SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS
A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 10 - MAY 19, 2006
44 ENERGY PRODUCTION AND CONVERSION
Includes specific energy conversion systems, e.g., fuel cells; and solar, geothermal, windpower, and waterwave conversion systems; energy storage; and traditional power generators.
For technologies related to nuclear energy production see 73 Nuclear Physics.
For related information see also 07 Aircraft Propulsion and Power; 20 Spacecraft Propulsion and Power; and 28 Propellants and Fuels.
20060012236 National Renewable Energy Lab., Golden, CO USA
Time-Resolved Photoluminescence and Photovoltaics
Metzger, W. K.; Ahrenkiel, R. K.; Dippo, P.; Geisz, J.; Wanlass, M. W.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860696; NREL/CP-520-37028; No Copyright; Avail.: Department of Energy Information Bridge
The time-resolved photoluminescence (TRPL) technique and its ability to characterize recombination in bulk photovoltaic semiconductor materials are reviewed. Results from a variety of materials and a few recent studies are summarized and compared. NTIS
Photoluminescence; Photovoltaic Cells; Photovoltaic Conversion
20060012239 National Renewable Energy Lab., Golden, CO USA
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Spatially-Resolved Studies of Grain-Boundary Effects in Polycrystalline Solar Cells Using Micro-Photoluminescence and Near-Field Microscopy
Smith, S.; Dhere, R.; Gessert, T.; Stradins, P.; Wang, T.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860698; NREL/CP-590-37037; No Copyright; Avail.: National Technical Information Service (NTIS)
Photoluminescence and photocurrent spectroscopies combined with diffraction-limited and sub-diffraction-limited spatial resolution are achieved via micro-photoluminescence (m-PL) and near-field microscopy (NSOM). These methods are used to examine the photo-response of individual grain boundaries in thin-film, polycrystalline solar cells at room and cryogenic temperatures. A systematic m-PL study of the effect of CdCl2-treatment on recombination in CdTe/CdS solar cell structures of varying thickness directly reveals the grain-boundary and surface passivation action of this important post-growth processing step. We achieve 50nm (l/10) spatial resolution in near-field Optical Beam Induced Current imaging (n-OBIC) of polycrystalline silicon solar cells using NSOM, at varying stages of silicon nitride grain-boundary passivation, and measure lateral variations in photo-response of CdTe/CdS solar cells with subwavelength spatial resolution. NTIS
Cadmium Tellurides; Cryogenics; Grain Boundaries; Microscopy; Near Fields; Photoluminescence; Polycrystals; Solar Cells
20060012775 National Renewable Energy Lab., Golden, CO USA
Characterization of Photovoltaic Concentrators
Kiehl, J.; Emery, K.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860840; NREL/CP-520-37043; No Copyright; Avail.: National Technical Information Service (NTIS)
This paper will describe the resources at the National Renewable Energy Laboratory (NREL) for performing characterization of photovoltaic (PV) materials designed for operation under concentrated light. NREL has the capability to measure devices ranging from very small, unencapsulated research cells to reasonably sized, environmentally protected modules. Data gathering and interpretation are also ongoing areas of revision and improvement. The main goal of the current research is to reduce the measurement uncertainty to the lowest practical value. At present, the state of the art is limited at a plus or minus 5% level in measuring efficiency accurately. NTIS
Concentrators; Photovoltaic Cells; Photovoltaic Conversion; Renewable Energy
20060012776 National Renewable Energy Lab., Golden, CO USA
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Electrochemical Approaches to PV Busbar Application
Pankow, J. W.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860839; NREL/CP-520-37060; No Copyright; Avail.: Department of Energy Information Bridge
Busbars are an integral component of any thin-film photovoltaic module and must be easy and quick to apply by PV manufacturers, as well as provide long-term reliability in deployed modules. Potential reliability issues include loss of adhesion and delamination, chemical instability under current collection conditions (electromigration or corrosion), compatibility of material and application method with subsequent encapsulation steps.
