Реферат: Wind Power Essay Research Paper The wind

P turbine

The power available is a function of elevation. At ground level, 100% of

the power is available. At 100 feet, 97% is available. At 5000 feet, 86%

is available. Some turbines are shrouded like jet engines. The shroud is

a way to channel the wind. An equation for the power harnessed by a

shrouded wind turbine is: P(Pe) = ( QT ((p + (k) where P is the power,

Pe is the power extracted, ( is the turbine efficiency, QT is the

volumetric flow rate of air on the turbine, (V/A), ((p + (k) is the change

in pressure energy between the inlet and the exit of the wind turbine, and

k is the cane in kinetic energy of a unit volume of air that passes

through the machine.

Shrouds concentrate and diffuse the wind as it passes through a

horizontal access wind-turbine. They reduce the turbulence of the wind

and “direct it”. The advantages of shrouds, as told by Cheremisinoff (pg.

61 of Fundamentals of Wind Energy), are: a ) the axial velocity of the

turbine increases, meaning that smaller rotors can operate at higher

revolutions, b) the shroud can greatly reduce tip-losses, and c) the

aerofoils would not have to be rotated in a direction parallel to the wind

if the wind-di rection changed. The cut in speed is the lowest wind speed

below which no usable power can be produced by a wind turbine. This means

that the wind must be fast enough to move the aerofoils to drive the shaft

to create enough power, after much is lost, so that the end amo unt of

power is greater than zero. Rated power is the maximum power output of a

turbine, which is dependent on a number of factors, especially the

generator. In calculating the height of the windmill, it is important to

keep in mind that the windmill must be high enough to be above

obstructions. The wind velocity decreases as one approaches the surface.

That means that the higher you build, the better chance

there will be that the wind speed is higher, however, you must find the