Availability factor

Last updated

The availability factor of a power plant is the amount of time that it is able to produce electricity over a certain period, divided by the amount of the time in the period. Occasions where only partial capacity is available may or may not be deducted. Where they are deducted, the metric is titled equivalent availability factor (EAF). The availability factor should not be confused with the capacity factor. The capacity factor for a given period can never exceed the availability factor for the same period. The difference arises when the plant is run at less than full capacity, in which case the capacity factor is less than the availability factor.

The availability of a power plant varies greatly depending on the type of fuel, the design of the plant and how the plant is operated. Everything else being equal, plants that are run less frequently have higher availability factors because they require less maintenance and because more inspections and maintenance can be scheduled during idle time. Most thermal power stations, such as coal, geothermal and nuclear power plants, have availability factors between 70% and 90%. Newer plants tend to have significantly higher availability factors, but preventive maintenance is as important as improvements in design and technology. Gas turbines have relatively high availability factors, ranging from 80% to 99%. Gas turbines are commonly used for peaking power plants, co-generation plants and the first stage of combined cycle plants.

Originally the term availability factor was used only for power plants that depended on an active, controlled supply of fuel, typically fossil or later also nuclear. The emergence of renewable energy such as hydro, wind and solar power, which operate without an active, controlled supply of fuel and which come to a standstill when their natural supply of energy ceases, requires a more careful distinction between the availability factor and the capacity factor. By convention, such zero production periods are counted against the capacity factor but not against the availability factor, which thus remains defined as depending on an active, controlled supply of fuel, along with factors concerning reliability and maintenance. A wind turbine cannot operate in wind speeds above a certain limit, which counts against its availability factor. [1] With this definition, modern wind turbines which require very little maintenance, have very high availability factors, up to about 98%. Photovoltaic power stations which have few or no moving parts and which can undergo planned inspections and maintenance during night have an availability factor approaching or equal to 100% when the sun is shining.[ citation needed ]

See also

Related Research Articles

Nuclear power plant Thermal power station where the heat source is a nuclear reactor

A nuclear power plant is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine connected to a generator that produces electricity. As of 2018, the International Atomic Energy Agency reported there were 450 nuclear power reactors in operation in 30 countries around the world.

Power station 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.

Distributed generation, also distributed energy, on-site generation (OSG), or district/decentralized energy, is electrical generation and storage performed by a variety of small, grid-connected or distribution system-connected devices referred to as distributed energy resources (DER).

Wind power Electrical power generation from wind

Wind power or wind energy is the use of wind to provide mechanical power through wind turbines to turn electric generators for electrical power. Wind power is a popular sustainable, renewable energy source that has a much smaller impact on the environment compared to burning fossil fuels.

Hydroelectricity Electricity generated by hydropower

Hydroelectricity, or hydroelectric power, is electricity produced from hydropower. In 2015, hydropower generated 16.6% of the world's total electricity and 70% of all renewable electricity, and was expected to increase by about 3.1% each year for the next 25 years.

Combined cycle power plant

A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turbine (CCGT) plant. The same principle is also used for marine propulsion, where it is called a combined gas and steam (COGAS) plant. Combining two or more thermodynamic cycles improves overall efficiency, which reduces fuel costs.

Electric power systems consist of generation plants of different energy sources, transmission networks, and distribution lines. Each of these components can have environmental impacts at multiple stages of their development and use including in their construction, during the generation of electricity, and in their decommissioning and disposal. We can split these impacts into operational impacts and construction impacts. This page looks exclusively at the operational environmental impact of electricity generation. The page is organized by energy source and includes impacts such as water usage, emissions, local pollution, and wildlife displacement.

OPG 7 commemorative turbine

The OPG 7 Gomberg Turbine was a Vestas model V80-1.8MW wind turbine in Pickering, Ontario. At the time of its construction, it was one of the largest wind turbines in North America, a 117-metre high wind machine commissioned in 2001 and designed to produce enough power to satisfy about 600 average households. This electricity was also emission-free.

Grid energy storage

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.

Base load Minimum level of demand on an electrical grid over a span of time

The baseload 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 which can be turned up or down quickly, such as load following power plants, peaking power plants, or energy storage.

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. 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.

Advanced boiling water reactor Nuclear reactor design

The advanced boiling water reactor (ABWR) is a Generation III boiling water reactor. The ABWR is currently offered by GE Hitachi Nuclear Energy (GEH) and Toshiba. The ABWR generates electrical power by using steam to power a turbine connected to a generator; the steam is boiled from water using heat generated by fission reactions within nuclear fuel. Kashiwazaki-Kariwa unit 6 is considered the first Generation III reactor in the world.

Capacity factor

The net capacity factor is the unitless ratio of an actual electrical energy output over a given period of time to the maximum possible electrical energy output over that period. The capacity factor is defined for any electricity producing installation, such as a fuel consuming power plant or one using renewable energy, such as wind or the sun. 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.

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.

Electric steam boiler

An electric steam boiler is a type of boiler where the steam is generated using electricity, rather than through the combustion of a fuel source. Such boilers are used to generate steam for process purposes in many locations, for example laundries, food processing factories and hospitals. Although they are more expensive to run than gas-fired or oil-fired boilers they are popular because of their simplicity and ease of use. Because of the large currents required, they are normally run from a three-phase electricity supply. They convert electrical energy into thermal energy with almost 100% efficiency but the overall thermal efficiency is variable, depending on the efficiency with which the electricity is generated.

Electrical grid 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 vary in size and can cover whole countries or continents. It consists of:

Wind turbine Machine which converts wind energy into mechanical and electric energy

A wind turbine is a device that converts the wind's kinetic energy into electrical energy.

Cost of electricity by source Comparison of costs of different electricity generation sources

Different methods of electricity generation can incur significantly different costs, and these costs can occur at significantly different times relative to when the power is used. The costs include the initial capital, and the costs of continuous operation, fuel, and maintenance as well as the costs of de-commissioning and remediating any environmental damage. Calculations of these costs can be made at the point of connection to a load or to the electricity grid, so that they may or may not include the transmission costs.

Renewable energy debate

Policy makers often debate the constraints and opportunities of renewable energy.

Variable renewable energy 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 biomass, or relatively constant sources, such as geothermal power.

References

  1. "AVAILABILITY FACTOR". huronwind.com . Retrieved 2017-02-11.