How to Increase Savonius Power Coefficient: Ducted Rotor Performance with Different Overlap Ratios

Abstract The use of ducted configuration to increase the efficiency wind turbine rotors is gaining wide attention in scientific community. Specifically for mini and micro urban environment applications this solution demonstrated be very attractive. possibility overcome Betz limit power coefficient was widely horizontal axis turbines. However, few studies have dealt with Savonius rotor despite these represented an efficient thanks their simplicity, cheapness low cut velocity highly turbulent conditions as well. Furthermore, concept, might applicable oscillating water column wave energy devices, its self-rectifying capability simplicity. For reasons, authors carried out experimental campaign verify impact ducting rotor, thus leading way a possible exploitation many practical applications. Specifically, present paper deals study type air performance. In particular, performance studied function overlap ratio. Four ratios were tested: 0, 1/6, 1/3 1/2. A specific setup built test turbine, while bare measured using tunnel. All tests performed at fixed velocity: 5 m/s. On basis results, it state that higher than performance, all tip speed ratios. optimal ratio equal 1/3.