Photovoltaic Energy Program Overview, Fiscal Year 1997

Photovoltaic Energy Program Overview Fiscal Year 1997

U.S. Department of Energy Message from the Director

he photovoltaic (PV) industry in the United States is booming, claiming a growing share of an expanding T worldwide market that grew 42% in 1997, from 89 megawatts (MW) to 126 MW. The U.S. share of this market amounted to almost 53 MW, which is a 35% increase in one year. And our market share is now 42%Ñmarkedly improved from 1991, when U.S. companies accounted for only 31% of total sales.

Operating at full capacity, with a backlog of orders and with man- Gretz, NREL/PIX03606 Warren ufacturing expansion in progress, the U.S. PV industry is poised James E. Rannels to take advantage of a rapidly changing marketplace. This year saw new products introduced, manufacturing processes improved, capacity expanded, and new materials explored. Conversion efficiencies for cells and modules continued to improve steadi- ly, and PV systems became more reliable.

A solid foundation for the Million Solar Roofs Initiative, announced by President Clinton on June 26, 1997, was laid by the combination of steady research progress in laboratories and universities, industry investment in new PV Sales Projections technology and capacity, and a bur-

1600 geoning market. To help reduce production of harmful greenhouse gases, 1400 Million Roofs Z8-B317503 the President called on the Depart- 1200 Business as Usual Z8-B317503 ment of Energy (DOE) to lead the

1000 effort to place one-million solar energy systems on buildings and homes 800 across the nation by 2010. Half of Megawatts 600 these installations are planned for 400 photovoltaic systems.

200 The Million Solar Roofs Initiative will 0 1995 2000 2005 2010 help the PV industry develop a most Business-as-usual projections based on ÒPV Industry promising large-scale domestic mar- Overview: Domestic and International,Ó Robert ket. As domestic sales increase and Johnson, Mountain View, CA: Strategies Unlimited, prices decline, the industry will fur- 1996. The additions to business-as-usual projections ther enhance its competitive advan- are based on Million Solar Roofs goals. tage in the international market, where two-billion people have roofs PV Price Projections but no electricity. Photovoltaics can 30 generate electricity for these people,

Z8-B317504 with less production of greenhouse 25

Z8-B317504 gases than using fossil fuels.

20 Although one-million roofs is a dra- 15 matic advance from where we are today, it is a modest goal compared 10 to PV's market and technical poten-

5 tial. I expect we will meet the

PV Systems Costs (cents/kWh) Million Solar Roofs objective by 2010 0 and then far exceed it in the years 1995 2000 2005 2010 after. The Initiative adds to the Cost goals derived from ÒPV: The Power of Choice, National momentum that is building around PV Program Plan for 1996-2000,Ó DOE, 1996. the world for the use of solar power. ii PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 And it also complements the strong U.S. Market Share of World Production base of research and development that is the core of our PV Program. 80 70 Z8-B317507

The first step in the Initiative requires 60 nearly doubling the sales of PV products made in the United States by 50 1999. By achieving 7,000 solar roofs by 40 1999 and reaching 1,000,000 in 2010, 30

we will be one of the first programs to 20 contribute to the President's goal of Market U.S. % of World reducing U.S. greenhouse gas emis- 10 0 sions below 1990 levels between 2010 1980 1982 1984 1986 1988 1990 1992 1994 1996 and 2012. We will accomplish even Year more in developing countries, where Information is derived from Paul Maycock, PV greenhouse gas emissions are growing News, January 1998, v.17, n.1, and past issues. the fastest. Working in partnership, we have the opportunity to move PV to a new level of importance in the global energy mix.

The DOE Office of PV and Wind Technologies will continue to support the domestic PV industry. At the beginning of FY 1997, DOE formed the National Center for Photovoltaics specifically to serve as a focal point for industry, end users, and the research community. Through the efforts of the PV community working together, I look forward to continued leadership by the United States in this technology. James E. Rannels James E. Rannels, Director Office of Photovoltaic and Wind Technologies U.S. Department of Energy Washington, D.C.

Cover Photos:

From top left, clockwise: A sheet of thin-film silicon emerges from At the Salinas Missions National the growth chamber of AstroPower, Inc.'s, Monument, New Mexico, a 1.5-kW grid- A National Center for Photovoltaics engi- manufacturing plant. The SiliconFilmª tied PV system provides two-thirds of the neer at Sandia National Laboratories uses product was developed through the DOE power for the Visitor Center and comfort a hail tester to determine the ability of a PV Program's PV Manufacturing station. (National Park Service/PIX05664) PV module to withstand the impact of hail Technology (PVMaT) project. (Rusty stones. (Jim Yost Photography/PIX01820) Ristin, AstroPower/PIX05668) Background photo:

This home built by FIRST (Fully Integrated Using a physical vapor deposition system, This house in coastal Maine generates its Residential Solar Technology) includes a an NCPV researcher at the National own electricity from a 4.25-kW PV system 1.8-kW PV array of amorphous silicon Renewable Energy Laboratory fabricates beautifully integrated into the rooftop. modules. The house, which is near high-efficiency PV devices of thin films of Surplus power is sent back into the utility Princeton, NJ, is not connected to the utili- copper indium diselenide. (Jim Yost grid. (Solar Design Associates/PIX04470) ty grid. (Lyle Rawlings, FIRST/PIX04474) Photography/PIX03524)

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 iii 1997 PV Program Highlights

Systems Engineering and Applications ...... page 2 ■ The Department of Defense ■ To support safe installation of PV ■ The PV Program designed and selected the 450-kW PV array at the systems, the PV Program facilitated built a flexible test bed at the U.S. Army Yuma Proving Grounds industry proposals of more than Outdoor Test Facility for short-term as a Federal Energy Management 50 changes, which have been accept- system performance characterization. Program Showcase Facility. ed, to the 1999 National Electrical The Program also sponsored the 1997 Code. The Program also facilitated a PV Systems and Performance ■ The National Park Foundation proposed standard for utility inter- Workshop, providing the primary awarded Sandia the 1997 National connection of PV systems. forum for communication on system Park Partnership Leadership Award issues between industry suppliers for promoting and expanding the ■ The PV Program facilitated the and users of the technology. use of renewable energy, reflecting development of criteria for laborato- the impact of the 1.5 MW of federal ry accreditation and module certifi- ■ The PV Program established base- agency PV projects facilitated by the cation. These criteria were applied line operation and maintenance costs National Center for Photovoltaics. to Arizona State University PV Test for systems and identified the factors FacilityÑthe first U.S. laboratory contributing to reliability. ■ The PV Program helped to com- accredited by PowerMark Corpo- plete 300 solar PV home-lighting ration to certify PV modules. systems in eight villages of the Sundarbans region in India.

ng to reliability. Technology Development ...... page 9 ■ The PV Program worked to extend turing lines for PV modules made of oped at NREL that has greater pho- the successes of the PV Manufactur- thin-film materials. tothermal stability than current ing Technology (PVMaT) project, commercial formulations. receiving 31 proposals for the new ■ PV Program researchers gained Phase 5A and supporting industrial new insights into failure mecha- ■ Cooperative R&D on balance of manufacturing improvements that nisms affecting the service lifetime systems for PV produced a new, resulted in capacity growth. of modules. 97%-efficient, grid-tied inverter from Utility Power Group. Specifications ■ United Solar Systems Corporation ■ A patent application has been were also developed for a new and Solarex opened large manufac- filed for a new encapsulant devel- 30-kilowatt (kW) hybrid inverter.

Research and Development ...... page 17 ■ United Solar made amorphous al had an efficiency of 14%, and a ■ The PV Program received 63 pro- silicon triple-junction cells with a sta- patent application has been filed. posals for participation in the next ble, total-area conversion efficiency round of Thin Film PV Partnerships. of 12.1%, measured after 1000 hours ■ Siemens Solar Industries tested a of light-soaking. 1-kW copper indium diselenide ■ The Georgia Institute of array having 9.2% efficiency. Technology produced high-efficien- ■ The first PV Program Fulbright cy crystalline silicon cells (19.1% on scholar proposed a theory to explain ■ AstroPower produced a 9.2%, float-zone material and 18.4% on the Staebler-Wronski effect. 321-cm2 monolithically interconnect- Czochralski material) with rapid ed Silicon-Filmª minimodule. thermal processing. ■ DOE's cadmium telluride team developed a new, high-performance ■ NREL received an R&D 100 transparent conducting oxide. The Award for its new software tool, PV first cells produced with this materi- Optics, for cell and module design. iv PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 Introduction

he U.S. Department of tions working in the field has A strategic review held by the Energy (DOE) Photovoltaic grown tremendously. Recognizing NCPV in July 1997 engaged the PV T Energy Program fosters the the benefits of improved communi- community in formulating plans widespread acceptance of photo- cation among these many people, for future activities. This success voltaic (PV) technology and accel- DOE formed the National Center is highlighted in a letter from a erates commercial use of U.S. PV for Photovoltaics (NCPV) in major U.S. PV manufacturer to the products. The Program is founded November of 1996. The NCPV is NCPV. "The workshop played a on a collaborative strategy involv- working to help the U.S. PV indus- valuable role in pulling together ing industry, the research and try maintain its global leadership in key representatives of all sectors of development community, potential the face of intense foreign competi- the U.S. PV community and get- users, utilities, and state and feder- tion. The NCPV currently includes ting their comments and sugges- al agencies. There are three main staff at the National Renewable tions in a documented report that Program elements: Systems Energy Laboratory (NREL), Sandia could be used to help generate a Engineering and Applications, National Laboratories and several national PV plan.Ó Technology Development, and other organizations. Research and Development.

Systems engineering and applications activities make the essential connection between technology and markets. Systems engineering activities help commercialize PV systems by using the PV Program's engineering expertise to assist both industry and users in achieving the highest probability of success that PV systems will work as expected. Applications efforts deploy PV technologies to demonstrate and validate their performance in specific applications.

