Solidity Effects on Small Hybrid Savonius-Darrieus Wind Turbine Performance: Experimental Analysis with NREL S809 Airfoil

This experimental study uses the NREL S809 airfoil to evaluate how solidity affects the performance of a hybrid Savonius-Darrieus wind turbine. To assess its effects on power coefficient, starting torque, and other performance metrics, solidity is varied with values of 0.5, 0.75, and 1. The model is made using 3D printing with PLA material and has internal and external rotor radii of 5cm and 10cm, respectively. The experiments are conducted in a wind tunnel with a testing chamber cross-sectional area measuring <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30x30</tex> cm between 3–12 m/s of wind speed variation. Overall, the model with a solidity of 0.75 demonstrates the best performance, showcasing both favorable initial torque and the highest maximum power coefficient of 0.33 at TSR 2.1.