2.1 Types of Cooling Systems

The most common type of CTIAC system has been evaporative cooling using wetted media, due to the relatively low installation and operating costs, although several installed CTIAC systems use mechanical vapor compression refrigerating systems, with and without cool thermal energy storage.

The type of cooling system for a particular combustion turbine installation will depend upon the climate, the airflow rate per kW of increased generation, the value of increased generation capacity and decreased heat rate, load profile and hours of operation, cost of equipment and installation, the turbine degradation due to increased air inlet pressure loss due to cooling coils or welted media, maintenance, and the cost of operation, which includes refrigerating equipment, pumps, water for evaporative cooling, and off-peak power generation for thermal storage. Electric or steam equipment that operates during periods of inlet air cooling represents parasitic loads on the gross turbine generating capacity.

Local conditions should be considered, such as the use of well water for cooling, which, for example, could also be used prior to a plant process. Also, the costs and effects of airborne dust concentrations on evaporative cooling wetted media maintenance, air filter maintenance, cooling coil performance and maintenance, and turbine maintenance should be considered.

The physical processes that occur during air cooling and some of the equipment and systems available to perform inlet air cooling are discussed in the following sections.