Several new and novel busbar materials and application methods have been explored, including adhering metal busbars with various one- and two-part conductive epoxies or conductive adhesive films, ultrasonic bonding of metal busbar strips, and bonding of busbar strips using low-temperature solders.
The most promising approach to date has been the direct application of metal busbars via various electrochemical techniques, which offers a variety of distinct advantages. NTIS
Electrochemistry; Photovoltaic Conversion
20060012777 National Renewable Energy Lab., Golden, CO USA
Polymer Based Nanocomposites for Solar Energy Conversion
Shaheen, S.; Olson, D.; White, M.; Mitchell, W.; Miedaner, A.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860836; NREL/CP-520-37042; No Copyright; Avail.: Department of Energy Information Bridge
Organic semiconductor-based photovoltaic devices offer the promise of low cost photovoltaic technology that can be manufactured via large-scale, roll-to-roll printing techniques. Existing organic photovoltaic devices are currently limited to solar power conversion efficiencies of 3-5%. This is because of poor overlap between the absorption spectrum of the organic chromophores and the solar spectrum, non-ideal band alignment between the donor and acceptor species, and low charge carrier mobilities. To address these issues, we are investigating the development of dendrimeric organic semiconductors that are readily synthesized with high purity. They also benefit from optoelectronic properties, such as band gap and band positions, which can be easily tuned by substituting different chemical groups into the molecule. Additionally, we are developing nanostructured oxide/conjugated polymer composite photovoltaics. These composites take advantage of the high electron mobilities attainable in oxide semiconductors and can be fabricated using low-temperature solution-based growth techniques. Here, we discuss the synthesis and preliminary device results of these novel materials and composites. NTIS
Nanocomposites; Solar Energy Conversion
20060012778 National Renewable Energy Lab., Golden, CO USA
Dye-and Semiconductor--Sensitized Nanoparticle Solar Cell Research at NREL
Frank, A. J.; Kopidakis, N.; Benkstein, K. D.; van de Lagemaat, J.; Neale, N. R.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860838; NREL/CP-590-37054; No Copyright; Avail.: Department of Energy Information Bridge
The major objective of this research program is to determine the operational characteristics key to efficient, low-cost, stable liquid-junction and solid-state solar cells based on sensitized nanoporous films (in collaboration with DOE's office of Science Program). Toward this end, we are conducting experimental and theoretical studies to understand the unique physical and chemical factors governing cell performance. Current scientific issues addressed include the influence of film morphology, sensitizer, and electrolyte on the electron transport and recombination dynamics and on the light-harvesting, charge-injection, and charge-collection efficiencies. Recently, we investigated the relationship between (1) transport and recombination, (2) morphological factors of core-shell nanoparticle films and their PV properties, and (3) electron-electron interactions and their effect on the transport dynamics. In this paper, we discuss the connection between transport and recombination and its effect on cell performance. NTIS
Dyes; Evaluation; Nanoparticles; Performance Tests; Semiconductors (Materials); Solar Cells
20060012779 National Renewable Energy Lab., Golden, CO USA
Effect of Electron-Electron Interaction on Transport in Dye-Sensitized Nanocrystalline TiO2
van de Lagemaat, J.; Kopidakis, M.; Neale, N. R.; Frank, A. J.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860837; NREL/CP-590-37053; No Copyright; Avail.: Department of Energy Information Bridge
Experimental measurements and continuous-time random walk simulations on sensitized electrolyte-infused porous nanocrystalline TiO(sub 2) films show that the actual electronic charge in the films is significantly larger than that estimated from small-perturbation methods by a constant, light-intensity- independent factor. This observation can be explained by small-perturbation techniques measuring the chemical diffusion coefficient of electrons instead of the normally assumed tracer diffusion coefficient of electrons. The difference between the two diffusion coefficients is attributed to the presence of an exponential density of states through which electrons interact. At high light intensities, an additional extra component owing to Coulomb interactions between the electrons is expected to arise. NTIS
