can either be the probability that the unit is completely unavailable at an arbitrary time t or it can be the probable fraction of capacity of the equipment that is unavailable 100% of the time, or a combination of both. For the purposes of this calculation, we have assumed that former interpretation. 2.3.2.2 Power Pool Loads Four different power pool loads were considered in this study. To simplify the analyses, load curves were idealized as simple closed-form analytical expressions. For example, the first three varied with time according to the following equations: where P, the maximum yearly demand, was taken to be 30 GWe, 40 GWe and 50 GWe for the three different sized power pools. <f>^ and were chosen so that the SPS eclipses occurred when the load was at the yearly minimum, P/4. The power demand in power pools described in Equation 2.8 varies by a factor of 2 during each day and the daily peak varies by a factor of 2 throughout the year. The absolute peak demand occurs twice a year, assumed to occur once at noon of the longest day of the year and once at noon at the shortest day of the year. The minimum yearly demand also occurs twice a year, assumed to occur at midnight during the autumnal equinox and at midnight during the vernal equinox. These latter time periods coincide with the times when the longest earth eclipses of the SPS occur. The fourth power pool was actually made up of two independent (except for the SPS) 30 MWe power pools each varying with time as shown in Equation 2.8. The variation of this load with time is shown in Equation 2.9.
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