Multi-objective structural optimization of long flexible wind turbine blades for enhanced lightweight and reliability

Global climate change and the energy crisis have driven the demand for larger wind turbines, posing new challenges to conventional blade design paradigms. A more thorough understanding of lightweight structural design and its associated risks is required due to the increasing blade length and flexibility. To address these issues, this study presents three key developments. First, an innovative layout strategy is proposed to determine the optimal spanwise position of maximum spar cap laminate thickness based on stress analysis. Second, an efficient and tailored fatigue assessment model for blade root is established through load and stress analyses, which is particularly tailored for structural design problems centered on spar cap laminate thickness optimization. Third, a modular multi-objective optimization design platform for long flexible blades is developed. Using the spar cap laminate thickness as the primary design variable, and considering blade mass reduction, tip-tower strike risk mitigation, and fatigue performance improvement as the main objectives, a comprehensive optimization is conducted. The final design achieves a 2.02% reduction in blade mass, a 1.38% decrease in tip-tower strike risk, a 5.77% reduction in root fatigue failure risk, and about 3% cost savings for a 15 MW turbine. These results highlight a structurally optimized blade with enhanced lifecycle performance, effectively balancing lightweight construction, cost efficiency, reliability under extreme conditions, and long-term stability. The study provides practical guidance for long flexible blade design and supports the continued scaling and sustainable development of the wind power industry.