Impact of climate-change scenarios on offshore wind turbine structural performance

Offshore wind turbines (OWTs) must be sufficiently safe and resilient to withstand windstorms over an operational life of 20–25 years in an aggressive marine environment. Current performance-based assessment methods for OWTs often neglect structural failure and focus on equipment failure only, which can be assessed using existing empirical databases. This study uses a simulation-based approach to assess various performance metrics associated with offshore wind infrastructure exposed to operational wind and wave conditions. Surrogate modelling is used to predict structural failure due to fatigue in a computationally efficient manner. The proposed surrogate model is based on Gaussian process regression and allows one to run structural simulations at a small training sample of wind and wave conditions and emulates the response at combinations where the OWT was not explicitly assessed. This results in an integrated probabilistic performance-based assessment framework for OWTs that considers both structural and non-structural (equipment) components. In particular, the proposed framework is used to evaluate the potential impact of climate-change scenarios on various OWT performance metrics, namely, fatigue damage, fatigue reliability and, ultimately, financial losses (cost of direct damage) for a case study OWT. This is compared to the change in revenue resulting from power production to understand which is more sensitive to climate change. Both fatigue damage and structural safety are found to be sensitive to changes in the site environmental conditions. However, as financial losses additionally depend on non-structural components - which are typically characterised by much higher failure rates - they are found to be less sensitive to the considered climate-change scenarios.