All electric utilities are faced with the problem of optimizing the addition of new generating units to provide adequate capacity as predicted by the load-growth forecasts. Smaller capacity additions permit closer matching of the load-growth curve, but larger units have a lower capital cost per kilowatt. The conflict between installing small generating units at a high capital cost per kilowatt, or larger units at a lower kilowatt cost, but resulting in excess system capacity, is particularly acute for the small and medium-size electric utilities. For these systems, the combined steam-turbine gas-turbine fired-exhaust cycle may be of special interest. This cycle permits a “building-block” approach; i.e., the gas turbine can be added to a new or an existing steam station at an optimum time, allowing deferment of the next steam-turbine installation. This building-block concept permits closer matching of the load-growth curve with all the advantages of the combined plant as an additional benefit.

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