General Framework

The SETP has created a management structure that blends program administration with scientific oversight. Program administration is done by a relatively small DOE staff that focuses on implementing Administration policy. Two DOE national laboratories -- the National Renewable Energy Laboratory and Sandia National Laboratories -- provide scientific oversight of the solar R&D tasks being performed by universities, industry, and national laboratories. Laboratory management of the tasks enables detailed technical evaluations to become a part of each programmatic decision made by DOE.

The bulk of the SETP Photovoltaic Subprogram's activities are carried out through two primary research centers: the National Renewable Energy Laboratory (NREL) in Golden, CO, and Sandia National Laboratories (SNL), in Albuquerque, NM. Brookhaven National Laboratory (BNL), in Upton, provides program support in the area of environmental health and safety. NREL, SNL, and BNL are all partners in the National Center for Photovoltaics (NCPV), which provides guidance to DOE PV research efforts. In addition, DOE's Golden Field Office (GO), in Golden, CO, and the Albuquerque Operations Office (ALO), in Albuquerque, NM, administer and manage contracting activities assigned by headquarters.

The photovoltaic Subprogram's research is focused on increasing domestic capacity by lowering the cost of delivered electricity and improving the efficiency of modules and systems. The program emphasizes long-term innovative research, thin-film development, manufacturing R&D, and systems development and reliability.

Long-term research is focused on “leapfrog” technologies such as polymers and nanostructures. In thin films, new levels of efficiency and stability in prototype modules have been achieved, as well as higher laboratory cell efficiencies. Near-term research is focused on reducing cost through manufacturing advancements and improving system reliability.

In 2005, photovoltaics (PV) generated excitement in the United States, with PV systems being installed at an unprecedented scale. Public support for PV appears to be increasing as well, as evidenced by public support of PV incentives mentioned later in this report.
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National Programme

To accomplish its goals, the SETP combines research, design, and development of technology with value analysis, an integrated-systems approach, and partnering. Central to this strategy is the “Systems-Driven Approach,” which emphasizes the importance of how materials, processes, components, products, applications, and markets for a technology are related to each other.
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Research, Development and Demonstration

• Fundamental Research
  Fundamental Research investigates the physical mechanisms of charge carrier transport, band structure, junction formation, impurity diffusion, defect states, and other physical properties of PV materials and devices. Among the research topics are innovative ideas and technologies with the potential to “leapfrog” current approaches, leading to new, non-conventional concepts that could dramatically improve cost effectiveness in the long term. The following are:
  • Fundamental Research topics and sample 2005 accomplishments. Measurements and Characterization -- Provides test, measurement, and analysis support and research for the SETP, including national laboratories, external research partners in university and industry laboratories, and PV manufacturers.
    • Expanded ISO 17025 accreditation from secondary reference cells to include primary reference cells and modules and developed a prototype minority-carrier lifetime measurement system capable of accurately measuring both crystalline and multi-crystalline silicon wafers in an in-line manufacturing environment.
  • Electronic Materials and Devices -- Carries out research in semiconductor materials, device properties, and fabrication processes to improve the efficiency, stability, and cost of PV.
    • Invented fire-through agents that enable inkjet-written Ag contacts to silicon solar cells through silicon nitride antireflection coating.
  • Crystalline Silicon Project -- Directs fundamental crystalline silicon R&D involving universities and national laboratories.
    • Demonstrated a 17 %-efficient heterojunction silicon (a-Si/c-Si) solar cell and demonstrated a bifacial heterojunction silicon solar cell process for p-type c-Si wafers that resulted in 12,5 %-efficient cells. This work is being used to evaluate deposition temperature and crystal orientation of the substrate.
  • High-Performance Photovoltaics -- Explores the ultimate performance of PV technologies, aiming to approximately double their sunlight-to-electricity conversion efficiencies.
    • Demonstrated a 39 %-efficient GaInP/GaInAs/Ge cell verified by NREL at 236 suns. This is the highest NREL-confirmed efficiency ever measured for any PV device. This record used three-junction GaInP/GaInAs/Ge concentrator solar cells grown on a Ge substrate incorporating epitaxial device features to optimize their performance under the concentrated terrestrial spectrum and processed at Boeing Spectrolab, under an NREL subcontract.
  • Solar Resource Characterization -- Addresses solar resource assessment including access to data and characterization of the solar resource.
    • Evaluated performance of three candidate solar radiation models for the National Solar Radiation Data Base and to implement the IEA “Solar Resource Knowledge Management” Task for benchmarking international solar resource data sets. This project addresses solar resource assessment and includes access to data and characterization of the solar resource for the needs of designers, modelers, and resource assessment interests, both in the United States and internationally.
  • Environmental Health and Safety -- Minimizes potential EH&S impacts associated with current and future PV energy systems and applications.
    • Advanced CdTe recycling by accomplishing a 99,99 % separation of Cd from Te at a projected cost of 0,02 USD per watt. Ongoing outreach and information dissemination efforts were also conducted because the PV industry is undergoing changes in type and quantities of materials, manufacturing processes, and scale.

