-concentration porphyrin-fullerene assembly solution in toluene and benzene is shown. In the photovoltaic system consisting of such a supramolecular active element, a thin ZnO film with a nanostructured surface may be introduced as a secondary acceptor of electrons from fullerene molecules. An enhancement of the transformation of separated charges of the porphyrin-fullerene assembly into electrical current by means of the ZnO film deposited on the surface of the anode electrode in such a heterogenic photovoltaic unit is proposed.

  14. High-Efficiency Photovoltaic Energy Conversion using Surface Acoustic Waves in Piezoelectric Semiconductors

    NASA Astrophysics Data System (ADS)

    Yakovenko, Victor

    2010-03-01

    We propose a radically new design for photovoltaic energy conversion using surface acoustic waves (SAWs) in piezoelectric semiconductors. The periodically modulated electric field from SAW spatially separates photogenerated electrons and holes to the maxima and minima of SAW, thus preventing their recombination. The segregated electrons and holes are transported by the moving SAW to the collecting electrodes of two types, which produce dc electric output. Recent experiments [1] using SAWs in GaAs have demonstrated the photon to current conversion efficiency of 85%. These experiments were designed for photon counting, but we propose to adapt these techniques for highly efficient photovoltaic energy conversion. The advantages are that the electron-hole segregation takes place in the whole volume where SAW is present, and the electrons and holes are transported in the organized, collective manner at high speed, as opposed to random diffusion in conventional devices.[4pt] [1] S. J. Jiao, P. D. Batista, K. Biermann, R. Hey, and P. V. Santos, J. Appl. Phys. 106, 053708 (2009).

  15. Characterization and modeling of microstructured chalcogenide fibers for efficient mid-infrared wavelength conversion.

    PubMed

    Xing, Sida; Grassani, Davide; Kharitonov, Svyatoslav; Billat, Adrien; Brès, Camille-Sophie

    2016-05-01

    We experimentally demonstrate wavelength conversion in the 2 µm region by four-wave mixing in an AsSe and a GeAsSe chalcogenide photonic crystal fibers. A maximum conversion efficiency of -25.4 dB is measured for 112 mW of coupled continuous wave pump in a 27 cm long fiber. We estimate the dispersion parameters and the nonlinear refractive indexes of the chalcogenide PCFs, establishing a good agreement with the values expected from simulations. The different fiber geometries and glass compositions are compared in terms of performance, showing that GeAsSe is a more suited candidate for nonlinear optics at 2 µm. Building from the fitted parameters we then propose a new tapered GeAsSe PCF geometry to tailor the waveguide dispersion and lower the zero dispersion wavelength (ZDW) closer to the 2 µm pump wavelength. Numerical simulations shows that the new design allows both an increased conversion efficiency and bandwidth, and the generation of idler waves further in the mid-IR regions, by tuning the pump wavelength in the vicinity of the fiber ZDW. PMID:27137588

  16. Linear mode conversion of Langmuir/z-mode waves to radiation: Scalings of conversion efficiencies and propagation angles with temperature and magnetic field orientation

    SciTech Connect

    Schleyer, F.; Cairns, Iver H.; Kim, E.-H.

    2013-03-15

    Linear mode conversion (LMC) is the linear transfer of energy from one wave mode to another in an inhomogeneous plasma. It is relevant to laboratory plasmas and multiple solar system radio emissions, such as continuum radiation from planetary magnetospheres and type II and III radio bursts from the solar corona and solar wind. This paper simulates LMC of waves defined by warm, magnetized fluid theory, specifically the conversion of Langmuir/z-mode waves to electromagnetic (EM) radiation. The primary focus is the calculation of the energy and power conversion efficiencies for LMC as functions of the angle of incidence {theta} of the Langmuir/z-mode wave, temperature {beta}=T{sub e}/m{sub e}c{sup 2}, adiabatic index {gamma}, and orientation angle {phi} between the ambient density gradient {nabla}N{sub 0} and ambient magnetic field B{sub 0} in a warm, unmagnetized plasma. The ratio of these efficiencies is found to agree well as a function of {theta}, {gamma}, and {beta} with an analytical relation that depends on the group speeds of the Langmuir/z and EM wave modes. The results demonstrate that the energy conversion efficiency {epsilon} is strongly dependent on {gamma}{beta}, {phi} and {theta}, with {epsilon}{proportional_to}({gamma}{beta}){sup 1/2} and {theta}{proportional_to}({gamma}{beta}){sup 1/2}. The power conversion efficiency {epsilon}{sub p}, on the other hand, is independent of {gamma}{beta} but does vary significantly with {theta} and {phi}. The efficiencies are shown to be maximum for approximately perpendicular density gradients ({phi} Almost-Equal-To 90 Degree-Sign ) and minimal for parallel orientation ({phi}=0 Degree-Sign ) and both the energy and power conversion efficiencies peak at the same {theta}.

  17. Dual-Layer Nanostructured Flexible Thin-Film Amorphous Silicon Solar Cells with Enhanced Light Harvesting and Photoelectric Conversion Efficiency.

    PubMed

    Lin, Yinyue; Xu, Zhen; Yu, Dongliang; Lu, Linfeng; Yin, Min; Tavakoli, Mohammad Mahdi; Chen, Xiaoyuan; Hao, Yuying; Fan, Zhiyong; Cui, Yanxia; Li, Dongdong

    2016-05-01

    Three-dimensional (3-D) structures have triggered tremendous interest for thin-film solar cells since they can dramatically reduce the material usage and incident light reflection. However, the high aspect ratio feature of some 3-D structures leads to deterioration of internal electric field and carrier collection capability, which reduces device power conversion efficiency (PCE). Here, we report high performance flexible thin-film amorphous silicon solar cells with a unique and effective light trapping scheme. In this device structure, a polymer nanopillar membrane is attached on top of a device, which benefits broadband and omnidirectional performances, and a 3-D nanostructure with shallow dent arrays underneath serves as a back reflector on flexible titanium (Ti) foil resulting in an increased optical path length by exciting hybrid optical modes. The efficient light management results in 42.7% and 41.7% remarkable improvements of short-circuit current density and overall efficiency, respectively. Meanwhile, an excellent flexibility has been achieved as PCE remains 97.6% of the initial efficiency even after 10 000 bending cycles. This unique device structure can also be duplicated for other flexible photovoltaic devices based on different active materials such as CdTe, Cu(In,Ga)Se2 (CIGS), organohalide lead perovskites, and so forth. PMID:27052357

  18. A new strategy for efficient solar energy conversion: Parallel-processing with surface plasmons

    NASA Technical Reports Server (NTRS)

    Anderson, L. M.

    1982-01-01

    This paper introduces an advanced concept for direct conversion of sunlight to electricity, which aims at high efficiency by tailoring the conversion process to separate energy bands within the broad solar spectrum. The objective is to obtain a high level of spectrum-splitting without sequential losses or unique materials for each frequency band. In this concept, sunlight excites a spectrum of surface plasma waves which are processed in parallel on the same metal film. The surface plasmons transport energy to an array of metal-barrier-semiconductor diodes, where energy is extracted by inelastic tunneling. Diodes are tuned to different frequency bands by selecting the operating voltage and geometry, but all diodes share the same materials.

  19. Efficient mode conversion in an optical nanoantenna mediated by quantum emitters.

    PubMed

    Straubel, J; Filter, R; Rockstuhl, C; Słowik, K

    2016-05-15

    Converting signals at low intensities between different electromagnetic modes is an asset for future information technologies. In general, slightly asymmetric optical nanoantennas enable the coupling between bright and dark modes that they sustain. However, the conversion efficiency might be very low. Here, we show that the additional incorporation of a quantum emitter allows us to tremendously enhance this efficiency. The enhanced local density of states cycles the quantum emitter between its upper and lower level at an extremely high rate, hence converting the energy very efficiently. The process is robust with respect to possible experimental tolerances, and adds a new ingredient to be exploited while studying and applying coupling phenomena in optical nanosystems. PMID:27176986

  20. Optimizing conversion efficiency and reducing ion energy in a laser-produced Gd plasma

    SciTech Connect

    Cummins, Thomas; Li Bowen; O'Gorman, Colm; Dunne, Padraig; Sokell, Emma; O'Sullivan, Gerry; Otsuka, Takamitsu; Yugami, Noboru; Higashiguchi, Takeshi; Jiang Weihua; Endo, Akira

    2012-02-06

    We have demonstrated an efficient extreme ultraviolet (EUV) source at 6.7 nm by irradiating Gd targets with 0.8 and 1.06 {mu}m laser pulses of 140 fs to 10 ns duration. Maximum conversion efficiency of 0.4% was observed within a 0.6% bandwidth. A Faraday cup observed ion yield and time of flight signals for ions from plasmas generated by each laser. Ion kinetic energy was lower for shorter pulse durations, which yielded higher electron temperatures required for efficient EUV emission, due to higher laser intensity. Picosecond laser pulses were found to be the best suited to 6.7 nm EUV source generation.

  1. The Upper Bound on Solar Power Conversion Efficiency Through Photonic Engineering

    NASA Astrophysics Data System (ADS)

    Xu, Yunlu; Munday, Jeremy

    The power conversion efficiency is a key parameter by which different photovoltaic devices are compared. The maximum value can be calculated under steady-state conditions where the photon flux absorbed by the device equals the outgoing flux of particles (also known as the principle of detailed balance). The photonic engineering of a solar cell offers a new alternative for boosting efficiency. We show that, for an ideally photonic engineered solar cell, its efficiency is subject to an upper bound dictated by a generalized form of detailed balance equation where nano-concentration is taken into account. Results under realistic operating conditions and recent experimental studies will also be discussed. Authors acknowledge the University of Maryland for startup funds to initiate this project and support by the National Science Foundation under Grant CBET-1335857.

  2. Electromagnetic Spectrum Analysis and Its Influence on the Photoelectric Conversion Efficiency of Solar Cells.

    PubMed

    Hu, Kexiang; Ding, Enjie; Wangyang, Peihua; Wang, Qingkang

    2016-06-01

    The electromagnetic spectrum and the photoelectric conversion efficiency of the silicon hexagonal nanoconical hole (SiHNH) arrays based solar cells is systematically analyzed according to Rigorous Coupled Wave Analysis (RCWA) and Modal Transmission Line (MTL) theory. An ultimate efficiency of the optimized SiHNH arrays based solar cell is up to 31.92% in consideration of the absorption spectrum, 4.52% higher than that of silicon hexagonal nanoconical frustum (SiHNF) arrays. The absorption enhancement of the SiHNH arrays is due to its lower reflectance and more supported guided-mode resonances, and the enhanced ultimate efficiency is insensitive to bottom diameter (D(bot)) of nanoconical hole and the incident angle. The result provides an additional guideline for the nanostructure surface texturing fabrication design for photovoltaic applications. PMID:27427668

  3. Efficiency and stability of a phosphor-conversion white light source using a blue laser diode

    NASA Astrophysics Data System (ADS)

    Ledru, G.; Catalano, C.; Dupuis, P.; Zissis, G.

    2014-10-01

    A white light source using direct phosphor-conversion excited by a blue laser diode is presented. In this preliminary study we have investigated the influence of phosphor's thickness and operating current of the laser diode over the (x, y) chromaticity coordinates, Correlated Color Temperature (CCT) and Color Rendering Index (CRI). The best values found were 4000 K and 94. A 40 lm/W luminous efficacy was achieved together with a CRI close to 90 for an operating current of 0.8 A. Those values, to the best of our knowledge, were not previously reported in the literature.

  4. Estimates of achievable potential for electricity efficiency improvements in U.S. residences

    SciTech Connect

    Brown, Richard

    1993-05-01

    This paper investigates the potential for public policies to achieve electricity efficiency improvements in US residences. This estimate of achievable potential builds upon a database of energy-efficient technologies developed for a previous study estimating the technical potential for electricity savings. The savings potential and cost for each efficiency measure in the database is modified to reflect the expected results of policies implemented between 1990 and 2010. Factors included in these modifications are: the market penetration of efficiency measures, the costs of administering policies, and adjustments to the technical potential measures to reflect the actual energy savings and cost experienced in the past. When all adjustment factors are considered, this study estimates that policies can achieve approximately 45% of the technical potential savings during the period from 1990 to 2010. Thus, policies can potentially avoid 18% of the annual frozen-efficiency baseline electricity consumption forecast for the year 2010. This study also investigates the uncertainty in best estimate of achievable potential by estimating two alternative scenarios -- a

  5. Enhanced solar cell conversion efficiency using birefringent liquid crystal polymer homeotropic films from reactive mesogens.

    PubMed

    Wu, Gwomei; Hsieh, Li-Hang; Chien, How-Wen

    2013-01-01

    Novel birefringent liquid crystal polymer homeotropic films have been coated on semiconductor solar cells to improve the effective incident sunlight angles. The liquid crystal polymer precursor, based on reactive mesogens, is fluidic and flows like liquid. It would distribute uniformly on the solar cell sample surface by any traditional coating technique. The birefringence for light, due to the liquid crystal retardation properties, manipulated the optical length and the deflection of incident light, thus allowed an increase in the energy conversion efficiency. The expensive sunlight tracking systems could be avoided. The processing parameters can be tuned such as different mesogen concentrations and plate speeds of spin-coating. The results showed that the solar cell conversion efficiency was improved from 14.56% to 14.85% at an incident sunlight angle of 15°. It was further improved from 13.40% to 13.81% when the angle was 30°. The interesting angular dependency on solar cell efficiency enhancement has been evaluated. PMID:24232577

  6. Enhanced Solar Cell Conversion Efficiency Using Birefringent Liquid Crystal Polymer Homeotropic Films from Reactive Mesogens

    PubMed Central

    Wu, Gwomei; Hsieh, Li-Hang; Chien, How-Wen

    2013-01-01

    Novel birefringent liquid crystal polymer homeotropic films have been coated on semiconductor solar cells to improve the effective incident sunlight angles. The liquid crystal polymer precursor, based on reactive mesogens, is fluidic and flows like liquid. It would distribute uniformly on the solar cell sample surface by any traditional coating technique. The birefringence for light, due to the liquid crystal retardation properties, manipulated the optical length and the deflection of incident light, thus allowed an increase in the energy conversion efficiency. The expensive sunlight tracking systems could be avoided. The processing parameters can be tuned such as different mesogen concentrations and plate speeds of spin-coating. The results showed that the solar cell conversion efficiency was improved from 14.56% to 14.85% at an incident sunlight angle of 15°. It was further improved from 13.40% to 13.81% when the angle was 30°. The interesting angular dependency on solar cell efficiency enhancement has been evaluated. PMID:24232577

  7. Improvement of power conversion efficiency in photovoltaic-assisted UHF rectifiers by non-silicide technique applied to photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Kotani, Koji

    2015-04-01

    Non-silicide PV cell structures were successfully applied to the photovoltaic (PV)-assisted UHF rectifier, which is one example realization of the “synergistic ambient energy harvesting” concept. Silicide blocking of PV cell area was experimentally verified to be effective for increasing photo-generated bias voltage, which resulted in the improved power conversion efficiency (PCE) of the rectifier by enhanced VTH compensation effect. Increase in both transparency of light and quantum efficiency of PV cells obtained by eliminating silicide layer affects the PCE improvement almost equally. 25.8% of PCE was achieved under the conditions of an RF input power of -20 dBm, a frequency of 920 MHz, an output load of 47 kΩ, and a typical indoor light irradiance level of 1 W/m2. In addition, when the non-silicide PV cell technique was applied to the voltage-boosted PV-cell structures, 32.1% peak PCE was achieved at 10 W/m2.

  8. K-alpha conversion efficiency measurments for x-ray scattering in inertial confinement fusion plasmas

    SciTech Connect

    Kritcher, A L; Neumayer, P; Urry, M K; Robey, H; Niemann, C; Landen, O L; Morse, E; Glenzer, S H

    2006-11-21

    The conversion efficiency of ultra short-pulse laser radiation to K-{alpha} x-rays has been measured for various chlorine-containing targets to be used as x-ray scattering probes of dense plasmas. The spectral and temporal properties of these sources will allow spectrally-resolved x-ray scattering probing with picosecond temporal resolution required for measuring the plasma conditions in inertial confinement fusion experiments. Simulations of x-ray scattering spectra from these plasmas show that fuel capsule density, capsule ablator density, and shock timing information may be inferred.

  9. Analysis of the acoustic conversion efficiency for infrasound from atmospheric entry of NEO`s

    SciTech Connect

    Whitaker, R.W.; ReVelle, D.O.

    1996-02-01

    ReVelle (1995) has recently presented a summary of available infrasonic signals from near earth objects (NEO`s) that entered the earth`s atmosphere between 1960-1980. We will analyze these signals using a formalism developed by Cox (1958) to calculate the energy of explosive sources in the atmosphere. For each source we will calculate the acoustic conversion efficiency for each source, i.e., the fraction of the original source energy that is available to couple into an acoustic wave. Based on results in Cox with conventional explosions, this quantity is expected to depend weakly on the range from the source. Since this quantity is difficult to estimate using fundamental blast wave theories, we instead use well-known, and independently calibrated, semi-empirical source energy-wave period (at maximum amplitude) scaling relations developed in the 1960-1975 period by the U.S. Air Force to determine the source energy, E{sub s}, from observations. Using E{sub s} and range to the source along with various observed signal and atmospheric properties, the efficiency can be computed, similar calculations have been done for other relevant atmospheric phenomena for low altitude sources. For example, thunder observations at relatively close range have been used by Few and co-workers to determine an acoustic conversion efficiency of about 0.4%. The only previous estimation for meteors was made by Astapovich (1946) who determined the acoustic efficiency to be less than 0.01%. By computing this efficiency factor we hope to predict the expected detection rate of large NEO`s for the proposed CTBT global scale infrasonic array systems, and to establish the rate of false alarms due to natural atmospheric explosions.

  10. Suppression of Tla1 gene expression for improved solar conversion efficiency and photosynthetic productivity in plants and algae

    DOEpatents

    Melis, Anastasios; Mitra, Mautusi

    2010-06-29

    The invention provides method and compositions to minimize the chlorophyll antenna size of photosynthesis by decreasing TLA1 gene expression, thereby improving solar conversion efficiencies and photosynthetic productivity in plants, e.g., green microalgae, under bright sunlight conditions.

  11. Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1.

    PubMed

    Wang, Qian; Hisatomi, Takashi; Jia, Qingxin; Tokudome, Hiromasa; Zhong, Miao; Wang, Chizhong; Pan, Zhenhua; Takata, Tsuyoshi; Nakabayashi, Mamiko; Shibata, Naoya; Li, Yanbo; Sharp, Ian D; Kudo, Akihiko; Yamada, Taro; Domen, Kazunari

    2016-06-01

    Photocatalytic water splitting using particulate semiconductors is a potentially scalable and economically feasible technology for converting solar energy into hydrogen. Z-scheme systems based on two-step photoexcitation of a hydrogen evolution photocatalyst (HEP) and an oxygen evolution photocatalyst (OEP) are suited to harvesting of sunlight because semiconductors with either water reduction or oxidation activity can be applied to the water splitting reaction. However, it is challenging to achieve efficient transfer of electrons between HEP and OEP particles. Here, we present photocatalyst sheets based on La- and Rh-codoped SrTiO3 (SrTiO3:La, Rh; ref. ) and Mo-doped BiVO4 (BiVO4:Mo) powders embedded into a gold (Au) layer. Enhancement of the electron relay by annealing and suppression of undesirable reactions through surface modification allow pure water (pH 6.8) splitting with a solar-to-hydrogen energy conversion efficiency of 1.1% and an apparent quantum yield of over 30% at 419 nm. The photocatalyst sheet design enables efficient and scalable water splitting using particulate semiconductors. PMID:26950596

  12. Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1%

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Hisatomi, Takashi; Jia, Qingxin; Tokudome, Hiromasa; Zhong, Miao; Wang, Chizhong; Pan, Zhenhua; Takata, Tsuyoshi; Nakabayashi, Mamiko; Shibata, Naoya; Li, Yanbo; Sharp, Ian D.; Kudo, Akihiko; Yamada, Taro; Domen, Kazunari

    2016-06-01

    Photocatalytic water splitting using particulate semiconductors is a potentially scalable and economically feasible technology for converting solar energy into hydrogen. Z-scheme systems based on two-step photoexcitation of a hydrogen evolution photocatalyst (HEP) and an oxygen evolution photocatalyst (OEP) are suited to harvesting of sunlight because semiconductors with either water reduction or oxidation activity can be applied to the water splitting reaction. However, it is challenging to achieve efficient transfer of electrons between HEP and OEP particles. Here, we present photocatalyst sheets based on La- and Rh-codoped SrTiO3 (SrTiO3:La, Rh; ref. ) and Mo-doped BiVO4 (BiVO4:Mo) powders embedded into a gold (Au) layer. Enhancement of the electron relay by annealing and suppression of undesirable reactions through surface modification allow pure water (pH 6.8) splitting with a solar-to-hydrogen energy conversion efficiency of 1.1% and an apparent quantum yield of over 30% at 419 nm. The photocatalyst sheet design enables efficient and scalable water splitting using particulate semiconductors.

  13. Efficient near-infrared up-conversion photoluminescence in carbon nanotubes

    PubMed Central

    Akizuki, Naoto; Aota, Shun; Mouri, Shinichiro; Matsuda, Kazunari; Miyauchi, Yuhei

    2015-01-01

    Photoluminescence phenomena normally obey Stokes' law of luminescence according to which the emitted photon energy is typically lower than its excitation counterparts. Here we show that carbon nanotubes break this rule under one-photon excitation conditions. We found that the carbon nanotubes exhibit efficient near-infrared photoluminescence upon photoexcitation even at an energy lying >100–200 meV below that of the emission at room temperature. This apparently anomalous phenomenon is attributed to efficient one-phonon-assisted up-conversion processes resulting from unique excited-state dynamics emerging in an individual carbon nanotube with accidentally or intentionally embedded localized states. These findings may open new doors for energy harvesting, optoelectronics and deep-tissue photoluminescence imaging in the near-infrared optical range. PMID:26568250

  14. Selective Conversion of CO2 to CO with High Efficiency using an Inexpensive Bismuth Based Electrocatalyst

    PubMed Central

    DiMeglio, John L.; Rosenthal, Joel

    2013-01-01

    The wide-scale implementation of solar and other renewable sources of electricity requires improved means for energy storage. An intriguing strategy in this regard is the reduction of CO2 to CO, which generates an energy rich commodity chemical that can be coupled to liquid fuel production. In this work, we report an inexpensive Bismuth Carbon Monoxide Evolving Catalyst (Bi-CMEC) that can be formed upon cathodic polarization of an inert glassy carbon electrode in acidic solutions containing Bi3+ ions. This catalyst can be used in conjunction with ionic liquids to effect the electrocatalytic conversion of CO2 to CO with appreciable current density at overpotentials below 0.2 V. Bi-CMEC is selective for production of CO, operating with a Faradaic efficiency of approximately 95%. When taken together these correspond to a high energy efficiency for CO production, on par with that which has historically only been observed using expensive silver and gold cathodes. PMID:23735115

  15. Development of a high-energy distributed energy source electromagnetic railgun with improved energy conversion efficiency

    SciTech Connect

    Tower, M.M.; Haight, C.H.

    1984-03-01

    Vought Corporation in cooperation with the Center for Electromechanics at the University of Texas (CEM-UT) has developed under sponsorship by the Defense Advanced Research Projects Agency (DARPA) and the Army Armament, Munitions, and Chemical Command (AMCCOM) a high-energy distributed energy source (DES) electromagnetic (EM) railgun accelerator. This paper discusses the development and current status of the DES railgun which has the design capability to launch projectile masses up to 60 grams to the 3-4 km/sec velocity regime with energy conversion efficiencies above 35 percent. These goals are being accomplished through utilization of scaled-energy CEM-UT railgun experiments for sequenced timing/staging and a full energy (575 kJ) design at Vought for high efficiency capability. The operational Vought single-pulse railgun forms the baseline for the full energy testing.

  16. Efficient near-infrared up-conversion photoluminescence in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Akizuki, Naoto; Aota, Shun; Mouri, Shinichiro; Matsuda, Kazunari; Miyauchi, Yuhei

    2015-11-01

    Photoluminescence phenomena normally obey Stokes' law of luminescence according to which the emitted photon energy is typically lower than its excitation counterparts. Here we show that carbon nanotubes break this rule under one-photon excitation conditions. We found that the carbon nanotubes exhibit efficient near-infrared photoluminescence upon photoexcitation even at an energy lying >100-200 meV below that of the emission at room temperature. This apparently anomalous phenomenon is attributed to efficient one-phonon-assisted up-conversion processes resulting from unique excited-state dynamics emerging in an individual carbon nanotube with accidentally or intentionally embedded localized states. These findings may open new doors for energy harvesting, optoelectronics and deep-tissue photoluminescence imaging in the near-infrared optical range.

  17. The atomistic origin of interface confinement and enhanced conversion efficiency in Si nanowire solar cells.

    PubMed

    He, Yan; Quan, Jun; Ouyang, Gang

    2016-03-14

    The photoelectric properties of Si nanowires (SiNWs) under interface confinement are investigated based on the atomic-bond-relaxation consideration and the detailed balance principle. An analytical model is developed to elucidate the interface confinement and power conversion efficiency (PCE). It is found that the band curvature and surface barrier height decrease with decreasing size. The interface recombination rate and PCE can be determined by the size, shell thickness and local interface conditions. Our theoretical results show evident improvement in the PCE of SiNWs under interface confinement compared to that of a bare nanowire, highlighting the feasibility of the epitaxial layer as a booster for highly efficient SiNW solar cells. PMID:26883245

  18. Anatase TiO2 nanorod-decoration for highly efficient photoenergy conversion

    NASA Astrophysics Data System (ADS)

    Kim, Dong Hoe; Seong, Won Mo; Park, Ik Jae; Yoo, Eun-Sang; Shin, Seong Sik; Kim, Ju Seong; Jung, Hyun Suk; Lee, Sangwook; Hong, Kug Sun

    2013-11-01

    In recent studies of inorganic materials for energy applications, surface modification processes have been shown to be among the most effective methods to enhance the performance of devices. Here, we demonstrate a facile nano-decoration method which is generally applicable to anatase TiO2 nanostructures, as well as a nano-decorated hierarchical TiO2 nanostructure which improves the energy conversion efficiency of a dye-sensitized solar cell (DSSC). Using a facile sol-gel method, 0-D, 1-D, and 2-D type anatase TiO2 nanostructures were decorated with 200 nm long anatase TiO2 nanorods to create various hierarchical nanostructures. A structural analysis reveals that the branched nanorod has a highly crystalline anatase phase with anisotropic growth in the [001] longitudinal direction. When one of the hierarchical structures, a chestnut bur-like nanostructure, was employed in a dye-sensitized solar cell as a scattering layer, offering increased dye-loading properties, preserving a sufficient level of light-scattering ability and preserving superior charge transport and recombination properties as well, the energy conversion efficiency of the cell improved by 19% (from 7.16% to 9.09%) compared to a cell with a 0-D TiO2 sphere as a scattering layer. This generally applicable anatase nanorod-decorating method offers potential applications in various energy-conversion applications, especially in DSSCs, quantum-dot solar cells, photoelectrochemical water-splitting devices, photocatalysis, and lithium ion batteries.In recent studies of inorganic materials for energy applications, surface modification processes have been shown to be among the most effective methods to enhance the performance of devices. Here, we demonstrate a facile nano-decoration method which is generally applicable to anatase TiO2 nanostructures, as well as a nano-decorated hierarchical TiO2 nanostructure which improves the energy conversion efficiency of a dye-sensitized solar cell (DSSC). Using a facile

  19. Pilot-scale bioelectrochemical system for efficient conversion of 4-chloronitrobenzene.

    PubMed

    Yuan, Yuan; You, Shi-Jie; Zhang, Jin-Na; Gong, Xiao-Bo; Wang, Xiu-Heng; Ren, Nan-Qi

    2015-01-01

    4-Chloronitrobenzene (4-CNB) is one of the highly toxic contaminants that may lead to acute, chronic or persistent physiological toxicity to ecology and environment. Conventional methods for removing 4-CNB from aquatic environment may be problematic due to inefficiency, high cost and low sustainability. This study develops a pilot-scale bioelectrochemical system (BES, effective volume of 18 L) and examines its performance of bioelectrochemical transformation of 4-CNB to 4-chloroaniline (4-CAN) under continuous operation. The results demonstrate that the initial 4-CNB concentration in the influent and hydraulic retention time (HRT) has a significant impact on 4-CNB reduction and 4-CAN formation. Compared with the conventional anaerobic process in the absence of external power supplied, the 4-CNB conversion efficiency can be enhanced with power supplied due to microbial-mediated electron transfer at the negative cathode potential. At a voltage of 0.4 V and HRT of 48 h, the 4-CNB reduction and 4-CAN formation efficiency reached 99% and 94.1%, respectively. Based on a small external voltage applied, the pilot-scale BES is effective in the conversion of 4-CNB to 4-CAN, an intermediate that is of less toxicity and higher bioavailability for subsequent treatment. This study provides a new strategy and methods for eliminating 4-CNB, making wastewater treatment more economical and more sustainable. PMID:25650667

  20. [Research practices of conversion efficiency of resources utilization model of castoff from Chinese material medica industrialization].

    PubMed

    Duan, Jin-Ao; Su, Shu-Lan; Guo, Sheng; Liu, Pei; Qian, Da-Wei; Jiang, Shu; Zhu, Hua-Xu; Tang, Yu-Ping; Wu, Qi-Nan

    2013-12-01

    The industrialization chains and their products, which were formed from the process of the production of medicinal materials-prepared drug in pieces and deep processed product of Chinese material medica (CMM) resources, have generated large benefits of social and economic. However, The large of herb-medicine castoff of "non-medicinal parts" and "rejected materials" produced inevitably during the process of Chinese medicinal resources produce and process, and the residues, waste water and waste gas were produced during the manufactured and deep processed product of CMM. These lead to the waste of resources and environmental pollution. Our previous researches had proposed the "three utilization strategies" and "three types of resources models" of herb-medicine castoff according to the different physicochemical property of resources constitutes, resources potential and utility value of herb-medicine castoff. This article focus on the conversion efficiency of resources model and analysis the ways, technologies, practices, and application in herb-medicine cast off of the conversion efficiency of resources model based on the recycling economy theory of resources and thoughts of resources chemistry of CMM. These data may be promote and resolve the key problems limited the industrialization of Chinese material medica for long time and promote the realization of herb-medicine castoff resources utilization. PMID:24791476

  1. Thermodynamic limits to the efficiency of solar energy conversion by quantum devices

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    The second law of thermodynamics imposes a strict limitation to the energy converted from direct solar radiation to useful work by a quantum device. This limitation requires that the amount of energy converted to useful work (energy in any form other than heat) can be no greater than the change in free energy of the radiation fields. Futhermore, in any real energy conversion device, not all of this available free energy in the radiation field can be converted to work because of basic limitations inherent in the device itself. A thermodynamic analysis of solar energy conversion by a completely general prototypical quantum device is presented. This device is completely described by two parameters, its operating temperature T sub R and the energy threshold of its absorption spectrum. An expression for the maximum thermodynamic efficiency of a quantum solar converter was derived in terms of these two parameters and the incident radiation spectrum. Efficiency curves for assumed solar spectral irradiance corresponding to air mass zero and air mass 1.5 are presented.

  2. Triple-junction amorphous silicon alloy solar cell with 14.6{percent} initial and 13.0{percent} stable conversion efficiencies

    SciTech Connect

    Yang, J.; Banerjee, A.; Guha, S.

    1997-06-01

    We have achieved 14.6{percent} initial and 13.0{percent} stable conversion efficiencies using an amorphous silicon-based alloy in a spectrum-splitting, triple-junction structure. These efficiencies have been confirmed independently by the National Renewable Energy Laboratory. Key factors leading to this major advance include improvements made in the low band-gap amorphous silicon{endash}germanium alloy cell, the pn tunnel junction between the component cells, and the top conducting oxide. {copyright} {ital 1997 American Institute of Physics.}

  3. Numerical model of the temperature dependence of the up-conversion efficiency of fluoride crystals codoped with ytterbium and thulium

    NASA Astrophysics Data System (ADS)

    Rapaport, A.; Milliez, J.; Bass, M.; Cassanho, A.; Jenssen, H.

    2005-06-01

    We review the role of temperature on the up-conversion efficiency of materials that are good candidates to be used as the three primary-color emitters in optically written displays. A rate equation model is given for the blue emitting material that includes temperature-dependent coefficients for energy transfer and cross relaxation. Increased temperature leads to decreased up-conversion efficiency. The effect of pumping conditions on heating the emitting material is illustrated and explained. Steps to reduce the temperature rise when pumping up-conversion materials are described.

  4. Investigation on the influence of BBO thermal-induced phase mismatching in 266nm UV laser conversion efficiency

    NASA Astrophysics Data System (ADS)

    Yu, Kai; Jin, Guangyong; Yu, Miao; Huang, Zhulong; Zhai, Ruizhi; Wang, Lei

    2014-12-01

    266nm UV laser has a wide range of applications in many fields, such as laser medical treatment, laser processing, precision measure and other applications for the reason of its advantages in wavelength, small diffraction effects, high single-photon energy, and high resolution and so on. BBO crystals absorb parts of the fundamental laser energy and second harmonic laser energy are unavoidable, and thus the temperature raise, so that the existing crystal phase matching conditions change, resulting in phase mismatching in the high-power frequency doubling, greatly influence the 266nm UV laser conversion efficiency. To further study the effect of phase mismatching to conversion efficiency, and improve the conversion efficiency, output power and other output characteristics of 266nm laser, the article mainly describe from the following three aspects. Firstly, took the use of three-dimensional nonlinear crystal temperature distribution which is obtained, the process of BBO crystal thermal-induced phase mismatching is analyzed. Secondly, based on frequency doubling theory, the effects of the thermal-induced phase mismatching affected of conversion in crystals are analyzed. Combining with the phase mismatching of the three-dimensional distributions, the fourth harmonic conversion efficiency with thermal phase mismatching changes of BBO 266nm UV laser are simulated for the first time. Thirdly, by using MATLAB software, the effects of phase mismatching to conversion efficiency in crystal for different waist radius, 532nm laser power and the fundamental beam quality are simulated. The results indicate a good physical interpretation of reasons of high power laser frequency doubling system. It shows that the model established explains the reason of the reduction of conversion efficiency, output power and the beam quality excellently. All results make a leading sense to the research on the compensating of the phase mismatching and on the improvement of conversion efficiency.

  5. Theme--Achieving 2020. Goal 3: All Students Are Conversationally Literate in Agriculture, Food, Fiber, and Natural Resource Systems.

    ERIC Educational Resources Information Center

    Trexler, Cary, Ed.

    2000-01-01

    Nine theme articles focus on the need for students to be conversationally literate about agriculture, food, fiber, and natural resources systems. Discusses the definition of conversational literacy, the human and institutional resources needed, and exemplary models for promoting literacy. (JOW)

  6. Perovskite Solar Cells: Influence of Hole Transporting Materials on Power Conversion Efficiency.

    PubMed

    Ameen, Sadia; Rub, Malik Abdul; Kosa, Samia A; Alamry, Khalid A; Akhtar, M Shaheer; Shin, Hyung-Shik; Seo, Hyung-Kee; Asiri, Abdullah M; Nazeeruddin, Mohammad Khaja

    2016-01-01

    The recent advances in perovskite solar cells (PSCs) created a tsunami effect in the photovoltaic community. PSCs are newfangled high-performance photovoltaic devices with low cost that are solution processable for large-scale energy production. The power conversion efficiency (PCE) of such devices experienced an unprecedented increase from 3.8 % to a certified value exceeding 20 %, demonstrating exceptional properties of perovskites as solar cell materials. A key advancement in perovskite solar cells, compared with dye-sensitized solar cells, occurred with the replacement of liquid electrolytes with solid-state hole-transporting materials (HTMs) such as 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), which contributed to enhanced PCE values and improved the cell stability. Following improvements in the perovskite crystallinity to produce a smooth, uniform morphology, the selective and efficient extraction of positive and negative charges in the device dictated the PCE of PSCs. In this Review, we focus mainly on the HTMs responsible for hole transport and extraction in PSCs, which is one of the essential components for efficient devices. Here, we describe the current state-of-the-art in molecular engineering of hole-transporting materials that are used in PSCs and highlight the requisites for market-viability of this technology. Finally, we include an outlook on molecular engineering of new functional HTMs for high efficiency PSCs. PMID:26692567

  7. Efficiency improvement in the cantilever photothermal excitation method using a photothermal conversion layer.

    PubMed

    Inada, Natsumi; Asakawa, Hitoshi; Kobayashi, Taiki; Fukuma, Takeshi

    2016-01-01

    Photothermal excitation is a cantilever excitation method that enables stable and accurate operation for dynamic-mode AFM measurements. However, the low excitation efficiency of the method has often limited its application in practical studies. In this study, we propose a method for improving the photothermal excitation efficiency by coating cantilever backside surface near its fixed end with colloidal graphite as a photothermal conversion (PTC) layer. The excitation efficiency for a standard cantilever of PPP-NCHAuD with a spring constant of ≈40 N/m and a relatively stiff cantilever of AC55 with a spring constant of ≈140 N/m were improved by 6.1 times and 2.5 times, respectively, by coating with a PTC layer. We experimentally demonstrate high stability of the PTC layer in liquid by AFM imaging of a mica surface with atomic resolution in phosphate buffer saline solution for more than 2 h without any indication of possible contamination from the coating. The proposed method, using a PTC layer made of colloidal graphite, greatly enhances photothermal excitation efficiency even for a relatively stiff cantilever in liquid. PMID:27335733

  8. Efficiency improvement in the cantilever photothermal excitation method using a photothermal conversion layer

    PubMed Central

    Inada, Natsumi; Kobayashi, Taiki; Fukuma, Takeshi

    2016-01-01

    Summary Photothermal excitation is a cantilever excitation method that enables stable and accurate operation for dynamic-mode AFM measurements. However, the low excitation efficiency of the method has often limited its application in practical studies. In this study, we propose a method for improving the photothermal excitation efficiency by coating cantilever backside surface near its fixed end with colloidal graphite as a photothermal conversion (PTC) layer. The excitation efficiency for a standard cantilever of PPP-NCHAuD with a spring constant of ≈40 N/m and a relatively stiff cantilever of AC55 with a spring constant of ≈140 N/m were improved by 6.1 times and 2.5 times, respectively, by coating with a PTC layer. We experimentally demonstrate high stability of the PTC layer in liquid by AFM imaging of a mica surface with atomic resolution in phosphate buffer saline solution for more than 2 h without any indication of possible contamination from the coating. The proposed method, using a PTC layer made of colloidal graphite, greatly enhances photothermal excitation efficiency even for a relatively stiff cantilever in liquid. PMID:27335733

  9. Radiation transport effects in heavy-ion beam--target interaction studies: Measurement of target opacity and beam conversion efficiency

    SciTech Connect

    Tahir, N. A.; Arnold, R. C.

    1989-07-01

    In this paper detailed simulations are presented of radiation-hydrodynamicresponse of gaseous cylindrical targets irradiated with heavy-ion beams thatwill be produced at the Gesellschaft f/umlt u/r Schwerionenforschung, Darmstadt,using a heavy-ion synchrotron (SIS) (/ital Heavy/ /ital Ion//usion/, AIP Conference Proceedings No. 152 (AIP, NewYork, 1986), p. 23). The purpose of this work is to explore material conditionsfor which the thermal radiation effects can be maximized. This is desirable inorder to study a number of interesting and important effects includingmaximization of conversion efficiency of the ion beam energy to thermalradiation and measurement of the target opacity in the SIS experiments. It isexpected that the SIS beams will produce a specific deposition power of 10 TW/g.The simulations in this paper show that a temperature of the order of 10 eVcould be achieved by the SIS beams using homogeneous, cylindrical Xe targets. Ithas been shown that with the help of these computer simulations one should beable to measure the target opacity in these experiments within a factor of 3.Also these calculations show that in the SIS experiments one should be able tohave a 50% conversion efficiency using a Xe target under optimum conditions. Ithas been found that the radiation effects will be optimized in the SISexperiments if the initial target density is of the order of 10/sup /minus/3/ g/cm/sup 3/.If the initial density is too high (of the order of 10/sup /minus/1/ g/cm/sup 3/ or more),hydrodynamic effects will dominate, while, on the other hand, if the initialdensity is too low (of the order of 10/sup /minus/4/ g/cm/sup 3/ or less), the electronthermal conductivity will take over.

  10. Basic aspects for improving the energy conversion efficiency of hetero-junction organic photovoltaic cells.

    PubMed

    Ryuzaki, Sou; Onoe, Jun

    2013-01-01

    Hetero-junction organic photovoltaic (OPV) cells consisting of donor (D) and acceptor (A) layers have been regarded as next-generation PV cells, because of their fascinating advantages, such as lightweight, low fabrication cost, resource free, and flexibility, when compared to those of conventional PV cells based on silicon and semiconductor compounds. However, the power conversion efficiency (η) of the OPV cells has been still around 8%, though more than 10% efficiency has been required for their practical use. To fully optimize these OPV cells, it is necessary that the low mobility of carriers/excitons in the OPV cells and the open circuit voltage (V OC), of which origin has not been understood well, should be improved. In this review, we address an improvement of the mobility of carriers/excitons by controlling the crystal structure of a donor layer and address how to increase the V OC for zinc octaethylporphyrin [Zn(OEP)]/C60 hetero-junction OPV cells [ITO/Zn(OEP)/C60/Al]. It was found that crystallization of Zn(OEP) films increases the number of inter-molecular charge transfer (IMCT) excitons and enlarges the mobility of carriers and IMCT excitons, thus significantly improving the external quantum efficiency (EQE) under illumination of the photoabsorption band due to the IMCT excitons. Conversely, charge accumulation of photo-generated carriers in the vicinity of the donor/acceptor (D/A) interface was found to play a key role in determining the V OC for the OPV cells. PMID:23853702

  11. A Strategy to Achieve High-Efficiency Organolead Trihalide Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Andalibi, Shabnam; Rostami, Ali; Darvish, Gafar; Moravvej-Farshi, Mohammad Kazem

    2016-07-01

    Recent theoretical and experimental reports have shown that organometal lead halide perovskite solar cells have attracted attention as a low-cost photovoltaic technology offering high power conversion efficiency. However, the photovoltaic efficiency of these materials is still limited by poor chemical and structural stability in the case of methylammonium lead triiodide and by large bandgap in the case of methylammonium lead tribromide or trichloride. To obtain high-performance devices, we have investigated the computationally optimal efficiency for these materials using the detailed-balance method and present optimal intermediate-band perovskite solar cells with high open-circuit voltage. We model different halide perovskites using density function theory calculations and study their bandgap and absorption coefficient. Based on calculation results, surprisingly Hg doping in different halide perovskites introduces a narrow partially filled intermediate band in the forbidden bandgap. We investigate electrical and optical properties of MAPb0.97Hg0.03I3, MAPb0.96Hg0.04Br3, and MAPb0.96Hg0.04Cl3 and calculate the high absorption efficiency of the different perovskite structures to create thin films suitable for photovoltaic devices.

  12. On the Achievable Efficiency-Fairness Tradeoff in Utility-Optimal MAC Protocols

    NASA Astrophysics Data System (ADS)

    Lee, Jang-Won; Chiang, Mung; Calderbank, A. Robert

    We use the network utility maximization (NUM) framework to create an efficient and fair medium access control (MAC) protocol for wireless networks. By adjusting the parameters in the utility objective functions of NUM problems, we control the tradeoff between efficiency and fairness of radio resource allocation through a rigorous and systematic design. In this paper, we propose a scheduling-based MAC protocol. Since it provides an upper-bound on the achievable performance, it establishes the optimality benchmarks for comparison with other algorithms in related work.

  13. Enhancement of starch conversion efficiency with free and immobilized pullalanase and alpha-1,4 glucosidase

    SciTech Connect

    Kumar, A.R.; Venkatasubramanian, K.

    1982-02-01

    Glucoamylase and pullulanase were immobilized on reconstituted bovine-hide collagen membranes using the covalent azide linkage method. A pretanning step was incorporated into the immobilization procedure to enable the support matrix to resist proteolytic activity while accommodating an operating temperature of 50 degrees Celcius. The immobilized glucoamylase and pullulanase activities were 0.91 and 0.022 mg dextrose equivalent (DE) min-1 cm-2 of membrane, respectively. Immobilized glucoamylase had a half-life of 50 days while the immobilized pullulanase had a half-life of 7 days. This is a considerably improved stability over that reported by other researchers. The enzymes were studied in their free and immobilized forms on a variety of starch substrates including waxy maize, a material which contains 80% alpha-1-6-glucosidic linkages. Substrate concentrations ranged from 1% to a typical commercial concentration of 30%. Conversion efficiencies of 90-92% DE were obtained with free and immobilized glucoamylase preparations. Conversion enhancements of 4-5 mg of DE above this level were obtained by the use of pullulanase in its free or immobilized forms. Close examination of free pullulanase stability as a function of pH indicated improved thermal stability at higher pH values. At 50 degrees Celcius and pH 5.0, the free enzyme was inactivated after 24 hours. At pH 7.0, the enzyme still possessed one-half its activity after 72 hours. Studies were conducted in both batch and continuous total recycle reactors. All experiments were conducted at 50 degrees Celcius. Experiments conducted with coimmobilized enzymes proved quite promising. Levels of conversion equivalent to those obtained with the individually immobilized enzymes were realized. (Refs. 16).

  14. Unraveling the Fundamental Mechanisms of Solvent-Additive-Induced Optimization of Power Conversion Efficiencies in Organic Photovoltaic Devices.

    PubMed

    Herath, Nuradhika; Das, Sanjib; Zhu, Jiahua; Kumar, Rajeev; Chen, Jihua; Xiao, Kai; Gu, Gong; Browning, James F; Sumpter, Bobby G; Ivanov, Ilia N; Lauter, Valeria

    2016-08-10

    The realization of controllable morphologies of bulk heterojunctions (BHJ) in organic photovoltaics (OPVs) is one of the key factors enabling high-efficiency devices. We provide new insights into the fundamental mechanisms essential for the optimization of power conversion efficiencies (PCEs) with additive processing to PBDTTT-CF:PC71BM system. We have studied the underlying mechanisms by monitoring the 3D nanostructural modifications in BHJs and correlated the modifications with the optical analysis and theoretical modeling of charge transport. Our results demonstrate profound effects of diiodooctane (DIO) on morphology and charge transport in the active layers. For small amounts of DIO (<3 vol %), DIO promotes the formation of a well-mixed donor-acceptor compact film and augments charge transfer and PCE. In contrast, for large amounts of DIO (>3 vol %), DIO facilitates a loosely packed mixed morphology with large clusters of PC71BM, leading to deterioration in PCE. Theoretical modeling of charge transport reveals that DIO increases the mobility of electrons and holes (the charge carriers) by affecting the energetic disorder and electric field dependence of the mobility. Our findings show the implications of phase separation and carrier transport pathways to achieve optimal device performances. PMID:27403964

  15. Sun to fibers (S2F): massively scalable collection and transmission of concentrated solar light for efficient energy conversion and storage

    NASA Astrophysics Data System (ADS)

    Díaz León, Juan J.; Garrett, Matthew P.; Zhang, Junce; Han, Katherine; Demaray, R. Ernest; Anderson, Roger W.; Lewandowski, Allan; Bottenberg, William; Kobayashi, Nobuhiko P.

