Investigating Efficient Clusters of Savonius Wind Turbines

Abstract

The wake effect is the biggest challenge when locating downwind turbines in wind farms which imposes large separation distances between turbines. In the present work, CFD simulations are presented to study possible configurations of wind farms of Savonius wind turbines. The farm is composed by in steps, starting from two-turbine configuration, adding one turbine until reaching a cluster of closely set ten rotors with an average power coefficient of 0.225. This value is very close to the single rotor’s power coefficient. The power density of the cluster is 7.55 W/m2 which is much higher than similar ten turbines located far apart to avoid wake effect. The maximum Cp of a downstream rotor in the cluster reached 0.323 which is about 40% higher than the single rotor. The adopted philosophy for placing downstream rotors is locating the rotor’s returning bucket in the low velocity region of the wake of the upstream rotor to get the least negative torque while the advancing bucket is located at the high velocity region getting higher positive torque which increases the performance. After that, two crosswind clusters are added to increase the power generated. The predicted average power coefficient for the 30 rotors farm is 0.246 which is higher than a similar isolated turbine. The increase of the Cp occurs due to the positive interactions between the clusters. The highest Cp in the farm rotors is found to be 0.411 which is higher than the single rotor’s Cp by 78%. The farm also provides a high power-density of 4.65 W/m2 which is 5 times higher than a farm with the same number of turbines located far apart.