How Combined Cycle Works

Inner workings of a combined cycle power plant

Combined cycle power plants feature gas and steam turbines. The gas turbine generates electricity using natural gas fuel, while the steam turbine generates electricity using waste heat from the gas turbine. The process is extremely efficient since exhaust heat is re-used that would otherwise be lost through the exhaust stack.

A gas turbine compresses air and mixes it with fuel. The fuel is burned and the resultant hot air-fuel mixture is expanded through turbine blades, making them spin about a shaft. The spinning turbine drives a generator that converts the spinning energy into electricity.

  • Fuel is burned in a combustor
  • The resulting energy in the gas turbine turns the generator drive shaft
  • Exhaust heat from the gas turbine is sent to a heat recovery steam generator (HRSG)
  • The HRSG creates steam using the gas turbine exhaust heat and delivers it to the steam turbine
  • The steam turbine delivers additional energy to the generator drive shaft
  • The generator converts the energy into electricity

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