Positive interactions of two Savonius-type vertical-axis wind turbines for performance improvement

Abstract

Abstract The performance of multiple vertical-axis wind turbines (VAWTs) can be greatly enhanced when they are placed close in some configurations where positive interaction or coupling occurs. Based on a systematic study using computational fluid dynamics (CFD) simulations, we investigate the positive coupling of two co-rotating Savonius-type VAWTs. A wide range of configurations are covered, i.e., P/D = 1.2−3.0 and α = -90°−90°, where P is the distance between the turbines’ centres, D is the diameter of turbine rotation, and α is the incident angle between the line connecting the turbines’ centres and incoming wind’s direction. It is found that the time-averaged power coefficient of the upstream turbine can be significantly improved by up to 60% at (P/D, α) = (2.2, 80o), compared to that of a single, isolated turbine. For the two-turbine system, the overall power coefficient can be increased by 40% over that of a single, isolated turbine. Typical configurations corresponding to different positive couplings of the two turbines are identified. The behaviour of torque on the individual turbines and the associated flow structures are discussed.