Specificities of floating offshore wind turbines for risk and safety evaluation of anchoring systems

‍

Abstract  

Floating offshore wind turbines (FOWT) will be necessary to harvest 70% of the EU and EEA technical offshore wind potential present in deep water, where traditional fixed offshore wind architecture is not cost-competitive. FOWT technologies are still in their infancy and represent only 0.2% of currently installed commercial capacity (193 MW). The design of mooring systems and anchors for FOWTs heavily relies on established oil and gas practice, which is sub-optimal as the requirements for design are very different. A reassessment of anchor design methods and practices is necessary, with regards to the lower risk of FOWT failure and the need to commoditise FOWT technology to install tens of thousands of them within the next 25 years. This lecture will summarise how FOWT specificities affect their design and risk analysis, focussing on three key aspects: (i) new configurations, such as shared anchors for arrays of FOWT, introduce new anchor design challenges and a more complex risk evaluation, where a single anchor failure can cascade across the array; (ii) new ground uncertainties are related to the very large areas of wind farms, for which new approaches to ground investigation are needed. Uncertainties on ground conditions increase the risk of anchor failure, or the risk during installation (e.g., refusal due to shallow rocky seabed); (iii) new design philosophies, such as a whole-life approach, allowing for changes in geotechnical resistance due to whole life actions, as well as risk-informed design, in which the different risks and consequences influence the design basis.   

‍

Short Curriculum

Benjamin Cerfontaine is a lecturer at the University of Southampton. He obtained his PhD at the University of Liège in 2014, moving to the University of Dundee with an MSCA individual fellowship in 2017, before joining the University of Southampton in 2020. Benjamin’s work has focused on geotechnical solutions to support renewable energy developments, and particularly on foundations for offshore wind turbines. His rationale has always been to understand the physics and complex mechanisms that underpin the behaviour of geostructures. He has studied hydro-mechanical couplings during suction caisson cyclic loading, the installation of screw piles and the loading of anchors in rocks, all in the offshore environment context. His expertise ranges from constitutive and DEM modelling, to centrifuge modelling.