An extremely conservative projection of space thin-film solar cell technology would be a 5% efficient thin-film cell fabricated on a 25 micron thick Kapton substrate. This yields a photovoltaic blanket specific power of 1.7 kW/kg. An optimistic projection might be a 15% thin-film cell on a 7 micron thick Kapton substrate, leading to a photovoltaic blanket specific power of 15 kW/kg. These numbers compare favorably to current state of the art spacecraft solar blankets, e.g., 67 W/kg at the array level for the flight-tested SAFE array, and 130 W/kg at the array level for the experimental APS A array using thin silicon solar cells. Values for the photovoltaic blanket alone without the array structure are about twice as high. Thin film cells have other desirable features for space applications. In addition to low mass, thin-film photovoltaics are also projected to have considerably lower costs. Materials cost is reduced due to the small amount of materials required; the cost of labor and assembly is reduced by the fact that large-area, integrated assemblies are produced directly on the substrate sheet. Preliminary results also indicate thin-film solar cells may be inherently radiation tolerant, and not require a glass cover for radiation protection [12]. They are highly tolerant of small damage areas, such as damage due to micrometeorite or debris impact. For currently designed space power systems, the photovoltaic blanket weight is only about a quarter of the total power system mass, as shown in table 2. The array structure and the power management and distribution (PMAD) system account for three-quarters of the power system mass. This provides a powerful incentive to reduce or eliminate the PMAD by integrating the loads (RF elements) directly in the solar array, and to design new array structures to take advantage of the ultralight blankets. The full utilization of the thin-film cell’s low mass potential is a goal of the proposed integrated design. Microwave Electronics Use of thin-film solar cells will significantly reduce the satellite mass only if the mass required for the power management and the microwave beaming system can
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