United States of America, PV technology status and prospects - Contribution to the Annual report 2002

United States of America
PV technology status and prospects
Ward Bower, Sandia National Laboratories, Albuquerque, New Mexico

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General Framework

Fig.1 - Pinnacles National Monument: This 10 kW PV Power System provides power for the ranger station, visitor center well pump and other loads. [Photo Courtesy of NREL]

The U.S. Department of Energy's (DOE) Office of Energy Efficiency and Renewable Energy directed the U.S. PV Program through its Office of Solar Energy Technologies in the U.S. through September 2002.
Beginning in October 2001, the U.S. DOE reorganized its renewable energy work into a new National Solar Program with the Photovoltaic topic being a subprogram. The U.S. DOE was the leading funding source for PV research and development in 2002 and it offered the resources of the national laboratories to assist in the PV industry’s applied research and development (R&D) activities.
The Office of Energy Efficiency and Renewable Energy led the national laboratories to develop comprehensive operating plans based on strategic, multiyear plans that respond to the broad policies for energy R&D determined by the executive and legislative branches of the federal government. The National Center for Photovoltaics (NCPV) worked with the PV industry through various cost-shared programs to develop and improve component designs, device manufacturability and systems. Education, technical transfer, technical assistance and competitive contracts were used extensively to accomplish the work in 2002. PV-related activities funded by the DOE were appropriated to PV cell and module development, manufacturing, balance-of-system and system technologies. The U.S. Department of Energy web site (http://www.eren.doe.gov/pv) provides up-to-date information on and links to all aspects of the PV activities in the U.S.

The "Industry Roadmap," refined in December 2000 unified the vision and long-term (2000-2020) strategies and goals for the PV industry. The vision goals are geared toward the electrical/energy consumer competitive and environmentally friendly energy products and services from a thriving U.S.-based solar electric power industry.
The “DOE PV Program 5-Year Plan (2000-2004)” that was written in concert with the “Industry Roadmap” helps to guide the national PV activities. In addition, the U.S. DOE Million Solar Roofs Initiative promoted the reduction in greenhouse gas and other emissions.
The initiative sponsors State and local partnerships, financial tools, consumer awareness, and support with codes, standards, and certification programs.

The National Center for Photovoltaics (NCPV), an alliance of organizations, continued to serve as the focal point for the nation’s capabilities in PV. The R&D goals and strategies are formulated each year by a governing board in concert with the “Industry Roadmap” and through the NCPV “Annual Operating Plan.”

PV technologies for thin-film devices continued a partnership program in 2002. The Thin-Film Partnership Program collaborated with manufacturers on technology issues that were common to all manufacturing processes and non-proprietary.
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National Programme

The U.S. Department of Energy is the principle source of funding for PV research and development. Research is focused on increasing domestic capacity by lowering the cost of delivered electricity and improving the efficiency of PV modules and systems. Fundamental research at universities helps to develop non-conventional, break-through technologies. Laboratory and university researchers will work with industry on high-volume, low-cost manufacturing, such as increasing deposition rates to grow thin-film layers, improving materials utilization, reducing cost, improving reliability and using in-line monitoring to increase yield and performance. Specific goals by 2006 are to:

Reduce the direct manufacturing cost of PV modules by 30 percent from the current average cost of USD 2,50/W to USD 1,75/W;
Identify and begin prototype development of leap-frog technologies that have the potential for dramatic cost reduction;
Establish greater than 20-year lifetime for PV systems by improving the reliability of balance-of-system components and reduce recurring costs by 40 percent;
Work with the PV industry to facilitate achievement of its roadmap goals of 1 GW cumulative U.S. sales (Export and Domestic) by 2006.

The national PV activities are directed through the U.S. Department of Energy (DOE) with headquarters in Washington, DC, and by research centers at the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories (Sandia). Overreaching goals of the U.S. PV activities are to accelerate the development of PV as a national and global energy option and to ensure technology and global market leadership for the nation. The dissemination of information pertaining to PV technologies is handled through printed reports, web sites, and conferences. The National Solar Program shared the costs in areas of fundamental research, technology development and advanced materials and devices. The authorized funding was categorized into three major areas for FY 2002 for PV.

