Optimization of twin vertical axis wind turbines through large eddy simulations and Taguchi method

The aerodynamic performance of twin configurations of vertical axis wind turbines (VAWTs) was systematically analyzed through large eddy simulations (LESs). The reliability of the computational results was validated through comparisons with experimental data reported in the literature. The Taguchi method was used in the optimization analysis, and an L₁₆ (4⁵) orthogonal table of five critical operation parameters—pitch angle (β), turbine spacing (S/D), aspect ratio (η), solidity ratio (σ), and rotational direction (γ)—with four levels was designed. Range analysis was applied to the results of the orthogonal test. Pitch angle was found to have the greatest extent of impact on power performance, whereas rotational direction exerted the least impact. Additionally, turbine spacing exercised the second greatest impact, followed by aspect ratio and thence solidity ratio. Accordingly, the parameter settings for the optimal and the worst twin array units were determined. The power performance of the optimal and worst twin array units increased by 13.72% and 7.39%, respectively, relative to their standalone counterparts. Moreover, analyses of the flow mechanisms indicated that to reduce power loss, tip winglets or tapered blade ends should be used in twin array units, especially those with small aspect ratios.