Which type of boiler is an electric power generation system that uses both a gas turbine-driven generator and a steam-driven generator?

Which type of boiler is an electric power generation system that uses both a gas turbine-driven generator and a steam-driven generator?

• A. Single-cycle
• B. Cogeneration
• C. Double-cycle
• D. Combined-cycle

Answer: (D)

The idea being tested is that combining two thermodynamic cycles in one plant yields more efficient power generation. In a combined-cycle setup, a gas turbine burns fuel to drive a generator and produce electricity. Instead of letting the hot exhaust go to waste, that exhaust is sent through a heat recovery steam generator to make high-pressure steam. That steam then powers a second turbine connected to another generator. By harvesting the exhaust heat to drive a steam turbine, the plant gets extra electricity from the same fuel, boosting overall efficiency far beyond what a single-cycle gas turbine could achieve. Cogeneration also involves heat recovery, but the specific configuration described—a gas turbine plus a steam-driven generator for electricity—points to the combined-cycle arrangement.

The idea being tested is that combining two thermodynamic cycles in one plant yields more efficient power generation. In a combined-cycle setup, a gas turbine burns fuel to drive a generator and produce electricity. Instead of letting the hot exhaust go to waste, that exhaust is sent through a heat recovery steam generator to make high-pressure steam. That steam then powers a second turbine connected to another generator. By harvesting the exhaust heat to drive a steam turbine, the plant gets extra electricity from the same fuel, boosting overall efficiency far beyond what a single-cycle gas turbine could achieve. Cogeneration also involves heat recovery, but the specific configuration described—a gas turbine plus a steam-driven generator for electricity—points to the combined-cycle arrangement.