On the Effect of Altitude on the Performance of a Small Wind Turbine Blade

Abstract

This study deals with the effect of the altitude on the performance of a Small Wind Turbine (SWT) blade. Four potential regions of wind energy with altitudes up to 3,000 m were selected and a three-bladed, 2 m diameter small HAWT was designed for those regions. Starting time was combined with output power in an objective function to improve the performance of the turbine at low wind speeds. The goals of the objective function, the output power and the starting performance, were addressed by geometry optimization of the blade which was carried out by the genetic algorithm. The modified Blade-Element Momentum (BEM) theory was applied to calculate the output power and starting time. Results show that the performance of an optimal blade which was optimized for operating at sea level degrades for other regions. That degradation is more important for the starting performance in comparison with the reduction of the power coefficient. To improve the performance of the blade in the considered regions, two redesign procedures were carried out. First, the geometry of the blade was optimized respect to the air density of the regions which led to increase of the power coefficient and the starting time. Much more power was achieved using the second approach in which the tip speed ratio was added to the geometry of the blade as an additional design variable. Results also indicate that the generator resistive torque remarkably puts off the starting of the turbine especially at very high altitudes.