Technology development projects help new product ideas progress to manufacturing reality. Many PV manufacturing companies have improved their production processes and lowered manufacturing costs through a variety of DOE-supported and cost- shared programs. Photo from NASA Website After decades of use on Earth and in space, PV saw its first use on another planet in 1997 when Sojourner began to explore Mars. These high-efficiency GaAs/Ge cells mounted on top of the Research and development projects vehicle provide 16 watts of power at noon on Mars, enough to perform the mission each day. generate new ideas, develop new theories, build laboratory-scale PV devices that push the limits of conversion efficiency, and address problems inherent in bringing processes from the laboratory to manufacturing.

As PV technology has matured, the number of people and organiza-

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 1 Systems Engineering and Applications Expanding the global market for U.S. PV products

his year the PV Program's systems engineering and applica- T tions activities promoted wider use of photovoltaics at home and abroad. PV projects were installed in the national parks, on military bases, on public lands, on buildings, and in utility systems across the United States. Elsewhere, the Program's efforts placed U.S. PV products in some of the most popu- lous countries of the world. Strategic alliances with end-use industries also fostered opportunities for the U.S. PV industry.

MILLION SOLAR ROOFS I DOE Supports a New Presidential Initiative NREL/PIX05364 Byron Stafford, Sunrayce '97, a solar car race held for university students, was sponsored by General Motors, The President's Million Solar DOE, and Electronic Data Systems. The competition helps engineering students gain practical Roofs Initiative, announced in experience in photovoltaics and automotive technology. The race was held in June, starting in June 1997, is designed to devel- Indianapolis, Indiana, and finishing in Colorado Springs, Colorado. The top 3 finishers out of the 36 entries were California State University, Los Angeles, Massachusetts Institute of op a large-scale domestic market Technology, and Stanford University/University of California, Berkeley (shown here). Plans are for PV by increasing sales and under way for Sunrayce '99. reducing prices. By 2010, one million solar energy systems are proposed to be operating on the mation/marketing package was Through the efforts of the PV nation's roofs. The Initiative tar- designed for each of five target Program's Markets and Applications gets cost-effective applications groups: embassies, organic farmers, team, as many as 750,000 people of PV and reaches out to many the military, recreational vehicle were introduced to the possibilities groups within communities clubs, and home improvement stores. of PV in 1997. These efforts included across the United StatesÑ DOE also developed and implement- such high-visibility events as the groups that include city plan- ed Solar Finance, the first-ever Pageant for Peace (a PV demonstra- ners, housing developers and national consumer finance program tion on the Mall in Washington, builders, utilities, PV manu- for PV and solar-thermal projects. D.C.), the National Western Stock facturers and suppliers, and The PV Program co-sponsored a pro- Show in Denver, and Sunrayce 97, as home owners. ject to develop a database of mort- well as a growing number of interna- gage lenders willing to finance grid- tional projects. independent homes and is negotiat- ing with Bank of America to develop Utilities Market Conditioning a national grid-independent home mortgage program. PV4U, managed The coming restructuring of the utili- In the on-going effort to educate by the Interstate Renewable Energy ty industry will catapult applications potential users of PV technology, Council, continues its work with mul- of PV technology into many new DOE is working with the Solar tiple stakeholder groups and con- locales. PV offers an easy way for Energy Industries Association and sumer and environmental constituen- utilities to diversify into new, previ- Photovoltaics for Utilities (PV4U) cies. PV4U state working groups ously unserved remote markets. PV working groups. This year, an infor- now number 14. offers fast construction with an

2 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 York, and Massachusetts. If other al activities on net metering and con- MILLION SOLAR ROOFS II factorsÑtax credits, depreciation, sumer incentive programs. Legis- Million Solar Roofs financing, leasing, and giving full lation was introduced in seven states retail credit for PV-generated elec- this year and passed in three, bring- Initiative Is a tricity (net-metering)Ñare added, PV ing to 20 the number of states that Collaborative Effort becomes a cost-effective choice in have some form of net metering. many other areas. Million Solar Roofs will be imple- U.S. government agencies mented at the state and local The Utility PhotoVoltaic Group level largely by groups that have (UPVG), formed in 1992, is a group Facilities operated by federal, state, been working with the DOE of more than 80 utilities and associ- and local governments present Program to promote PV. For ations working to commercialize many opportunities for cost-effective example, the Utility PhotoVoltaic PV systems. UPVG, whose member installations of PV. With more than Group has already initiated sev- utilities represent more than 40% of 500,000 rooftops, the federal govern- eral commercial and community U.S. electricity sales, gets financial ment is the world's largest owner of efforts for the President's Million support from its members and buildings. The U.S. government Solar Roofs Initiative. In another from DOE. As of this year, there spends more than $3 billion each effort, the California PV Alliance, were 24 UPVG ventures under con- year on electricity for buildings. a PV4U working group, helped tract. As many as 35 utilities are State and local governments also develop the California Solar directly involved in 25 states with own and operate many facilities that Fund, which is a proposal to pro- commitments for more than 1300 could save money by installing PV. vide consumer incentives to pur- PV installations. A total of 1.5 MW The PV Program facilitated the chase PV systems. The proposal, is installed and an additional installation of 1.5 MW of PV systems submitted to the $540 million 6.7 MW are planned. The NCPV in government installations this California Renewables Trust provides technical assistance dur- year. These ranged widely in pur- Fund, is a model for state imple- ing the planning and installation of pose, size, and location, but the mentation of the Million Solar these ventures. majority were less than 1 kW, for Roofs Initiative. uses such as providing power at This year, DOE laid the groundwork remote recreational sites or pumping for expansion in the restructured groundwater to reduce demands on acceptable environmental impact. electricity market through education- surface waters. One NREL PV publication highlights the best U.S. locations for grid-connected PV systems. Another publication maps effective load-carrying capacityÑa measure of how well PV can meet customer demand. A good example of high capacity for PV is in regions where midday air-conditioning demands are high. There, PV has a high tan- gible value to utilities in generating capacity to meet peak loads.

While PV can boost a utility's capacity at peak times, it can also serve homes and buildings directly. Such individual units, connected to the utility grid, are cost-effective now in

regions such as Oahu, Hawaii, where Sandia National Laboratories/PIX05788 conventional electric energy costs The 450-kW PV array at the U.S. Army Yuma Proving Grounds in southwestern Arizona is may exceed $0.12 per kilowatt hour. shown. Photovoltaics offered an excellent solution for Yuma because PV can generate the most An NREL study shows that the best electricity at the same time that Yuma experiences its peak demandÑon summer afternoons immediate markets for PV are in when the sun is shining and all air conditioners are on. (Utility Power Group, ASE Americas, Hawaii, California, Arizona, New C&D Batteries, and Trace Engineering)

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 3 Department of DefenseÑThe Costs for generating this electricity at erplant at the U.S. Army Yuma Department of Defense (DoD) con- remote locations may rise to $1 bil- Proving Ground in 1997. The sys- sumes more energy than any other lion per year. tem, tied to the utility grid, can user in the world. Utility bills for operate three different ways: it can DoD run more than $2 billion a year The PV Program has worked with supply the grid with up to 375 kW for about 35,000 billion kilowatt- DoD for more than a decade to of ac power directly from the PV hours of electricity. In addition to make PV an option at military array; it can power a critical water- electricity purchased from utilities, installations. Thanks to early studies treatment plant during utility out- DoD also generates about 3,000 that identified more than 50,000 ages; and it can supplement the gigawatt-hours of electricity at cost-effective projects within DoD, array power with battery power to remote locations using fossil fuels. standard military construction prac- supply up to 925 kW for maximum tice now includes considering PV. peak-shaving benefit. But for large installations (more than MILLION SOLAR ROOFS III 100 kW), there were no suitable In developing the Yuma project, sys- power-processing units on the mar- tems integration and power-condi- Utilities Are ket to convert direct current gener- tioning technologies have advanced Important Partners ated by PV into the alternating cur- significantly. Now that this technolo- rent most commonly used. To devel- gy base exists, more large-scale, PV One of the first successful op, test, and demonstrate the neces- powerplant applications can be iden- models that could be followed sary new power-processing tech- tified and implemented within DoD. for the Million Solar Roofs nologies, the PV Program worked The Yuma facility and its power-pro- Initiative is the PV Pioneer pro- with the military using funding cessing and control technology were ject of the Sacramento from the Strategic Environmental selected as one of DoD's Federal Municipal Utility District. Research and Development Energy Management Program Participants pay less than $10 Program (SERDP). Showcase Facilities. At the moment, per month extra to "host" a the Yuma system is unique; but there 4-kilowatt rooftop PV system Funding through SERDP and DOE are perhaps thousands of mini-grid, that feeds power back to the has made several showcase mili- as well as remote and grid-connect- utility. In return, these cus- tary installations of PV possible. ed, DoD facilities that could take tomers are guaranteed that For example, this year, after five advantage of the economical and their electricity rates will years of planning and testing, environmental benefits demonstrat- not increase for 10 years. Sandia's researchers helped DoD ed at Yuma. install a unique grid-tied PV pow- PV in the Parks and on Public LandÑThe National Park Service, the U.S. Forest Service, and the Bureau of Land Management (BLM) all have large recreational areas without an electric power infrastructure. Such dispersed power needs can be met by PV systems designed to standardized specifications. For example, BLM took advantage of standardiza- tion with this year's installation of six 4-kW PV water pumpers in the Richfield District of Utah. Other PV installations completed by the BLM this year provide nearly 40 kW for lights and power for campgrounds, rest rooms, and host trailers in California, Colorado, Idaho, Oregon, Utah, and Wyoming. Sandia National Laboratories/PIX05787 BLM campground hosts, as this one in Utah, rely on PV power to make their remote locations In another project that took advan- more comfortable. (Applied Power Corp., Solarex, Absolyte, and Trace Engineering) tage of a standardized, packaged PV

4 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 National Park, Yosemite National Park, and Sleeping Bear Dunes National Lakeshore.

