Numerical investigation of the power and self-start performance of a folding-blade horizontal axis wind turbine with a downwind configuration

This study proposes an oblique folding mechanism design inspired by the wings of Borneo camphor seeds to enable the blades of wind turbines to pitch and cone. The blade pitching increases the power output, while the blade coning reduces the blade root stress and increases the yaw stability of the wind turbine. Numerical predictions of the power and self-start performance of a downwind folding-blade horizontal axis wind turbine were conducted. For comparison, a benchmark wind turbine with a constant chord blade section with an SD8000 airfoil and zero blade twist was also modeled. The maximum power coefficient (C_P) of the folding-blade wind turbine is 0.404 which is 28.22% higher than that of the benchmark wind turbine, when the fold axis angle is 50° and the pitch angle is 3.834°. The maximum starting torque of the folding-blade wind turbine is 0.720 Nm at a pitch angle of 64.59°, which is 1153.97% higher than that of the benchmark wind turbine. This finding confirms that a folding blade can increase the power output, start-up capability and passive yaw capability of a wind turbine. In conclusion, the proposed folding design can be adopted as an alternative for pitching and coning wind turbine blades.