Assessment of solidity effect on the power performance of H-rotor vertical axis wind turbines in turbulent flows

Recent research suggests that vertical axis wind turbines (VAWTs) are suitable for urban installations. Nevertheless, systematic investigation of the power performance of VAWTs operating in flows of various turbulence levels remains limited. This study presents the influence of solidity on the aerodynamic performance of H-rotor VAWTs immersed in turbulence via wind tunnel tests. Homogeneous turbulence of various levels was generated by a wooden grid. A turbine control system was used to tune the blade speed ratio (BSR) and measure the rotational speed and torque. The relationship between the turbine's power coefficient, C_P, and BSR, λ, was examined at different turbulence levels, I. Further, the impact of changes in the solidity ratio, σ, on the C_P-λ curve was investigated. The analysis results show that the C_P value of the turbine in turbulent flows was, on average, two times that of the one in smooth flow. However, a simple relationship between the increase in turbulence intensity and the increase in power performance of the wind turbine cannot be concluded. It was also observed that the turbine with a higher solidity obtained a larger rated C_P, irrespective of flow regimes. Moreover, the turbine with a medium solidity ratio, σ = 0.45, was able to produce power over a broader range of BSRs than the one with low/high solidity in turbulent flows.