Dioxides; Dyes; Electrons; Elementary Particle Interactions; Solar Cells; Titanium; Titanium Oxides; Nanocrystals
20060012780 National Renewable Energy Lab., Golden, CO USA
Durability of Polymeric Glazing and Absorber Materials
Jorgensen, G.; Terwilliger, K.; Bingham, C.; Milbourne, M.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860835; NREL/CP-520-37041; No Copyright; Avail.: Department of Energy Information Bridge
The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. The objective of this task is to quantify lifetimes through measurement of the optical and mechanical stability of candidate polymeric glazing and absorber materials. Polycarbonate sheet glazings, as proposed by two industry partners, have been tested for resistance to UV radiation with three complementary methods. Incorporation of a specific 2-mil thick UV-absorbing screening layer results in glazing lifetimes of at least 15 years; improved screens promise even longer lifetimes. Proposed absorber materials were tested for creep and embrittlement under high temperature, and appear adequate for planned ICS absorbers. NTIS
Durability; Solar Heating; Water Heating
20060012781 National Renewable Energy Lab., Golden, CO USA
Real-Time Spectroscopic Ellipsometry as an In-Situ Diagnostic for Hot-Wire CVD Growth of Amorphous and Epitaxial Si
Levi, D.; Teplin, C.; Iwaniczko, E.; Wang, T.; Yan, Y.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860834; NREL/CP-520-37047; No Copyright; Avail.: National Technical Information Service (NTIS)
Real-time spectroscopic ellipsometry (RTSE) has proven to be an exceptionally valuable tool in the optimization of hot wire CVD (HWCVD) growth of both silicon heterojunction (SHJ) solar cells and thin epitaxial layers of crystal silicon (epi-Si). For SHJ solar cells, RTSE provides real-time thickness information and rapid feedback on the degree of crystallinity of the thin intrinsic layers used to passivate the crystal silicon (c-Si) wafers. For epi-Si growth, RTSE provides real-time feedback on the crystallinity and breakdown of the epitaxial growth process. Transmission electron microscopy (TEM) has been used to verify the RTSE analysis of thickness and crystallinity. In contrast to TEM, RTSE provides feedback in real time or same-day, while TEM normally requires weeks. This rapid feedback has been a key factor in the rapid progress of both the SHJ and epi-Si projects. NTIS
Amorphous Silicon; Ellipsometry; Epitaxy; Real Time Operation; Spectroscopy; Vapor Deposition
20060012782 National Renewable Energy Lab., Golden, CO USA
FTR Laboratory in Support of the PV Program
Keyes, B. M.; Gedvilas, L. M.; Bhattacharya, R.; Xu, Y.; Li, X.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860833; NREL/CP-520-37046; No Copyright; Avail.: Department of Energy Information Bridge
The Fourier Transform Infrared Spectroscopy (FTIR) Laboratory supports the Solar Energy Technologies Program through the measurement and characterization of solar energy-related materials and devices. The FTIR technique is a fast, accurate, and reliable method for studying molecular structure and composition. This ability to identify atomic species and their bonding environment is a powerful combination that finds use in many research and development efforts. A brief overview of the technical approach used is contained in Section 2 of this report. Because of its versatility and accessibility, the FTIR Laboratory is a valuable contributor to the Solar Energy Technologies Program. The laboratory provides support for, and collaborates with, several in-house programs as well as our industry and university partners. By the end of FY 2004, the FTIR Laboratory performed over 1100 measurements on PV-related materials. These contributions resulted in conference and workshop presentations and several peer-reviewed publications. A brief summary of a few of these efforts is contained in Section 3 of this report. NTIS
Fourier Transformation; Infrared Spectra; Infrared Spectroscopy; Solar Energy
20060012975 National Renewable Energy Lab., Golden, CO USA
Role of Technology Adoption within the Department of Energy's Solar Energy Technologies Program
Hanley, C.; Thornton, J.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860941; NREL/CP-520-37324; No Copyright; Avail.: Department of Energy Information Bridge
