PNL-3234 UC-63 FI GURES TABLES some of the general cell types and, in some cases, several candidate materials for a particular device function are examined. Examples are the homojunction, heterojunction and r~IS structures possible for polycrystalline Si cells and the use of either ITO or Sn0 2 as the window layer of the heterojunction structure. Also selected for study by the workshop participants were the processes listed below for fabrication of materials used in the selected cell types. These processes are examined in this study for materials usage efficiency:

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The research and development described in this document was conducted within the U.S. Deoartment of Energy's (DOE's) Solar Thermal TechnologyProgram. The qoal of the Solar Thermal Technology Program is to advance the engineering and scientific understanding of solar thermal technology and to establish the technoloqv base from which private industry can develop solar thermal power production options for introduction into the competitive energy market.Solar thermal technology concentrates solar radiation by means of tracking mirrors or lenses onto a receiver where the solar energy is absorbed as heat and converte~ into electricity or incorporated into products as process heat. The two primary solar thermal technoloqies, central receivers and distributed receivers, emoloy various Point and line-focus optics to concentrate sunlight. Current cental receiver systems use fields of heliostats (two-axis tracking mirrors) to focus the sun's radiant energy onto a single tower-mounted receiver. Parabolic dishes up to 17 meters in diameter track the sun in two axes and use mirrors or Fresnel lenses to focus radiant energy onto a receiver. Troughs and bowls are line-focus tracking reflectors that concentrate sunliqht onto receiver tubes along their focal lines. Concentratinq collector modules can be used alone or in a multimodule system. The concentrated radiant enerqy absorbed by the solar thermal receiver is transported to the convP.rsion process by a circulating working fluirl. Receiver temperatures range from 100°C in low-temperature trouqhs to over 1500°C in dish and central rP.ceiver systems.The Solar Thermal Technology Proqram is directing efforts to advance and improve Promisinq system concepts throuqh the research and development of solar thermal materials, components, and subsystems, and the testing and oerformance evaluation of subsystems and systems. These efforts are carried out through the technical direction of DOE anrl its network of national laboratories, which work with private industry. Toqether, they have established a comprehensive, goal-directed proqram to improve performance and provide technically oroven options for eventual incorporation into the nation's energy suooly. ; ; iTo be successful in contributing to an adequate national energy supply at reasonable cost, solar thermal enerqy must ev~ntually be economically competitive with a variety of other energy sources. Components and system-level oerformance tarqets have been developed as quantitative program goals. The performance targets are used in planning research and development activities, measurinq progress, assessinq alternative technology options, and developing ootimal components. These targets will be pursued vigorously to insure a successful program.The objective of this report is to provide information on the commercial developments of wind energy conversion systems (WECS) and photovoltaics (PV) in the U.S. This particular study was conducted because it was felt that the commercial success of these two nonthermal solar technogies has sever...

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