    2014-10-01

    Concentrated solar energy has proven to be an efficient approach for both solar thermal energy applications and photovoltaics. Here, we propose a passive optical device, the Adiabatic Optical Coupler (AOC), that efficiently couples concentrated solar light from a primary solar concentrator into an optical fiber, enabling light collection and energy conversion/storage to be geographically separated, thus maximizing the overall system efficiency. The AOC offers secondary concentration of concentrated solar light through an adiabatic optical mode conversion process. Solar light, highly focused by this two stage concentrator, is delivered by optical fiber to either be subsequently converted to electricity or thermally stored. The ability to transport high energy light flux eliminates the need for high temperature working fluids in solar-thermal systems. In order to design the AOC and related peripherals, we used various modeling tools to cover different optical regimes at macroscopic and microscopic scales. We demonstrated a set of optical thin films with spatially varied refractive index up to 3 and negligible optical absorption by using proprietary sputtering technique to fabricate the AOC. We further studied the films using experimental measurements and theoretical analysis to optimize their optical properties. Preliminary cost analysis suggests that solar thermal power generation systems that employ our S2F concept could offer the cost and efficiency required to achieve the 2020 SunShot initiative levelized cost of electricity (LCOE) target. Success of this endeavor could change the energy conversion paradigm, and allow massively scalable concentrated solar energy utilization.

  16. Impacts of kafirin allelic diversity, starch content, and protein digestibility on ethanol conversion efficiency in grain sorghum

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seed protein and starch composition determines the efficiency of ethanol conversion in the production of grain-based biofuels. Sorghum, highly water- and nutrient-efficient, has the potential to replace fuel crops with greater irrigation and fertiliser requirements, such as maize. However, sorghum g...

  17. Stabilized Conversion Efficiency and Dye-Sensitized Solar Cells from Beta vulgaris Pigment

    PubMed Central

    Hernández-Martínez, Angel Ramon; Estévez, Miriam; Vargas, Susana; Rodríguez, Rogelio

    2013-01-01

    Dye-Sensitized Solar Cells (DSSCs), based on TiO2 and assembled using a dye from Beta vulgaris extract (BVE) with Tetraethylorthosilicate (TEOS), are reported. The dye BVE/TEOS increased its UV resistance, rendering an increase in the cell lifetime; the performance of these solar cells was compared to those prepared with BVE without TEOS. The efficiency η for the solar energy conversion was, for BVE and BVE/TEOS, of 0.89% ± 0.006% and 0.68% ± 0.006% with a current density Jsc of 2.71 ± 0.003 mA/cm2 and 2.08 ± 0.003 mA/cm2, respectively, using in both cases an irradiation of 100 mW/cm2 at 25 °C. The efficiency of the BVE solar cell dropped from 0.9 ± 0.006 to 0.85 ± 0.006 after 72 h of operation, whereas for the BVE/TEOS, the efficiency remained practically constant in the same period of time. PMID:23429194

  18. Improved photoelectric conversion efficiency from titanium oxide-coupled tin oxide nanoparticles formed in flame

    NASA Astrophysics Data System (ADS)

    Gu, Feng; Huang, Wenjuan; Wang, Shufen; Cheng, Xing; Hu, Yanjie; Li, Chunzhong

    2014-12-01

    The charge losses as a result of recombination to redox electrolyte and dye cation make tin oxide (SnO2)-based dye-sensitized solar cells (DSSCs) particularly inferior when compared with its titanium oxide (TiO2) counterpart. In this article, TiO2 nanocrystal is sealed in SnO2 by a modified flame spray pyrolysis (FSP) approach and the recombination losses to dye cation of SnO2 photoanode are effectively suppressed due to the negatively shifted Fermi level with the formation of bandedge-engineered core/shell structure. The fabricated TiO2@SnO2 (TSN)-device shows an open circuit voltage of 0.59 V and an efficiency of 3.82%, significantly better than those of the TiO2-, and SnO2-DSSCs devices. After surface modification, the conversion efficiency could be further improved to 7.87% while the open circuit voltage reaches 0.70 V. The higher efficiency of the TSN-based device is attributed to the enhanced electron injection arising from decreased interfacial charge recombination losses and improved electron transport. This strategy renders a new concept for further improvement of photovoltaic performance by engineering the dynamics of electron transport and recombination in DSSCs.

  19. New concepts for high efficiency energy conversion: The avalanche heterostructure and superlattice solar cells

    SciTech Connect

    Summers, C.J.; Rohatgi, A.; Torabi, A.; Harris, H.M. )

    1993-01-01

    This report describes investigation into the theory and technology of a novel heterojunction or superlattice, single-junction solar cell, which injects electrons across the heterointerface to produce highly efficient impact ionization of carriers in the lowband-gap side of the junction, thereby conserving their total energy. Also, the superlattice structure has the advantage of relaxing the need for perfect lattice matching at the p-n interface and will inhibit the cross diffusion of dopant atoms that typically occurs in heavy doping. This structure avoids the use of tunnel junctions that make it very difficult to achieve the predicted efficiencies in cascade cells, thus making it possible to obtain energy efficiencies that are competitive with those predicted for cascade solar cells with reduced complexity and cost. This cell structure could also be incorporated into other solar cell structures designed for wider spectral coverage.

  20. Reversibility and efficiency in electrocatalytic energy conversion and lessons from enzymes

    PubMed Central

    Armstrong, Fraser A.; Hirst, Judy

    2011-01-01

    Enzymes are long established as extremely efficient catalysts. Here, we show that enzymes can also be extremely efficient electrocatalysts (catalysts of redox reactions at electrodes). Despite being large and electronically insulating through most of their volume, some enzymes, when attached to an electrode, catalyze electrochemical reactions that are otherwise extremely sluggish (even with the best synthetic catalysts) and require a large overpotential to achieve a useful rate. These enzymes produce high electrocatalytic currents, displayed in single bidirectional voltammetric waves that switch direction (between oxidation and reduction) sharply at the equilibrium potential for the substrate redox couple. Notoriously irreversible processes such as CO2 reduction are thereby rendered electrochemically reversible—a consequence of molecular evolution responding to stringent biological drivers for thermodynamic efficiency. Enzymes thus set high standards for the catalysts of future energy technologies. PMID:21844379

  1. Carbon nanotube-amorphous silicon hybrid solar cell with improved conversion efficiency.

    PubMed

    Funde, Adinath M; Nasibulin, Albert G; Syed, Hashmi Gufran; Anisimov, Anton S; Tsapenko, Alexey; Lund, Peter; Santos, J D; Torres, I; Gandía, J J; Cárabe, J; Rozenberg, A D; Levitsky, Igor A

    2016-05-01

    We report a hybrid solar cell based on single walled carbon nanotubes (SWNTs) interfaced with amorphous silicon (a-Si). The high quality carbon nanotube network was dry transferred onto intrinsic a-Si forming Schottky junction for metallic SWNT bundles and heterojunctions for semiconducting SWNT bundles. The nanotube chemical doping and a-Si surface treatment minimized the hysteresis effect in current-voltage characteristics allowing an increase in the conversion efficiency to 1.5% under an air mass 1.5 solar spectrum simulator. We demonstrated that the thin SWNT film is able to replace a simultaneously p-doped a-Si layer and transparent conductive electrode in conventional amorphous silicon thin film photovoltaics. PMID:27005494

  2. Shape-dependent conversion efficiency of Si nanowire solar cells with polygonal cross-sections

    NASA Astrophysics Data System (ADS)

    He, Yan; Yu, Wangbing; Ouyang, Gang

    2016-06-01

    A deeper insight into shape-dependent power conversion efficiency (PCE) of Si nanowire (SiNW) solar cells with polygonal cross-sectional shapes, including trigon, tetragon, hexagon, and circle, has been explored based on the atomic-bond-relaxation approach and detailed balance principle. It has been found that the surface effect induced by the loss-coordination atoms located at edges and surfaces, as well as the thermal effect, plays the dominant roles for the band shift and PCE of SiNWs due to the lattice strain occurrence at the self-equilibrium state. Our predictions are consistent with the available evidences, providing an important advance in the development of Si-based nanostructures for the desirable applications.

  3. Conservation laws and conversion efficiency in ultraintense laser-overdense plasma interactions

    SciTech Connect

    Levy, M. C.; Wilks, S. C.; Tabak, M.; Baring, M. G.

    2013-10-15

    Particle coupling to the oscillatory and steady-state nonlinear force of an ultraintense laser is studied through analytic modeling and particle-in-cell simulations. The complex interplay between these absorption mechanisms—corresponding, respectively, to “hot” electrons and “hole punching” ions—is central to the viability of many ultraintense laser applications. Yet, analytic work to date has focused only on limiting cases of this key problem. In this paper, we develop a fully relativistic model in 1-D treating both modes of ponderomotive light absorption on equitable theoretical footing for the first time. Using this framework, analytic expressions for the conversion efficiencies into hole punching ions and into hot electrons are derived. Solutions for the relativistically correct hole punching velocity and the hot electron Lorentz factor are also calculated. Excellent agreement between analytic predictions and particle-in-cell simulations is demonstrated, and astrophysical analogies are highlighted.

  4. Carbon nanotube-amorphous silicon hybrid solar cell with improved conversion efficiency

    NASA Astrophysics Data System (ADS)

    Funde, Adinath M.; Nasibulin, Albert G.; Gufran Syed, Hashmi; Anisimov, Anton S.; Tsapenko, Alexey; Lund, Peter; Santos, J. D.; Torres, I.; Gandía, J. J.; Cárabe, J.; Rozenberg, A. D.; Levitsky, Igor A.

    2016-05-01

    We report a hybrid solar cell based on single walled carbon nanotubes (SWNTs) interfaced with amorphous silicon (a-Si). The high quality carbon nanotube network was dry transferred onto intrinsic a-Si forming Schottky junction for metallic SWNT bundles and heterojunctions for semiconducting SWNT bundles. The nanotube chemical doping and a-Si surface treatment minimized the hysteresis effect in current-voltage characteristics allowing an increase in the conversion efficiency to 1.5% under an air mass 1.5 solar spectrum simulator. We demonstrated that the thin SWNT film is able to replace a simultaneously p-doped a-Si layer and transparent conductive electrode in conventional amorphous silicon thin film photovoltaics.

  5. Methods of Measuring Energy Conversion Efficiency in Dye-sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Koide, Naoki; Chiba, Yasuo; Han, Liyuan

    2005-06-01

    The current-voltage characteristics of dye-sensitized solar cells (DSCs) were measured and compared with those of crystalline silicon solar cells. It was found that the energy conversion efficiency of DSCs is dependent on voltage sweep direction and sampling delay time (Td). Measurement of the transient photocurrent revealed that this dependence is due to the longer time constant of DSCs. This dependence was also confirmed in a simulation of current-voltage curves based on an equivalent circuit model of DSCs. Analysis of the current-voltage characteristics of polymer-based bulk heterojunction solar cells (BHSCs) and simulated measurements showed that the longer time constant is due to slow movement of ions in the electrolyte. To improve accuracy, the I-V measurement should be carried out from short circuit to open circuit with Td of 100 ms or longer.

  6. Efficient catalytic system for the conversion of fructose into 5-ethoxymethylfurfural.

    PubMed

    Wang, Hongliang; Deng, Tiansheng; Wang, Yingxiong; Qi, Yongqin; Hou, Xianglin; Zhu, Yulei

    2013-05-01

    DMSO can improve the selectivity of 5-hydroxymethylfurfural (HMF) in the conversion of carbohydrates. However, one of the bottlenecks in its application is product separation. Thus a one-pot synthesis of 5-ethoxymethylfurfural (EMF) rather than HMF from fructose in ethanol-DMSO was investigated. Phosphotungstic acid was used as an effective catalyst. The yield of EMF can be reached as high as 64% in the mixed solvent system of DMSO and ethanol within 130 min at 140 °C. Ethyl levulinate (LAE) was detected as the main by-product, the yield of which increased with the reaction time, temperature and the amount of catalyst. In addition, the existence of water could significantly reduce the yield of EMF and increased the yield of LAE. Most importantly, it was discovered that EMF could be much more efficiently extracted from the reaction solvent system by some organic solvents than HMF. PMID:23567707

  7. Solution-processed small-molecule solar cells: breaking the 10% power conversion efficiency.

    PubMed

    Liu, Yongsheng; Chen, Chun-Chao; Hong, Ziruo; Gao, Jing; Yang, Yang Michael; Zhou, Huanping; Dou, Letian; Li, Gang; Yang, Yang

    2013-01-01

    A two-dimensional conjugated small molecule (SMPV1) was designed and synthesized for high performance solution-processed organic solar cells. This study explores the photovoltaic properties of this molecule as a donor, with a fullerene derivative as an acceptor, using solution processing in single junction and double junction tandem solar cells. The single junction solar cells based on SMPV1 exhibited a certified power conversion efficiency of 8.02% under AM 1.5 G irradiation (100 mW cm(-2)). A homo-tandem solar cell based on SMPV1 was constructed with a novel interlayer (or tunnel junction) consisting of bilayer conjugated polyelectrolyte, demonstrating an unprecedented PCE of 10.1%. These results strongly suggest solution-processed small molecular materials are excellent candidates for organic solar cells. PMID:24285006

  8. Conservation laws and conversion efficiency in ultraintense laser-overdense plasma interactions

    NASA Astrophysics Data System (ADS)

    Levy, M. C.; Wilks, S. C.; Tabak, M.; Baring, M. G.

    2013-10-01

    Particle coupling to the oscillatory and steady-state nonlinear force of an ultraintense laser is studied through analytic modeling and particle-in-cell simulations. The complex interplay between these absorption mechanisms—corresponding, respectively, to "hot" electrons and "hole punching" ions—is central to the viability of many ultraintense laser applications. Yet, analytic work to date has focused only on limiting cases of this key problem. In this paper, we develop a fully relativistic model in 1-D treating both modes of ponderomotive light absorption on equitable theoretical footing for the first time. Using this framework, analytic expressions for the conversion efficiencies into hole punching ions and into hot electrons are derived. Solutions for the relativistically correct hole punching velocity and the hot electron Lorentz factor are also calculated. Excellent agreement between analytic predictions and particle-in-cell simulations is demonstrated, and astrophysical analogies are highlighted.

  9. Efficient Conversion of Inulin to Inulooligosaccharides through Endoinulinase from Aspergillus niger.

    PubMed

    Xu, Yanbing; Zheng, Zhaojuan; Xu, Qianqian; Yong, Qiang; Ouyang, Jia

    2016-03-30

    Inulooligosaccharides (IOS) represent an important class of oligosaccharides at industrial scale. An efficient conversion of inulin to IOS through endoinulinase from Aspergillus niger is presented. A 1482 bp codon optimized gene fragment encoding endoinulinase from A. niger DSM 2466 was cloned into pPIC9K vector and was transformed into Pichia pastoris KM71. Maximum activity of the recombinant endoinulinase, 858 U/mL, was obtained at 120 h of the high cell density fermentation process. The optimal conditions for inulin hydrolysis using the recombinant endoinulinase were investigated. IOS were harvested with a high concentration of 365.1 g/L and high yield up to 91.3%. IOS with different degrees of polymerization (DP, mainly DP 3-6) were distributed in the final reaction products. PMID:26961750

  10. Exciton Diffusion in Conjugated Polymers: From Fundamental Understanding to Improvement in Photovoltaic Conversion Efficiency.

    PubMed

    Tamai, Yasunari; Ohkita, Hideo; Benten, Hiroaki; Ito, Shinzaburo

    2015-09-01

    Singlet exciton diffusion plays a central role in the photovoltaic conversion in organic photovoltaics (OPVs). Upon light absorption, singlet excitons are promptly generated in organic materials instead of charge carriers because the dielectric constant (εr) is small (∼3-4), which is in sharp contrast to inorganic and perovskite solar cells. In order to convert to charge carriers, excitons need to diffuse into an interface between electron donor and acceptor materials before deactivating to the ground state. Therefore, fundamental understanding of exciton diffusion dynamics is one of the most important issues to further improve OPVs. We highlight recent leading studies in this field and describe several approaches for efficient exciton harvesting at the interface in OPVs. PMID:26269208

  11. High-efficiency thin-film solar cells for the conversion of concentrated radiation

    NASA Astrophysics Data System (ADS)

    Andreev, V. M.; Burba, T. S.; Dorgan, V. V.; Trofim, V. G.; Chumak, V. A.

    1987-09-01

    The objective of the study was to investigate the possibility of increasing the efficiency of thin-film solar cells with coplanar back contacts for the conversion of concentrated solar radiation. It is shown that, in the thin-film solar cells described here, the cell shading factor can be reduced to a minimum since it does not depend on the p-contact area but is determined solely by the area of etched grooves in a thin (7 microns) layer of GaAs. The cells used in the study have a shading factor of 2.5 percent, and a further reduction by an order of magnitude is shown to be possible.

  12. Report of feasibility study on international-cooperation in high efficient energy conversion technology

    NASA Astrophysics Data System (ADS)

    1993-03-01

    With regard to accelerated introduction of high efficient energy conversion technology to developing countries, the paper investigates the countries' thoughts of the introduction of the technology and the status of the introduction bases. The countries for survey are the Philippines, Indonesia, Malaysia and Thailand. The Philippine government expects to develop cogeneration as well as large power sources and to widen effective use of natural energy. In Indonesia, they largely expect effective use of biomass energy using Stirling engines by international cooperation and the promoted local electrification using standalone distributed fuel cells. In Malaysia, they have great expectations of the introduction of air conditioning facilities using Stirling engines and the use of standalone distributed fuel cells for promotion of local electrification. Thailand hopes for the use of Stirling engines to air conditioning systems, and the development of solar Stirling generators with solar energy as a heat source and electric vehicles.

  13. Correlation between laser absorption and radiation conversion efficiency in laser produced tin plasma

    SciTech Connect

    Matsukuma, Hiraku Hosoda, Tatsuya; Fujioka, Shinsuke; Nishimura, Hiroaki; Sunahara, Atsushi; Yanagida, Tatsuya; Tomuro, Hiroaki; Kouge, Kouichiro; Kodama, Takeshi

    2015-09-21

    The correlation between the laser absorption and the conversion efficiency (CE) for 13.5 nm extreme ultraviolet (EUV) light in a laser-produced tin plasma was investigated. The absorption rate α and the CE were measured simultaneously for a laser-pre-formed low-density tin target as a function of the time delay between the pre-pulse and the main laser pulse. A clear and positive correlation between α and CE was found with increasing delay time; however, the CE decreases rapidly at longer delay times. This result is partly attributed to a reduction in the absorption rate, but is mainly attributed to the self-absorption of EUV light in excessively long-scale plasmas.

  14. Efficient Power Converters for PV Arrays : Scalable Submodule Power Conversion for Utility-Scale Photovoltaics

    SciTech Connect

    2012-02-23

    Solar ADEPT Project: SolarBridge is developing a new power conversion technique to improve the energy output of PV power plants. This new technique is specifically aimed at large plants where many solar panels are connected together. SolarBridge is correcting for the inefficiencies that occur when two solar panels that encounter different amounts of sun are connected together. In most conventional PV system, the weakest panel limits the energy production of the entire system. That’s because all of the energy collected by the PV system feeds into a single collection point where a central inverter then converts it into useable energy for the grid. SolarBridge has found a more efficient and cost-effective way to convert solar energy, correcting these power differences before they reach the grid.

  15. Efficient conversion of biomass into lipids by using the simultaneous saccharification and enhanced lipid production process

    PubMed Central

    2013-01-01

    Background Microbial lipid production by using lignocellulosic biomass as the feedstock holds a great promise for biodiesel production and biorefinery. This usually involves hydrolysis of biomass into sugar-rich hydrolysates, which are then used by oleaginous microorganisms as the carbon and energy sources to produce lipids. However, the costs of microbial lipids remain prohibitively high for commercialization. More efficient and integrated processes are pivotal for better techno-economics of microbial lipid technology. Results Here we describe the simultaneous saccharification and enhanced lipid production (SSELP) process that is highly advantageous in terms of converting cellulosic materials into lipids, as it integrates cellulose biomass hydrolysis and lipid biosynthesis. Specifically, Cryptococcus curvatus cells prepared in a nutrient-rich medium were inoculated at high dosage for lipid production in biomass suspension in the presence of hydrolytic enzymes without auxiliary nutrients. When cellulose was loaded at 32.3 g/L, cellulose conversion, cell mass, lipid content and lipid coefficient reached 98.5%, 12.4 g/L, 59.9% and 204 mg/g, respectively. Lipid yields of the SSELP process were higher than those obtained by using the conventional process where cellulose was hydrolyzed separately. When ionic liquid pretreated corn stover was used, both cellulose and hemicellulose were consumed simultaneously. No xylose was accumulated over time, indicating that glucose effect was circumvented. The lipid yield reached 112 mg/g regenerated corn stover. This process could be performed without sterilization because of the absence of auxiliary nutrients for bacterial contamination. Conclusions The SSELP process facilitates direct conversion of both cellulose and hemicellulose of lignocellulosic materials into microbial lipids. It greatly reduces time and capital costs while improves lipid coefficient. Optimization of the SSELP process at different levels should further

  16. Designing interfaces of hydrogenase-nanomaterial hybrids for efficient solar conversion.

    PubMed

    King, Paul W

    2013-01-01

    The direct conversion of sunlight into biofuels is an intriguing alternative to a continued reliance on fossil fuels. Natural photosynthesis has long been investigated both as a potential solution, and as a model for utilizing solar energy to drive a water-to-fuel cycle. The molecules and organizational structure provide a template to inspire the design of efficient molecular systems for photocatalysis. A clear design strategy is the coordination of molecular interactions that match kinetic rates and energetic levels to control the direction and flow of energy from light harvesting to catalysis. Energy transduction and electron-transfer reactions occur through interfaces formed between complexes of donor-acceptor molecules. Although the structures of several of the key biological complexes have been solved, detailed descriptions of many electron-transfer complexes are lacking, which presents a challenge to designing and engineering biomolecular systems for solar conversion. Alternatively, it is possible to couple the catalytic power of biological enzymes to light harvesting by semiconductor nanomaterials. In these molecules, surface chemistry and structure can be designed using ligands. The passivation effect of the ligand can also dramatically affect the photophysical properties of the semiconductor, and energetics of external charge-transfer. The length, degree of bond saturation (aromaticity), and solvent exposed functional groups of ligands can be manipulated to further tune the interface to control molecular assembly, and complex stability in photocatalytic hybrids. The results of this research show how ligand selection is critical to designing molecular interfaces that promote efficient self-assembly, charge-transfer and photocatalysis. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems. PMID:23541891

  17. Device engineering of perovskite solar cells to achieve near ideal efficiency

    SciTech Connect

    Agarwal, Sumanshu E-mail: prnair@ee.iitb.ac.in; Nair, Pradeep R. E-mail: prnair@ee.iitb.ac.in

    2015-09-21

    Despite the exciting recent research on perovskite based solar cells, the design space for further optimization and the practical limits of efficiency are not well known in the community. In this letter, we address these aspects through theoretical calculations and detailed numerical simulations. Here, we first provide the detailed balance limit efficiency in the presence of radiative and Auger recombination. Then, using coupled optical and carrier transport simulations, we identify the physical mechanisms that contribute towards bias dependent carrier collection, and hence low fill factors of current perovskite based solar cells. Our detailed simulations indicate that it is indeed possible to achieve efficiencies and fill factors greater than 25% and 85%, respectively, with near ideal super-position characteristics even in the presence of Auger recombination.

  18. Elevated soil nitrogen pools after conversion of turfgrass to water-efficient residential landscapes

    NASA Astrophysics Data System (ADS)

    Heavenrich, Hannah; Hall, Sharon J.

    2016-08-01

    As a result of uncertain resource availability and growing populations, city managers are implementing conservation plans that aim to provide services for people while reducing household resource use. For example, in the US, municipalities are incentivizing homeowners to replace their water-intensive turfgrass lawns with water-efficient landscapes consisting of interspersed drought-tolerant shrubs and trees with rock or mulch groundcover (e.g. xeriscapes, rain gardens, water-wise landscapes). While these strategies are likely to reduce water demand, the consequences for other ecosystem services are unclear. Previous studies in controlled, experimental landscapes have shown that conversion from turfgrass to shrubs may lead to high rates of nutrient leaching from soils. However, little is known about the long-term biogeochemical consequences of this increasingly common land cover change across diverse homeowner management practices. We explored the fate of soil nitrogen (N) across a chronosequence of land cover change from turfgrass to water-efficient landscapes in privately owned yards in metropolitan Phoenix, Arizona, in the arid US Southwest. Soil nitrate ({{{{NO}}}3}-–N) pools were four times larger in water-efficient landscapes (25 ± 4 kg {{{{NO}}}3}-–N/ha 0–45 cm depth) compared to turfgrass lawns (6 ± 7 kg {{{{NO}}}3}-–N/ha). Soil {{{{NO}}}3}-–N also varied significantly with time since landscape conversion; the largest pools occurred at 9–13 years after turfgrass removal and declined to levels comparable to turfgrass thereafter. Variation in soil {{{{NO}}}3}-–N with landscape age was strongly influenced by management practices related to soil water availability, including shrub cover, sub-surface plastic sheeting, and irrigation frequency. Our findings show that transitioning from turfgrass to water-efficient residential landscaping can lead to an accumulation of {{{{NO}}}3}-–N that may be lost from the plant rooting zone over time following

  19. Protection of humans by plant glucosinolates: efficiency of conversion of glucosinolates to isothiocyanates by the gastrointestinal microflora.

    PubMed

    Fahey, Jed W; Wehage, Scott L; Holtzclaw, W David; Kensler, Thomas W; Egner, Patricia A; Shapiro, Theresa A; Talalay, Paul

    2012-04-01

    Plant-based diets rich in crucifers are effective in preventing cancer and other chronic diseases. Crucifers contain very high concentrations of glucosinolates (GS; β-thioglucoside-N-hydroxysulfates). Although not themselves protective, GS are converted by coexisting myrosinases to bitter isothiocyanates (ITC) which defend plants against predators. Coincidentally, ITC also induce mammalian genes that regulate defenses against oxidative stress, inflammation, and DNA-damaging electrophiles. Consequently, the efficiency of conversion of GS to ITC may be critical in controlling the health-promoting benefits of crucifers. If myrosinase is heat-inactivated by cooking, the gastrointestinal microflora converts GS to ITC, a process abolished by enteric antibiotics and bowel cleansing. When single oral doses of GS were administered as broccoli sprout extracts (BSE) to two dissimilar populations (rural Han Chinese and racially mixed Baltimoreans) patterns of excretions of urinary dithiocarbamates (DTC) were very similar. Individual conversions in both populations varied enormously, from about 1% to more than 40% of dose. In contrast, administration of ITC (largely sulforaphane)-containing BSE resulted in uniformly high (70%-90%) conversions to urinary DTC. Despite the remarkably large range of conversion efficiencies between individuals, repeated determinations within individuals were much more consistent. The rates of urinary excretion (slow or fast) were unrelated to the ultimate magnitudes (low or high) of these conversions. Although no demographic factors affecting conversion efficiency have been identified, there are clearly diurnal variations: conversion of GS to DTC was greater during the day, but conversion of ITC to DTC was more efficient at night. PMID:22318753

  20. Influences of bulk and surface recombinations on the power conversion efficiency of perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Xie, Ziang; Sun, Shuren; Yan, Yu; Wang, Wei; Qin, Laixiang; Qin, G. G.

    2016-07-01

    For a novel kind of solar cell (SC) material, it is critical to estimate how far the power conversion efficiencies (PCEs) of the SCs made of it can go. In 2010 Han and Chen proposed the equation for the ultimate efficiency of SCs without considering the carrier recombination η un. η un is capable of estimating the theoretical upper limits of the SC efficiencies and has attracted much attention. However, carrier recombination, which is one of the key factors influencing the PCEs of the SCs, is ignored in the equation for η un. In this paper, we develop a novel equation to calculate the ultimate efficiency for the SCs, η ur, which considers both the bulk and the surface carrier recombinations. The novel equation for η ur can estimate how much the bulk and the surface carrier recombinations influence the PCEs of the SCs. Moreover, with η ur we can estimate how much PCE improvement space can be gained only by reducing the influence of the carrier recombination to the least. The perovskite organometal trihalide SCs have attracted tremendous attention lately. For the planar CH3NH3PbI3 SCs, in the material depth range from 31.25–2000 nm, we apply the equation of η ur to investigate how the bulk and the surface carrier recombinations affect PCE. From a typically reported PCE of 15% for the planar CH3NH3PbI3 SC, using the equation of η ur, it is concluded that by reducing the influence of carrier recombination to the least the improvement of PCE is in the range of 17–30%.

  1. Achieving palliative care research efficiency through defining and benchmarking performance metrics

    PubMed Central

    Lodato, Jordan E.; Aziz, Noreen; Bennett, Rachael E.; Abernethy, Amy P.; Kutner, Jean S.

    2014-01-01

    Purpose of Review Research efficiency is gaining increasing attention in the research enterprise, including palliative care research. The importance of generating meaningful findings and translating these scientific advances to improved patient care creates urgency in the field to address well-documented system inefficiencies. The Palliative Care Research Cooperative Group (PCRC) provides useful examples for ensuring research efficiency in palliative care. Recent Findings Literature on maximizing research efficiency focuses on the importance of clearly delineated process maps, working instructions, and standard operating procedures (SOPs) in creating synchronicity in expectations across research sites. Examples from the PCRC support these objectives and suggest that early creation and employment of performance metrics aligned with these processes are essential to generate clear expectations and identify benchmarks. These benchmarks are critical in effective monitoring and ultimately the generation of high quality findings that are translatable to clinical populations. Prioritization of measurable goals and tasks to ensure that activities align with programmatic aims is critical. Summary Examples from the PCRC affirm and expand the existing literature on research efficiency, providing a palliative care focus. Operating procedures, performance metrics, prioritization, and monitoring for success should all be informed by and inform the process map to achieve maximum research efficiency. PMID:23080309

  2. Energy efficiency enhancements for semiconductors, communications, sensors and software achieved in cool silicon cluster project

    NASA Astrophysics Data System (ADS)

    Ellinger, Frank; Mikolajick, Thomas; Fettweis, Gerhard; Hentschel, Dieter; Kolodinski, Sabine; Warnecke, Helmut; Reppe, Thomas; Tzschoppe, Christoph; Dohl, Jan; Carta, Corrado; Fritsche, David; Tretter, Gregor; Wiatr, Maciej; Detlef Kronholz, Stefan; Mikalo, Ricardo Pablo; Heinrich, Harald; Paulo, Robert; Wolf, Robert; Hübner, Johannes; Waltsgott, Johannes; Meißner, Klaus; Richter, Robert; Michler, Oliver; Bausinger, Markus; Mehlich, Heiko; Hahmann, Martin; Möller, Henning; Wiemer, Maik; Holland, Hans-Jürgen; Gärtner, Roberto; Schubert, Stefan; Richter, Alexander; Strobel, Axel; Fehske, Albrecht; Cech, Sebastian; Aßmann, Uwe; Pawlak, Andreas; Schröter, Michael; Finger, Wolfgang; Schumann, Stefan; Höppner, Sebastian; Walter, Dennis; Eisenreich, Holger; Schüffny, René

    2013-07-01

    An overview about the German cluster project Cool Silicon aiming at increasing the energy efficiency for semiconductors, communications, sensors and software is presented. Examples for achievements are: 1000 times reduced gate leakage in transistors using high-fc (HKMG) materials compared to conventional poly-gate (SiON) devices at the same technology node; 700 V transistors integrated in standard 0.35 μm CMOS; solar cell efficiencies above 19% at < 200 W/m2 irradiation; 0.99 power factor, 87% efficiency and 0.088 distortion factor for dc supplies; 1 ns synchronization resolution via Ethernet; database accelerators allowing 85% energy savings for servers; adaptive software yielding energy reduction of 73% for e-Commerce applications; processors and corresponding data links with 40% and 70% energy savings, respectively, by adaption of clock frequency and supply voltage in less than 20 ns; clock generator chip with tunable frequency from 83-666 MHz and 0.62-1.6 mW dc power; 90 Gb/s on-chip link over 6 mm and efficiency of 174 fJ/mm; dynamic biasing system doubling efficiency in power amplifiers; 60 GHz BiCMOS frontends with dc power to bandwidth ratio of 0.17 mW/MHz; driver assistance systems reducing energy consumption by 10% in cars Contribution to the Topical Issue “International Semiconductor Conference Dresden-Grenoble - ISCDG 2012”, Edited by Gérard Ghibaudo, Francis Balestra and Simon Deleonibus.

  3. Hot-electron-transfer enhancement for the efficient energy conversion of visible light.

    PubMed

    Yu, Sungju; Kim, Yong Hwa; Lee, Su Young; Song, Hyeon Don; Yi, Jongheop

    2014-10-13

    Great strides have been made in enhancing solar energy conversion by utilizing plasmonic nanostructures in semiconductors. However, current generation with plasmonic nanostructures is still somewhat inefficient owing to the ultrafast decay of plasmon-induced hot electrons. It is now shown that the ultrafast decay of hot electrons across Au nanoparticles can be significantly reduced by strong coupling with CdS quantum dots and by a Schottky junction with perovskite SrTiO3 nanoparticles. The designed plasmonic nanostructure with three distinct components enables a hot-electron-assisted energy cascade for electron transfer, CdS→Au→SrTiO3, as demonstrated by steady-state and time-resolved photoluminescence spectroscopy. Consequently, hot-electron transfer enabled the efficient production of H2 from water as well as significant electron harvesting under irradiation with visible light of various wavelengths. These findings provide a new approach for overcoming the low efficiency that is typically associated with plasmonic nanostructures. PMID:25169852

  4. Efficient Eucalypt Cell Wall Deconstruction and Conversion for Sustainable Lignocellulosic Biofuels

    PubMed Central

    Healey, Adam L.; Lee, David J.; Furtado, Agnelo; Simmons, Blake A.; Henry, Robert J.

    2015-01-01

    In order to meet the world’s growing energy demand and reduce the impact of greenhouse gas emissions resulting from fossil fuel combustion, renewable plant-based feedstocks for biofuel production must be considered. The first-generation biofuels, derived from starches of edible feedstocks, such as corn, create competition between food and fuel resources, both for the crop itself and the land on which it is grown. As such, biofuel synthesized from non-edible plant biomass (lignocellulose) generated on marginal agricultural land will help to alleviate this competition. Eucalypts, the broadly defined taxa encompassing over 900 species of Eucalyptus, Corymbia, and Angophora are the most widely planted hardwood tree in the world, harvested mainly for timber, pulp and paper, and biomaterial products. More recently, due to their exceptional growth rate and amenability to grow under a wide range of environmental conditions, eucalypts are a leading option for the development of a sustainable lignocellulosic biofuels. However, efficient conversion of woody biomass into fermentable monomeric sugars is largely dependent on pretreatment of the cell wall, whose formation and complexity lend itself toward natural recalcitrance against its efficient deconstruction. A greater understanding of this complexity within the context of various pretreatments will allow the design of new and effective deconstruction processes for bioenergy production. In this review, we present the various pretreatment options for eucalypts, including research into understanding structure and formation of the eucalypt cell wall. PMID:26636077

  5. Efficient Eucalypt Cell Wall Deconstruction and Conversion for Sustainable Lignocellulosic Biofuels.

    PubMed

    Healey, Adam L; Lee, David J; Furtado, Agnelo; Simmons, Blake A; Henry, Robert J

    2015-01-01

    In order to meet the world's growing energy demand and reduce the impact of greenhouse gas emissions resulting from fossil fuel combustion, renewable plant-based feedstocks for biofuel production must be considered. The first-generation biofuels, derived from starches of edible feedstocks, such as corn, create competition between food and fuel resources, both for the crop itself and the land on which it is grown. As such, biofuel synthesized from non-edible plant biomass (lignocellulose) generated on marginal agricultural land will help to alleviate this competition. Eucalypts, the broadly defined taxa encompassing over 900 species of Eucalyptus, Corymbia, and Angophora are the most widely planted hardwood tree in the world, harvested mainly for timber, pulp and paper, and biomaterial products. More recently, due to their exceptional growth rate and amenability to grow under a wide range of environmental conditions, eucalypts are a leading option for the development of a sustainable lignocellulosic biofuels. However, efficient conversion of woody biomass into fermentable monomeric sugars is largely dependent on pretreatment of the cell wall, whose formation and complexity lend itself toward natural recalcitrance against its efficient deconstruction. A greater understanding of this complexity within the context of various pretreatments will allow the design of new and effective deconstruction processes for bioenergy production. In this review, we present the various pretreatment options for eucalypts, including research into understanding structure and formation of the eucalypt cell wall. PMID:26636077

  6. Optimization of nanoparticle structure for improved conversion efficiency of dye solar cell

    SciTech Connect

    Mohamed, Norani Muti; Zaine, Siti Nur Azella

    2014-10-24

    Heavy dye loading and the ability to contain the light within the thin layer (typically ∼12 μm) are the requirement needed for the photoelectrode material in order to enhance the harvesting efficiency of dye solar cell. This can be realized by optimizing the particle size with desirable crystal structure. The paper reports the investigation on the dependency of the dye loading and light scattering on the properties of nanostructured photoelectrode materials by comparing 4 different samples of TiO{sub 2} in the form of nanoparticles and micron-sized TiO{sub 2} aggregates which composed of nanocrystallites. Their properties were evaluated by using scanning electron microscopy, X-ray diffraction and UVVis spectroscopy while the performance of the fabricated test cells were measured using universal photovoltaic test system (UPTS) under 1000 W/cm{sup 2} intensity of radiation. Nano sized particles provide large surface area which allow for greater dye adsorption but have no ability to retain the incident light in the TiO{sub 2} film. In contrast, micron-sized particles in the form of aggregates can generate light scattering allowing the travelling distance of the light to be extended and increasing the interaction between the photons and dye molecules adsorb on TiO{sub 2}nanocrystallites. This resulted in an improvement in the conversion efficiency of the aggregates that demonstrates the close relation between light scattering effect and the structure of the photolectrode film.

  7. Enhanced power conversion efficiency of dye-sensitized solar cells assisted with phosphor materials

    NASA Astrophysics Data System (ADS)

    Lee, Yong-Min; Kim, Dong In; Hwang, Ki-Hwan; Nam, Sang Hun; Boo, Jin-Hyo

    2016-07-01

    Theoretically dye-sensitized solar cells (DSSCs) are high efficiency solar cells. However, DSSCs have lower power conversion efficiency (PCE) than silicon based solar cells. In this study, we use scattering layer and phosphor materials, such as ZrO2 and Zn2SiO4:Mn (Green), to enhance the PCE of DSSCs. The scattering layer and phosphor materials were prepared and used as an effective scattering layer on the transparent TiO2 photoelectrode through the doctor blade method. We confirmed that the scattering layer improves the PCE and J sc due to the enhancement of light harvesting by increasing the scattering and absorbance in the visible range. Under sun illumination AM 1.5 conditions, the PCE of the mesoporous TiO2 based DSSCs was 5.18%. The PCE of the DSSCs with ZrO2 scattering layer was 5.61% and Zn2SiO4:Mn as the scattering layer was enhanced to 5.72%. In order to compare the change in optical properties, DSSCs were measured by EQE, reflectance and PCE. At the same time, FE-SEM and XRD were used to confirm the structural changes in each layer. [Figure not available: see fulltext.

  8. The Liquid Droplet Radiator - an Ultralightweight Heat Rejection System for Efficient Energy Conversion in Space

    NASA Technical Reports Server (NTRS)

    Mattick, A. T.; Hertzberg, A.

    1984-01-01

    A heat rejection system for space is described which uses a recirculating free stream of liquid droplets in place of a solid surface to radiate waste heat. By using sufficiently small droplets ( 100 micron diameter) of low vapor pressure liquids the radiating droplet sheet can be made many times lighter than the lightest solid surface radiators (heat pipes). The liquid droplet radiator (LDR) is less vulnerable to damage by micrometeoroids than solid surface radiators, and may be transported into space far more efficiently. Analyses are presented of LDR applications in thermal and photovoltaic energy conversion which indicate that fluid handling components (droplet generator, droplet collector, heat exchanger, and pump) may comprise most of the radiator system mass. Even the unoptimized models employed yield LDR system masses less than heat pipe radiator system masses, and significant improvement is expected using design approaches that incorporate fluid handling components more efficiently. Technical problems (e.g., spacecraft contamination and electrostatic deflection of droplets) unique to this method of heat rejectioon are discussed and solutions are suggested.

  9. The liquid droplet radiator - An ultralightweight heat rejection system for efficient energy conversion in space

    NASA Technical Reports Server (NTRS)

    Mattick, A. T.; Hertzberg, A.

    1981-01-01

    A heat rejection system for space is described which uses a recirculating free stream of liquid droplets in place of a solid surface to radiate waste heat. By using sufficiently small droplets (less than about 100 micron diameter) of low vapor pressure liquids (tin, tin-lead-bismuth eutectics, vacuum oils) the radiating droplet sheet can be made many times lighter than the lightest solid surface radiators (heat pipes). The liquid droplet radiator (LDR) is less vulnerable to damage by micrometeoroids than solid surface radiators, and may be transported into space far more efficiently. Analyses are presented of LDR applications in thermal and photovoltaic energy conversion which indicate that fluid handling components (droplet generator, droplet collector, heat exchanger, and pump) may comprise most of the radiator system mass. Even the unoptimized models employed yield LDR system masses less than heat pipe radiator system masses, and significant improvement is expected using design approaches that incorporate fluid handling components more efficiently. Technical problems (e.g., spacecraft contamination and electrostatic deflection of droplets) unique to this method of heat rejection are discussed and solutions are suggested.

  10. Aspects for efficient wide spectral band THz generation via CO2 laser down conversion

    NASA Astrophysics Data System (ADS)

    Panchenko, Yu. N.; Andreev, Yu. M.; Lanskii, G. V.; Losev, V. F.; Lubenko, D. M.

    2015-02-01

    Detailed model study of THz generation by CO2 laser down-conversion in pure and solid solution crystals GaSe1-xSx is carried out for the first time. Both forward and backward collinear interactions of common (eo-e, oe-e, oe-o, oo-e, ee-o) and original (ee-e, oo-o) types are considered. Possibility of realization, phase matching angles and figure of merits are estimated for line mixing within 9 μm and 10 μm emission bands, as well between them. Dispersion properties of o- and e-wave refractive indices and absorption coefficients for GaSe, GaS and GaSe1-xSx crystals were preliminary measured by THz-TDS, approximated in the equation form and then used in the study. Estimated results are presented in the form of 3-D figures that are suitable for rapid analyses of DFG parameters. The most efficient type of interaction is eo-o type. Optimally doped (x = 0.09-0.13) GaSe1-xSx crystals are from 4 to 5 times more efficient at limit pump intensity than not doped GaSe crystals.

  11. A thin-film polycrystalline photoelectrochemical cell with 8% solar conversion efficiency

    NASA Astrophysics Data System (ADS)

    Hodes, G.

    1980-05-01

    A thin-film polycrystalline CdSe(0.65)Te(0.35)/polysulfide-based photoelectrochemical solar cell with an energy conversion efficiency of up to 8% is presented. Cell electrodes were prepared by painting a slurry of sintered CdSe(0.65)Te(0.35) powder onto a Ti substrate and then annealing in an inert atmosphere and etching by various means. Solar efficiencies of the electrodes immersed in an aqueous electrolyte 1 M in KOH, Na2S and S with a counter electrode of sulfide brass gauze of up to 5% were obtained following a HCl:HNO3 etch, up to 5.5% following etching in dilute aqueous CrO3 and up to 8.0% following photoetching and K2CrO4 treatment. The spectral response of the anode in polysulfide solution exhibits a short-wavelength cutoff due to electrolyte absorption, a flat plateau region, and a fairly sharp long-wavelength cut-off indicating an effective band gap of about 1.45 eV, similar to that of CdTe. Output stability has been found to decrease with increasing output current, remaining stable for more than 21 h at a current of 20 mA/sq cm.

  12. Efficient light-to-electrical energy conversion with dithiocarbamate-ruthenium polypyridyl sensitizers

    SciTech Connect

    Argazzi, R.; Bignozzi, C.A.; Hasselmann, G.M.; Meyer, G.J.

    1998-09-07

    New Ru(dcbH)(dcbH{sub 2})(L) sensitizers, where L is diethyldithiocarbamate, dibenzyldithiocarbamate, or pyrrolidinedithiocarbamate, dcbH is 4-(COOH)-4{prime}-(COO{sup {minus}})-2,2{prime}-bipyridine, and dcbH{sub 2} is 4,4{prime}-(COOH){sub 2}-2,2{prime}-bipyridine, have been synthesized, characterized, and anchored to nanocrystalline TiO{sub 2} films for light to electrical energy conversion in regenerative photoelectrochemical cells with I{sup {minus}}/I{sub 2} acetonitrile electrolyte. The sensitizers have intense metal-to-ligand charge-transfer (MLCT) bands centered {approximately}380 and 535 mm that sensitize TiO{sub 2} over a notably broad spectral range. The photophysical and photoelectrochemical studies of these materials are contrasted with cis-Ru(dcbH{sub 2}){sub 2}(NCS){sub 2}, which is one of the most efficient sensitizers reported to date. Photophysical measurements show that the high photocurrent observed for cis-Ru(dcb){sub 2}(NCS){sub 2}TiO{sub 2} is due to efficient and rapid iodide oxidation.

  13. Effect of post-deposition treatment on energy conversion efficiency of nanostructured CdS/Cu2S thin films

    NASA Astrophysics Data System (ADS)

    Taur, Vidya S.; Joshi, Rajesh A.; Sharma, Ramphal

    2013-02-01

    In the present manuscript we report about synthesis of nanostructured CdS/Cu2S thin films by economically viable soft chemical route and effect of post deposition treatments such as annealing in air and swift heavy ion irradiation on solar energy conversion efficiency of the heterojunction device. These as grown, annealed and irradiated thin films are characterized for structural, morphological, optical and I-V properties. X-ray diffraction pattern (XRD) represents structural as well as crystallite modifications, atomic force microscopy (AFM) shows improvement in surface appearance of the materials. The solar energy conversion efficiency calculated from I-V exhibited increase in conversion efficiency i. e. 0.09, 0.24 and 0.48 % for as grown, annealed and SHI irradiated thin films.

