Power & energy

Combined-cycle power plant

Power generation · Brayton + Rankine

How can a power station get a second helping of electricity from the same fuel?

A combined-cycle plant first burns natural gas in a gas turbine, a machine like a jet engine, which spins a generator. Its exhaust is still hotter than a pizza oven, so instead of wasting it the plant uses it to boil water, and that steam spins a second turbine. Together they turn about 60% of the fuel’s energy into electricity, far more than older power stations manage.

A combined-cycle plant puts a steam (Rankine) cycle underneath a gas-turbine (Brayton) cycle, using the gas turbine’s hot exhaust to raise steam in a heat-recovery steam generator. Because the second cycle needs no extra fuel, modern plants convert about 60 % of the fuel energy into electricity — the highest of any large thermal power station.

Key facts

Net efficiency (new H class)

≈ 60–64 % (LHV)

Typical unit size

≈ 400–1300 MW per block

Output split

≈ 2/3 gas turbine, 1/3 steam turbine

GT exhaust / stack temperature

≈ 600–650 °C / ≈ 80–100 °C

HP steam conditions

≈ 16–18 MPa, ≈ 585–600 °C (with reheat)

CO₂ intensity (natural gas)

≈ 330–370 kg per MWh

Parts you can explore (15)

• Compressor
• Combustors
• Gas turbine
• Generator
• Steam turbine
• Condenser
• HRSG casing
• Superheaters
• Evaporators
• Economisers
• Steam drums
• Stack
• Steam piping
• Gas flow
• Steam & water flow

In the 3D model

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