Which statement best describes 'combined cycle' power plants?

'Combined cycle' power plants are designed to optimize efficiency by combining two types of turbines: gas and steam turbines. In this setup, the gas turbine generates electricity and produces hot exhaust gases. These exhaust gases are then routed to a steam generator, where they create steam that drives a steam turbine. This process allows for the capture and utilization of waste heat that would otherwise be lost in a conventional gas turbine system.

This dual approach significantly enhances the overall efficiency of power generation compared to using only one type of turbine. In essence, the combined cycle harnesses the strengths of both gas and steam turbines, maximizing energy output from the same fuel input. This is particularly beneficial in reducing fuel consumption and lowering emissions, making combined cycle power plants an attractive option in power generation systems.

This understanding clarifies that the other options do not accurately depict the nature of combined cycle plants, as they either limit the plant's operation to one type of turbine, or incorrectly suggest that turbines are not involved at all.