Fundamental Research 33 % of the budget
Technology Development 41 % of the budget

Advanced Materials and Devices 26 % of the budget

The total FY2002 federal budget for the Photovoltaic component of the National Solar Program totaled USD 66,1 million dollars. Substantial funding for PV-related projects also came through State and local governments, partnerships, PV industry cost sharing, and utilities.

The NCPV relies on the core expertise of NREL and Sandia to create, develop, and deploy PV and related technologies. Other national PV resources that the NCPV draws on are Brookhaven National Laboratory, two Regional Experiment Stations (the Florida Solar Energy Center and the Southwest Technology Development Institute), and U.S. DOE Centers of Excellence at the Georgia Institute of Technology and the University of Delaware (Institute of Energy Conversion). In addition, more than 90 university, industry and utility research partnerships across the country are linked together to function in a unified way. The NCPV awards most of its federal funds through competitive procurements to industry, universities, and other research centers.
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Research, development and demonstration

The national PV effort included fundamental, advanced materials, device, and manufacturing R&D. Critical PV program contributions were provided through national laboratory support to the industry through basic research, device characterization, and environment, safety and health activities. A web-based virtual laboratory allowed collaborators from universities and industry to access real-time data on test results related to their projects.

Research on Thin-film Photovoltaics
Thin-film devices and materials development were a major part of the PV program and were administered through the NCPV and the Thin-film Partnership Program. Thin-film devices include amorphous silicon (a-Si), copper indium diselenide (CIS), copper indium gallium diselenide (CIGS), cadmium telluride (CdTe), thin-film silicon and others. The Thin-film Partnership Program continued awarding contracts for the next round of research. Responding to sustained research efforts, the efficiency of thin-film devices is rising. Six companies marketed thin-film ranging from a few watts to nearly 100 watts.
Research has moved efficiencies of a-Si devices toward the national goal of 13 % efficiency. United Solar Systems increased a-Si production to more than 8 MW in 2002. BP Solar operated its 10 MW/year plant with enhanced throughput that produces tandem-junction until November 2002.
PV devices using CdTe can be manufactured using potentially lowcost techniques such as spraying, electro deposition, and high-rate evaporation. Achieving high laboratory efficiencies using these lowcost techniques is an important objective of the National PV Program. To date, more than ten techniques have been used to grow CdTe. First Solar, LLC has continued to advance its ultrahigh-rate vapor transport deposition through collaboration with the NCPV.
A major goal for CIS research is to transfer years of government-sponsored research to industry for pilot-scale manufacturing and to produce commercial modules. NREL scientists have achieved replicable CIGS cells with efficiencies greater than 21,1% under 14-sun concentration. Industry explored new deposition systems for large-area CIS devices.
Shell Solar and Global Solar sold commercial products using CIS alloys in 2002. Shell Solar produced 5- to 40-W PV modules made of CIS alloys. Global Solar produced flexible modules for a variety of field applications.
Research and Development of the Balance-of-System
Research within the industry and the national laboratories continued to explore improved solid-state switching methodologies for inverters, new control firmware and software, new balance-of- system hardware designs, and entire PV systems that are cost effective. Inverter development included higher reliability, universal/modular inverters and conformance with anti-islanding and code requirements. A market for new grid-tied installations using battery storage remained steady. Sandia maintains a program to evaluate and improve batteries and charge controllers for PV applications. Issues pertaining to environment, safety and health remained an essential aspect of working with the balance-of-system industry and were included in all work sponsored by the National Solar Program.
Research on High Performance and Concentrating PV
The National Solar Program contains a 10 year program goal to double the efficiency of multi-junction thin-film modules. There is also a goal to demonstrate a high-efficiency III-V cell in a pre-commercial concentrator module. To help achieve this objective, the High Performance PV Initiative was continued in 2002. The NCPV and Spectrolab are collaborating toward a goal of a 40 % cell under concentrated sunlight. Workshops and concentrator forums were held during 2002 as work continues on several fronts to develop materials that will perform well at very high concentrations of sunlight.
Plug and Play Research and Development
A new concept called the AC PV Building Block was detailed and patents were applied for. This concept is expected to fill an important market niche for code compliant, retrofit and building-integrated applications.
Demonstration Programs
No major national demonstration programs were active during 2002. Several programs were sponsored by various sectors of state governments and utilities, most notably California. Deregulation of the electric utilities and localized energy shortages have spurred several state programs that require installation of PV energy systems along with new R&D efforts aimed at fielded PV systems.

