Simple cycle gas plants are a type of natural gas power plant which operate by propelling hot gas through a turbine, in order to generate electricity. They differ from combined cycle gas plants because their waste heat is not supplied to another external heat engine, so they are only used to meet peaking power needs on the electrical grid. These turbines have a high specific power, which means that the power they provide for how massive they are is relatively high.
Baseload power is supplied to the grid from various power plants like coal or nuclear which meet the minimum electricity needs, and peaking power plants such as simple cycle gas plants can respond to the fluctuating demands for electricity. To do so, simple cycle plants have great operational flexibility which means they can be started up quickly in order to meet these needs. However this comes at a lower efficiency compared to combined cycle plants, as they make less use of the energy in the fuel they are using. The efficiency of these plants is around 35%.
The relatively lower efficiency and function to only provide peaking power, simple cycle power plants are not run for very long throughout the year. This gives them a very low capacity factor, which means that they are, on average, not running very close to their maximum output. At most, these plants are typically only run for a few hours per day.
To read more about how these turbines create useful energy, visit the gas turbine page.