Wake Recovery in Downwind Wind Turbines

Creating a turbine design that allows for more economical and energy efficient farms will positively impact the wind energy industry. Downwind turbines are less susceptible to blade-tower collisions which could allow for larger, lighter, and more flexible blade designs. The potential of downwind turbines to increase power production compared to an upwind design are considered as well as the possibility for a tighter grid configuration. Unlike upwind configurations, the impact of tower wake on the overall efficiency and power production needs to be considered. These experiments were performed in the wind tunnel at Portland State University. Upwind and downwind configurations of scaled wind turbine models were compared to evaluate their wake recovery at wind speeds ranging from 3 m/s to 12m/s in an active grid with turbulent flows. Two camera stereo particle image velocimetry (PIV) were used to visualize and measure flow behavior. Mean velocities and Reynolds stresses were measured through the use of PIV; accessing three components of velocity over two planes. Power was measured through generators mounted in the hub of the turbines and power curves were developed. The measured data obtained from the experiments includes power, mean velocities, and turbulent Reynolds stresses.