How cogeneration and combustion turbine power works

Gas turbines have been used for electricity generation for many years. In the past, their use has been generally limited to generating electricity in periods of peak electricity demand. Gas turbines are ideal for this application as they can be started and stopped quickly enabling them to be brought into service as required to meet energy demand peaks.

Gas turbines use the hot gas produced by burning a fuel to drive a turbine. The main components of a gas turbine are an air compressor, several combustors (also called burners) and a turbine.

• Compressor - Compresses the incoming air to high pressure
• Combustion area - Burns the fuel and produces high-pressure, high-velocity gas
• Turbine - Extracts the energy from the high-pressure, high-velocity gas flowing from the combustion chamber

The air compressor compresses the inlet air (raises its pressure). Fuel is mixed with the high pressure air in burners and burnt in special chambers called combustors. The hot pressurized gas coming out of the combustors is at very high temperature (up to 1350° C). This gas then passes through a turbine, giving the turbine energy to spin and do work, such as turn a generator to produce electricity. As the turbine is connected to its compressor, the compressor uses some (about 60%) of the turbine's energy.

Because some of its heat and pressure energy has been transferred to the turbine, the gas is cooler and at a lower pressure when it leaves the turbine. It is then either discharged up a chimney (often called a stack) or is directed to a special type of boiler, called a Heat Recovery Steam Generator (HRSG), where most of the remaining heat energy in the gas is used to produce steam.

Natural Gas, Combined-Cycle

Modern natural gas-fueled facilities produce 90-percent less emissions and are 40-percent more fuel-efficient than older technology, fossil-fueled electric generating facilities.

Cogeneration

Cogeneration, also known as on-site power generation, Combined Heat and Power (CHP), Distributed Generation (DG) and others, is the simultaneous production of electricity and useful 'waste' heat. Any facility that has significant thermal load requirements could be a technical fit for cogeneration.