Key Issue Goal 1. Solar cell performance 18% efficiency, 2-mil-thick cell 2. Solar cell cost 0.38 cent per cm2 3. Blanket weight 950 W/kg (430 W/lb) 4. Blanket cost 0.68 cent per cm2 5. Concentration optimization Array: $310/kW, 3 Ib/kW 6. Long life 30-year-life, 6% degradation in 5 years 7. Energy input to process 1-3 year payback 8. High-voltage circuit control 40 kV - 5% loss 9. Operation Automatic assembly and replacement Within each of the key issues there are distinct work areas which will precipitate different degrees of urgency, depending on the specific objective of the effort and its relationship to the final system configuration. Table 22 presents the areas which have been identified. The table is divided into four groups, the first of which includes those areas which require immediate action to maximize the probability of technology readiness at the time of production. The fourth group represents those areas which have the least immediate requirement at the present time, but can still be identified as areas for future work. Investigations carried out without a priority framework in terms of SSPS development objectives are unlikely to result in an effective and^coordinated effort. The relative importance of each of the work areas as they relate to one another, as well as to the system concept, has to be related to the overall SSPS development program. With each of the items listed under the specific work areas is a reference to the key issue number. The objective of the particular work area is also listed and the importance of that effort to the total system is indicated. Following the table, each key factor is described in detail, the research objectives are listed, and the approach to be pursued is indicated. a. Key Issue No. 1 — Solar Cell Performance Improvement Investigations into methods of improving solar cell efficiency are extremely important to the weight and size reductions required for SSPS. The efficiency must be increased from about 14% to 18%, while at the same time reducing the thickness of the devices from about 250 to 50gm. The overall task is expected to require 10 years. The first three or four years will be concerned primarily with theoretical and laboratory studies of potential efficiency-improved techniques and production processes. The approach will be to pursue: 1. The use of low resistivity silicon, 2. Investigations into the theoretical and experimental development of new conversion devices and alternate materials,
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