available. SPS energy ratios were found to be marginally favorable with respect to other energy sources when the system boundaries were drawn so as to exclude fuel ("fuel" in this case being solar radiation). When fuel is included, the SPS energy ratios are very favorable. There are, however, large uncertainties associated with the SPS design and with the energy analysis techniques themselves. Because of these uncertainties, it was considered unwarranted to conduct additional studies in this area for the final assessment. If further studies should be undertaken in the future, it is recommended that such analysis employ a hybrid methodology consisting of: (1) process analysis to identify key initial energy requirements, and, (2) input-output analysis to account for indirect energies. A breakdown of material requirements by system component would facilitate the use of materials energy intensity data and better reveal sensitivity to data uncertainties in the energy analysis. Basically, the energy resource is not considered to be a problem. However, the high initial energy investments of a capital-intensive SPS program make for a long pay-off period. The dynamic consequence of the program mean that, though each individual plant may have a positive energy ratio, initial energy requirements create a protracted energy drain during the initial years of construction and operation. The approach to the land-use problem, both in the preliminary and final assessments, has been to identify those areas of the contiguous United States that cannot be used for siting rectennas. The remaining areas are then "eligible," pending further analysis. It has also been assumed in both assessments that the required land must be near enough to load centers to represent a reasonable solution to the utility integration problem. Thus, sufficient land is only one requirement; suitably located land is another. The preliminary assessment identified areas of the U.S. that were potentially eligible for SPS rectenna sites. A problem arose, however, in matching potentially eligible areas to power demand areas. The North Central and Northeast regions of the U.S. have the smallest potential area for rectenna siting relative to apparent need. Unfortunately, the uncertainties in the analysis were such that little confidence could be placed in these results. Therefore, a follow-on study was undertaken that refined the data base of exclusion criteria (populated areas, national parks, etc.) and used a finer mapping grid in the eligible area analysis. The preliminary assessment used a 26 X 26 kilometer grid size; the final assessment used the USCG 7.5 minute quad maps which are roughly 13 kilometers on a side. Validation of both eligible and ineligible areas was incorporated in the analysis and sensitivity studies were conducted. In a related but independent analysis, a prototype environmental impact statement was prepared for a specific, although hypothetical rectenna site. The primary conclusions of the siting studies are that there are suitably located areas for rectenna sites throughout the U.S. Actual acquisition of the specific sites promises to be a difficult problem at best, and location of sites in some of these areas will exact a fairly heavy cost penalty to either prepare the site or modify the rectenna design. The most critical design variable is topography. Sites can be placed in different terrain but only at a substantial cost penalty incurred in site preparation. Migratory bird flyways could have a devastating impact on eligible areas, depending on the (currently unknown) impact of SPS microwave radiation on birds. Sea sites are
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