Advanced blade profiles for improved efficiency in Savonius wind turbines: the aeroleaf case study

The Aeroleaf, a Savonius-based vertical-axis wind turbine (VAWT) designed for urban environments, is compact and omnidirectional but limited in aerodynamic efficiency. In this study, the baseline Aeroleaf was compared with a conventional Savonius wind turbine (CSWT) under identical Reynolds number conditions (Re ≈ 1.7 × 10⁵, U = 7 m/s). The Aeroleaf achieved a peak Cp of 0.107 at TSR of 0.5, while the CSWT reached Cp = 0.120 at TSR = 0.8, confirming that although the Aeroleaf operates optimally at lower TSRs (advantageous for low-wind startup) its maximum efficiency is 11% lower than the CSWT. Static torque analysis further showed that the Aeroleaf produced 0.301 N·m at α = 90°, demonstrating good startup potential but limited aerodynamic output. To address these shortcomings, four optimized blade profiles (scooplet, S-shaped, Roy, and elliptical) were integrated into the Aeroleaf's three-dimensional structure and evaluated through unsteady CFD simulations. Among these, the scooplet profile delivered the strongest improvement, achieving Cp = 0.180 at TSR = 0.6 and static torque of 0.443 N·m, corresponding to 68.2% and 47% gains over the Aeroleaf baseline. The S-shaped, Roy, and elliptical profiles achieved peak Cp values of 0.159, 0.132, and 0.124 with static torques of 0.317, 0.350, and 0.420 N·m, respectively. Dynamic torque-azimuth analysis confirmed the same order of performance, with the scooplet reaching the highest peak torque of 1.2 N·m and the largest average torque. These findings demonstrate that optimized blade profiles, especially the scooplet, overcome the Aeroleaf's aerodynamic limits, improving efficiency and startup for reliable small-scale urban wind energy.