  14. Conversion efficiency and spectral broadening of the K-{alpha} line emitted from planar titanium targets irradiated with ultra-short laser pulses of high intensity

    SciTech Connect

    Arora, V.; Singhal, H.; Naik, P. A.; Gupta, P. D.

    2011-10-15

    A study of the conversion efficiency and line shape of the K-{alpha} x-ray line radiation from a planar titanium target irradiated by an ultra-short laser pulse is performed. The conversion efficiency and spectral broadening are studied as a function of laser intensity (5 x 10{sup 16}-10{sup 18} W cm{sup -2}), laser pulse duration (45 fs-800 fs), and laser fluence (2 x 10{sup 3}-4.2 x 10{sup 4} J cm{sup -2}). The K-{alpha}{sub 1} line (4510 eV) is observed to be broadened (up to {approx}9 eV), predominantly towards the higher energy side and strongly depends on the laser fluence rather than on laser intensity. The reason for the spectral broadening is attributed to K-{alpha} emission in warm dense plasma. The role of hot electrons and direct laser heating on spectral broadening is outlined. In addition to this, our observations indicates that the presence of pre-plasma strongly contribute to the observed broadening through the inner-shell transitions in multiply charged titanium ions in the pre-plasma. The appropriate laser irradiation parameters to achieve high conversion efficiency and minimum spectral width of the K-{alpha} radiation are identified. The study is important, since the control of the spectral profile is of general interest for diffraction or scattering experiments in view of its potential in increasing temporal resolution.

  15. Integration of CdSe/CdSexTe1-x Type-II Heterojunction Nanorods into Hierarchically Porous TiO2 Electrode for Efficient Solar Energy Conversion

    NASA Astrophysics Data System (ADS)

    Lee, Sangheon; Flanagan, Joseph C.; Kang, Joonhyeon; Kim, Jinhyun; Shim, Moonsub; Park, Byungwoo

    2015-12-01

    Semiconductor sensitized solar cells, a promising candidate for next-generation photovoltaics, have seen notable progress using 0-D quantum dots as light harvesting materials. Integration of higher-dimensional nanostructures and their multi-composition variants into sensitized solar cells is, however, still not fully investigated despite their unique features potentially beneficial for improving performance. Herein, CdSe/CdSexTe1-x type-II heterojunction nanorods are utilized as novel light harvesters for sensitized solar cells for the first time. The CdSe/CdSexTe1-x heterojunction-nanorod sensitized solar cell exhibits ~33% improvement in the power conversion efficiency compared to its single-component counterpart, resulting from superior optoelectronic properties of the type-II heterostructure and 1-octanethiol ligands aiding facile electron extraction at the heterojunction nanorod-TiO2 interface. Additional ~32% enhancement in power conversion efficiency is achieved by introducing percolation channels of large pores in the mesoporous TiO2 electrode, which allow 1-D sensitizers to infiltrate the entire depth of electrode. These strategies combined together lead to 3.02% power conversion efficiency, which is one of the highest values among sensitized solar cells utilizing 1-D nanostructures as sensitizer materials.

  16. Integration of CdSe/CdSexTe1-x Type-II Heterojunction Nanorods into Hierarchically Porous TiO2 Electrode for Efficient Solar Energy Conversion.

    PubMed

    Lee, Sangheon; Flanagan, Joseph C; Kang, Joonhyeon; Kim, Jinhyun; Shim, Moonsub; Park, Byungwoo

    2015-01-01

    Semiconductor sensitized solar cells, a promising candidate for next-generation photovoltaics, have seen notable progress using 0-D quantum dots as light harvesting materials. Integration of higher-dimensional nanostructures and their multi-composition variants into sensitized solar cells is, however, still not fully investigated despite their unique features potentially beneficial for improving performance. Herein, CdSe/CdSe(x)Te(1-x) type-II heterojunction nanorods are utilized as novel light harvesters for sensitized solar cells for the first time. The CdSe/CdSe(x)Te(1-x) heterojunction-nanorod sensitized solar cell exhibits ~33% improvement in the power conversion efficiency compared to its single-component counterpart, resulting from superior optoelectronic properties of the type-II heterostructure and 1-octanethiol ligands aiding facile electron extraction at the heterojunction nanorod-TiO(2) interface. Additional ~32% enhancement in power conversion efficiency is achieved by introducing percolation channels of large pores in the mesoporous TiO(2) electrode, which allow 1-D sensitizers to infiltrate the entire depth of electrode. These strategies combined together lead to 3.02% power conversion efficiency, which is one of the highest values among sensitized solar cells utilizing 1-D nanostructures as sensitizer materials. PMID:26638994

  17. Investigation of Proton Focusing and Conversion Efficiency for Proton Fast Ignition

    NASA Astrophysics Data System (ADS)

    Bartal, Teresa Jean

    Recent advances in generating high energy (> 50 MeV) protons from intense laser-matter interactions has opened up new areas of research, with applications in radiography, high energy density physics, and ion-proton beam fast ignition (FI). The ability to focus the proton beam has made these applications more attractive. Fast ignition (FI) is an evolved concept of conventional inertial confinement fusion (ICF). In proton FI, a collimated beam of protons is used to deliver the necessary ignition energy to the compressed Deuterium-Tritium (DT) fuel capsule instead of the original concept of a beam composed of relativistic electrons. In cone-guided FI, a cone is embedded into the side of the fuel capsule where the proton source foil is placed within the cone. The cone provides a clear path to the dense core and protects the proton source foil from radiation during the compression of the capsule. The proton source foil is a segment of a hemispherical shell target used to help focus the proton beam to the core to spark ignition. The viability of proton FI requires focusing of the generated proton beam to a 40 mum spot at the compressed fuel and a laser to proton conversion efficiency of ˜15%. Here, proton focusing and the laser to proton conversion efficiency are investigated using flat foils and hemispherical shell targets. Experiments were conducted on the 200 TW short pulse laser at Los Alamos Laboratory. The 1053 nm laser pulse delivered 70--80 J on target in 500--600 fs focused by an f/8 parabolic mirror. The generated proton beam from the target was examined by placing a mesh downstream of the target, which the proton beam would pass though and then imaged with a pack of radiochromic film (RCF). A 3D ray-tracing technique was developed to determine the focal position and focal spot size of the generated proton beam by tracing the proton trajectories from the image of the mesh collected by the RCF back through the mesh to the central axis. The focal position

  18. Achievement-Relevant Personality: Relations with the Big Five and Validation of an Efficient Instrument.

    PubMed

    Briley, Daniel A; Domiteaux, Matthew; Tucker-Drob, Elliot M

    2014-05-01

    Many achievement-relevant personality measures (APMs) have been developed, but the interrelations among APMs or associations with the broader personality landscape are not well-known. In Study 1, 214 participants were measured on 36 APMs and a measure of the Big Five. Factor analytic results supported the convergent and discriminant validity of five latent dimensions: performance, mastery, self-doubt, effort, and intellectual investment. Conscientiousness, neuroticism, and openness to experience had the most consistent associations with APMs. We constructed a more efficient scale- the Multidimensional Achievement-Relevant Personality Scale (MAPS). In Study 2, we replicated the factor structure and external correlates of the MAPS in a sample of 359 individuals. Finally, we validated the MAPS with four indicators of academic performance and demonstrated incremental validity. PMID:24839374

  19. Achievement-Relevant Personality: Relations with the Big Five and Validation of an Efficient Instrument

    PubMed Central

    Briley, Daniel A.; Domiteaux, Matthew; Tucker-Drob, Elliot M.

    2014-01-01

    Many achievement-relevant personality measures (APMs) have been developed, but the interrelations among APMs or associations with the broader personality landscape are not well-known. In Study 1, 214 participants were measured on 36 APMs and a measure of the Big Five. Factor analytic results supported the convergent and discriminant validity of five latent dimensions: performance, mastery, self-doubt, effort, and intellectual investment. Conscientiousness, neuroticism, and openness to experience had the most consistent associations with APMs. We constructed a more efficient scale– the Multidimensional Achievement-Relevant Personality Scale (MAPS). In Study 2, we replicated the factor structure and external correlates of the MAPS in a sample of 359 individuals. Finally, we validated the MAPS with four indicators of academic performance and demonstrated incremental validity. PMID:24839374

  20. "I Tell Them I Know How to Do My ABCs!": Kindergartners' School-Related Conversations with Parents and Associations with Adjustment and Achievement

    ERIC Educational Resources Information Center

    Patrick, Helen; Johnson, Kiana R.; Mantzicopoulos, Panayota; Gray, DeLeon L.

    2011-01-01

    We examined kindergartners' (N = 160) reports of their conversations with parents about school, including whether parents ask about school, what parents ask about, what children tell them, and whether children want to tell their parents. We also investigated whether school adjustment and achievement were associated with either parent questions or…

  1. Quantitative Analysis of Defects in Silicon. [to predict energy conversion efficiency of silicon samples for solar cells

    NASA Technical Reports Server (NTRS)

    Natesh, R.; Smith, J. M.; Qidwai, H. A.; Bruce, T.

    1979-01-01

    The evaluation and prediction of the conversion efficiency for a variety of silicon samples with differences in structural defects, such as grain boundaries, twin boundaries, precipitate particles, dislocations, etc. are discussed. Quantitative characterization of these structural defects, which were revealed by etching the surface of silicon samples, is performed by using an image analyzer. Due to different crystal growth and fabrication techniques the various types of silicon contain a variety of trace impurity elements and structural defects. The two most important criteria in evaluating the various silicon types for solar cell applications are cost and conversion efficiency.

  2. Enhanced conversion efficiency in wide-bandgap GaNP solar cells

    SciTech Connect

    Sukrittanon, Supanee; Liu, Ren; Ro, Yun Goo; Pan, Janet L.; Jungjohann, Katherine Leigh; Tu, Charles W.; Dayeh, Shadi A.

    2015-10-12

    In this study, we demonstrate –2.05 eV dilute nitride GaNP solar cells on GaP substrates for potential use as the top junction in dual-junction integrated cells on Si. By adding a small amount of N into indirect-bandgap GaP, GaNP has several extremely important attributes: a direct-bandgap that is also tunable, and easily attained lattice-match with Si. Our best GaNP solar cell ([N] –1.8%, Eg –2.05 eV) achieves an efficiency of 7.9%, even in the absence of a window layer. This GaNP solar cell's efficiency is 3× higher than the most efficient GaP solar cell to date and higher than other solar cells with similar direct bandgap (InGaP, GaAsP). Through a systematic study of the structural, electrical, and optical properties of the device, efficient broadband optical absorption and enhanced solar cell performance are demonstrated.

  3. Enhanced conversion efficiency in wide-bandgap GaNP solar cells

    DOE PAGESBeta

    Sukrittanon, Supanee; Liu, Ren; Ro, Yun Goo; Pan, Janet L.; Jungjohann, Katherine Leigh; Tu, Charles W.; Dayeh, Shadi A.

    2015-10-12

    In this study, we demonstrate –2.05 eV dilute nitride GaNP solar cells on GaP substrates for potential use as the top junction in dual-junction integrated cells on Si. By adding a small amount of N into indirect-bandgap GaP, GaNP has several extremely important attributes: a direct-bandgap that is also tunable, and easily attained lattice-match with Si. Our best GaNP solar cell ([N] –1.8%, Eg –2.05 eV) achieves an efficiency of 7.9%, even in the absence of a window layer. This GaNP solar cell's efficiency is 3× higher than the most efficient GaP solar cell to date and higher than othermore » solar cells with similar direct bandgap (InGaP, GaAsP). Through a systematic study of the structural, electrical, and optical properties of the device, efficient broadband optical absorption and enhanced solar cell performance are demonstrated.« less

  4. THz generation at 1.55 µm excitation: six-fold increase in THz conversion efficiency by separated photoconductive and trapping regions.

    PubMed

    Dietz, Roman J B; Gerhard, Marina; Stanze, Dennis; Koch, Martin; Sartorius, Bernd; Schell, Martin

    2011-12-19

    We present first results on photoconductive THz emitters for 1.55µm excitation. The emitters are based on MBE grown In0.53Ga0.47As/In0.52Al0.48As multilayer heterostructures (MLHS) with high carrier mobility. The high mobility is achieved by spatial separation of photoconductive and trapping regions. Photoconductive antennas made of these MLHS are evaluated as THz emitters in a THz time domain spectrometer (THz TDS). The high carrier mobility and effective absorption significantly increases the optical-to-THz conversion efficiency with THz bandwidth in excess of 3 THz. PMID:22274179

  5. PowerSphere: A Novel Photovoltaic Cavity Converter Using Low Bandgap TPV Cells for Efficient Conversion of High Power Laser Beams to Electricity

    NASA Astrophysics Data System (ADS)

    Ortabasi, Ugur; Friedman, Herbert W.

    2004-11-01

    PowerSphere is a variant of the recently developed Photovoltaic Cavity Converter (PVCC) for High Concentration Photovoltaic applications. Both systems share the benefit of photon recycling in a cavity and have therefore the potential to convert high-density radiant power to electricity at unprecedented efficiencies. Unlike PVCC that is optimized for the full content of the solar spectrum, the PowerSphere is designed to convert the monochromatic beam of a laser efficiently to electricity. The PowerSphere concept introduced here greatly benefits from recent advances in the area of high power, near-IR lasers and advanced bandgap engineering involving `tunable' III-V cells operating in the same range of the spectrum. Given this new scenario the spectral response of such cells can be perfectly tuned to the frequency of a high power laser to achieve conversion efficiencies in excess of 60%. Other key phenomena that allow achieving such high conversion rates are described in the main text of this paper. PowerSphere concept when fully developed can greatly contribute to the advancement of Laser Power Beaming technology for terrestrial, near-space and space applications. The paper explores the performance potential of Laser Power Beaming (LPB) systems using a PowerSphere as a receiver and discusses some of the critical issues that require further studies in this promising area of `Wireless Power Transmission'.

  6. An alternative synthetic approach for efficient catalytic conversion of syngas to ethanol.

    PubMed

    Yue, Hairong; Ma, Xinbin; Gong, Jinlong

    2014-05-20

    Ethanol is an attractive end product and a versatile feedstock because a widespread market exists for its commercial use as a fuel additive or a potential substitute for gasoline. Currently, ethanol is produced primarily by fermentation of biomass-derived sugars, particularly those containing six carbons, but coproducts 5-carbon sugars and lignin remain unusable. Another major process for commercial production of ethanol is hydration of ethylene over solid acidic catalysts, yet not sustainable considering the depletion of fossil fuels. Catalytic conversion of synthetic gas (CO + H2) could produce ethanol in large quantities. However, the direct catalytic conversion of synthetic gas to ethanol remains challenging, and no commercial process exists as of today although the research has been ongoing for the past 90 years, since such the process suffers from low yield and poor selectivity due to slow kinetics of the initial C-C bond formation and fast chain growth of the C2 intermediates. This Account describes recent developments in an alternative approach for the synthesis of ethanol via synthetic gas. This process is an integrated technology consisting of the coupling of CO with methanol to form dimethyl oxalate and the subsequent hydrogenation to yield ethanol. The byproduct of the second step (methanol) can be separated and used in circulation as the feedstock for the coupling step. The coupling reaction of carbon monoxide for producing dimethyl oxalate takes place under moderate reaction conditions with high selectivity (∼95%), which ideally leads to a self-closing, nonwaste, catalytic cycling process. This Account also summarizes the progress on the development of copper-based catalysts for the hydrogenation reaction with remarkable efficiencies and stability. The unique lamellar structure and the cooperative effect between surface Cu(0) and Cu(+) species are responsible for the activity of the catalyst with high yield of ethanol (∼91%). The understanding of

  7. Ultra-broad band and dual-band highly efficient polarization conversion based on the three-layered chiral structure

    NASA Astrophysics Data System (ADS)

    Xu, Kai-kai; Xiao, Zhong-yin; Tang, Jing-yao; Liu, De-jun; Wang, Zi-hua

    2016-07-01

    In the paper, a novel three-layered chiral structure is proposed and investigated, which consists of a split-ring resonator sandwiched between two layers of sub-wavelength gratings. This designed structure can achieve simultaneously asymmetric transmission with an extremely broad bandwidth and high amplitude as well as multi-band 90° polarization rotator with very low dispersion. Numerical simulations adopted two kinds of softwares with different algorithms demonstrate that asymmetric parameter can reach a maximum of 0.99 and over than 0.8 from 4.6 to 16.8 GHz, which exhibit magnitude and bandwidth improvement over previous chiral metamaterials in microwave bands (S, C, X and Ku bands). Specifically, the reason of high amplitude is analyzed in detail based on the Fabry-perot like resonance. Subsequently, the highly efficient polarization conversion with very low dispersion between two orthogonal linearly polarized waves is also analyzed by the optical activity and ellipticity. Finally, the electric fields are also investigated and further demonstrate the correctness of the simulated and calculated results.

  8. Efficient method for the conversion of agricultural waste into sugar alcohols over supported bimetallic catalysts.

    PubMed

    Tathod, Anup P; Dhepe, Paresh L

    2015-02-01

    Promoter effect of Sn in the PtSn/γ-Al2O3 (AL) and PtSn/C bimetallic catalysts is studied for the conversion of variety of substrates such as, C5 sugars (xylose, arabinose), C6 sugars (glucose, fructose, galactose), hemicelluloses (xylan, arabinogalactan), inulin and agricultural wastes (bagasse, rice husk, wheat straw) into sugar alcohols (sorbitol, mannitol, xylitol, arabitol, galactitol). In all the reactions, PtSn/AL showed enhanced yields of sugar alcohols by 1.5-3 times than Pt/AL. Compared to C, AL supported bimetallic catalysts showed prominent enhancement in the yields of sugar alcohols. Bimetallic catalysts characterized by X-ray diffraction study revealed the stability of catalyst and absence of alloy formation thereby indicating that Pt and Sn are present as individual particles in PtSn/AL. The TEM analysis also confirmed stability of the catalysts and XPS study disclosed formation of electron deficient Sn species which helps in polarizing carbonyl bond to achieve enhanced hydrogenation activity. PMID:25453932

  9. [An effect enhancement mechanism of up-conversion luminescence--up-conversion sensitization].

    PubMed

    Meng, C; Meng, G; Song, Z

    2001-04-01

    The research of frequency up-conversion has been developed greatly in recent ten years. In order to achieve its applications, it needs to enhance the up-conversion efficiency further greatly, which is the core problem of up-conversion. Because of the specialty of Yb3+ ion energy level, Yb3+ can greatly enhance up-conversion luminescence of co-doped rare earth ion activator through energy transfer. Meanwhile it may not cause the obvious fluorescence quenching. Thus it is very significance to investigate up-conversion sensitization which Yb3+ ion acts as a sensitizer. It is more important that it is quite urgent to combine up-conversion efficiency and material property to develop up-conversion. This paper reviews the proposing and developing process of up-conversion sensitization. The achievement of up-conversion sensitization field especial the originate fruit in indirect up-conversion sensitization obtained by China are introduce emphatically. PMID:12947606

  10. Identifying the efficient inter-conversion between singlet and triplet charge-transfer states by magneto-electroluminescence study

    NASA Astrophysics Data System (ADS)

    Chen, Ping; Peng, Qiming; Yao, Liang; Gao, Na; Li, Feng

    2013-02-01

    Using the magneto-electroluminescence (MEL) as a tool, we demonstrated the efficient inter-conversion between singlet and triplet charge-transfer (CT) states in exciplex-based organic light-emitting diodes (OLEDs). Results show that the MEL of exciplex-based device is larger than that of exciton-based device by a factor of 3.2. The emission of exciplex-based devices comes from the direct intermolecular electron-hole pair recombination and their spin exchange energy is much smaller, which causes the efficient inter-conversion between singlet and triplet states. This argument was supported by the consistent evolutions of the MEL and EL spectra versus applied bias and donor concentrations. Finally, the bandgap effects on the MEL as well as the external quantum efficiency of exciplex-based devices were discussed. Our findings of MEL may offer a feasible way to unravel underlying mechanisms that limit the EL efficiency in the OLEDs.

  11. Modifying woody plants for efficient conversion to liquid and gaseous fuels

    SciTech Connect

    Dinus, R.J.; Dimmel, D.R.; Feirer, R.P.; Johnson, M.A.; Malcolm, E.W. )

    1990-07-01

    The Short Rotation Woody Crop Program (SRWCP), Department of Energy, is developing woody plant species as sources of renewable energy. Much progress has been made in identifying useful species, and testing site adaptability, stand densities, coppicing abilities, rotation lengths, and harvesting systems. Conventional plant breeding and intensive cultural practices have been used to increase above-ground biomass yields. Given these and foreseeable accomplishments, program leaders are now shifting attention to prospects for altering biomass physical and chemical characteristics, and to ways for improving the efficiency with which biomass can be converted to gaseous and liquid fuels. This report provides a review and synthesis of literature concerning the quantity and quality of such characteristics and constituents, and opportunities for manipulating them via conventional selection and breeding and/or molecular biology. Species now used by SRWCP are emphasized, with supporting information drawn from others as needed. Little information was found on silver maple (Acer saccharinum), but general comparisons (Isenberg 1981) suggest composition and behavior similar to those of the other species. Where possible, conclusions concerning means for and feasibility of manipulation are given, along with expected impacts on conversion efficiency. Information is also provided on relationships to other traits, genotype X environment interactions, and potential trade-offs or limitations. Biomass productivity per se is not addressed, except in terms of effects that may by caused by changes in constituent quality and/or quantity. Such effects are noted to the extent they are known or can be estimated. Likely impacts of changes, however effected, on suitability or other uses, e.g., pulp and paper manufacture, are notes. 311 refs., 4 figs., 9 tabs.

  12. In situ processed gold nanoparticle-embedded TiO2 nanofibers enabling plasmonic perovskite solar cells to exceed 14% conversion efficiency

    NASA Astrophysics Data System (ADS)

    Mali, Sawanta S.; Shim, Chang Su; Kim, Hyungjin; Patil, Pramod S.; Hong, Chang Kook

    2016-01-01

    We have demonstrated organometallic perovskite solar cells (PSCs) based on Au decorated TiO2 nanofibers and methylammonium lead iodide (MAPbI3). A power conversion efficiency of 14.92% was achieved, which is significantly higher than that of conventional mesoporous (mp) TiO2, as well as TiO2 nanofiber-based devices. The present synthetic process provides new opportunities for the development of efficient plasmonic PSCs based on metal oxide nanofibers. Solar cells based on these architectures exhibit a short-circuit current density JSC of 21.63 +/- 0.36 mA cm-2, VOC of 0.986 +/- 0.01 V and fill factor of 70% +/- 3%, which provide a power conversion efficiency of 14.92% +/- 0.33% under standard AM 1.5 conditions. The results of time-resolved photoluminescence (TRPL) spectroscopy and solid-state impedance spectroscopy (ssIS) revealed that PSCs based on Au-decorated TiO2 nanofibers exhibit a low recombination rate. The present results are much higher than those for reported PSCs based on a Au@TiO2 electron-transporting layer (ETL).We have demonstrated organometallic perovskite solar cells (PSCs) based on Au decorated TiO2 nanofibers and methylammonium lead iodide (MAPbI3). A power conversion efficiency of 14.92% was achieved, which is significantly higher than that of conventional mesoporous (mp) TiO2, as well as TiO2 nanofiber-based devices. The present synthetic process provides new opportunities for the development of efficient plasmonic PSCs based on metal oxide nanofibers. Solar cells based on these architectures exhibit a short-circuit current density JSC of 21.63 +/- 0.36 mA cm-2, VOC of 0.986 +/- 0.01 V and fill factor of 70% +/- 3%, which provide a power conversion efficiency of 14.92% +/- 0.33% under standard AM 1.5 conditions. The results of time-resolved photoluminescence (TRPL) spectroscopy and solid-state impedance spectroscopy (ssIS) revealed that PSCs based on Au-decorated TiO2 nanofibers exhibit a low recombination rate. The present results are much

  13. Glycoform-independent prion conversion by highly efficient, cell-based, protein misfolding cyclic amplification

    PubMed Central

    Moudjou, Mohammed; Chapuis, Jérôme; Mekrouti, Mériem; Reine, Fabienne; Herzog, Laetitia; Sibille, Pierre; Laude, Hubert; Vilette, Didier; Andréoletti, Olivier; Rezaei, Human; Dron, Michel; Béringue, Vincent

    2016-01-01

    Prions are formed of misfolded assemblies (PrPSc) of the variably N-glycosylated cellular prion protein (PrPC). In infected species, prions replicate by seeding the conversion and polymerization of host PrPC. Distinct prion strains can be recognized, exhibiting defined PrPSc biochemical properties such as the glycotype and specific biological traits. While strain information is encoded within the conformation of PrPSc assemblies, the storage of the structural information and the molecular requirements for self-perpetuation remain uncertain. Here, we investigated the specific role of PrPC glycosylation status. First, we developed an efficient protein misfolding cyclic amplification method using cells expressing the PrPC species of interest as substrate. Applying the technique to PrPC glycosylation mutants expressing cells revealed that neither PrPC nor PrPSc glycoform stoichiometry was instrumental to PrPSc formation and strainness perpetuation. Our study supports the view that strain properties, including PrPSc glycotype are enciphered within PrPSc structural backbone, not in the attached glycans. PMID:27384922

  14. Feasibility survey on international cooperation for high efficiency energy conversion technology in fiscal 1993

    NASA Astrophysics Data System (ADS)

    1994-03-01

    Following cooperative researches on fuel cell jointly conducted by NEDO and EGAT (Electricity Generating Authority of Thailand), the survey on international cooperation relating to high efficiency energy conversion technology was carried out for the ASEAN countries. The paper summed up the results of the survey. The study of the international cooperation is made for the following three items: a program for periodical exchange of information with EGAT, a project for cooperative research on phosphoric acid fuel cell in Indonesia, and a project for cooperative research with EGAT on electric power storage by advanced battery. In Malaysia, which is small in scale of state, part of the Ministry of Energy, Telecommunication and Posts is only in charge of the energy issue. Therefore, the situation is that they cannot answer well to many items of research/development cooperation brought in from Japan. The item of medium- and long-term developmental research in the Philippines is about the problems which are seen subsequently in the Manila metropolitan area where the problem of outage is being settled. Accordingly, it is essential to promote the cooperative research, well confirming policies and systems of the Ministry of Energy and the national electricity corporation.

  15. Designation of highly efficient catalysts for one pot conversion of glycerol to lactic acid

    NASA Astrophysics Data System (ADS)

    Tao, Meilin; Dan Zhang; Guan, Hongyu; Huang, Guohui; Wang, Xiaohong

    2016-07-01

    Production of lactic acid from glycerol is a cascade catalytic procedure using multifunctional catalysts combined with oxidative and acidic catalytic sites. Therefore, a series of silver-exchanged phosphomolybdic acid catalysts (AgxH3‑xPMo12O40, x = 1 ~ 3, abbreviated as AgxPMo) was designed and applied in glycerol oxidation with O2 as an oxidant to produce lactic acid (LA) without adding any base. Among all, total silver exchanged phosphomolybdic acid (Ag3PMo) was found to be the most active one with LA selectivity of 93% at 99% conversion under mild conditions of 5 h at 60 °C. The exceptionally high efficiency was contributed to the generation of strong Lewis acid sites, enhanced redox potentials and water-tolerance. More importantly, Ag3PMo was tolerant in crude glycerol from biodiesel production. And the reaction mechanism was also discussed. Meanwhile, Ag3PMo acted as a heterogeneous catalyst for 12 recycles without loss of activity.

  16. Designation of highly efficient catalysts for one pot conversion of glycerol to lactic acid.

    PubMed

    Tao, Meilin; Dan Zhang; Guan, Hongyu; Huang, Guohui; Wang, Xiaohong

    2016-01-01

    Production of lactic acid from glycerol is a cascade catalytic procedure using multifunctional catalysts combined with oxidative and acidic catalytic sites. Therefore, a series of silver-exchanged phosphomolybdic acid catalysts (AgxH3-xPMo12O40, x = 1 ~ 3, abbreviated as AgxPMo) was designed and applied in glycerol oxidation with O2 as an oxidant to produce lactic acid (LA) without adding any base. Among all, total silver exchanged phosphomolybdic acid (Ag3PMo) was found to be the most active one with LA selectivity of 93% at 99% conversion under mild conditions of 5 h at 60 °C. The exceptionally high efficiency was contributed to the generation of strong Lewis acid sites, enhanced redox potentials and water-tolerance. More importantly, Ag3PMo was tolerant in crude glycerol from biodiesel production. And the reaction mechanism was also discussed. Meanwhile, Ag3PMo acted as a heterogeneous catalyst for 12 recycles without loss of activity. PMID:27431610

  17. Restructuring fundamental predator-prey models by recognising prey-dependent conversion efficiency and mortality rates.

    PubMed

    Li, Jiqiu; Montagnes, David J S

    2015-05-01

    Incorporating protozoa into population models (from simple predator-prey explorations to complex food web simulations) is of conceptual, ecological, and economic importance. From theoretical and empirical perspectives, we expose unappreciated complexity in the traditional predator-prey model structure and provide a parsimonious solution, especially for protistologists. We focus on how prey abundance alters two key components of models: predator conversion efficiency (e, the proportion of prey converted to predator, before mortality loss) and predator mortality (δ, the portion of the population lost though death). Using a well-established model system (Paramecium and Didinium), we collect data to parameterize a range of existing and novel population models that differ in the functional forms of e and δ. We then compare model simulations to an empirically obtained time-series of predator-prey population dynamics. The analysis indicates that prey-dependent e and δ should be considered when structuring population models and that both prey and predator biomass also vary with prey abundance. Both of these impact the ability of the model to predict population dynamics and, therefore, should be included in theoretical model evaluations and assessment of ecosystem dynamics associated with biomass flux. PMID:25819465

  18. Designation of highly efficient catalysts for one pot conversion of glycerol to lactic acid

    PubMed Central

    Tao, Meilin; Dan Zhang; Guan, Hongyu; Huang, Guohui; Wang, Xiaohong

    2016-01-01

    Production of lactic acid from glycerol is a cascade catalytic procedure using multifunctional catalysts combined with oxidative and acidic catalytic sites. Therefore, a series of silver-exchanged phosphomolybdic acid catalysts (AgxH3−xPMo12O40, x = 1 ~ 3, abbreviated as AgxPMo) was designed and applied in glycerol oxidation with O2 as an oxidant to produce lactic acid (LA) without adding any base. Among all, total silver exchanged phosphomolybdic acid (Ag3PMo) was found to be the most active one with LA selectivity of 93% at 99% conversion under mild conditions of 5 h at 60 °C. The exceptionally high efficiency was contributed to the generation of strong Lewis acid sites, enhanced redox potentials and water-tolerance. More importantly, Ag3PMo was tolerant in crude glycerol from biodiesel production. And the reaction mechanism was also discussed. Meanwhile, Ag3PMo acted as a heterogeneous catalyst for 12 recycles without loss of activity. PMID:27431610

  19. Protonation process of conjugated polyelectrolytes on enhanced power conversion efficiency in the inverted polymer solar cells

    NASA Astrophysics Data System (ADS)

    Yi, Chao; Hu, Rong; Ren, He; Hu, Xiaowen; Wang, Shu; Gong, Xiong; Cao, Yong

    2014-01-01

    In this study, two conjugated polyelectrolytes, polythiophene derivative (PTP) and poly[(9,9-bis [6‧-N, N, N-trimethylammonium] hexyl)-fluorenylene-phenylene] dibromide (PFP), are utilized to modify the surface properties of ZnO electron extraction layer (EEL) in the inverted polymer solar cells (PSCs). Both higher short-circuit current densities and larger open-circuit voltages were observed from the inverted PSCs with ZnO/PFP or ZnO/PTP as compared with those only with ZnO EEL. The protonation process for PTP and PFP in solution is distinguished. Overall, more than 40% enhanced power conversion efficiency (PCE) from the inverted PSCs with ZnO/PFP, in which the PFP could be fully ionized in deionized water, and more than 30% enhanced PCE from the inverted PSCs with ZnO/PTP, as the case that the PTP could not be fully ionized in deionized water, as compared with the inverted PSCs with ZnO EEL were observed, respectively. These results demonstrate that the conjugated polyelectrolytes play an important role in enhancement of device performance of inverted PSCs and that the protonation process of the conjugated polyelectrolytes is critical to the modification for EEL in PSCs.

  20. Glycoform-independent prion conversion by highly efficient, cell-based, protein misfolding cyclic amplification.

    PubMed

    Moudjou, Mohammed; Chapuis, Jérôme; Mekrouti, Mériem; Reine, Fabienne; Herzog, Laetitia; Sibille, Pierre; Laude, Hubert; Vilette, Didier; Andréoletti, Olivier; Rezaei, Human; Dron, Michel; Béringue, Vincent

    2016-01-01

    Prions are formed of misfolded assemblies (PrP(Sc)) of the variably N-glycosylated cellular prion protein (PrP(C)). In infected species, prions replicate by seeding the conversion and polymerization of host PrP(C). Distinct prion strains can be recognized, exhibiting defined PrP(Sc) biochemical properties such as the glycotype and specific biological traits. While strain information is encoded within the conformation of PrP(Sc) assemblies, the storage of the structural information and the molecular requirements for self-perpetuation remain uncertain. Here, we investigated the specific role of PrP(C) glycosylation status. First, we developed an efficient protein misfolding cyclic amplification method using cells expressing the PrP(C) species of interest as substrate. Applying the technique to PrP(C) glycosylation mutants expressing cells revealed that neither PrP(C) nor PrP(Sc) glycoform stoichiometry was instrumental to PrP(Sc) formation and strainness perpetuation. Our study supports the view that strain properties, including PrP(Sc) glycotype are enciphered within PrP(Sc) structural backbone, not in the attached glycans. PMID:27384922

  1. Multiscaled hierarchical nanostructures for enhancing the conversion efficiency of crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Bingfa; Qiu, Shenyu; Hu, Ruiyi; Liao, Yuanbin; Chen, Nan; Du, Guoping

    2012-10-01

    High-performance antireflection structure is critical for enhancing the conversion efficiency of solar cells. One of the most effective antireflection techniques for solar cells is the introduction of nanostructures to the cells. In this work, we prepared multiscaled hierarchical Er-doped ZnO nanostructures on the plasma enhanced chemical vapor deposited silicon nitride-coated texturized single crystalline silicon solar cells for antireflection. The multiscaled hierarchical Er-doped ZnO nanostructures were needle-like nanotip arrays, and they were grown using the hydrothermal method. The dependence of microstructure and antireflection performance of the multiscaled hierarchical Er-doped ZnO nanostructures on the growth time were studied. It was shown that longer growth time resulted in greater length and diameter for the Er-doped ZnO nanostructures. For longer growth time, the needle-like tips of the multiscaled hierarchical Er-doped ZnO nanostructures were found to transform to flat tops, which greatly degraded their antireflection performance. An optimal growth time for the multiscaled hierarchical Er-doped ZnO nanostructures was determined, and a large enhancement in the photovoltaic performance of sc-Si solar cells was resulted.

  2. X-ray conversion efficiency in vacuum hohlraum experiments at the National Ignition Facility

    SciTech Connect

    Olson, R. E.; Suter, L. J.; Callahan, D. A.; Rosen, M. D.; Dixit, S. N.; Landen, O. L.; Meezan, N. B.; Moody, J. D.; Thomas, C. A.; Warrick, A.; Widmann, K.; Williams, E. A.; Glenzer, S. H.; Kline, J. L.

    2012-05-15

    X-ray fluxes measured in the first 96 and 192 beam vacuum hohlraum experiments at the National Ignition Facility (NIF) were significantly higher than predicted by computational simulations employing XSN average atom atomic physics and highly flux-limited electron heat conduction. For agreement with experimental data, it was found that the coronal plasma emissivity must be simulated with a detailed configuration accounting model that accounts for x-ray emission involving all of the significant ionization states. It was also found that an electron heat conduction flux limit of f= 0.05 is too restrictive, and that a flux limit of f= 0.15 results in a much better match with the NIF vacuum hohlraum experimental data. The combination of increased plasma emissivity and increased electron heat conduction in this new high flux hohlraum model results in a reduction in coronal plasma energy and, hence, an explanation for the high ({approx}85%-90%) x-ray conversion efficiencies observed in the 235 < T{sub r} < 345 eV NIF vacuum hohlraum experiments.

  3. Efficient frequency conversion by stimulated Raman scattering in a sodium nitrate aqueous solution

    SciTech Connect

    Ganot, Yuval E-mail: ibar@bgu.ac.il; Bar, Ilana E-mail: ibar@bgu.ac.il

    2015-09-28

    Frequency conversion of laser beams, based on stimulated Raman scattering (SRS) is an appealing technique for generating radiation at new wavelengths. Here, we investigated experimentally the SRS due to a single pass of a collimated frequency-doubled Nd:YAG laser beam (532 nm) through a saturated aqueous solution of sodium nitrate (NaNO{sub 3}), filling a 50 cm long cell. These experiments resulted in simultaneous generation of 1st (564 nm) and 2nd (599 nm) Stokes beams, corresponding to the symmetric stretching mode of the nitrate ion, ν{sub 1}(NO{sub 3}{sup −}), with 40 and 12 mJ/pulse maximal converted energies, equivalent to 12% and 4% efficiencies, respectively, for a 340 mJ/pulse pump energy. The results indicate that the pump and SRS beams were thermally defocused and that four-wave mixing was responsible for the second order Stokes process onset.

  4. Efficient conversion of myricetin from Ampelopsis grossedentata extracts and its purification by MIP-SPE.

    PubMed

    Zhong, Shian; Kong, Yanyue; Zhou, Ling; Zhou, Chengyun; Zhang, Xiaona; Wang, Yan

    2014-01-15

    In this study, we developed an efficient conversion process of dihydromyricetin to myricetin from Ampelopsis grossedentata extracts. The content of myricetin increased from 2.38% to 85.57%, demonstrating the successful dehydrogenation of dihydromyricetin. Molecularly imprinted polymers (MIPs) were prepared by surface imprinting method using silica microspheres as the support matrices and myricetin as template. The MIPs were applied for the selective adsorption of myricetin. The chemical structure of the MIPs was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Static, dynamic and selective adsorption experiments showed that the MIPs exhibited good adsorption ability, rather fast template rebinding kinetics, and appreciate selectivity over structurally related compounds. Accordingly, the MIPs were applied as the selective sorbent in SPE to purify myricetin obtained through dehydrogenation, followed by HPLC-UV analysis. The recoveries of myricetin and dihydromyricetin were 92.7% and 55.6%, respectively. This study demonstrates the feasibility of using the developed MIP-SPE method to purify and enrich myricetin in the natural products. PMID:24321759

  5. The genetics of feed conversion efficiency traits in a commercial broiler line

    PubMed Central

    Reyer, Henry; Hawken, Rachel; Murani, Eduard; Ponsuksili, Siriluck; Wimmers, Klaus

    2015-01-01

    Individual feed conversion efficiency (FCE) is a major trait that influences the usage of energy resources and the ecological footprint of livestock production. The underlying biological processes of FCE are complex and are influenced by factors as diverse as climate, feed properties, gut microbiota, and individual genetic predisposition. To gain an insight to the genetic relationships with FCE traits and to contribute to the improvement of FCE in commercial chicken lines, a genome-wide association study was conducted using a commercial broiler population (n = 859) tested for FCE and weight traits during the finisher period from 39 to 46 days of age. Both single-marker (generalized linear model) and multi-marker (Bayesian approach) analyses were applied to the dataset to detect genes associated with the variability in FCE. The separate analyses revealed 22 quantitative trait loci (QTL) regions on 13 different chromosomes; the integration of both approaches resulted in 7 overlapping QTL regions. The analyses pointed to acylglycerol kinase (AGK) and general transcription factor 2-I (GTF2I) as positional and functional candidate genes. Non-synonymous polymorphisms of both candidate genes revealed evidence for a functional importance of these genes by influencing different biological aspects of FCE. PMID:26552583

  6. Nanoparticle-Loaded Protein-Polymer Nanodroplets for Improved Stability and Conversion Efficiency in Ultrasound Imaging and Drug Delivery.

    PubMed

    Lee, Jeong Yu; Carugo, Dario; Crake, Calum; Owen, Joshua; de Saint Victor, Marie; Seth, Anjali; Coussios, Constantin; Stride, Eleanor

    2015-10-01

    A new formulation of volatile nanodroplets stabilized by a protein and polymer coating and loaded with magnetic nanoparticles is developed. The droplets show enhanced stability and phase conversion efficiency upon ultrasound exposure compared with existing formulations. Magnetic targeting, encapsulation, and release of an anticancer drug are demonstrated in vitro with a 40% improvement in cytotoxicity compared with free drug. PMID:26265592

  7. Highly efficient conversion of biomass-derived glycolide to ethylene glycol over CuO in water.

    PubMed

    Xu, Lingli; Huo, Zhibao; Fu, Jun; Jin, Fangming

    2014-06-01

    The efficient conversion of biomass-derived glycolide into ethylene glycol over CuO in water was investigated. The reaction of glycolide was carried out with 25 mmol Zn and 6 mmol CuO with 25% water filling at 250 °C for 150 min, which yielded the desired ethylene glycol in 94% yield. PMID:24769741

  8. Photosynthetic energy conversion efficiency: setting a baseline for gauging future improvements in important food and biofuel crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The conversion efficiency (RUE) of absorbed radiation into biomass (MJ dry matter per MJ absorbed photosynthetically active radiation) is a component of yield potential that has been estimated at less than half the theoretical maximum. Various strategies have been proposed to improve RUE, but a stat...

  9. Bremsstrahlung and K(alpha) fluorescence measurements for inferring conversion efficiencies into fast ignition relevant hot electrons

    SciTech Connect

    Chen, C D; Patel, P K; Hey, D S; Mackinnon, A J; Key, M H; Akli, K U; Bartal, T; Beg, F N; Chawla, S; Chen, H; Freeman, R R; Higginson, D P; Link, A; Ma, T Y; MacPhee, A G; Stephens, R B; Van Woerkom, L D; Westover, B; Porkolab, M

    2009-07-24

    The Bremsstrahlung and K-shell emission from 1 mm x 1 mm x 1 mm planar targets irradiated by a short-pulse 3 x 10{sup 18}-8 x 10{sup 19} W/cm{sup 2} laser were measured. The Bremsstrahlung was measured using a filter stack spectrometer with spectral discrimination up to 500 keV. K-shell emission was measured using a single photon counting charge coupled device (CCD). From Monte Carlo modeling of the target emission, conversion efficiencies into 1-3 MeV electrons of 3-12%, representing 20-40% total conversion efficiencies were inferred for intensities up to 8 x 10{sup 19} W/cm{sup 2}. Comparisons to scaling laws using synthetic energy spectra generated from the intensity distribution of the focal spot imply slope temperatures less than the ponderomotive potential of the laser. Resistive transport effects may result in potentials of a few hundred kV in the first few tens of microns in the target. This would lead to higher total conversion efficiencies than inferred from Monte Carlo modeling but lower conversion efficiencies into 1-3 MeV electrons.

  10. Effects of beam quality of XeCl excimer laser on Raman conversion efficiency in H/sub 2/ *

    SciTech Connect

    Lou Qihong; Huo Yunshen; Dong Jinxing; Ding Zean; Wei Yunrong; Ding Aizhen; Gao Hongyi

    1988-10-01

    Stimulated Raman scattering (SRS) characteristics in high pressure H/sub 2/ are evaluated for pumping lasers with stable, plane-parallel and unstable laser resonators. By using a ring aperture to select the part of the laser beam with the best beam quality, Raman photon conversion efficiency of more than 90% was obtained with a pumping energy of 40 mJ.

  11. NASA-OAST/JPL high efficiency thermionic conversion studies. [nuclear electric propulsion

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Efforts were made to develop a thermionic energy conversion TEC technology appropriate for nuclear electric propulsion missions. This space TEC effort was complementary to the terrestrial TEC studies sponsored by the Department of Energy which had the goal of topping fossil fuel power plants. Thermionic energy conversion was a primary conversion option for space reactors because of its: (1) high operating temperature; (2) lack of moving parts; (3) modularity; (4) established technology; and (5) development potential.

  12. Enhanced conversion efficiency of dye-sensitized solar cells using a CNT-incorporated TiO2 slurry-based photoanode

    NASA Astrophysics Data System (ADS)

    Cai, Jiaoping; Chen, Zexiang; Li, Jun; Wang, Yan; Xiang, Dong; Zhang, Jijun; Li, Hai

    2015-02-01

    A new titanium dioxide (TiO2) slurry formulation is herein reported for the fabrication of TiO2 photoanode for use in dye-sensitized solar cells (DSSCs). The prepared TiO2 photoanode featured a highly uniform mesoporous structure with well-dispersed TiO2 nanoparticles. The energy conversion efficiency of the resulting TiO2 slurry-based DSSC was ˜63% higher than that achieved by a DSSC prepared using a commercial TiO2 slurry. Subsequently, the incorporation of acid-treated multi-walled carbon nanotubes (CNTs) into the TiO2 slurry was examined. More specifically, the effect of varying the concentration of the CNTs in this slurry on the performance of the resulting DSSCs was studied. The chemical state of the CNTs-incorporated TiO2 photoanode was investigated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A high energy conversion efficiency of 6.23% was obtained at an optimum CNT concentration of ˜0.06 wt.%. The obtained efficiency corresponds to a 63% enhancement when compared with that obtained from a DSSC based on a commercial TiO2 slurry. The higher efficiency was attributed to the improvement in the collection and transport of excited electrons in the presence of the CNTs.

  13. Enhanced conversion efficiency of dye-sensitized solar cells using a CNT-incorporated TiO{sub 2} slurry-based photoanode

    SciTech Connect

    Cai, Jiaoping; Chen, Zexiang Li, Jun; Wang, Yan Zhang, Jijun; Li, Hai; Xiang, Dong

    2015-02-15

    A new titanium dioxide (TiO{sub 2}) slurry formulation is herein reported for the fabrication of TiO{sub 2} photoanode for use in dye-sensitized solar cells (DSSCs). The prepared TiO{sub 2} photoanode featured a highly uniform mesoporous structure with well-dispersed TiO{sub 2} nanoparticles. The energy conversion efficiency of the resulting TiO{sub 2} slurry-based DSSC was ∼63% higher than that achieved by a DSSC prepared using a commercial TiO{sub 2} slurry. Subsequently, the incorporation of acid-treated multi-walled carbon nanotubes (CNTs) into the TiO{sub 2} slurry was examined. More specifically, the effect of varying the concentration of the CNTs in this slurry on the performance of the resulting DSSCs was studied. The chemical state of the CNTs-incorporated TiO{sub 2} photoanode was investigated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A high energy conversion efficiency of 6.23% was obtained at an optimum CNT concentration of ∼0.06 wt.%. The obtained efficiency corresponds to a 63% enhancement when compared with that obtained from a DSSC based on a commercial TiO{sub 2} slurry. The higher efficiency was attributed to the improvement in the collection and transport of excited electrons in the presence of the CNTs.

