The Savonius rotor concept never became popular, until recently, probably because of its low efficiency. However, it has the following advantages over the other conventional wind turbines: - simple and cheap construction; - acceptance of wind from any direction thus eliminating the need for reorientation; - high starting torque; - relatively low operating speed (rpm). The above advantages may not outweigh its low efficiency and make it an ideal economical source to meet small scale power requirements, especially in the rural parts of developing countries. ----- The concept of the Savonius rotor was based on the principle developed by Flettner. Savonius used a rotor which was formed by cutting the Flettner cylinder into two halves along the central plane and then moving the two semicylindrical surfaces sideways along the cutting plane so that the cross-section resembled the letter “S.”