wind turbine blades
Wind turbine blades are usually flat objects connected to a center shaft that converts the push of the wind into a circular motion in a wind turbine. Most wind turbines have three blades. Very small turbines may use two blades for ease of construction and installation. Vibration intensity decreases with larger numbers of blades. Noise and wear are generally lower, and efficiency higher, with three instead of two blades.
Turbines with larger numbers of smaller blades operate at a lower Reynolds number and so are less efficient. Small turbines with 4 or more blades suffer further losses as each blade operates partly in the wake of the other blades. Also, the cost of the turbine usually increases with the number of blades.
One of the strongest construction materials available (in 2006) is graphite-fibre in epoxy, but it is very expensive and only used by some manufactures for special load-bearing parts of the rotor blades. Modern rotor blades (up to 126 m diameter) are made of lightweight pultruded glass-reinforced plastic, smaller ones also from aluminum, or sometimes laminated wood.