Aerodynamic performance analysis of small wind turbine blades using NREL S809 profile and various tip speed ratios.

Abstract

One of the main factors that influence the operation and efficiency of wind generators is the aerodynamic performance. Therefore, the rotor blades are the primary target of this study. They are the aerodynamic components that interact directly with the air flow for the transformation of kinetic energy of the wind into electrical energy. This work proposes the design, build and testing the blades of a small wind turbine. The rotor was built with 3.0 m diameter, equipped with three blades using the airfoil NREL S809 profile. The blades were developed according to the BEM (Blade Element Momentum) theory, resulting in geometry of maximum aerodynamic performance. Four distinct sets of blades were used in the performance tests; they differ from each other by the value of the tip speed ratio. The values applied were equal to 6, 7, 8 and 9. In the tests, it was found a little dependence on the measured torque as a function of the specific speed operation, which is a characteristic of the high-speed wind turbines. The test results reveals that the blade with tip speed ratio 7 showed the best average performance, obtaining a maximum coefficient of performance equal to 31%.