What is Combined Cycle Generation?
A combined cycle plant uses both a gas turbine and a steam turbine to produce electricity. Electricity is generated first in the gas turbine cycle using natural gas fuel and then the steam turbine cycle.
Cycle 1: The Gas Turbine
In the gas turbine cycle, air is compressed then heated through the combustion of natural gas. The expansion of gases turns the turbine, which drives a generator, producing electricity.
Cycle 2: The Steam Turbine
Heat created in the first cycle (that would otherwise be wasted) is recovered to produce steam. This steam is provided to a steam turbine. Similar to the gas turbine cycle, the expansion of steam turns a steam turbine which drives a generator, producing electricity.
Adding the steam cycle to the gas turbine cycle increases the amount of electricity generated from a given amount of natural gas. Subsequently, there is greater fuel efficiency and fewer emissions produced per unit of electricity generated than would be produced by the gas turbine on its own.