  14. Enhanced energy conversion efficiency from high strength synthetic organic wastewater by sequential dark fermentative hydrogen production and algal lipid accumulation.

    PubMed

    Ren, Hong-Yu; Liu, Bing-Feng; Kong, Fanying; Zhao, Lei; Xing, Defeng; Ren, Nan-Qi

    2014-04-01

    A two-stage process of sequential dark fermentative hydrogen production and microalgal cultivation was applied to enhance the energy conversion efficiency from high strength synthetic organic wastewater. Ethanol fermentation bacterium Ethanoligenens harbinense B49 was used as hydrogen producer, and the energy conversion efficiency and chemical oxygen demand (COD) removal efficiency reached 18.6% and 28.3% in dark fermentation. Acetate was the main soluble product in dark fermentative effluent, which was further utilized by microalga Scenedesmus sp. R-16. The final algal biomass concentration reached 1.98gL(-1), and the algal biomass was rich in lipid (40.9%) and low in protein (23.3%) and carbohydrate (11.9%). Compared with single dark fermentation stage, the energy conversion efficiency and COD removal efficiency of two-stage system remarkably increased 101% and 131%, respectively. This research provides a new approach for efficient energy production and wastewater treatment using a two-stage process combining dark fermentation and algal cultivation. PMID:24582427

  15. Design of hybrid nanoheterostructure systems for enhanced quantum and solar conversion efficiencies in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Kılıç, Bayram; Telli, Hakan; Tüzemen, Sebahattin; Başaran, Ali; Pirge, Gursev

    2015-04-01

    Dye sensitized solar cells (DSSCs) with an innovative design involving controlled-morphology vertically aligned (VA) ZnO nanowires within mesoporous TiO2 structures with ultrahigh surface area for implementation as photoanodes are herein reported. Although TiO2 nanostructures exhibit excellent power conversion efficiency, the electron transport rate is low owing to low electron mobility. To overcome this, ZnO nanowires with high electron mobility have been investigated as potential candidates for photoanodes. However, the power conversion efficiency of ZnO nanowires is still lower than that of TiO2 owing to their low internal surface area. Consequently, in this work, vertical growth of ZnO nanowires within mesoporous TiO2 structures is carried out to increase their solar power conversion efficiency. The photovoltaic performance of solar cells using ZnO nanowires, mesoporous TiO2, and TiO2/ZnO hybrid structures are compared. The VA TiO2/ZnO hybrid structures are found to provide direct electron transfer compared with the tortuous pathway of zero-dimensional nanostructures, resulting in an increased conversion efficiency. It is demonstrated that the light scattering of the photoanode film is increased and electron recombination is decreased when an appropriate amount of mesoporous TiO2 is used as a substrate for ZnO nanowires. The DSSC fabricated with the TiO2/ZnO hybrid photoanode prepared with 15.8 wt. % TiO2 showed the highest conversion efficiency of 7.30%, approximately 5%, 18%, and 40% higher than that of DSSCs fabricated with 3.99 wt. % TiO2, pure TiO2, and pure ZnO photoanodes, respectively.

  16. Design of hybrid nanoheterostructure systems for enhanced quantum and solar conversion efficiencies in dye-sensitized solar cells

    SciTech Connect

    Kılıç, Bayram E-mail: kbayramkilic@gmail.com; Telli, Hakan; Başaran, Ali; Pirge, Gursev; Tüzemen, Sebahattin

    2015-04-07

    Dye sensitized solar cells (DSSCs) with an innovative design involving controlled-morphology vertically aligned (VA) ZnO nanowires within mesoporous TiO{sub 2} structures with ultrahigh surface area for implementation as photoanodes are herein reported. Although TiO{sub 2} nanostructures exhibit excellent power conversion efficiency, the electron transport rate is low owing to low electron mobility. To overcome this, ZnO nanowires with high electron mobility have been investigated as potential candidates for photoanodes. However, the power conversion efficiency of ZnO nanowires is still lower than that of TiO{sub 2} owing to their low internal surface area. Consequently, in this work, vertical growth of ZnO nanowires within mesoporous TiO{sub 2} structures is carried out to increase their solar power conversion efficiency. The photovoltaic performance of solar cells using ZnO nanowires, mesoporous TiO{sub 2}, and TiO{sub 2}/ZnO hybrid structures are compared. The VA TiO{sub 2}/ZnO hybrid structures are found to provide direct electron transfer compared with the tortuous pathway of zero-dimensional nanostructures, resulting in an increased conversion efficiency. It is demonstrated that the light scattering of the photoanode film is increased and electron recombination is decreased when an appropriate amount of mesoporous TiO{sub 2} is used as a substrate for ZnO nanowires. The DSSC fabricated with the TiO{sub 2}/ZnO hybrid photoanode prepared with 15.8 wt. % TiO{sub 2} showed the highest conversion efficiency of 7.30%, approximately 5%, 18%, and 40% higher than that of DSSCs fabricated with 3.99 wt. % TiO{sub 2}, pure TiO{sub 2}, and pure ZnO photoanodes, respectively.

  17. Tunneling-injection in vertical quasi-2D heterojunctions enabled efficient and adjustable optoelectronic conversion

    PubMed Central

    Tan, Wei-Chun; Chiang, Chia-Wei; Hofmann, Mario; Chen, Yang-Fang

    2016-01-01

    The advent of 2D materials integration has enabled novel heterojunctions where carrier transport proceeds thrsough different ultrathin layers. We here demonstrate the potential of such heterojunctions on a graphene/dielectric/semiconductor vertical stack that combines several enabling features for optoelectronic devices. Efficient and stable light emission was achieved through carrier tunneling from the graphene injector into prominent states of a luminescent material. Graphene’s unique properties enable fine control of the band alignment in the heterojunction. This advantage was used to produce vertical tunneling-injection light-emitting transistors (VtiLET) where gating allows adjustment of the light emission intensity independent of applied bias. This device was shown to simultaneously act as a light detecting transistor with a linear and gate tunable sensitivity. The presented development of an electronically controllable multifunctional light emitter, light detector and transistor open up a new route for future optoelectronics. PMID:27507171

  18. Tunneling-injection in vertical quasi-2D heterojunctions enabled efficient and adjustable optoelectronic conversion.

    PubMed

    Tan, Wei-Chun; Chiang, Chia-Wei; Hofmann, Mario; Chen, Yang-Fang

    2016-01-01

    The advent of 2D materials integration has enabled novel heterojunctions where carrier transport proceeds thrsough different ultrathin layers. We here demonstrate the potential of such heterojunctions on a graphene/dielectric/semiconductor vertical stack that combines several enabling features for optoelectronic devices. Efficient and stable light emission was achieved through carrier tunneling from the graphene injector into prominent states of a luminescent material. Graphene's unique properties enable fine control of the band alignment in the heterojunction. This advantage was used to produce vertical tunneling-injection light-emitting transistors (VtiLET) where gating allows adjustment of the light emission intensity independent of applied bias. This device was shown to simultaneously act as a light detecting transistor with a linear and gate tunable sensitivity. The presented development of an electronically controllable multifunctional light emitter, light detector and transistor open up a new route for future optoelectronics. PMID:27507171

  19. Tunneling-injection in vertical quasi-2D heterojunctions enabled efficient and adjustable optoelectronic conversion

    NASA Astrophysics Data System (ADS)

    Tan, Wei-Chun; Chiang, Chia-Wei; Hofmann, Mario; Chen, Yang-Fang

    2016-08-01

    The advent of 2D materials integration has enabled novel heterojunctions where carrier transport proceeds thrsough different ultrathin layers. We here demonstrate the potential of such heterojunctions on a graphene/dielectric/semiconductor vertical stack that combines several enabling features for optoelectronic devices. Efficient and stable light emission was achieved through carrier tunneling from the graphene injector into prominent states of a luminescent material. Graphene’s unique properties enable fine control of the band alignment in the heterojunction. This advantage was used to produce vertical tunneling-injection light-emitting transistors (VtiLET) where gating allows adjustment of the light emission intensity independent of applied bias. This device was shown to simultaneously act as a light detecting transistor with a linear and gate tunable sensitivity. The presented development of an electronically controllable multifunctional light emitter, light detector and transistor open up a new route for future optoelectronics.

  20. Demonstration of efficient full aperture Type I/Type II third harmonic conversion on Nova

    SciTech Connect

    Wegner, P.J.; Henesian, M.A.; Marchi, F.T.; Speck, D.R.

    1987-11-19

    Type I/Type II third harmonic conversion has been implemented at the 74 cm aperture of the Nova laser system. We discuss the performance capabilities and alignment issues of this scheme for Nova relative to conventional Type II/Type II conversion. 3 refs., 2 figs.

  1. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 5: Combined gas-steam turbine cycles. [energy conversion efficiency in electric power plants

    NASA Technical Reports Server (NTRS)

    Amos, D. J.; Foster-Pegg, R. W.; Lee, R. M.

    1976-01-01

    The energy conversion efficiency of gas-steam turbine cycles was investigated for selected combined cycle power plants. Results indicate that it is possible for combined cycle gas-steam turbine power plants to have efficiencies several point higher than conventional steam plants. Induction of low pressure steam into the steam turbine is shown to improve the plant efficiency. Post firing of the boiler of a high temperature combined cycle plant is found to increase net power but to worsen efficiency. A gas turbine pressure ratio of 12 to 1 was found to be close to optimum at all gas turbine inlet temperatures that were studied. The coal using combined cycle plant with an integrated low-Btu gasifier was calculated to have a plant efficiency of 43.6%, a capitalization of $497/kW, and a cost of electricity of 6.75 mills/MJ (24.3 mills/kwh). This combined cycle plant should be considered for base load power generation.

  2. Efficient fluoride-catalyzed conversion of CO2 to CO at room temperature.

    PubMed

    Lescot, Camille; Nielsen, Dennis U; Makarov, Ilya S; Lindhardt, Anders T; Daasbjerg, Kim; Skrydstrup, Troels

    2014-04-23

    A protocol for the efficient and selective reduction of carbon dioxide to carbon monoxide has been developed. Remarkably, this oxygen abstraction step can be performed with only the presence of catalytic cesium fluoride and a stoichiometric amount of a disilane in DMSO at room temperature. Rapid reduction of CO2 to CO could be achieved in only 2 h, which was observed by pressure measurements. To quantify the amount of CO produced, the reduction was coupled to an aminocarbonylation reaction using the two-chamber system, COware. The reduction was not limited to a specific disilane, since (Ph2MeSi)2 as well as (PhMe2Si)2 and (Me3Si)3SiH exhibited similar reactivity. Moreover, at a slightly elevated temperature, other fluoride salts were able to efficiently catalyze the CO2 to CO reduction. Employing a nonhygroscopic fluoride source, KHF2, omitted the need for an inert atmosphere. Substituting the disilane with silylborane, (pinacolato)BSiMe2Ph, maintained the high activity of the system, whereas the structurally related bis(pinacolato)diboron could not be activated with this fluoride methodology. Furthermore, this chemistry could be adapted to (13)C-isotope labeling of six pharmaceutically relevant compounds starting from Ba(13)CO3 in a newly developed three-chamber system. PMID:24702475

  3. A theoretical analysis of the current-voltage characteristics of solar cells. [and their energy conversion efficiency

    NASA Technical Reports Server (NTRS)

    Dunbar, P. M.; Hauser, J. R.

    1976-01-01

    Various mechanisms which limit the conversion efficiency of silicon solar cells were studied. The effects of changes in solar cell geometry such as layer thickness on performance were examined. The effects of various antireflecting layers were also examined. It was found that any single film antireflecting layer results in a significant surface loss of photons. The use of surface texturing techniques or low loss antireflecting layers can enhance by several percentage points the conversion efficiency of silicon cells. The basic differences between n(+)-p-p(+) and p(+)-n-n(+) cells are treated. A significant part of the study was devoted to the importance of surface region lifetime and heavy doping effects on efficiency. Heavy doping bandgap reduction effects are enhanced by low surface layer lifetimes, and conversely, the reduction in solar cell efficiency due to low surface layer lifetime is further enhanced by heavy doping effects. A series of computer studies is reported which seeks to determine the best cell structure and doping levels for maximum efficiency.

  4. Systematic investigation of self-absorption and conversion efficiency of 6.7 nm extreme ultraviolet sources

    SciTech Connect

    Otsuka, Takamitsu; Higashiguchi, Takeshi; Yugami, Noboru; Yatagai, Toyohiko; Kilbane, Deirdre; Dunne, Padraig; O'Sullivan, Gerry; Jiang, Weihua; Endo, Akira

    2010-12-06

    We have investigated the dependence of the spectral behavior and conversion efficiencies of rare-earth plasma extreme ultraviolet sources with peak emission at 6.7 nm on laser wavelength and the initial target density. The maximum conversion efficiency was 1.3% at a laser intensity of 1.6x10{sup 12} W/cm{sup 2} at an operating wavelength of 1064 nm, when self-absorption was reduced by use of a low initial density target. Moreover, the lower-density results in a narrower spectrum and therefore improved spectral purity. It is shown to be important to use a low initial density target and/or to produce low electron density plasmas for efficient extreme ultraviolet sources when using high-Z targets.

  5. Color-conversion efficiency enhancement of quantum dots via selective area nano-rods light-emitting diodes.

    PubMed

    Liu, Che-Yu; Chen, Tzu-Pei; Kao, Tsung Sheng; Huang, Jhih-Kai; Kuo, Hao-Chung; Chen, Yang-Fang; Chang, Chun-Yen

    2016-08-22

    A large enhancement of color-conversion efficiency of colloidal quantum dots in light-emitting diodes (LEDs) with novel structures of nanorods embedded in microholes has been demonstrated. Via the integration of nano-imprint and photolithography technologies, nanorods structures can be fabricated at specific locations, generating functional nanostructured LEDs for high-efficiency performance. With the novel structured LED, the color-conversion efficiency of the existing quantum dots can be enhanced by up to 32.4%. The underlying mechanisms can be attributed to the enhanced light extraction and non-radiative energy transfer, characterized by conducting a series of electroluminescence and time-resolved photoluminescence measurements. This hybrid nanostructured device therefore exhibits a great potential for the application of multi-color lighting sources. PMID:27557273

  6. Efficiency enhancement in dye-sensitized solar cells with down conversion material ZnO: Eu3+, Dy3+

    NASA Astrophysics Data System (ADS)

    Yao, Nannan; Huang, Jinzhao; Fu, Ke; Liu, Shiyou; E, Dong; Wang, Yanhao; Xu, Xijin; Zhu, Min; Cao, Bingqiang

    2014-12-01

    The down conversion (DC) material ZnO: Eu3+, Dy3+ are synthesized by precipitation method and used to prepare the photo anode of dye-sensitized solar cells (DSSCs). The effects of down conversion material on the photoelectric performance of the DSSC were characterized by the X-ray diffraction (XRD), photoluminescence (PL), scanning electron microscope (SEM), current-voltage (I-V) curve, incident-photon-to-current conversion efficiency (IPCE) and UV-vis-NIR absorption spectroscopy. In this paper, Eu3+, Dy3+ codoped ZnO excited by from UV to blue light converts blue to red light emission, corresponding to the absorption region of the dye (N719). At the concentration 1.75% of ZnO: Eu3+, Dy3+ (weight ratio of DC to TiO2), the short-circuit current density and conversion efficiency of the DSSCs reached to the optimal values: 8.92 mA cm-2 and 4.48%, about 212% and 245% higher than with pure TiO2 and about 91.4% and 105% higher than with TiO2/graphene (G) structure, respectively. The research result reveals that the application of DC material can improve the efficiency of DSSCs.

  7. Rapid and Efficient Conversion of (11) CO2 to (11) CO through Silacarboxylic Acids: Applications in Pd-Mediated Carbonylations.

    PubMed

    Nordeman, Patrik; Friis, Stig D; Andersen, Thomas L; Audrain, Hélène; Larhed, Mats; Skrydstrup, Troels; Antoni, Gunnar

    2015-12-01

    Herein, we present a new rapid, efficient, and low-cost radiosynthetic protocol for the conversion of (11) CO2 to (11) CO and its subsequent application in Pd-mediated reactions of importance for PET applications. This room-temperature methodology, using readily available chemical reagents, is carried out in simple glass vials, thus eliminating the need for expensive and specialized high-temperature equipment to access (11) CO. With this fast and near-quantitative conversion of (11) CO2 into (11) CO, aryl and heteroaryl iodides were easily converted into a broad selection of biologically active amides in radiochemical yields ranging from 29-84 %. PMID:26492852

  8. Efficient up-conversion of triplet excitons into a singlet state and its application for organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Endo, Ayataka; Sato, Keigo; Yoshimura, Kazuaki; Kai, Takahiro; Kawada, Atsushi; Miyazaki, Hiroshi; Adachi, Chihaya

    2011-02-01

    A material possessing a very small energy gap between its singlet and triplet excited states, ΔE1-3, which allows efficient up-conversion of triplet excitons into a singlet state and leads to efficient thermally activated delayed fluorescence (TADF), is reported. The compound, 2-biphenyl-4,6-bis(12-phenylindolo[2,3-a] carbazole-11-yl)-1,3,5-triazine, breaks the restriction of a large energy gap, with a ΔE1-3 of just 0.11 eV, while maintaining a high fluorescent radiative decay rate (kr˜107). The intense TADF provides a pathway for highly efficient electroluminescence.

  9. Calibration of STUD+ parameters to achieve optimally efficient broadband adiabatic decoupling in a single transient

    PubMed

    Bendall; Skinner

    1998-10-01

    for a single sech/tanh pulse. Residual splitting of the centerband, normally associated with incomplete or inefficient decoupling, is not seen in sech/tanh decoupling and therefore cannot be used as a measure of adiabatic decoupling efficiency. The calibrated experimental performance levels achieved in this study are within 20% of theoretical performance levels derived previously for ideal sech/tanh decoupling at high power, indicating a small scope for further improvement at practical RF power levels. The optimization procedures employed here will be generally applicable to any good combination of adiabatic inversion pulse and phase cycle. Copyright 1998 Academic Press. PMID:9761708

  10. In situ processed gold nanoparticle-embedded TiO2 nanofibers enabling plasmonic perovskite solar cells to exceed 14% conversion efficiency.

    PubMed

    Mali, Sawanta S; Shim, Chang Su; Kim, Hyungjin; Patil, Pramod S; Hong, Chang Kook

    2016-02-01

    We have demonstrated organometallic perovskite solar cells (PSCs) based on Au decorated TiO2 nanofibers and methylammonium lead iodide (MAPbI3). A power conversion efficiency of 14.92% was achieved, which is significantly higher than that of conventional mesoporous (mp) TiO2, as well as TiO2 nanofiber-based devices. The present synthetic process provides new opportunities for the development of efficient plasmonic PSCs based on metal oxide nanofibers. Solar cells based on these architectures exhibit a short-circuit current density J(SC) of 21.63 ± 0.36 mA cm(-2), V(OC) of 0.986 ± 0.01 V and fill factor of 70% ± 3%, which provide a power conversion efficiency of 14.92% ± 0.33% under standard AM 1.5 conditions. The results of time-resolved photoluminescence (TRPL) spectroscopy and solid-state impedance spectroscopy (ssIS) revealed that PSCs based on Au-decorated TiO2 nanofibers exhibit a low recombination rate. The present results are much higher than those for reported PSCs based on a Au@TiO2 electron-transporting layer (ETL). PMID:26759073

  11. A 24.4% solar to hydrogen energy conversion efficiency by combining concentrator photovoltaic modules and electrochemical cells

    NASA Astrophysics Data System (ADS)

    Nakamura, Akihiro; Ota, Yasuyuki; Koike, Kayo; Hidaka, Yoshihide; Nishioka, Kensuke; Sugiyama, Masakazu; Fujii, Katsushi

    2015-10-01

    The highest efficiency of 24.4% for the solar-to-hydrogen (STH) energy conversion was obtained in an outdoor field test by combining concentrator photovoltaic (CPV) modules with InGaP/GaAs/Ge three-junction cells and polymer-electrolyte electrochemical (EC) cells. The high efficiency was obtained by using the high-efficiency CPV modules (∼31% under the present operation conditions) and the direct connection between the CPV modules and the EC cells with an almost optimized number of elements in series. The STH efficiency bottleneck was clarified to be the efficiency of the CPV modules, the over-potential of the EC cells, and matching of the operation point to the maximal-power point of the CPV modules.

  12. Efficient electrochemical CO2 conversion powered by renewable energy

    SciTech Connect

    Kauffman, Douglas R.; Thakkar, Jay; Siva, Rajan; Matranga, Christopher; Ohodnicki, Paul R.; Zeng, Chenjie; Jin, Rongchao

    2015-06-29

    Here, the catalytic conversion of CO2 into industrially relevant chemicals is one strategy for mitigating greenhouse gas emissions. Along these lines, electrochemical CO2 conversion technologies are attractive because they can operate with high reaction rates at ambient conditions. However, electrochemical systems require electricity, and CO2 conversion processes must integrate with carbon-free, renewable-energy sources to be viable on larger scales. We utilize Au25 nanoclusters as renewably powered CO2 conversion electrocatalysts with CO2 → CO reaction rates between 400 and 800 L of CO2 per gram of catalytic metal per hour and product selectivities between 80 and 95%. These performance metrics correspond to conversion rates approaching 0.8–1.6 kg of CO2 per gram of catalytic metal per hour. We also present data showing CO2 conversion rates and product selectivity strongly depend on catalyst loading. Optimized systems demonstrate stable operation and reaction turnover numbers (TONs) approaching 6 × 106 mol CO2 molcatalyst–1 during a multiday (36 hours total hours) CO2electrolysis experiment containing multiple start/stop cycles. TONs between 1 × 106 and 4 × 106 molCO2 molcatalyst–1 were obtained when our system was powered by consumer-grade renewable-energy sources. Daytime photovoltaic-powered CO2 conversion was demonstrated for 12 h and we mimicked low-light or nighttime operation for 24 h with a solar-rechargeable battery. This proof-of-principle study provides some of the initial performance data necessary for assessing the scalability and technical viability of electrochemical CO2 conversion technologies. Specifically, we show the following: (1) all electrochemical CO2 conversion systems will produce a net increase in CO2 emissions if they do

  13. Efficient electrochemical CO2 conversion powered by renewable energy

    SciTech Connect

    Kauffman, Douglas R.; Thakkar, Jay; Siva, Rajan; Matranga, Christopher; Ohodnicki, Paul R.; Zeng, Chenjie; Jin, Rongchao

    2015-06-29

    The catalytic conversion of CO2 into industrially relevant chemicals is one strategy for mitigating greenhouse gas emissions. Along these lines, electrochemical CO2 conversion technologies are attractive because they can operate with high reaction rates at ambient conditions. However, electrochemical systems require electricity, and CO2 conversion processes must integrate with carbon-free, renewable-energy sources to be viable on larger scales. We utilize Au25 nanoclusters as renewably powered CO2 conversion electrocatalysts with CO2 → CO reaction rates between 400 and 800 L of CO2 per gram of catalytic metal per hour and product selectivities between 80 and 95%. These performance metrics correspond to conversion rates approaching 0.8–1.6 kg of CO2 per gram of catalytic metal per hour. We also present data showing CO2 conversion rates and product selectivity strongly depend on catalyst loading. Optimized systems demonstrate stable operation and reaction turnover numbers (TONs) approaching 6 × 106 mol CO2 molcatalyst–1 during a multiday (36 hours total hours) CO2electrolysis experiment containing multiple start/stop cycles. TONs between 1 × 106 and 4 × 106 molCO2 molcatalyst–1 were obtained when our system was powered by consumer-grade renewable-energy sources. Daytime photovoltaic-powered CO2 conversion was demonstrated for 12 h and we mimicked low-light or nighttime operation for 24 h with a solar-rechargeable battery. This proof-of-principle study provides some of the initial performance data necessary for assessing the scalability and technical viability of electrochemical CO2 conversion technologies. Specifically, we show the following: (1) all electrochemical CO2 conversion systems will produce a net increase in CO2 emissions if they do not

  14. Optimal Materials and Deposition Technique Lead to Cost-Effective Solar Cell with Best-Ever Conversion Efficiency (Fact Sheet)

    SciTech Connect

    Not Available

    2012-07-01

    This fact sheet describes how the SJ3 solar cell was invented, explains how the technology works, and why it won an R&D 100 Award. Based on NREL and Solar Junction technology, the commercial SJ3 concentrator solar cell - with 43.5% conversion efficiency at 418 suns - uses a lattice-matched multijunction architecture that has near-term potential for cells with {approx}50% efficiency. Multijunction solar cells have higher conversion efficiencies than any other type of solar cell. But developers of utility-scale and space applications crave even better efficiencies at lower costs to be both cost-effective and able to meet the demand for power. The SJ3 multijunction cell, developed by Solar Junction with assistance from foundational technological advances by the National Renewable Energy Laboratory, has the highest efficiency to date - almost 2% absolute more than the current industry standard multijunction cell-yet at a comparable cost. So what did it take to create this cell having 43.5% efficiency at 418-sun concentration? A combination of materials with carefully designed properties, a manufacturing technique allowing precise control, and an optimized device design.

  15. Dependence of Seebeck coefficient on a load resistance and energy conversion efficiency in a thermoelectric composite

    SciTech Connect

    Yamashita, Osamu Odahara, Hirotaka; Ochi, Takahiro; Satou, Kouji

    2007-10-02

    The thermo-emf {delta}V and current {delta}I generated by imposing the alternating temperature gradients (ATG) at a period of T and the steady temperature gradient (STG) on a thermoelectric (TE) composite were measured as a function of t, where t is the lapsed time and T was varied from 60 to or {infinity} s. The STG and ATG were produced by imposing steadily and alternatively a source voltage V in the range from 1.0 to 4.0 V on two Peltier modules sandwiching a composite. {delta}T, {delta}V, {delta}I and V{sub P} oscillate at a period T and their waveforms vary significantly with a change of T, where {delta}V and V{sub P} are the voltage drops in a load resistance R{sub L} and in resistance R{sub P} of two modules. The resultant Seebeck coefficient |{alpha}| = |{delta}V|/{delta}T of a composite under the STG was found to be expressed as |{alpha}| = |{alpha}{sub 0}|(1 - R{sub comp}/R{sub T}), where R{sub T} is the total resistance of a circuit for measuring the output signals and R{sub comp} is the resistance of a composite. The effective generating power {delta}W{sub eff} has a local maximum at T = 960 s for the p-type composite and at T = 480 s for the n-type one. The maximum energy conversion efficiency {eta} of the p- and n-type composites under the ATG produced by imposing a voltage of 4.0 V at an optimum period were 0.22 and 0.23% at {delta}T{sub eff} = 50 K, respectively, which are 42 and 43% higher than those at {delta}T = 42 K under the STG. These maximum {eta} for a TE composite sandwiched between two Peltier modules, were found to be expressed theoretically in terms of R{sub P}, R{sub T}, R{sub L}, {alpha}{sub P} and {alpha}, where {alpha}{sub P} and {alpha} are the resultant Seebeck coefficients of Peltier modules and a TE composite.

  16. Efficient Conversion of Spermatogonial Stem Cells to Phenotypic and Functional Dopaminergic Neurons via the PI3K/Akt and P21/Smurf2/Nolz1 Pathway.

    PubMed

    Yang, Hao; Liu, Yang; Hai, Yanan; Guo, Ying; Yang, Shi; Li, Zheng; Gao, Wei-Qiang; He, Zuping

    2015-12-01

    Parkinson's disease (PD) is a common neurodegenerative syndrome characterized by loss of midbrain dopaminergic (DA) neurons. Generation of functional dopaminergic (DA) neurons is of unusual significance for treating Parkinson's disease (PD). However, direct conversion of spermatogonial stem cells (SSCs) to functional DA neurons without being reprogrammed to a pluripotent status has not been achieved. Here, we report an efficient approach to obtain morphological, phenotypic, and functional DA neurons from SSCs using a specific combination of olfactory ensheathing cell-conditioned medium (OECCM) and several defined growth factors (DGF). By following the current protocol, direct conversion of SSCs (both SSC line and primary SSCs) to neural cells and DA neurons was demonstrated by expression of numerous phenotypic genes and proteins for neural cells, as well as cell morphological features. More significantly, SSCs-derived DA neurons acquired neuronal functional properties such as synapse formation, electrophysiology activity, and dopamine secretion. Furthermore, PI3K/Akt pathway and p21/Nolz1 cascades were activated whereas Smurf2 was inactivated, leading to cell cycle exit during the conversion of SSCs into DA neurons. Collectively, this study could provide sufficient neural cells from SSCs for applications in the treatment of PD and offers novel insights into mechanisms underlying neural system development from the line of germ cells. PMID:25373443

  17. X-ray conversion efficiency as a function of atomic number for 0.26-micron-laser - Irradiated targets

    NASA Astrophysics Data System (ADS)

    Alaterre, P.; Pepin, H.; Fabbro, R.; Faral, B.

    1986-11-01

    Soft-X-ray low-resolution experimental spectra are obtained for a large set of targets irradiated at 2 x 10 to the 14th W/sq cm by 0.26-micron radiation. X-ray conversion efficiencies in various spectral ranges are studied as a function of atomic number. To calculate the emissivity, a simple, multiple-Z atomic-physics model is developed based on a screened-hydrogenic description for the atomic structure and on a non-LTE modified Saha approach to plasma-ionization properties. Experimental soft-X-ray spectra are replicated by using a discrete summation of emissivities over a few temperatures with appropriate weighting factors determined from the experiment or through a separate hydrodynamic-code simulation. The modulations in the Z dependence of the X-ray conversion efficiency in various spectral ranges are well described and interpreted.

  18. Role of dc space charge field in the optimization of microwave conversion efficiency from a modulated intense relativistic electron beam

    SciTech Connect

    Xiao, Renzhen; Chen, Changhua; Wu, Ping; Song, Zhimin; Sun, Jun

    2013-12-07

    We demonstrate an efficiency of 70% with 5.1 GW microwave power for a diode voltage of 770 kV and a current modulation coefficient of 1.67 in a klystron-like relativistic backward wave oscillator. The device combines the advantages of reducing electron beam radius, adopting dual-cavity extractor, and introducing two pre-modulation cavities. A large dc space charge field is present due to the conversion of considerable potential energy to kinetic energy at the end of beam-wave interaction region. A nonlinear theory is developed to show that the dc space charge field can increase the current modulation coefficient and microwave conversion efficiency significantly.

  19. High energy conversion efficiency in laser-proton acceleration by controlling laser-energy deposition onto thin foil targets

    SciTech Connect

    Brenner, C. M.; Robinson, A. P. L.; Markey, K.; Scott, R. H. H.; Lancaster, K. L.; Musgrave, I. O.; Spindloe, C.; Winstone, T.; Wyatt, D.; Neely, D.; Gray, R. J.; McKenna, P.; Rosinski, M.; Badziak, J.; Wolowski, J.; Deppert, O.; Batani, D.; Davies, J. R.; Hassan, S. M.; Tatarakis, M.; and others

    2014-02-24

    An all-optical approach to laser-proton acceleration enhancement is investigated using the simplest of target designs to demonstrate application-relevant levels of energy conversion efficiency between laser and protons. Controlled deposition of laser energy, in the form of a double-pulse temporal envelope, is investigated in combination with thin foil targets in which recirculation of laser-accelerated electrons can lead to optimal conditions for coupling laser drive energy into the proton beam. This approach is shown to deliver a substantial enhancement in the coupling of laser energy to 5–30 MeV protons, compared to single pulse irradiation, reaching a record high 15% conversion efficiency with a temporal separation of 1 ps between the two pulses and a 5 μm-thick Au foil. A 1D simulation code is used to support and explain the origin of the observation of an optimum pulse separation of ∼1 ps.

  20. Highly coherent red-shifted dispersive wave generation around 1.3 μm for efficient wavelength conversion

    SciTech Connect

    Li, Xia; Bi, Wanjun; Chen, Wei; Xue, Tianfeng; Hu, Lili; Liao, Meisong; Gao, Weiqing

    2015-03-14

    This research investigates the mechanism of the optical dispersive wave (DW) and proposes a scheme that can realize an efficient wavelength conversion. In an elaborately designed photonic crystal fiber, a readily available ytterbium laser operating at ∼1 μm can be transferred to the valuable 1.3 μm wavelength range. A low-order soliton is produced to concentrate the energy of the DW into the target wavelength range and improve the degree of coherence. The input chirp is demonstrated to be a factor that enhances the wavelength conversion efficiency. With a positive initial chirp, 76.6% of the pump energy in the fiber can be transferred into a spectral range between 1.24 and 1.4 μm. With the use of a grating compressor, it is possible to compress the generated coherent DW of several picoseconds into less than 90 fs.

  1. Patterning ITO by Template-Assisted Colloidal-Lithography for Enhancing Power Conversion Efficiency in Organic Photovoltaic.

    PubMed

    Lee, Jin-Su; Yu, Jung-Hun; Hwang, Ki-Hwan; Nam, Sang-Hun; Boo, Jin-Hyo; Yun, Sang H

    2016-05-01

    Highly structured interfaces are very desirable in organic photovoltaic solar cells (OPVs), in order to enhance power conversion efficiency (PCE) by decreasing of the transport path for excited charge carriers in the absorber and increasing the optical path length for photon absorption. Many complicated, high-cost lithographic methods have been attempted to modify the surface of the absorber or substrate. However, solution-based colloidal-lithography processes are scalable and cost-effective, but generally result in non-uniform structured surfaces. In this report, we demonstrated an optimized silica-templated colloidal lithographical approach to create a well-defined and controlled transparent ITO layer for enhancing power conversion efficiency (PCE). Additionally, morphological effects of the patterned ITO on optical properties and PCE were analyzed in detail. PMID:27483864

  2. Optimal enhancement in conversion efficiency of crystalline Si solar cells using inverse opal photonic crystals as back reflectors

    NASA Astrophysics Data System (ADS)

    Chaouachi, A.; Chtourou, R.; M'nif, A.; Hamzaoui, A. H.

    2015-04-01

    The effect of using inverse opal photonic crystals as back reflectors on the power conversion efficiency of c-Si solar cells is investigated. The reflection spectra of inverse opal photonic crystals with different diameters of air spheres are simulated using the finite difference time domain (FDTD) method. The reflection peaks are correlated with photonic band gaps present in the photonic band gap diagram. Significant improvement in the optical absorption of the crystalline silicon layer is recorded when inverse opal photonic crystals are considered. Physical mechanisms which may contribute to the enhancement of the light absorption are underlined. With higher short-circuit current enhancement possible, and with no corresponding degradation in open-circuit voltage Voc or the fill factor, the power conversion efficiency is increased significantly when inverse opal photonic crystals are used as back reflectors with optimized diameter of air spheres.

  3. GUIDELINES FOR INDUSTRIAL BOILER PERFORMANCE IMPROVEMENT. (BOILER ADJUSTMENT PROCEDURES TO MINIMIZE AIR POLLUTION AND TO ACHIEVE EFFICIENT USE OF FUEL)

    EPA Science Inventory

    Recommended procedures for improving industrial boiler performance to minimize air pollution and to achieve efficient use of fuel are given. It is intended for use by industrial boiler operators to perform an efficiency and emissions tune-up on boilers firing gas, oil, or coal. P...

  4. Annealing group III-V compound doped silicon-germanium alloy for improved thermo-electric conversion efficiency

    NASA Technical Reports Server (NTRS)

    Vandersande, Jan W. (Inventor); Wood, Charles (Inventor); Draper, Susan L. (Inventor)

    1989-01-01

    The thermoelectric conversion efficiency of a GaP doped SiGe alloy is improved about 30 percent by annealing the alloy at a temperature above the melting point of the alloy, preferably stepwise from 1200 C to 1275 C in air to form large grains having a size over 50 microns and to form a GeGaP rich phase and a silicon rich phase containing SiP and SiO2 particles.

  5. Studying the energy dependence of intrinsic conversion efficiency of single crystal scintillators under X-ray excitation

    NASA Astrophysics Data System (ADS)

    Kalyvas, N.; Valais, I.; David, S.; Michail, Ch.; Fountos, G.; Liaparinos, P.; Kandarakis, I.

    2014-05-01

    Single crystal scintilators are used in various radiation detectors applications. The efficiency of the crystal can be determined by the Detector Optical Gain (DOG) defined as the ratio of the emitted optical photon flux over the incident radiation photons flux. A parameter affecting DOG is the intrinsic conversion efficiency ( n C ) giving the percentage of the X-ray photon power converted to optical photon power. n C is considered a constant value for X-ray energies in the order of keV although a non-proportional behavior has been reported. In this work an analytical model, has been utilized to single crystals scintillators GSO:Ce, LSO:Ce and LYSO:Ce to examine whether the intrinsic conversion efficiency shows non proportional behavior under X-ray excitation. DOG was theoretically calculated as a function of the incident X-ray spectrum, the X-ray absorption efficiency, the energy of the produced optical photons and the light transmission efficiency. The theoretical DOG values were compared with experimental data obtained by irradiating the crystals with X-rays at tube voltages from 50 to 140 kV and by measuring the light energy flux emitted from the irradiated screen. An initial value for n C (calculated from literature data) was assumed for the X-ray tube voltage of 50 kV. For higher X-ray tube voltages the optical photon propagation phenomena was assumed constant and any deviations between experimental and theoretical data were associated with changes in the intrinsic conversion efficiency. The experimental errors were below 7% for each experimental setup. The behavior of n C values for LSO:Ce and LYSO:Ce were found very similar, i.e., ranging with values from 0.089 at 50 kV to 0.015 at 140 kV, while for GSO:Ce, n C demonstrated a peak at 80 kV.

  6. Impact of PEGylation on the biological effects and light heat conversion efficiency of gold nanoshells on silica nanorattles.

    PubMed

    Liu, Huiyu; Liu, Tianlong; Wang, Hai; Li, Linlin; Tan, Longfei; Fu, Changhui; Nie, Guangjun; Chen, Dong; Tang, Fangqiong

    2013-09-01

    As an excellent photothermal agent candidate, gold nanoshells have attracted a great deal of attention, but the influences of PEGylation on their biological effects and light heat conversion efficiency remain unclear. Here we investigate the influences of PEGylation density on the gold nanoshells on silica nanorattles (GSNPs) to their biological effects, including their cellular uptake, "corona" of biological macromolecules they are covered with, in vivo biodistribution and toxicities, and their in vitro and in vivo light heat conversion efficiency. The results suggest PEGylation obviously impacts the uptake patterns of GSNPs. Less-density PEGylated GSNPs show enhanced cellular uptake caused by the high dose exposure on cell surface due to their rapid aggregation. High-density PEGylated GSNPs show advantages in less toxicity for suppression of aggregation of GSNPs, avoidance of RES, good enhanced permeability and retention (EPR) effect of cancerous tumors, especially the enhanced light heat conversion efficiency in vivo. Less or insufficient PEGylation may induce in vivo toxicity. This study highlights the need to study the effect of PEGylation for near infrared (NIR) light absorbing nanoparticles to predict the effects and safety of nanotherapeutics. PMID:23777913

  7. Evaluation of the energy efficiency of CO2 conversion in microwave discharges using a reaction kinetics model

    NASA Astrophysics Data System (ADS)

    Kozák, Tomáš; Bogaerts, Annemie

    2015-02-01

    We use a zero-dimensional reaction kinetics model to simulate CO2 conversion in microwave discharges where the excitation of the vibrational levels plays a significant role in the dissociation kinetics. The model includes a description of the CO2 vibrational kinetics, taking into account state-specific VT and VV relaxation reactions and the effect of vibrational excitation on other chemical reactions. The model is used to simulate a general tubular microwave reactor, where a stream of CO2 flows through a plasma column generated by microwave radiation. We study the effects of the internal plasma parameters, namely the reduced electric field, electron density and the total specific energy input, on the CO2 conversion and its energy efficiency. We report the highest energy efficiency (up to 30%) for a specific energy input in the range 0.4-1.0 eV/molecule and a reduced electric field in the range 50-100 Td and for high values of the electron density (an ionization degree greater than 10-5). The energy efficiency is mainly limited by the VT relaxation which contributes dominantly to the vibrational energy losses and also contributes significantly to the heating of the reacting gas. The model analysis provides useful insight into the potential and limitations of CO2 conversion in microwave discharges.

  8. A single nucleotide polymorphism in suppressor of cytokine signalling-2 is associated with growth and feed conversion efficiency in pigs.

    PubMed

    Chen, Y; Piper, E; Zhang, Y; Tier, B; Graser, H U; Luxford, B G; Moran, C

    2011-04-01

    Feed efficiency and growth are the most important traits in pig production, and very few genetic markers have been reported to be associated with feed efficiency. The suppressor of cytokine signalling-2 (encoded by SOCS2) is the main negative regulator of somatic growth, and the knockout of SOCS2 and naturally mutant mice have high-growth phenotypes. Porcine SOCS2 was selected as a primary positional candidate for feed efficiency, because it is located on chromosome 5q, in the vicinity of a Quantitative Trait Locus (QTL) region for food conversion ratio in pigs. Here, we report five single nucleotide polymorphisms identified by sequencing of the promoter region and exon 1. One PCR-RFLP assay was designed for genotyping the polymorphism c.1667A > G (GenBank Accession No AY312266). Association analyses were performed in an Australian mapping resource pedigree population (PRDC-US43) for food conversion ratio, backfat, IGF1 level and growth traits and showed significant effects on average daily gain on test (ADG2) (P < 0.01) and marginal association with food conversion ratio (FCR) (P < 0.08). PMID:24725230

  9. High efficiency light source using solid-state emitter and down-conversion material

    DOEpatents

    Narendran, Nadarajah; Gu, Yimin; Freyssinier, Jean Paul

    2010-10-26

    A light emitting apparatus includes a source of light for emitting light; a down conversion material receiving the emitted light, and converting the emitted light into transmitted light and backward transmitted light; and an optic device configured to receive the backward transmitted light and transfer the backward transmitted light outside of the optic device. The source of light is a semiconductor light emitting diode, a laser diode (LD), or a resonant cavity light emitting diode (RCLED). The down conversion material includes one of phosphor or other material for absorbing light in one spectral region and emitting light in another spectral region. The optic device, or lens, includes light transmissive material.

  10. Genetic variation among sorghum and Brachypodium distachyon accessions for biological conversion efficiency

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using the well-developed microbial system, Clostridium phytofermentans, we developed an assay that provides the ability to measure the impact of pretreatment, conversion processes, and microbial and plant genetic diversity of digestibility, and thereby determine the potential effects of numerous var...

  11. Enhancing alfalfa conversion efficiencies for sugar recovery and ethanol production by altering lignin composition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Alfalfa (Medicago sativa L.) has potential utility as an energy crop for conversion to biofuels because it is already produced commercially, grows as a perennial, increases soil nitrogen, and the protein enriched leaves can be marketed as a co-product for animal feed. In this paper, the biomass proc...

  12. Evaluating low lignin mutants of forage sorghum for increased conversion efficiency to sugars and ethanol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reduced lignin near-isogenic lines of Atlas bmr-6, bmr-12, and bmr-6 bmr-12 forage sorghum (Sorghum biocolor (L.)) were evaluated as sources of biomass for conversion to sugars and ethanol. These mutants have the advantage of reduced lignin contents and high biomass yields. Field replicates of wil...

  13. Micropower chemical fuel-to-electric conversion : a "regenerative flip" hydrogen concentration cell promising near carnot efficiency.

    SciTech Connect

    Wally, Karl

    2006-05-01

    Although battery technology is relatively mature, power sources continue to impose serious limitations for small, portable, mobile, or remote applications. A potentially attractive alternative to batteries is chemical fuel-to-electric conversion. Chemical fuels have volumetric energy densities 4 to 10 times those of batteries. However, realizing this advantage requires efficient chemical fuel-to-electric conversion. Direct electrochemical conversion would be the ideal, but, for most fuels, is generally not within the state-of-the-science. Next best, chemical-to-thermal-to-electric conversion can be attractive if efficiencies can be kept high. This small investigative project was an exploration into the feasibility of a novel hybrid (i.e., thermal-electrochemical) micropower converter of high theoretical performance whose demonstration was thought to be within near-term reach. The system is comprised of a hydrogen concentration electrochemical cell with physically identical hydrogen electrodes as anode and cathode, with each electrode connected to physically identical hydride beds each containing the same low-enthalpy-of-formation metal hydride. In operation, electrical power is generated by a hydrogen concentration differential across the electrochemical cell. This differential is established via coordinated heating and passive cooling of the corresponding hydride source and sink. Heating is provided by the exothermic combustion (i.e., either flame combustion or catalytic combustion) of a chemical fuel. Upon hydride source depletion, the role of source and sink are reversed, heating and cooling reversed, electrodes commutatively reversed, cell operation reversed, while power delivery continues unchanged. This 'regenerative flip' of source and sink hydride beds can be cycled continuously until all available heating fuel is consumed. Electricity is efficiently generated electrochemically, but hydrogen is not consumed, rather the hydrogen is regeneratively cycled as

  14. Facile synthesis of biocompatible cysteine-coated CuS nanoparticles with high photothermal conversion efficiency for cancer therapy.

    PubMed

    Liu, Xijian; Li, Bo; Fu, Fanfan; Xu, Kaibing; Zou, Rujia; Wang, Qian; Zhang, Bingjie; Chen, Zhigang; Hu, Junqing

    2014-08-14

    The semiconductor compounds have been proven to be promising candidates as a new type of photothermal therapy agent, but unsatisfactory photothermal conversion efficiencies limit their widespread application in photothermal therapy (PTT). Herein, we synthesized cysteine-coated CuS nanoparticles (Cys-CuS NPs) as highly efficient PTT agents by a simple aqueous solution method. The Cys-CuS NPs have a good biocompatibility owing to their biocompatible cysteine coating and exhibit a strong absorption in the near-infrared region due to the localized surface plasma resonances of valence-band free carriers. The photothermal conversion efficiency of Cys-CuS NPs reaches 38.0%, which is much higher than that of the recently reported Cu9S5 and Cu(2-x)Se nanocrystals. More importantly, tumor growth can be efficiently inhibited in vivo by the fatal heat arising from the excellent photothermal effect of Cys-CuS NPs at a low concentration under the irradiation of a 980 nm laser with a safe power density of 0.72 W cm(-2). Therefore, the Cys-CuS NPs have great potential as ideal photothermal agents for cancer therapy. PMID:24950757

  15. Efficient Raman conversion of XeC1 laser into the blue-green region. Final report

    SciTech Connect

    Komine, H.; Stappaerts, E.A.