PV Partnerships with the StatesÑ Working at the state level through the Interstate Renewable Energy Council (IREC), Sandia awarded 11 contracts in 1997 to state agencies, utilities, and other organizations across the United States that had not previously installed a PV project. For example, an IREC project in cen- Currin Corporation/PIX05667 tral Texas uses PV to pump water This 11.2-kW PV array is part of the hybrid solar/diesel generator power system on North Manitou Island at Sleeping Bear Dunes National Lakeshore, Michigan. Three identical sub- for livestock, with the utility charg- arrays provide a total peak current of 75 amps for charging a 288-kW, 120-V battery bank. ing farmers a special rate developed (Currin Corp., Solarex, Absolyte, and Advanced Energy Systems). just for PV. Farther north, the Wisconsin Department of Natural Resources is identifying cost-effec- system made possible by the PV the nation's parks with the on-going Program, the National Park Service effort to define standardized PV tive applications for PV throughout installed a PV array at Salinas Pueblo packages. For example, a hybrid its 60-facility system. How these Missions National Monument in PV system installed at Pinnacles first-time users of PV work their New Mexico. This newest project in National Monument last year was way through a project will be docu- the PV Program's "Renew the Parks" the model for a 7.5-kW system mented by Sandia and IREC. partnership with the National Park being installed in North Cascades Service benefited from Sandia's tech- National Park this year, as well as Building-integrated nical support and includes a 5-year, for other units now being readied photovoltaics full-service agreement. for Joshua Tree National Monument and Mohave National Preserve. Residential, commercial, and institu- Sandia received the 1997 National Other "Renew the Parks" PV sys- tional buildings consume about 67% Park Partnership Leadership Award tems were completed and installed of the electricity generated in the from the National Park Foundation this year at the North Rim of the United States. To encourage the for promoting and expanding the Grand Canyon, Navajo National development of PV systems that use of renewable energy throughout Monument, the Channel Islands work with building designs, DOE

Photovoltaics Systems Assistance Center he Photovoltaics Systems Assistance Center The PVSAC also manages DOE contracts for the (PVSAC) at Sandia promotes the use of PV Southwest Technology Development Institute at New T technology through publications, technical Mexico State University in Las Cruces and the Florida assistance, and engineering evaluations. In 1997, the Solar Energy Center at the University of Central Center distributed more than 10,000 PVSAC publica- Florida in Cocoa. The Florida Center focuses on build- tions, including the newly published NEC Recom- ing-integration issues at the component level. The mended Practices, a manual of safety practices, and Southwest Institute works with hybrid systems. Both Renew the Public Lands, which identifies a large groups conduct site surveys, "snapshot" one-day eval- potential BLM market for the U.S. PV industry. In uations of the reliability of installed PV systems, and addition, PVSAC provided significant technical monitor other PV installations over a period of months assistance to 106 requesters from the PV industry to analyze their performance. PVSAC, through these and 128 users of PV systems. contractors, performed technical evaluations at 24 utility and federal agency sites and prepared nearly 200 data reports for monitored sites.

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 5 initiated PV:BONUS (Building for many agricultural uses such as raising health and living standards, Opportunities in the United States electric fences, water pumping, and so DOE is supporting the installation for Photovoltaics) in 1993. battery charging. Any small applica- of renewable energy projects in tion where utility power is farther emerging energy markets around the The PV:BONUS project funded the than several hundred feet away is a world. This year, DOE supported PV development of several commer- candidate for PV systems. The projects in the world's two most pop- cial products for the building Photovoltaic Services Network, ini- ulous countries, China and India. industry. For example, the award- tially supported by the PV Program, winning flexible solar shingle and publishes an annual catalog of "pack- IndiaÑAn agreement between DOE solar-electric metal roofing of aged" PV systems for remote resi- and the Ministry of Non-Conven- Energy Conversion Devices, Inc., dential use, water-pumping, and tional Energy Sources of India calls are now available as commercial security lighting. In 1997, NREL for sharing project costs 50-50 to products. The shingle modules are published Photovoltaics for Farms and demonstrate the economic viability currently being produced at a rate Ranches, a 24-page brochure detailing of PV systems in India. This year, of 40 kW per month. PV uses in remote agricultural appli- 300 solar PV home-lighting systems cations. In addition, travelling in eight villages in the Sundarbans Other PV:BONUS projects are moving exhibits spread information about region were completed by the toward the marketplace. The large- PV at stock shows and agricultural Sustainable Rural Electrification area ac PV module and micro-invert- equipment conventions across the Project with the Ramakrishna er developed by Solar Design nation's farm belt. Mission in West Bengal, India. Associates, Inc., received Underwrit- ers Laboratories (UL) certification this International markets ChinaÑA U.S./China summit held year. In addition, four grid-connected, growing for U.S. products in Beijing in October 1997 proposed dispatchable PV peak-shaving sys- a Joint Program on Rural Electrifi- tems developed under PV:BONUS Some 40% of the world's population cation including village power, solar contracts have been installed by does not have access to electricity. home systems, hybrid PV/wind/ Delmarva Power and Light Company, Providing electricity is essential for diesel systems, grid-connected wind- an investor-owned electric and gas utility headquartered in Wilmington, Delaware. Modular solar homes being developed by a consortium of builders, PV manufacturers, and utilities have been erected in the Washington area and in Philadelphia. The Philadelphia homes had substantially lower construction costs ($20 per square-foot less) than conventional homes in the community.

To expand on the success of the orig- inal PV:BONUS contracts, 17 new awards were made in 1997 under Phase I of PV:BONUS Two. The objective of PV:BONUS Two is to develop technologies and to foster business arrangements that integrate PV or hybrid products into buildings and demonstrate commercially viable products. PV and agriculture

PV systems are reliable, require little United Solar Systems Corp./PIX05673 maintenance, and put power right Embedded in these roof shingles are advanced, triple-junction amorphous silicon cells developed where it is neededÑa primary asset by United Solar Systems Corp., within the Thin Film PV Partnership.

6 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 farms, biomass gasification, and geothermal energy use. DOE and NREL cooperative work in China is expanding the work of the Solar Electric Light Fund (SELF). SELF established a system of credit for homeowners to finance PV systems in the Gansu province. The revolving credit accounts, managed by a local nonprofit group, were used to pur- chase equipment and services from local vendors. PV has now been installed in 300 households and 10 schools. The World Bank is also interested in developing renewable energy in China and, as applications expand, the potential market for U.S. PV products will also expand.

BrazilÑA good example of how DOE's international projects help open markets to U.S. industry is the DOE effort in Brazil. More than 90% of the PV systems now in place were purchased from U.S. suppliers. This includes cooperative projects in five Brazilian states where DOE work is now integrating system designs and Harin Ullal, NREL/PIX 05161 developing in-country installation This PV module installed on a roof in an Indian village is part of the Ramakrishna Mission PV and maintenance expertise. project in Sundarbans, West Bengal, India. (Solarex modules; Morningstar charge controllers; Applied Power Corporation, systems integration; Remote Power International, training). South AfricaÑDOE and NREL are working with Renewable Energy for South Africa, the U.S. Agency for Development on the development of Systems Engineering International Development, the pilot renewable energy projects in National Rural Electric Cooperative Mexico continues to demonstrate sig- Standards and codes Association, and Renewable Energy nificant results. In 1997, the rate of for African Development to bring project implementation doubled and To be successful in global markets, stand-alone renewable power sys- there are now more than 120 PV sys- PV products must not only work tems to 16,000 schools and 2,000 clin- tems installed in eight Mexican well, they must also meet interna- ics. The first step is a pilot program states. The applications are primarily tionally recognized standards per- using 2500 PV systems for off-grid water pumping for livestock and formance and safety criteria. One rural electricity. DOE is also assisting power for ranger stations. Sandia effort to specify the performance the South African government in manages this program and NREL and safety of PV systems is the PV restructuring the electricity sector. provides technical assistance. While Global Approval Program (PV GAP). U.S. analysts work with their coun- the U.S. cost share for the pilot pro- This program an international effort terparts in South Africa to analyze jects has been declining, the U.S. PV to certify PV components and sys- power generation, transmission, and industry is gaining more access to tems, includes representatives from distribution. In addition, NREL per- Mexican markets. In FY 1997, one of the NCPV on its board of directors sonnel will help train South Africans Sandia's principal Mexican partners, and working committees. To sup- about the utility requirements for PV the Mexican Trust for Shared Risk port these efforts, DOE provides and other renewable energy sources. (FIRCO), began implementing parts funding to the International Energy of a $1.8 billion agricultural develop- Commission-Technical Committee MexicoÑDOE's collaboration with ment program that explicitly includes 82 effort. Standards are especially the U.S. Agency for International renewable energy equipment. important for PV products

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 7 designed to operate dependably in procedures and specifications for Institute in August to discuss issues a variety of applications. Standards evaluating PV modules developed by about PV performance and reliabili- are now being developed for PV the Institute of Electrical and ty. Nearly 100 people joined in dis- concentrator systems. Electronics EngineersÑ IEEE 1262Ñ cussions of PV systems issues, heard this certifying facility applies the about lessons learned from field test- The DOE PV Program has long DOE-facilitated criteria developed for ing, and focused on real concerns for worked to develop both domestic laboratory accreditation and module large, grid-tied PV systems. Specific and international standards, codes, certification. Industry involvement in topics included problems and resolu- and certification programs for PV this effort was key to its success. tions with power conditioners, con- products. This year the work paid off trol systems, and maintenance of as PV products began to achieve the The National PV Program operates remote PV systems. Underwriters Laboratories (UL) list- test facilities to support research and ings necessary for consumer confi- validate performance of products for In FY 1997, in a partnership with the dence. In addition, DOE facilitated the PV industry. To adapt to different PV industry and PV system owners, industry proposals of more than standardized tests of modules and NCPV researchers at Sandia quanti- 50 changes to the 1999 National systems, the Program added a flexi- fied baseline operation and mainte- Electrical Code that would support ble test bed to the Outdoor Test nance costs of systems. Factors con- the safe installation of PV systems. Facility at NREL. The flexible test tributing to reliability were identi- These changes have been adopted. bed, which can run a variety of stan- fied and modeled, and these results The Program systems engineers also dards tests, will be used to validate will be used for future system facilitated a proposed standard for interface compatibility test methods improvements. utility interconnection of PV systems. for small PV systems.

