Effect of solidity on aerodynamic performance of vertical axis wind turbines

Vertical axis wind turbines (VAWTs) are promising for wind energy harvesting in the urban environment mainly because of their omnidirectional capability. However, currently their aerodynamic performance is not comparable with horizontal axis wind turbines (HAWTs). Therefore, to make them an ideal candidate, they need to be further improved. The aerodynamic performance of VAWTs depends on several geometrical parameters, such as solidity. However, the impact of solidity on blade aerodynamics and turbine wake has not yet been comprehensively investigated. Therefore, the current study intends to systematically study the effect of solidity on aerodynamic performance of VAWTs with different number of blades operating at various tip speed ratios to provide a deeper insight into its impact on dynamic loads on blades, turbine performance and wake. High-fidelity unsteady Reynolds-averaged Navier-Stokes (URANS) simulations extensively validated with experimental data are employed. The results show that for fixed-rotational-speed urban VAWTs, which frequently operate at high tip speed ratios, a low solidity value is more favorable. On the other hand, an optimal VAWT is a high-solidity variable-rotational-speed (fixed λ) rotor operating at a low tip speed ratio regime.