Abstract: A windmill assembly includes (a) a support frame; (b) a rotor rotatably mounted to the support frame for rotation around a vertical axis in response to the movement of wind passing the wind engine. The rotor includes (i) a shaft, (ii) at least two wings extending radially from the shaft, and (iii) a plurality of vanes pivotally mounted to one side of each wing and movable between a closed first position wherein the vanes prevent wind from passing through the wing and an open second position wherein the vanes permit wind to pass through spaces between the vanes and through the wing, wherein the wings are arranged such that when the vanes on one wing are in the closed position the vanes on the other wing are at least partially open.