UTILITY SYSTEM IMPACTS OF THE SATELLITE POWER SYSTEM Frank R. Goodman, Jr. Electric Power Research Inst., P.O. Box 10412, Palo Alto, CA 94303 The technical requirements and barriers for integration of the satellite power system (SPS) into an electric utility network are discussed. For the purpose of discussion the overall SPS concept is considered to be composed of up to sixty individual 5 GW SPS units. This concept has been selected to reflect the preferred SPS design currently under examination through programs funded primarily by the federal government. This paper focuses on problems that would arise in attempting to interconnect a single 5GW SPS unit with an electric utility system. The potential difficulties with handling large blocks of power produced by an SPS unit are examined in the context of utility planning and operating practices. The features of the earthbound receiving antenna (rectenna) are especially important in examining the utility interconnection problems, but the operational limitations of the space-borne portion of the SPS unit are also a determining factor. The emphasis herein is on technical problems rather than economic problems. The economic ramifications of these problems are addressed only in a relative sense, because uncertainties in the cost of the SPS concept do not permit a reliable estimation of cost figures. The time frame for the SPS scenario discussed in this paper is the first half of the next century. The technical issues identified and examined are generic, rather than specific to a particular utility scenario. However, the size of the utility system or power pool with which an SPS unit is interconnected is an important variable that is taken into account. In this manner the technical treatment should remain valid in spite of uncertainties associated with the technology and characteristics of future utility systems. The foremost technical problem area to be considered herein is utility system operation with an SPS unit interconnected. Before examining specific operating problems, a judgment must be made as to whether or not an SPS unit can be operated as baseload, intermediate, or some other mode of generation. The actual reliability of an SPS unit is clearly unknown at this point in time, but let us assume for the moment that its reliability is very high. In this case the SPS unit might be used as baseload generation together with coal and nuclear power plants which are likely to be the primary forms of baseload generation in the time period of interest. The use of an SPS .unit as baseload generation suffers from one major drawback involving the outage during eclipse periods whose time duration and time of occurrence during the year are exactly predictable. During these periods, a major block of baseload generation (5 GW) is unavailable and must be replaced by reserve units. The exact dispatch strategy will depend on the characteristics and size of the utility or power pool in question. Some possibilities are to use spinning reserve, commit intermediate units, start peaking units, or purchase power through an interarea exchange agreement. In any case a significant component of cost is introduced that does not exist in all conventional baseload generation mix due to increased cycling duty of the backup units and due to the fact that the backup units may be less efficient than baseload units. The argument might be made that this problem is mitigated somewhat by the fact that the eclipse periods occur around local midnight when utility daily demand profiles have historically been near their low point for the day. This argument loses its validity if one envisions a future scenario in which widespread usage of load management programs has flattened out daily demand profiles compared to their historical form. Finally, this problem is compounded in the situation
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