How does a combined-cycle power plant work?

The process of transforming natural gas into electricity begins when air from outside is compressed at high pressure in the compressor. From there, it is conducted to the combustion chamber where it is mixed with the fuel. The combustion gases then pass through the gas turbine where they expand. This causes the heat energy to be transformed into mechanical energy, transmitting it to the shaft.

Subsequently, the gases leaving the gas turbine are fed to a heat recovery boiler to produce steam. From this point on, the conventional water-steam cycle occurs, in which the steam turns the steam turbine. At the exit of the turbine the steam condenses (turning back into water) and returns to the boiler to start a new steam production cycle. Usually, the gas turbine and the steam turbine are coupled to the same shaft, so that they jointly drive the same electric generator.

Source: Fundación ENDESA