    1982-11-01

    An efficient, blue-green laser source is urgently needed for the Navy submarine communication system as well as other applications. The rare-gas halide excimer lasers developed over the last few years appear to meet the requirements on efficiency and scalability, but the wavelength of their near-uv emission is too short for direct use. This report describes theoretical and experimental work on the feasibility of a novel, frequency conversion scheme, based on higher order Raman scattering, for efficiently shifting the uv wavelengths of these excimer lasers to the blue-green region. The technique uses an oscillator-amplifier combination, and the Raman medium is typically a gas such as hydrogen or deuterium at a pressure of several atmospheres. In preliminary experiments with a frequency-tripled Nd:YAG laser (355 nm), photon efficiencies as high as 51 percent have been obtained for the second Stokes order, in very good agreement with computer simulations. More recently, the Raman oscillator-amplifier experiments have been extended to the case of an XeC1 pump laser. The Raman amplifier experiments led to the observation of significant conversion from 308 nm to 499 nm by third Stokes order shifting for the first time.

  16. A calorimetric study of energy conversion efficiency of a sonochemical reactor at 500 kHz for organic solvents.

    PubMed

    Toma, Maricela; Fukutomi, Satoshi; Asakura, Yoshiyuki; Koda, Shinobu

    2011-01-01

    It would seem that the economic viability is yet to be established for a great number of sonochemical processes, owning to their perfectible ultrasonic equipments. Industrial scale sonoreactors may become more important as a result of mastering the parameters with influence on their energy balance. This work related the solvent type to the energy efficiency as the first step of a complex study aiming to assess the energy balance of sonochemical reactors at 500 kHz. Quantitative measurements of ultrasonic power for water and 10 pure organic solvents were performed by calorimetry for a cylindrically shaped sonochemical reactor with a bottom mounted vibrating plate. It was found that the ultrasonic power is strongly related to the solvent, the energy conversion for organic liquids is half from that of water and there is a drop in energy efficiency for filling levels up to 250 mm organic solvents. Surface tension, viscosity and vapor pressure influence the energy conversion for organic solvents, but it is difficult explain these findings based on physical properties of solvents alone. The apparent intensity of the atomization process shows a good agreement with the experimentally determined values for energy conversion for water and the solvent group studied here. This study revealed that to attain the same ultrasonic power level, more electrical energy is need for organic solvents as compared to water. The energy balance equation has been defined based on these findings by considering an energy term for atomization. PMID:20655791

  17. Parametric Study of Up-Conversion Efficiency in Er-Doped Lanthanide Hosts Under 780 nm/980 nm Excitation Wavelengths

    NASA Astrophysics Data System (ADS)

    Samir, E.; Shehata, N.; Aldacher, M.; Kandas, I.

    2016-06-01

    Up-conversion is a process of converting low energy light photons to higher energy ones, which can be extensively used in many applications. This paper presents a detailed parametric study of the up-conversion process under different wavelength excitations—780 nm and 980 nm—showing the optical conversion mechanisms that affect the emitted light quantum yield efficiencies. The studied material is erbium-doped β-NaYF4 material, which is one of the most recently studied materials due to its low phonon energy. The studied simulation considers most processes and possible transitions that can take place between Er3+ ions. Einstein coefficients, which are the main parameters that are responsible for the transitions probabilities, are discussed in detail using Judd-Ofelt analysis. In addition, the effect of changing some parametric values is discussed, showing their optimum values that could improve the quantum yield efficiency. This model is very promising, and generic, and can be applied for any host material under any excitation wavelengths by varying the material-dependent parameters.

  18. High efficiency solar-to-hydrogen conversion on a monolithically integrated InGaN/GaN/Si adaptive tunnel junction photocathode.

    PubMed

    Fan, Shizhao; AlOtaibi, Bandar; Woo, Steffi Y; Wang, Yongjie; Botton, Gianluigi A; Mi, Zetian

    2015-04-01

    H2 generation under sunlight offers great potential for a sustainable fuel production system. To achieve high efficiency solar-to-hydrogen conversion, multijunction photoelectrodes have been commonly employed to absorb a large portion of the solar spectrum and to provide energetic charge carriers for water splitting. However, the design and performance of such tandem devices has been fundamentally limited by the current matching between various absorbing layers. Here, by exploiting the lateral carrier extraction scheme of one-dimensional nanowire structures, we have demonstrated that a dual absorber photocathode, consisting of p-InGaN/tunnel junction/n-GaN nanowire arrays and a Si solar cell wafer, can operate efficiently without the strict current matching requirement. The monolithically integrated photocathode exhibits an applied bias photon-to-current efficiency of 8.7% at a potential of 0.33 V versus normal hydrogen electrode and nearly unity Faradaic efficiency for H2 generation. Such an adaptive multijunction architecture can surpass the design and performance restrictions of conventional tandem photoelectrodes. PMID:25811636

  19. Synthesis of a Sulfonated Two-Dimensional Covalent Organic Framework as an Efficient Solid Acid Catalyst for Biobased Chemical Conversion.

    PubMed

    Peng, Yongwu; Hu, Zhigang; Gao, Yongjun; Yuan, Daqiang; Kang, Zixi; Qian, Yuhong; Yan, Ning; Zhao, Dan

    2015-10-12

    Because of limited framework stability tolerance, de novo synthesis of sulfonated covalent organic frameworks (COFs) remains challenging and unexplored. Herein, a sulfonated two-dimensional crystalline COF, termed TFP-DABA, was synthesized directly from 1,3,5-triformylphloroglucinol and 2,5-diaminobenzenesulfonic acid through a previously reported Schiff base condensation reaction, followed by irreversible enol-to-keto tautomerization, which strengthened its structural stability. TFP-DABA is a highly efficient solid acid catalyst for fructose conversion with remarkable yields (97 % for 5-hydroxymethylfurfural and 65 % for 2,5-diformylfuran), good chemoselectivity, and good recyclability. The present study sheds light on the de novo synthesis of sulfonated COFs as novel solid acid catalysts for biobased chemical conversion. PMID:26448524

  20. Efficient LUT-Based Truncated Multiplier and Its Application in RGB to YCbCr Color Space Conversion

    NASA Astrophysics Data System (ADS)

    Hoang, Van-Phuc; Pham, Cong-Kha

    High performance, low area multipliers are highly desired for modern and future DSP systems due to the increasing demand of high speed DSP applications. In this paper, we present an efficient architecture for an LUT-based truncated multiplier and its application in RGB to YCbCr color space conversion which can be used for digital TV, image and video processing systems. By employing an improved split LUT-based architecture and LUT optimization method, the proposed multiplier can reduce the value of area-delay product by up to 52% compared with other constant multiplier methods. The FPGA implementation of a color space conversion application employing the proposed multiplier also results in significant reduction of area-delay product of up to 48%.

  1. The effect of air flow on the temperature distribution and the harmonic conversion efficiency of the ADP crystal with large aperture in the temperature control scheme

    NASA Astrophysics Data System (ADS)

    Sun, Fuzhong; Zhang, Peng; Lu, Lihua; Xiang, Yong; Bai, Qingshun

    2016-03-01

    This paper presented a temperature control scheme for ammonium dihydrogen phosphate (ADP) crystal of Ф80 mm in diameter, and the influence of the air flow was also studied. This research aims to obtain the high energy, high frequency laser with large aperture under the non-critical phase matching (NCPM). Firstly, thermal analysis was carried out to investigate the air flow property in the cavity, as well as the effect of ambient temperature was analyzed. Secondly, the temperature distributions of air flow were achieved using the Finite Volume Method (FVM), and this prediction was validated by the experiment results. Finally, the effect of air flow in the cavity was obtained from the heating method, and the variation of harmonic conversion efficiency caused by the ambient temperature was also highlighted.

  2. 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.

  3. Improved conversion efficiency of InN/p-GaN heterostructure solar cells with embedded InON quantum dots

    NASA Astrophysics Data System (ADS)

    Ke, Wen-Cheng; Liang, Zhong-Yi; Yang, Cheng-Yi; Chan, Yu-Teng; Jiang, Chi-Yung

    2016-02-01

    An indium oxynitride (InON) quantum dot (QD) layer was inserted between the indium nitride (InN) and p-type gallium nitride (GaN) films for improving the conversion efficiency of the heterostructure solar cells. The InN/InON QD/p-GaN heterostructure solar cells exhibited a high open-circuit voltage of 2.29 V, short-circuit current density of 1.64 mA/cm2, and conversion efficiency of 1.12% under AM 1.5G illumination. Compared with samples without InON QDs, the power conversion efficiency of sample with InON QDs increased twofold; this increase was attributed to the increase in short-current density. The external quantum efficiency of 250-nm-thick InN/p-GaN heterostructure solar cells has a highest value of 6.5% in the wavelength range of 700-1100 nm. The photogenerated holes separated in the depletion region of InN thin films is difficult to transport across the energy barrier between the InN and p-GaN layers. The oxygen vacancy assisted carrier transport in the InN/InON QD/p-GaN sample, which was evidenced in its current-voltage (I-V) and capacitance-voltage (C-V) characteristics. The dark I-V characteristic curves in the bias range of -2 to 2 V exhibited ohmic behavior, which indicated the absence of a transport barrier between the InN and p-GaN layers. In addition, a shoulder peak at -0.08 V was observed in the high-frequency (60-100 kHz) C-V characteristic curves corresponding to carrier capture and emission in the shallow defect state of oxygen vacancy in the InON QDs. The oxygen vacancy exists inside the InON QDs and generates the interface states in the InON QD/p-GaN interface to form a carrier transport path. Thus, more photogenerated holes can transport via the InON QDs into the p-GaN layer, contributing to the photocurrent and resulting in high conversion efficiency for the InN/InON QD/p-GaN heterostructure solar cells.

  4. Tandem concentrator solar cells with 30 percent (AMO) power conversion efficiency

    NASA Technical Reports Server (NTRS)

    Avery, J. E.; Fraas, L. M.; Sundaram, V. S.; Brinker, David J.; Gee, J. M.; Oneill, Mark J.

    1991-01-01

    Very high efficiency concentrator solar panels are envisioned as economical and reliable electrical power subsystems for space based platforms of the future. GaAs concentrator cells with very high efficiencies and good sub-bandgap transmissions can be fabricated on standard wafers. GaSb booster cell development is progressing very well; performance characteristics are still improving dramatically. Consistent GaAs/GaSb stacked cell AMO efficiencies greater than 30 percent are expected.

  5. Expert Meeting Report: Achieving the Best Installed Performance from High-Efficiency Residential Gas Furnaces

    SciTech Connect

    Brand, Larry

    2012-03-01

    This report describes a Building America expert meeting hosted on July 28, 2011, by the Partnership for Advanced Residential Retrofit (PARR) team. The purpose of this meeting was to identify installation practices that provide the best installed efficiency for residential gas furnaces, explain how AFUE and field efficiency can differ, and investigate the impact of installation practices on the efficiency and long-term durability of the furnace.

  6. Expert Meeting Report: Achieving the Best Installed Performance from High-Efficiency Residential Gas Furnaces

    SciTech Connect

    Brand, L.

    2012-03-01

    This report describes a Building America expert meeting hosted on July 28, 2011, by the Partnership for Advanced Residential Retrofit team. The purpose of this meeting was to identify installation practices that provide the best installed efficiency for residential gas furnaces, explain how AFUE and field efficiency can differ, and investigate the impact of installation practices on the efficiency and long-term durability of the furnace.

  7. New strategy to promote conversion efficiency using high-index nanostructures in thin-film solar cells

    PubMed Central

    Wang, DongLin; Su, Gang

    2014-01-01

    Nano-scaled metallic or dielectric structures may provide various ways to trap light into thin-film solar cells for improving the conversion efficiency. In most schemes, the textured active layers are involved into light trapping structures that can provide perfect optical benefits but also bring undesirable degradation of electrical performance. Here we propose a novel approach to design high-performance thin-film solar cells. In our strategy, a flat active layer is adopted for avoiding electrical degradation, and an optimization algorithm is applied to seek for an optimized light trapping structure for the best optical benefit. As an example, we show that the efficiency of a flat a-Si:H thin-film solar cell can be promoted close to the certified highest value. It is also pointed out that, by choosing appropriate dielectric materials with high refractive index (>3) and high transmissivity in wavelength region of 350 nm–800 nm, the conversion efficiency of solar cells can be further enhanced. PMID:25418477

  8. Analysis and calculation of electronic properties and light absorption of defective sulfur-doped silicon and theoretical photoelectric conversion efficiency.

    PubMed

    Jiang, He; Chen, Changshui

    2015-04-23

    Most material properties can be traced to electronic structures. Black silicon produced from SF6 or sulfur powder via irradiation with femtosecond laser pulses displays decreased infrared absorption after annealing, with almost no corresponding change in visible light absorption. The high-intensity laser pulses destroy the original crystal structure, and the doping element changes the material performance. In this work, the structural and electronic properties of several sulfur-doped silicon systems are investigated using first principle calculations. Depending on the sulfur concentration (level of doping) and the behavior of the sulfur atoms in the silicon lattice, different states or an absence of states are exhibited, compared with the undoped system. Moreover, the visible-infrared light absorption intensities are structure specific. The results of our theoretical calculations show that the conversion efficiency of sulfur-doped silicon solar cells depends on the sulfur concentrations. Additionally, two types of defect configurations exhibit light absorption characteristics that differ from the other configurations. These two structures produce a rapid increase in the theoretical photoelectric conversion efficiency in the range of the specific chemical potential studied. By controlling the positions of the atomic sulfur and the sulfur concentration in the preparation process, an efficient photovoltaic (PV) material may be obtainable. PMID:25798659

  9. Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure

    NASA Astrophysics Data System (ADS)

    May, Matthias M.; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

    2015-09-01

    Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators.

  10. Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure.

    PubMed

    May, Matthias M; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

    2015-01-01

    Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators. PMID:26369620

  11. Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure

    PubMed Central

    May, Matthias M.; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

    2015-01-01

    Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators. PMID:26369620

  12. Historical perspective of barriers to achieving high-efficiency silicon solar cells

    NASA Technical Reports Server (NTRS)

    Lindmayer, J.

    1985-01-01

    Early silicon solar cells were made of metallurgical-grade silicon with very low efficiency. The single-crystal silicon introduced in the mid-50's increased the efficiency to the 5% to 10% region. Throughout the 1960s the technology of the 2 x 2 cm or 2 x 4 cm space solar cell with 10% efficiency was established. In the early 1970s work related to the violet cell upset the status quo and space solar cells and cells in general became more efficient. The rest of the decade became characterized by establishing a terrestrial photovoltaic technology to support the development of a new industry. Costs per watt became the dominant consideration and frequently the efficiency was compromised. The introduction of materials and other forms of silicon dropped the efficiency and it is now a state of mine that accomplishing 10% efficiency with some alternative combination is regarded as success. Silicon solar cells are capable of delivering efficiences much greater than 10%.

  13. Ag nanocluster functionalized glasses for efficient photonic conversion in light sources, solar cells and flexible screen monitors.

    PubMed

    Kuznetsov, A S; Tikhomirov, V K; Shestakov, M V; Moshchalkov, V V

    2013-11-01

    An ever growing demand for efficient energy conversion, for instance in luminescent lamps, flexible screens and solar cells, results in the current significant growth of research on functionalized nanomaterials for these applications. This paper reviews recent developments of a new class of optically active nanostructured materials based on glasses doped with luminescent Ag nanoclusters consisting of only a few Ag atoms, suitable for mercury-free white light generation and solar down-shifting. This new approach, based solely on Ag nanocluster doped glasses, is compared to other alternatives in the field of Ag and rare-earth ion co-doped materials. PMID:23948871

  14. Ag nanocluster functionalized glasses for efficient photonic conversion in light sources, solar cells and flexible screen monitors

    NASA Astrophysics Data System (ADS)

    Kuznetsov, A. S.; Tikhomirov, V. K.; Shestakov, M. V.; Moshchalkov, V. V.

    2013-10-01

    An ever growing demand for efficient energy conversion, for instance in luminescent lamps, flexible screens and solar cells, results in the current significant growth of research on functionalized nanomaterials for these applications. This paper reviews recent developments of a new class of optically active nanostructured materials based on glasses doped with luminescent Ag nanoclusters consisting of only a few Ag atoms, suitable for mercury-free white light generation and solar down-shifting. This new approach, based solely on Ag nanocluster doped glasses, is compared to other alternatives in the field of Ag and rare-earth ion co-doped materials.

  15. Size dependent cellular uptake, in vivo fate and light-heat conversion efficiency of gold nanoshells on silica nanorattles

    NASA Astrophysics Data System (ADS)

    Liu, Huiyu; Liu, Tianlong; Li, Linlin; Hao, Nanjing; Tan, Longfei; Meng, Xianwei; Ren, Jun; Chen, Dong; Tang, Fangqiong

    2012-05-01

    Despite advances in photothermal therapy of gold nanoshells, reliable evaluations of their size dependence on the relative biological effects are needed. We report the size effects of PEGylated gold nanoshells on silica nanorattles (pGSNs) on their cellular uptake, in vivo fate and light-heat conversion efficiency in this study. The results indicate that smaller pGSNs have enhanced cellular uptake by the MCF-7 cells. For in vivo biodistribution study, pGSNs of different particle sizes (84-315 nm) distribute mainly in the liver and spleen in MCF-7 tumor-bearing BALB/c nude mice. Smaller pGSNs have a longer blood-circulation lifetime and higher light-heat conversion efficiency both in vitro and in vivo compared with larger ones. All three sizes of pGSNs can be excreted from the mice body at a slow rate and do not cause tissue toxicity after intravenous injection at a dosage of 20 mg kg-1 for three times. The data support the feasibility of optimizing the therapeutic process for photothermal cell killing by plasmonic gold nanoshells.Despite advances in photothermal therapy of gold nanoshells, reliable evaluations of their size dependence on the relative biological effects are needed. We report the size effects of PEGylated gold nanoshells on silica nanorattles (pGSNs) on their cellular uptake, in vivo fate and light-heat conversion efficiency in this study. The results indicate that smaller pGSNs have enhanced cellular uptake by the MCF-7 cells. For in vivo biodistribution study, pGSNs of different particle sizes (84-315 nm) distribute mainly in the liver and spleen in MCF-7 tumor-bearing BALB/c nude mice. Smaller pGSNs have a longer blood-circulation lifetime and higher light-heat conversion efficiency both in vitro and in vivo compared with larger ones. All three sizes of pGSNs can be excreted from the mice body at a slow rate and do not cause tissue toxicity after intravenous injection at a dosage of 20 mg kg-1 for three times. The data support the feasibility of

  16. The Effect of Curriculum for Developing Efficient Studying Skills on Academic Achievements and Studying Skills of Learners

    ERIC Educational Resources Information Center

    Demir, Semra; Kilinc, Mehmet; Dogan, Ali

    2012-01-01

    Purpose of this study is to examine the effect of "Development of Efficient Studying Skills Curriculum" on academic achievements and studying skills of 7th grade primary school students. In this study, pre-test post-test from experiment models and semi-experimental model with control group were preferred. The reason for the preference is…

  17. Carbon Nitride-Aromatic Diimide-Graphene Nanohybrids: Metal-Free Photocatalysts for Solar-to-Hydrogen Peroxide Energy Conversion with 0.2% Efficiency.

    PubMed

    Kofuji, Yusuke; Isobe, Yuki; Shiraishi, Yasuhiro; Sakamoto, Hirokatsu; Tanaka, Shunsuke; Ichikawa, Satoshi; Hirai, Takayuki

    2016-08-10

    Solar-to-chemical energy conversion is a challenging subject for renewable energy storage. In the past 40 years, overall water splitting into H2 and O2 by semiconductor photocatalysis has been studied extensively; however, they need noble metals and extreme care to avoid explosion of the mixed gases. Here we report that generating hydrogen peroxide (H2O2) from water and O2 by organic semiconductor photocatalysts could provide a new basis for clean energy storage without metal and explosion risk. We found that carbon nitride-aromatic diimide-graphene nanohybrids prepared by simple hydrothermal-calcination procedure produce H2O2 from pure water and O2 under visible light (λ > 420 nm). Photoexcitation of the semiconducting carbon nitride-aromatic diimide moiety transfers their conduction band electrons to graphene and enhances charge separation. The valence band holes on the semiconducting moiety oxidize water, while the electrons on the graphene moiety promote selective two-electron reduction of O2. This metal-free system produces H2O2 with solar-to-chemical energy conversion efficiency 0.20%, comparable to the highest levels achieved by powdered water-splitting photocatalysts. PMID:27439985

  18. High-Efficiency Rooftop Air Conditioners: Innovative Procurement to Achieve Advances in Technology

    SciTech Connect

    Hollomon, Brad

    2003-08-01

    The U.S. Department of Energy, Defense Logistics Agency, and Pacific Northwest National Laboratory recently conducted a technology procurement to increase the availability of energy-efficient, packaged unitary ''rooftop'' air conditioners. The procurement encouraged air conditioner manufacturers to produce equipment that exceeded US energy efficiency standards by at least 25% at a lower life-cycle cost. An outgrowth of the project, a web-based cost estimator tool is now available to help consumers determine the cost-effectiveness of purchasing energy-efficient air conditioners based on climate conditions and other factors at their own locations.

  19. O&M Best Practices - A Guide to Achieving Operational Efficiency (Release 2.0)

    SciTech Connect

    Sullivan, Gregory P.; Pugh, Ray; Melendez, Aldo P.; Hunt, W. D.

    2004-07-31

    This guide, sponsored by DOE's Federal Energy Management Program, highlights operations and maintenance (O&M) programs targeting energy efficiency that are estimated to save 5% to 20% on energy bills without a significant capital investment. The purpose of this guide is to provide the federal O&M energy manager and practitioner with useful information about O&M management, technologies, energy efficiency and cost-reduction approaches.

  20. Direct nitrogen fixation at the edges of graphene nanoplatelets as efficient electrocatalysts for energy conversion

    NASA Astrophysics Data System (ADS)

    Jeon, In-Yup; Choi, Hyun-Jung; Ju, Myung Jong; Choi, In Taek; Lim, Kimin; Ko, Jaejung; Kim, Hwan Kyu; Kim, Jae Cheon; Lee, Jae-Joon; Shin, Dongbin; Jung, Sun-Min; Seo, Jeong-Min; Kim, Min-Jung; Park, Noejung; Dai, Liming; Baek, Jong-Beom

    2013-07-01

    Nitrogen fixation is essential for the synthesis of many important chemicals (e.g., fertilizers, explosives) and basic building blocks for all forms of life (e.g., nucleotides for DNA and RNA, amino acids for proteins). However, direct nitrogen fixation is challenging as nitrogen (N2) does not easily react with other chemicals. By dry ball-milling graphite with N2, we have discovered a simple, but versatile, scalable and eco-friendly, approach to direct fixation of N2 at the edges of graphene nanoplatelets (GnPs). The mechanochemical cracking of graphitic C-C bonds generated active carbon species that react directly with N2 to form five- and six-membered aromatic rings at the broken edges, leading to solution-processable edge-nitrogenated graphene nanoplatelets (NGnPs) with superb catalytic performance in both dye-sensitized solar cells and fuel cells to replace conventional Pt-based catalysts for energy conversion.

  1. Efficient and selective molecular catalyst for the CO2-to-CO electrochemical conversion in water

    PubMed Central

    Costentin, Cyrille; Robert, Marc; Savéant, Jean-Michel; Tatin, Arnaud

    2015-01-01

    Substitution of the four paraphenyl hydrogens of iron tetraphenylporphyrin by trimethylammonio groups provides a water-soluble molecule able to catalyze the electrochemical conversion of carbon dioxide into carbon monoxide. The reaction, performed in pH-neutral water, forms quasi-exclusively carbon monoxide with very little production of hydrogen, despite partial equilibration of CO2 with carbonic acid—a low pKa acid. This selective molecular catalyst is endowed with a good stability and a high turnover frequency. On this basis, prescribed composition of CO–H2 mixtures can be obtained by adjusting the pH of the solution, optionally adding an electroinactive buffer. The development of these strategies will be greatly facilitated by the fact that one operates in water. The same applies for the association of the cathode compartment with a proton-producing anode by means of a suitable separator. PMID:26038542

  2. Direct nitrogen fixation at the edges of graphene nanoplatelets as efficient electrocatalysts for energy conversion

    PubMed Central

    Jeon, In-Yup; Choi, Hyun-Jung; Ju, Myung Jong; Choi, In Taek; Lim, Kimin; Ko, Jaejung; Kim, Hwan Kyu; Kim, Jae Cheon; Lee, Jae-Joon; Shin, Dongbin; Jung, Sun-Min; Seo, Jeong-Min; Kim, Min-Jung; Park, Noejung; Dai, Liming; Baek, Jong-Beom

    2013-01-01

    Nitrogen fixation is essential for the synthesis of many important chemicals (e.g., fertilizers, explosives) and basic building blocks for all forms of life (e.g., nucleotides for DNA and RNA, amino acids for proteins). However, direct nitrogen fixation is challenging as nitrogen (N2) does not easily react with other chemicals. By dry ball-milling graphite with N2, we have discovered a simple, but versatile, scalable and eco-friendly, approach to direct fixation of N2 at the edges of graphene nanoplatelets (GnPs). The mechanochemical cracking of graphitic C−C bonds generated active carbon species that react directly with N2 to form five- and six-membered aromatic rings at the broken edges, leading to solution-processable edge-nitrogenated graphene nanoplatelets (NGnPs) with superb catalytic performance in both dye-sensitized solar cells and fuel cells to replace conventional Pt-based catalysts for energy conversion. PMID:23877200

  3. Bandwidth efficient coding: Theoretical limits and real achievements. Error control techniques for satellite and space communications

    NASA Technical Reports Server (NTRS)

    Costello, Daniel J., Jr.; Courturier, Servanne; Levy, Yannick; Mills, Diane G.; Perez, Lance C.; Wang, Fu-Quan

    1993-01-01

    In his seminal 1948 paper 'The Mathematical Theory of Communication,' Claude E. Shannon derived the 'channel coding theorem' which has an explicit upper bound, called the channel capacity, on the rate at which 'information' could be transmitted reliably on a given communication channel. Shannon's result was an existence theorem and did not give specific codes to achieve the bound. Some skeptics have claimed that the dramatic performance improvements predicted by Shannon are not achievable in practice. The advances made in the area of coded modulation in the past decade have made communications engineers optimistic about the possibility of achieving or at least coming close to channel capacity. Here we consider the possibility in the light of current research results.

  4. Rationally designed graphene-nanotube 3D architectures with a seamless nodal junction for efficient energy conversion and storage

    PubMed Central

    Xue, Yuhua; Ding, Yong; Niu, Jianbing; Xia, Zhenhai; Roy, Ajit; Chen, Hao; Qu, Jia; Wang, Zhong Lin; Dai, Liming

    2015-01-01

    One-dimensional (1D) carbon nanotubes (CNTs) and 2D single-atomic layer graphene have superior thermal, electrical, and mechanical properties. However, these nanomaterials exhibit poor out-of-plane properties due to the weak van der Waals interaction in the transverse direction between graphitic layers. Recent theoretical studies indicate that rationally designed 3D architectures could have desirable out-of-plane properties while maintaining in-plane properties by growing CNTs and graphene into 3D architectures with a seamless nodal junction. However, the experimental realization of seamlessly-bonded architectures remains a challenge. We developed a strategy of creating 3D graphene-CNT hollow fibers with radially aligned CNTs (RACNTs) seamlessly sheathed by a cylindrical graphene layer through a one-step chemical vapor deposition using an anodized aluminum wire template. By controlling the aluminum wire diameter and anodization time, the length of the RACNTs and diameter of the graphene hollow fiber can be tuned, enabling efficient energy conversion and storage. These fibers, with a controllable surface area, meso-/micropores, and superior electrical properties, are excellent electrode materials for all-solid-state wire-shaped supercapacitors with poly(vinyl alcohol)/H2SO4 as the electrolyte and binder, exhibiting a surface-specific capacitance of 89.4 mF/cm2 and length-specific capacitance up to 23.9 mF/cm, — one to four times the corresponding record-high capacities reported for other fiber-like supercapacitors. Dye-sensitized solar cells, fabricated using the fiber as a counter electrode, showed a power conversion efficiency of 6.8% and outperformed their counterparts with an expensive Pt wire counter electrode by a factor of 2.5. These novel fiber-shaped graphene-RACNT energy conversion and storage devices are so flexible they can be woven into fabrics as power sources. PMID:26601246

  5. Rationally designed graphene-nanotube 3D architectures with a seamless nodal junction for efficient energy conversion and storage.

    PubMed

    Xue, Yuhua; Ding, Yong; Niu, Jianbing; Xia, Zhenhai; Roy, Ajit; Chen, Hao; Qu, Jia; Wang, Zhong Lin; Dai, Liming

    2015-09-01

    One-dimensional (1D) carbon nanotubes (CNTs) and 2D single-atomic layer graphene have superior thermal, electrical, and mechanical properties. However, these nanomaterials exhibit poor out-of-plane properties due to the weak van der Waals interaction in the transverse direction between graphitic layers. Recent theoretical studies indicate that rationally designed 3D architectures could have desirable out-of-plane properties while maintaining in-plane properties by growing CNTs and graphene into 3D architectures with a seamless nodal junction. However, the experimental realization of seamlessly-bonded architectures remains a challenge. We developed a strategy of creating 3D graphene-CNT hollow fibers with radially aligned CNTs (RACNTs) seamlessly sheathed by a cylindrical graphene layer through a one-step chemical vapor deposition using an anodized aluminum wire template. By controlling the aluminum wire diameter and anodization time, the length of the RACNTs and diameter of the graphene hollow fiber can be tuned, enabling efficient energy conversion and storage. These fibers, with a controllable surface area, meso-/micropores, and superior electrical properties, are excellent electrode materials for all-solid-state wire-shaped supercapacitors with poly(vinyl alcohol)/H2SO4 as the electrolyte and binder, exhibiting a surface-specific capacitance of 89.4 mF/cm(2) and length-specific capacitance up to 23.9 mF/cm, - one to four times the corresponding record-high capacities reported for other fiber-like supercapacitors. Dye-sensitized solar cells, fabricated using the fiber as a counter electrode, showed a power conversion efficiency of 6.8% and outperformed their counterparts with an expensive Pt wire counter electrode by a factor of 2.5. These novel fiber-shaped graphene-RACNT energy conversion and storage devices are so flexible they can be woven into fabrics as power sources. PMID:26601246

  6. Enhanced Optoelectronic Conversion Efficiency of CdSe/ZnS Quantum Dot/Graphene/Silver Nanowire Hybrid Thin Films.

    PubMed

    Liu, Bo-Tau; Wu, Kuan-Han; Lee, Rong-Ho

    2016-12-01

    In this study, we prepared the reduced graphene oxide (rGO)-CdSe/ZnS quantum dots (QDs) hybrid films on a three-layer scaffold that the QD layer was sandwiched between the two rGO layers. The photocurrent was induced by virtue of the facts that the rGO quenched the photoluminescence of QDs and transferred the excited energy. The quenching mechanism was attributed to the surface energy transfer, supported in our experimental results. We found that the optoelectronic conversion efficiency of the hybrid films can be significantly improved by incorporating the silver nanowires (AgNWs) into the QD layer. Upon increasing AgNW content, the photocurrent density increased from 22.1 to 80.3 μA cm(-2), reaching a near 3.6-fold enhancement compared to the pristine rGO-QD hybrid films. According to the analyses of photoluminescence spectra, shape effect, and electrochemical impedance spectra, the enhancement on the optoelectronic conversion efficiency arise mainly from the strong quenching ability of silver and the rapid electron transfer of AgNWs. PMID:27599719

  7. Improved conversion efficiency of dye sensitized solar cell using Zn doped TiO2-ZrO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Tomar, Laxmi J.; Bhatt, Piyush J.; Desai, Rahul K.; Chakrabarty, B. S.; Panchal, C. J.

    2016-05-01

    TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites were prepared by hydrothermal method for dye sensitized solar cell (DSSC) application. The structural and optical properties were investigated by X -ray diffraction (XRD) and UV-Visible spectroscopy respectively. XRD results revealed the formation of material in nano size. The average crystallite size is 22.32 nm, 17.41 nm and 6.31 nm for TiO2, TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites respectively. The optical bandgap varies from 2.04 eV to 3.75 eV. Dye sensitized solar cells were fabricated using the prepared material. Pomegranate juice was used as a sensitizer and graphite coated conducting glass plate was used as counter electrode. The I - V characteristics were recorded to measure photo response of DSSC. Photovoltaic parameter like open circuit voltage, power conversion efficiency, and fill factor were evaluated for fabricated solar cell. The power conversion efficiency of DSSC fabricated with TiO2, TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites were found 0.71%, 1.97% and 4.58% respectively.

  8. Opportunities for increasing biomass conversion efficiencies to ethanol by engineering energy crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The United States government has targeted aggressive development of bioethanol as one route for decreasing oil dependence and lowering greenhouse gas emissions. Achieving future production targets depends on expanding feedstock sources beyond corn and towards lignocellulose. This is expected to in...

  9. Large-Scale Nanophotonic Solar Selective Absorbers for High-Efficiency Solar Thermal Energy Conversion.

    PubMed

    Li, Pengfei; Liu, Baoan; Ni, Yizhou; Liew, Kaiyang Kevin; Sze, Jeff; Chen, Shuo; Shen, Sheng

    2015-08-19

    An omnidirectional nanophotonic solar selective absorber is fabricated on a large scale using a template-stripping method. The nanopyramid nickel structure achieves an average absorptance of 95% at a wavelength range below 1.3 μm and a low emittance less than 10% at wavelength >2.5 μm. PMID:26134928

  10. Multiple Exciton Generation in Semiconductor Nanocrystals: Toward Efficient Solar Energy Conversion

    SciTech Connect

    Beard, M. C.; Ellingson, R. J.

    2008-01-01

    Within the range of photon energies illuminating the Earth's surface, absorption of a photon by a conventional photovoltaic semiconductor device results in the production of a single electron-hole pair; energy of a photon in excess of the semiconductor's bandgap is efficiently converted to heat through interactions between the electron and hole with the crystal lattice. Recently, colloidal semiconductor nanocrystals and nanocrystal films have been shown to exhibit efficient multiple electron-hole pair generation from a single photon with energy greater than twice the effective band gap. This multiple carrier pair process, referred to as multiple exciton generation (MEG), represents one route to reducing the thermal loss in semiconductor solar cells and may lead to the development of low cost, high efficiency solar energy devices. We review the current experimental and theoretical understanding of MEG, and provide views to the near-term future for both fundamental research and the development of working devices which exploit MEG.

  11. Study on an environmental-friendly and high-efficient fuel cell energy conversion system.

    PubMed

    Yu, Li-Jun; Cao, Guang-Yi; Zhu, Xin-Jian; Jiang, An-Zhong; Tian, Zi-Ping

    2003-01-01

    The kinds and the distribution of the coal in China are investigated. The results indicated that the 80% coal in China is used by the method of the coal gasification. The possibility of utilization and development of the fuel cell power plant in China is analyzed. A combined cycle generation system is designed. Its net electrical efficiency is about 55% (LHV), which is higher than that of the fire power plant. So it is environmental-friendly and high-efficient generation mode. PMID:12602611

  12. Efficient methane conversion to hydrogen and hydrocarbons by combination of corona and glow discharge

    NASA Astrophysics Data System (ADS)

    Ghorbanzadeh, A. M.; Matin, N. S.

    2004-03-01

    In this study we offer a new type of plasma which consists of double, corona and glow, discharge to convert natural gas, the main part of which is methane. The most important future of this type of plasma is the steady increase of overall chemical energy efficiency by enhancement of repetition rate. At repetition rate of R=80 Hz, the energy efficiency of 5.5% was increased to 10% at R=330 Hz and more improvement was yet expected at higher repetition rates. Easy control of selectivity of products that were hydrogen, acetylene, ethylene, ethane and hydrocarbons with up to 5 carbons, was also possible by repetition rate.

  13. Efficient telecom to visible wavelength conversion in doubly resonant gallium phosphide microdisks

    NASA Astrophysics Data System (ADS)

    Lake, David P.; Mitchell, Matthew; Jayakumar, Harishankar; dos Santos, Laís Fujii; Curic, Davor; Barclay, Paul E.

    2016-01-01

    Resonant second harmonic generation between 1550 nm and 775 nm with normalized outside efficiency > 3.8 × 10 - 4 mW - 1 is demonstrated in a gallium phosphide microdisk supporting high-Q modes at visible ( Q ˜ 10 4 ) and infrared ( Q ˜ 10 5 ) wavelengths. The double resonance condition is satisfied for a specific pump power through intracavity photothermal temperature tuning using ˜ 360 μ W of 1550 nm light input to a fiber taper and coupled to a microdisk resonance. Power dependent efficiency consistent with a simple model for thermal tuning of the double resonance condition is observed.

  14. Improved conversion efficiency of amorphous Si solar cells using a mesoporous ZnO pattern

    PubMed Central

    2014-01-01

    To provide a front transparent electrode for use in highly efficient hydrogenated amorphous silicon (a-Si:H) thin-film solar cells, porous flat layer and micro-patterns of zinc oxide (ZnO) nanoparticle (NP) layers were prepared through ultraviolet nanoimprint lithography (UV-NIL) and deposited on Al-doped ZnO (AZO) layers. Through this, it was found that a porous micro-pattern of ZnO NPs dispersed in resin can optimize the light-trapping pattern, with the efficiency of solar cells based on patterned or flat mesoporous ZnO layers increased by 27% and 12%, respectively. PMID:25276101

  15. Student Achievement and Efficiency in Missouri Schools and the No Child Left Behind Act

    ERIC Educational Resources Information Center

    Primont, Diane F.; Domazlicky, Bruce

    2006-01-01

    The 2001 No Child Left Behind Act requires that schools make ''annual yearly progress'' in raising student achievement, or face possible sanctions. The No Child Left Behind Act places added emphasis on test scores, such as scores from the Missouri Assessment Program (MAP), to evaluate the performance of schools. In this paper, we investigate…

  16. A Thorough and Efficient Education: School Funding, Student Achievement and Productivity

    ERIC Educational Resources Information Center

    Ahlgrim, Richard W.

    2010-01-01

    Many school districts are facing stagnant or reduced funding (input) concurrent with demands for improved student achievement (output). In other words, there is pressure for all schools, even those schools with student populations of low socioeconomic status, to improve academic results (accountability for output) without a directly proportionate…

  17. Langley program of GaAs solar cells. [emphasizing energy conversion efficiency and radiation resistance

    NASA Technical Reports Server (NTRS)

    Conway, E. J.

    1979-01-01

    A brief overview of the development of GaAs solar cell technology is provided. An 18 to 20 percent AMO efficiency, stability under radiation and elevated-temperature operation, and high power-to-weight ratio are among the factors studied. Cell cost and availability are also examined.

  18. 'Squeezing' near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion.

    PubMed

    Karalis, Aristeidis; Joannopoulos, J D

    2016-01-01

    We numerically demonstrate near-field planar ThermoPhotoVoltaic systems with very high efficiency and output power, at large vacuum gaps. Example performances include: at 1200 °K emitter temperature, output power density 2 W/cm(2) with ~47% efficiency at 300 nm vacuum gap; at 2100 °K, 24 W/cm(2) with ~57% efficiency at 200 nm gap; and, at 3000 °K, 115 W/cm(2) with ~61% efficiency at 140 nm gap. Key to this striking performance is a novel photonic design forcing the emitter and cell single modes to cros resonantly couple and impedance-match just above the semiconductor bandgap, creating there a 'squeezed' narrowband near-field emission spectrum. Specifically, we employ surface-plasmon-polariton thermal emitters and silver-backed semiconductor-thin-film photovoltaic cells. The emitter planar plasmonic nature allows for high-power and stable high-temperature operation. Our simulations include modeling of free-carrier absorption in both cell electrodes and temperature dependence of the emitter properties. At high temperatures, the efficiency enhancement via resonant mode cross-coupling and matching can be extended to even higher power, by appropriately patterning the silver back electrode to enforce also an absorber effective surface-plasmon-polariton mode. Our proposed designs can therefore lead the way for mass-producible and low-cost ThermoPhotoVoltaic micro-generators and solar cells. PMID:27363522

  19. Efficient dye regeneration at low driving force achieved in triphenylamine dye LEG4 and TEMPO redox mediator based dye-sensitized solar cells.

    PubMed

    Yang, Wenxing; Vlachopoulos, Nick; Hao, Yan; Hagfeldt, Anders; Boschloo, Gerrit

    2015-06-28

    Minimizing the driving force required for the regeneration of oxidized dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of dye-sensitized solar cells (DSSCs). Appropriate combinations of redox mediators and dye molecules should be explored to achieve this goal. Herein, we present a triphenylamine dye, LEG4, in combination with a TEMPO-based electrolyte in acetonitrile (E(0) = 0.89 V vs. NHE), reaching an efficiency of up to 5.4% under one sun illumination and 40% performance improvement compared to the previously and widely used indoline dye D149. The origin of this improvement was found to be the increased dye regeneration efficiency of LEG4 using the TEMPO redox mediator, which regenerated more than 80% of the oxidized dye with a driving force of only ∼0.2 eV. Detailed mechanistic studies further revealed that in addition to electron recombination to oxidized dyes, recombination of electrons from the conducting substrate and the mesoporous TiO2 film to the TEMPO(+) redox species in the electrolyte accounts for the reduced short circuit current, compared to the state-of-the-art cobalt tris(bipyridine) electrolyte system. The diffusion length of the TEMPO-electrolyte based DSSCs was determined to be ∼0.5 μm, which is smaller than the ∼2.8 μm found for cobalt-electrolyte based DSSCs. These results show the advantages of using LEG4 as a sensitizer, compared to previously record indoline dyes, in combination with a TEMPO-based electrolyte. The low driving force for efficient dye regeneration presented by these results shows the potential to further improve the power conversion efficiency (PCE) of DSSCs by utilizing redox couples and dyes with a minimal need of driving force for high regeneration yields. PMID:26016854

  20. Cobalt phosphate-modified barium-doped tantalum nitride nanorod photoanode with 1.5% solar energy conversion efficiency.

    PubMed

    Li, Yanbo; Zhang, Li; Torres-Pardo, Almudena; González-Calbet, Jose M; Ma, Yanhang; Oleynikov, Peter; Terasaki, Osamu; Asahina, Shunsuke; Shima, Masahide; Cha, Dongkyu; Zhao, Lan; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

    2013-01-01

    Spurred by the decreased availability of fossil fuels and global warming, the idea of converting solar energy into clean fuels has been widely recognized. Hydrogen produced by photoelectrochemical water splitting using sunlight could provide a carbon dioxide lean fuel as an alternative to fossil fuels. A major challenge in photoelectrochemical water splitting is to develop an efficient photoanode that can stably oxidize water into oxygen. Here we report an efficient and stable photoanode that couples an active barium-doped tantalum nitride nanostructure with a stable cobalt phosphate co-catalyst. The effect of barium doping on the photoelectrochemical activity of the photoanode is investigated. The photoanode yields a maximum solar energy conversion efficiency of 1.5%, which is more than three times higher than that of state-of-the-art single-photon photoanodes. Further, stoichiometric oxygen and hydrogen are stably produced on the photoanode and the counter electrode with Faraday efficiency of almost unity for 100 min. PMID:24089138

  1. Achieving strategic cost advantages by focusing on back-office efficiency.

    PubMed

    McDowell, Jim

    2010-06-01

    A study of more than 270 hospitals over a four-year period highlighted a number of investments that can reduce hospitals' costs and improve efficiency, including the following: E-procurement systems. Electronic exchange of invoices and payments (and electronic receipt of payments). Human resources IT systems that reduce the need for manual entry of data. Shared services deployment. PMID:20533684

  2. Achieving high performance polymer optoelectronic devices for high efficiency, long lifetime and low fabrication cost

    NASA Astrophysics Data System (ADS)

    Huang, Jinsong

    This thesis described three types of organic optoelectronic devices: polymer light emitting diodes (PLED), polymer photovoltaic solar cell, and organic photo detector. The research in this work focuses improving their performance including device efficiency, operation lifetime simplifying fabrication process. With further understanding in PLED device physics, we come up new device operation model and improved device architecture design. This new method is closely related to understanding of the science and physics at organic/metal oxide and metal oxide/metal interface. In our new device design, both material and interface are considered in order to confine and balance all injected carriers, which has been demonstrated very be successful in increasing device efficiency. We created two world records in device efficiency: 18 lm/W for white emission fluorescence PLED, 22 lm/W for red emission phosphorescence PLED. Slow solvent drying process has been demonstrated to significantly increase device efficiency in poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C 61-butyric acid methyl ester (PCBM) mixture polymer solar cell. From the mobility study by time of flight, the increase of efficiency can be well correlated to the improved carrier transport property due to P3HT crystallization during slow solvent drying. And it is found that, similar to PLED, balanced carrier mobility is essential in high efficient polymer solar cell. There is also a revolution in our device fabrication method. A unique device fabrication method is presented by an electronic glue based lamination process combined with interface modification as a one-step polymer solar cell fabrication process. It can completely skip the thermal evaporation process, and benefit device lifetime by several merits: no air reactive. The device obtained is metal free, semi-transparent, flexible, self-encapsulated, and comparable efficiency with that by regular method. We found the photomultiplication (PM) phenomenon in C

  3. Lipase cocktail for efficient conversion of oils containing phospholipids to biodiesel.

    PubMed

    Amoah, Jerome; Ho, Shih-Hsin; Hama, Shinji; Yoshida, Ayumi; Nakanishi, Akihito; Hasunuma, Tomohisa; Ogino, Chiaki; Kondo, Akihiko

    2016-07-01

    The presence of phospholipid has been a challenge in liquid enzymatic biodiesel production. Among six lipases that were screened, lipase AY had the highest hydrolysis activity and a competitive transesterification activity. However, it yielded only 21.1% FAME from oil containing phospholipids. By replacing portions of these lipases with a more robust bioFAME lipase, CalT, the combination of lipase AY-CalT gave the highest FAME yield with the least amounts of free fatty acids and partial glycerides. A higher methanol addition rate reduced FAME yields for lipase DF-CalT and A10D-CalT combinations while that of lipase AY-CalT combination improved. Optimizing the methanol addition rate for lipase AY-CalT resulted in a FAME yield of 88.1% at 2h and more than 95% at 6h. This effective use of lipases could be applied for the rapid and economic conversion of unrefined oils to biodiesel. PMID:27019125

  4. Efficient Photoelectrochemical Energy Conversion using Spinach Photosystem II (PSII) in Lipid Multilayer Films.

    PubMed

    Zhang, Yun; Magdaong, Nikki M; Shen, Min; Frank, Harry A; Rusling, James F

    2015-04-01

    The need for clean, renewable energy has fostered research into photovoltaic alternatives to silicon solar cells. Pigment-protein complexes in green plants convert light energy into chemical potential using redox processes that produce molecular oxygen. Here, we report the first use of spinach protein photosystem II (PSII) core complex in lipid films in photoelectrochemical devices. Photocurrents were generated from PSII in a ∼2 μm biomimetic dimyristoylphosphatidylcholine (DMPC) film on a pyrolytic graphite (PG) anode with PSII embedded in multiple lipid bilayers. The photocurrent was ∼20 μA cm(-2) under light intensity 40 mW cm(-2). The PSII-DMPC anode was used in a photobiofuel cell with a platinum black mesh cathode in perchloric acid solution to give an output voltage of 0.6 V and a maximum output power of 14 μW cm(-2). Part of this large output is related to a five-unit anode-cathode pH gradient. With catholytes at higher pH or no perchlorate, or using an MnO2 oxygen-reduction cathode, the power output was smaller. The results described raise the possibility of using PSII-DMPC films in small portable power conversion devices. PMID:25969807

  5. Scalable, efficient ASICS for the square kilometre array: From A/D conversion to central correlation

    NASA Astrophysics Data System (ADS)

    Schmatz, M. L.; Jongerius, R.; Dittmann, G.; Anghel, A.; Engbersen, T.; van Lunteren, J.; Buchmann, P.

