Combined Cycle Power Plant Animation

Combining two or more thermodynamic cycles results in improved overall efficiency, reducing fuel costs. In stationary power plants, a widely used combination is a gas turbine (operating by the Brayton cycle) burning natural gas or synthesis gasfrom coal, whose hot exhaust powers a steam power plant (operating by the Rankine cycle). This is called a Combined Cycle Gas Turbine (CCGT) plant, and can achieve a thermal efficiency of around 60%, in contrast to a single cycle steam power plant which is limited to efficiencies of around 35-42%. Many new gas power plants in North America and Europe are of this type. Such an arrangement is also used for marine propulsion, and is called a combined gas and steam (COGAS)plant. Multiple stage turbine or steam cycles are also common.

Reference:

Yahya, S.M. Turbines, compressors and fans. Tata Mc Graw Hill. pp. chapter 5.