Electricity from photovoltaic solar cells: Flat-Plate Solar Array Project. 10 years of progress

Abstract

The Flat-Plate Solar Array (FSA) Project, a Government-sponsored photovoltaics project, was initiated in January 1975 (previously named the Low-Cost Silicon Solar Array Project) to stimulate the development of PV systems for widespread use. Its goal then was to develop PV modules with 10% efficiency, a 20-year lifetime, and a selling price of $0.50 per peak watt of generating capacity (1975 dollars). It was recognized that cost reduction of PV solar-cell and module manufacturing was the key achievement needed if PV power systems were to be economically competitive for large-scale terrestrial use. The project was initiated at JPL to meet these goals through R&D of all phases of flat-plate module technology, from solar-cell silicon material refinement through verification of module reliability and performance. The Project sponsored parallel technology efforts with periodic progress reviews and continuing sponsorship of only the most promising options. A module manufacturing cost-analysis capability was developed that permitted cost goal allocations to be made for each module technology, based upon potential for achievement. Economic analyses, done as technical progress was achieved, permitted assessments to be made of each technical option's potential for meeting the goal and of the Project's overall progress toward the national goal. Excellent technical progress across the entire project was accomplished over the years, with growing interest and participation by the private sector. More recently, effective energy conservation practices, a leveling of energy prices, a perception that energy prices are not increasing endlessly, and a change in Government emphasis has altered the picture for photovoltaics. DOE's National Photovoltaics Program was redirected to longer-range efforts that the private sector avoids because of higher risk and longer payoff time. Consistent with these new directions, FSA has been concentrating its efforts on overcoming specific critical technological barriers that inhibit large-scale PV use. These activities require an in-depth, long-range, integrated effort that industry cannot reasonably be expected to undertake alone. This work is being performed by a team that includes universities, industry (which shares the cost), and Government laboratories. This team has worked together successfully for 10 years. An estimate that PV-generated power should cost about $0.15/kWh in the 1990s to be competitive in utility central-station generation plants is the basis for a DOE Five-Year Research Plan. The high cost of PV generating equipment, especially modules, remains the major limitation. Continuing solar-cell and module cost reductions are still the key activities. However, it is now known that, for a utility plant, area-related costs are significant enough that flat-plate module efficiencies must be raised to between 13 and 17% (more energy generated per fixed-area dollar), and module life should be extended to 30 years. It is believed by FSA reseachers that both of these requirements and the corresponding cost reductions are possible, but are achievable only with a dedicated effort. Present FSA activities emphasize high efficiency, long life, reliability, and low cost for solar cells, modules, and arrays. Major Project Accomplishments • Established the basic technologies for all aspects of manufacturing and evaluated nonconcentrating crystalline silicon PV modules and arrays for terrestrial use. • Established a new low-cost, high-purity silicon-feedstock- material refinement process. • Made significant advances in quality and cost reduction of: • Silicon sheet for solar cells. • Higher efficiency solar cells. • Manufacturing processes. • Established PV module/array engineering/design and evaluation knowledge and capabilities. • Established PV module encapsulation systems. • Devised manufacturing and life-cycle cost economic analysis capabilities. • Transferred the above technologies to the private sector by dynamic interactive activities including hundreds of contracts, comprehensive module development and evaluation efforts, 25 Project integration meetings, research forums, presentations at hundreds of technical meetings, and advisory efforts to industry on specific technical problems. • Stimulated the establishment of a commercial PV industry in the United States.

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