Dispatchable generation

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Grids with high penetration of renewable energy sources generally need dispatchable generation rather than baseload generation Renewables need flexible backup not baseload.png
Grids with high penetration of renewable energy sources generally need dispatchable generation rather than baseload 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. [1] Non-dispatchable renewable energy sources such as wind power and solar photovoltaic (PV) power cannot be controlled by operators. [2] Other types of renewable energy that are dispatchable without separate energy storage are hydroelectric, biomass, geothermal and ocean thermal energy conversion. [3]

Contents

Startup time

Dispatchable plants have varying startup times, depending on the technology used and time elapsed after the previous operation. For example, "hot startup" can be performed a few hours after a preceding shutdown, while "cold startup" is performed after a few days of inoperation.

The fastest plants to dispatch are grid batteries which can dispatch in milliseconds. Hydroelectric power plants can often dispatch in tens of seconds to minutes, and natural gas power plants can generally dispatch in tens of minutes.

For example, the 1,728 MW Dinorwig pumped storage power plant can reach full output in 16 seconds. [4]

Gas turbine (Brayton cycle) thermal plants require around 15-30 minutes to startup. Coal thermal plants based on steam turbines (Rankine cycle) are dispatchable sources that require hours to startup.

The combined cycle power plants consist of few stages with varying startup times with more than 8 hours required to get to full power from cold state: [5]

Nuclear power plants have the longest startup times of few days for the cold startup (less than a week). A typical boiling water reactor goes through the following stages: [6]

Benefits

The primary benefits of dispatchable power plants include: [7]

These capabilities of dispatchable generators allow:

Alternative classification

A 2018 study suggested a new classification of energy generation sources, which accounts for fast increase in penetration of variable renewable energy sources, which result in high energy prices during periods of low availability: [8]

See also

Related Research Articles

<span class="mw-page-title-main">Electricity generation</span> Process of generating electrical power

Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery to end users or its storage, using for example, the pumped-storage method.

<span class="mw-page-title-main">Power station</span> Facility generating electric power

A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid.

<span class="mw-page-title-main">Pumped-storage hydroelectricity</span> Electric energy storage system

Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential energy of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost surplus off-peak electric power is typically used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Although the losses of the pumping process make the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. If the upper lake collects significant rainfall or is fed by a river then the plant may be a net energy producer in the manner of a traditional hydroelectric plant.

<span class="mw-page-title-main">Hydroelectricity</span> Electricity generated by hydropower

Hydroelectricity, or hydroelectric power, is electricity generated from hydropower. Hydropower supplies one sixth of the world's electricity, almost 4,500 TWh in 2020, which is more than all other renewable sources combined and also more than nuclear power. Hydropower can provide large amounts of low-carbon electricity on demand, making it a key element for creating secure and clean electricity supply systems. A hydroelectric power station that has a dam and reservoir is a flexible source, since the amount of electricity produced can be increased or decreased in seconds or minutes in response to varying electricity demand. Once a hydroelectric complex is constructed, it produces no direct waste, and almost always emits considerably less greenhouse gas than fossil fuel-powered energy plants. However, when constructed in lowland rainforest areas, where part of the forest is inundated, substantial amounts of greenhouse gases may be emitted.

<span class="mw-page-title-main">Rolling blackout</span> Intentionally engineered electrical power shutdown

A rolling blackout, also referred to as rota or rotational load shedding, rota disconnection, feeder rotation, or a rotating outage, is an intentionally engineered electrical power shutdown in which electricity delivery is stopped for non-overlapping periods of time over different parts of the distribution region. Rolling blackouts are a last-resort measure used by an electric utility company to avoid a total blackout of the power system.

<span class="mw-page-title-main">Grid energy storage</span> Large scale electricity supply management

Grid energy storage is a collection of methods used for energy storage on a large scale within an electrical power grid. Electrical energy is stored during times when electricity is plentiful and inexpensive or when demand is low, and later returned to the grid when demand is high, and electricity prices tend to be higher.

<span class="mw-page-title-main">Base load</span> Minimum level of demand on an electrical grid over a span of time

The base load 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 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 plants, peaking power plants, or energy storage.

<span class="mw-page-title-main">Peaking power plant</span> Reserved for high demand times

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. 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.

<span class="mw-page-title-main">Diesel generator</span> Combination of a diesel engine with an electrical generator

A diesel generator (DG) (also known as a diesel genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of engine generator. A diesel compression-ignition engine is usually designed to run on diesel fuel, but some types are adapted for other liquid fuels or natural gas (CNG).

