Optimization of Lenz-Type VAWT Geometries with Computational Fluid Dynamics

Abstract

The renewable energy industry is evaluating vertical axis wind turbines (VAWT) because they are operable in both turbulent and omnidirectional wind conditions and maintain a smaller physical footprint than traditional turbines. However, most traditional VAWT designs generate significantly less power than a corresponding horizontal axis wind turbine (HAWT). VAWTs will also typically start generating power at lower wind speeds than HAWT. In this work computational fluid dynamics and wind tunnel experiments have been used to investigate the tradeoff between high mechanical energy production and low starting wind speeds. The design space is explored using a genetic algorithm approach. Several key finds were gathered through the optimization, modeling, and validation process. It is shown that, although discrepancies are seen between the computational and experimental data, the approach described allowed for general trends to be captured allowing for design optimization. Two key values are targets, a positive coefficient of torque which indicates that wind that can overcome the losses in the system will create positive rotation, and coefficient of power, which is an indication of the efficiency of power generation. The best design at the time of this paper’s publication is a rotor with five “J” shaped blades, which achieves an uncorrected maximum power coefficient of 0.347 and a minimum torque coefficient of 0.42 when measured in a wind-tunnel.