Maximizing efficiency with active diameter modulation of vertical axis wind turbine

Abstract

Wind turbines rely heavily on prevailing wind conditions, yet the dynamic nature of wind often limits the efficiency of turbines with fixed dimensions. While previous research has explored variable concepts such as pitch angle, deformable aerofoils, etc., studies on variable solidity are scarce. This study proposes a novel variable diameter vertical axis wind turbine (VD-VAWT) designed to dynamically adapt to varying tip speed ratios (TSR), enhancing performance and expanding its wind capture range. This VD-VAWT comprises a special mechanism design that enables the turbine blade to slide along the strut. Experiments were conducted on a VD-VAWT with two straight-bladed NACA0018 aerofoils. Initially, the fixed diameter experiments spanning 300 mm to 800 mm were conducted which identified 600 mm as the optimal diameter, achieving a maximum power coefficient (C_{P, max}) of 0.2748. The active control VD-VAWT demonstrated significant performance improvements, with power yields surpassing fixed diameter turbines by 34 % at 600 mm and 68 % at 800 mm. While changing its diameter, it can maximize the C_P at different TSRs. In addition, the VD-VAWT enhanced self-starting capabilities, dynamic self-regulation for optimal conditions, and potential storm protection. This innovation demonstrates the potential of adaptable turbines to achieve higher efficiency and versatility in fluctuating wind conditions.