Реферат: Wind Power Essay Research Paper The wind

will be 2.5 feet wide at its widest point). A erofoils come in many

shapes. Some blades are made a little wider than this ratio, because it

is easier to start such a windmill. However, blades like this aren’t as

efficient. No matter what the shape, “most have a blunt nose and a finely

tapering tab le” (Calvert). A flow must be able to follow the curved

surfaces of the aerofoil without being separated. The mass flow rate is

given by the equation: m = p Vb A, where p is the air density, Vb is the

air speed at the blades and A is the area. The number of blades on a

windmill varies. There are many different types of windmills. The

following equation helps figure out how fast the a certain-bladed windmill

will rotate in relation to windmills with different numbers of blades:

Speed of windmill = 1 / sq. root of number of blades The aerofoils of a

four bladed machine rotate 71% as fast as that of a 2 bladed machine. A

six bladed machine rotates at 58% and an 8 bladed machine rotates at 56%

as fast as a 2 bladed machine.

Electricity and Storage of Energy

As mentioned previously, the generators in a wind turbine can

convert the mechanical energy produced by the rotation of the shaft into

electrical energy, DC. From there, some windmills have synchronous

inverters, complex electronic devices which convert

the DC generated by the turbines into AC. This is an expensive option.

There is a loss of power as well through its processes. Others have

induction generators, which produce AC current without a synchronous

inverter and less power loss. The energy extracted from the wind and

converted into mechanical energy then electrical energy by the generator

must be stored, since it is not used generally used all at once. It is

important to keep a surplus of energy for usage when the wind is not bl

owing fast enough, despite the corrections that can be made in the pitch

of the aerofoil blades and when the windmill is out of service or the