Patent ID: 8371809

Claim:
A windmill device comprising: a stator provided with a plurality of stator blades; and a rotor provided with a plurality of rotor blades and positioned inside a hollow area of the stator, wherein said rotor is adapted to rotate with respect to the stator about an axis of rotation and wherein the plurality of stator blades are adapted to direct an air flow coming from outside the stator toward the rotor, and the rotor blades being adapted to cause said rotor to rotate about said axis of rotation due to the effect of said directed air flow, and wherein: at least some of the plurality of rotor blades have a concave profile on one side, at least some of the plurality of stator blades have a concave profile on one side, and wherein the rotor blades with a concave profile have a chord greater than a chord of the stator blades having a concave profile, and wherein a maximum distance between a concave side of the concave profile of each of the at least some of the rotor blades and the chord of the respective rotor blade is greater than one third of a length of the chord and a tangent to a center line of the stator blade at its trailing edge is substantially parallel to a tangent to a center line of the rotor blade at its leading edge.