Numerical investigation and experimental validation about negative overlap in Savonius hydrokinetic turbine

Conventional hydroelectric turbines use the potential energy of the water as a primary source of energy. However, the hydrokinetic turbines use the kinetic energy of the flowing water to generate power output. It is also one of the best clean energy generation technologies. Out of many hydrokinetic turbines, the Savonius hydrokinetic turbine is very simple in design and easy to manufacture. The ratio of the gap between the two vanes to the turbine diameter is known as the overlap ratio. The effect of the positive overlap has been extensively investigated for the Savonius turbine. However, for the first time in the present investigation, the effect of the negative overlap ratio on the hydrodynamic performance of the Savonius turbine is investigated. The highest value of negative overlap ratios is obtained for two, three, and four numbers of blades of Savonius hydrokinetic turbines. With the present investigation, the best-suited range of the negative overlap ratio is obtained for each case. The present investigation also concludes that the Savonius turbine with three and four vanes, with a negative overlap ratio, maintains its good performance for a wide variation in the turbine load. Also, the best-obtained design through numerical analysis was cross-verified by experiments.