industrial power supply system and concentrated power generation systems. Each of these demonstration systems are designed as 3 kW, 60 kW, 200 kW, and 200+ 1000 kW, respectively. Construction of a pilot production line started in October, 1980 and was accomplished by March, 1984. A demonstration experiment will be carried out until March, 1985 (6). In addition to these crystalline Si solar cell pilot plant and demonstration systems, a research and demonstration plant on amorphous Si solar cell technology has been intensely carried out. National Photovoltaic Plan in USA The Department of Energy (DOE) has proposed a Five Year Research Plan from 1984-1988 on photovoltaics (2). The principal research items are materials, collectors and systems. Regarding materials research, single junction thin films such as CdS- like polycrystalline thin film cells, amorphous Si cells and GaAs-like thin film cells, multijunction cells of crystalline or amorphous materials, some innovative materials, low cost high purity Si materials and advanced Si sheet technology are going to be treated. Regarding collector research, flat collector and concentrated collector research will be carried out. Regarding systems research, module reliability, array technology and system experiments have been planned. Regardless of the recession, a lot of research items are going to be developed. SOLAR CELL TECHNOLOGY Mission of Each Technology In Table 1, the expected mission for several kinds of solar cell technologies are summarized. Beyond the first generation of special use, we are thought to lie in the second generation of advanced CZ Si technology, and if we can succeed at the technical innovation by adopting advanced ribbon crystalline technology, then we expect to enter the third generation, where industrial use of photovoltaic energy begins. Furthermore, the fourth generation where grid connection of photovoltaic power generation will be realized may be expected by amorphous Si technology and so on. The prospect of photovoltaic system cost decrease by the DOE was shown in Fig. 1 (3). This prospect demonstrates that the replacement of conventional energy by solar cell may be possible only when system cost is lowered to under $1/Wp. Crystalline Si Solar Cell Technology In order to avoid the slice loss of Si ingot and lower the wafer cost, several kinds of ribbon crystal manufacturing technologies have been developed. Among them, Si ribbon pulling technology using die lies nearest to practice and 100 mm width ribbon crystal has already been obtained. Edge supported pulling is thought to be a more advanced technology. Using ribbon crystal, more than 12% of conversion efficiency has been reported (4).
RkJQdWJsaXNoZXIy MTU5NjU0Mg==