Condition-based maintenance of wind turbine structures: A state-of-the-art review

Wind turbine structures have become increasingly popular due to global trends in renewable energy policies. However, more than 3800 failures are reported annually, and resultant maintenance and repair costs are significant. Previous studies have mainly focused on structural failures from the historical perspective, but there is a lack of discussion on condition-based maintenance to reduce life-cycle costs. Furthermore, the studies on disposal after end-of-life are limited. To face these challenges, this study aims to optimize wind turbine structures throughout their life cycle, from design to disposal with four key approaches. From parts to system level, wind turbines are investigated (i) theoretically and (ii) experimentally under dynamic stress and various environmental conditions for optimized and safe operation. Health monitoring, damage diagnosis, and prognosis approaches are highlighted to ensure their reliable and secure operations. Maintenance strategies are reviewed from repair to maintenance perspective (iii). Finally, recycling and life cycle assessment studies are discussed, along with current challenges in condition-based maintenance (iv). Advanced condition-maintenance with four approaches will lead to enhanced sustainability and efficiency of wind turbine systems to achieve the goal of carbon neutrality. Lastly, scientific recommendations and guidelines for future research towards sustainable net-zero life cycle of wind turbine structures are proposed.