Application of a Vortical Stator Assembly to Augment the Rotor Performance of Drag-Type Vertical-Axis Wind Turbines

A vortical stator assembly (VSA), surrounding a drag-type, vertical-axis wind turbine, was developed to improve rotor performance. The VSA consisted of six guide vanes, which were to guide the air tangentially into the VSA. The design concept was to generate a vortical flow inside the VSA, to reduce the negative torque of the returning rotor blade, and to increase the air speed into the rotor. Wind tunnel tests were conducted to study the VSA effects on rotor performance. Results show that the VSA significantly increased rotor performance. The augmentation ratios of the rotor power outputs with the VSA were between 8.33 and 13.62 under the investigated wind speeds between 4 m/s and 8 m/s, and wind directions between 0 degrees and 50 degrees. The diameter of the rotor integrated VSA increased by less than 87.5%. A yaw mechanism was not required because the power augmentation with the VSA was significant regardless of wind direction. Results also show that the rotor starting speed was reduced to approximately 1 m/s.