Abstract
Maintenance and repair of wind turbines contribute to the higher costs of wind energy. In this paper, various technologies of structural repair of damaged and broken wind turbine blades are compared. The composite plates, mimicking damaged blade parts, were damaged and repaired, using various available curing and bonding technologies. Technologies of repair with hand layup lamination, vacuum repair with hand layup and infusion, ultraviolet repair and high temperature thermal curing were compared. The repaired samples were tested under tensile static and fatigue tests, and subject to microscopic X-ray investigations. It was observed that both the strength of the repaired structures and the porosity depend on the repair technology used. Vacuum-based technologies lead to relatively stiff and lower-strength repaired plates, while ultraviolet-curing technologies lead to average stiffness and high strength. High-temperature vacuum curing leads to the highest maximum stress. Hand layup (both vacuum and without vacuum) leads to high post-repair porosity in the adhesive and scarf, while vacuum infusion leads to low porosity. Fatigue lifetime generally follows the trend of porosity. There exist risks of micro-damaging the parent laminate and the formation of residual stresses in the repaired structure.
Highlights
Introduction and Andrzej BieleckiExpansion of renewable energy is one of the key elements of the global strategy to mitigate global warming
The quality of blade repair is very important for the post-repair time of wind turbine blades [9,11]
While the sample bending is a result of large strains applied during the destructive testing, and such high strains cannot be observed in real life, this illustrates the potential for undesirable internal stresses, when repairs are applied to a potentially unknown substrate
Summary
Expansion of renewable energy is one of the key elements of the global strategy to mitigate global warming. For the years and decades, a large expansion of wind energy is planned. The USA plans a massive expansion of wind farms off the coasts. The operation and maintenance (O&M) of wind turbines remain important factors, influencing the wind energy price. Onshore wind farm operators spent around USD 15 billion on O&M services in 2019, of them, 57% on unplanned repairs [3,4]. Wind turbine service companies and wind-park owners face a large choice of technologies for the blade repair. The authors sought to provide the service companies and end users with necessary information for the comparing and selecting of the repair technologies, and, on the other hand, to give the adhesive and equipment developers feedback on the performance of their products in quasi-real conditions
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