Several technical activities are undertaken on behalf of DOE's Solar Energy Technologies Program in the interests of increasing the broader adoption of solar technologies in the marketplace. Included in these activities are technical support to the development of electrical codes and standards; installer and hardware certification programs; domestic and international technical support activities with leveraged partners; developing new systems configurations, such as building-integrated systems; and studies on environmental, safety, and health-related aspects of production. These technology adoption (TA) activities provide a valuable link between the systems-driven approach (SDA), and both fundamental and applied R&D within the program. Through TA support, the Solar Energy Technologies Program is able to identify market-based needs through data gathering and analysis and to communicate these needs to program researchers. In addition, TA activities maintain the role of the DOE and the laboratories as impartial brokers of information as the markets for these products continue to grow. NTIS
Energy Technology; Solar Energy
20060012978 National Renewable Energy Lab., Golden, CO USA
Low-Cost Solar Domestic Hot Water Systems for Mild Climates
Burch, J.; Christensen, C.; Merrigan, T.; Hewett, R.; Jorgensen, G.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860939; NREL/CP-550-37106; No Copyright; Avail.: Department of Energy Information Bridge
In FY99, Solar Heating and Lighting set the goal to reduce the life-cycle cost of saved-energy for solar domestic hot water (SDHW) systems in mild climates by 50%, primarily through use of polymer technology. Two industry teams (Davis Energy Group/SunEarth (DEG/SE) and FAFCO) have been developing un-pressurized integral-collector-storage (ICS) systems having load-side heat exchangers, and began field-testing in FY04. DEG/SE's ICS has a rotomolded tank and thermoformed glazing. Based upon manufacturing issues, costs, and poor performance, the FAFCO team changed direction in late FY04 from an un-pressurized ICS to a direct thermosiphon design based upon use of pool collectors. Support for the teams is being provided for materials testing, modeling, and system testing. New ICS system models have been produced to model the new systems. A new ICS rating procedure for the ICS systems is undergoing testing and validation. Pipe freezing, freeze protection valves, and overheating have been tested and analyzed. NTIS
Climate; Cost Reduction; Low Cost; Solar Energy; Water; Water Heating
20060012980 National Renewable Energy Lab., Golden, CO USA
Cold-Climate Solar Domestic Hot Water Systems: Cost/Benefit Analysis and Opportunities for Improvement
Burch, J.; Hillman, T.; Salasovich, J.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860938; NREL/CP-550-37105; No Copyright; Avail.: National Technical Information Service (NTIS)
To determine potential for reduction in the cost of saved energy (COSE) for cold-climate solar domestic hot water (SDHW) systems, COSE was computed for three types of cold climate water heating systems. For each system, a series of cost-saving measures was considered: (1) balance of systems (BOS): tank, heat exchanger, and piping-valving measures; and (2) four alternative lower-cost collectors. Given all beneficial BOS measures in place, \g50% reduction of COSE was achievable only with selective polymer collectors at half today's selective collector cost. In all three system types, today's metal-glass selective collector achieved the same COSE as the hypothesized non-selective polymer collector. NTIS
Climate; Cost Analysis; Cost Effectiveness; Water; Water Heating
20060012981 National Renewable Energy Lab., Golden, CO USA
Parabolic Trough Optical Characterization at the National Renewable Energy Laboratory
Wendelin, T. J.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860937; NREL/CP-550-37101; No Copyright; Avail.: Department of Energy Information Bridge
Solar parabolic trough power plant projects are soon to be implemented in the USA and internationally. In addition to these new projects, parabolic trough power plants totaling approximately 350 MW already exist within the USA and have operated for close to 20 years. As such, the status of the technology exists within several different phases. Theses phases include R&D, manufacturing and installation, and operations and maintenance. One aspect of successful deployment of this technology is achieving and maintaining optical performance. Different optical tools are needed to assist in improving initial designs, provide quality control during manufacture and assembly, and help maintain performance during operation. This paper discusses several such tools developed at SunLab (a joint project of the National Renewable Laboratory and Sandia National Laboratories) for these purposes. Preliminary testing results are presented. Finally, plans for further tool development are discussed. NTIS