    2014-05-01

    The Square Kilometre Array (SKA) is a future radio telescope, currently being designed by the worldwide radio-astronomy community. During the first of two construction phases, more than 250,000 antennas will be deployed, clustered in aperture-array stations. The antennas will generate 2.5 Pb/s of data, which needs to be processed in real time. For the processing stages from A/D conversion to central correlation, we propose an ASIC solution using only three chip architectures. The architecture is scalable - additional chips support additional antennas or beams - and versatile - it can relocate its receiver band within a range of a few MHz up to 4GHz. This flexibility makes it applicable to both SKA phases 1 and 2. The proposed chips implement an antenna and station processor for 289 antennas with a power consumption on the order of 600W and a correlator, including corner turn, for 911 stations on the order of 90 kW.

  6. Efficient Photoelectrochemical Energy Conversion using Spinach Photosystem II (PSII) in Lipid Multilayer Films

    PubMed Central

    Zhang, Yun; Magdaong, Nikki M; Shen, Min; Frank, Harry A; Rusling, James F

    2015-01-01

    The need for clean, renewable energy has fostered research into photovoltaic alternatives to silicon solar cells. Pigment–protein complexes in green plants convert light energy into chemical potential using redox processes that produce molecular oxygen. Here, we report the first use of spinach protein photosystem II (PSII) core complex in lipid films in photoelectrochemical devices. Photocurrents were generated from PSII in a ∼2 μm biomimetic dimyristoylphosphatidylcholine (DMPC) film on a pyrolytic graphite (PG) anode with PSII embedded in multiple lipid bilayers. The photocurrent was ∼20 μA cm−2 under light intensity 40 mW cm−2. The PSII–DMPC anode was used in a photobiofuel cell with a platinum black mesh cathode in perchloric acid solution to give an output voltage of 0.6 V and a maximum output power of 14 μW cm−2. Part of this large output is related to a five-unit anode–cathode pH gradient. With catholytes at higher pH or no perchlorate, or using an MnO2 oxygen-reduction cathode, the power output was smaller. The results described raise the possibility of using PSII–DMPC films in small portable power conversion devices. PMID:25969807

  7. Revisiting Morrison and Osterle 1965: the efficiency of membrane-based electrokinetic energy conversion.

    PubMed

    Catalano, J; Hamelers, H V M; Bentien, A; Biesheuvel, P M

    2016-08-17

    We revisit Morrison and Osterle (1965) who derived a phenomenological expression for the 'figure-of-merit' [Formula: see text] of the electrokinetic energy conversion (EKEC) of a pressure difference into electric energy (and vice versa) using charged nanotubes, nanopores or ion-exchange membranes. We show the equivalence with Morrison and Osterle of a novel expression of [Formula: see text] derived by Bentien et al (2013). We analyze two physical models for ionic and solvent flow which directly relate [Formula: see text] to nanopore characteristics such as pore size and wall charge density. For the uniform potential model, we derive an analytical expression as a function of pore size, viscosity, ion diffusion coefficients and membrane charge density, and compare results with the full space-charge model by Osterle and co-workers as a function of pore size and ion diffusion coefficient. We present a novel expression for [Formula: see text] for salt solutions with ions with unequal diffusion coefficients (mobilities) and show that to increase [Formula: see text] the counterion mobility must be low and the coion mobility high. PMID:27321823

  8. Revisiting Morrison and Osterle 1965: the efficiency of membrane-based electrokinetic energy conversion

    NASA Astrophysics Data System (ADS)

    Catalano, J.; Hamelers, H. V. M.; Bentien, A.; Biesheuvel, P. M.

    2016-08-01

    We revisit Morrison and Osterle (1965) who derived a phenomenological expression for the ‘figure-of-merit’ {β\\text{EK}} of the electrokinetic energy conversion (EKEC) of a pressure difference into electric energy (and vice versa) using charged nanotubes, nanopores or ion-exchange membranes. We show the equivalence with Morrison and Osterle of a novel expression of {β\\text{EK}} derived by Bentien et al (2013). We analyze two physical models for ionic and solvent flow which directly relate {β\\text{EK}} to nanopore characteristics such as pore size and wall charge density. For the uniform potential model, we derive an analytical expression as a function of pore size, viscosity, ion diffusion coefficients and membrane charge density, and compare results with the full space-charge model by Osterle and co-workers as a function of pore size and ion diffusion coefficient. We present a novel expression for {β\\text{EK}} for salt solutions with ions with unequal diffusion coefficients (mobilities) and show that to increase {β\\text{EK}} the counterion mobility must be low and the coion mobility high.

  9. Efficient conversion of xylose to ethanol by stress-tolerant Kluyveromyces marxianus BUNL-21.

    PubMed

    Nitiyon, Sukanya; Keo-Oudone, Chansom; Murata, Masayuki; Lertwattanasakul, Noppon; Limtong, Savitree; Kosaka, Tomoyuki; Yamada, Mamoru

    2016-01-01

    The fermentation ability of thermotolerant Kluyveromyces marxianus BUNL-21 isolated in Laos was investigated. Comparison with thermotolerant K. marxianus DMKU3-1042 as one of the most thermotolerant yeasts isolated previously revealed that the strain possesses stronger ability for conversion of xylose to ethanol, resistance to 2-deoxyglucose in the case of pentose, and tolerance to various stresses including high temperature and hydrogen peroxide. K. marxianus BUNL-21 was found to have ethanol fermentation activity from xylose that is slightly lower and much higher than that of Scheffersomyces stipitis (Pichia stipitis) at 30 °C and at higher temperatures, respectively. The lower ethanol production seems to be due to large accumulation of acetic acid. The possible mechanism of acetic acid accumulation is discussed. In addition, it was found that both K. marxianus strains produced ethanol in the presence of 10 mM hydroxymethylfurfural or furfural, at a level almost equivalent to that in their absence. Therefore, K. marxianus BUNL-21 is a highly competent yeast for high-temperature ethanol fermentation with lignocellulosic biomass. PMID:27026881

  10. PAF-derived nitrogen-doped 3D Carbon Materials for Efficient Energy Conversion and Storage

    PubMed Central

    Xiang, Zhonghua; Wang, Dan; Xue, Yuhua; Dai, Liming; Chen, Jian-Feng; Cao, Dapeng

    2015-01-01

    Owing to the shortage of the traditional fossil fuels caused by fast consumption, it is an urgent task to develop the renewable and clean energy sources. Thus, advanced technologies for both energy conversion (e.g., solar cells and fuel cells) and storage (e.g., supercapacitors and batteries) are being studied extensively. In this work, we use porous aromatic framework (PAF) as precursor to produce nitrogen-doped 3D carbon materials, i.e., N-PAF-Carbon, by exposing NH3 media. The “graphitic” and “pyridinic” N species, large surface area, and similar pore size as electrolyte ions endow the nitrogen-doped PAF-Carbon with outstanding electronic performance. Our results suggest the N-doping enhance not only the ORR electronic catalysis but also the supercapacitive performance. Actually, the N-PAF-Carbon obtains ~70 mV half-wave potential enhancement and 80% increase as to the limiting current after N doping. Moreover, the N-PAF-Carbon displays free from the CO and methanol crossover effect and better long-term durability compared with the commercial Pt/C benchmark. Moreover, N-PAF-Carbon also possesses large capacitance (385 F g−1) and excellent performance stability without any loss in capacitance after 9000 charge–discharge cycles. These results clearly suggest that PAF-derived N-doped carbon material is promising metal-free ORR catalyst for fuel cells and capacitor electrode materials. PMID:26045229

  11. 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.

  12. Elementary Mode Analysis for the Rational Design of Efficient Succinate Conversion from Glycerol by Escherichia coli

    PubMed Central

    Chen, Zhen; Liu, Hongjuan; Zhang, Jianan; Liu, Dehua

    2010-01-01

    By integrating the restriction of oxygen and redox sensing/regulatory system, elementary mode analysis was used to predict the metabolic potential of glycerol for succinate production by E. coli under either anaerobic or aerobic conditions. It was found that although the theoretical maximum succinate yields under both anaerobic and aerobic conditions are 1.0 mol/mol glycerol, the aerobic condition was considered to be more favorable for succinate production. Although increase of the oxygen concentration would reduce the succinate yield, the calculation suggests that controlling the molar fraction of oxygen to be under 0.65 mol/mol would be beneficial for increasing the succinate productivity. Based on the elementary mode analysis, the rational genetic modification strategies for efficient succinate production under aerobic and anaerobic conditions were obtained, respectively. Overexpressing the phosphoenolpyruvate carboxylase or heterogonous pyruvate carboxylase is considered to be the most efficient strategy to increase the succinate yield. PMID:20886007

  13. Three-terminal heterojunction bipolar transistor solar cell for high-efficiency photovoltaic conversion

    PubMed Central

    Martí, A.; Luque, A.

    2015-01-01

    Here we propose, for the first time, a solar cell characterized by a semiconductor transistor structure (n/p/n or p/n/p) where the base–emitter junction is made of a high-bandgap semiconductor and the collector is made of a low-bandgap semiconductor. We calculate its detailed-balance efficiency limit and prove that it is the same one than that of a double-junction solar cell. The practical importance of this result relies on the simplicity of the structure that reduces the number of layers that are required to match the limiting efficiency of dual-junction solar cells without using tunnel junctions. The device naturally emerges as a three-terminal solar cell and can also be used as building block of multijunction solar cells with an increased number of junctions. PMID:25902374

  14. Three-terminal heterojunction bipolar transistor solar cell for high-efficiency photovoltaic conversion.

    PubMed

    Martí, A; Luque, A

    2015-01-01

    Here we propose, for the first time, a solar cell characterized by a semiconductor transistor structure (n/p/n or p/n/p) where the base-emitter junction is made of a high-bandgap semiconductor and the collector is made of a low-bandgap semiconductor. We calculate its detailed-balance efficiency limit and prove that it is the same one than that of a double-junction solar cell. The practical importance of this result relies on the simplicity of the structure that reduces the number of layers that are required to match the limiting efficiency of dual-junction solar cells without using tunnel junctions. The device naturally emerges as a three-terminal solar cell and can also be used as building block of multijunction solar cells with an increased number of junctions. PMID:25902374

  15. Enhanced up/down-conversion luminescence and heat: Simultaneously achieving in one single core-shell structure for multimodal imaging guided therapy.

    PubMed

    He, Fei; Feng, Lili; Yang, Piaoping; Liu, Bin; Gai, Shili; Yang, Guixin; Dai, Yunlu; Lin, Jun

    2016-10-01

    Upon near-infrared (NIR) light irradiation, the Nd(3+) doping derived down-conversion luminescence (DCL) in NIR region and thermal effect are extremely fascinating in bio-imaging and photothermal therapy (PTT) fields. However, the concentration quenching induced opposite changing trend of the two properties makes it difficult to get desired DCL and thermal effect together in one single particle. In this study, we firstly designed a unique NaGdF4:0.3%Nd@NaGdF4@NaGdF4:10%Yb/1%Er@NaGdF4:10%Yb @NaNdF4:10%Yb multiple core-shell structure. Here the inert two layers (NaGdF4 and NaGdF4:10%Yb) can substantially eliminate the quenching effects, thus achieving markedly enhanced NIR-to-NIR DCL, NIR-to-Vis up-conversion luminescence (UCL), and thermal effect under a single 808 nm light excitation simultaneously. The UCL excites the attached photosensitive drug (Au25 nanoclusters) to generate singlet oxygen ((1)O2) for photodynamic therapy (PDT), while DCL with strong NIR emission serves as probe for sensitive deep-tissue imaging. The in vitro and in vivo experimental results demonstrate the excellent cancer inhibition efficacy of this platform due to a synergistic effect arising from the combined PTT and PDT. Furthermore, multimodal imaging including fluorescence imaging (FI), photothermal imaging (PTI), and photoacoustic imaging (PAI) has been obtained, which is used to monitor the drug delivery process, internal structure of tumor and photo-therapeutic process, thus achieving the target of imaging-guided cancer therapy. PMID:27512942

  16. More Efficient Power Conversion for EVs: Gallium-Nitride Advanced Power Semiconductor and Packaging

    SciTech Connect

    2010-02-01

    Broad Funding Opportunity Announcement Project: Delphi is developing power converters that are smaller and more energy efficient, reliable, and cost-effective than current power converters. Power converters rely on power transistors which act like a very precisely controlled on-off switch, controlling the electrical energy flowing through an electrical circuit. Most power transistors today use silicon (Si) semiconductors. However, Delphi is using semiconductors made with a thin layer of gallium-nitride (GaN) applied on top of the more conventional Si material. The GaN layer increases the energy efficiency of the power transistor and also enables the transistor to operate at much higher temperatures, voltages, and power-density levels compared to its Si counterpart. Delphi is packaging these high-performance GaN semiconductors with advanced electrical connections and a cooling system that extracts waste heat from both sides of the device to further increase the device’s efficiency and allow more electrical current to flow through it. When combined with other electronic components on a circuit board, Delphi’s GaN power transistor package will help improve the overall performance and cost-effectiveness of HEVs and EVs.

  17. Identification of Energy Efficiency Opportunities through Building Data Analysis and Achieving Energy Savings through Improved Controls

    SciTech Connect

    Katipamula, Srinivas; Taasevigen, Danny J.; Koran, Bill

    2014-09-04

    This chapter will highlight analysis techniques to identify energy efficiency opportunities to improve operations and controls. A free tool, Energy Charting and Metrics (ECAM), will be used to assist in the analysis of whole-building, sub-metered, and/or data from the building automation system (BAS). Appendix A describes the features of ECAM in more depth, and also provide instructions for downloading ECAM and all resources pertaining to using ECAM.

  18. SIU-based modification in Kelley's measure of skewness to achieve gains in efficiency

    NASA Astrophysics Data System (ADS)

    Habibullah, Saleha Naghmi; Shan-E-Fatima, Syeda

    2015-02-01

    The importance of accurate modeling of life-lengths of components and systems cannot be over-emphasized. Some well-known distributions such as the Birnbaum Saunders distribution extensively used in Reliability Theory are known to fulfill the self-inversion property, the term `Self-Inverse at Unity' (`SIU') implying that, for a random variable X, the distribution of 1/ X is identical to the distribution of X. Very recently, it has been demonstrated the advantage that can be drawn from the SIU property by proposing a modification to the well-known formula of the empirical cumulative distribution function to obtain an estimator of the cumulative distribution function that is more efficient than the empirical cumulative distribution function in situations where the parent population can be assumed to be SIU. Subsequently, a number of papers have appeared proposing SIU-based modifications to the formulae of well-known estimators of central tendency, dispersion and kurtosis that are likely to yield gains in efficiency on account of an approach very similar to the one adopted for the modification of the formula of the empirical cumulative distribution function. In this paper, we propose SIU-based modification to Kelley's Measure of Skewness and, through a simulation study, demonstrate the potential of the proposed formula in improving the efficiency of the estimation process which, obviously, has important implications for accurate modeling of life-data encountered in various branches of engineering.

  19. Artificial perfect electric conductor-perfect magnetic conductor anisotropic metasurface for generating orbital angular momentum of microwave with nearly perfect conversion efficiency

    NASA Astrophysics Data System (ADS)

    Chen, Menglin L. N.; Jiang, Li Jun; Sha, Wei E. I.

    2016-02-01

    Orbital angular momentum (OAM) is a promising degree of freedom for fundamental studies in electromagnetics and quantum mechanics. The unlimited state space of OAM shows a great potential to enhance channel capacities of classical and quantum communications. By exploring the Pancharatnam-Berry phase concept and engineering anisotropic scatterers in a metasurface with spatially varying orientations, a plane wave with zero OAM can be converted to a vortex beam carrying nonzero OAM. In this paper, we proposed two types of novel perfect electric conductor-perfect magnetic conductor anisotropic metasurfaces. One is composed of azimuthally continuous loops and the other is constructed by azimuthally discontinuous dipole scatterers. Both types of metasurfaces are mounted on a mushroom-type high impedance surface. Compared to previous metasurface designs for generating OAM, the proposed ones achieve nearly perfect conversion efficiency. In view of the eliminated vertical component of electric field, the continuous metasurface shows very smooth phase pattern at the near-field region, which cannot be achieved by convectional metasurfaces composed of discrete scatterers. On the other hand, the metasurface with discrete dipole scatterers shows a great flexibility to generate OAM with arbitrary topological charges. Our work is fundamentally and practically important to high-performance OAM generation.

  20. The affect of erbium hydride on the conversion efficience to accelerated protons from ultra-shsort pulse laser irradiated foils

    SciTech Connect

    Offermann, Dustin Theodore

    2008-01-01

    This thesis work explores, experimentally, the potential gains in the conversion efficiency from ultra-intense laser light to proton beams using erbium hydride coatings. For years, it has been known that contaminants at the rear surface of an ultra-intense laser irradiated thin foil will be accelerated to multi-MeV. Inertial Confinement Fusion fast ignition using proton beams as the igniter source requires of about 1016 protons with an average energy of about 3MeV. This is far more than the 1012 protons available in the contaminant layer. Target designs must include some form of a hydrogen rich coating that can be made thick enough to support the beam requirements of fast ignition. Work with computer simulations of thin foils suggest the atomic mass of the non-hydrogen atoms in the surface layer has a strong affect on the conversion efficiency to protons. For example, the 167amu erbium atoms will take less energy away from the proton beam than a coating using carbon with a mass of 12amu. A pure hydrogen coating would be ideal, but technologically is not feasible at this time. In the experiments performed for my thesis, ErH3 coatings on 5 μm gold foils are compared with typical contaminants which are approximately equivalent to CH1.7. It will be shown that there was a factor of 1.25 ± 0.19 improvement in the conversion efficiency for protons above 3MeV using erbium hydride using the Callisto laser. Callisto is a 10J per pulse, 800nm wavelength laser with a pulse duration of 200fs and can be focused to a peak intensity of about 5 x 1019W/cm2. The total number of protons from either target type was on the order of 1010. Furthermore, the same experiment was performed on the Titan laser, which has a 500fs pulse duration, 150J of energy and can be focused to about 3 x 1020 W/cm2. In this experiment 1012 protons were seen from both erbium hydride and

  1. The effect of erbium hydride on the conversion efficiency to accelerated protons from ultra-short pulse laser irradiated foils

    NASA Astrophysics Data System (ADS)

    Offermann, Dustin Theodore

    This thesis work explores, experimentally, the potential gains in the conversion efficiency from ultra-intense laser light to proton beams using erbium hydride coatings. For years, it has been known that contaminants at the rear surface of an ultra-intense laser irradiated thin foil will be accelerated to multi-MeV. Inertial Confinement Fusion fast ignition using proton beams as the igniter source requires of about 10 16 protons with an average energy of about 3MeV. This is far more than the 1012 protons available in the contaminant layer. Target designs must include some form of a hydrogen rich coating that can be made thick enough to support the beam requirements of fast ignition. Work with computer simulations of thin foils suggest the atomic mass of the non-hydrogen atoms in the surface layer has a strong affect on the conversion efficiency to protons. For example, the 167amu erbium atoms will take less energy away from the proton beam than a coating using carbon with a mass of 12amu. A pure hydrogen coating would be ideal, but technologically is not feasible at this time. In the experiments performed for my thesis, ErH 3 coatings on 5mum gold foils are compared with typical contaminants which are approximately equivalent to CH 1.7. It will be shown that there was a factor of 1.25 +/- 0.19 improvement in the conversion efficiency for protons above 3MeV using erbium hydride using the Callisto laser. Callisto is a 10J per pulse, 800nm wavelength laser with a pulse duration of 200fs and can be focused to a peak intensity of about 5 x 1019W/cm2. The total number of protons from either target type was on the order of 1010. Furthermore, the same experiment was performed on the Titan laser, which has a 500fs pulse duration, 150J of energy and can be focused to about 3 x 1020W/cm 2. In this experiment 1012 protons were seen from both erbium hydride and contaminants on 14mum gold foils. Significant improvements were also observed but possibly because of the depletion of

  2. Exciton Lifetime Paradoxically Enhanced by Dissipation and Decoherence: Toward Efficient Energy Conversion of a Solar Cell

    NASA Astrophysics Data System (ADS)

    Yamada, Yasuhiro; Yamaji, Youhei; Imada, Masatoshi

    2015-11-01

    Energy dissipation and decoherence are at first glance harmful to acquiring the long exciton lifetime desired for efficient photovoltaics. In the presence of both optically forbidden (namely, dark) and allowed (bright) excitons, however, they can be instrumental, as suggested in photosynthesis. By simulating the quantum dynamics of exciton relaxations, we show that the optimized decoherence that imposes a quantum-to-classical crossover with the dissipation realizes a dramatically longer lifetime. In an example of a carbon nanotube, the exciton lifetime increases by nearly 2 orders of magnitude when the crossover triggers a stable high population in the dark excitons.

  3. Design techniques for modular integrated utility systems. [energy production and conversion efficiency

    NASA Technical Reports Server (NTRS)

    Wolfer, B. M.

    1977-01-01

    Features basic to the integrated utility system, such as solid waste incineration, heat recovery and usage, and water recycling/treatment, are compared in terms of cost, fuel conservation, and efficiency to conventional utility systems in the same mean-climatic area of Washington, D. C. The larger of the two apartment complexes selected for the test showed the more favorable results in the three areas of comparison. Restrictions concerning the sole use of currently available technology are hypothetically removed to consider the introduction and possible advantages of certain advanced techniques in an integrated utility system; recommendations are made and costs are estimated for each type of system.

  4. Exciton Lifetime Paradoxically Enhanced by Dissipation and Decoherence: Toward Efficient Energy Conversion of a Solar Cell.

    PubMed

    Yamada, Yasuhiro; Yamaji, Youhei; Imada, Masatoshi

    2015-11-01

    Energy dissipation and decoherence are at first glance harmful to acquiring the long exciton lifetime desired for efficient photovoltaics. In the presence of both optically forbidden (namely, dark) and allowed (bright) excitons, however, they can be instrumental, as suggested in photosynthesis. By simulating the quantum dynamics of exciton relaxations, we show that the optimized decoherence that imposes a quantum-to-classical crossover with the dissipation realizes a dramatically longer lifetime. In an example of a carbon nanotube, the exciton lifetime increases by nearly 2 orders of magnitude when the crossover triggers a stable high population in the dark excitons. PMID:26588415

  5. Broiler ascites syndrome: collateral damage from efficient feed to meat conversion.

    PubMed

    Kalmar, Isabelle D; Vanrompay, Daisy; Janssens, Geert P J

    2013-08-01

    Chickens have been raised as food for human consumption for over 4000 years. Over this time they have been continuously selected for specific desirable characteristics by active selection of parents to produce birds which fit perceived needs. Despite this long history of selective breeding and improvements in rearing techniques, the efficiency with which broiler meat is produced has shown a remarkable leap in recent decades. Persistent selection for rapid growth, high feed utilisation efficiency and large cut yield has resulted in modern meat-type poultry lines with superior genetic potential with regard to productivity. However, mortality and the incidence of metabolic diseases has increased in parallel with growth rate. One such disease is broiler ascites syndrome, which has been shown to be closely associated with the fast growth and high meat yield resulting from intense selection and with modern rearing techniques. The review is focused on the historical background, pathogenesis, epidemiology and prevention of broiler ascites syndrome in modern broiler production. PMID:23628419

  6. Simple measurements reveal the feeding history, the onset of reproduction, and energy conversion efficiencies in captive bluefin tuna

    NASA Astrophysics Data System (ADS)

    Jusup, Marko; Klanjšček, Tin; Matsuda, Hiroyuki

    2014-11-01

    We present a numerical approach that, in conjunction with a fully set up Dynamic Energy Budget (DEB) model, aims at consistently approximating the feeding history of cultivated fish from the commonly measured aquaculture data (body length, body mass, or the condition factor). We demonstrate the usefulness of the approach by performing validation of a DEB-based model for Pacific bluefin tuna (Thunnus orientalis) on an independent dataset and exploring the implied bioenergetics of this species in captivity. In the context of validation, the results indicate that the model successfully accounts for more than 75% of the variance in actual fish feed. At the 5% significance level, predictions do not underestimate nor overestimate observations and there is no bias. The overall model accuracy of 87.6% is satisfactory. In the context of tuna bioenergetics, we offer an explanation as to why the first reproduction in the examined case occurred only after the fish reached seven years of age, whereas it takes five years in the wild and sometimes as little as three years in captivity. Finally, we calculate energy conversion efficiencies and the supply stress throughout the entire lifetime to theoretically underpin the relatively low contribution of growth to aerobic metabolism implied by respirometry and high feed conversion ratio observed in bluefin tuna aquaculture.

  7. Optimal thickness of silicon membranes to achieve maximum thermoelectric efficiency: A first principles study

    NASA Astrophysics Data System (ADS)

    Mangold, Claudia; Neogi, Sanghamitra; Donadio, Davide

    2016-08-01

    Silicon nanostructures with reduced dimensionality, such as nanowires, membranes, and thin films, are promising thermoelectric materials, as they exhibit considerably reduced thermal conductivity. Here, we utilize density functional theory and Boltzmann transport equation to compute the electronic properties of ultra-thin crystalline silicon membranes with thickness between 1 and 12 nm. We predict that an optimal thickness of ˜7 nm maximizes the thermoelectric figure of merit of membranes with native oxide surface layers. Further thinning of the membranes, although attainable in experiments, reduces the electrical conductivity and worsens the thermoelectric efficiency.

  8. Improved conversion efficiency of Ag2S quantum dot-sensitized solar cells based on TiO2 nanotubes with a ZnO recombination barrier layer

    PubMed Central

    2011-01-01

    We improve the conversion efficiency of Ag2S quantum dot (QD)-sensitized TiO2 nanotube-array electrodes by chemically depositing ZnO recombination barrier layer on plain TiO2 nanotube-array electrodes. The optical properties, structural properties, compositional analysis, and photoelectrochemistry properties of prepared electrodes have been investigated. It is found that for the prepared electrodes, with increasing the cycles of Ag2S deposition, the photocurrent density and the conversion efficiency increase. In addition, as compared to the Ag2S QD-sensitized TiO2 nanotube-array electrode without the ZnO layers, the conversion efficiency of the electrode with the ZnO layers increases significantly due to the formation of efficient recombination layer between the TiO2 nanotube array and electrolyte. PMID:21777458

  9. High-resolution mapping of the energy conversion efficiency of solar cells and silicon photodiodes in photovoltaic mode

    NASA Astrophysics Data System (ADS)

    Cemine, Vernon Julius; Sarmiento, Raymund; Blanca, Carlo Mar

    2008-11-01

    We demonstrate an optical technique to derive the two-dimensional energy conversion efficiency ( ηCE), fill factor (FF) and external quantum efficiency ( ηQE) distributions across the surface of photovoltaic devices. A compact, inexpensive optical-feedback laser diode microscope is constructed to acquire the confocal reflectance and efficiency maps enabling the observation of the local parametric behavior in silicon photodiodes in photovoltaic mode and single-junction solar cells. The ηCE and ηQE distributions are greatly influenced by local parasitic resistances that depend on laser irradiance. These parasitic resistances decrease the ηCE and ηQE values with distance from the contact electrode at high laser irradiance. The optical technique enables microscopic comparison of ηCE and ηQE within the pn-overlay region of the photodiode sample, revealing its optimization for photodetection rather than power generation. The technique also elucidates the decreasing local ηCE of the solar cell under intense irradiation.

  10. Characterization of deliberately nickel-doped silicon wafers and solar cells. [microstructure, electrical properties, and energy conversion efficiency

    NASA Technical Reports Server (NTRS)

    Salama, A. M.

    1980-01-01

    Microstructural and electrical evaluation tests were performed on nickel-doped p-type silicon wafers before and after solar cell fabrication. The concentration levels of nickel in silicon were 5 x 10 to the 14th power, 4 x 10 to the 15th power, and 8 x 10 to the 15th power atoms/cu cm. It was found that nickel precipitated out during the growth process in all three ingots. Clumps of precipitates, some of which exhibited star shape, were present at different depths. If the clumps are distributed at depths approximately 20 micron apart and if they are larger than 10 micron in diameter, degradation occurs in solar cell electrical properties and cell conversion efficiency. The larger the size of the precipitate clump, the greater the degradation in solar cell efficiency. A large grain boundary around the cell effective area acted as a gettering center for the precipitates and impurities and caused improvement in solar cell efficiency. Details of the evaluation test results are given.

  11. Improved Energy Conversion Efficiency in Wide-Bandgap Cu(In,Ga)Se2 Solar Cells: Preprint

    SciTech Connect

    Contreras, M.; Mansfield, L.; Egaas, B.; Li, J.; Romero, M.; Noufi, R.; Rudiger-Voigt, E.; Mannstadt, W.

    2011-07-01

    This report outlines improvements to the energy conversion efficiency in wide bandgap (Eg>1.2 eV) solar cells based on CuIn1-xGaxSe2. Using (a) alkaline containing high temperature glass substrates, (b) elevated substrate temperatures 600˚C-650˚C and (c) high vacuum evaporation from elemental sources following NREL's three-stage process, we have been able to improve the performance of wider bandgap solar cells with 1.2efficiencies >18% for absorber bandgaps ~1.30 eV and efficiencies ~16% for bandgaps up to ~1.45 eV. In comparing J-V parameters in similar materials, we establish gains in the open-circuit voltage and, to a lesser degree, the fill factor value, as the reason for the improved performance. The higher voltages seen in these wide gap materials grown at high substrate temperatures may be due to reduced recombination at the grain boundary of such absorber films. Solar cell results, absorber materials characterization, and experimental details are reported.

  12. Resource limits and conversion efficiency with implications for climate change and California's energy supply

    NASA Astrophysics Data System (ADS)

    Croft, Gregory Donald

    There are two commonly-used approaches to modeling the future supply of mineral resources. One is to estimate reserves and compare the result to extraction rates, and the other is to project from historical time series of extraction rates. Perceptions of abundant oil supplies in the Middle East and abundant coal supplies in the United States are based on the former approach. In both of these cases, an approach based on historical production series results in a much smaller resource estimate than aggregate reserve numbers. This difference is not systematic; natural gas production in the United States shows a strong increasing trend even though modest reserve estimates have resulted in three decades of worry about the gas supply. The implication of a future decline in Middle East oil production is that the market for transportation fuels is facing major changes, and that alternative fuels should be analyzed in this light. Because the U.S. holds very large coal reserves, synthesizing liquid hydrocarbons from coal has been suggested as an alternative fuel supply. To assess the potential of this process, one has to look at both the resource base and the net efficiency. The three states with the largest coal production declines in the 1996 to 2006 period are among the top 5 coal reserve holders, suggesting that gross coal reserves are a poor indicator of future production. Of the three categories of coal reserves reported by the U.S. Energy Information Administration, reserves at existing mines is the narrowest category and is approximately the equivalent of proved developed oil reserves. By this measure, Wyoming has the largest coal reserves in the U.S., and it accounted for all of U.S. coal production growth over the 1996 to 2006 time period. In Chapter 2, multi-cycle Hubbert curve analysis of historical data of coal production from 1850 to 2007 demonstrates that U.S. anthracite and bituminous coal are past their production peak. This result contradicts estimates based

  13. Resource limits and conversion efficiency with implications for climate change and California's energy supply

    NASA Astrophysics Data System (ADS)

    Croft, Gregory Donald

    There are two commonly-used approaches to modeling the future supply of mineral resources. One is to estimate reserves and compare the result to extraction rates, and the other is to project from historical time series of extraction rates. Perceptions of abundant oil supplies in the Middle East and abundant coal supplies in the United States are based on the former approach. In both of these cases, an approach based on historical production series results in a much smaller resource estimate than aggregate reserve numbers. This difference is not systematic; natural gas production in the United States shows a strong increasing trend even though modest reserve estimates have resulted in three decades of worry about the gas supply. The implication of a future decline in Middle East oil production is that the market for transportation fuels is facing major changes, and that alternative fuels should be analyzed in this light. Because the U.S. holds very large coal reserves, synthesizing liquid hydrocarbons from coal has been suggested as an alternative fuel supply. To assess the potential of this process, one has to look at both the resource base and the net efficiency. The three states with the largest coal production declines in the 1996 to 2006 period are among the top 5 coal reserve holders, suggesting that gross coal reserves are a poor indicator of future production. Of the three categories of coal reserves reported by the U.S. Energy Information Administration, reserves at existing mines is the narrowest category and is approximately the equivalent of proved developed oil reserves. By this measure, Wyoming has the largest coal reserves in the U.S., and it accounted for all of U.S. coal production growth over the 1996 to 2006 time period. In Chapter 2, multi-cycle Hubbert curve analysis of historical data of coal production from 1850 to 2007 demonstrates that U.S. anthracite and bituminous coal are past their production peak. This result contradicts estimates based

  14. Enhanced Power Conversion Efficiency of Graphene/Silicon Heterojunction Solar Cells Through NiO Induced Doping.

    PubMed

    Kuru, Cihan; Yavuz, Serdar; Kargar, Alireza; Choi, Duyoung; Choi, Chulmin; Rustomji, Cyrus; Jin, Sungho; Bandaru, Prabhakar R

    2016-01-01

    We report a doping strategy, where nickel oxide (NiO) nanoparticle film coating is employed for graphene/Si heterojunction solar cells to improve the power conversion efficiency (PCE). NiO doping has been shown to improve the short circuit current (J(SC)) by 12%, open circuit voltage (V(OC)) by 25% and fill factor (FF) by 145% of the cells, in turn increasing the PCE from 1.37% to 4.91%. Furthermore, NiO doped graphene/Si solar cells don't show any significant performance degradation over 10 days revealing that NiO doping can be a promising approach for practical applications of graphene in solar cells. PMID:27398585

  15. Broadband plasmon-enhanced polymer solar cells with power conversion efficiency of 9.26% using mixed Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Hao, Jingyu; Xu, Ying; Chen, Shufen; Zhang, Yupei; Mai, Jiangquan; Lau, Tsz-Ki; Zhang, Ran; Mei, Yang; Wang, Lianhui; Lu, Xinhui; Huang, Wei

    2016-03-01

    As-synthesized Au nanoparticles (NPs) composed of bone-like and rod shapes and a minority of cube and irregular spheres, generating three localized surface plasmon resonance (LSPR) peaks of 525, 575, and 775 nm, were doped into poly(3, 4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) layer and realized a power conversion efficiency of as high as 9.26% in our polymer solar cells. Optical, electrical, and morphology changes induced by Au NPs were analyzed and results demonstrate that the outstanding device performance is mainly attributed to the LSPR- and scattering-induced absorption enhancement in the active layer. Besides, mixed Au NPs also decreased the bulk resistance of PEDOT:PSS, which is found to facilitate hole transport and collection.

  16. Impact of sub-cell internal luminescence yields on energy conversion efficiencies of tandem solar cells: A design principle

    SciTech Connect

    Zhu, Lin Kim, Changsu; Yoshita, Masahiro; Chen, Shaoqiang; Sato, Shintaroh; Mochizuki, Toshimitsu; Akiyama, Hidefumi; Kanemitsu, Yoshihiko

    2014-01-20

    To develop a realistic design principle, we calculated the maximum conversion efficiency η{sub sc} and optimized sub-cell band-gap energies E{sub g} in double-junction tandem solar cells via a detailed-balance theory, paying particular attention to their dependence on internal luminescence quantum yields y{sub int} of the top and bottom sub-cell materials. A strong drop in the maximum η{sub sc} occurs when y{sub int} slightly drops from 1 to 0.9, where the drop in y{sub int} of the bottom cell causes a stronger effect than that of the top cell. For low values of y{sub int}, the maximum η{sub sc} has a simple logarithmic dependence on the geometric mean of the two sub-cells'y{sub int}.

  17. On Optimizing K-Shell X-ray Conversion Efficiencies with New Nano-structured Laser Targets

    NASA Astrophysics Data System (ADS)

    Colvin, Jeffrey; Charnvanichborikarn, Supakit; Felter, Tom; Flores, Chad; Fournier, Kevin; Gilbert, Dustin; Kucheyev, Sergei; Liu, Kai

    2011-10-01

    We have begun developing new nano-fabrication techniques to make suitable laser targets that can form highly uniform high-Z non-LTE plasmas when illuminated by high-intensity laser light. In this presentation we first discuss progress in developing very low-density pure Cu foams via a four-step ion-lithography process and progress in mechanically trapping Cu nanowires in a silica aerogel foam. We then discuss the radiation-hydrodynamics and non-LTE atomic physics modeling of various targets we could assemble from these foams, and what the modeling reveals about how best to optimize Cu K-shell x-ray conversion efficiencies via target design. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract No. DE-AC52-07NA27344, with funding from a Basic Research grant from the U.S. Defense Threat Reduction Agency.

  18. Efficient Method of Achieving Agreements between Individuals and Organizations about RFID Privacy

    NASA Astrophysics Data System (ADS)

    Cha, Shi-Cho

    This work presents novel technical and legal approaches that address privacy concerns for personal data in RFID systems. In recent years, to minimize the conflict between convenience and the privacy risk of RFID systems, organizations have been requested to disclose their policies regarding RFID activities, obtain customer consent, and adopt appropriate mechanisms to enforce these policies. However, current research on RFID typically focuses on enforcement mechanisms to protect personal data stored in RFID tags and prevent organizations from tracking user activity through information emitted by specific RFID tags. A missing piece is how organizations can obtain customers' consent efficiently and flexibly. This study recommends that organizations obtain licenses automatically or semi-automatically before collecting personal data via RFID technologies rather than deal with written consents. Such digitalized and standard licenses can be checked automatically to ensure that collection and use of personal data is based on user consent. While individuals can easily control who has licenses and license content, the proposed framework provides an efficient and flexible way to overcome the deficiencies in current privacy protection technologies for RFID systems.

  19. Giant Up-Conversion Efficiency of InGaAs Quantum Dots in a Planar Microcavity

    PubMed Central

    Xu, Qinfeng; Piermarocchi, Carlo; Pershin, Yuriy V.; Salamo, G. J.; Xiao, Min; Wang, Xiaoyong; Shih, Chih-Kang

    2014-01-01

    Self-assembled InGaAs quantum dots (QDs) were fabricated inside a planar microcavity with two vertical cavity modes. This allowed us to excite the QDs coupled to one of the vertical cavity modes through two propagating cavity modes to study their down- and up-converted photoluminescence (PL). The up-converted PL increased continuously with the increasing temperature, reaching an intensity level comparable to that of the down-converted PL at ~120 K. This giant efficiency in the up-converted PL of InGaAs QDs was enhanced by about 2 orders of magnitude with respect to a similar structure without cavity. We tentatively explain the enhanced up-converted signal as a direct consequence of the modified spontaneous emission properties of the QDs in the microcavity, combined with the phonon absorption and emission effects. PMID:24492329

  20. Efficient conversion of surface-plasmon-like modes to spatial radiated modes

    SciTech Connect

    Xu, Jun Jun; Zhang, Hao Chi; Zhang, Qian; Cui, Tie Jun

    2015-01-12

    We propose a spoof surface plasmon polariton (SPP) emitter which is composed of ultrathin corrugated metallic strips, exhibiting the directional radiation property. The spoof SPP emitter provides a way to quickly convert the SPP mode to a radiated mode. By controlling phase modulations produced by the phase-gradient metasurface on the ultrathin metallic strips, we demonstrate theoretically and experimentally that spoof SPP waves are converted into spatial propagating waves with high efficiency, which are further radiated with flexible beam steering. The proposed method sets up a link between SPP waves and radiation waves in a highly controllable way, which would possibly open an avenue in designing new kinds of microwave and optical elements in engineering.

  1. Unassisted photoelectrochemical water splitting exceeding 7% solar-to-hydrogen conversion efficiency using photon recycling

    NASA Astrophysics Data System (ADS)

    Shi, Xinjian; Jeong, Hokyeong; Oh, Seung Jae; Ma, Ming; Zhang, Kan; Kwon, Jeong; Choi, In Taek; Choi, Il Yong; Kim, Hwan Kyu; Kim, Jong Kyu; Park, Jong Hyeok

    2016-06-01

    Various tandem cell configurations have been reported for highly efficient and spontaneous hydrogen production from photoelectrochemical solar water splitting. However, there is a contradiction between two main requirements of a front photoelectrode in a tandem cell configuration, namely, high transparency and high photocurrent density. Here we demonstrate a simple yet highly effective method to overcome this contradiction by incorporating a hybrid conductive distributed Bragg reflector on the back side of the transparent conducting substrate for the front photoelectrochemical electrode, which functions as both an optical filter and a conductive counter-electrode of the rear dye-sensitized solar cell. The hybrid conductive distributed Bragg reflectors were designed to be transparent to the long-wavelength part of the incident solar spectrum (λ>500 nm) for the rear solar cell, while reflecting the short-wavelength photons (λ<500 nm) which can then be absorbed by the front photoelectrochemical electrode for enhanced photocurrent generation.

  2. Unassisted photoelectrochemical water splitting exceeding 7% solar-to-hydrogen conversion efficiency using photon recycling.

    PubMed

    Shi, Xinjian; Jeong, Hokyeong; Oh, Seung Jae; Ma, Ming; Zhang, Kan; Kwon, Jeong; Choi, In Taek; Choi, Il Yong; Kim, Hwan Kyu; Kim, Jong Kyu; Park, Jong Hyeok

    2016-01-01

    Various tandem cell configurations have been reported for highly efficient and spontaneous hydrogen production from photoelectrochemical solar water splitting. However, there is a contradiction between two main requirements of a front photoelectrode in a tandem cell configuration, namely, high transparency and high photocurrent density. Here we demonstrate a simple yet highly effective method to overcome this contradiction by incorporating a hybrid conductive distributed Bragg reflector on the back side of the transparent conducting substrate for the front photoelectrochemical electrode, which functions as both an optical filter and a conductive counter-electrode of the rear dye-sensitized solar cell. The hybrid conductive distributed Bragg reflectors were designed to be transparent to the long-wavelength part of the incident solar spectrum (λ>500 nm) for the rear solar cell, while reflecting the short-wavelength photons (λ<500 nm) which can then be absorbed by the front photoelectrochemical electrode for enhanced photocurrent generation. PMID:27324578

  3. Achieving Internet-based efficiencies in a rural IDS: a case study.

    PubMed

    Bacus, R; Zunke, R

    2001-09-01

    After suffering payment cuts resulting from the Balanced Budget Act of 1997, Colorado-Fayette Medical Center (CFMC), a not-for-profit, rural integrated delivery system in Texas, wanted to reduce costs by gaining systemwide Internet access for its internal information system at a reasonable price. An application service provider affiliated with the Texas Hospital Association, helped CFMC achieve its goals for the project by performing a needs assessment, installing a wide-area network (WAN) with Internet access, and training staff. The new WAN enabled CFMC to improve its Web presence, allow radiologic image viewing at all sites, negotiate more favorable prices from vendors, implement electronic communication for staff members, and take advantage of on-line education opportunities. CFMC has found that the monthly fee paid to THN is offset by savings on long-distance calls, Internet service provider fees, and marketing and advertising costs. PMID:11552587

  4. Metering Best Practices, A Guide to Achieving Utility Resource Efficiency, Release 2.0

    SciTech Connect

    Sullivan, Greg; Hunt, W. D.; Pugh, Ray; Sandusky, William F.; Koehler, Theresa M.; Boyd, Brian K.

    2011-08-31

    This release is an update and expansion of the information provided in Release 1.0 of the Metering Best Practice Guide that was issued in October 2007. This release, as was the previous release, was developed under the direction of the U.S. Department of Energy's Federal Energy Management Program (FEMP). The mission of FEMP is to facilitate the Federal Government's implementation of sound cost-effective energy management and investment practices to enhance the nation's energy security and environmental stewardship. Each of these activities is directly related to achieving requirements set forth in the Energy Policy Acts of 1992 and 2005, the Energy Independence and Security Act (EISA) of 2007, and the goals that have been established in Executive Orders 13423 and 13514 - and also those practices that are inherent in sound management of Federal financial and personnel resources.

  5. On Field-Effect Photovoltaics: Gate Enhancement of the Power Conversion Efficiency in a Nanotube/Silicon-Nanowire Solar Cell.

    PubMed

    Petterson, Maureen K; Lemaitre, Maxime G; Shen, Yu; Wadhwa, Pooja; Hou, Jie; Vasilyeva, Svetlana V; Kravchenko, Ivan I; Rinzler, Andrew G

    2015-09-30

    Recent years have seen a resurgence of interest in crystalline silicon Schottky junction solar cells distinguished by the use of low density of electronic states (DOS) nanocarbons (nanotubes, graphene) as the metal contacting the Si. Recently, unprecedented modulation of the power conversion efficiency in a single material system has been demonstrated in such cells by the use of electronic gating. The gate field induced Fermi level shift in the low-DOS carbon serves to enhance the junction built-in potential, while a gate field induced inversion layer at the Si surface, in regions remote from the junction, keeps the photocarriers well separated there, avoiding recombination at surface traps and defects (a key loss mechanism). Here, we extend these results into the third dimension of a vertical Si nanowire array solar cell. A single wall carbon nanotube layer engineered to contact virtually each n-Si nanowire tip extracts the minority carriers, while an ionic liquid electrolytic gate drives the nanowire body into inversion. The enhanced light absorption of the vertical forest cell, at 100 mW/cm(2) AM1.5G illumination, results in a short-circuit current density of 35 mA/cm(2) and associated power conversion efficiency of 15%. These results highlight the use of local fields as opposed to surface passivation as a means of avoiding front surface recombination. A deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue, a nonencapsulation-based approach is also implemented. PMID:26352052

  6. On Field-Effect Photovoltaics: Gate Enhancement of the Power Conversion Efficiency in a Nanotube/Silicon-Nanowire Solar Cell

    DOE PAGESBeta

    Petterson, Maureen K.; Lemaitre, Maxime G.; Shen, Yu; Wadhwa, Pooja; Hou, Jie; Vasilyeva, Svetlana V.; Kravchenko, Ivan I.; Rinzler, Andrew G.

