Savonius Wind Turbine - Power and Rotational Speed

Power and Rotational Speed

The maximum power of a Savonius rotor is given by, where and are the height and radius of the rotor and is the wind speed.

The angular frequency of a rotor is given by, where is a dimensionless factor called the tip-speed ratio. λ is characteristic of a specific windmill, and its value is typically between 0.5 and 14. In a Savonius rotor, λ≈1.

For example, an oil-barrel sized Savonius rotor with h=1 m and r=0.5 m under a wind of v=10 m/s, will generate a maximum power of 160 W and an angular speed of 20 rad/s (190 revolutions per minute).