An Evolutionary Path to Satellite Solar Power Systems GEOFFREY A. LANDIS Summary A difficulty with proposals for satellite solar power systems is the absence of a plausable evolutionary pathway to development of systems on the scale required. One possible pathway is discussed, where the required technologies are developed and refined on an incremental scale. The initial stages of the process are development of ground- based photovoltaic power and of beamed power systems for space use. Introduction Starting with Peter Glaser’s initial 1968 proposal [1], many people have discussed use of the satellite solar power system (SPS) as a means of supplying energy to the Earth to replace fossil fuel sources. The recent prominence of the ‘greenhouse effect’ from burning of fossil fuels has again brought alternative energy sources to public attention, and the time is certainly appropriate to reexamine the SPS. The barrier to development of SPS is social, not technological. The initial development cost for a SPS would be enormous: e.g. 102 billion [1977 dollars] for the first 5 GW unit [2, 3] (possibly somewhat lower for some alternative concepts), and the construction time would be long. While it is often argued that production of solar power satellites could eventually be a profit-making commercial venture, the high initial cost and long development time presents a large barrier to commercial involvement. Thus: how can we get there from here? The problem is that possible risks for such a large project are very large, and there is an understandable reluctance to committing enormous amounts of financial resources to a project with uncertain pay-off. The pay-off time is long, and thus fear of technological obsolescence is high. Electricity demand may be inaccurately forecast, or alternative, lower-cost generating technologies may be developed during the time required to develop and construct the system. SPS must overcome the negative experiences with large projects of the nuclear power industry, which invested heavily on long-term, large capacity projects and discovered that projected use did not materialize, while costs and environmental objections ballooned. A significant problem with SPS is that it is inherently a large project. The optimal position is in geosynchronous earth orbit (GEO), far from the user. The physics of antennas mean that a SPS system cannot be made small, since the beam spread at Geoffrey A. Landis, Sverdrup Technology, Inc., NASA Lewis Research Center, 302-1,21000 Brookpark Rd., Cleveland, OH 44135, USA.
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