Effect of Flexible Rotor Bucket Design on Savonius Turbine Performance

Abstract

Savonius wind turbines are simple and robust devices suitable for a variety of climate conditions. Due to their low noise emission, they can be used in urban areas close to end users. However, their biggest drawback is their relatively low aerodynamic performance. One solution to this challenge is to use flexible rotor buckets. Public literature has shown that a wing’s aerodynamic performance can be improved by introducing flexible material; however, this idea has not been widely studied in the case of a Savonius turbine. Therefore, this work presents an experimental and analytical study determining how turbine performance is affected by the flexibility of the rotor bucket. In particular, the effect of the leading edge design is examined. In total, three rotor designs are studied in a continuously operated wind tunnel to reveal the effects of rotor design on the rotational speed and rotor deformation at different flow velocities. In addition, a correlation is developed to predict the turbine power coefficient under the measured operating conditions. The results suggest that a flexible membrane bucket can improve the performance of a Savonius turbine compared to a conventional rigid design. It is also found that the amount of leading edge flexibility can affect the optimal operating range. High-speed camera studies provide further insights into the bucket deformations during the operation of different rotor designs.