[edit
<http://en.wikipedia.org/w/index.php?title=Wind_turbine&action=edit&sect\
ion=2> ] Potential turbine powerMain article: Wind turbine design
<http://en.wikipedia.org/wiki/Wind_turbine_design> [Wind Turbine Power
Coefficent] <http://en.wikipedia.org/wiki/Image:Wind_power_coeff.jpg>
[http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png]
<http://en.wikipedia.org/wiki/Image:Wind_power_coeff.jpg> Wind Turbine
Power Coefficent
The amount of power <http://en.wikipedia.org/wiki/Power_(physics)>
transferred to a wind turbine is directly proportional to the area swept
out by the rotor, to the density of the air, and the cube of the wind
speed.

The power P in the wind is given by:
[P = \begin{matrix}\frac{1}{2}\end{matrix}\alpha\rho\pi r^2 v^3] ,
where P = power in watts, á = an efficiency
<http://en.wikipedia.org/wiki/Energy_efficiency> factor determined by
the design of the turbine, ñ = mass density of air in kilograms per
cubic meter, r = radius of the wind turbine in meters, and v = velocity
of the air in meters per second.[5]

As the wind turbine extracts energy from the air flow, the air is slowed
down, which causes it to spread out. Albert Betz
<http://en.wikipedia.org/wiki/Albert_Betz> , a German physicist,
determined in 1919 (see Betz' law
<http://en.wikipedia.org/wiki/Betz%27_law> ) that a wind turbine can
extract at most 59% of the energy that would otherwise flow through the
turbine's cross section, that is á can never be higher than 0.59 in
the above equation. The Betz limit applies regardless of the design of
the turbine.

This equation shows the effects of the mass rate of flow of air
traveling through the turbine, and the energy of each unit mass of air
flow caused by its velocity. As an example, on a cool 15 °C (59
°F) day at sea level, air density is 1.225 kilograms per cubic metre.
An 8 m/s (28.8 km/h or 18 mi/h) breeze blowing through a 100 meter
diameter rotor would move almost 77,000 kilograms of air per second
through the swept area. The total power of the example breeze through a
100 meter diameter rotor would be about 2.5 megawatts. Betz' law states
that no more than 1.5 megawatts could be extracted.



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