Reduced availability of the large quantities of water required for traditional wet condenser cooling systems has created a growing market for dry and hybrid cooling for power plants. These technologies significantly reduce overall water consumption, but with large capital cost and heat rate penalties. An important consideration in sizing air-cooled and hybrid condensing systems is the emergence of a spot market for electrical energy. Energy prices can vary over an order of magnitude, and are typically highest during summer conditions. This paper evaluates whether it may be more economical to over-size the cooling system to achieve lower backpressures during the summer and thus generate additional revenue when energy prices peak. A universal methodology for evaluating the impact of cooling system design on operating economics was developed. It consists of a capital cost database for the condensing system, a Gate/Cycle model used to evaluate the effect of cooling parameter selection thermal performance, climatological data to provide representative dry bulb and wet bulb temperatures for typical annualized operating profiles at each plant location, and historical spot market energy pricing for each plant location. Several different design points for the cooling system are examined to determine the optimum selection that maximizes the difference between revenue and cooling system capital cost recovery. A nominal 500 MW coal-burning power plant is used as the study basis to demonstrate the results of this methodology for both northeastern and southwestern sites in the USA.

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