Characterization; Parabolic Reflectors; Renewable Energy; Solar Energy
20060012982 National Renewable Energy Lab., Golden, CO USA, Sandia National Labs., Albuquerque, NM USA
Planning Strategic Communications and Outreach for the Solar Program
Pedigo, S.; Nahan, R.; Moon, S.; Gwinner, D.; Brooks, C.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860936; NREL/CP-520-37094; No Copyright; Avail.: Department of Energy Information Bridge
Advances made through the Solar Program in photovoltaic and solar thermal technologies must be well communicated to appropriate audiences if further technical and market growth will occur. As the Program's communications team, we developed a plan to: (1) integrate communications across the various solar technologies and reduce redundancy; (2) target audiences and messages strategically; (3) respond better to changes in markets, technology perceptions, audiences, and funding; (4) develop communication projects within the context of other relevant plans (e.g., Solar Program Multi-Year Technical Plan); (5) leverage limited resources; and (6) cultivate a multiyear mentality. Our approach included profiling eight key audiences, including their perceptions of solar technologies; formulating audience-specific messages and communication objectives and strategies; and proposing communications tactics to reinforce the objectives. Presently, we are conducting a needs assessment of print products, as well as a gap analysis. We will then prioritize projects, complete high-priority projects, measure effectiveness of selected projects and the plan, and seek strategic connections with other activities and programs. NTIS
Energy Technology; Solar Energy
20060012984 National Renewable Energy Lab., Golden, CO USA
Exploratory Research for New Solar Electric Technologies
McConnell, R.; Matson, R.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860934; NREL/CP-520-37090; No Copyright; Avail.: Department of Energy Information Bridge
We will review highlights of exploratory research for new PV technologies funded by the DOE Solar Energy Technologies Program through NREL and its Photovoltaic Exploratory Research Project. The goal for this effort is highlighted in the beginning of the Solar Program Multi- Year Technical Plan by Secretary of Energy Spencer Abraham's challenge to 'leapfrog the status quo' by pursuing research having the potential to create breakthroughs. The ultimate goal is to create solar electric technologies for achieving electricity costs below 5 cents/kWh. Exploratory research includes work on advanced photovoltaic technologies (organic and ultra-high efficiency solar cells for solar concentrators) as well as innovative approaches to emerging and mature technologies (e.g., crystalline silicon). NTIS
Electricity; Experimentation; Solar Energy
20060012987 National Renewable Energy Lab., Golden, CO USA
Performance and Cost Model for Solar Energy Technologies in Support of the Systems-Driven Approach
Mehos, M.; Mooney, D.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860933; NREL/CP-550-37085; No Copyright; Avail.: National Technical Information Service (NTIS)
A comprehensive solar technology systems analysis model is being developed to support the implementation of the systems driven approach to program planning for the U.S. Department of Energy's Solar Energy Technologies Program (SETP). Use of this systems model, together with technology and cost benchmarking, market penetration analysis, and other relevant considerations, will support the development of program priorities and direction, and the subsequent investment needed to support R&D activities. NTIS
Cost Analysis; Energy Technology; Mathematical Models; Performance Prediction; Solar Energy; Systems Analysis
20060012991 National Renewable Energy Lab., Golden, CO USA, Colorado School of Mines, Golden, CO USA
Application of Combinatorial Tools for Solar Cell Improvement -- New High Performance Transparent Conducting Oxides
Perkins, J.; van Hest, M.; Teplin, C.; Alleman, J.; Dabney, M.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860931; NREL/CP-520-37081; No Copyright; Avail.: National Technical Information Service (NTIS)