This year, the Arizona State University Performance and reliability PV Test Facility became the first U.S. laboratory to be accredited by the Industry and key users joined the PowerMark Corporation to certify PV national laboratories and the modules. Using the recommended Southwest Technology Development

8 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 Technology Development Modifying successful laboratory techniques for industrial production

his year the PV Program 8 worked with PV compa- 7 M72-B148401

nies in several ways to 1992 M72-B143401 T Direct manufacturing increase the conversion efficiency 1994 6 costs only of potential new products and 1995 improve manufacturing tech- 5 PVMaT participants with active manufacturing niques for current and future 4 lines (12) products. The Program conducted 1996 1997 data applied research and tested new 3 concepts through the PV 1998 ÒAverageÓ module ÒAverageÓ Manufacturing Technology 1993 1997 1999 2000 2 2001 2002 (PVMaT) and Thin Film PV manufacturing cost ($/Wp) 2003 Partnership programs, cooperative 1 research and development agree- 0 ments (CRADAs), and in-house 0 50 100 150 200 250 300 350 400 450 500 550 research at the DOE laboratories. Total manufacturing capacity (MW)

PVMaT Repays A PVMaT study shows that manufacturing costs have declined and are expected to Investments decline further as manufacturing capacity increases over time.

To enhance the worldwide competi- The PVMaT project is both help- ¥ Improve manufacturing tiveness of the U.S. PV industry, ing the U.S. PV industry to processes Congress approved funds for the extend its world leadership in ¥ Accelerate manufactur- PVMaT project in 1990. Sharing manufacturing and stimulating ing-cost reductions for PV costs between the PV Program and commercial development of PV modules the individual manufacturers, the modules and systems. The objec- total funding to date for PVMaTÑ tives of PVMaT are to help ¥ Improve commercial including some 43% from indus- industry: product performance tryÑis about $146 million. ¥ Lay the groundwork for substantial scale-up of U.S.-based PV manufac- Solarex CRADA Supports Scale-Up of turing capabilities. a-Si Module Manufacturing PVMaT's success in reducing the manufacturing cost of U.S. PV Making larger modules is an important step to move prototype tech- products repays both manufactur- nologies toward manufactured products. To help scale up Solarex's ers and U.S. taxpayers for their multijunction amorphous silicon technology from 4-ft2 prototypes to investments. Since 1990, PVMaT 8.6-ft2 commercial modules, NREL and Solarex began a 24-month, has teamed the PV Program with $794,000 (roughly 50-50 cost-shared) CRADA. The new, larger mod- industry in five separate staggered ules can be used in building-integrated PV applications, solar farms, phases, to support the evolution of and more-traditional remote applications. technology in the industry. This There are five major tasks in the CRADA: step-wise development process has ¥ Characterize amorphous silicon multijunction modules. been instrumental in the success of ¥ Characterize materials and devices. the U.S. PV industry. ¥ Study the stability of amorphous silicon alloys and devices. Systems and components ¥ Test reliability. for PV products ¥ Identify and eliminate defects. In most cases, modules comprise less than half the cost of PV sys-

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 9 tems. Therefore, improving system inverter by 70%, simplified control listed. It is currently being shipped integration and the rest of the sys- circuits to reduce costs 5 cents per to several utilities for long-term tem componentsÑsuch as mounting watt, and improved magnetics to performance tests. designs and power-processing hard- reduce overall unit cost by $2000. wareÑcould lower the cost of PV Evergreen Solar, Inc., Waltham, MA, is systems significantly. Phase 4A1 Ascension Technology, Inc., Waltham, developing new materials to facili- contracts under PVMaT may MA, is working with ASE Americas tate continuous, in-line manufactur- address either components or com- Corp., Billerica, MA, to develop an ing of PV modules for high-volume plete systems with optimized com- Underwriters Laboratories-listed ac mass production. Most module ponents or specialized components PV module rated at 240 to 300 encapsulants require a vacuum cur- for PV generation. watts. This unit combines ASE ing stage that can only be performed Americas' PV module, which pro- in batches, thus slowing production. Advanced Energy Systems, Inc. Wilton, duces dc electricity, with Evergreen is developing an encapsu- N.H., developed a next-generation Ascension's ac inverter. In 1997, the lant that can be processed in a con- prototype 60-kW inverter for both module-sized inverter was fully tinuous assembly line, without vacu- grid-interactive uses and hybrid integrated with ASE Americas' um curing. Evergreen also devel- applications such as conditioning PV large-area PV module and the oped a novel hard backskin material and/or wind-generated electricity assembly was Underwriters that serves as the frame, as well as for village power or remote military Laboratories-listed and certified by the backskin for modules. It also can applications. The new design incor- the Federal Communications be processed continuously. A new porates simpler manufacturing steps Commission. Innovations included innovative mounting design allows and remote monitoring. WPI Power a new mounting and quick-connec- mounting brackets to be bonded Systems, Inc., of Warner, NH, built tor design and a "Zebra" anti- directly to the backskin. the inverter and assisted with the islanding circuit. The assembly was magnetics design. During Phase delivered to the NCPV for develop- Omnion Power Engineering 4A1, Advanced Energy Systems, Inc., ment tests. This PV unit is the first Corporation, East Troy, WI, working reduced the physical size of the to be Underwriters Laboratories- with Soft Switching Technologies,

Phases of the PVMaT Program

Phase 1: Problem Identification Phase 4A: Process-Specific Problem Solutions Twenty-two companies identified projects to improve Phase 4A1ÑEight companies began 2-year subcon- PV module manufacturing. All subcontracts were tracts in 1995 to develop system and component tech- completed in 1991. nology for PV products. Phase 4A2ÑFive companies began 3-year subcon- Phase 2A: Process-Specific Problem Solutions tracts in 1995 to address company-specific manufacturing issues to reduce costs and increase the capacity Seven companies carried out their recommendations of their production facilities. These subcontracts are from Phase 1 to perform manufacturing R&D intend- similar to research carried out with other companies ed to decrease PV module manufacturing costs and under phases 2A and 2B. increase manufacturing capacities.

Phase 2B: Process-Specific Problem Solutions Phase 5A: Process-Specific Problem Solutions Thirty-one proposals were received for Phase 5A, Four companies carried out projects similar to those of announced in June 1997. Phase 5A awards, similar to Phase 2A. These 3-year subcontracts began in FY 1994. the 4A awards, will emphasize product-driven manufacturing R&D for improvements and cost reductions Phase 3A: Generic Problem Solutions in manufacturing full-system PV products and are Two companies addressed issues common to the planned for early 1998. entire PV industry. These subcontracts, begun in FY 1993, were completed in FY 1996.

10 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 Inc., is developing a 100-kW proto- Trace Engineering, Arlington, WA, is Research and development type 3-phase power conversion sys- developing, testing, and modifying for module manufacturing tem for utility-interconnected PV its manufacturing methods to pro- applications using a resonant core duce a lower-cost, higher-perfor- Under Phase 2B of PVMaT, several inverter. In 1997, this system exhib- mance, 2-kW ac inverter for the PV contractors continued work in FY 1997. ited more than 97.5 % efficiency at industry. The inverter, which can be Solar Cells, Inc. (SCI), Toledo, OH, is peak power and more than 92% in combined by 2-kW increments to developing a high-speed manufac- the range from 10% to 100% of rated serve larger systems, converts ac turing process for 60-cm by 120-cm, power. Audible noise was reduced power to dc, or dc power to ac, as thin-film cadmium telluride mod- to less than 50 decibels, and FCC required. This standardized, uni- ules. In FY 1997, SCI fine-tuned a standards for electromagnetic inter- tized approach to manufacturing system to increase production capac- ference were met. Omnion goals and the ability to incrementally add ity by a factor of four, demonstrated include a cost of less than 50 cents capacity is expected to reduce costs module deposition in 30 seconds, per watt in high-volume produc- and improve reliability. In 1997, and completed module qualification tion, 96%-97% efficiency, and Trace Engineering improved the and multi-year outdoor testing for Underwriters Laboratories listing modes of operation and hardware reliability. SCI also completed instal- for the product. modularity for their inverter. A pro- lation of key equipment for a multi- totype of the 2-kW inverter that can megawatt line and initiated market- Solar Design Associates, Inc., Harvard, be used in parallel, in 3-phase sys- ing of manufacturing technology MA, leads a team in refining the tems, and expanded up to 30 kW, offering a variety of CdS/CdTe pro- design of a modular inverter devel- was delivered to Sandia for testing. duction lines and plate finishing oped under the PV:BONUS program. Trace also completed development lines. SCI, whose work was also A digitally controlled, 250-watt and achieved Underwriters supported by the Thin Film PV micro-inverter has been developed Laboratories listing of a standard- Partnership program, has reduced by SDA's partner, Advanced Energy ized containment system for invert- module manufacturing costs by 78% Systems, Inc., of Wilton, NH. The ers, controllers, and batteries. and expects to increase its produc- unit has microprocessor control and tion capacity to 20-30 MW per year full communications capabilities. In Utility Power Group (UPG), in the near term. 1997, AES completed Underwriters Chatsworth, CA, has designed, built Laboratories listing for this digitally and tested a prefabricated, tracking Solarex, Frederick, MD, is reducing the controlled micro-inverter, which is PV array that includes a 20-kW cost and increasing the performance easier to manufacture than the previ- inverter and power-conditioning of its commercial products made of ous analog design. unit called an Integrated Power cast polycrystalline silicon. Solarex Processing Unit (IPPU). During assessed each production step: cast- Solar Electric Specialties, Willits, CA, is 1997, UPG received 60 orders ing the material, sawing ingots, pro- a systems integrator. SES works with (800 kW) from utilities for this sys- cessing cells, laminating, and finish- suppliers to enhance the suitability of tem. The IPPU includes power con- ing. Improvements incorporated currently available PV system compo- version from dc to ac, a power con- into the processing of cells should nents. They are working to design, troller, and data-gathering access, reduce costs and increase the mini- fabricate, and test two PV power sys- all packaged as one unit for ease of mum average cell efficiency to 15%. tems for off-grid applications. In installation. UPG teamed with For example, Solarex reduced mod- 1997, SES obtained Underwriters Siemens to increase modular panel ule manufacturing costs during Laboratories listing on the MAPPS production of factory-assembled FY 1997 by modifying its production (Modular Autonomous Photovoltaic PV panels and reduced the overall line to use wire-sawing techniques Power Supply), a 12- and 24-V dc, system cost by 20% while increas- and has doubled its capacity in sili- 200-W PV power supply. This pole- ing modular panel production from con ingot casting. Solarex expects to mounted, stand-alone PV power sup- 20 kW to 5 MW. They also devel- produce modules for about $1.20 per ply minimizes weight and cost. The oped a high-efficiency (97%) invert- watt with a 15-megawatt-per-year l-kW MAPPS was delivered to the er for the system which passed all production capacity. NCPV for testing. A 1-kW photo- tests at Sandia. UPG reported a genset, also nearing completion, com- total net cost reduction of more Phase 4A2 of PVMaT, which began bines a generator, inverter, and PV than 20% for a 15-kW PV system in FY 1995, continued in 1997. power supply in a containerized PV- after changes in PV array assembly hybrid system. The unit is expected to methods, field installation meth- ASE Americas, Inc. (formerly Mobil be completed in early FY 1998. ods, and the IPPU. Solar), Billerica, MA, manufactures

