Chapter 4

Rotors and Blades


The element of a wind turbine that captures energy from the wind is the rotor. Efficiency will depend on the number of blades on the rotor, their shape, their length, and the speed at which the rotor turns. The total amount of energy available depends on the area swept out by the blades, the swept area. The larger this is, the more energy can be captured. The blades of a modern wind turbine have an aerofoil shape similar to an aeroplane wing. The shape creates lift as the wind passes over it. Maximum lift is generated from a moving blade if it is twisted slightly. The optimum rotational speed of a wind turbine rotor is defined in terms of a factor called the tip speed ratio. This is typically 7–10 for a three ...

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