Improved solar array lifetime Optimized concentration factor. While cost is considered explicitly only in the first category, failure to resolve the other problem areas will tend to increase the overall satellite solar power station (SSPS) costs because of the increased orbital transportation required to place additional, heavier cells in orbit. Furthermore, all these problem areas are highly interrelated in the sense that the resolution of one tends to make the resolution of another more difficult. The requirements, current status, and proposed development procedures to be applied in the resolution of each of the five problem areas are discussed in subsections a through e; subsection f summarizes this presentation. (1) Reduced Solar Cell Cost Current silicon solar cell costs for one kilowatt of generating capacity are about $20,000. This has dropped from an initial value (1958) on the order of $300,000 per kilowatt. Further reductions are projected in accordance with Exhibit 53. Operating spacecraft solar arrays cost about $80,000 per kilowatt and up; the SSPS requirement for economic operation is on the order of $200 per kilowatt or a cost reduction factor of two to three orders of magnitude. For purposes of comparison, it has been noted that from the earliest transistors to the present ones a cost reduction factor of somewhat less than two orders of magnitude has been achieved. However, by using the edge-defined film- fed growth (EFG) method of obtaining silicon crystals a cost of 2.45 2 cents per square inch (0.38 cents/cm ) is projected in the time frame of 2 2 interest. Adding 1.94 cents per in (30 cents/cm ) for laminating the cover and printed circuit substrate gives a total cost of 4.40 cents per 2 2 in (0.68 cents per cm ). Power output, assuming an efficiency approach- . . 2 2 ing 20 percent, is 172 mW/in (26.7 mW/cm ) which gives an overall cost to power ratio of $255 per kilowatt, which is certainly within striking distance of the goal. It should be noted, however, that the ERDA cost goal for terrestrial solar arrays is about $500 per kilowatt for the same time period.
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