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 11 Since PVMaT began, they have reduced module manufacturing costs 23%.

Iowa Thin Films Technologies, Inc. (ITF), Ames, IA, is increasing their throughput of a-Si deposition on continuous polymer substrates, and the subsequent metalization, laser- scribing, and welding processes to reduce costs. In FY 1997, ITF increased throughput in the printer and scriber by a factor of 6. Work on

Rusty Ristin, AstroPower/PIX05668 Rusty Ristin, their submodule lamination process Thin-film silicon sheet emerges from the growth chamber at the AstroPower plant. The com- has increased throughput from 20 to 2 pany's current commercial product is 15.5 cm wide, with sheets from prototype production 240 ft per hour. Other areas of measuring 30 cm wide. advancement included improving printing registration reproducibility PV wafers, cells, and modules using greater variety of products for differ- from 100 to 10 microns. Under an edge-defined, film-fed growth ent markets. In 1997, AstroPower PVMaT Phase 4A2, ITF has reduced (EFG) process developed at Mobil fabricated the world's largest pro- a-Si module manufacturing costs by Solar. ASE's goal is to reduce wafer, duction silicon solar cell (240 cm2), 42% and increased production capac- cell, and manufacturing costs by 25% initiated production with a continu- ity by a factor of 4. relative to pre-PVMaT Phase 4A2 ous Silicon-Filmª growth process levels. In this effort, ASE is using a that is 10 times faster than compet- Siemens Solar Industries, Camarillo, PVMaT-developed lower-cost, envi- ing processes, and established a CA, is reducing the cost and improv- ronmentally safe process to remove record efficiency of 16.6% for a 1 cm2 ing the reliability of their commer- their diffusion glass from the wafers. solar cell. The latter accomplishment cial, Czochralski, crystalline-silicon In 1997, ASE increased EFG wafer was one year ahead of the contract modules. They are testing prototype production yield by 5%; demonstrat- milestone. In Phase 4A2, Astro- modules from larger, 225-cm2 cells, ed a new benign wafer-etching Power reduced module-manufactur- which can reduce module costs per process; lowered cell add-on producing costs by 13% and increased pro- watt by 18% and increase manufac- tion cost by 7%; and reduced fluo- duction capacity by a factor of 4. turing process yields by 15%. rine-ion effluent in the waste stream by 50%, hydrofluoric acid consumption by 20%, and deionized water consumption by 20%. With these changes and improvements in solar cell fabrication technology, ASE has reduced module manufacturing costs by 26% and doubled EFG module production capacity. Since PVMaT began, ASE has reduced module manufacturing costs by 75% and increased their production capacity by a factor of 10.

AstroPower, Inc., Newark, DE, is reducing the manufacturing cost of

its commercial Silicon-Filmª materi- Frank Jeffrey/PIX05674 al cells and modules. Their approach Iowa Thin Films Technologies, Inc. supplied the solar array for the Indian Creek Nature Center is to make the material in wider outside of Cedar Rapids, Iowa. The panels provide about 200 watts of electricity, enough to run sheets that make better use of the the low-wattage, energy-efficient lights. The Center, a project of the Iowa Department of Natural material, require less labor per area Resources, demonstrates the use of energy-efficiency and renewable-energy technology through- of modules produced, and allow out its facilities as part of Iowa's commitment to environmental education.

12 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 Breakage can reduce yields by 20% to 40%, so Siemens is also investigating lowering costs through reduced breakage, while continuing to make thinner cells. In addition, a new prototype junction box combines low cost with improved design. In FY 1997, Siemens implemented statisti- cal process controls on the manufacturing line, initiated production of a new PVMaT-developed, 150-mm thick round cell, and brought a semi- automated lamination process on line. Siemens has reduced module

manufacturing costs under their United Solar Systems Corp./PIX05671 PVMaT research by 16%, with 10% United Solar makes its a-Si alloy triple-junction thin film using a roll of stainless steel half a of this under Phase 4A2 alone. They mile long, 14 inches wide, and 5 mils thick. The roll passes through four machines, where it is have also doubled their module pro- washed and layers are deposited. The coated web is then processed to make a variety of products. duction capacity.

Photovoltaics International (formerly power systems. The PV Program SolarexÑopened large manufactur- Solar Engineering Applications contributed directly to such expan- ing lines for modules made of thin- Corporation), Sunnyvale, CA, is reduc- sion through the successes of the film materials. United Solar, a joint ing manufacturing costs for its linear Thin Film PV Partnership program, venture of Energy Conversion concentrating PV modules by PVMaT, cooperative research and Devices and Canon, Inc. (Japan), expanding the continuous processing development agreements, and began producing a-Si triple-junction of key components. In 1997, they national laboratory work in mea- alloys at their new 5-MW plant in developed an in-house capability to surements and characterization. Troy, Michigan. Around-the-clock extrude Fresnel lenses which low- operations began in May 1997, with ered product costs by 37%. They This year, two companiesÑUnited products ranging from 3 to 64 watts. also increased lens manufacturing Solar Systems Corporation and The United Solar a-Si devices are capability to 5 MW/year and completed the first half of an automated 12 receiver-assembly station. They continue to investigate a new way to Initial active-area efficiency Z8-B317501 bond plastic collector components Z8-B317501 Subcell yield without using solvents. PVMaT 4A2 results have reduced module manu- 1.0 facturing costs by 41% and increased 11 linear-concentrator production capacity by a factor of 5.

Progress in Technology 10 0.8 Results in Industrial Expansion Subcell yield > 0.6 fill factor

In 1997, major U.S. crystalline and (%) Initial active-area efficiency amorphous silicon manufacturers 9 0.6 such as ASE Americas, Siemens 100 400 700 1000 1300 1600 1900 Solar Industries, and United Solar Slab number Systems Corporation increased their production capacity and shipments On the United Solar production line, samples are taken at regular intervals along the half-mile-long Initial active-area efficiency ( ) and subcell yield ( ) versus by around 40% to help meet the roll of a-Si alloy triple-junction thin-film cells to evaluate efficiency and yield. Yields of close to 100% slab number for a 2000-foot production run from the 5-megawatt line. rapidly expanding market for PV are achieved over the entire length of the roll, as illustrated here.

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 13 will use the results of its CRADA ments of wafers produced by the MILLION SOLAR ROOFS IV with DOE in its new thin-film manu- AstroPower production facility were facturing plant in Virginia. This made in 1997 by NREL. Expansion of PV plant is capable of producing 10 MW Industry Supports Million of tandem-junction thin-film mod- Module and Array Solar Roofs Initiative ules each year. Development

The U.S. PV industry has more Measurements in This year, tests and analyses point to than doubled its manufactur- the Manufacturing improved techniques and validation ing capacity in the last three Environment of new technologies. years, while average manufacturing cost has fallen 32%. By To monitor and grade the quality of New products of thin-film 2000, industry projections are a polycrystalline thin-film and silicon materials test well production capacity exceeding solar cells, a contactless, nondestruc- 200 MW and manufacturing tive, and real-time manufacturing- To provide important information to costs below $2/watt. This solid line method was developed at industry on evolving thin-film tech- base of domestic production NREL. Known as Phase III radio-fre- nologies, the PV Program's Outdoor capacity makes possible an ini- quency photoconductivity decay life- Test Facility (OTF) continued ongo- tiative like Million Solar Roofs. time spectrometry, the measurement ing studies of prototype thin-film (from PVMaT progress report, system is being adjusted to meet modules. Concerns about the stabili- 26th IEEE Specialists some specific needs of the Astro- ty of thin-film modules were allayed Conference, 1997.) Power Silicon-Filmª material, and a by this year's trials at the OTF. Two patent application has been made. dual-junction a-Si systems from The interaction between AstroPower United Solar demonstrated extreme- UL-approved and carry a 10-year and NCPV researchers has clarified ly good stability. Five years after sta- warranty. These commercial prod- the needs of the manufacturing envi- bilization, the 1.8-kW system has ucts include PV shingles and metal ronment. After beta-testing and shown less than 5% degradation, roofing with 7.5% stable efficiencies. error analysis, the collaboration with while the 1-kW roofing system has AstroPower will continue by com- shown less than 1% degradation over a 4-year period. Another thin- The Solarex plant is designed to paring the quality of the measure- film system, a dual-junction 1-kW operate at 10-MW capacity. Solarex, a ments at the factory with those of the a-Si system from Solarex, has been business unit of Amoco/Enron Solar, laboratory. More than 300 measure- operating for almost 2 years after stabilization with an average efficiency of 5.8%. And a cadmium telluride system from Solar Cells, Inc., rated at 1 kW, has maintained an average operating efficiency of 7%. Extending PV module lifetimes with better solder bonds and encapsulants

