Gas turbines and combined cycle
Turbines burning gas directly, alone for peaking or with a steam turbine on the exhaust.
Conversion and use · Conversion devices · No. 97
- Conversion and use
A jet engine paired with a steam turbine makes the best fossil power plant, and data centres have booked them to 2031.
Chart: Illustration: Gas turbines and combined cycle
Where it comes from
Chart: Map of where it comes from
A gas turbine compresses air, burns gas in it and expands the hot gas; a combined cycle uses the 650 C exhaust to raise steam for a second turbine.
Three things to know
- Turbine blades work in gas at about 1,650 C, far above their melting point, kept alive by cooling and ceramic coatings.
- Peakers run only 10 to 15% of hours, so each MWh costs USD 149 to 251, against USD 48 to 109 for combined cycle.
- Jet engines have climbed from about 10% overall efficiency in the late 1940s to about 40% today.
The journey
- 1 Air inCompressor squeezes air hard
- 2 CombustionGas burns at about 1,650 C
- 3 Gas turbineHot gas spins compressor and generator
- 4 Exhaust heatAbout 650 C gas raises steam
- 5 Steam turbineAdds about one third more power