Transparent conducting oxides (TCOs) can serve a variety of important functions in thin film photovoltaics such as transparent electrical contacts, antireflection coatings and chemical barriers. Two areas of particular interest are TCOs that can be deposited at low temperatures and TCOs with high carrier mobilities. We have employed combinatorial high-throughput approaches to investigate both these areas. Conductivities of =2500 (sup -1)-cm(sup -1) have been obtained for In-Zn-O (IZO) films deposited at 100 deg C \g 5000 (sup -1)-cm(sup -1) for In-Ti-O (ITiO) and In-Mo-O (IMO) films deposited at 550 deg C. The highest mobility obtained was 83 cm2/V-sec for ITiO deposited at 550 deg C. NTIS
Combinatorial Analysis; Oxides; Solar Cells; Transparence
20060013004 National Renewable Energy Lab., Golden, CO USA
a-SiGe:H Deposited by Hot-Wire CVD Using a Tantalum Filament Operated at Low Temperature
Mahan, A. H.; Xu, Y.; Gedvilas, L. M.; January 2005; 10 pp.; In English Report No.(s): DE2006-860925; NREL/CP-520-37525; No Copyright; Avail.: National Technical Information Service (NTIS)
We report the deposition of optimum-quality a- SiGe:H and a-Si:H by the hot-wire chemical vapor deposition (HWCVD) technique using a tantalum filament operating at a low temperature. We gauge the material quality of the a-SiGe:H films by comparing infrared, small-angle x-ray scattering, photocapacitance, and conductivity results to those presented elsewhere. NTIS
Low Temperature; Solar Cells; Tantalum; Vapor Deposition
20060013005 National Renewable Energy Lab., Golden, CO USA
High Efficiency Solar Cell Concepts: Physics, Materials, and Devices
Mascarenhas, A.; Francoeur, S.; Seong, M. J.; Fluegel, B.; Zhang, Y.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860924; NREL/CP-590-37079; No Copyright; Avail.: National Technical Information Service (NTIS)
Over the past three decades, significant progress has been made in the area of high-efficiency multijunction solar cells, with the effort primarily directed at current-matched solar cells in tandem. The key materials issues here have been obtaining semiconductors with the required bandgaps for sequential absorption of light in the solar spectrum and that are lattice matched to readily available substrates. The GaInP/GaAs/Ge cell is a striking example of success achieved in this area. Recently, several new approaches for high-efficiency solar cell design have emerged, that involve novel methods for tailoring alloy bandgaps, as well as alternate technologies for hetero-epitaxy of III-V's on Si. The advantages and difficulties expected to be encountered with each approach will be discussed, addressing both the materials issues and device physics whilst contrasting them with other fourth-generation solar cell concepts. NTIS
Solar Cells; Design
20060013006 National Renewable Energy Lab., Golden, CO USA
Reflectance Spectroscopy: Rapid Quantitative Measurements in Commercial Production of Si Solar Cells
Sopori, B.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860844; NREL/CP-520-37061; No Copyright; Avail.: National Technical Information Service (NTIS)
The reflectance spectrum of a wafer/solar cell is used to measure physical parameters of the wafer and its structural components and interfaces. New applications of the reflectometer have been developed, which enable determination of the average parameters over the entire wafer/cell, as well as their spatial mapping. Measurements can be made in less than 100 ms. This method is well suited for commercial monitoring of solar cell processing. NTIS
Reflectance; Solar Cells; Spectroscopy; Reflectometers
20060013007 National Renewable Energy Lab., Golden, CO USA
Photovoltaics R&D: At the Tipping Point
Kazmerski, L. L.; Jan. 2005; 14 pp.; In English Report No.(s): DE2006-860923; NREL/CP-520-37553; No Copyright; Avail.: National Technical Information Service (NTIS)
The realigned U.S. Photovoltaic Industry Roadmap highlights R&D as critical to the tipping point that will make solar photovoltaics (PV) significant in the U.S. energy portfolio- part of a well-designed plan that would bring '2034 expectations' to reality by 2020. Technology improvement and introduction depend on key, focused, and pertinent research contributions that range from the most fundamental through the applied. In this paper, we underscore the successes and relevance of our current systems-driven PV R&D programs, which are built on integrated capabilities. These capabilities span atomic-level characterization, nanotechnology, new materials design, interface and device engineering, theoretical guidance and modeling, processing, measurements and analysis, and process integration. This presentation identifies and provides examples of critical research tipping points needed to foster now and near technologies (primarily crystalline silicon and thin films) and to introduce coming generations of solar PV that provide options to push us to the next performance levels (devices with ultra-high efficiencies and with ultra-low cost). The serious importance of science and creativity to U.S. PV technology ownership- and the increased focus to accelerate the time from laboratory discovery to industry adoption-are emphasized at this 'tipping point' for solar PV. NTIS
