Aerodynamic Optimization of Vertical Axis Wind Turbine with Trailing Edge Flap

Abstract

Vertical Axis Wind Turbines (VAWT) are competitive concepts for very large scale (1020 MW) floating offshore applications. Rotor circulation control (loading control) opens a wide design space to enhance the aerodynamic and operational features of VAWT. The modified linear derivation of the Actuator Cylinder Model (Mod-Lin ACM) is used as the aerodynamic model to assess VAWT performance throughout the work. As the first step, optimum aerodynamic loadings of a VAWT with infinite number of blades are studied. Next, for the case of finite number of blades, direct and inverse optimization approaches are used. The direct method is coupled with a hybrid numerical optimizer to serve as a global method for designing flap sequences. The effectiveness of trailing edge flap on VAWT is investigated for three aerodynamic objectives which lead to improved power efficiency, rated power control and peak load control. The aerodynamic gains for various solidity, tip-speed ratio, maximum flap deflection and flap size are quantified in inviscid flow. This extensive work presents new insights on the performance of a VAWT with infinite number of blades as well as it provides a solid foundation for flap usage on a real VAWT rotor to enhance its capabilities.