Efficiency of a small wind turbine using BEM and CFD

Abstract

The wind turbine is a mechanism which converts the mechanical energy to an electrical energy. The aerodynamic efficiency of the wind turbine is defined by the kinetic energy captured from the wind. A higher aerodynamic efficiency depends only on the design of the rotor blades. Theoretically, this efficiency (which is known by the power coefficient) is restricted by the Betz-Joukowski limit. Generally, to evaluate the power coefficient of a wind turbine, the Blade Element Momentum theory (BEM) have been used because it is fast and gives accurate results. In this work, a design of a small wind turbine is presented. The evaluation of the power coefficient of this wind turbine is estimated using the BEM theory. In order to minimize time and cost generated by the experimental tests, a computational fluid dynamic (CFD) approach is adopted to estimate the efficiency of the wind turbine. This method simulates the flow around the rotor blades to estimate the pressure and velocity distributions of the airflow, and then the aerodynamic performance. This CFD method can be conducted using many models (inviscid, laminar, k-w model, and Spalart Allmaras). In order to find the best model that should be used, a 2D simulation of the airflow around an airfoil validated experimentally was performed using Fluent. Then, the established methodology would be adopted for a 3D simulation of the airflow around the rotor. The results obtained were satisfactory and accurate compared to the results given by the BEM theory.