A probabilistic framework for offshore wind turbine loss assessment

Abstract

During their operational life, offshore wind turbines (OWTs) may be exposed to severe storms, resulting in extreme wind and wave loading acting on the OWT structure (and substructure). This paper proposes quantifying financial losses associated with an OWT exposed to extreme wind and waves using a probabilistic risk modelling framework, as a first step towards evaluating offshore wind farm (OWF) resilience. The proposed modelling framework includes a number of novel elements: 1) the development of site-specific fragility relationships (i.e., likelihood of different levels of damage experienced by an OWT over a range of hazard intensities), properly accounting for uncertainties in both structural capacity and demands; 2) the implementation of a closed-form technique, based on a combinatorial system reliability approach, to assess failure consequences (e.g., financial loss) for both structural and nonstructural components; 3) a coherent treatment of epistemic uncertainties across the framework (e.g., sampling variability in fragility estimation), providing loss results accounting for uncertainty of estimation. These aspects can allow for more informative comparisons of various design solutions in terms of structural fragility and risk and/or an improved evaluation of probabilistic losses for decision making. An illustrative application to two case-study sites is presented as a simplified walk-through of the calculation steps in the proposed framework, discussing possible outcomes. For instance, the results from the illustrative application indicate the structural components play an important role in the overall risk profile of an OWT, but this depends on the site-specific wind and wave conditions. The calculation of losses provides a foundation from which a more detailed assessment of OWT and OWF resilience could be developed.

Influence of The Personnel Availability on Offshore Wind Farm Maintenance

“…One of the most important factors that have an influence on the WT and ipso facto on the OWF maintenance is weather. The influence is a subject of discussion in Battisti et al (2006); Carroll et al (2016); and Wilkie and Galasso (2020). In this paper, it is also considered as a major constraint on the performance of maintenance tasks.…”

Site-specific ultimate limit state fragility of offshore wind turbines on monopile substructures

“…In a separate study [55], the full probabilistic risk framework has been implemented utilizing the fragility curves developed here and assessing the number of random seeds required for the fragility curves, explicitly quantifying the error due to limited sampling using resampling.…”

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

“…Recently, a probabilistic risk assessment framework for OWTs exposed to extreme wind and wave conditions (i.e., considering the ultimate limit state, or ULS) has been proposed by the authors, 1) enabling the modelling of these complex loads and their induced structural demands for use in financial loss calculations; and 2) considering an OWT as a system of interrelated structural and non-structural (e.g., equipment) components (4). The study presented here aims to extend this probabilistic risk assessment framework to also include operational wind and wave conditions and consider the fatigue limit state (FLS) which more often drives the design of OWT substructures in European waters (5).…”

“…A simplified loss assessment procedure is proposed to combine failure rates for the OWT structural components with those recorded empirically for the non-structural components (e.g., equipment). The procedure is only sketched in brief as full details are provided in Wilkie and Galasso (4). It consists of generating different failure scenarios from all possible combinations of different states in a system with a given number of components.…”