rotor mixte Darrieus-Savonius

OBS: The major competitor of the propeller system is the vertical-axis Darrieus rotor. This is a lift device having curved blades with airfoil cross sections. Darrieus rotors have low starting torques but high tip speed ratios and, therefore, relatively high power outputs for their weight and cost. They are very efficient, but are not self-starting. Hence the machine is connected to a utility grid so that the generator can drive the rotor to a self-sustaining speed or is hybridized with a self-starting, but less-efficient Savonius rotor.