• Advanced Materials and Devices
  The Advanced Materials and Devices effort carries out research in semiconductor material properties, device mechanisms, and fabrication processes to improve the efficiency, stability, and cost of PV. The effort focuses on thin films, module manufacturing methods, and module reliability. The following are Advanced Materials and Devices research areas and sample 2005 accomplishments:
  • Thin Film PV Partnership -- Directs subcontracted and collaborative R&D in thin films including CIS, CdTe, amorphous silicon, CIGS, and film silicon.
    • Two Technology Partners broke ground on major manufacturing expansions (First Solar 25 MW to 75 MWp CdTe, and Uni-Solar 25 MW to 50 MWp a-Si). The Thin Film PV Partnership supported the transition to successful first-time manufacturing of key thin-film technologies during the fiscal year. This is the Partnership's most important activity in the short term, because it will help establish thin films in the marketplace, improve their chances of future growth and success, and help define the transition of technologies that have been successfully developed by DOE funding to the private sector.
  • PV Manufacturing R&D -- Assists the U.S. PV industry through cost-shared manufacturing R&D.
    • Continued with “Large-Scale Module and Component Yield, Durability, and Reliability” subcontracted efforts with the selection of 11 industry partners. This solicitation focuses on: the improvement of module manufacturing processes to increase module reliability, system and system component packaging, system integration, manufacturing and assembly; product manufacturing flexibility; and balance-of-system (BOS) development including storage and quality control.
  • PV Module Reliability R&D -- Develops and applies advanced measurement techniques, diagnostic methods, and instrumentation to help mitigate degradation, reduce module costs, and improve performance. To conduct these activities, NREL and SNL develop and apply advanced measurement techniques, diagnostic methods, and instrumentation. The intent of this R&D is to optimize the time and funding applied to advancing module technologies from the prototype to the commercial production stage, with respect to meeting acceptable performance, reliability, and costing requirements.
    • Initiated unique high-voltage stress testing experiment that measures module leakage currents to ground on a bipolar array of Shell Solar's CIGSS modules. Also, a cooperative testing program was initiated on SunPower's high-efficiency crystalline-Si modules including light soaking, thermal cycling, and damp heat exposure indoors, and real-time outdoor exposure geared toward helping SunPower improve fabrication of its solar cells.
  • Inverter and BOS Development -- Supports engineering advancements through characterization feedback of newly developed power electronics and BOS hardware and establishes suitability for incorporation of new inverters and BOS into integrated systems.
    • Assessed alpha inverter and controller prototypes for conformity to utility interconnection requirements, performance objectives, and manufacturing objectives. Additionally, the “High-reliability Inverter Initiative” took a first step toward higher reliability at no increase in unit cost, namely the improvement of mean-time-between- failures to more than 10 years. This advance had a significant positive impact on calculated levelized cost of energy of PV systems.