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Manufacturing and implementation

Fig. 2 - Solar Decathlon: The U.S. Department of Energy organized the Solar Decathlon international competition to challenge student teams to capture, convert, store and use enough solar energy to power today’s modern lifestyle. Fourteen teams competed. [Photo Courtesy of Richard King, US DOE]

Industry Roadmap
Success of the PV component of the National Solar Program depends on the direction, resources, best scientific and technological approaches, use of the best technologies and continued efforts of the best and brightest among industry, federal laboratory and university partners. The NCPV worked in concert with the industry to lay the groundwork for a “Systems Driven Approach” to guide new PV work that meets the goals of the industry roadmap and that will be funded by the U.S. DOE.
Photovoltaic Manufacturing
In 2002, the U.S. PV industry marketed about USD 1,2 billion of the world’s estimated USD 3,2 billion of PV products. To maintain technology leadership and market share, improvements in product must move from laboratories to the world marketplace. Against this backdrop of a growing market, the PV Manufacturing R&D Project continued it support through, “Photovoltaic Manufacturing R&D—In-line Diagnostics and Intelligent Processing in Manufacturing Scale-Up.” This solicitation encourages teams to share the cost of high-risk research to develop intelligent processing for larger scale manufacturing that will be the foundation for achieving the goals set out in the U.S. Photovoltaic Industry Roadmap. Great progress has been made in reducing the cost of PV systems and improving the performance and reliability of commercial products under the manufacturing research and development program. Work under previous subcontracts awarded under PV Manufacturing Technology (PVMaT) solicitations were completed in 2001, just as new contracts were awarded.
Systems
A systems engineering program that included a balance-of-system program was accelerated this year with Sandia leading efforts to fund evolutionary changes to power processing hardware that would result in improved reliability and performance. Improved reliability of inverters and required switchgear was also funded with Phase I of the high reliability inverter initiative begun in 2002. The initiative continues working with industry to improve "Total Quality Management" programs in the manufacturing and assembly areas.
Sandia also urged industry to participate in “Highly Accelerated Life Tests (HALT™)” and “Highly Accelerated Stress Screens (HASS™)” to improve quality and reliability of hardware. The test facilities at Sandia and NREL continue to contribute significantly to all of the reliability-improving programs.
Sandia and NREL conduct module performance and durability studies for manufacturers based on data from several test sites. For new modules or for those that have operated in the field for years, researchers collect data on electrical performance, extent of delamination, integrity of solder joints, and properties of encapsulants. Tests include outdoor electrical performance, dark current/voltage (I-V), infrared (IR) imaging, ultraviolet (UV) inspection, solder-joint metallurgy, and ultrasonic characterization, as well as destructive testing for specific failure modes.
An inverter test facility at Sandia provides for characterization, benchmarking, surge testing and accelerated life testing. A new 30 kW hybrid test bed for inverters, designed for grid-connected or stand-alone PV systems was in operation as the Distributed Energy Test Laboratory (DETL). It includes a complete mini-grid control unit and a 75 kVA micro turbine; a 90 kVA diesel; and load banks that are resistive, inductive, and capacitive in nature. The product of an agreement with the Salt River Project and Sandia, this DETL can be used to study the effects of any distributed generation system (including PV and PV hybrid systems) on electrical utility operation.
NREL maintains the Outdoor Test Facility (OTF) to test performance and reliability of solar cells, modules, and small (1–5 kW) systems. The OTF also calibrates primary reference cells for use in-house, by other national laboratories, by industry, and by universities. Researchers at the OTF measure performance in actual outdoor tests and using solar simulators indoors. Indoors at the OTF, modules are tested for failure and performance in conditions of high voltage, high heat, high humidity, flexing, static loading, and simulated hail strikes.
Outdoors, the test beds at the OTF measure long-term performance and stability. Two test beds perform stress tests of modules under accelerated conditions of high voltage and high sunlight concentration.
Sandia support increased at least five-fold the participation by systems and balance-of-system industry at the 23rd IEEE PV Specialist Conference. For the first time in a decade, the conference topics include six dedicated systems sessions with overflow participation. Topics for the sessions included increasing reliability, improving performance, reducing life-cycle costs, removing barriers, certification of practitioners and hardware, and expanding markets.
Although manufacturers are now offering 10- to 20-year warranties on PV modules, PV systems that operate reliably for 25 years are a major goal of the PV system activities. To reach that goal, the program is supporting research and analysis using field data and models to identify areas for further technical development. Sandia’s “PV System Reliability Plan,” drafted in consultation with industry, is guiding hardware and system development. The plan recommends continuation of several activities such as developing a reliability database to improve understanding of the performance of real systems; examining PV systems and components after extended operation in the field to identify sources of performance degradation or failures that could be prevented by changes in manufacturing; modeling system performance to identify fault-tolerant designs, sensitivity to component failure, and cost-effective component replacement strategies; and working with industry and users to resolve technical or institutional barriers to system reliability.

