Numerical analysis of off-axis wind and passive yaw control of an opposing airfoil paired motionless wind energy system

Abstract

• Safe, low-noise, and rooftop-integrated wind energy harvesting. • Innovative airfoil pairing optimized for urban wind conditions. • Turbine performance sharply declines at wind angles exceeding 15°. • The NACA0012 airfoil-shaped tail vane outperformed others. The energy extraction from urban wind at small-to-medium scale is limited due to lower performance and high capital cost of wind energy systems. This study aims to optimize the passive yaw control mechanism of a motionless wind energy system utilizing opposing S1210 airfoils, focusing on enhancing alignment with variable wind directions. A computational fluid dynamics (CFD) framework evaluates five tail vane designs NACA0012, triangular, trapezoidal, arrow, and rounded to assess their aerodynamic performance in generating lift, minimizing drag, and producing turning moments for self-alignment. Results demonstrate that the NACA0012 airfoil-shaped vane achieves superior efficiency, balancing high lift (15 % greater than alternatives) and low drag, enabling robust turbine orientation even at wind speeds of 8 m/s. However, off-axis wind angles exceeding 15° degrade performance drastically, reducing the coefficient of performance (COP) by 26 % and 81 % at 20° and 25°, respectively, highlighting the importance of passive yaw control. The findings contribute to optimizing the paired airfoil wind energy system for improved performance in urban wind conditions. The study concludes that integrating streamlined tail vanes, such as the NACA0012, significantly enhances the viability of motionless wind turbines for urban deployment, offering a cost-effective solution to harness low-to-medium wind speeds with minimal maintenance.