Global optimization of Savonius-type vertical axis wind turbine with multiple circular-arc blades using validated 3D CFD model

Vertical-axis wind turbines, such as Savonius-type wind turbines (SWT) are an attractive choice for small-scale electricity generation. Recent SWT research is mostly targeted at improving the SWT power coefficient, which is also the topic of this paper. The power coefficient was improved by optimization of a multi-blade SWT (2, 4 and 6), with blades based on circular arc segments. Additional optimization variables were the tip-speed ratio and the aspect ratio. The main novelty of this paper is the global optimization using genetic algorithm, which involved analysis of many different designs (similar to 10(5)) using a validated 3D CFD model with a 4eq SST turbulence model. Since many designs were investigated, the optimization result is considered as the global optimal solution. In the 4 and 6-blade cases, the global optimal solution was similar to the previously proposed Scooplet-based design. The design was improved to achieve power coefficient c(p) = 0.32 with aspect ratio 1.5, and additionally c(p) = 0.34 with an increased aspect ratio of 2.5. Optimized designs were compared with a similar multiple quarter-blade design known from previous research (which was outperformed by 60%). For the 2-blade case a novel design was reached, which operates at TSR = 1.2, and achieves a 12% improvement over the classical SWT. (C) 2021 Elsevier Ltd. All rights reserved.