Peaking power plant
Peaking power plants, also known as peaker plants, and occasionally just "peakers", are power plants that generally run only when there is a high demand, known as peak demand, for electricity.[1] Because they supply power only occasionally, the power supplied commands a much higher price per kilowatt hour than base load power. Peak load power plants are dispatched in combination with base load power plants, which supply a dependable and consistent amount of electricity, to meet the minimum demand.
Although historically peaking power plants were frequently used in conjunction with coal baseload plants, peaking plants are now used less commonly. Combined cycle gas turbine plants have two or more cycles, the first of which is very similar to a peaking plant, with the second running on the waste heat of the first. That type of plant is often capable of rapidly starting up, albeit at reduced efficiency, and then over some hours transitioning to a more efficient baseload generation mode. Combined cycle plants have similar capital cost per watt to peaking plants, but run for much longer periods, and use less fuel overall, and hence give cheaper electricity.
As of 2020, open cycle gas turbines give an electricity cost of around $151–198/MWh.[2]
Peaker plants have been replaced with battery storage in some places.[3] The New York Power Authority (NYPA) is seeking to replace gas peaker plants with battery storage,[4][5] 142 Tesla Megapacks (providing 100 MW) replaced a gas peaker plant in Ventura County, California[6][7] and in Lessines, Belgium 40 Tesla Megapacks (50 MW) replaced a turbojet generator.[8] Australia's Clean Energy Council found in April 2021 that battery storage can be 30% cheaper than gas peaker plants.[9]
Renewable energy[edit]
As countries trend away from fossil fuel-fired base load plants and towards renewable but intermittent energy sources such as wind and solar, there is a corresponding increase in the need for grid energy storage systems, as renewable alternatives to building more peaking or load following power plants. Another option is broader distribution of generating capacity, through the use of grid interties, such as the WECC Intertie Paths.
Base load power plants[edit]
An economical electrical supply system will also include base load power plants. These generating units will emphasize low incremental fuel cost, but may use a higher capital investment to improve efficiency. For example, a peaking plant might use only a gas turbine, while a base load plant might also add a steam "bottom cycle" to improve the overall plant fuel consumption per unit of electricity produced. Nuclear and coal burning plants generally operate continuously, stopping only for maintenance or unexpected outages.[23]
The low incremental fuel cost of nuclear power plants compared with high capital cost, makes it most economic for them to be used for base load supply. Hydroelectric plants with few restrictions on water supply may be used for base load as their incremental fuel cost is zero. Since a steam cycle power plant may take hours to go from cold standby to full rating, they are not usually used to provide peak load service.[24]
Intermediate load following power plants such as hydroelectric operate between these extremes, curtailing their output on nights and weekends when demand is low. Base load and intermediate plants are used preferentially to meet electrical demand because the lower efficiencies of peaker plants make them more expensive to operate.[25]