The Conference ended with a summary panel at which Dr. Rashmi Mayur, Director, Urban Development Institute, Bombay, India, presented a special report on “SPS and The Third World” and, with earlier speakers, fielded questions from participants. Robert Piland, using excellent artists’ renderings presented an overall view of SPS. He said the advantages of satellites over surface solar systems were greater insolation, base load capability, minimal damage to collectors from weather and day to night changes, and geographical independence of sunny climates. Engineering problems are chiefly matters of scale rather than of new technologies. A 5x 10 km space structure weighing 100,000 metric tons is a formidable challenge; so is the delivery of 5-10 gigawatts through an independently rotatable transmitter, the design of space freighters (heavy lift launch vehicles), construction depots at low earth orbit and geosynchronous orbit, transfer vehicles, and dormitories for 500 workers, but all these things have been done on a smaller scale. Environmental problems such as rocket emissions and the effect of microwaves on health, the ionosphere, communications, and electronic systems should be studied. At this time, there do not appear to be any show stoppers or overwhelming obstacles. In answer to a question from the audience, Mr. Piland estimated the cost of SPS research and development at approximately $100 billion (comparable to an estimate of $88 billion for synthetics from fossil fuels), and the cost per satellite about $12 billion. Dr. Ruth favored Gallium Arsenide photovoltaic cells over silicon because of their ability to accept higher concentrations of sunlight, longer life, and efficiencies of around 17% as against 13% for silicon. Mr. Dickinson said that link efficiencies in microwave transmission exceeded 80% and that efficiencies from electricity to electricity exceeded 60%. Filtering will be needed to meet radio frequency interference standards. Dr. Beverly reported that laser transmission of electric power has the advantage of requiring smaller receptor sites than microwave transmission (.3 km2 to 2 km2 vs 100-150 km2) but is more sensitive to weather, is massive (27 kg per kw), and inefficient (14.7% for a CO2 laser, 23.4% for a CO laser). Mr. Kotin reported on a comprehensive study of potential rectenna sites undertaken by Kotin and Regan, Inc., and the Rice University Space Solar Power Research Program. Some 59 criteria are being applied to each of 94,000 square grid areas into which the study divides the continental U.S. and coastal waters. Finding sites free from all exclusion variables is difficult. Dr. Moyer, speaking after the luncheon from the point of view of a harassed utility, spoke very emphatically about the need for solar power satellites. Mr. Johnson pointed out that SPS becomes increasingly attractive during inflation and periods of rising fuel costs, and that its cost over 40 years of operation is expected to be less than that of generating power with nuclear or coal plants. Dr. Bachrach pointed out that SPS is now being taken seriously, and that the key issues to be considered are microwave bioeffects, ionosphere impacts, and communications effects, the comparison of SPS impacts and benefits with alternative energy options, and involving affected interest groups in dialogue to achieve consensus. Dr. Mayur discussed the energy problems of the Third World, and described the intense interest in SPS. He suggested India, Argentina, Israel and others might provide research at a bargain price as the Third World’s contribution. The meeting was followed by a short SUNSAT Energy Council Business meeting.
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