Improving Savonius turbine efficiency with splitter and barrier cylinder deflector design: A Taguchi method study

Abstract

Vertical axis wind turbines are wind turbines with the rotor axis perpendicular to the ground, designed to harness wind energy for electricity generation. The primary cause of low-efficiency Savonius turbines is the negative torque contribution from the returning blade. A Savonius turbine is a type of turbine characterized by its rotational direction orthogonal to the passing fluid flow and the flow interaction with advancing and returning blades, generating torque primarily through drag forces. Thus, the study proposes a novel design of a cylindrical deflector with splitters and a barrier to offset the flow field to the returning blades. This study aims to maximize the efficiency of conventional Savonius turbines using the cylindrical deflector with splitters and a barrier via a combination of computational fluid dynamics simulations and the Taguchi optimization method. The Taguchi method is used to determine the best combination of specified characteristics such as the length of the barrier (Ls/D), the barrier attachment angle (α), and the geometric shape of the cylinder deflector with a splitter and a barrier. The tip speed ratio (λ) for this study is fixed at λ = 1. The simulations and additive model revealed that the optimal combination in this study is a cylinder deflector with double wake splitters positioned at the top and middle of the deflector. The deflector is oriented parallel to the flow, and a barrier placed at the bottom of the deflector is oriented orthogonal to the flow. The optimal configuration has Ls/D ratio of 0.9 and a barrier attachment angle (α) of 10°. Therefore, the ideal combination was found to produce a power coefficient equivalent to 0.459, indicating that the performance of Savonius turbines increases by around 61% compared to previous studies.