• Technology Development
  The Technology Development activity advances PV performance and systems engineering, improves systems reliability, and develops technology suitable for integration into residential and commercial building structures. The following are Technology Development research areas and sample 2005 accomplishments:
  • PV Systems Engineering -- Characterizes performance and reliability of emerging PV technologies, assists with development and implementation of codes and standards, and provides world-class solar irradiance capabilities, measurements, and standards.
    • Generated 24 performance reports for PV systems monitored at the NREL Outdoor Test Facility. These reports provide world-class and traceable measurements and instrumentation for solar radiometry. The resultant precision and accuracy of the PV system (and module) performance measurements are determined by the quality, precision, and accuracy of the measurements of the incident (on the PV arrays) solar irradiance (i.e., “power in”). This project also includes very important activities aimed at supporting the development of industry-consensus/ adopted codes, standards, and certification that cover PV systems, components, and installation practices.
  • System Evaluation & Optimization -- Provides laboratory and field-test information to establish the performance and reliability of current PV systems and identifies opportunities for improved system design and component integration in next-generation systems.
    • Implemented the PV System Optimization Laboratory, which can perform detailed performance and long-term reliability research on 14 separate nominally 3-kW PV systems with multiple array/inverter combinations. Working with SNL, both General Electric and Xantrex are currently active in Phase III of the “High-reliability Inverter Initiative” and have extensive and critically timed commercialization plans for the products developed out of this program. Xantrex expects to use the fundamental high-reliability design as a basis for its next-generation family of products. GE is vertically integrating its newly acquired PV module manufacturing capabilities with the new inverter development into its existing new construction housing market.
  • Domestic PV Applications -- Provides a focal point for DOE activities through developing projects, disseminating information, promoting public awareness, managing subcontracts, and providing technical assistance.
    • Supported development of standardized program acceptance criteria for evaluation of U.S. Department of Agriculture (USDA)\Rural Utility Service and the USDA Farm Bill proposals.
  • Building-Integrated PV -- Fosters widespread acceptance of PV-integrated buildings by overcoming technical and commercial barriers and facilitating the integration of PV into the built environment through technology development, applications, and key partnerships.
    • Implemented the 2005 Solar Decathlon university competition involving 18 university design teams to raise awareness of the potential of solar technologies. Student teams from around the globe participated in an unparalleled solar competition to design, build, and operate the most attractive and energy-efficient solar-powered home. More than 120 000 attendees toured the homes on the Washington D.C. Mall, and the official Solar Decathlon Web site, www.solardecathlon.org, received approximately 73 000 unique visits during the event.
  • Million Solar Roofs (MSR) -- Facilitates installation of solar energy systems on U.S. buildings.
    • Added five new MSR State and Local Partnerships, bringing the national total of participants to 926 partnerships.
  • PV System Analysis -- Performs systems performance and cost modelling, market/value/policy analysis, and benchmarking projects.
    • Expanded the number of default markets/systems included in the Solar Advisor Model and expanded partnered activities on commercial and utility-scale systems to further refine determinations of life-cycle cost, system reliability, and system availability. Additionally, a working version of the SolarDS model was developed with an initial set of scenarios and expanded work on PV value analysis to include both identifying best practices and information sharing, aimed at helping to inform state-level policymaking.
  • Regional Experiment Stations -- Provide technical support to the SETP, including reducing systems costs, improving systems reliability, improving system performance, and removing barriers to deployment.
    • Four inverters were placed in service for long-term performance testing at each Regional Experiment Station. Additionally, technical assistance and installer workshops to the industry and users have resulted in an evolving design review and approval standard that provides guidance for uniform designs and system documentation. This activity promotes a level of quality recognized and practiced by other industries that develop products in successful markets.

Implementation

Federal and State Policies Promote PV
The U.S. PV Industry Roadmap states, “Effective policies sustained over time increase solar power production, dramatically grow markets, improve technology, and reduce costs (SEIA, 2003).” In the United States, federal and state policies are in place to promote PV.

The Energy Policy Act of 2005 offers consumers and businesses federal incentives for many renewable energy and energy efficiency technologies. For example, the act established a 30 % tax credit for qualified PV system expenditures up to a maximum of 2 000 USD for equipment placed in service during 2006-2007. The U.S. PV industry is promoting extension of this incentive.

The most notable state PV incentive program is the California Solar Initiative. Enacted in 2005, it is the largest state solar incentive program in the United States. It allots 2,9 billion USD for solar energy rebates in California over 10 years. The goal is to increase the solar capacity installed on California rooftops by 3 000 MW by 2017. The initial PV incentive levels were set at 2,80 USD per watt effective Jan. 1, 2006, to be reduced by an average of approximately 10 % annually. For more information, visit the California Public Utilities Commission site at www.cpuc.ca.gov.

Numerous additional state policies promote PV throughout the United States. For example, more than 20 states have renewable portfolio standards, requiring that a certain proportion of a utility's generating capacity or energy sales be derived from renewable resources. For more information on state incentive programs, see the Database of State Incentives for Renewable Energy at www.dsireusa.org.
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Industry status

A consequence of the rapid growth of PV has been the emergence of a solar-grade silicon supply shortage. This supply shortage, which is believed to be temporary with new supplies coming on line throughout 2006 and 2007, has created an opportunity for thin-film PV and concentrator technologies, which do not use polysilicon feedstock, to accelerate their move from the laboratory into manufacturing and large-scale production.

