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The base load (also baseload) 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 Dispatchable generation refers to sources of electricity that can be programmed ''on demand'' at the request of power grid operators, according to market needs. Dispatchable generators may adjust their power output according to an order. Non-disp ...
, or by a collection of smaller
intermittent energy source Variable renewable energy (VRE) or intermittent renewable energy sources (IRES) are renewable energy sources that are not dispatchable due to their fluctuating nature, such as wind power and solar power, as opposed to controllable renewable ener ...
s, 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 by dispatchable generation which can be turned up or down quickly, such as
load following power plant A load-following power plant, regarded as producing mid-merit or mid-priced electricity, is a power plant that adjusts its power output as demand for electricity fluctuates throughout the day. Load-following plants are typically in between base lo ...
s, peaking power plants, or 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. Donald G. Fink, H. Wayne Beatty (ed), ''Standard Handbook for Electrical Engineers'', Eleventh Edition, Mc-Graw Hill, 1978 , pp. 12-16 through 12-18 Historically, most or all of base load demand was met with baseload power plants, whereas new capacity based around renewables often employs flexible generation.


Description

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 The unit commitment problem (UC) in electrical power production is a large family of mathematical optimization problems where the production of a set of electrical generators is coordinated in order to achieve some common target, usually either matc ...
. 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 source Variable renewable energy (VRE) or intermittent renewable energy sources (IRES) are renewable energy sources that are not dispatchable due to their fluctuating nature, such as wind power and solar power, as opposed to controllable renewable ener ...
s and
dispatchable generation Dispatchable generation refers to sources of electricity that can be programmed ''on demand'' at the request of power grid operators, according to market needs. Dispatchable generators may adjust their power output according to an order. Non-disp ...
. Unvarying power plants can be coal, nuclear, combined cycle plants, which may take several days to start up and shut down, hydroelectric, geothermal,
biogas Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
, biomass, solar thermal with storage and
ocean thermal energy conversion Ocean Thermal Energy Conversion (OTEC) uses the ocean thermal gradient between cooler deep and warmer shallow or surface seawaters to run a heat engine and produce useful work, usually in the form of electricity. OTEC can operate with a very hi ...
. The desirable attribute of dispatchability applies to some gas plants, wind (through
blade pitch Blade pitch or simply pitch refers to the angle of a blade in a fluid. The term has applications in aeronautics, shipping, and other fields. Aeronautics In aeronautics, blade pitch refers to the angle of the blades of an aircraft propeller o ...
) and hydroelectricity. Grid operators also use '' curtailment'' to shut plants out of the grid when their energy is not needed.


Economics

Grid operators solicit bids to find the cheapest sources of electricity over short and long term buying periods. Nuclear and coal plants have very high
fixed costs In accounting and economics, 'fixed costs', also known as indirect costs or overhead costs, are business expenses that are not dependent on the level of goods or services produced by the business. They tend to be recurring, such as interest or r ...
, high
plant load factor The net capacity factor is the unitless ratio of actual electrical energy output over a given period of time to the theoretical maximum electrical energy output over that period. The theoretical maximum energy output of a given installation is def ...
but very low
marginal costs In economics, the marginal cost is the change in the total cost that arises when the quantity produced is incremented, the cost of producing additional quantity. In some contexts, it refers to an increment of one unit of output, and in others it r ...
. On the other hand, peak load generators, such as
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
, have low fixed costs, low plant load factor and high marginal costs. Coal and nuclear power plants do not change production to match power consumption demands since it is more economical to operate them at constant production levels, and not all power plants are designed for it. However, some nuclear power stations, such as those in France, are physically capable of being used as
load following power plant A load-following power plant, regarded as producing mid-merit or mid-priced electricity, is a power plant that adjusts its power output as demand for electricity fluctuates throughout the day. Load-following plants are typically in between base lo ...
s and do alter their output, to some degree, to help meet varying demands. Some combined-cycle plants usually fuelled by gas, can provide baseload power, as well as being able to be cost-effectively cycled up and down to match more rapid fluctuations in consumption. According to National Grid plc
chief executive officer A chief executive officer (CEO), also known as a central executive officer (CEO), chief administrator officer (CAO) or just chief executive (CE), is one of a number of corporate executives charged with the management of an organization especial ...
Steve Holliday Steven John Holliday FREng, born 26 October 1956, is a British businessman and engineer. He was the chief executive officer (CEO) of National Grid plc from 2007 to 2016. Early life Born in Exeter, Holliday is the son of Michael J. Holliday and ...
and others, baseload is "outdated".


See also

*
Capacity factor The net capacity factor is the unitless ratio of actual electrical energy output over a given period of time to the theoretical maximum electrical energy output over that period. The theoretical maximum energy output of a given installation is def ...
*
Energy demand management Energy demand management, also known as demand-side management (DSM) or demand-side response (DSR), is the modification of consumer demand for energy through various methods such as financial incentives and behavioral change through education. Us ...
* Grid energy storage *
Load balancing (electrical power) Load balancing, load matching, or daily peak demand reserve refers to the use of various techniques by electrical power stations to store excess electrical power during low demand periods for release as demand rises. The aim is for the power supp ...
* Smart grid *
Load following power plant A load-following power plant, regarded as producing mid-merit or mid-priced electricity, is a power plant that adjusts its power output as demand for electricity fluctuates throughout the day. Load-following plants are typically in between base lo ...
* Peaking power plant


References


External links


Base Load Power Plants - Fundamentals of Electricity
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The Energy Resources and Economics Workbook (.doc)
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