of all future revenue requirements" (pwafrr) for a generator operating in the expected manner shall be less than for the other available generators. A calculation of the optimum expansion plan for a utility must include a calculation of how the power plant is likely to be used. The "pawfrr" for each candidate generator can be calculated once the expected usage is determined. When the SPS comes on-line, and is used to meet base load, plants which were base-loaded will be transferred to intermediate load service until the demand growth requires them for base load service again. Cycling of this equipment in load following service can cause expensive maintenance problems and should be terminated as soon as possible. The time required before all of these units can be returned to base load service depends on the power pool characteristics. Two examples of how the duration of this undesirable situation varies with the power pool characteristics are shown in Figure 3.2 and 3.3. Both figures show the peak power demand for a power pool as a function of time; the growth rate is 5% per year in Figure 3.2 and 7% per year in Figure 3.3. As demonstrated in Chapter 2, the SPS should not be placed in small power pools; both power pools have a yearly peak demand of 30 GWe in year zero. The plotted values of the total required installed capacity are taken from the results of Section 2.3. The base load was taken to be 40% of the yearly peak demand; for the power demand described in Equation 2.11, 40% of all generators could be operated without daily cycling for six of the 14 maintenance intervals. The effect on the total generating capacity of adding a 5 GWe generator to the power pools is quite small and, except for the increased margin requirement, disappears within a couple of years. However, adding a 5 GWe generator to a pool has a lasting effect on the base load equipment. If the SPS is added to a 30 GW power pool, 5-8 years (depending on growth rates) must pass before all base load units are returned to
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