Design of a variable-pitch vertical-axis wind turbine with embedded resilient biasing device inside an aerofoil

This study addresses the design of a vertical-axis wind turbine (VAWT) by introducing a novel passive pitch mechanism. Traditional VAWTs, while advantageous for urban environments due to their simple design, omni-directional operation, and low cut-in wind speeds, often suffer from low starting torque and poor self-starting capabilities. To overcome these issues, a recently patented resilient biasing device was integrated into the blade's aerofoil. Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) were employed to enable the design, prototype, and test of the blade. The CFD simulations predicted aerodynamic forces, which were then used in FEA to assess structural deflections. The key findings from wind tunnel tests of the prototype blade show a logarithmic correlation between wind speed and pitch angle. The novel resilient biasing device acting as a torsional spring effectively returned the angle of attack to zero after force removal. The wind tunnel test results demonstrated that the pitch angle can be changed under wind load, hence leading to potential improvements in starting torque and self-starting capabilities. The results validate the concept of embedding a resilient biasing device for passive pitch control, paving the way for optimizing passive pitch mechanisms to enable the self-starting ability and overall efficiency of VAWTs.