Experimental investigation of solidity and blade profile effects on H-Darrieus wind rotor: Performance and self-starting analysis

The present study investigates the impact of rotor solidity and blade profile on the self-starting characteristics and performance of H-Darrieus wind rotors (H-rotors) through subsonic wind tunnel experiments. Three symmetrical (NACA 0018) and three unsymmetrical (NREL S823) H-rotors were analyzed to determine the coefficient of static torque (Cts) and coefficient of power (Cp) across three solidities (σ = 0.25, 0.3, and 0.35) and two free stream wind speeds (Uf = 6 and 8 m/s). The findings revealed that the NREL S823-bladed H-rotor outperformed the NACA 0018-bladed H-rotor, displaying 13% and 11% higher Cts values at σ = 0.25 (Uf = 6 and 8 m/s), 9% and 9% at σ = 0.3 (Uf = 6 and 8 m/s), and 13% and 11% at σ = 0.35 (Uf = 6 and 8 m/s). The NREL S823-bladed H-rotor achieved a maximum Cp of 0.197 at σ = 0.3 and Uf = 8 m/s, which is 6% higher than the maximum Cp obtained by the NACA 0018-bladed H-rotor. Furthermore, the trend of maximum Cp values for both H-rotors followed the order of Cp, max σ = 0.25 < Cp, max σ = 0.3 > Cp, max σ = 0.35. Based on the experimental findings, it is inferred that the NREL S823-bladed H-rotor with a solidity of 0.3 is suitable for small-scale wind turbines.