    2015-09-09

    Recent years have seen a resurgence of interest in crystalline silicon Schottky junction solar cells distinguished by the use of low density of electronic states (DOS) nanocarbons (nanotubes, graphene) as the metal contacting the Si. Recently, unprecedented modulation of the power conversion efficiency in a single material system has been demonstrated in such cells by the use of electronic gating. The gate field induced Fermi level shift in the low-DOS carbon serves to enhance the junction built-in potential, while a gate field induced inversion layer at the Si surface, in regions remote from the junction, keeps the photocarriers well separatedmore » there, avoiding recombination at surface traps and defects (a key loss mechanism). Here, we extend these results into the third dimension of a vertical Si nanowire array solar cell. A single wall carbon nanotube layer engineered to contact virtually each n-Si nanowire tip extracts the minority carriers, while an ionic liquid electrolytic gate drives the nanowire body into inversion. The enhanced light absorption of the vertical forest cell, at 100 mW/cm2 AM1.5G illumination, results in a short-circuit current density of 35 mA/cm2 and associated power conversion efficiency of 15%. These results highlight the use of local fields as opposed to surface passivation as a means of avoiding front surface recombination. Finally, a deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue, a nonencapsulation-based approach is also implemented.« less

  7. On Field-Effect Photovoltaics: Gate Enhancement of the Power Conversion Efficiency in a Nanotube/Silicon-Nanowire Solar Cell

    SciTech Connect

    Petterson, Maureen K.; Lemaitre, Maxime G.; Shen, Yu; Wadhwa, Pooja; Hou, Jie; Vasilyeva, Svetlana V.; Kravchenko, Ivan I.; Rinzler, Andrew G.

    2015-09-09

    Recent years have seen a resurgence of interest in crystalline silicon Schottky junction solar cells distinguished by the use of low density of electronic states (DOS) nanocarbons (nanotubes, graphene) as the metal contacting the Si. Recently, unprecedented modulation of the power conversion efficiency in a single material system has been demonstrated in such cells by the use of electronic gating. The gate field induced Fermi level shift in the low-DOS carbon serves to enhance the junction built-in potential, while a gate field induced inversion layer at the Si surface, in regions remote from the junction, keeps the photocarriers well separated there, avoiding recombination at surface traps and defects (a key loss mechanism). Here, we extend these results into the third dimension of a vertical Si nanowire array solar cell. A single wall carbon nanotube layer engineered to contact virtually each n-Si nanowire tip extracts the minority carriers, while an ionic liquid electrolytic gate drives the nanowire body into inversion. The enhanced light absorption of the vertical forest cell, at 100 mW/cm2 AM1.5G illumination, results in a short-circuit current density of 35 mA/cm2 and associated power conversion efficiency of 15%. These results highlight the use of local fields as opposed to surface passivation as a means of avoiding front surface recombination. Finally, a deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue, a nonencapsulation-based approach is also implemented.

  8. Progress toward achieving high power and high efficiency semipolar LEDs and their characterization

    NASA Astrophysics Data System (ADS)

    Zhong, Hong

    Performance of current commercially available wurtzite nitride based light-emitting diodes (LEDs), grown along the polar (0001) c-plane orientation, is limited by the presence of polarization-related electric fields inside multi-quantum wells (MQWs). The discontinuities in both spontaneous and piezoelectric polarization at the heterointerfaces result in internal electric fields in the quantum wells. These electric fields cause carrier separation [quantum confined Stark effect (QCSE)] and reduce the radiative recombination rate within the quantum wells. One approach to reduce and possibly eliminate the polarization-related effects is to grow III-nitride devices on crystal planes that are inclined with respect to the c-axis, i.e., on semipolar planes. In this dissertation, metalorganic chemical vapor deposition (MOCVD) has been employed for the homoepitaxial growth of GaN based LEDs on semipolar orientations. As a consequence of growing on high-quality bulk GaN substrates, the LEDs have significantly reduced threading dislocation and stacking fault densities, resulting in remarkable improvements in EQE and output power. High efficiency semipolar (1011) violet-blue and blue LEDs have been demonstrated without any intentional effort to enhance the light extraction from those devices. Optimizations of epitaxial structures have led to increased output power and external quantum efficiency. A silicone encapsulated single quantum well blue LED with peak wavelength of 444 nm with output power of 24.3 mW, external quantum efficiency of 43% and luminous efficacy of 75 lm/W (with phosphorescent coating) at 20 mA has been demonstrated. Polarization fields in strained (1011) and (112¯2) InGaN quantum wells have been experimentally determined through bias-dependent optical studies. Our results show that the polarization field flips its direction in semipolar InGaN quantum wells with large inclination angles (i.e. around 60°). This suggests that there exists a polarization

  9. Achieving 100% Efficient Postcolumn Hydride Generation for As Speciation Analysis by Atomic Fluorescence Spectrometry.

    PubMed

    Marschner, Karel; Musil, Stanislav; Dědina, Jiří

    2016-04-01

    An experimental setup consisting of a flow injection hydride generator coupled to an atomic fluorescence spectrometer was optimized in order to generate arsanes from tri- and pentavalent inorganic arsenic species (iAs(III), iAs(V)), monomethylarsonic acid (MAs(V)), and dimethylarsinic acid (DMAs(V)) with 100% efficiency with the use of only HCl and NaBH4 as the reagents. The optimal concentration of HCl was 2 mol L(-1); the optimal concentration of NaBH4 was 2.5% (m/v), and the volume of the reaction coil was 8.9 mL. To prevent excessive signal noise due to fluctuations of hydride supply to an atomizer, a new design of a gas-liquid separator was implemented. The optimized experimental setup was subsequently interfaced to HPLC and employed for speciation analysis of arsenic. Two chromatography columns were tested: (i) ion-pair chromatography and (ii) ion exchange chromatography. The latter offered much better results for human urine samples without a need for sample dilution. Due to the equal hydride generation efficiency (and thus the sensitivities) of all As species, a single species standardization by DMAs(V) standard was feasible. The limits of detection for iAs(III), iAs(V), MAs(V), and DMAs(V) were 40, 97, 57, and 55 pg mL(-1), respectively. Accuracy of the method was tested by the analysis of the standard reference material (human urine NIST 2669), and the method was also verified by the comparative analyses of human urine samples collected from five individuals with an independent reference method. PMID:26938848

  10. Operations & Maintenance Best Practices - A Guide to Achieving Operational Efficiency (Release 3)

    SciTech Connect

    Sullivan, Greg; Pugh, Ray; Melendez, Aldo P.; Hunt, W. D.

    2010-08-04

    This guide highlights operations and maintenance programs targeting energy and water efficiency that are estimated to save 5% to 20% on energy bills without a significant capital investment. The purpose of this guide is to provide you, the Operations and Maintenance (O&M)/Energy manager and practitioner, with useful information about O&M management, technologies, energy and water efficiency, and cost-reduction approaches. To make this guide useful and to reflect your needs and concerns, the authors met with O&M and Energy managers via Federal Energy Management Program (FEMP) workshops. In addition, the authors conducted extensive literature searches and contacted numerous vendors and industry experts. The information and case studies that appear in this guide resulted from these activities. It needs to be stated at the outset that this guide is designed to provide information on effective O&M as it applies to systems and equipment typically found at Federal facilities. This guide is not designed to provide the reader with step-by-step procedures for performing O&M on any specific piece of equipment. Rather, this guide first directs the user to the manufacturer's specifications and recommendations. In no way should the recommendations in this guide be used in place of manufacturer's recommendations. The recommendations in this guide are designed to supplement those of the manufacturer, or, as is all too often the case, provide guidance for systems and equipment for which all technical documentation has been lost. As a rule, this guide will first defer to the manufacturer's recommendations on equipment operation and maintenance.

  11. Improving energy conversion efficiency for triboelectric nanogenerator with capacitor structure by maximizing surface charge density.

    PubMed

    He, Xianming; Guo, Hengyu; Yue, Xule; Gao, Jun; Xi, Yi; Hu, Chenguo

    2015-02-01

    Nanogenerators with capacitor structures based on piezoelectricity, pyroelectricity, triboelectricity and electrostatic induction have been extensively investigated. Although the electron flow on electrodes is well understood, the maximum efficiency-dependent structure design is not clearly known. In this paper, a clear understanding of triboelectric generators with capacitor structures is presented by the investigation of polydimethylsiloxane-based composite film nanogenerators, indicating that the generator, in fact, acts as both an energy storage and output device. Maximum energy storage and output depend on the maximum charge density on the dielectric polymer surface, which is determined by the capacitance of the device. The effective thickness of polydimethylsiloxane can be greatly reduced by mixing a suitable amount of conductive nanoparticles into the polymer, through which the charge density on the polymer surface can be greatly increased. This finding can be applied to all the triboelectric nanogenerators with capacitor structures, and it provides an important guide to the structural design for nanogenerators. It is demonstrated that graphite particles with sizes of 20-40 nm and 3.0% mass mixed into the polydimethylsiloxane can reduce 34.68% of the effective thickness of the dielectric film and increase the surface charges by 111.27% on the dielectric film. The output power density of the triboelectric nanogenerator with the composite polydimethylsiloxane film is 3.7 W m(-2), which is 2.6 times as much as that of the pure polydimethylsiloxane film. PMID:25526319

  12. Outstanding efficiency in energy conversion for electric motors constructed by nanocrystalline soft magnetic alloy "NANOMET®" cores

    NASA Astrophysics Data System (ADS)

    Nishiyama, N.; Tanimoto, K.; Makino, A.

    2016-05-01

    Recently updated nanocrystalline soft magnetic Fe-Co-Si-B-P-Cu alloys "NANOMET®" exhibit high saturation magnetic flux density (Bs > 1.8 T), low coercivity (Hc < 10 A/m) and low core loss (W1.7/50 ˜ 0.4 W/kg) even in a ribbon form with a thickness of up to 40 μm. By utilize excellent magnetic softness, several products such as motors or transformers for electrical appliances are now under developing by industry-academia collaboration. In particular, it is found that a brushless DC motor using NANOMET® core exhibited remarkable improvement in energy consumption. The prototype motor with an outer core diameter of 70 mm and a core thickness of 50 mm was constructed using laminated nano-crystallized NANOMET® ribbons. Core-loss for the constructed motor was improved from 1.4 W to 0.4 W only by replacing the non-oriented Si-steel core with NANOMET® one. The overall motor efficiency is evaluated to be 3% improvement. In this work, the relation between processing and resulting magnetic properties will be presented. In addition, feasibility for commercialization will also be discussed.

  13. Enhanced Detection Efficiency of Direct Conversion X-ray Detector Using Polyimide as Hole-Blocking Layer

    PubMed Central

    Abbaszadeh, Shiva; Scott, Christopher C.; Bubon, Oleksandr; Reznik, Alla; Karim, Karim S.

    2013-01-01

    In this article we demonstrate the performance of a direct conversion amorphous selenium (a-Se) X-ray detector using biphenyldisnhydride/1,4 phenylenediamine (BPDA/PPD) polyimide (PI) as a hole-blocking layer. The use of a PI layer with a-Se allows detector operation at high electric fields (≥10 V/μm) while maintaining low dark current, without deterioration of transient performance. The hole mobility of the PI/a-Se device is measured by the time-of-flight method at different electric fields to investigate the effect of the PI layer on detector performance. It was found that hole mobility as high as 0.75 cm2/Vs is achievable by increasing the electric field in the PI/a-Se device structure. Avalanche multiplication is also shown to be achievable when using PI as a blocking layer. Increasing the electric field within a-Se reduces the X-ray ionization energy, increases hole mobility, and improves the dynamic range and sensitivity of the detector. PMID:24285255

  14. Enhanced Detection Efficiency of Direct Conversion X-ray Detector Using Polyimide as Hole-Blocking Layer

    NASA Astrophysics Data System (ADS)

    Abbaszadeh, Shiva; Scott, Christopher C.; Bubon, Oleksandr; Reznik, Alla; Karim, Karim S.

    2013-11-01

    In this article we demonstrate the performance of a direct conversion amorphous selenium (a-Se) X-ray detector using biphenyldisnhydride/1,4 phenylenediamine (BPDA/PPD) polyimide (PI) as a hole-blocking layer. The use of a PI layer with a-Se allows detector operation at high electric fields (>=10 V/μm) while maintaining low dark current, without deterioration of transient performance. The hole mobility of the PI/a-Se device is measured by the time-of-flight method at different electric fields to investigate the effect of the PI layer on detector performance. It was found that hole mobility as high as 0.75 cm2/Vs is achievable by increasing the electric field in the PI/a-Se device structure. Avalanche multiplication is also shown to be achievable when using PI as a blocking layer. Increasing the electric field within a-Se reduces the X-ray ionization energy, increases hole mobility, and improves the dynamic range and sensitivity of the detector.

  15. Enhanced detection efficiency of direct conversion X-ray detector using polyimide as hole-blocking layer.

    PubMed

    Abbaszadeh, Shiva; Scott, Christopher C; Bubon, Oleksandr; Reznik, Alla; Karim, Karim S

    2013-01-01

    In this article we demonstrate the performance of a direct conversion amorphous selenium (a-Se) X-ray detector using biphenyldisnhydride/1,4 phenylenediamine (BPDA/PPD) polyimide (PI) as a hole-blocking layer. The use of a PI layer with a-Se allows detector operation at high electric fields (≥10 V/μm) while maintaining low dark current, without deterioration of transient performance. The hole mobility of the PI/a-Se device is measured by the time-of-flight method at different electric fields to investigate the effect of the PI layer on detector performance. It was found that hole mobility as high as 0.75 cm(2)/Vs is achievable by increasing the electric field in the PI/a-Se device structure. Avalanche multiplication is also shown to be achievable when using PI as a blocking layer. Increasing the electric field within a-Se reduces the X-ray ionization energy, increases hole mobility, and improves the dynamic range and sensitivity of the detector. PMID:24285255

  16. Improving energy conversion efficiency for triboelectric nanogenerator with capacitor structure by maximizing surface charge density

    NASA Astrophysics Data System (ADS)

    He, Xianming; Guo, Hengyu; Yue, Xule; Gao, Jun; Xi, Yi; Hu, Chenguo

    2015-01-01

    Nanogenerators with capacitor structures based on piezoelectricity, pyroelectricity, triboelectricity and electrostatic induction have been extensively investigated. Although the electron flow on electrodes is well understood, the maximum efficiency-dependent structure design is not clearly known. In this paper, a clear understanding of triboelectric generators with capacitor structures is presented by the investigation of polydimethylsiloxane-based composite film nanogenerators, indicating that the generator, in fact, acts as both an energy storage and output device. Maximum energy storage and output depend on the maximum charge density on the dielectric polymer surface, which is determined by the capacitance of the device. The effective thickness of polydimethylsiloxane can be greatly reduced by mixing a suitable amount of conductive nanoparticles into the polymer, through which the charge density on the polymer surface can be greatly increased. This finding can be applied to all the triboelectric nanogenerators with capacitor structures, and it provides an important guide to the structural design for nanogenerators. It is demonstrated that graphite particles with sizes of 20-40 nm and 3.0% mass mixed into the polydimethylsiloxane can reduce 34.68% of the effective thickness of the dielectric film and increase the surface charges by 111.27% on the dielectric film. The output power density of the triboelectric nanogenerator with the composite polydimethylsiloxane film is 3.7 W m-2, which is 2.6 times as much as that of the pure polydimethylsiloxane film.Nanogenerators with capacitor structures based on piezoelectricity, pyroelectricity, triboelectricity and electrostatic induction have been extensively investigated. Although the electron flow on electrodes is well understood, the maximum efficiency-dependent structure design is not clearly known. In this paper, a clear understanding of triboelectric generators with capacitor structures is presented by the

  17. The use of ECDIS equipment to achieve an optimum value for energy efficiency operation index

    NASA Astrophysics Data System (ADS)

    Acomi, N.; Acomi, O. C.; Stanca, C.

    2015-11-01

    To reduce air pollution produced by ships, the International Maritime Organization has developed a set of technical, operational and management measures. The subject of our research addresses the operational measures for minimizing CO2 air emissions and the way how the emission value could be influenced by external factors regardless of ship-owners’ will. This study aims to analyse the air emissions for a loaded voyage leg performed by an oil tanker. The formula that allows us to calculate the predicted Energy Efficiency Operational Index involves the estimation of distance and fuel consumption, while the quantity of cargo is known. The electronic chart display and information system, ECDIS Simulation Software, will be used for adjusting the passage plan in real time, given the predicted severe environmental conditions. The distance will be determined using ECDIS, while the prediction of the fuel consumption will consider the sea trial and the vessel experience records. That way it will be possible to compare the estimated EEOI value in the case of great circle navigation in adverse weather condition with the estimated EEOI value for weather navigation.

  18. Depth Filters Containing Diatomite Achieve More Efficient Particle Retention than Filters Solely Containing Cellulose Fibers

    PubMed Central

    Buyel, Johannes F.; Gruchow, Hannah M.; Fischer, Rainer

    2015-01-01

    The clarification of biological feed stocks during the production of biopharmaceutical proteins is challenging when large quantities of particles must be removed, e.g., when processing crude plant extracts. Single-use depth filters are often preferred for clarification because they are simple to integrate and have a good safety profile. However, the combination of filter layers must be optimized in terms of nominal retention ratings to account for the unique particle size distribution in each feed stock. We have recently shown that predictive models can facilitate filter screening and the selection of appropriate filter layers. Here we expand our previous study by testing several filters with different retention ratings. The filters typically contain diatomite to facilitate the removal of fine particles. However, diatomite can interfere with the recovery of large biopharmaceutical molecules such as virus-like particles and aggregated proteins. Therefore, we also tested filtration devices composed solely of cellulose fibers and cohesive resin. The capacities of both filter types varied from 10 to 50 L m−2 when challenged with tobacco leaf extracts, but the filtrate turbidity was ~500-fold lower (~3.5 NTU) when diatomite filters were used. We also tested pre–coat filtration with dispersed diatomite, which achieved capacities of up to 120 L m−2 with turbidities of ~100 NTU using bulk plant extracts, and in contrast to the other depth filters did not require an upstream bag filter. Single pre-coat filtration devices can thus replace combinations of bag and depth filters to simplify the processing of plant extracts, potentially saving on time, labor and consumables. The protein concentrations of TSP, DsRed and antibody 2G12 were not affected by pre-coat filtration, indicating its general applicability during the manufacture of plant-derived biopharmaceutical proteins. PMID:26734037

  19. Efficient Solar Energy Conversion Using CaCu3Ti4O12 Photoanode for Photocatalysis and Photoelectrocatalysis

    NASA Astrophysics Data System (ADS)

    Kushwaha, H. S.; Madhar, Niyaz A.; Ilahi, B.; Thomas, P.; Halder, Aditi; Vaish, Rahul

    2016-01-01

    A highly efficient third generation catalyst, CaCu3Ti4O12 (CCTO) shows excellent photoelectrochemical (PEC) and photocatalytic ability. As only 4% part of the solar spectrum covers UV light, thus it is highly desirable to develop visible light active photocatalyst materials like CCTO for effective solar energy conversion. A direct band transition with a narrow band gap (1.5 eV) was observed. Under light irradiation, high photocurrent density was found to be 0.96 mA/cm2, indicating the visible light induced photocatalytic ability of CCTO. Visible light mediated photocatalytic and photoelectrocatalytic degradation efficiency of CaCu3Ti4O12 pellets (CCTO) was investigated for three classes of pharmaceutical waste: erythrosin (dye), ciprofloxacin (antibiotic) and estriol (steroid). It is found that the degradation process follows first order kinetic reaction in electrocatalysis, photocatalysis and photoelectrocatalysis and high kinetic rate constant was observed in photoelectrocatalysis. This was quite high in comparison to previously reported methods.

  20. Fabrication of Cu2SnS3 thin-film solar cells with power conversion efficiency of over 4%

    NASA Astrophysics Data System (ADS)

    Kanai, Ayaka; Toyonaga, Kotoba; Chino, Kotaro; Katagiri, Hironori; Araki, Hideaki

    2015-08-01

    Cu2SnS3 (CTS) thin films were produced by the co-evaporation of Cu, Sn, and cracked sulfur, followed by annealing. The as-deposited films were then annealed at 570 °C for 5 min in the presence of 100 mg of sulfur lumps in a rapid thermal processing furnace filled with N2 gas at atmospheric pressure. Solar cells were then fabricated using the CTS films as absorber layers, and their efficiency was evaluated for different Cu/Sn compositional ratios. The largest grain size was found for films with a slightly Sn-rich composition. The highest performance was obtained for solar cells containing a CTS thin film with a Cu/Sn ratio of about 1.9. A cell with a Cu/Sn ratio of 1.87 exhibited an open-circuit voltage of 258 mV, a short-circuit current density of 35.6 mA/cm2, a fill factor of 0.467, and a power conversion efficiency of 4.29%.

  1. Efficient Solar Energy Conversion Using CaCu3Ti4O12 Photoanode for Photocatalysis and Photoelectrocatalysis

    PubMed Central

    Kushwaha, H. S.; Madhar, Niyaz A; Ilahi, B.; Thomas, P.; Halder, Aditi; Vaish, Rahul

    2016-01-01

    A highly efficient third generation catalyst, CaCu3Ti4O12 (CCTO) shows excellent photoelectrochemical (PEC) and photocatalytic ability. As only 4% part of the solar spectrum covers UV light, thus it is highly desirable to develop visible light active photocatalyst materials like CCTO for effective solar energy conversion. A direct band transition with a narrow band gap (1.5 eV) was observed. Under light irradiation, high photocurrent density was found to be 0.96 mA/cm2, indicating the visible light induced photocatalytic ability of CCTO. Visible light mediated photocatalytic and photoelectrocatalytic degradation efficiency of CaCu3Ti4O12 pellets (CCTO) was investigated for three classes of pharmaceutical waste: erythrosin (dye), ciprofloxacin (antibiotic) and estriol (steroid). It is found that the degradation process follows first order kinetic reaction in electrocatalysis, photocatalysis and photoelectrocatalysis and high kinetic rate constant was observed in photoelectrocatalysis. This was quite high in comparison to previously reported methods. PMID:26725655

  2. Efficient Solar Energy Conversion Using CaCu3Ti4O12 Photoanode for Photocatalysis and Photoelectrocatalysis.

    PubMed

    Kushwaha, H S; Madhar, Niyaz A; Ilahi, B; Thomas, P; Halder, Aditi; Vaish, Rahul

    2016-01-01

    A highly efficient third generation catalyst, CaCu3Ti4O12 (CCTO) shows excellent photoelectrochemical (PEC) and photocatalytic ability. As only 4% part of the solar spectrum covers UV light, thus it is highly desirable to develop visible light active photocatalyst materials like CCTO for effective solar energy conversion. A direct band transition with a narrow band gap (1.5 eV) was observed. Under light irradiation, high photocurrent density was found to be 0.96 mA/cm(2), indicating the visible light induced photocatalytic ability of CCTO. Visible light mediated photocatalytic and photoelectrocatalytic degradation efficiency of CaCu3Ti4O12 pellets (CCTO) was investigated for three classes of pharmaceutical waste: erythrosin (dye), ciprofloxacin (antibiotic) and estriol (steroid). It is found that the degradation process follows first order kinetic reaction in electrocatalysis, photocatalysis and photoelectrocatalysis and high kinetic rate constant was observed in photoelectrocatalysis. This was quite high in comparison to previously reported methods. PMID:26725655

  3. Enhanced power conversion efficiency in InGaN-based solar cells via graded composition multiple quantum wells.

    PubMed

    Tsai, Yu-Lin; Wang, Sheng-Wen; Huang, Jhih-Kai; Hsu, Lung-Hsing; Chiu, Ching-Hsueh; Lee, Po-Tsung; Yu, Peichen; Lin, Chien-Chung; Kuo, Hao-Chung

    2015-11-30

    This work demonstrates the enhanced power conversion efficiency (PCE) in InGaN/GaN multiple quantum well (MQWs) solar cells with gradually decreasing indium composition in quantum wells (GQWs) toward p-GaN as absorber. The GQW can improve the fill factor from 42% to 62% and enhance the short current density from 0.8 mA/cm2 to 0.92 mA/cm2, as compares to the typical MQW solar cells. As a result, the PCE is boosted from 0.63% to 1.11% under AM1.5G illumination. Based on simulation and experimental results, the enhanced PCE can be attributed to the improved carrier collection in GQW caused by the reduction of potential barriers and piezoelectric polarization induced fields near the p-GaN layer. The presented concept paves a way toward highly efficient InGaN-based solar cells and other GaN-related MQW devices. PMID:26698792

  4. Simulation and Experimental Study on the Efficiency of Traveling Wave Direct Energy Conversion for Application to Aneutronic Fusion Reactions

    NASA Astrophysics Data System (ADS)

    Tarditi, Alfonso; Chap, Andrew; Miley, George; Scott, John

    2013-10-01

    A study based on both Particle-in-cell (PIC) simulation and experiments is being developed to study the physics of the Traveling Wave Direct Energy Converter (TWDEC,) with the perspective of application to aneutronic fusion reaction products and space propulsion. The PIC model is investigating in detail the key TWDEC physics process by simulating the time-dependent transfer of energy from the ion beam to an electric load connected to ring-type electrodes in cylindrical symmetry. An experimental effort is in progress on a TWDEC test article at NASA, Johnson Space Center with the purpose of studying the conditions for improving the efficiency of the direct energy conversion process. Using a scaled-down ion energy source, the experiment is primarily focused on the effect of the (bunched) beam density on the efficiency and on the optimization of the electrode design. The simulation model is guiding the development of the experimental configuration and will provide details of the beam dynamics for direct comparison with experimental diagnostics. Work supported by NASA, Johnson Space Center.

  5. Correlating high power conversion efficiency of PTB7:PC71BM inverted organic solar cells with nanoscale structures.

    PubMed

    Das, Sanjib; Keum, Jong K; Browning, James F; Gu, Gong; Yang, Bin; Dyck, Ondrej; Do, Changwoo; Chen, Wei; Chen, Jihua; Ivanov, Ilia N; Hong, Kunlun; Rondinone, Adam J; Joshi, Pooran C; Geohegan, David B; Duscher, Gerd; Xiao, Kai

    2015-10-14

    Advances in material design and device engineering led to inverted organic solar cells (i-OSCs) with superior power conversion efficiencies (PCEs) compared to their "conventional" counterparts, in addition to the well-known better ambient stability. Here, we report an in-depth morphology study of the i-OSC active and cathode modifying layers, employing a model system with a well-established bulk-heterojunction, PTB7:PC71BM as the active layer and poly-[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as the cathode surface modifying layer. We have also identified the role of a processing additive, 1,8-diiodooctane (DIO), used in the spin-casting of the active layer to increase PCE. Using various characterization techniques, we demonstrate that the high PCEs of i-OSCs are due to the diffusion of electron-accepting PC71BM into the PFN layer, resulting in improved electron transport. The diffusion occurs when residual solvent molecules in the spun-cast film act as a plasticizer. Addition of DIO to the casting solution results in more PC71BM diffusion and therefore more efficient electron transport. This work provides important insight and guidance to further enhancement of i-OSC performance by materials and interface engineering. PMID:26220775

  6. Study of the potential energy conversion efficiency of organic solar cells based on donor/acceptor heterojunctions

    NASA Astrophysics Data System (ADS)

    Geens, Wim

    2002-01-01

    Organic solar cells can offer an appealing alternative for bulk silicon solar cells due to their attractive properties such as flexibility and possibility to apply low-cost manufacturing techniques. The different types of existing organic solar cells reported in the literature have been critically assessed in terms of performance and processability, based on which it was concluded that the concept of the donor/acceptor bulk heterojunction sandwiched between a transparent and a metal electrode has the most potential. In order to gain more insight into the charge transport properties of spin-cast photovoltaic conjugated polymer/fullerene blends, these films were incorporated into field-effect transistors to derive values for the electron and hole mobilities. Model calculations showed that increasing these mobility values in combination with the use of thicker active layers could significantly enhance the short-circuit current density of the bulk heterojunction solar cells. Optimisation of the charge transport is required and was realised in this study by choosing PPV-oligomers and C60 as well-defined building blocks to construct the donor/acceptor networks. First, these materials were spin-cast in single-layer diodes to allow full electrical characterisation, which was then compared with simulation of the devices in dark as well as under illumination. The photovoltaic performance of blended PPV-oligomer/C60 devices remained rather low due to C60-induced shunting paths and high molecular disorder. In a second part, more morphological order was obtained by using vacuum evaporation to deposit the organic materials. Besides structural characterisation of the evaporated films, the electrical behaviour of single-layer devices was investigated and the influence of interfacial layers was addressed. Photovoltaic devices based on evaporated planar heterojunctions reaching a conversion efficiency of 1.9% and exhibiting an open-circuit voltage of over 1 V were realised

  7. Efficient and Anonymous Two-Factor User Authentication in Wireless Sensor Networks: Achieving User Anonymity with Lightweight Sensor Computation

    PubMed Central

    Nam, Junghyun; Choo, Kim-Kwang Raymond; Han, Sangchul; Kim, Moonseong; Paik, Juryon; Won, Dongho

    2015-01-01

    A smart-card-based user authentication scheme for wireless sensor networks (hereafter referred to as a SCA-WSN scheme) is designed to ensure that only users who possess both a smart card and the corresponding password are allowed to gain access to sensor data and their transmissions. Despite many research efforts in recent years, it remains a challenging task to design an efficient SCA-WSN scheme that achieves user anonymity. The majority of published SCA-WSN schemes use only lightweight cryptographic techniques (rather than public-key cryptographic techniques) for the sake of efficiency, and have been demonstrated to suffer from the inability to provide user anonymity. Some schemes employ elliptic curve cryptography for better security but require sensors with strict resource constraints to perform computationally expensive scalar-point multiplications; despite the increased computational requirements, these schemes do not provide user anonymity. In this paper, we present a new SCA-WSN scheme that not only achieves user anonymity but also is efficient in terms of the computation loads for sensors. Our scheme employs elliptic curve cryptography but restricts its use only to anonymous user-to-gateway authentication, thereby allowing sensors to perform only lightweight cryptographic operations. Our scheme also enjoys provable security in a formal model extended from the widely accepted Bellare-Pointcheval-Rogaway (2000) model to capture the user anonymity property and various SCA-WSN specific attacks (e.g., stolen smart card attacks, node capture attacks, privileged insider attacks, and stolen verifier attacks). PMID:25849359

  8. Efficient and anonymous two-factor user authentication in wireless sensor networks: achieving user anonymity with lightweight sensor computation.

    PubMed

    Nam, Junghyun; Choo, Kim-Kwang Raymond; Han, Sangchul; Kim, Moonseong; Paik, Juryon; Won, Dongho

    2015-01-01

    A smart-card-based user authentication scheme for wireless sensor networks (hereafter referred to as a SCA-WSN scheme) is designed to ensure that only users who possess both a smart card and the corresponding password are allowed to gain access to sensor data and their transmissions. Despite many research efforts in recent years, it remains a challenging task to design an efficient SCA-WSN scheme that achieves user anonymity. The majority of published SCA-WSN schemes use only lightweight cryptographic techniques (rather than public-key cryptographic techniques) for the sake of efficiency, and have been demonstrated to suffer from the inability to provide user anonymity. Some schemes employ elliptic curve cryptography for better security but require sensors with strict resource constraints to perform computationally expensive scalar-point multiplications; despite the increased computational requirements, these schemes do not provide user anonymity. In this paper, we present a new SCA-WSN scheme that not only achieves user anonymity but also is efficient in terms of the computation loads for sensors. Our scheme employs elliptic curve cryptography but restricts its use only to anonymous user-to-gateway authentication, thereby allowing sensors to perform only lightweight cryptographic operations. Our scheme also enjoys provable security in a formal model extended from the widely accepted Bellare-Pointcheval-Rogaway (2000) model to capture the user anonymity property and various SCA-WSN specific attacks (e.g., stolen smart card attacks, node capture attacks, privileged insider attacks, and stolen verifier attacks). PMID:25849359

  9. High K-alpha X-ray Conversion Efficiency From Extended Source Gas Jet Targets Irradiated by Ultra Short Laser Pulses

    SciTech Connect

    Kugland, N L; Constantin, C; Collette, A; Dewald, E; Froula, D; Glenzer, S H; Kritcher, A; Neumayer, P; Ross, J S; Niemann, C

    2007-11-01

    The absolute laser conversion efficiency to K{sub {alpha}}-like inner shell x-rays (integrated from K{sub {alpha}} to K{sub {beta}}) is observed to be an order of magnitude higher in argon gas jets than in solid targets due to enhanced emission from higher ionization stages following ultra short pulse laser irradiation. Excluding the higher ionization stages, the conversion efficiency to near-cold K{sub {alpha}} is the same in gas jets as in solid targets. These results demonstrate that gas jet targets are bright, high conversion efficiency, high repetition rate, debris-free multi-keV x-ray sources for spectrally resolved scattering and backlighting of rapidly evolving dense matter.

  10. Integration of CdSe/CdSexTe1−x Type-II Heterojunction Nanorods into Hierarchically Porous TiO2 Electrode for Efficient Solar Energy Conversion

    PubMed Central

    Lee, Sangheon; Flanagan, Joseph C.; Kang, Joonhyeon; Kim, Jinhyun; Shim, Moonsub; Park, Byungwoo

    2015-01-01

    Semiconductor sensitized solar cells, a promising candidate for next-generation photovoltaics, have seen notable progress using 0-D quantum dots as light harvesting materials. Integration of higher-dimensional nanostructures and their multi-composition variants into sensitized solar cells is, however, still not fully investigated despite their unique features potentially beneficial for improving performance. Herein, CdSe/CdSexTe1−x type-II heterojunction nanorods are utilized as novel light harvesters for sensitized solar cells for the first time. The CdSe/CdSexTe1−x heterojunction-nanorod sensitized solar cell exhibits ~33% improvement in the power conversion efficiency compared to its single-component counterpart, resulting from superior optoelectronic properties of the type-II heterostructure and 1-octanethiol ligands aiding facile electron extraction at the heterojunction nanorod-TiO2 interface. Additional ~32% enhancement in power conversion efficiency is achieved by introducing percolation channels of large pores in the mesoporous TiO2 electrode, which allow 1-D sensitizers to infiltrate the entire depth of electrode. These strategies combined together lead to 3.02% power conversion efficiency, which is one of the highest values among sensitized solar cells utilizing 1-D nanostructures as sensitizer materials. PMID:26638994

  11. Efficient conversion of polyamides to ω-hydroxyalkanoic acids: a new method for chemical recycling of waste plastics.

    PubMed

    Kamimura, Akio; Ikeda, Kosuke; Suzuki, Shuzo; Kato, Kazunari; Akinari, Yugo; Sugimoto, Tsunemi; Kashiwagi, Kohichi; Kaiso, Kouji; Matsumoto, Hiroshi; Yoshimoto, Makoto

    2014-09-01

    An efficient transformation of polyamides to ω-hydroxy alkanoic acids was achieved. Treatment of nylon-12 with supercritical MeOH in the presence of glycolic acid gave methyl ω-hydroxydodecanoate in 85% yield and the alcohol/alkene selectivity in the product was enhanced to up to 9.5:1. The use of (18)O-enriched acetic acid for the reaction successfully introduced an (18)O atom at the alcoholic OH group in the product. This strategy may provide a new and economical solution for the chemical recycling of waste plastics. PMID:25044218

  12. Titanate cathodes with enhanced electrical properties achieved via growing surface Ni particles toward efficient carbon dioxide electrolysis.

    PubMed

    Gan, Lizhen; Ye, Lingting; Tao, Shanwen; Xie, Kui

    2016-01-28

    Ionic conduction in perovskite oxide is commonly tailored by element doping in lattices to create charge carriers, while few studies have been focused on ionic conduction enhancement through tailoring microstructures. In this work, remarkable enhancement of ionic conduction in titanate has been achieved via in situ growing active nickel nanoparticles on an oxide surface by controlling the oxide material nonstoichiometry. The combined use of XRD, SEM, XPS and EDS indicates that the exsolution/dissolution of the nickel nanoparticles is completely reversible in redox cycles. With the synergetic effect of enhanced ionic conduction of titanate and the presence of catalytic active Ni nanocatalysts, significant improvement of electrocatalytic performances of the titanate cathode is demonstrated. A current density of 0.3 A cm(-2) with a Faradic efficiency of 90% has been achieved for direct carbon dioxide electrolysis in a 2 mm-thick YSZ-supported solid oxide electrolyzer with the modified titanate cathode at 2 V and 1073 K. PMID:26743799

  13. Benefits of Hybrid-Electric Propulsion to Achieve 4x Increase in Cruise Efficiency for a VTOL Aircraft

    NASA Technical Reports Server (NTRS)

    Fredericks, William J.; Moore, Mark D.; Busan, Ronald C.

    2013-01-01

    Electric propulsion enables radical new vehicle concepts, particularly for Vertical Takeoff and Landing (VTOL) aircraft because of their significant mismatch between takeoff and cruise power conditions. However, electric propulsion does not merely provide the ability to normalize the power required across the phases of flight, in the way that automobiles also use hybrid electric technologies. The ability to distribute the thrust across the airframe, without mechanical complexity and with a scale-free propulsion system, is a new degree of freedom for aircraft designers. Electric propulsion is scale-free in terms of being able to achieve highly similar levels of motor power to weight and efficiency across a dramatic scaling range. Applying these combined principles of electric propulsion across a VTOL aircraft permits an improvement in aerodynamic efficiency that is approximately four times the state of the art of conventional helicopter configurations. Helicopters typically achieve a lift to drag ratio (L/D) of between 4 and 5, while the VTOL aircraft designed and developed in this research were designed to achieve an L/D of approximately 20. Fundamentally, the ability to eliminate the problem of advancing and retreating rotor blades is shown, without resorting to unacceptable prior solutions such as tail-sitters. This combination of concept and technology also enables a four times increase in range and endurance while maintaining the full VTOL and hover capability provided by a helicopter. Also important is the ability to achieve low disc-loading for low ground impingement velocities, low noise and hover power minimization (thus reducing energy consumption in VTOL phases). This combination of low noise and electric propulsion (i.e. zero emissions) will produce a much more community-friendly class of vehicles. This research provides a review of the concept brainstorming, configuration aerodynamic and mission analysis, as well as subscale prototype construction and

  14. Variation in the biochemical response to l-thyroxine therapy and relationship with peripheral thyroid hormone conversion efficiency

    PubMed Central

    Midgley, John E M; Larisch, Rolf; Dietrich, Johannes W; Hoermann, Rudolf

    2015-01-01

    Several influences modulate biochemical responses to a weight-adjusted levothyroxine (l-T4) replacement dose. We conducted a secondary analysis of the relationship of l-T4 dose to TSH and free T3 (FT3), using a prospective observational study examining the interacting equilibria between thyroid parameters. We studied 353 patients on steady-state l-T4 replacement for autoimmune thyroiditis or after surgery for malignant or benign thyroid disease. Peripheral deiodinase activity was calculated as a measure of T4–T3 conversion efficiency. In euthyroid subjects, the median l-T4 dose was 1.3 μg/kg per day (interquartile range (IQR) 0.94,1.60). The dose was independently associated with gender, age, aetiology and deiodinase activity (all P<0.001). Comparable FT3 levels required higher l-T4 doses in the carcinoma group (n=143), even after adjusting for different TSH levels. Euthyroid athyreotic thyroid carcinoma patients (n=50) received 1.57 μg/kg per day l-T4 (IQR 1.40, 1.69), compared to 1.19 μg/kg per day (0.85,1.47) in autoimmune thyroiditis (P<0.01, n=76) and 1.08 μg/kg per day (0.82, 1.44) in patients operated on for benign disease (P< 0.01, n=80). Stratifying patients by deiodinase activity categories of <23, 23–29 and >29 nmol/s revealed an increasing FT3–FT4 dissociation; the poorest converters showed the lowest FT3 levels in spite of the highest dose and circulating FT4 (P<0.001). An l-T4-related FT3–TSH disjoint was also apparent; some patients with fully suppressed TSH failed to raise FT3 above the median level. These findings imply that thyroid hormone conversion efficiency is an important modulator of the biochemical response to l-T4; FT3 measurement may be an additional treatment target; and l-T4 dose escalation may have limited success to raise FT3 appropriately in some cases. PMID:26335522

  15. Variation in the biochemical response to l-thyroxine therapy and relationship with peripheral thyroid hormone conversion efficiency.

    PubMed

    Midgley, John E M; Larisch, Rolf; Dietrich, Johannes W; Hoermann, Rudolf

    2015-12-01

    Several influences modulate biochemical responses to a weight-adjusted levothyroxine (l-T4) replacement dose. We conducted a secondary analysis of the relationship of l-T4 dose to TSH and free T3 (FT3), using a prospective observational study examining the interacting equilibria between thyroid parameters. We studied 353 patients on steady-state l-T4 replacement for autoimmune thyroiditis or after surgery for malignant or benign thyroid disease. Peripheral deiodinase activity was calculated as a measure of T4-T3 conversion efficiency. In euthyroid subjects, the median l-T4 dose was 1.3 μg/kg per day (interquartile range (IQR) 0.94,1.60). The dose was independently associated with gender, age, aetiology and deiodinase activity (all P<0.001). Comparable FT3 levels required higher l-T4 doses in the carcinoma group (n=143), even after adjusting for different TSH levels. Euthyroid athyreotic thyroid carcinoma patients (n=50) received 1.57 μg/kg per day l-T4 (IQR 1.40, 1.69), compared to 1.19 μg/kg per day (0.85,1.47) in autoimmune thyroiditis (P<0.01, n=76) and 1.08 μg/kg per day (0.82, 1.44) in patients operated on for benign disease (P< 0.01, n=80). Stratifying patients by deiodinase activity categories of <23, 23-29 and >29 nmol/s revealed an increasing FT3-FT4 dissociation; the poorest converters showed the lowest FT3 levels in spite of the highest dose and circulating FT4 (P<0.001). An l-T4-related FT3-TSH disjoint was also apparent; some patients with fully suppressed TSH failed to raise FT3 above the median level. These findings imply that thyroid hormone conversion efficiency is an important modulator of the biochemical response to l-T4; FT3 measurement may be an additional treatment target; and l-T4 dose escalation may have limited success to raise FT3 appropriately in some cases. PMID:26335522

  16. Enhanced conversion efficiency in dye-sensitized solar cells based on bilayered nano-composite photoanode film consisting of TiO2 nanoparticles and nanofibers.

    PubMed

    Du, P F; Song, L X; Xiong, J

    2014-06-01

    Novel TiO2 nanoparticles/nanofibers (NPs/NFs) bilayered nano-composite photoanode film for dye-sensitized solar cells (DSSCs) was fabricated through the combination of spin-coating and electrospinning. The NPs and NFs layers have complementary roles. The underlaid spin-coated NPs layer provides the photoanode film with higher specific surface area for dye adsorption and improved adhesion to conductive glass substrate. The overlaid electrospun NFs layer endows the photoanode film with better dye-loading and light-harvesting capabilities due to its porous meshwork structure. And the NFs layer also offers larger pore volume, which can facilitate the electrolyte diffusion and the activity regeneration of dye sensitizers. As a result, the electron transport is accelerated while the charge recombination is suppressed. Ascribing to the synergic effect of the NPs and NFs layers, the TiO2 NPs/NFs-based DSSCs achieve a conversion efficiency of 4.46%, which is nearly 14% higher than that of the pure TiO2 NPs-based ones. PMID:24738365

  17. A cascaded QSAR model for efficient prediction of overall power conversion efficiency of all-organic dye-sensitized solar cells.

    PubMed

    Li, Hongzhi; Zhong, Ziyan; Li, Lin; Gao, Rui; Cui, Jingxia; Gao, Ting; Hu, Li Hong; Lu, Yinghua; Su, Zhong-Min; Li, Hui

    2015-05-30

    A cascaded model is proposed to establish the quantitative structure-activity relationship (QSAR) between the overall power conversion efficiency (PCE) and quantum chemical molecular descriptors of all-organic dye sensitizers. The cascaded model is a two-level network in which the outputs of the first level (JSC, VOC, and FF) are the inputs of the second level, and the ultimate end-point is the overall PCE of dye-sensitized solar cells (DSSCs). The model combines quantum chemical methods and machine learning methods, further including quantum chemical calculations, data division, feature selection, regression, and validation steps. To improve the efficiency of the model and reduce the redundancy and noise of the molecular descriptors, six feature selection methods (multiple linear regression, genetic algorithms, mean impact value, forward selection, backward elimination, and +n-m algorithm) are used with the support vector machine. The best established cascaded model predicts the PCE values of DSSCs with a MAE of 0.57 (%), which is about 10% of the mean value PCE (5.62%). The validation parameters according to the OECD principles are R(2) (0.75), Q(2) (0.77), and Qcv2 (0.76), which demonstrate the great goodness-of-fit, predictivity, and robustness of the model. Additionally, the applicability domain of the cascaded QSAR model is defined for further application. This study demonstrates that the established cascaded model is able to effectively predict the PCE for organic dye sensitizers with very low cost and relatively high accuracy, providing a useful tool for the design of dye sensitizers with high PCE. PMID:25773984

  18. Correlating high power conversion efficiency of PTB7:PC71BM inverted organic solar cells with nanoscale structures

    NASA Astrophysics Data System (ADS)

    Das, Sanjib; Keum, Jong K.; Browning, James F.; Gu, Gong; Yang, Bin; Dyck, Ondrej; Do, Changwoo; Chen, Wei; Chen, Jihua; Ivanov, Ilia N.; Hong, Kunlun; Rondinone, Adam J.; Joshi, Pooran C.; Geohegan, David B.; Duscher, Gerd; Xiao, Kai

    2015-09-01

    Advances in material design and device engineering led to inverted organic solar cells (i-OSCs) with superior power conversion efficiencies (PCEs) compared to their ``conventional'' counterparts, in addition to the well-known better ambient stability. Here, we report an in-depth morphology study of the i-OSC active and cathode modifying layers, employing a model system with a well-established bulk-heterojunction, PTB7:PC71BM as the active layer and poly-[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as the cathode surface modifying layer. We have also identified the role of a processing additive, 1,8-diiodooctane (DIO), used in the spin-casting of the active layer to increase PCE. Using various characterization techniques, we demonstrate that the high PCEs of i-OSCs are due to the diffusion of electron-accepting PC71BM into the PFN layer, resulting in improved electron transport. The diffusion occurs when residual solvent molecules in the spun-cast film act as a plasticizer. Addition of DIO to the casting solution results in more PC71BM diffusion and therefore more efficient electron transport. This work provides important insight and guidance to further enhancement of i-OSC performance by materials and interface engineering.Advances in material design and device engineering led to inverted organic solar cells (i-OSCs) with superior power conversion efficiencies (PCEs) compared to their ``conventional'' counterparts, in addition to the well-known better ambient stability. Here, we report an in-depth morphology study of the i-OSC active and cathode modifying layers, employing a model system with a well-established bulk-heterojunction, PTB7:PC71BM as the active layer and poly-[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as the cathode surface modifying layer. We have also identified the role of a processing additive, 1,8-diiodooctane (DIO), used in the spin-casting of the active

  19. Enhanced Power-Conversion Efficiency in Inverted Bulk Heterojunction Solar Cells using Liquid-Crystal-Conjugated Polyelectrolyte Interlayer.