To double the lifetimes of PV modules, the mechanisms that cause degradation must be understood and related to specific manufacturing processes and materials. Such fundamental understanding requires observing modules in actual field operations. Analysis of field-aged modules is required because acceler-

Warren Gretz, NREL/PIX01990 Warren ated-aging tests currently used in Tests of Solar Cells, Inc.'s 1-kW thin-film CdTe array at NREL's Outdoor Test Facility showed module qualification procedures do encouraging stability. not generate all of the degradation

14 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 ¥ Contracts to develop quality, systems engineering and reli- Voids ability programs in manufacturers' facilities ¥ Accelerated testing of new prototypes to identify problems before production ¥ Laboratory support to provide test capabilities that manufacturers do not have

Sandia National Laboratories ¥ Laboratory evaluation pro- This photo shows a microscopic cross-section used to evaluate the quality of solder bonds grams that identify BOS between solder-coated copper ribbons and solar cells. Layers of solder, copper, solder, and cell problems, develop solutions, metalization sandwich the inner silicon cell. Dark sections in the lower solder layer reveal orig- and coordinate industry inating points of potential solder-bond failure (ÒvoidsÓ). approaches mechanisms observed after actual example, this year, NREL identified ¥ Codes and standards support. outdoor exposure. formulations of the pottant material Tackling the difficult problem of iden- ethylene vinyl acetate (EVA) that The BOS laboratory also bench- tifying and minimizing degradation show much greater photothermal sta- marks equipment to provide users mechanisms that reduce performance bility than the two now in commer- with information on how hardware and limit the ultimate lifetime of PV cial use. The new EVAs will be can be used. For example, the modules, the Program teamed with patented soon, and NREL expects to Utility Power Group's grid-tied established module manufacturers, make the formulations available for inverter, developed under PVMaT, material suppliers, system users, PV industry use in FY 1998. Although was tested at 97% efficiency. Florida Solar Energy Center, and the new EVA formulas should Southwest Technology Development improve module performance, In 1997, the two largest U.S. manu- Institute. In 1997, this Module lengthen service life, simplify process- facturers of inverters were awarded Durability Research Cooperative ing procedures, and lower module contracts to improve the reliability of (MDRC) led by Sandia emphasized cost, further work is needed to identi- their products. The Program also two key issues of module durability: fy the ultimate module pottant mate- arranged and supported highly solder-bond processes and their rials for a 30-year service life. accelerated lifetime tests at a com- fatigue lifetime, and the adhesion and mercial test laboratory for four prod- chemical properties of encapsulant- ucts important to PV systems. to-solar-cell interfaces. In addition, Testing the Components the Cooperative has a well-moni- of PV Systems In other work supporting demon- tored, long-term, outdoor exposure stration projects, two large hybrid program for module manufacturers Reliable systems are a requirement inverters were evaluated in the lab- with commercial products that have for the successful implementation of oratory before field installation. already passed today's qualification PV. In electronic systems, reliability When the inverters were connected test standards. Modules provided by is directly related to manufacturing to battery banks, a diesel generator, manufacturers are being installed for and usage experience. In the case of and realistic loads, several problems long-term exposure and analysis in PV balance-of-system (BOS) compo- that could not be identified at the environmental conditions historically nents, manufacturing quantities vary manufacturer's facility were identi- proven to be harsh on module life- from one to, at most, a few thou- fied and corrected. time: a hot and humid site in Florida sand. Thus, there is not adequate (FSEC) and a hot and dry site in experience data to assure reliability. Routine testing of inverters destined southern New Mexico (SWTDI). The The NCPV's national laboratories are for demonstration projects continues. results of these exhaustive analyses providing resources to help bridge A 30-kW Abacus Tri-Mode hybrid should lead to 30-year lifetimes for this experience gap. These resources inverter was evaluated in support of PV modules from U.S. manufacturers. include the following: a Small Business Innovative Research contract. The inverter was New ways to encapsulate PV devices ¥ R&D contracts to provide then installed at the Channel Islands into power-producing devices or min- funds for research that small Naval Facility. A 60-kW AES Static imodules are being explored. For companies cannot afford Power Pack was evaluated for

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 15 PVMaT. This inverter represents a MILLION SOLAR ROOFS V new U.S. manufacturing capability. Testing Supports Million Solar Roofs Batteries are an important and costly component of stand-alone PV sys- The President's Million Solar Roofs Initiative relies on utilities to accept and tems. To test battery reliability and promote the connection of PV systems to the grid. To demonstrate PV's lifetime in PV systems, a laboratory compatibility, Sandia developed a test bed tied to the utility grid so that program is conducted at Sandia and multiple inverters could be evaluated in a realistic, utility-connected config- FSEC. Researchers tested the lifetime uration. The test bed has revealed problems with the way manufacturers of batteries, and they designed and design to prevent "islanding," the continued operation of the system even built a PV hybrid and charge-con- after the grid goes down. In particular, inverters from different manufac- troller system simulator for auto- turers interfered with each other, and islanding times in excess of one mated PV system level testing. In minute were noted for disconnects on the customer side of the distribution addition, they developed and tested transformer. It was observed that islands are not sustained when the island a new hybrid battery charge algo- includes a distribution transformer. As a result, in FY 1998, Sandia will rithm using Digital Solar's micro- coordinate with U.S. inverter manufacturers to develop a single approach processor-based PV hybrid charge to anti-islanding and to modify existing U.S. standards accordingly. This controller. Several publications were addresses a key concern of utilities and is therefore critical to successful- also added to the literature on bat- ly implementing the Million Solar Roofs Initiative. teries: a PV Battery Guide, and PV Battery Cycle Test Results.

16 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 Research and Development Maintaining the U.S. PV industryÕs leadership in technology

esearch continues on a vari- at the national laboratories, col- facturing thin-film a-Si for a variety ety of familiar and novel leagues in universities, the PV of markets and applications. R PV materials. Thin-film industry, and ancillary industries. Manufacturing of a-Si for diverse technology has the potential to The research teams address perfor- applications is the fruition of nearly achieve widespread use in grid- mance, reliability, cost, and manu- two decades of aggressive R&D in connected applications if this facturability. The Thin Film PV thin films, much of it supported in emerging technology can achieve Partnership has been particularly partnership with DOE and NREL performance goals approaching instrumental in identifying critical through the National PV Program. 15%-efficient modules that cost less issues, an important step in scaling Recent support for the successful than $0.50/W and offer a 30-year up successful laboratory results to a commercialization of a-Si thin films lifetime. A number of materials can manufacturing environment. This has come from several sources: the be used to create thin-film solar focus on an agreed-upon set of PVMaT project for manufacturing cells. They include amorphous sili- research priorities is one of the clear- development, the Building Oppor- con (a-Si), cadmium telluride est positive results of teaming, and tunities in the United States for (CdTe), copper indium diselenide the collaborative efforts are paying Photovoltaics (PV:BONUS) project (CIS), and polycrystalline silicon off in bringing thin-film technology for PV shingle product develop- (Si). This year, research continued to its full potential. ment, and the Thin Film PV to support the development of thin Partnership for developing the films from the fundamental to pre- Amorphous silicon advanced double- and triple-junction commercialization stages. cells and modules. As discussed in the Technology The crystalline silicon (c-Si) PV Development section, a-Si has suc- Enhancing the stable efficiency of modules that dominate the market cessfully moved from the laborato- a-Si solar cells was identified as the today have a long track record of ry to the marketplace. Both United highest-priority research area by proven reliability and steady cost Solar and Solarex are now manu- the Amorphous Silicon National reductions resulting from improved manufacturing efficiency and reduced material costs. This year, crystalline silicon efforts with industry focused on advanced manufacturing processes and simplified designs to further lower costs.

In high-efficiency (III-V) solar cells, two major efforts are under way: developing a novel 3-junction concentrator cell and investigating methods for growing high-efficiency III-V devices on low-cost substrates such as glass. Thin Film PV Partnership

The U.S. PV industry is a world leader in thin-film technology. The

Thin Film PV Partnership, like the Gretz, NREL/PIX00652 Warren other R&D partnerships of the PV One of the four a-Si systems tested at NREL that clearly showed a-Si to be a viable technology Program, stimulates collaboration for use in future PV systems. All four small, grid-tied systems showed excellent stability after among researchers and test facilities an initial degradation period (1.5-kW a-Si system by Advanced Photovoltaic Systems).

