How many blades should a wind turbine rotor have? Each system has its own characteristics. Although the main types used in the wind industry have three blades, two-bladed rotors are also deployed.
Rotors with two blades are mechanically less stable than three-bladed rotors. They are susceptible to dynamic loads and higher sound levels. This situation can largely be remedied with a teeter hinge. One advantage of two-bladed rotors is that they require less material than three-bladed ones, making the associated logistics easier. They also have high tip speed ratios.
Three-bladed rotors are easily the most common type since they are used in over 90% of wind turbines. Having three blades makes their aerodynamics easier to control for two reasons: the reduced effect of the tower shadow and the more favourable weight distribution on the rotor. This means that three-bladed rotors suffer less from vibration problems than other types. Modern three-bladed rotors have tip speed ratios of 6–10. Since their tips move more slowly, they are quieter than older wind turbines. And because their blades have a larger overall surface area, a slower start-up speed is necessary, enabling wind turbines with three-bladed rotors to be used in areas with little wind.