Improving Vertical Axis Turbine Performance with Active Blade Pitch Control: Mechanism Design and Fundamental Physics Analysis

Abstract

Compared to their horizontal counterparts, vertical-axis turbines (VATs) have several advantages, such as low manufacturing, installation, operation and maintenance costs, low noise emission, and are less harmful to birds and insects. In this study, we propose to develop active turbine blade pitch control methods to conquer the challenges encountered by the VAT technology. There are many control approaches that offer performance improvements. This thesis explores the potential performance improvements that the constant angle of attack (AoA) control function offers. The constant AoA function was developed to facilitate implementation into a real turbine. To validate the new control approach ANSYS-Fluent was used to simulate the 2D VATs at different Tip Speed Ratios (TSRs) and wind speeds (WS)to better understand the scope of performance improvement of this control. To understand capability of the control, flow physics is studied for different constant AoA control strategies across a wide range of TSR and WS. The individual behavior of a constant AoA case was investigated using the torque coefficient graphs and the instantaneous velocity flow fields. These efforts gave invaluable insight into the fundamental physics that governed the turbine?s performance and how the control affected the fluid. The overall effect that an individual control case had on the performance of the turbine was analyzed using the power coefficient (CP ) graphs. The comparison between the best performance of the control function and that of the no control baseline ranged from an increase in the CP , a measure of energy harvesting efficiency, of 27.4% to 704.0%.