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Market Development

Fig. 3 - This 1,18 MW photovoltaic installation on the Santa Rita jail is located in Dublin, CA. It reduces peak power consumption by 30 % and produces over 1,4 million kWh per year. [Photo Courtesy of PowerLight Corporation]

The National Solar Program provided continuing support for state-supported PV applications using assistance through the Interstate Renewable Energy Council (IREC). Much of this work continued to provide PV applications and education for parks and public spaces through the “Photovoltaics for Utilities (PV4U)” program.

The approach to removing barriers to PV for utilities is a network of State working groups that promote PV. Working with the States and supporting the North American Board of Certified Energy Practitioners for “A Voluntary National Certification Program for Practitioners” remained a focal point for the IREC program in 2002 featuring workshops and special sessions at conferences.

There is a huge potential market for installing solar electric systems as an alternative to upgrading aging power lines to existing rural loads in the U.S. If 5 % of all applications in the rural electric cooperative system were replaced with PV, the market would equal 50 MW. Barriers to this large potential market for PV systems are being addressed when NCPV personnel provide analysis and technical assistance to organizations such as the U.S. Department of Agriculture’s (USDA) Rural Utility Service, the U.S. Department of Defense, the U.S. Agency for International Development, the Florida Solar Buildings Program, the U.S. Bureau of Reclamation, Mexico’s Agricultural Secretariat, the Salt River Project, and the Navajo Tribal Utility Authority (NTUA).
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Implementation

As more installations of PV systems occur, the electrical and personnel safety of the systems are undergoing more thorough examinations by designers, installers, inspectors and users. Vital utility and industry issues, such as codes and standards, are continuing activities in the National Solar Program. The program supported work to provide a consensus of industry input into the National Electrical Code® (NEC®), listing and certification standards, and numerous standards activities in both the domestic and the international arena. An "Industry Forum" proposed 24 changes in Article 690 of the NEC for the upcoming 2005 Code and submitted them in October.

The IEEE929-2000 standard spearheaded by Sandia was published in 2000, and now serves to help remove barriers to interconnection of PV systems to the utility grid. The NCPV headed up other IEEE PV standards activities and also actively participated in the International Electrotechnical Commission activities for PV-related international standards. The new IEEE 1547 “Standard for Interconnecting Distributed Resources With Electric Power Systems” received 90 % affirmatives and may soon become a standard after resolution of the negative ballots. Underwriters Laboratories amended the UL1741 "Standard for Static Inverters and Charge Controllers for Use in Photovoltaic Power Systems" and is now considering expansion of the standard to include inverters for all distributed generation.

PowerMark Corporation continued as a non-profit certification body. PowerMark previously recognized the Arizona State University PV Testing Laboratory (PTL) and approved them for performing module certification tests based on the accreditation certificate they received from the American Association of Laboratory Accreditation. Module models have been qualified to IEEE1262 /IEC61215 or IEEE1262/IEC61646 standards since the work began in 1996. The PTL continues to test module types to the UL1703 PV module standard to determine their suitability for listing and has a reciprocity arrangement with European testing organizations. The PTL also announced plans to perform preliminary “Systems Certification Tests” within the next year.