Photovoltaic Conversion; Solar Energy; Research and Development
20060013008 National Renewable Energy Lab., Golden, CO USA
First Demonstration of Surface Passivation in Dye-Sensitized TiO2 Solar Cells by an Additive in the Electrolyte
Kopidakis, N.; Neale, N. R.; van de Lagemaat, J.; Frank, A. J.; January 2005; 10 pp.; In English Report No.(s): DE2006-860842; NREL/CP-590-37055; No Copyright; Avail.: National Technical Information Service (NTIS)
The composition of the electrolyte is known to greatly influence the performance of dye-sensitized solar cells. It has been speculated that some components of the electrolyte passivate the TiO(sub 2) surface against recombination; however, this has never been confirmed experimentally. We hereby present the first case of passivation of the TiO(sub 2) surface against recombination by an additive in the electrolyte. Even though the additive also causes a downward movement of the TiO(sub2) bands, suppression of recombination prevails and an overall improvement in open-circuit photovoltage is observed. This work was conducted in collaboration with the DOE Office of Science program. NTIS
Additives; Dioxides; Dyes; Electrolytes; Passivity; Solar Cells; Titanium; Titanium Oxides
20060013009 National Renewable Energy Lab., Golden, CO USA
Tailoring the Interface to Improve Voc in Dye-Sensitized Solar Cells
Kopidakis, N.; Neale, N. R.; van de Lagemaat, J.; Frank, A. J.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860843; NREL/CP-590-37056; No Copyright; Avail.: Department of Energy Information Bridge
Adding certain adsorbents in conjunction with the sensitizing dye employed in high-efficiency TiO2 nanoparticle solar cells has been shown to increase the photovoltage. It is has been speculated that the increased photovoltage is due to these hydrophobic adsorbents passivating surface states that mitigate the recombination of photo-injected electrons with redox species in the electrolyte. In collaboration with the DOE Office of Science Program, we are conducting transient-photovoltage measurements to determine the mechanism for the improved photovoltage. NTIS
Adsorbents; Dyes; Solar Cells
20060013010 National Renewable Energy Lab., Golden, CO USA
Solar Technology and Policy Analysis to Support the Systems-Driven Approach
Margolis, R. M.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860832; NREL/CP-620-37052; No Copyright; Avail.: Department of Energy Information Bridge
The primary focus of the Systems-Driven Approach (SDA) analysis team is to improve the analytical basis for understanding the system and policy drivers of solar technologies in various markets. Analysis activities during the past year have focused in three inter-related areas: (1) developing long-term market penetration projections for the full set of technologies funded within the Solar Energy Technologies Program, (2) reviewing the Program's out-year cost and performance targets for photovoltaic (PV) technology, and (3) evaluating policies, as well as other factors, that impact the value of solar energy technologies in various markets. This paper will summarize the results of these activities and describe how they relate to the overall SDA effort. NTIS
Policies; Solar Energy; Support Systems; Technologies
20060013033 National Renewable Energy Lab., Golden, CO USA
Siting Utility-Scale Concentrating Solar Power Projects
Mehos, M.; Owens, B.; January 2005; 10 pp.; In English Report No.(s): DE2006-860929; NREL/CP-550-37086; No Copyright; Avail.: National Technical Information Service (NTIS)
In 2002, Congress asked the U.S. Department of Energy to 'develop and scope out an initiative to fulfill the goal of having 1,000 megawatts (MW) of new parabolic trough, power tower, and dish engine solar capacity supplying the southwestern USA'. In this paper, we present a review of the solar resource for Arizona, California, Nevada, and New Mexico. These four states have the greatest number of 'premium' solar sites in the country and each has a renewable portfolio standard (RPS). We present information on the generation potential of the solar resources in these states. We also present regions within New Mexico that may be ideally suited for developing large-scale concentrating solar power (CSP) plants because of their proximity to load and their access to unconstrained transmission. NTIS
