Although these considerations might suggest that waste heat impacts from photovoltaic systems might be significant, one must look at the potential size of such a facility. A typical application of the technology might supply the electrical energy needs for a town of about 10,000. This would require about 0.25 km^ of collector area representing a maximum system capacity of about 22 MWe.®® somewhat larger system (88 MWe) would require 0.9-1.7 km 2 of collector area.^® Generic studies have been completed for large-scale applications (100 MW and 1,500 MW); however, the actual utilization of systems of this size will depend largely on the experience with smaller facilities.®^ It is apparent that large-scale photovoltaic facilities will be considerably smaller than a rectenna. It is thus anticipated that impacts from photovoltaic systems will be minimal and local in nature. Small temperature perturbations over the collector surfaces may occur, particularly during calm weather. Other impacts on local climate will include a change in surface roughness (due to the collector surface), producing a change in the wind structure in the atmospheric boundary layer. Additionally, changes in evapotranspiration at the surface will occur because of the collector. These changes should produce negligible changes in the climate because of the relatively small surface area being disturbed. 3.4.2 Secondary Impacts Although there are no normal emissions of air pollutants during operation of photovoltaic systems, emissions occur during the manufacture of photovoltaic cells. A modest amount of particulates will be emitted from aluminum and concrete production for the cell arrays.®5 Production of silicon or cadmium photovoltaic cells will entail some emissions of particulates, S0x, and N0x. However, on a per-capacity basis,®® all of these emissions are small in comparison to those from coal-fired electrical generating systems. 3.5 FUSION SYSTEMS Estimates of fusion power development indicate that precommercial demonstration reactors will not be built until the 21st century and that commercial reactors will not exist until the year 2030, at earliest.®® It is
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