<span class="mw-page-title-main">Capacity factor</span> Electrical production measure

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 defined as that due to its continuous operation at full nameplate capacity over the relevant period. The capacity factor can be calculated for any electricity producing installation, such as a fuel consuming power plant or one using renewable energy, such as wind, the sun or hydro-electric installations. The average capacity factor can also be defined for any class of such installations, and can be used to compare different types of electricity production.

Dynamic Demand is the name of a semi-passive technology to support demand response by adjusting the load demand on an electrical power grid. It is also the name of an independent not-for-profit organization in the UK supported by a charitable grant from the Esmée Fairbairn Foundation, dedicated to promoting this technology. The concept is that by monitoring the frequency of the power grid, as well as their own controls, intermittent domestic and industrial loads switch themselves on/off at optimal moments to balance the overall grid load with generation, reducing critical power mismatches. As this switching would only advance or delay the appliance operating cycle by a few seconds, it would be unnoticeable to the end user. This is the foundation of dynamic demand control. In the United States, in 1982, a (now-lapsed) patent for this idea was issued to power systems engineer Fred Schweppe. Other patents have been issued based on this idea.

<span class="mw-page-title-main">Hybrid power</span> Combinations between different technologies to generate electric power

Hybrid power are combinations between different technologies to produce power.

To balance the supply and demand of electricity on short timescales, the UK National Grid has contracts in place with generators and large energy users to provide temporary extra power, or reduction in demand. These reserve services are needed if a power station fails for example, or if forecast demand differs from actual demand. National Grid has several classes of reserve services, which in descending order of response time are: Balancing Mechanism (BM) Start-Up, Short-Term Operating Reserve, Demand Management and Fast Reserve.

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 load and peaking power plants in efficiency, speed of start-up and shut-down, construction cost, cost of electricity and capacity factor.

<span class="mw-page-title-main">Levelized cost of electricity</span> Measure of lifetime average net present cost of electricity generation

The levelized cost of electricity (LCOE) is a measure of the average net present cost of electricity generation for a generator over its lifetime. It is used for investment planning and to compare different methods of electricity generation on a consistent basis.

<span class="mw-page-title-main">Electrical grid</span> Interconnected network for delivering electricity from suppliers to consumers

An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids consist of power stations, electrical substations to step voltage up or down, electric power transmission to carry power over long distances, and finally electric power distribution to customers. In that last step, voltage is stepped down again to the required service voltage. Power stations are typically built close to energy sources and far from densely populated areas. Electrical grids vary in size and can cover whole countries or continents. From small to large there are microgrids, wide area synchronous grids, and super grids.

Different methods of electricity generation can incur a variety of different costs, which can be divided into three general categories: 1) wholesale costs, or all costs paid by utilities associated with acquiring and distributing electricity to consumers, 2) retail costs paid by consumers, and 3) external costs, or externalities, imposed on society.

Ancillary services are the services necessary to support the transmission of electric power from generators to consumers given the obligations of control areas and transmission utilities within those control areas to maintain reliable operations of the interconnected transmission system.

<span class="mw-page-title-main">Variable renewable energy</span> Class of renewable energy sources

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 energy sources, such as dammed hydroelectricity or bioenergy, or relatively constant sources, such as geothermal power.

Moorside clean energy hub is a proposal put forward on 30 June 2020 by two consortia, one led by EDF and the other by Rolls-Royce, to create an energy hub that would produce electricity and hydrogen through the use of nuclear power and renewable energy.

References

  1. Cooper, Duncan (22 March 2012). "Johnson's Energy Club Competes in Renewable Energy Case Competition". Samuel Curtis Johnson Graduate School of Management. Archived from the original on 16 June 2012. Retrieved 29 August 2012. Most conventional energy sources are dispatchable, meaning that they can be turned on or off according to the demand for electricity. The amount of electricity they produce can also be turned up or down so that supply of electricity matches the amount demanded by users.
  2. Electricity Grid: Key Terms and Definitions
  3. Global Energy Assessment: Toward a Sustainable Future
  4. "Welcome to First Hydro" (PDF). Archived from the original (PDF) on 2016-03-03. Retrieved 2013-01-08.
  5. Ivanova, Sauhats & Linkevics 2016, p. 2.
  6. Li 2021, p. 23.
  7. How can renewables deliver dispatchable power on demand?
  8. Sepulveda, Nestor A.; Jenkins, Jesse D.; De Sisternes, Fernando J.; Lester, Richard K. (2018-11-21). "The Role of Firm Low-Carbon Electricity Resources in Deep Decarbonization of Power Generation". Joule. 2 (11): 2403–2420. doi: 10.1016/j.joule.2018.08.006 . ISSN   2542-4351.

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