Power improvement of a cluster of three Savonius wind turbines using the variable-speed control method

Abstract

The average power output of multiple Savonius wind turbines optimally arranged in a cluster is improved significantly compared to that of an isolated turbine due to the coupling effect. Previous investigations focused on the influence of the configuration and the initial phase angles of Savonius turbines operating at the same rotational speed in a cluster. This paper proposes to adopt the variable-speed control method to improve the power output of a three-turbine cluster, and simultaneously avoid the requirement for the accurate initial phase angle settings of the turbines. The Taguchi method is used to optimize the configuration of the cluster. The distances between the centers of adjacent turbines (L1-2, L1-3), the configuration angles (θ1-2, θ1-3), and the combination of rotational directions (RD) are taken as Taguchi experimental factors. The optimal configuration of the cluster is determined to be L1-2 = 2.0D, L1-3 = 2.4D, θ1-2 = 110°, θ1-3 = 110°, and RD = (-,+,-). The influence strength of the factors is ranked as configuration angle, RD, and distance between turbines. In addition, the average power coefficient of the turbines in the optimal cluster is 1.425 times that of an isolated turbine and the tip speed ratios of the three turbines are 1.13, 1.14, and 1.09.