6/27/2014 Availability factor - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Availability_factor 1/2

Availability factorFrom Wikipedia, the free encyclopedia

The availability factor of a power plant is the amount of time that it is able to produce electricity over a certainperiod, divided by the amount of the time in the period. Occasions where only partial capacity is available may ormay not be deducted. Where they are, the metric is titled Equivalent Availability Factor (EAF). The AvailabilityFactor should not be confused with the capacity factor. The Capacity Factor for a period will always be less thanthe Equivalent Availability Factor for the same period. The difference depends on the utilization of the power plant.

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

The availability factor of wind and solar power plants depends on weather periods when the plant is operational,but there is no wind or sunlight, are counted as available, unavailable or disregarded. If they are counted asavailable during these times, photovoltaic plants have an availability factor approaching or equal to 100%. Modernwind turbines also have very high availability factors, about 98%. However, solar and wind plants have relativelylow capacity factors. In the wiki on capacity factors you can see that wind capacity factors range from 20-40% andsolar capacity factors in Arizona are about 19%. This makes wind and solar availability factors much lower if timeswhen sunlight or wind are not available are taken into account.

References

See also

Availability (Reliability Engineering)

Capacity factor

Generating Availability Data System (Electricity Industry)

List of energy storage projects

Utilization factor

Forced outage rate

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Categories: Power station technology

This page was last modified on 2 December 2013 at 20:22.

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6/27/2014 Availability factor - Wikipedia, the free encyclopedia

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