EXPERIMENTAL INVESTIGATION OF A NOVEL SAVONIUS TURBINE WITH PARTIALLY FLEXIBLE BUCKETS

Savonius wind turbines, due to their drag-based operation, generally exhibit low aerodynamic efficiency, prompting ongoing efforts to improve their performance in low-wind-speed environments. This study investigates the use of partially flexible buckets, featuring passive morphing fabric sections, to enhance torque generation and power output without increasing mechanical complexity. Flexible bucket geometries were characterized using two dimensionless parameters: the Sagitta Ratio (SR), describing surface curvature, and the Flexible Ratio (FR), representing the deformable region’s span. A series of experimental tests were conducted in an open-jet wind tunnel under controlled conditions, comparing flexible configurations to a rigid baseline across varying tip speed ratios (TSRs).Results show that all flexible designs retained self-starting capability, with performance highly dependent on the SR–FR combination. The optimal configuration (SR = 0.2, FR = 0.5) achieved a peak power coefficient (Cp) of 12.9%, surpassing the rigid reference Cp of 12.2%, and reached steady-state rotation in 24.8 seconds, faster than the 28.3 seconds required by the rigid turbine. These findings demonstrate that judicious use of passive flexibility can enhance Savonius turbine performance while preserving simplicity and structural integrity. The study offers a viable path toward low-cost, scalable wind energy solutions for decentralized and urban applications.