High-solidity straight-bladed vertical axis wind turbine: Aerodynamic force measurements

Vertical axis wind turbines (VAWTs) have many advantages over horizontal axis wind turbines (HAWTs), but due to the lack of knowledge of complicated aerodynamic mechanisms, the power generation of VAWTs is lower per equivalent area. The detailed experimental investigations are therefore highly recommended to understand the aerodynamic mechanisms of blades of a VAWT. This study performs direct measurements of aerodynamic forces on the blades of a high-solidity straight-bladed VAWT in a wind tunnel. The wind turbine and measurement system are presented in detail. A series of wind tunnel tests were carried out to investigate the effects of azimuth angle, tip speed ratio, inflow wind speed and blade chord width on the aerodynamic (both tangential and normal) forces of the blades. The wind tunnel test results demonstrate that the measurement system developed in this study is capable of providing aerodynamic forces with adequate accuracy. The measurement results show that the high-solidity straight-bladed VAWT has better self-starting performance and can achieve higher power coefficient at lower tip speed ratios, which enable them to work at low rotational speed conditions. Nevertheless, high-solidity adds the complexity to the flow field around blades at lower tip speed ratios.