A “National Voluntary Certification Program” for PV installers is being developed with the support of the U.S. DOE PV Program. Most of the critical documentation, logistics and legal work had progressed towards completion of the preparatory stage of the program next year. State funding was also begun in 2002 with cost sharing by New York.
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Industry status

The quantity of PV modules produced in the United States in 2001 reached 100 MW and continued to grow at more than 20 % in 2002. Photovoltaic installations in the U.S. grew to more than 50 MW.

The United States PV applications in 2002 involved virtually all market sectors with the exception of the central power application. The majority of the growth was in the grid-connected sector and was spurred by the national Million Solar Roofs program, the California USD 3,50/W “buy-down, the SMUD USD 3,00/W effective buy-down (to allow < USD 3,50/W costs to the consumer), the Los Angeles Department of Water & Power renewable energy program and other state subsidies in Illinois, New York, and North Carolina.

The U.S. now installs more than 15 MW per year of grid-connected systems. Approximately 7 MW of small, 2- to 4-kW roof-mounted systems are installed on private residences. The systems use all types of PV modules and are sometimes connected to a multiple mode inverter that permits the PV system to first serve the building’s load and then to send excess power to the utility grid. When the grid power is not available, the inverter may be designed to switch to “standby” and power the local load from energy stored in a battery bank.

There are several inverter manufacturers serving the U.S. market. They all have complementary markets for inverters, and some export a large percentage of their product. Much of the U.S. inverter industry has been consolidated under Xantrex of Canada. Xantrex acquired Trace Engineering, Trace Technologies, Heart Interface, and Statpower. Trace Engineering was the largest manufacturer of inverters for stand-alone and utility-interactive systems. Other producers include Advanced Energy Systems Inc., Heliotrope General, and Vanner Weldon. In 2001 SMA (Germany) opened a sales office (SMA America) in the U.S. and now sells its UL-listed grid-connected residential inverters for U.S. applications.
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Market development

Fig. 4 - Naval Base in San Diego, California. This 924 kWp PV system provides long-term covered parking for over 400 vehicles while providing enough electricity to power more then 900 homes. [Photo Courtesy of PowerLight Corporation]

International work included continuation of the Mexico Renewable Energy Program that is sponsored by the U.S. Agency for International Development (USAID) and supported by the U.S. Department of Energy to institutionalize the use of renewable energy technologies. This program had been honored as one of the most successful renewable energy programs for USAID and now serves as a model for increasing the use of renewables in other parts of the world. These projects were implemented in partnership with local Mexican organizations in each geographical or political area to purchase, finance, install and maintain the sustainable systems. This program is resulting in wide-scale system replication, through increased awareness of the benefits of renewable energy technologies, and improved private sector capacities to serve the market.

The NCPV support, such as training and technical assistance in Bolivia, Brazil, China, Ghana, Guatemala, Honduras, India, Indonesia, Kenya, Mexico, Morocco, Nigeria, Pakistan, the Philippines, Russia, South Africa, and Venezuela, has helped U.S. companies continued to make inroads into the international market.
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Future outlook

The U.S. Department of Energy, in partnership with its national laboratories, will continue with strong PV initiatives through the National Solar Program. The “Industry Roadmap” and an updated “DOE PV Program 5-year Plan” will guide the work using a “Systems Driven Approach” to determine priorities based on market needs.
The market development and expansion will include all of the components, interconnects, and materials needed for the PV industry. PV materials, manufacturing processes, balance-of-system hardware, fire and personnel safety, codes, standards, hardware certification and practitioner certification will remain vital elements in the program.

The U.S. DOE Million Solar Roofs Initiative promotes the use of PV and solar thermal to reduce the energy demands of buildings. It enables businesses and communities to install solar systems on one million rooftops across the U.S. The U.S. DOE leads this initiative by working with partners in the building industry, local governments, state agencies, the solar industry, electric service providers, and non-governmental organizations to remove market barriers and strengthen grassroots demand for solar technologies. The “MSRI Action Plan” serves as a guide for the initiative and includes assistance to MSR “State and Local Partnerships” through regional DOE offices, enhancement of financial tools available for solar energy, increased consumer awareness, strengthened ties to other Federal Agencies, encouraged adoption of uniform interconnection standards and codes, support for R&D and testing programs, establishment of certification programs, and encouragement to builders and developers to include solar energy systems.
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Fundamental Research	33 % of the budget
Technology Development	41 % of the budget
Advanced Materials and Devices	26 % of the budget