The SSPS is of worldwide interest. Thus, whatever we shall decide to do, we have to realize that many other nations will ask questions. What we have attempted to do so far is to assess the environmental impacts and understand some of the socioeconomic questions which will need to be answered. If we examine the capital costs of the SSPS, we find that the total cost of $7.6 billion for a 5,000-megawatt satellite can be broken down into various of its components..The major cost element is for space transportation. However, even with transportation, we project the unit cost to be $1,500 per kilowatt, which is the competitive range of most other generating systems in the time frame of the 1990's when this satellite would be operational. A utility could supply SSPS produced power at the bus bar for 27 mills per kilowatt-hour, if we assume a 30-year operational life. We actually expect the satellites to last longer than 30 years. We have compared these costs in mills per kilowatt-hours—and here we are using 1974 dollars—'to the cost of coal, oil and terrestrial solar systems. Nuclear power is not shown, since it is hard to project costs which have recently increased at such rapid rates. We have assumed for example, that coal will increase in noninflationary terms, either at 2.6 or 5 percent yearly increments from 1995 to 2025 while oil will increase at an increment of 0.7 percent with a 5 percent yearly increment being outside the range of economic interest. I do not believe that oil for power-generating purposes will be significant much beyond the turn of the century. Thus we project that at 27 mills per kilowatt-hour, the SSPS can be competitive with coal-burning plants, and it certainly is competitive with terrestrial solar plants. The solar system cost projects, ranging from 35 to 65 mills per kilowatt-hour, have been produced by JPL in a study carried out for NASA. We have compared the capital costs of terrestrial solar plants, using photovoltaic conversion, with the costs of the SSPS for a number of solar cell efficiencies—48 percent and 10 percent—with and without energy storage. In all cases, we find that the cost of power produced by the satellite tends to be very competitive—in fact, lower when the cost of the solar cell per square meter is the basis for the comparison. The reason we are not now using solar cells on earth is, of course, their high cost, which is expected to be reduced as the national photovoltaics conversion program begins to achieve lower costs. The SSPS development program can be divided into three phases. The first phase is concerned with development of the technology and its verification—for example, in a space station or other means that could test the various functions of the components. These tests should be completed in the mid-1980's, allowing us then to take the next step to construct a prototype SSPS so that we can then be assured how such a device would operate on a reasonably large scale, and be ready to proceed with commercial SSPS construction. As far as the near-term aspects are concerned, we have identified a development program over the next 4 or 5 years to improve our knowledge of photovoltaic conversion, particularly the fabrication of solar cells into large arrays, the analysis of large structures, the techniques for manufacturing and assembling components in orbit, system for providing stability and control, the generation and transmission of
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