Combined-Cycle Generation. Combined-cycle generation is a configuration using both gas turbines and

steam generators. In a combined-cycle gas turbine (CCGT), the hot exhaust gases of a gas turbine are used to provide all, or a portion of, the heat source for the boiler, which produces steam for the steam generator turbine. This combination increases the thermal efficiency over a coal- or oil- fueled steam

generator. The system has an efficiency of about 54 percent, and the fuel consumption is approximately 25 percent lower. Combined-cycle systems may have multiple gas turbines driving one steam turbine.