Base load power plant

The baseload (also base load) on a grid is the minimum level of demand on an electrical grid over a span of time, for example, one week. This demand can be met by unvarying power plants, dispatchable generation, or by a collection of smaller intermittent energy sources, depending on which approach has the best mix of low cost, availability and high reliability in any particular market. The remainder of demand, varying throughout a day, is met by dispatchable generation, load following power plants, and peaking power plants, which can be turned up or down quickly, operating reserve, demand response and energy storage. The baseload (also base load) on a grid is the minimum level of demand on an electrical grid over a span of time, for example, one week. This demand can be met by unvarying power plants, dispatchable generation, or by a collection of smaller intermittent energy sources, depending on which approach has the best mix of low cost, availability and high reliability in any particular market. The remainder of demand, varying throughout a day, is met by dispatchable generation, load following power plants, and peaking power plants, which can be turned up or down quickly, operating reserve, demand response and energy storage. Power plants that do not change their power output quickly, such as large coal or nuclear plants, are generally called baseload power plants. Grid operators take long and short term bids to provide electricity over various time periods and balance supply and demand continuously. The detailed adjustments are known as the unit commitment problem in electrical power production. While historically large power grids used unvarying power plants to meet the base load, there is no specific technical requirement for this to be so. The base load can equally well be met by the appropriate quantity of intermittent power sources and dispatchable generation. Unvarying power plants can be coal, nuclear, combined cycle plants, which may take several days to start up and shut down, hydroelectric, geothermal, biogas, biomass, solar thermal with storage and ocean thermal energy conversion. Supply interruptions can affect all plants from breakdowns, and also hydroelectric plants from droughts, coal plants if their coal stockpiles freeze, and gas plants from pipeline leaks and closures. The desirable attribute of dispatchability applies to some gas plants, wind (through blade pitch) and hydroelectricity. Grid operators also use curtailment to shut plants out of the grid when their energy is not needed. There are 195,000 megawatts of grid storage installed world-wide; 94% is pumped-storage hydroelectricity; 2% is in batteries. Pumped storage uses cheap power at times of low demand, usually night, to pump water from a lower reservoir to an upper reservoir, then lets it drop back through turbines during peak demand times, usually in the day. Availability of solar power in peak hours of the day can reduce the need for storage. The biggest storage facility in the world is on the Virginia-West Virginia border, with 50% more capacity than the Hoover Dam. Grid operators solicit bids to find the cheapest sources of electricity over short and long term buying periods.