Gas turbine exhaust heats a steam cycle to reach over 55% efficiency.
A gas turbine's exhaust (500–600 °C) heats a heat-recovery steam generator driving a steam turbine. Overall efficiency 55–62%, the highest of fossil technologies. Fast start and lower CO₂ per MWh than coal.
A 400 MW combined cycle plant burns less gas per MWh than separate cycles.
Combined cycles pair a gas turbine with a steam cycle, which is why modern gas power plants reach very high efficiency.
Gas turbine exhaust heats a steam cycle to reach over 55% efficiency.
Combined cycles pair a gas turbine with a steam cycle, which is why modern gas power plants reach very high efficiency.
The gas turbine rejects heat at high temperature, which the steam cycle uses. This reduces the waste heat that is lost to the environment.
A boiler that uses exhaust gas from the gas turbine to generate steam for the steam turbine.
Typical applications include designing a gas-fired plant that recovers heat from the turbine exhaust, estimating the output of a combined cycle from its gas turbine and steam turbine and upgrading an old steam plant by adding a gas turbine in front of its boiler.
Study "Reheat and regeneration" first (topic 34 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
Topping and bottoming cycles. HRSG pinch point. Cogeneration option.
A 400 MW combined cycle plant burns less gas per MWh than separate cycles.
The next topic is "Vapour compression refrigeration", which builds directly on this one.
It is classed as Beginner in Thermodynamics & Fluids (topic 35 of 105). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.