An experimental investigation into performance characteristics of H-shaped and Savonius-type VAWT rotors

Abstract

The effects of flow regime and rotor configuration strongly influence the power performance of vertical axis wind turbines (VAWTs). Yet, there exits few experimental investigations from literature that have been carried to explain this effect. This could be attributable to huge wind tunneling cost requirement and an array of design skills required including time constrains. The balance between cost and power performance has limited development of VAWTs towards utility scale type. In this paper therefore, we seek to investigate in detail the performance characteristics of vertical axis wind rotors in a wind tunnel environment. The H-Darrieus and Savonius-type VAWT configurations have been utilized to carry out the investigation. A systematic analysis of effect of blade number, rotor configuration, and flow regime including comparison of the two configurations was presented to predict the power performance using a rotary sensor. Results revealed a significant impact of flow field regime on power performance of the VAWT models, with the Savonius-type rotor attaining lower power coefficient (CP) than the Darrieus-type rotor across all the tested wind speeds. In addition, increase in number of blades for Darrieus-type rotor revealed narrower negative CP band that decreased with increase in wind speeds. In both configurations, the CP decreased at low tip speed ratios while an increase in CP was revealed at high tip speed ratios. The understanding gained from the results could be useful to the VAWT research community, and the findings can be extended to the design of wind turbines for mini-grid and utility scale applications.