While PV has been growing rapidly worldwide, the United States has lost its lead in PV development. According to the U.S. PV Industry Roadmap, in 1997, U.S. solar power manufacturers captured nearly 100 % of the domestic market; in 2003, they captured only 73 % (SEIA, 2003). According to PV News, in 1997, U.S. manufacturers captured more than 40 % of the world market; in 2005, they captured only 9 %. In 2005, U.S. production grew by 10 % from the previous year. Meanwhile, shipments from Europe grew by 44 % and shipments from Japan by 38 % from 2004 (Maycock, 2006).
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Market development

The SETP meets these deployment facilitation opportunities in a variety of ways. For example, DOE's Million Solar Roofs Initiative is a public/private technology deployment partnership aimed to overcome barriers to market entry for solar technologies and to facilitate the installation of residential, commercial, and industrial systems. Another example is DOE's Solar Decathlon, which brings college and university teams from around the world to compete in designing and building houses that demonstrate the benefits of solar technologies.

International partnerships also play a role in deployment facilitation because the majority of domestically produced solar products are currently shipped overseas, and international solar markets will continue to grow in the foreseeable future. Therefore, knowledge and information from solar activities outside the United States provide business opportunities to U.S. solar companies in developed markets, such as Japan and Europe, and developing markets, such as India and China. The SETP also supports the International Energy Agency (IEA), specifically through the IEA Photovoltaic Power System Implementing Agreement. Activities include technical assistance, demonstration of the technical feasibility of new technologies and applications, training, development and promotion of norms and standards, and fostering business development, such as facilitation of joint-venture agreements between foreign and U.S. companies.

To facilitate continued market growth, it is important to develop appropriate and reasonable codes, standards, and certification programs. The SETP focuses support on collaborative efforts with standards organizations, including the National Fire Protection Association, the Institute for Electrical and Electronic Engineers, the American Society for Testing Materials, Underwriters Laboratories, and the International Electrotechnical Commission.

Specific opportunities in this arena are improved utility interconnection standards that include communications and controls for grid stabilization, a standardized communications protocol for inverters and system controllers, hardware certifications to improve consumer confidence, and standardized practices for certification of PV system designers and practitioners, assuring up-to-date knowledge on advances in technology, safety, or interconnect practices.
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Future outlook

Industry Targets and Projections
Projections from the U.S. PV Industry Roadmap suggest that, at robust growth rates achievable through proven policies for technology and market development, “the cumulative capacity of installed solar electric systems in the United States will grow from less than 0,4 GW in 2003 to 200 GW by 2030” (SEIA, 2003). In the short term, the annual growth in U.S. solar generation capacity is projected to track growth in worldwide solar power equipment sales, at over 35 %. U.S. exports likely will remain flat. Most U.S. solar power equipment will remain in the United States, and domestic demand will fuel industry growth if the United States invests in technology and market development programs. According to the industry roadmap, “By 2020, the U.S. industry should install nearly all its output -- 7,2 GWp per year -- in the United States. After 2015, growth rates will moderate to 26 % annually until 2020, as technology and markets mature. Annual growth rates will decline to a sustainable 1 % to 2 % annual increase in 2030 -- the classic S-shaped market penetration curve for new technologies. By 2030, the industry is targeting cumulative installed solar capacity of 200 GW, and the industry will install 19 GW per year” (SEIA, 2003). At that point, the industry predicts that solar power will be a substantial share of U.S. peak generating capacity and a major source of electricity. As soon as 2015, the system selling price is projected at 3,68 USD per watt if the policies recommended in the industry roadmap are implemented. With incentives, the cost of solar electricity will be as low as 0,057 USD per kWh -- a level that is lower than current retail rates for many consumers.

In summary, the potential of solar energy in the United States will be realized through concerted R&D efforts via public/private partnerships to reduce the cost of solar energy systems and to maximize solar energy's promise over the next 20 years. Solar energy represents an opportunity to diversify the United States' primary energy requirements and future energy demands while creating jobs in high-tech manufacturing, installation, and operation of solar power equipment.
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Sources

• Maycock, Paul. “PV News.” PV Energy Systems. Vol. 24/No. 3, p. 1. March 2005. www.pvenergy.com.
• Solar Energy Industry Association. Our Solar Power Future: The U.S. Photovoltaics Industry Roadmap. September 2003. www.seia.org.
• U.S. Department of Energy, Solar Energy Technologies Program. Solar Energy Technologies Program FY 2004 Annual Report. DOE/GO-102005-2173. October 2005. www.osti.gov/bridge
• U.S. Department of Energy, Solar Energy Technologies Program. Solar Energy Technologies Program Multi-Year Program Plan 2007-2011. September 2005. www.eere.energy.gov/solar/
• U.S. Department of Energy, Solar Energy Technologies Program. Solar Energy Technologies Program Multi-Year Technical Plan 2003-2007. January 2004. www.eere.energy.gov/solar/

Acknowledgements

Further reading about the USA

• USA - Country information