    PubMed

    Liu, Chao; Tan, Yun; Li, Chunquan; Wu, Feiyan; Chen, Lie; Chen, Yiwang

    2015-09-01

    Two novel liquid-crystal-conjugated polyelectrolytes (LCCPEs) poly[9,9-bis[6-(4-cyanobiphenyloxy)-hexyl]-fluorene-alt-9,9-bis(6-(N,N-diethylamino)-hexyl)-fluorene] (PF6Ncbp) and poly[9,9-bis[6-(4-cyanobiphenyloxy)-hexyl]-fluorene-alt-9,9-bis(6-(N-methylimidazole)-hexyl]-fluorene] (PF6lmicbp) are obtained by covalent linkage of the cyanobiphenyl mesogen polar groups onto conjugated polyelectrolytes. After deposition a layer of LCCPEs on ZnO interlayer, the spontaneous orientation of liquid-crystal groups can induce a rearrangement of dipole moments at the interface, subsequently leading to the better energy-level alignment. Moreover, LCCPEs favors intimate interfacial contact between ZnO and the photon harvesting layer and induce active layer to form the nanofibers morphology for the enhancement of charge extraction, transportation and collection. The water/alcohol solubility of the LCCPEs also enables them to be environment-accepted solvent processability. On the basis of these advantages, the poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C60-butyric acid methyl ester (PC60BM)-based inverted polymer solar cells (PSCs) combined with ZnO/PF6Ncbp and ZnO/PF6lmicbp bilayers boost the power conversion efficiency (PCE) to 3.9% and 4.2%, respectively. Incorporation of the ZnO/PF6lmicbp into the devices based on a blend of a narrow band gap polymer thieno[3,4-b]thiophene/benzodithiophene (PTB7) with [6,6]-phenyl C70-butyric acid methyl ester (PC71BM) affords a notable efficiency of 7.6%. PMID:26280810

  20. Correlating High Power Conversion Efficiency of PTB7:PC71BM Inverted Organic Solar Cells with Nanoscale Structures

    DOE PAGESBeta

    Das, Sanjib; Keum, Jong Kahk; Browning, Jim; Gu, Gong; Yang, Bin; Do, Changwoo; Chen, Wei; Chen, Jihua; Ivanov, Ilia N; Hong, Kunlun; et al

    2015-01-01

    Advances in materials design and device engineering led to inverted organic solar cells (i-OSCs) with superior power conversion efficiencies (PCEs) to their conventional counterparts, in addition to the well-known better ambient stability. Despite the significant progress, however, it has so far been unclear how the morphologies of the photoactive layer and its interface with the cathode modifying layer impact device performance. Here, we report an in-depth morphology study of the i-OSC active and cathode modifying layers, employing a model system with the well-established bulk-heterojunction, PTB7:PC71BM as the active layer and poly-[(9,9-bis(3 -(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as the cathode surface modifying layer. Wemore » have also identified the role of a processing additive, 1,8-diiodooctane (DIO), used in the spin-casting of the active layer to increase PCE. Using a variety of characterization techniques, we demonstrate that the high PCEs of i-OSCs are due to the smearing (diffusion) of electron-accepting PC71BM into the PFN layer, resulting in improved electron transport. The PC71BM diffusion occurs after spin-casting the active layer onto the PFN layer, when residual solvent molecules act as a plasticizer. The DIO additive, with a higher boiling point than the host solvent, has a longer residence time in the spin-cast active layer, resulting in more PC71BM smearing and therefore more efficient electron transport. This work provides important insight and guidance to further enhancement of i-OSC performance by materials and interface engineering.« less

  1. Power conversion efficiency enhancement of polymer solar cells using MoO3/TFB as hole transport layer

    NASA Astrophysics Data System (ADS)

    Zheng, Qiao; Sun, Jianbin; Cheng, Shuying; Lai, Yunfeng; Zhou, Haifang; Yu, Jinling

    2015-09-01

    In this paper, we report a simple method to increase the power conversion efficiency (PCE) of the polymer solar cells based on poly(3-hexylthiophene) and [6, 6]-phenyl-C61-butyric acid methyl ester derivatives blended active layer. The approach includes using a molybdenum oxide (MoO3) and Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4-( N-(4-sec-butylphenyl))diphenylamine)] (TFB) composites as the hole transport layer (HTL). Compared with that of the device with bare MoO3 HTL, the maximum 39 % increased of PCE is obtained when MoO3/TFB composites as the HTL in the devices. The device with MoO3/TFB shows the best performance with a PCE of 3.70 %, an open-circuit voltage of 0.58 V, and a short-circuit current density of 11.39 mA/cm2. The intrinsically mechanisms behind PCE increased are due to the improvement in the interface layer morphology and the more appropriately energy level of the cells.

  2. High power laser-driven ceramic phosphor plate for outstanding efficient white light conversion in application of automotive lighting

    PubMed Central

    Song, Young Hyun; Ji, Eun Kyung; Jeong, Byung Woo; Jung, Mong Kwon; Kim, Eun Young; Yoon, Dae Ho

    2016-01-01

    We report on Y3Al5O12: Ce3+ ceramic phosphor plate (CPP) using nano phosphor for high power laser diode (LD) application for white light in automotive lighting. The prepared CPP shows improved luminous properties as a function of Ce3+ concentration. The luminous properties of the Y3Al5O12: Ce3+ CPP nano phosphor are improved when compared to the Y3Al5O12: Ce3+ CPP with bulk phosphor, and hence, the luminous emittance, luminous flux, and conversion efficiency are improved. The Y3Al5O12: Ce3+ CPP with an optimal Ce3+ content of 0.5 mol % shows 2733 lm/mm2 value under high power blue radiant flux density of 19.1 W/mm2. The results indicate that Y3Al5O12: Ce3+ CPP using nano phosphor can serve as a potential material for solid-state laser lighting in automotive applications. PMID:27502730

  3. High power laser-driven ceramic phosphor plate for outstanding efficient white light conversion in application of automotive lighting

    NASA Astrophysics Data System (ADS)

    Song, Young Hyun; Ji, Eun Kyung; Jeong, Byung Woo; Jung, Mong Kwon; Kim, Eun Young; Yoon, Dae Ho

    2016-08-01

    We report on Y3Al5O12: Ce3+ ceramic phosphor plate (CPP) using nano phosphor for high power laser diode (LD) application for white light in automotive lighting. The prepared CPP shows improved luminous properties as a function of Ce3+ concentration. The luminous properties of the Y3Al5O12: Ce3+ CPP nano phosphor are improved when compared to the Y3Al5O12: Ce3+ CPP with bulk phosphor, and hence, the luminous emittance, luminous flux, and conversion efficiency are improved. The Y3Al5O12: Ce3+ CPP with an optimal Ce3+ content of 0.5 mol % shows 2733 lm/mm2 value under high power blue radiant flux density of 19.1 W/mm2. The results indicate that Y3Al5O12: Ce3+ CPP using nano phosphor can serve as a potential material for solid-state laser lighting in automotive applications.

  4. Photosynthetic energy conversion efficiency: setting a baseline for gauging future improvements in important food and biofuel crops.

    PubMed

    Slattery, Rebecca A; Ort, Donald R

    2015-06-01

    The conversion efficiency (ε(c)) of absorbed radiation into biomass (MJ of dry matter per MJ of absorbed photosynthetically active radiation) is a component of yield potential that has been estimated at less than half the theoretical maximum. Various strategies have been proposed to improve ε(c), but a statistical analysis to establish baseline ε(c) levels across different crop functional types is lacking. Data from 164 published ε(c) studies conducted in relatively unstressed growth conditions were used to determine the means, greatest contributors to variation, and genetic trends in ε(c )across important food and biofuel crop species. ε(c) was greatest in biofuel crops (0.049-0.066), followed by C4 food crops (0.046-0.049), C3 nonlegumes (0.036-0.041), and finally C3 legumes (0.028-0.035). Despite confining our analysis to relatively unstressed growth conditions, total incident solar radiation and average growing season temperature most often accounted for the largest portion of ε(c) variability. Genetic improvements in ε(c), when present, were less than 0.7% per year, revealing the unrealized potential of improving ε(c) as a promising contributing strategy to meet projected future agricultural demand. PMID:25829463

  5. Contributions of Ag Nanowires to the Photoelectric Conversion Efficiency Enhancement of TiO2 Dye-Sensitized Solar Cells.

    PubMed

    Liu, Yunyu; She, Guangwei; Qi, Xiaopeng; Mu, Lixuan; Wang, Xuesong; Shi, Wensheng

    2015-09-01

    Ag nanowires (AgNWs) were employed in mesoporous TiO2 dye-sensitized solar cells (DSSCs) to enhance the photoelectric conversion efficiency (PCE). The possible reasons for PCE improvement, i.e., improvement in electron transport and light harvesting due to light scattering and plasmonic resonance effect of AgNWs are investigated. Electrochemical impedance spectra (EIS) study proved that addition of AgNWs can enhance the conductivity of TiO2 thin film photoanode, which is an important reason for the increase of photocurrent. Furthermore, through the comparison experiments as well as the UV-Vis absorption and IPCE characterization, contributions of the light scattering and plasmonic resonance effect to the enhancement of light harvest, and thus PCE of the DSSCs were demonstrated. It was found that fast electron transport of AgNWs played more important role for the PCE improvement than the light harvest enhancement due to light scattering and plasmonic effect. Based on these investigations, the AgNWs modified TiO2 thin film DSSCs were optimized. After integrating AgNWs into the photoanode, the photocurrent increased significantly and PCE increased -50% comparing with the pure TiO2-based DSSCs. PMID:26716285

  6. Effect of space layer doping on photoelectric conversion efficiency of InAs/GaAs quantum dot solar cells

    NASA Astrophysics Data System (ADS)

    Lee, Kyoung Su; Lee, Dong Uk; Kim, Eun Kyu; Choi, Won Jun

    2015-11-01

    We report an effect of photoelectric conversion efficiency (PCE) by space layer doping in InAs/GaAs quantum dot solar cells (QDSC) and δ-doped QDSC grown by molecular beam epitaxy. The PCEs of QDSC and δ-doped QDSC without anti-reflection coating were 10.8% and 4.3%, respectively. The QDSC had about four electrons per QD, and its ideality factor was temperature-independent, which implies that recombination of electron-hole pairs is suppressed by strong potential barriers around charged dots. From the deep level transient spectroscopy measurements, four defect levels, including QD with the activation energy ranges from 0.08 eV to 0.50 eV below GaAs conduction band edge, appeared. Especially, the M1 defect (Ec-0.14 eV) was newly formed in δ-doped QDSC and its density was higher than those of M3 (Ec-0.35 eV) and M4 (Ec-0.50 eV) levels in QDSC. These results suggest that the photo-carriers recombining at M1 defect might be responsible for the reduction of PCE in δ-doped QDSC.

  7. Effect of space layer doping on photoelectric conversion efficiency of InAs/GaAs quantum dot solar cells

    SciTech Connect

    Lee, Kyoung Su; Lee, Dong Uk; Kim, Eun Kyu; Choi, Won Jun

    2015-11-16

    We report an effect of photoelectric conversion efficiency (PCE) by space layer doping in InAs/GaAs quantum dot solar cells (QDSC) and δ-doped QDSC grown by molecular beam epitaxy. The PCEs of QDSC and δ-doped QDSC without anti-reflection coating were 10.8% and 4.3%, respectively. The QDSC had about four electrons per QD, and its ideality factor was temperature-independent, which implies that recombination of electron-hole pairs is suppressed by strong potential barriers around charged dots. From the deep level transient spectroscopy measurements, four defect levels, including QD with the activation energy ranges from 0.08 eV to 0.50 eV below GaAs conduction band edge, appeared. Especially, the M1 defect (E{sub c}-0.14 eV) was newly formed in δ-doped QDSC and its density was higher than those of M3 (E{sub c}-0.35 eV) and M4 (E{sub c}-0.50 eV) levels in QDSC. These results suggest that the photo-carriers recombining at M1 defect might be responsible for the reduction of PCE in δ-doped QDSC.

  8. Near-infrared quarter-waveplate with near-unity polarization conversion efficiency based on silicon nanowire array.

    PubMed

    Dai, Yanmeng; Cai, Hongbing; Ding, Huaiyi; Ning, Zhen; Pan, Nan; Zhu, Hong; Shi, Qinwei; Wang, Xiaoping

    2015-04-01

    Metasurfaces made of subwavelength resonators can modify the wave front of light within the thickness much less than free space wavelength, showing great promises in integrated optics. In this paper, we theoretically show that electric and magnetic resonances supported simultaneously by a subwavelength nanowire with high refractive-index can be utilized to design metasurfaces with near-unity transmittance. Taking silicon nanowire for instance, we design numerically a near-infrared quarter-waveplate with high transmittance using a subwavelength nanowire array. The operation bandwidth of the waveplate is 0.14 μm around the center wavelength of 1.71 μm. The waveplate can convert a 45° linearly polarized incident light to circularly polarized light with conversion efficiency ranging from 94% to 98% over the operation band. The performance of quarter waveplate can in principle be tuned and improved through optimizing the parameters of nanowire arrays. Its compatibility to microelectronic technologies opens up a distinct possibility to integrate nanophotonics into the current silicon-based electronic devices. PMID:25968730

  9. Photosynthetic Energy Conversion Efficiency: Setting a Baseline for Gauging Future Improvements in Important Food and Biofuel Crops1

    PubMed Central

    2015-01-01

    The conversion efficiency (εc) of absorbed radiation into biomass (MJ of dry matter per MJ of absorbed photosynthetically active radiation) is a component of yield potential that has been estimated at less than half the theoretical maximum. Various strategies have been proposed to improve εc, but a statistical analysis to establish baseline εc levels across different crop functional types is lacking. Data from 164 published εc studies conducted in relatively unstressed growth conditions were used to determine the means, greatest contributors to variation, and genetic trends in εc across important food and biofuel crop species. εc was greatest in biofuel crops (0.049–0.066), followed by C4 food crops (0.046–0.049), C3 nonlegumes (0.036–0.041), and finally C3 legumes (0.028–0.035). Despite confining our analysis to relatively unstressed growth conditions, total incident solar radiation and average growing season temperature most often accounted for the largest portion of εc variability. Genetic improvements in εc, when present, were less than 0.7% per year, revealing the unrealized potential of improving εc as a promising contributing strategy to meet projected future agricultural demand. PMID:25829463

  10. High power laser-driven ceramic phosphor plate for outstanding efficient white light conversion in application of automotive lighting.

    PubMed

    Song, Young Hyun; Ji, Eun Kyung; Jeong, Byung Woo; Jung, Mong Kwon; Kim, Eun Young; Yoon, Dae Ho

    2016-01-01

    We report on Y3Al5O12: Ce(3+) ceramic phosphor plate (CPP) using nano phosphor for high power laser diode (LD) application for white light in automotive lighting. The prepared CPP shows improved luminous properties as a function of Ce(3+) concentration. The luminous properties of the Y3Al5O12: Ce(3+) CPP nano phosphor are improved when compared to the Y3Al5O12: Ce(3+) CPP with bulk phosphor, and hence, the luminous emittance, luminous flux, and conversion efficiency are improved. The Y3Al5O12: Ce(3+) CPP with an optimal Ce(3+) content of 0.5 mol % shows 2733 lm/mm(2) value under high power blue radiant flux density of 19.1 W/mm(2). The results indicate that Y3Al5O12: Ce(3+) CPP using nano phosphor can serve as a potential material for solid-state laser lighting in automotive applications. PMID:27502730

  11. Solar energy conversion via internal photoemission in aluminum, copper, and silver: Band structure effects and theoretical efficiency estimates

    NASA Astrophysics Data System (ADS)

    Chang, Yin-Jung; Shih, Ko-Han

    2016-05-01

    Internal photoemission (IPE) across an n-type Schottky junction due to standard AM1.5G solar illumination is quantified with practical considerations for Cu, Ag, and Al under direct and fully nondirect transitions, all in the context of the constant matrix element approximation. Under direct transitions, photoemitted electrons from d bands dominate the photocurrent and exhibit a strong dependence on the barrier energy ΦB but are less sensitive to the change in the metal thickness. Photocurrent is shown to be nearly completely contributed by s-state electrons in the fully nondirect approximation that offers nearly identical results as in the direct transition for metals having a free-electron-like band structure. Compared with noble metals, Al-based IPE has the highest quantum yield up to about 5.4% at ΦB = 0.5 eV and a maximum power conversion efficiency of approximately 0.31% due mainly to its relatively uniform and wide Pexc energy spectral width. Metals (e.g., Ag) with a larger interband absorption edge are shown to outperform those with shallower d-bands (e.g., Cu and Au).

  12. Problems of efficiency of photoelectric conversion in thin-film CdS/CdTe solar cells

    SciTech Connect

    Kosyachenko, L. A.

    2006-06-15

    The available data are generalized and new results of investigation of losses of photoelectric energy conversion in CdS/CdTe thin-film solar cells are reported. The requirements concerning the electrical characteristics of the material, for minimizing the electric losses and providing effective radiation absorption in the active region of the diode structure, are discussed and refined. It is shown to what extent the incomplete collection of photogenerated charge carriers is determined by recombination both at the CdS/CdTe interface (based on the continuity equation taking into account the surface recombination) and in the space-charge region (based on the Hecht equation). The comparison of the calculated and experimental results shows that, in general, both types of recombination losses are important but can be virtually eliminated by the choice of parameters of both the barrier structure and the material used. The limiting values of the short-circuit current density and efficiency of the CdS/CdTe solar cell are discussed.

  13. Efficient thermoelectric energy conversion in Pb0.95Mn0.05Te p-n couple

    NASA Astrophysics Data System (ADS)

    Dybko, K.; Szot, M.; Mycielski, A.; Szczerbakow, A.; Dziawa, P.; Guziewicz, M.; Knoff, W.; Łusakowska, E.; Story, T.

    2016-03-01

    We demonstrate an efficient energy conversion in a p-n thermoelectric couple built of bulk Pb0.95Mn0.05Te crystals grown by the Bridgman method and heavily doped n-type with Bi ( n =1.9 ×1019cm-3 ) or p-type with Na ( p =2.3 ×1019cm-3 ). Substitution of Mn2+ ions for Pb2+ ions at the rock-salt lattice cation sites increases the band gap of Pb1-xMnxTe and decreases the energy separation between the light hole L-band and the heavy hole Σ-band. It results in a large increase of thermoelectric power and improved thermoelectric parameters of p-type Pb1-xMnxTe. Applying the Harman method for samples of various lengths, we experimentally determined the radiation correction factors and found the thermoelectric figure of merit parameter Z T =0.75 -0.8 at T =650 K for both n- and p-type materials with good thermoelectric matching of the couple. We report on thermoelectric performance of a p-n thermoelectric couple assembled of these materials and tested over the T =300 -670 K temperature region.

  14. Hierarchically Structured ZnO Film for Dye-Sensitized Solar Cells with Enhanced Energy Conversion Efficiency

    SciTech Connect

    Chou, Tammy P.; Zhang, Qifeng; Fryxell, Glen E.; Cao, Guozhong

    2007-09-17

    The interest in dye-sensitized solar cells has increased due to reduced energy sources and higher energy production costs. For the most part, titania (TiO2) has been the material of choice for dye-sensitized solar cells and so far have shown to exhibit the highest overall light conversion efficiency ~ 11%.[1] However, zinc oxide (ZnO) has recently been explored as an alternative material in dye-sensitized solar cells with great potential.[2] The main reasons for this increase in research surrounding ZnO material include: 1) ZnO having a band gap similar to that for TiO2 at 3.2 eV,[3] and 2) ZnO having a much higher electron mobility ~ 115-155 cm2/Vs[4] than that for anatase titania (TiO2), which is reported to be ~ 10-5 cm2/Vs.[5] In addition, ZnO has a few advantages as the semiconductor electrode when compared to TiO2, including 1) simpler tailoring of the nanostructure as compared to TiO2, and 2) easier modification of the surface structure. These advantages[6] are thought to provide a promising means for improving the solar cell performance of the working electrode in dye-sensitized solar cells.

  15. Near-ultraviolet LED of the External Quantum Efficiency Over 45% and its Application to High-color Rendering Phosphor Conversion White LEDs

    NASA Astrophysics Data System (ADS)

    Sakuta, Hiroaki; Fukui, Takeshi; Miyachi, Tsutomu; Kamon, Kunihito; Hayashi, Hideki; Nakamura, Nobutaka; Uchida, Yuji; Kurai, Satoshi; Taguchi, Tsunemasa

    Highly luminous efficiency and color rendering index (CRI) of 70 lm/W and 95 under low correlated color temperature (CCT) of 3177 K has been obtained by phosphor conversion (PC) white light-emitting diodes (LEDs) using near-ultra violet (n-UV) LEDs with the external quantum efficiency (EQE) of 46.7%. The homogeneous spatial color uniformity on chromaticity of PC white LEDs excited by n-UV LEDs are particularly adequate to the general lighting applications.

  16. Enhancement of conversion efficiency of extreme ultraviolet radiation from a liquid aqueous solution microjet target by use of dual laser pulses

    NASA Astrophysics Data System (ADS)

    Higashiguchi, Takeshi; Dojyo, Naoto; Hamada, Masaya; Kawasaki, Keita; Sasaki, Wataru; Kubodera, Shoichi

    2006-03-01

    We demonstrated a debris-free, efficient laser-produced plasma extreme ultraviolet (EUV) source by use of a regenerative liquid microjet target containing tin-dioxide (SnO II) nano-particles. By using a low SnO II concentration (6%) solution and dual laser pulses for the plasma control, we observed the EUV conversion efficiency of 1.2% with undetectable debris.

  17. Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings.

    PubMed

    Zahran, Zaki N; Mohamed, Eman A; Naruta, Yoshinori

    2016-01-01

    Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe-containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push-pull mechanism. Bio-inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe-Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe-Fe separation distance. PMID:27087483

  18. High partial feed conversion efficiency appears to be a persistent trait associated with reduction in selected measures of methane emissions in dairy cattle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the United States enteric methane (CH4) contributes approximately 21% of all anthropogenic CH4 emissions. Alongside dietary manipulations, exploiting among-animal variation in feed conversion efficiency (FCE) may offer possible CH4 mitigation strategies. This experiment was designed to evaluate t...

  19. Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings

    PubMed Central

    Zahran, Zaki N.; Mohamed, Eman A.; Naruta, Yoshinori

    2016-01-01

    Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe−containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push−pull mechanism. Bio−inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe−Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe−Fe separation distance. PMID:27087483

  20. Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings

    NASA Astrophysics Data System (ADS)

    Zahran, Zaki N.; Mohamed, Eman A.; Naruta, Yoshinori

    2016-04-01

    Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe‑containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push‑pull mechanism. Bio‑inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe‑Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe‑Fe separation distance.

  1. Efficient H/sub 2/ Raman conversion of long-pulse XeF laser radiation into blue-green region

    SciTech Connect

    Komine, H.; Stappaerts, E.A.; Brosnan, S.J.; West, J.B.

    1982-04-01

    Efficient Raman conversion of microsecond pulse XeF laser radiation into the blue-green region via the second Stokes shift in hydrogen has been demonstrated using a Raman oscillator-amplifier scheme. Strong depletion of the pump and the first Stokes radiation accompanied by a dominant second Stokes output was observed for the first time.

  2. Analyzing the possibility of achieving more efficient cooling of water in the evaporative cooling towers of the Armenian NPP

    NASA Astrophysics Data System (ADS)

    Petrosyan, V. G.; Yeghoyan, E. A.

    2015-10-01

    The specific features of the service cooling water system used at the Armenian NPP and modifications made in the arrangement for supplying water to the water coolers in order to achieve more efficient cooling are presented. The mathematical model applied in carrying out the analyses is described, the use of which makes it possible to investigate the operation of parallel-connected cooling towers having different hydraulic and thermal loads. When the third standby cooling tower is put into operation (with the same flow rate of water supplied to the water coolers), the cooled water temperature is decreased by around 2-3°C in the range of atmospheric air temperatures 0-35°C. However, the introduced water distribution arrangement with a decreased spraying density has limitation on its use at negative outdoor air temperatures due to the hazard intense freezing of the fill in the cooling tower peripheral zone. The availability of standby cooling towers in the shutdown Armenian NPP power unit along with the planned full replacement of the cooling tower process equipment create good possibilities for achieving a deeper water cooling extent and better efficiency of the NPP. The present work was carried out with the aim of achieving maximally efficient use of existing possibilities and for elaborating the optimal cooling tower modernization version. Individual specific heat-andmass transfer processes in the chimney-type evaporative cooling towers are analyzed. An improved arrangement for distributing cooled water over the cooling tower spraying area (during its operation with a decreased flow rate) is proposed with the aim of cooling water to a deeper extent and preserving the possibility of using the cooling towers in winter. The main idea behind improving the existing arrangement is to exclude certain zones of the cooling tower featuring inefficient cooling from operation. The effectiveness of introducing the proposed design is proven by calculations (taking as an

  3. Efficient conversion of crude glycerol from various industrial wastes into single cell oil by yeast Yarrowia lipolytica.

    PubMed

    Dobrowolski, Adam; Mituła, Paweł; Rymowicz, Waldemar; Mirończuk, Aleksandra M

    2016-05-01

    In this study, crude glycerol from various industries was used to produce lipids via wild type Yarrowia lipolytica A101. We tested samples without any prior purification from five different waste products; each contained various concentrations of glycerol (42-87%) as the sole carbon source. The best results for lipid production were obtained for medium containing glycerol from fat saponification. This reached 1.69gL(-1) (25% of total cell dry weight) with a biomass yield of 0.17gg(-1) in the flasks experiment. The batch cultivation in a bioreactor resulted in enhanced lipid production-it achieved 4.72gL(-1) with a biomass yield 0.21gg(-1). Moreover, the properly selected batch of crude glycerol provides a defined fatty acid composition. In summary, this paper shows that crude glycerol from soap production could be efficiently converted to single cell oil without any prior purification. PMID:26890799

  4. Babesia and its hosts: adaptation to long-lasting interactions as a way to achieve efficient transmission

    PubMed Central

    Chauvin, Alain; Moreau, Emmanuelle; Bonnet, Sarah; Plantard, Olivier; Malandrin, Laurence

    2009-01-01

    Babesia, the causal agent of babesiosis, are tick-borne apicomplexan protozoa. True babesiae (Babesia genus sensu stricto) are biologically characterized by direct development in erythrocytes and by transovarial transmission in the tick. A large number of true Babesia species have been described in various vertebrate and tick hosts. This review presents the genus then discusses specific adaptations of Babesia spp. to their hosts to achieve efficient transmission. The main adaptations lead to long-lasting interactions which result in the induction of two reservoirs: in the vertebrate host during low long-term parasitemia and throughout the life cycle of the tick host as a result of transovarial and transstadial transmission. The molecular bases of these adaptations in vertebrate hosts are partially known but few of the tick-host interaction mechanisms have been elucidated. PMID:19379662

  5. Feed conversion efficiency in dairy cows: Repeatability, variation in digestion and metabolism of energy and nitrogen, and ruminal methanogens.

    PubMed

    Arndt, C; Powell, J M; Aguerre, M J; Crump, P M; Wattiaux, M A

    2015-06-01

    The objective was to study repeatability and sources of variation in feed conversion efficiency [FCE, milk kg/kg dry matter intake (DMI)] of lactating cows in mid to late lactation. Trials 1 and 2 used 16 cows (106 to 368 d in milk) grouped in 8 pairs of 1 high- and 1 low-FCE cow less than 16 d in milk apart. Trial 1 determined the repeatability of FCE during a 12-wk period. Trial 2 quantified the digestive and metabolic partitioning of energy and N with a 3-d total fecal and urine collection and measurement of CH4 and CO2 emission. Trial 3 studied selected ruminal methanogens in 2 pairs of cows fitted with rumen cannulas. Cows received a single diet including 28% corn silage, 27% alfalfa silage, 17% crude protein, and 28% neutral detergent fiber (dry matter basis). In trial 1, mean FCE remained repeatedly different and averaged 1.83 and 1.03 for high- and low-FCE cows, respectively. In trial 2, high-FCE cows consumed 21% more DMI, produced 98% more fat- and protein-corrected milk, excreted 42% less manure per kilogram of fat- and protein-corrected milk, but emitted the same daily amount of CH4 and CO2 compared with low-FCE cows. Percentage of gross energy intake lost in feces was higher (28.6 vs. 25.9%), but urinary (2.76 vs. 3.40%) and CH4 (5.23 vs. 6.99%) losses were lower in high- than low-FCE cows. Furthermore, high-FCE cows partitioned 15% more of gross energy intake toward net energy for maintenance, body gain, and lactation (37.5 vs. 32.6%) than low-FCE cows. Lower metabolic efficiency and greater heat loss in low-FCE cows might have been associated in part with greater energy demand for immune function related to subclinical mastitis, as somatic cell count was 3.8 fold greater in low- than high-FCE cows. As a percentage of N intake, high-FCE cows tended to have greater fecal N (32.4 vs. 30.3%) and had lower urinary N (32.2 vs. 41.7%) and greater milk N (30.3 vs. 19.1%) than low-FCE cows. In trial 3, Methanobrevibacter spp. strain AbM4 was less prevalent in

  6. High efficiency on-chip three wave parametric frequency conversion and its applications in both classical and quantum optics

    NASA Astrophysics Data System (ADS)

    Guo, Xiang; Zou, Changling; Schuck, Carsten; Jung, Hojoong; Cheng, Risheng; Tang, Hong X.

    Second order nonlinearity (?(2)) is one of the most widely explored properties in photonics. Integrating nonlinear devices on a photonic chip attracts more and more attention due to the devices' small foot-print and large scalability. However, ?(2) nonlinearity in a scalable platform is normally believed to be weak due to difficulties in finding a suitable material with both high nonlinearity and compatibility with advanced nanofabrication technologies. Aluminum nitride is newly developed as a material combining such two properties: high nonlinearity in low-loss, small foot-print waveguide circuits. In experiment, we fabricate microring resonator devices supporting both telecom and visible modes and achieve exceptionally large second harmonic generation efficiency. High quality photon pair generation is further demonstrated with a generation rate of 3 MHz/mW for degenerate photon pair and 5.8 MHz/mW for non-degenerate photon pair. Furthermore, the strong nonlinearity results in coherent interaction between two spectraly far-away modes which manifest as a nonlinear optic induced transparency and efficient frequency converter. We envision more interesting and important applications in the AlN platform combining its outstanding linear and nonlinear properties.

  7. SnO2-based dye-sensitized hybrid solar cells exhibiting near unity absorbed photon-to-electron conversion efficiency.

    PubMed

    Snaith, Henry J; Ducati, Caterina

    2010-04-14

    Improving the solar light harvesting and photon-to-electron conversion efficiency for hybrid, organic-inorganic photovoltaics are critical challenges. Titania based solid-state hybrid solar cells are moderately efficient at converting visible photons to electrons, but major electrical losses still remain. A material based paradigm shift is required to dramatically enhance the performance of these devices. Here, we present an investigation into solid-state dye-sensitized solar cells (SDSCs) incorporating a molecular hole-transporter and mesoporous tin oxide electrodes, in place of titania usually employed. We investigate the influence of treating the surface of the SnO(2) with different oxides and find that MgO "passivated" SnO(2) electrodes demonstrate an unprecedented absorbed photon-to-electron conversion efficiency of near unity across a broad spectral range. A dual surface treatment of TiO(2) followed by MgO enables tuning of the solar cell photovoltage, fill factor, and efficiency with visible light absorbing cells delivering 3% solar-to-electrical full sun power conversion efficiency. PMID:20302336

  8. Advanced techniques in laser-ion acceleration: Conversion efficiency, beam distribution and energy scaling in the Break-Out Afterburner regime

    NASA Astrophysics Data System (ADS)

    Jung, Daniel; Yin, Lin; Albright, Brian; Gautier, Donald; Hoerlein, Rainer; Johnson, Randall; Kiefer, Daniel; Letzring, Sam; Shah, Rahul; Palaniyappan, Sasikumar; Shimada, Tsutomu; Habs, Dietrich; Fernandez, Juan; Hegelich, Manuel

    2011-10-01

    Recently, increasing laser intensities and contrast made acceleration mechanisms such as the radiation pressure acceleration or the Break-Out Afterburner (BOA) accessible. These mechanisms efficiently couple laser energy into all target ion species, making them a competitive alternative to conventional accelerators. We here present experimental data addressing conversion efficiency and ion distribution scaling for both carbon C6+ and protons within the BOA regime and the transit into the TNSA regime. Unique high resolution measurements of angularly resolved carbon C6+ and proton energy spectra for targets ranging from 30nm to 25microns - recorded with a novel ion wide angle spectrometer - are presented and used to derive thickness scaling estimates. While the measured conversion efficiency for C6+ reaches up to ~6%, peak energies of 1GeV and 120MeV have been measured for C6+ and protons, respectively.

  9. Direct Conversion of CH3NH3PbI3 from Electrodeposited PbO for Highly Efficient Planar Perovskite Solar Cells

    PubMed Central

    Huang, Jin-hua; Jiang, Ke-jian; Cui, Xue-ping; Zhang, Qian-qian; Gao, Meng; Su, Mei-ju; Yang, Lian-ming; Song, Yanlin

    2015-01-01

    Organic-inorganic hybrid perovskite materials have recently been identified as a promising light absorber for solar cells. In the efficient solar cells, the perovskite active layer has generally been fabricated by either vapor deposition or two-step sequential deposition process. Herein, electrochemically deposited PbO film is in situ converted into CH3NH3PbI3 through solid-state reaction with adjacent CH3NH3I layer, exhibiting a large-scale flat and uniform thin film with fully substrate coverage. The resultant planar heterojunction photovoltaic device yields a best power conversion efficiency of 14.59% and an average power conversion efficiency of 13.12 ± 1.08% under standard AM 1.5 conditions. This technique affords a facile and environment-friendly method for the fabrication of the perovskite based solar cells with high reproducibility, paving the way for the practical application. PMID:26510520

  10. Cu7.2S4 nanocrystals: a novel photothermal agent with a 56.7% photothermal conversion efficiency for photothermal therapy of cancer cells.

    PubMed

    Li, Bo; Wang, Qian; Zou, Rujia; Liu, Xijian; Xu, Kaibing; Li, Wenyao; Hu, Junqing

    2014-03-21

    Copper sulphides, as a novel kind of photothermal agent for photothermal therapy (PTT) of cancer cells, have attracted increasing attention in recent years due to good photostability, synthetic simplicity, low toxicity and low cost. However, the unsatisfactory photothermal conversion efficiency of copper sulphides limits their bioapplication as PTT agents. Herein, Cu7.2S4 NCs with a mean size of ∼20 nm as a novel photothermal agent have been prepared by a simple thermal decomposition route. Moreover, these NCs exhibit strong near-infrared (NIR) absorption, good photostability and significant photothermal conversion efficiency up to 56.7% due to strong NIR absorption, good dispersity and suitable size. Importantly, these NCs can be very compatibly used as a 980 nm laser-driven PTT agent for the efficient PTT of cancer cells in vitro and in vivo. PMID:24509646

  11. Efficiency of non-linear frequency conversion of double-scale pico-femtosecond pulses of passively mode-locked fiber laser.

    PubMed

    Smirnov, Sergey V; Kobtsev, Sergey M; Kukarin, Sergey V

    2014-01-13

    For the first time we report the results of both numerical simulation and experimental observation of second-harmonic generation as an example of non-linear frequency conversion of pulses generated by passively mode-locked fiber master oscillator in different regimes including conventional (stable) and double-scale (partially coherent and noise-like) ones. We show that non-linear frequency conversion efficiency of double-scale pulses is slightly higher than that of conventional picosecond laser pulses with the same energy and duration despite strong phase fluctuations of double-scale pulses. PMID:24515065

  12. Efficient Conversion of CO₂ to CO Using Tin and Other Inexpensive and Easily Prepared Post-Transition Metal Catalysts.

    PubMed

    Medina-Ramos, Jonnathan; Pupillo, Rachel C; Keane, Thomas P; DiMeglio, John L; Rosenthal, Joel

    2015-04-22

    The development of affordable electrocatalysts that can drive the reduction of CO2 to CO with high selectivity, efficiency, and large current densities is a critical step on the path to production of liquid carbon-based fuels. In this work, we show that inexpensive triflate salts of Sn(2+), Pb(2+), Bi(3+), and Sb(3+) can be used as precursors for the electrodeposition of CO2 reduction cathode materials from MeCN solutions, providing a general and facile electrodeposition strategy, which streamlines catalyst synthesis. The ability of these four platforms to drive the formation of CO from CO2 in the presence of [BMIM]OTf was probed. The electrochemically prepared Sn and Bi catalysts proved to be highly active, selective, and robust platforms for CO evolution, with partial current densities of jCO = 5-8 mA/cm(2) at applied overpotentials of η < 250 mV. By contrast, the electrodeposited Pb and Sb catalysts do not promote rapid CO generation with the same level of selectivity. The Pb material is only ∼10% as active as the Sn and Bi systems at an applied potential of E = -1.95 V and is rapidly passivated during catalysis. The Sb-comprised cathode material shows no activity for conversion of CO2 to CO under analogous conditions. When taken together, this work demonstrates that 1,3-dialkylimidazoliums can promote CO production, but only when used in combination with an appropriately chosen electrocatalyst material. More broadly, these results suggest that the interactions between CO2, the imidazolium promoter, and the cathode surface are all critical to the observed catalysis. PMID:25697668

  13. Efficient Conversion of CO2 to CO Using Tin and Other Inexpensive and Easily Prepared Post-Transition Metal Catalysts

    DOE PAGESBeta

    Medina-Ramos, Jonnathan; Pupillo, Rachel C.; Keane, Thomas P.; DiMeglio, John L.; Rosenthal, Joel

    2015-02-19

    The development of affordable electrocatalysts that can drive the reduction of CO2 to CO with high selectivity, efficiency, and large current densities is a critical step on the path to production of liquid carbon-based fuels. In this work, we show that inexpensive triflate salts of Sn2+, Pb2+, Bi3+, and Sb3+ can be used as precursors for the electrodeposition of CO2 reduction cathode materials from MeCN solutions, providing a general and facile electrodeposition strategy, which streamlines catalyst synthesis. The ability of these four platforms to drive the formation of CO from CO2 in the presence of [BMIM]OTf was probed. The electrochemicallymore » prepared Sn and Bi catalysts proved to be highly active, selective, and robust platforms for CO evolution, with partial current densities of jCO = 5-8 mA/cm2 at applied overpotentials of η < 250 mV. By contrast, the electrodeposited Pb and Sb catalysts do not promote rapid CO generation with the same level of selectivity. The Pb material is only ~10% as active as the Sn and Bi systems at an applied potential of E = -1.95 V and is rapidly passivated during catalysis. The Sb-comprised cathode material shows no activity for conversion of CO2 to CO under analogous conditions. When taken together, this work demonstrates that 1,3-dialkylimidazoliums can promote CO production, but only when used in combination with an appropriately chosen electrocatalyst material. More broadly, these results suggest that the interactions between CO2, the imidazolium promoter, and the cathode surface are all critical to the observed catalysis.« less

  14. Effects of feed intake and genetics on tissue nitrogen-15 enrichment and feed conversion efficiency in sheep.

    PubMed

    Cheng, L; Logan, C M; Dewhurst, R J; Hodge, S; Zhou, H; Edwards, G R

    2015-12-01

    This study investigated the effects of sheep genetics and feed intake on nitrogen isotopic fractionation (ΔN) and feed conversion efficiency (FCE; live weight gain/DMI), using a 2 × 2 factorial design, with 2 levels of genetic merit for growth (high vs. low) and 2 levels of feed intake (110 vs. 170% of ME for maintenance [MEm]). No effect of genetic merit was detected for live weight gain ( = 0.64), FCE ( = 0.46), plasma urea nitrogen ( = 0.52), plasma glucose ( = 0.78), and ΔN of wool ( = 0.45), blood ( = 0.09), and plasma ( = 0.51). Sheep receiving 170% of MEm had 175% higher live weight gain ( < 0.001) and 77% higher FCE ( < 0.001) than sheep receiving 110% of MEm. There was no difference among treatments at the beginning of the study for either blood or plasma ∆N, but the treatment groups started to diverge in blood and plasma ∆N at 21 and 7 d, respectively. Blood, plasma, and wool samples were enriched in N compared with feed. There was a higher blood, plasma, and wool ∆N for the low feed intake group than the high feed intake group ( < 0.001 in all cases). Across the 4 treatment groups, higher FCE in sheep was associated with lower ∆N for plasma, blood, and wool. Overall, the results are consistent with the potential of ∆N as a rapid, low-cost biomarker of FCE in sheep, despite there being no effects of genetic treatment on FCE and ∆N. PMID:26641195

  15. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 9: Closed-cycle MHD. [energy conversion efficiency of electric power plants using magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Tsu, T. C.

    1976-01-01

    A closed-cycle MHD system for an electric power plant was studied. It consists of 3 interlocking loops, an external heating loop, a closed-cycle cesium seeded argon nonequilibrium ionization MHD loop, and a steam bottomer. A MHD duct maximum temperature of 2366 K (3800 F), a pressure of 0.939 MPa (9.27 atm) and a Mach number of 0.9 are found to give a topping cycle efficiency of 59.3%; however when combined with an integrated gasifier and optimistic steam bottomer the coal to bus bar efficiency drops to 45.5%. A 1978 K (3100 F) cycle has an efficiency of 55.1% and a power plant efficiency of 42.2%. The high cost of the external heating loop components results in a cost of electricity of 21.41 mills/MJ (77.07 mills/kWh) for the high temperature system and 19.0 mills/MJ (68.5 mills/kWh) for the lower temperature system. It is, therefore, thought that this cycle may be more applicable to internally heated systems such as some futuristic high temperature gas cooled reactor.

  16. Achieving high power efficiency and low roll-off OLEDs based on energy transfer from thermally activated delayed excitons to fluorescent dopants.

    PubMed

    Wang, Shipan; Zhang, Yuewei; Chen, Weiping; Wei, Jinbei; Liu, Yu; Wang, Yue

    2015-08-01

    Achieving high power efficiencies at high-brightness levels is still an important issue for organic light-emitting diodes (OLEDs) based on the thermally activated delayed fluorescence (TADF) mechanism. Herein, enhanced electroluminescence efficiencies were achieved in fluorescent OLEDs using a TADF molecule, (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN), as a host and quinacridone derivatives (QA) as fluorescent dopants. PMID:26120606

  17. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 7: Metal vapor Rankine topping-steam bottoming cycles. [energy conversion efficiency in electric power plants

    NASA Technical Reports Server (NTRS)

    Deegan, P. B.

    1976-01-01

    Adding a metal vapor Rankine topper to a steam cycle was studied as a way to increase the mean temperature at which heat is added to the cycle to raise the efficiency of an electric power plant. Potassium and cesium topping fluids were considered. Pressurized fluidized bed or pressurized (with an integrated low-Btu gasifier) boilers were assumed. Included in the cycles was a pressurizing gas turbine with its associated recuperator, and a gas economizer and feedwater heater. One of the ternary systems studied shows plant efficiency of 42.3% with a plant capitalization of $66.7/kW and a cost of electricity of 8.19 mills/MJ (29.5 mills/kWh).

  18. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 10: Liquid-metal MHD systems. [energy conversion efficiency of electric power plants using liquid metal magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Holman, R. R.; Lippert, T. E.

    1976-01-01

    Electric Power Plant costs and efficiencies are presented for two basic liquid-metal cycles corresponding to 922 and 1089 K (1200 and 1500 F) for a commercial applications using direct coal firing. Sixteen plant designs are considered for which major component equipment were sized and costed. The design basis for each major component is discussed. Also described is the overall systems computer model that was developed to analyze the thermodynamics of the various cycle configurations that were considered.

  19. Hands-On, Demonstration, and Videotape Laboratories for Non-Science Majors in a Food Science Course: Achievement, Attitude, and Efficiency

    ERIC Educational Resources Information Center

    Johnson, H. L.; Trout, B. L.; Brekke, C. J.; Luedecke, L. O.

    2004-01-01

    Student achievement, attitude, and instructional efficiency were determined for hands-on and for live and videotape demonstration laboratories for nonscience majors. Each of 3 laboratory sections experienced 3 different teaching methods for one 4-wk unit. No significant difference in achievement was found among the laboratory methods. An attitude…

  20. A Low Input Current and Wide Conversion Ratio Buck Regulator with 75% Efficiency for High-Voltage Triboelectric Nanogenerators

    NASA Astrophysics Data System (ADS)

    Luo, Li-Chuan; Bao, De-Chun; Yu, Wu-Qi; Zhang, Zhao-Hua; Ren, Tian-Ling

    2016-01-01

    It is meaningful to research the Triboelectric Nanogenerators (TENG), which can create electricity anywhere and anytime. There are many researches on the structures and materials of TENG to explain the phenomenon that the maximum voltage is stable and the current is increasing. The output voltage of the TENG is high about 180-400 V, and the output current is small about 39 μA, which the electronic devices directly integration of TENG with Li-ion batteries will result in huge energy loss due to the ultrahigh TENG impedance. A novel interface circuit with the high-voltage buck regulator for TENG is introduced firstly in this paper. The interface circuit can transfer the output signal of the TENG into the signal fit to a lithium ion battery. Through the circuit of the buck regulator, the average output voltage is about 4.0 V and the average output current is about 1.12 mA. Further, the reliability and availability for the lithium ion battery and the circuit are discussed. The interface circuit is simulated using the Cadence software and verified through PCB experiment. The buck regulator can achieve 75% efficiency for the High-Voltage TENG. This will lead to a research hot and industrialization applications.