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 17 R&D Team. The 12.1% stable effi- CdTe thin films. This work is in the 15%. Although this efficiency goal ciency achieved by United Solar laboratory phase at NREL. was not reached, the Program's substantially improved the chances emphasis on low-cost, scalable fab- of a-Si in terms of both its transition The NREL CdTe team focused on rication processes did make signifi- to the marketplace and achieving research addressing critical portions cant progress. Because reducing the longer-term cost per watt reduc- of the device. For example, a new, film thickness or increasing deposi- tions needed to make PV competi- high-performance transparent con- tion rate are the primary means of tive on a global scale. ducting oxide (TCO) was developed increasing manufacturing through- to replace the conventional tin oxide put, NREL focused on evaluating While partnered R&D fuels the layer in CdS/CdTe devices. Made of three deposition techniquesÑsput- steady development of thin-film cadmium stannate, this new TCO tering, close-spaced sublimation, manufacturing, research continues to has several significant advantages and electro-deposition. explore the solid-state physics and over conventional TCOs: it is more other phenomena underlying conductive, more transparent, has a Silicon film advances in technology. For exam- lower surface roughness, is pattern- ple, the Staebler-Wronski effect has able, and is exceptionally stable. The AstroPower fabricated monolithical- long handicapped a-Si thin-film tech- first solar cells produced with this ly integrated silicon-film submod- nology by initially decreasing cell TCO had an efficiency of 14%, and a ules as part of the Thin Film PV efficiency by 20%-40%. A new patent application has been filed. Partnership Program. These sub- model of the Staebler-Wronski effect modules provided the first convinc- was developed by the PV Program's The Institute of Energy Conversion ing demonstration of interconnection first Fulbright scholar, Howard at the University of Delaware is and reasonable efficiency from this Branz, who spent a sabbatical at the working to translate laboratory potentially low-cost silicon-film University of Crete and the Foun- results into an effective engineering approach. The first module had an dations of Research and Technology reactor design for use in large-scale efficiency of 6.25%. The second Hellas (Greece). He created and module manufacturing using CdTe module, which consisted of 36 cells explored the new model, which and CIS materials. The University of connected in series, measured 9.2% explains how the observed light- Delaware's Institute is a U.S. DOE efficient over a larger area (321 cm2). induced metastability in hydrogenat- Center of Excellence for PV Research ed a-Si increases the number of and Development. New PV partnerships atomic defects in the thin-film. The to be formed resulting paper will appear in Solid For the first time, NREL researchers State Communications. NREL is con- succeeded in preparing cross-section A recompetition of the Thin Film PV ducting further theoretical and samples of CIS and CdTe films Partnerships began this year. The experimental studies to determine deposited on glass substrates for new solicitation covers the entire the implications of this new model transmission electron microscopy DOE Thin Film Program, including for a-Si technology. analysis. This development is R&D and Technology Partners in important in determining the chemi- CIS, CdTe, a-Si, film-Si, and Environ- Cadmium telluride cal and structural properties of mental Safety and Health (ES&H). CdS/CdTe interfaces. Letters of interest for the second Thin Large-area CdTe technology saw Film PV Partnership were mailed to initial commercialization this year Copper indium diselenide (CIS) 131 requesters in May 1997, with 63 when Solar Cells, Inc. (SCI) success- proposals received in response. fully demonstrated a low-cost, CIS technology continues to progress high-rate process that produces reli- toward eventual commercialization A significant aspect of this second able modules. The SCI CdTe and by achieving milestones such as the round is that the Electric Power cadmium sulfide deposition process Siemens Solar Industries' 1-kW array Research Institute is providing pri- produces these active semiconduc- that demonstrated 9.2% efficiency vate funding of about $400,000, tor layers in under one minute. this year. adding to the federal investment in Manufacturing costs in full produc- thin-film PV. The DOE portion of tion could be less than $1 per peak In CIS thin-film technology, NREL the funding forms the backbone of watt. Development work is under focused in 1997 on process issues in the partnership and is expected to be way on a contactless, manufactur- scaling up CIS laboratory devices to about $11 to $13 million a year for ing-line method to monitor and larger-area samples with intercon- 3 years. Corporate partners will cost grade the quality of polycrystalline nected submodule efficiencies of share about 45% of the projects.

18 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 PV module recycling substrate. For thin-layer silicon to 100 Award this year from R&D work, the structure of the layer must Magazine. Called PV Optics, the soft- The Thin Film PV Partnership ES&H be designed to enhance optical ware quickly and accurately models team, co-chaired by Brookhaven absorption in the thin layer. the optics of any solar cell or module, National Laboratory and NREL rep- whether crystalline, multicrystalline, resentatives, addressed industry con- Process and device or amorphous. Multijunction designs cerns about potentially toxic waste development can also be modeled. streams containing cadmium and selenium. The team created an SBIR An NREL software tool for perform- Fabricating c-Si solar cells and mod- (Small Business Innovative Research) ing optical modeling of these sophis- ules requires several steps or category for PV recycling. The ticated structures received an R&D processes. Using plasma processing, results not only produced an effective, low-cost recycling technology in advance of large-scale deployment of CdTe and CIGS thin-film modules, but also highlighted a way to recycle silicon cells from modules. Both Solar Cells, Inc., and Drinkard Metalox won first- and second- phase SBIRs to complete this innova- Light tive work. The resulting thin-film process results in recyclable, separat- ed glass, metal, plastic, and metals- containing powders. M72-B147004 Research on Crystalline Silicon

The crystalline silicon program at the Anti-reflection coating national laboratories coordinates three basic tasks: developing next- Semiconductor 1 generation silicon crystal growth methods, increasing the fundamental Semiconductor 2 understanding of crystalline silicon material science, and developing new or improved c-Si devices and process- Semiconductor 3 es. Test facilities at the national laboratories play a key role in all of these projects by verifying the performance Buffer changes that result from the research. Aluminum Next-generation (back-contact/reflector) crystal growth

The silicon substrate for the solar cell requires growing crystals and shap- ing them into slices. Because crystal Glass substrate growth and slicing represents one of the largest costs of c-Si PV modules, researchers have investigated alternative ways to grow crystals that significantly improve throughput, reduce cost, and reduce energy requirements. One way is to deposit PV Optics, a 1997 R&D 100 Award-winning computer software, is a complete, easy-to-use a thin layer of silicon on a low-cost package that accurately models the optics of any solar cell or module.

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 19 researchers at Sandia are optimizing Georgia Tech achieved a record effi- compared to current designs. processing techniques. Initial results ciency of 19.1% on float-zone silicon Preliminary work has demonstrated show a statistically significant and 18.4% on Czochralski (Cz) sili- an 11%-efficient module using back- improvement of half an absolute per- con using RTP. Also, improved contact cells and the one-step centage point in cell efficiency understanding of aluminum-alloyed assembly process. through the optimized use of hydro- junctions led to the fabrication of genation in a commercial production 19.0% and 17.0%-efficient cells using Concentrators: High- line. These researchers have also laboratory and industrial-type investigated an alternative doping processes, respectively. A new Efficiency Concepts technique for reducing back-surface simultaneous boron and phospho- recombination. Aluminum-alloyed rous diffusion process was devel- Research and development sponsored junctions are a popular technique for oped and used to produce 20.3% by DOE, Electric Power Research reducing back-surface recombina- float zone and 19.1% Cz solar cells in Institute, and industry has created a tion, and their performance can be a single furnace step. nascent concentrator industry ready considerably improved by doping to begin large-scale deployment of the aluminum with boron. Researchers at Sandia are examining concentrator PV systems. The PV the entire PV module production Concentrator Alliance was formed at A Crystalline-Silicon Research and process to optimize the cell and a workshop for the PV concentrator Development Cooperative, made up module design concurrently. This industry. This group wrote a position of all major U.S. manufacturers of approach finds that considerable paper for DOE to use in planning crystalline and multicrystalline mod- cost in the module assembly is due future support of the concentrator ules, investigates c-Si device and to the use of solar cells with con- industry. The first problem identified processing issues that are of common tacts on both surfaces. Sandia is by this paperÑthe need to develop interest to the members. therefore developing solar cells with standards for concentratorsÑis both contacts on the back surface already being addressed. Researchers at the Georgia Institute and developing new module assem- of Technology are using rapid ther- bly concepts using back-contact The concentrator industry is in the mal processing (RTP) for crystalline- solar cells. Some preliminary stud- process of changing from a group of silicon solar cells, a process with ies estimate that costs with this new very small companies to a group potentially much greater throughput. approach may be reduced by 25%, with representation of some large companies, including BP Solar and Honda. Future-generation concentrators are likely to use high-efficiency gallium arsenide cells. III-V High-Efficiency Solar Cells

The PV Program is transferring its award-winning, high-efficiency cell technology to suppliers of solar cells for satellites, but this technology could also provide the necessary edge to make cost-effective concentrator systems for use on Earth.

Historically, high-efficiency solar cells have been two-junction GaInP- on-GaAs tandem cells. For example, a record-setting 25.7% (air-mass 0) and 30.2% (air-mass 1.5 direct, Arizona Public Service Co./PIX05675 150 suns) efficient cell won an award A high-concentration, point-focus concentrator is shown here being tested at Arizona Public of excellence in technology transfer Service Company's STAR test facility in Tempe. The arrays, made by Amonix, are two-axis from the Federal Laboratory systems that concentrate incoming solar energy by a factor of 265. Consortium. This tandem solar cell

20 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 ¥ With collaborative support from DOE's OER, a new photochemical device was fabricated and measured at NREL to have 10% solar-to-electric efficiency. This photovoltaic device is based on the dye sensitization of thin nano- crystalline films of titanium oxide.

¥ To further improve the efficiency and stability of CIGS cells, theoreticians performed first-principles calculations leading to several publications on the physics of Ga addition in CIS and its effect on the CIS electronic structure.

