Extension of learning curves for diode production shown in Figure 43 indicate that one cent per diode cost at high quantity can be projected. Power distribution at about 47 $/kW (2.50 at 5 GW) also is important. The cost factors for real estate and site preparation assuming a generally suitable location has beer- selected are relatively small. 7. SYSTEMS ANALYSIS AND EVALUATION Frequency and power output level are the two prime parameters affecting MPTS performance, given the subsystem and component characteristics discussed above. MPTS cost and efficiency together determine its performance, and these can be combined into a single index of capital cost per kilowatt of ground output power if the power source characteristics are included, so that the cost impact of MPTS inefficiency is accounted for. We must also include the orbital transportation and assembly costs which can be more significant than the equipment factory manufacturing costs. The range of power source and transportation-assembly factors included in the study is shown in Figure 44. The high transportation and assembly cost of 600 $/kg derives from the Shuttle based estimate, and the low figure of 100 $/kg, which is below the transportation factor for the HLLV noted earlier, represents a probable lower extreme for a combined transportation and assembly cost for operational systems with deployment extending into the next century. The power source estimates represent a composite assessment of the range of values appropriate to the ISoO’s and beyond for solar photovoltaic [Glaser, 1974], solar thermal [Woodcock, 1974J and nuclear [williams, 1973] technologies, which have been studied elsewhere in decreasing detail in the order given. Points of reference are the cost goals for ground based solar arrays recommended as realistic for the U.S.A, by a National Science Foundation Study [1974], which are 500 $/kW by 1985 and 200 $/kW in a subsequent development phase. Other reference points are an estimate of 313 $/kW for an orbital silicon photovoltaic array with 2:1 concentration ratio and 18% cell efficiency made in the prior feasibility study [Glaser, 1974] and an updated weight estimate of 1.46 kg/kW made in this MPTS study for a 2:1 concentration ratio and 14% cell efficiency. The high values in Figure 44 represent what are thought to be achievable with high confidence in the required time frame. SPS capital cost as a function of frequency for low and medium level transportation assembly and power source parameters are given in Figures 45 and 46. Plotted are the lowest cost solutions representing tradeoffs between costs of orbital equipment, including transportation and assembly, and the rectenna costs. The latter pertain to an elevation angle of 50 degrees, which would be the case in the Southwest USA. Frequency range has been limited to below 5 GHz because of the increasing susceptibility to rain brownouts above 3 GHz.
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