Gas Turbine CHP Generators
These engines use compressed, high velocity air to drive the turbine and in-turn the generator. This air is brought up to pressure and temperature by burning fuel (usually natural gas), where it expands down to the exhaust pressure driving the turbine. It is by driving this shaft coupled to the generator and the compressor, that produces both the compression method and mechanical rotation to drive the altenator for the electricity. Once the hot air has passed through the turbine it is utilised by the heat exchanger.
Combined cycle gas turbine systems
These systems harness the heat from the exhaust from the above Gas Turbine engine and create steam with it. This steam then is used to power an additional steam turbine increasing efficiencies to 55% (average of about 52%). These systems are custom-built and are used in large-scale power generation.