Fig. 10. Fraction of transmitted laser power absorbed or scattered by each atmospheric layer (Midlatitude Summer Model). nitude of this thermal source depends on the power rating of the plant and its thermodynamic or laser-energy conversion efficiency. Possibility for Global Climatic Change. “Waste” heat is an inevitable consequence of the utilization of most energy sources, and it dissipates in the atmosphere, surface layers of the earth, and surface waters. An estimate of the level at which waste-heat disposal at or near the earth’s surface might induce global climatic alteration is not difficult to perform. The average rate of absorption of solar energy is about 250 W/m2, and simple climatic models suggest that thermal polution sources which increase this value by about 1 percent may produce serious consequences (52,53). Based on the present laser-SPS design, it would require a proliferation of 200,000 to 400,000 complete satellites to induce this magnitude of waste heat. The quoted range accounts for the possible range in various system powers and efficiencies. Meteorological Implications. Direct laser-beam heating of the troposphere is likely to induce local meteorological changes. The effects of heat input from a distributed source (see Figures 10 and 11) will differ from effects typically found near conventional fossil-fuel electric power plants. The nature of the distributed source suggests that significant updrafts will exist in the lower troposphere above the receptor site. Because of prevailing winds and the Coriolis effect, the ensuing convective air movement may assume a helical or vortex flow. The turbulence associated with this effect will probably be severe in the lower troposphere, especially for multiple-beam transmission to a common site. There is one outstanding positive benefit to this effect — the strong convective updraft will
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