Circulation Control Applied to Wind Turbines

Abstract

The recent rise in fuel costs and global warming concerns have re-invigorated the search for alternative energy sources. Harnessing energy from the wind is a logical alternative; however the cost and efficiency of current wind turbines is a limiting factor. The use of an augmented Vertical Axis Wind Turbines (VAWTs) may become the superior choice to the more common Horizontal Axis Wind Turbines (HAWTs) that are usually associated with the harvesting of wind energy. HAWTs operate on the same principles as large airplane propellers, while VAWTs operate on lift and/or drag principles like an airplane wing or a sail on a boat. VAWTs are currently being investigated for use with circulation control to increase their potential power output. In this paper, two topics will be presented, a comparison between VAWTs and HAWTs for rotor diameter versus key turbine aspects and the impact of VAWTs on environmental concerns, such as bat and bird populations. The Center for Industrial Research Applications (CIRA) at West Virginia University (WVU) is currently developing a concept utilizing circulation control to increase the lift to drag ratio, maximizing the beneficial forces on the VAWT blade, allowing for improved wind energy production. For the comparison between VAWTs and HAWTs, there are currently 14 companies with a total of 34 wind turbines variations representing VAWTs and 11 companies with a total of 40 wind turbines representing HAWTs. Trend studies of VAWT and HAWT diameters to cut-in-speed, rated velocity, max velocity, power output (<100 kW), and power output (≥100 kW) were created to show the potential of VAWTs. A growing concern with wind energy is the impact on bat and bird populations. It is currently believed that VAWTs reduce the impact of wind energy by altering the interaction with the wind. If these benefits can be proven, then not only are VAWTs potentially more economical, but even more eco-friendly.