A Method for Utilities to Assess the SPS Commercially P.Q. COLLINS AND R. TOMKINS1 SUMMARY Most of the literature on satellite solar power stations (SPS) has considered the combined satellite-rectenna unit as a means of generating continuous power. This paper shows that by considering the rectenna as an independent facility owned and operated by a utility, the utility could use their existing expertise to estimate how much they would be prepared to pay for supplies of microwave power from space, thereby providing clear cost targets for space engineering companies. In addition a range of more flexible and more profitable modes of operation for the SPS can be analysed including provision of daytime power, provision ofpower to a rectenna from more than one satellite, and coordinated operation of a system of several satellites. Introduction For the SPS project, as for any new commercial venture, the concerns of potential customers are of primary importance. The customers for the SPS will be the major electric utilities of the world, and it is therefore essential to consider the SPS from their point of view. The concerns of electric utilities center, in turn, on the needs of their customers, and in particular on the pattern of demand for electricity. This is not constant, but fluctuates according to a number of regular patterns. First there is a daily cycle, whereby for most utilities the daytime level of demand lasts for some 16 hours and then falls by some 50% for the 8 hours of night-time. There is also an annual cycle, which for some utilities shows an average winter demand approximately 100% higher than the summer average; for other utilities the summer average is higher than the winter. There are also weekly cycles and short-term surges at peak demand periods during the day. In order to supply this power, utilities operate electricity generating capacity of different types, some providing continuous "baseload" power, some providing daytime power, and other capacity providing short-term "peak" supplies. The marginal cost per kilowatt-hour from each of these sources is different generally being lowest for baseload power and highest for short-term supplies. Most SPS studies have assumed that, because of the SPS’s high capital cost and the corresponding need to maximise its usage, each satellite would be used to transmit "baseload" power more or less continuously to a single rectenna. However, this assumption overlooks the fact that the value of electric power is not constant but varies during the day and over the year. + The Management School, London, United Kingdom.
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