¥ Fundamental Raman spec- troscopy studies provided David Parsons, NREL/PIX05278 strong evidence of Te precipi- The III-V metal organic vapor-phase epitaxy system is used to synthesize single-crystal, tates in the microstructure on thin films of a variety of III-V materials, primarily GaInAs and InP-based films for high- CdTe films. This understand- efficiency research cells. ing could lead to improved CdTe devices. uses two cells grown monolithically Fundamental and as one device: the top cell is gallium indium phosphide and the bottom Exploratory Research cell is gallium arsenide. Continued advances in PV technology MILLION SOLAR ROOFS VI depend on improving fundamental The 30.2% efficiency can be NREL Resource understanding of the synthesis and increased by adding more junctions Studies Pinpoint Best processing of the materials from to the two-junction gallium indium which solar cells are made. Million Roofs Locales phosphide/gallium arsenide cell. A Recognizing this national need, DOE's study of related three- and four- Office of Energy Research (OER) The NCPV characterizes solar junction concepts showed that, ide- established the Center of Excellence resources using state-of-the-art ally, an efficiency over 50% is possi- for Synthesis and Processing of measurement systems traceable ble. Practically, it should be possi- Advanced Materials (CSP). to world standards. Electronic ble to reach an efficiency in the data sets and maps depict the 35%-40% range, provided appropri- The most recent project created global distribution of solar ate materials can be identified. within CSP is on High-Efficiency radiation and the quantity and There are a number of materials that PV Projects. In FY 1997, project variability of the resource at may be suitable for the third and members held their first meeting to specific locations. For regions fourth junctions. These materials assess the progress and review vari- with limited sampling data, are known to have band gaps in the ous research activities. The overall researchers are using satellite appropriate ranges and a lattice approach is to effectively couple imagery, meteorological data, constant that can be matched to that existing projects in the PV Program and models to estimate solar of gallium arsenide. The possibility with some 20 relevant OER research radiation. Such studies help to of using these new materials in projects involving national labora- target houses best suited for high-efficiency solar cells is current- tories and universities. participation in the Million ly being investigated, with the goal Solar Roofs Initiative. of reaching a 35%-40% efficiency Among other research results report- within the next 10 years. ed in FY 1997 were:

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 21 Some of today's successful thin-film Measurements and R&D and industry efforts by pro- PV technologies were once innova- viding cost-effective measurement tive ideas. The PV Program works Characterization and characterization service, especially with universities to keep research, and technique develop- these ideas coming in efforts such as The PV Program's Measurements ment. In FY 1997, these laboratories the First Conference on Future- and Characterization laboratories performed more than 40,000 mea- Generation Photovoltaic Technolo- perform thousands of measurements surements on some 15,000 samples gies held in March of 1997. Sessions each year in teaming activities with representing every photovoltaic of the conference addressed the fol- industry, university, research labora- technology. The technique develop- lowing topics: Criteria for New tory, and internal researchers. The ment work addressed measure- PV Concepts; Role of Government, Measurements and Characterization ments specific to PV industry needs Universities and Industries in team within the NCPV includes and the furthering of methods for Developing and Funding New more than 40 experts who provide the manufacturing environment. Ideas; Dye-Sensitized Photochemical analytical support that covers the Cells; Single-Crystal-Like Films on test-and-measurement range from New or improved offerings during Low-Cost Substrates; Innovative atoms through PV arrays. With this past year include a large-area, Concepts; and New Materials and state-of-the-art equipment and facili- continuous solar simulator for evalu- Device Architectures for PV. ties, these laboratories embody cell ating cells and modules under stan- and module performance, electro- dard conditions for flat-plate and con- optical characterization, analytical centrator technologies, a time-of-flight In addition to cutting-edge microscopy, and surface analysis secondary-ion microprobe for high- research in university laboratories, characterization capabilities. resolution determination of impuri- NREL also supports undergraduate ties in cell materials, a large-area laser education. For example, in 1997, These laboratories offer more than scanner for versatile module diagnos- NREL's Historically Black Colleges 40 techniques to measure electrical tics, non-contact spectrometer for and Universities PV Research and optical properties of materials determining the minority-carrier life- Associates Program provided sig- and devices, as well as the chemistry, times and diffusion lengths in semi- nificant PV education to students composition, topography, structure, conductors, a scanning micro-Fourier through seven subcontracts, giving and physical nature of materials, sur- transform infrared system for exam- tuition assistance and summer faces, and interfaces. Through its ining insulators and conductors, and internships at NREL and the Website, this NCPV operation offers a novel near-field scanning optical NASA Lewis Research Center in its collaborators and clients a secure microscope for nanoscale imaging Cleveland, Ohio. Other partici- way to transfer data, thus enhancing and spectroscopic studies of semicon- pants visited Port Elizabeth, South customer interactions and measure- ductors. With this arsenal of analyti- Africa, to learn how Port Elizabeth ment turnaround time. cal capabilities, these laboratories Technikon trains young South offer a complete, one-stop site for Africans to start their own busi- The NCPV maintains technical lead- diagnostic evaluation and correlation nesses installing and maintaining ership in the standard testing of of events from the dimension of sin- PV systems. solar cells and modules, and assists gle atoms to the macroscale.

22 PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 49% 53% 77%

39% 30%

Program 20% Resources 7% he National Center for Research & Photovoltaics (NCPV) was Development 21% Systems Engineering T created last year to improve 49% & Applications the implementation of the National 32% Photovoltaics Program by encouraging the most efficient use of the 2% nation's PV resources. This year the NCPV conducted a series of Technology Industry Z8-B317506Z8-B317506 discussion forums, a workshop, Development and a review to continue building University 19% unity in the national PV communi- Government ty. Specific efforts included an open house at the Solar Forum in April, a high-level industry summit FY 1997 Budget Distribution. Performance and reliability testingÑ in May, a workshop on PV Program PV technologies are tested using Strategic Directions in July, and the ment, and testing of PV compo- outdoor test beds, indoor laborato- Annual Operating Plan task review nents and systems in partnership ries, and field trials. Equipment can encompassing all elements of the with the PV industry. The world- be tested under simulated and actu- DOE PV Program in August. class facilities of the national labo- al outdoor conditions, and under ratories make this possible. varying temperature, humidity, pre- Headquartered at DOE's National cipitation, and radiation levels. Renewable Energy Laboratory, the Material and device developmentÑ NCPV draws on the core expertise Competencies include solid-state Manufacturing and deploymentÑ of NREL and Sandia to guide oper- spectroscopic analysis, experimen- Cost-shared development pro- ations and coordinate support from tation with photoelectrochemical grams evaluate and resolve techni- other resources. These other nation- processes, and the application of cal issues in producing PV compo- al PV resources include Brook- advanced theoretical and computa- nents and systems. NCPV works haven National Laboratory and tional tools for predicting the with large user groups such as DOE's Centers of Excellence in PV behavior of new PV materials. utilities to address technical issues at the Georgia Institute of in deploying PV technologies in Technology, the Institute of Energy Module and system developmentÑ new applications. Conversion at the University of includes laboratories for fabricating Delaware, and the two Regional and evaluating thin-film technolo- Market development and outreachÑ Experiment StationsÑthe Florida gies (a-Si, CdTe, and CIS), c-Si cells Information and outreach activities Solar Energy Center and the and modules, concentrator cells of the staff include assisting those Southwest Technology Develop- and PV arrays, and for developing who buy systems, finding ways to ment Institute. In addition, dozens and testing BOS components such finance PV installations, and ana- of university and industry research as charge controllers and inverters. lyzing technological, economic, partners across the country are and environmental impacts for linked together to function in a Measurement and characterizationÑ specific applications. more unified way. Competencies include analytical microscopy, electro-optical charac- Solar resource characterizationÑ Facilities Available terization, surface and interface State-of-the-art measurement sys- analysis of materials, analysis of tems traceable to world standards Because most companies cannot cell and device operation, computer are used to characterize solar afford large research facilities of modeling of system and component resources. Electronic data sets, maps, their own, the National PV performance, and the development and models are available to quantify Program conducts long-term, high- of special measurement techniques or estimate the distribution of solar risk, high-payoff research, develop- and instruments for U.S. firms. radiation for specific locations.

PHOTOVOLTAIC ENERGY PROGRAM OVERVIEW FY1997 23 Key Contacts U.S. Department of Energy National Renewable Energy Sandia National Laboratories James E. Rannels, Director Laboratory Marjorie Tatro, Manager Office of Photovoltaic and Wind Thomas Surek, Technology Photovoltaic System Components Technologies Manager, Photovoltaics Department, MS-0752 1000 Independence Avenue, SW 1617 Cole Boulevard P.O. Box 5800 Washington, DC 20585 Golden, CO 80401-3393 Albuquerque, NM 87185-0752 Phone: (202) 586-1720 Phone: (303) 384-6471 Phone: (505) 844-3154 Fax: (202) 586-5127 Fax: (303) 384-6530 Fax: (505) 844-6541 e-mail: [email protected] Website: www.nrel.gov/pv Website: www.eren.doe.gov/pv Chris Cameron, Manager Photovoltaic System Applications National Center for Photovoltaics Department, MS-0753 NREL P.O. Box 5800 1617 Cole Boulevard Albuquerque, NM 87185-0753 Golden, CO 80401-3393 Phone: (505) 844-8161 Phone: (303) 384-NCPV Fax: (505) 844-6541 Fax: (303) 384-6481 Website: www.sandia.gov/pv e-mail: [email protected] Website: www.nrel.gov/ncpv

NOTICE: This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service Produced for the by trade name, trademark, manufacturer, or otherwise does not U.S. Department of Energy necessarily constitute or imply its endorsement, recommenda- tion, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.

Printed in the United States of America

Available to DOE and DOE contractors from: Office of Scientific and Technical Information (OSTI) P.O. Box 62 Oak Ridge, TN 37831 1000 Independence Avenue, SW Prices available by calling (615) 576-8401 Washington, DC 20585 Available from: National Technical Information Service by the National Renewable Energy Laboratory, U.S. Department of Commerce 5285 Port Royal Road a DOE national laboratory. Springfield, VA 22161 (703) 487-4650 DOE/GO-10098-539 Information pertaining to the pricing codes can be found in the February 1998 current issue of the following publications which are generally available in most libraries: Government Reports Announcements and Index (GRA and I); Scientific and Technical Abstract Reports (STAR); and publication NTIS-PR-360 available Printed with a renewable-source ink on paper containing at from NTIS at the above address. least 50% wastepaper, including 20% postconsumer waste.