Improving energy extraction in VAWT clusters: effect of blade count, wake synergy, and inter-turbine spacing

Abstract This study investigates the performance characteristics of vertical-axis wind turbine (VAWT) clusters, with a particular focus on the influence of blade count on system efficiency. To evaluate the cluster performance across various configurations, high-fidelity numerical simulations are conducted using a coupled approach that integrates large eddy simulation (LES) with the actuator line method (ALM). The number of blades per turbine is systematically varied from two to seven, and the resulting impact on the power output of a three-turbine cluster is analyzed. The results show that, in contrast to the conventional preference for three-bladed turbines, four-bladed turbines perform better in the cluster arrangement. This improvement is attributed to enhanced kinetic energy interactions in the turbine wake, leading to more effective energy extraction across the cluster. This observation remains consistent across a range of incoming wind directions. Furthermore, the study examines the impact of turbine interspacing on cluster performance and finds that an inter-turbine spacing of 2.5 times the rotor diameter (2.5D) yields better performance than the commonly used 3D spacing. The analysis highlights that critical parameter including blade number, turbine rotational direction, and the spatial configuration within the cluster collectively contribute to the overall power coefficient of the system. These findings provide valuable insights for the design and optimization of VAWT clusters, with implications for improving the efficiency and sustainability of wind energy harvesting.