Lifetime Extension of Offshore Wind Turbines using a Local-Global Digital Twin Paradigm

• Applicants: Professor Dr. Elyas Ghafoori; Professor Dr.-Ing. Clemens Hübler
• Subject Area: Applied Mechanics, Statics and Dynamics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 574458861

The design and verification of steel structures, as per Eurocode 3, are based on comparing loads/effects and resistances, with resistances exceeding loads/effects by appropriate safety margins. For offshore wind turbines, lifetime extensions require precise structural reassessments that utilize accurate load models reflecting environmental and operational conditions (EOCs) and local approaches to determine resistances. This project proposes a paradigm shift toward local-global digital twins to more efficiently assess loads, based on continuously measured EOCs, and resistances, using real surface geometries of existing steel support structures. By transitioning from conservative design loads and nominal geometries to actual load histories and real scanned geometrical parameters of critical structural details, this approach enables accurate estimation of remaining lifetimes and unlocks the potential for extending service life. However, current limitations hinder this shift. On the global level, computing full load histories from measured EOCs using aero-elastic simulation models is infeasible due to high computational demands. As an alternative to aero-elastic simulations, meta-models providing damage-equivalent loads (DELs) can be used. However, state-of-the-art DEL-based meta-models but are inadequate for local-global digital twins, which require detailed load time-series or load cycle counts. This project addresses this gap by developing efficient meta-models tailored for digital twin applications. On the local level, accurate fatigue life estimation of structural details requires computationally efficient approaches to process real 3D scans of critical regions, such as weld seams. Existing methods struggle with the computational bottleneck of local fatigue analysis. To overcome this, the project proposes a novel meta-model framework for local fatigue assessment. This framework uses 3D-scanned geometries to realistically evaluate fatigue resistance and remaining life by incorporating local geometrical and material properties. Together, these innovations in global and local modelling aim to enable the reliable and efficient reassessment of offshore wind turbine structures, supporting sustainable lifetime extension efforts as well as return of investments.

• DFG Programme: Research Grants