Performance Analysis of H-Rotor Vertical Axis Wind Turbine

Abstract

Angle of attack is a well-developed and widely-used approach in modern horizontal axis wind turbines in operation. However, its application in vertical axis wind turbines (VAWTs) is restricted by the ambiguities in its functional mechanism. A generic formulation that uses governing parameters to represent the solution space of the optimal angle of attack control is developed through an in-depth analysis of the relationship between angle of attack and the output torque of VAWTs. Subsequently, a single tube stream model, multiple tube stream model composed of genetic algorithm and MATLAB SIMULINK simulation modules is built to search for angle of attack that can maximize turbine torque. A MATLAB SIMULINK model is used as a performance evaluation tool because of its high computational efficiency. Results show that in a wide range of tip speed ratios (TSRs), the angle of attack and torque coefficient can increase respectively, in two simulated VAWT models with different two stream tube. At stages below the rated TSR, stall induced torque losses are delayed or even avoided by the proposed optimized angle of attack control. At stages beyond the rated TSR, energy extraction in the downwind zone is improved due to increased upwind wake velocity.