Monday, May 18, 2009

Wind renewable energy



Wind renewable energy in airflows can be used to run wind turbines. Modern wind energy turbines range from around 600 kW to 5 MW of rated power, although wind turbines with rated output of 1.5–3 MW have become the most common for commercial use. The power output of a wind turbine is a function of the cube of the wind speed, so as wind speed increases, power output of a wind turbine increases dramatically. Wind energy can be used in areas where winds are stronger and more constant, such as offshore and high altitude, are perfect wind energy farms.
Since wind speed is not constant, a wind farm's annual energy production of wind energy farms is never as much as the sum of the generator nameplate ratings multiplied by the total hours in a year. The ratio of actual wind energy farm productivity in a year to this theoretical maximum is called the capacity factor. Typical capacity factors of wind energy farms are 20-40%, with values at the upper end of the range in particularly favourable wind energy sites.
For example, a 1 megawatt wind energy turbine with a capacity factor of 35% will not produce 8,760 megawatt-hours of wind renewable electricity in a year, but only 0.35x24x365 = 3,066 MWh, averaging to 0.35 MW of wind energy.
Globally, the long-term technical potential of wind energy is believed to be five times total current global energy production, or 40 times current electricity demand. This could require large amounts of land for wind energy turbines, particularly in areas of higher wind resources. Offshore resources experience mean wind speeds of ~90% greater than that of land, so offshore resources could contribute substantially more renewable energy. This number could also increase with higher altitude ground-based or airborne wind energy turbines.
Wind energy is renewable and produces no greenhouse gases during operation, such as carbon dioxide and methane.

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