Abstract
The authors already have shown that the conversion efficiency of tidal current energy by a vertical Savonius water turbine is significantly improved by introducing outer ring type current controlling devices. In order to obtain much higher extraction rate of the tidal current power and also seeking a more simple structural form of guide vanes, a new type of guide vane was examined and proposed. The proposed guide vane in this study is composed of four vertical thin walls in axisymmetrical arrangement. We call it as a vortex-stream like guide vane. It was confirmed that the extraction rate of the tidal current power of a vertical Savonius water turbine becomes more than fifty percents by installing a new guide vane. Also the rotating torque by the turbine is significantly magnified, typically four or five times as large as the case without a guide vane.
