Minimum level of demand on an electrical grid over a span of time
Some early nuclear plants, such as the VVER-440 (pictured atMetsamor) were designed for baseload operation[1]
Thebase load[2] (alsobaseload) is the minimum level of demand on anelectrical grid over a span of time, for example, one week. This demand can be met by unvarying power plants[3] ordispatchable generation,[4] depending on which approach has the best mix of cost, availability and reliability in any particular market. The remainder of demand, varying throughout a day, is met byintermittent sources together with dispatchable generation (such asload following power plants,peaking power plants, which can be turned up or down quickly) orenergy storage.
Power plants that do not change their power output quickly, such as some large coal or nuclear plants, are generally calledbaseload power plants.[3][5][6] In the 20th century most or all of base load demand was met with baseload power plants,[7] whereas new capacity based around renewables often employs flexible generation.[8]
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 ofintermittent power sources anddispatchable generation.[4][10]
The desirable attribute ofdispatchability applies to some gas plants and hydroelectricity. Grid operators also usecurtailment to shut plants out of the grid when their energy is not needed.[13][14]
Some coal and nuclear power plants do not change production to match power consumption demands since it is sometimes more economical to keep operating them at constant production levels than to reduce output duringtimes of power price below marginal cost, and not all power plants are designed for it. TheIEA has suggested that coal power plants should not run as baseload, because thatemits a lot of carbon dioxide, whichcauses climate change.[18] Some nuclear power stations, such as thosein France, are physically capable of being used asload following power plants and do alter their output, to some degree, to help meet varying demands.[19][moved resource?][20][moved resource?]
Some combined-cycle plants usually fuelled by gas, can provide baseload power,[21][need quotation to verify][obsolete source] as well as being able to be cost-effectively cycled up and down to match more rapid fluctuations in consumption.
^abDonald G. Fink, H. Wayne Beatty (ed),Standard Handbook for Electrical Engineers, Eleventh Edition, Mc-Graw Hill, 1978ISBN9780070209749, pp. 12-16 through 12-18
