|
MasterSlaveLA -> RE: windmills (6/20/2011 11:14:14 AM)
|
Personally, I don't have an issue with the "visual appeal" of windmills, just that they're too ineffecient to meet power demands. (shrugs)
Capacity factorSince wind speed is not constant, a wind farm's annual energy production is never as much as the sum of the generator nameplate ratings multiplied by the total hours in a year. The ratio of actual productivity in a year to this theoretical maximum is called the capacity factor. Typical capacity factors are 20–40%, with values at the upper end of the range in particularly favourable sites.[19] For example, a 1 MW turbine with a capacity factor of 35% will not produce 8,760 MW·h in a year (1 × 24 × 365), but only 1 × 0.35 × 24 × 365 = 3,066 MW·h, averaging to 0.35 MW. Online data is available for some locations and the capacity factor can be calculated from the yearly output.[20][21]
Unlike fueled generating plants, the capacity factor is affected by several parameters, including the variability of the wind at the site, but also the generator size- having a smaller generator would be cheaper and achieve higher capacity factor, but would make less electricity (and money) in high winds.[22] Conversely a bigger generator would cost more and generate little extra power and, depending on the type, may stall out at low wind speed. Thus an optimum capacity factor can be used, which is usually around 20-35%.
Capacity factors of other types of power plant are based mostly on fuel cost, with a small amount of downtime for maintenance. Nuclear plants have low incremental fuel cost and are particularly expensive to build, and so have to be run at full output as much as possible to be economic and thus must achieve a 80-90% capacity factor.
Fossil fueled power plants often run at roughly 40-60% capacity, depending on the type- plants with higher fuel cost are throttled back to follow load. Gas turbine plants using natural gas as fuel may be very expensive to operate and may be run only to meet peak power demand.[dubious – discuss] A gas turbine plant may have an annual capacity factor of 5–25% due to relatively high energy production cost.
In a 2008 study released by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy, the capacity factor achieved by the wind turbine fleet is shown to be increasing as the technology improves. The capacity factor achieved by new wind turbines in 2004 and 2005 reached 36%.[23]
http://en.wikipedia.org/wiki/Wind_power#Capacity_factor
|
|
|
|
