Electric Demand Statistical Model

This section develops the statistical-and-math model for the economical sizing of an electrical peak-shaving generator set (PSG) for a given facility. The fundamental question is: What is the most economical generator-set size—g* in kW—for a given site demand profile? Figure 1 shows a sample record for a facility's electrical demand, which is uniformly distributed between 2000 and 5300 kW. Next, Figure 2 shows the corresponding statistical distributions.

The statistical model of electrical demand is expressed graphically in Figure 2, in terms of two functions:

• The load-duration curve D(t), is the demand as a function of cumulative time t (i.e. the accumulated annual duration t in hrs/year of a given D(t) load in kW), and

• The load frequency distribution f(D) (rectangular shaded area in Figures 1 and 2) is the "uniform" probability density function.

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