**Kyoungboo Yang**

Faculty of Wind Energy Engineering, Jeju National University, 102 Jejudaehakno, Jeju 63243, Korea; kbyang@jejunu.ac.kr; Tel.: +82-64-754-4405

Received: 3 April 2020; Accepted: 4 May 2020; Published: 7 May 2020

**Abstract:** For a wind turbine to extract as much energy as possible from the wind, blade geometry optimization to maximize the aerodynamic performance is important. Blade design optimization includes linearizing the blade chord and twist distribution for practical manufacturing. As blade linearization changes the blade geometry, it also affects the aerodynamic performance and load characteristics of the wind turbine rotor. Therefore, it is necessary to understand the effects of the design parameters used in linearization. In this study, the effects of these parameters on the aerodynamic performance of a wind turbine blade were examined. In addition, an optimization algorithm for linearization and an objective function that applies multiple tip speed ratios to optimize the aerodynamic efficiency were developed. The analysis revealed that increasing the chord length and chord profile slope improves the aerodynamic efficiency at low wind speeds but lowers it at high wind speeds, and that the twist profile mainly affects the behaviour at low wind speeds, while its effect on the aerodynamic performance at high wind speeds is not significant. When the blade geometry was optimized by applying the linearization parameter ranges obtained from the analysis, blade geometry with improved aerodynamic efficiency at all wind speeds below the rated wind speed was derived.

**Keywords:** design optimization; wind turbine blade; blade geometry linearization; tip speed ratio; simulated annealing algorithm
