Geometric Optimization of Savonius Vertical-Axis Wind Turbines Using Full Factorial Design and Response Surface Methodology

This study presents the geometric optimization of a Savonius-type VAWT with multi-element blade profiles using a full factorial design integrated with RSM. Two crucial geometric parameters, the blade twist angle (γ) and the aspect ratio (AR), were systematically varied to assess their influence on the power coefficient (Cp). Experimental measurements were performed in a controlled wind tunnel environment, and a second-order regression equation was used to model the resulting data. The optimization approach identified the combination of γ and AR that maximized Cp. The optimal configuration was achieved with a γ of 30° and an AR of 2.0, for which the experimentally measured power coefficient (Cp) reached a value of 0.2326. The results confirm that lower twist angles and higher aspect ratios enhance aerodynamic efficiency, reduce manufacturing complexity, and improve structural reliability. These findings highlight the potential of Savonius turbines as competitive solutions for small-scale energy harvesting in low-wind-speed environments. Moreover, the identified optimal configuration provides a basis for future work that focuses on scaling the design, integrating power transmission and electrical generation components, and validating performance under real operating conditions.