An arrangement of a steam system and a gas turbine, working as a single installation, is called a

• A. A combined cycle plant
• B. A cogeneration system
• C. A once-through system
• D. A two-stage system

Answer: (A)

The arrangement is called a combined cycle plant. It uses a gas turbine to generate electricity, and its hot exhaust is fed to a heat recovery steam generator that makes steam to drive a steam turbine. Running the gas turbine and the steam cycle together inside one installation boosts overall efficiency by reusing waste heat rather than discarding it. Cogeneration also produces heat and power, but the specific pairing of a gas turbine with a steam cycle in a single installation is the defining feature of a combined cycle plant. The other terms describe different steam-generation or turbine configurations and don’t highlight the integration of the gas turbine with a steam cycle.