Реферат: Wind Power Essay Research Paper The wind

Turbines

Windmills are turbines. The two names can be used synonymously.

Turbines are a means of harnessing the a fluid’s power (the wind) by

converting the kinetic energy of the fluid (the wind) into mechanical

power (the rotating shaft) When the shaft of a w indmill is hooked up to a

generator, electrical energy can be formed. The generator can be used to

produce either DC or AC current. Generators that produce DC can be

connected to batteries, an inverter to produce AC, or to power DC loads.

Some generato rs are connected to heating coils. Generators that produce

AC can be hooked up to AC motors such as water pumps. Windmills are NOT

efficient. At the very most, a windmill can extract only 16/27ths of the

kinetic energy from the wind. This is called the Betz Limit and it can be

mathematically proven through calculus. Most of today’s windmills extract

about 30 perc ent of the wind’s energy. The American farm windmill can

only extract 10%. An important equation used to find the wind power

density, how much power is available per square meter is the equation P =

.5 pu?, where P is the wind power density in W/m2, p is the density of the

air, and u? is the cube of the wind velocity. An equation for the power

available is (kinetic energy flux) = .5 p V3 A, where p is the kinetic

energy density J/m?, V is the velocity of the wind, A is the cross

sectional area of the wind on the turbine.

The equation for determining the power of the shaft, (which is

less than the final power output, since gear trains and generators cause

power to be lost) is as follows: Cp = P((((((((

(0.5 p V ? ( D2)

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Where Cp is the power coefficient (Power of shaft), p is the air density,

D is the rotor diameter, V is the velocity of the wind and P is the net

power output.