Aerodynamic optimization to improve the starting torque of a 1 kW Savonius-Darrieus Vertical Axis Wind Turbine

Abstract

This work presents a series of gradual improvements to reduce the starting torque of a 1kW capacity of the Savonius–Darrieus Vertical Axis Hybrid Wind Turbine Rotor. The improvements start from a design configuration of a wind turbine with at cut-in wind speeds of 7 m/s and an aerodynamic torque of 6 N-m. These improvements include the implementation of curved fins on the Savonius rotor, asymmetric profiles on the Darrieus rotor, direct coupling of the power train to the hybrid rotor and finally the increase of the tower height up to 2m without compromising maintenance operations. The results showed satisfactory operating parameters since the cut-in wind speed was reduced by 50% with respect to the original configuration, reaching values of 3.3 m/s, while the starting torque value had a decrease of 40% reaching a low value of 3.5 N-m. These improvements significantly increase the use of wind resources in urban environments where wind speeds do not exceed 6 m/s.