Generator Cost Description

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The cost associated with operating a generator varies according to the output of the generator, with the general rule that getting more power out of a generator costs more. In Simulator, there are two options for modeling generator cost. The first employs the common cubic relationship

 Ci(Pgi)  = IndFixedCost + ( ai + bi Pgi + ci (Pgi)2 + di (Pgi)3 ) * fuel cost $/Hour

where Pgi is the output of the generator at bus i in MW. IndFixedCost is the fuel cost independent fixed cost, and therefore is not multiplied by the fuel cost. The value ai is the fuel cost dependent fixed cost, and is therefore multiplied by the fuel cost. The values bi, ci, and di are used to model the generator's input-output (I/O) curve. The I/O curve specifies the relationship between how much heat must be input to the generator (expressed in MBtu per hour) and its resulting MW output. Normally, the cubic coefficients remain constant for a generator. The last term in the equation is the fuel cost, expressed in $/MBtu. This value varies depending on the fuel used in a generator. Typical values would be $ 1.25/MBtu for coal and $ 2/Mbtu for natural gas. The resultant equation is known as the fuel-cost curve. The value of the fixed costs, bi, ci, di, and fuel cost can be viewed and modified using the Generator Information Dialog.

Simulator can also model generator costs using a piecewise linear model consisting of pairs of MW output and incremental cost ($/MWhr) of generation, along with a fixed cost. These piecewise linear curves must be convex curves, meaning the marginal cost of the current MW break point must be higher than the previous MW break point.

Such curves can be defined using the Generator Information Dialog or by loading data from generator cost data files.