A direct method for evaluating performance of horizontal axis wind turbines

This paper presents a direct approach for the determination of aerodynamic performance characteristics of horizontal axis wind turbines. Based on Glauert's solution of an ideal windmill along with an exact trigonometric function method, analytical closed form equations are derived and given for preliminary determination of the optimum chord and twist distributions. The variation of the angle of attack of the relative wind along blade span is then obtained directly from a unique equation for a known rotor size and refined blade geometry. A case study including the analysis of an existing turbine model is given and results are discussed and compared with those obtained by other investigators. It is shown that the approach used in this study is efficient and saves much of the computational time as compared with the commonly used iterative procedures.