Patent ID: 7696635

Claim:
A vertical axis wind turbine comprising: (a) a turbine rotor with a rotatable vertical shaft and at least three rotor vanes disposed for rotation about the vertical shaft, each rotor vane being substantially box-shaped with four solid rectangular sides and equally sized front and rear rectangular sides disposed in a radial vertical plane, the front side being substantially open faced and the rear side having an opening covered by a flap that moves into the box-shaped rotor vane with a directional passage of wind against an exterior of the flap for reducing drag resistance against the rear side of and through the rotor vane, said rear side including a narrow rim along at least three of its sides, said same flap returning to form the rear side of the rotor vane with the directional passage of wind against an interior of the flap for improving turbine rotor efficiency, each rotor vane having a front-to-rear depth that is at least half its height; and (b) means for attaching each rotor vane to the vertical shaft so that the front side of each vane lies in the same rotational direction around the vertical shaft.