Blade Offset and Pitch Effects on a High Solidity Vertical Axis Wind Turbine

Abstract

A high solidity, small scale, 2.5m diameter by 3m high Vertical Axis Wind Turbine (VAWT) consisting of three NACA 0015 profile blades, each with a span of 3m and a chord length of 0.4m, was tested in an open-air wind tunnel facility to investigate the effects of preset toe-in and toe-out turbine blade pitch. The effect of blade mount-point offset was also investigated. The results from these tests are presented for a range of tip speed ratios, and compared with an extensive base data set obtained for a nominal wind speed of 10m/s. Results show measured performance decreases of up to 47% for toe-in, and increases of up to 29% for toe-out blade pitch angles, relative to the zero preset pitch case. Also, blade mount-point offset tests indicate decreases in performance as the mount location is moved from mid-chord towards the leading edge, as a result of an inherent toe-in condition. Observations indicate that these performance decreases may be minimized by compensating for the blade mount offset with a toe-out preset pitch. The trends of the preset blade pitch tests agree with those found in literature for much lower solidity turbines.