Site Selection; Solar Energy; Solar Energy Conversion; Electric Power Plants
20060013035 National Renewable Energy Lab., Golden, CO USA
Solid State Theory of Photovoltaic Materials: Nanoscale Grain Boundaries and Doping CIGS
Zunger, A.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860927; NREL/CP-590-37162; No Copyright; Avail.: Department of Energy Information Bridge
We use modern first-principles electronic structure theory to investigate (1) why are grain boundaries in chalcopyrites passive; (2) can chalcopyrites be doped by transition metals, and; (3) can hot electrons and carrier multiplication be efficient in quantum-dot solar cells. NTIS
Additives; Electronic Structure; Grain Boundaries; Photovoltaic Conversion; Solid State
20060013053 National Renewable Energy Lab., Golden, CO USA
DOE/NREL Minority University Research Associates Program
Eddy, F. P.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860926; NREL/CP-520-37082; No Copyright; Avail.: Department of Energy Information Bridge
The DOE-NREL Minority University Research Associates Program (MURA) encourages minority students to pursue careers in science and technology. In this program, undergraduate students work with principal investigators at their universities to perform research projects on solar technology. Then, students are awarded summer internships in industry or at national laboratories, such as NREL, during the summer. Because of its success, the program has been expanded to include additional minority-serving colleges and universities and all solar energy technologies. NTIS
Education; Minorities; Solar Energy; Students; Energy Technology
20060013063 National Renewable Energy Lab., Golden, CO USA
Design of a Net-Metering and PV Exhibit for the 2005 Solar Decathlon
Wassmer, M.; Warner, C.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860828; NREL-CP-520-37029; No Copyright; Avail.: Department of Energy Information Bridge
In the 2005 Solar Decathlon competition, 19 collegiate teams will design, build, and operate grid-independent homes powered by photovoltaic (PV) arrays on the National Mall. The prominence of grid-interconnected systems in the arketplace has provided the impetus for the development of a net-metering exhibit to be installed and operated during the competition. The exhibit will inform the visiting public about PV basics and appropriate alternatives to grid-independent systems. It will consist of four interactive components. One will be designed to educate people about the principles of net metering using a small PV array, a grid-interactive inverter, and a variable load. Additional components of the exhibit will demonstrate the effects of orientation, cloud cover, and nighttime on performance. The nighttime component will discuss appropriate storage options for different applications. NTIS
Solar Energy; Photovoltaic Cells; Inverters; Solar Arrays
20060013064 National Renewable Energy Lab., Golden, CO USA
Parabolic Trough Organic Rankine Cycle Solar Power Plant
Canada, S.; Cohen, G.; Cable, R.; Brosseau, D.; Price, H.; Jan. 2005; 10 pp.; In English Report No.(s): DE2006-860827; NREL/CP-550-37077; No Copyright; Avail.: Department of Energy Information Bridge
Arizona Public Service (APS) is required to generate a portion of its electricity from solar resources in order to satisfy its obligation under the Arizona Environmental Portfolio Standard (EPS). In recent years, APS has installed and operates over 4.5 MWe of fixed, tracking, and concentrating photovoltaic systems to help meet the solar portion of this obligation and to develop an understanding of which solar technologies provide the best cost and performance to meet utility needs. During FY04, APS began construction of a 1-MWe parabolic trough concentrating solar power plant. This plant represents the first parabolic trough plant to begin construction since 1991. The plant will also be the first commercial deployment of the Solargenix parabolic trough collector technology developed under contract to the National Renewable Energy Laboratory (NREL). The plant will use an organic Rankine cycle (ORC) power plant, provided by Ormat. The ORC power plant is much simpler than a conventional steam Rankine cycle power plant and allows unattended operation of the facility. NTIS
Electric Power Plants; Parabolic Reflectors; Rankine Cycle; Solar Collectors; Solar Energy Conversion
Source: NASA
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