Energy from Natural Gas and Oil
How do combustion turbines work?
Our combustion turbine units can supplement power to the grid quickly when electricity demands are highest. The combustion turbine operates on the Brayton Cycle in which air is compressed in a compressor, fuel is fired in a combustor, power is generated from a turbine and waste heat is exhausted from a stack. The mechanical power developed in the turbine is converted to electrical energy in a generator, as shown below.
Duke Energy operates a system of generating plants that operate on natural gas and/or fuel oil (diesel), including simple cycle and combined cycle combustion turbines. These units are extremely flexible and reliable.
Many of our combustion turbine units are used to supplement power supply during peak period demands when electricity use is highest. These combustion turbine units start quickly and can be used for a short period of time to meet temporary energy demands. However, they are also capable of operating for extended periods and our combined cycle units are some of the most reliable and lowest cost dispatchable generators.
A combined cycle generating plant uses combustion turbines, heat recovery steam generators and steam turbines to efficiently convert fuel to electricity. The fuel is burned in the combustion turbines to produce mechanical power that is converted to electric power by the generators. For increased efficiency, the hot exhaust gases resulting from this combustion process are routed through the boiler to produce steam which is then converted to additional electricity via a steam turbine generator. Combined-cycle units offer greater efficiency than traditional combustion turbines or steam turbines. Their operational flexibility is vital in supporting load demand.
Combustion turbines can operate on several different fuels, including natural gas and liquid fuel (or oil). While natural gas is the primary fuel source for most of our units, many are capable of operating on oil as either the primary or secondary fuel source to produce electricity. In addition, most combustion turbines are capable of operating partially on hydrogen gas.
Generation from a combustion turbine can develop up to 300,000 horsepower.
A combustion turbine is made up of several stages of compressor blades, a ring of combustors and 3-4 stages of turbine blades that spin at 3,600 rotations per minute.
Two-thirds of the generated power rotates the compressor and turbine while the rest spins the generator to produce electricity.