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Capacity factor should not be confused with [[efficiency]]. | Capacity factor should not be confused with [[efficiency]] or [[availability]]. | ||
Capacity factor is the fraction of energy actually produced over a period of time – usually a year – of what a generator has the capacity to produce. | Capacity factor is the fraction of energy actually produced over a period of time – usually a year – of what a generator has the capacity to produce. | ||
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Other dispatchable plants have lower capacity factors, because they are called on only when needed to supply power above the base load. | Other dispatchable plants have lower capacity factors, because they are called on only when needed to supply power above the base load. | ||
For nondispatchable sources – i.e., ones that generate electricity according to wind speed or sunlight rather than actual demand on the grid – capacity factor is determined by their fuel sources and | For nondispatchable sources – i.e., ones that generate electricity according to wind speed and direction or sunlight rather than actual demand on the grid – capacity factor is determined by the variability of their fuel sources (i.e., wind and sun). | ||
Wind turbines generate electricity at an annual average rate of 25%–35% of their capacity.<ref>https://www.eia.gov/electricity/data/eia923/</ref> | Wind turbines generate electricity at an annual average rate of 25%–35% of their capacity.<ref>https://www.eia.gov/electricity/data/eia923/</ref> | ||
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==Capacity value== | ==Capacity value== | ||
Grid operators have to be able to call on the various generating plants as needed to meet demand. The ability to do so can be expressed as a plant’s ''capacity value'', the percentage of time that it can be called on to provide power to the grid. It is a measure of dispatchability. The capacity value of most plants is effectively 100%. | Grid operators have to be able to call on the various generating plants as needed to meet demand. The ability to do so can be expressed as a plant’s ''capacity value'', the percentage of time that it can be called on to provide power to the grid. It is a measure of dispatchability. The capacity value of most power plants is effectively 100%. | ||
Wind turbines, however, can not be “called on” except by the wind, which has only a random relationship to user demand for electricity.<ref>https://wind-watch.org/pix/displayimage.php?pid=494</ref><ref>https://wind-watch.org/pix/displayimage.php?pid=493</ref><ref>https://wind-watch.org/pix/displayimage.php?pid=660</ref><ref>https://wind-watch.org/pix/displayimage.php?pid=73</ref> Therefore, their capacity value is effectively zero. This means that to meet the needs of the grid, other – dispatchable – sources have to be maintained and built just as if wind turbines were not on the grid. | Wind turbines, however, can not be “called on” except by the wind, which has only a random relationship to user demand for electricity.<ref>https://wind-watch.org/pix/displayimage.php?pid=494</ref><ref>https://wind-watch.org/pix/displayimage.php?pid=493</ref><ref>https://wind-watch.org/pix/displayimage.php?pid=660</ref><ref>https://wind-watch.org/pix/displayimage.php?pid=73</ref> Therefore, their capacity value is effectively zero. This means that to meet the needs of the grid, other – dispatchable – sources have to be maintained and built just as if wind turbines were not on the grid. |