Rotor solidity effects on the performance of vertical-axis wind turbines at high Reynolds numbers

Abstract

Vertical Axis Wind Turbines have yet to see wide-spread use as a means of harvesting the kinetic energy of the wind. This may be due in part to the difficulty in modeling the relatively complex flow field and hence performance of these units. Additionally, similar to Horizontal Axis Wind Turbines, VAWTs are difficult to properly test in a conventional wind tunnel. Typically Reynolds numbers cannot be matched or the turbine geometry must be altered, limiting the applicability of the results. Presented in the following is a set of experiments in a specialized, high-pressure wind tunnel used to achieve high Reynolds numbers with a small-scale model. The performance change of this model is investigated at two different solidities and over nearly a decade of Reynolds numbers (based on diameter: 600, 000 ≤ ReD ≤ 5 × 106). The non- dimensional power coefficient displays behavior consistent with Reynolds number invariance, regardless of solidity. In addition, the change in performance as this limit is approached also shows no direct dependence on the solidity for the VAWT geometry used in this study. The results of this work have direct application for modeling and simulation efforts concerning the performance of new VAWT designs.