Navigating the Valley of Death: Reducing Reliability Uncertainties for Marine Renewable Energy

Technology Readiness Levels (TRLs) are a widely used metric of technology maturity and risk for marine renewable energy (MRE) devices. To-date, a large number of device concepts have been proposed which have reached the early validation stages of development (TRLs 1-3). Only a handful of mature designs have attained pre-commercial development status following prototype sea trials (TRLs 7-8). In order to navigate through the aptly named ‘valley of death’ (TRLs 4-6) towards commercial realisation it is necessary for new technologies to be de-risked in terms of component durability and reliability. Due to a lack of deployment experience a conservative design approach is often adopted utilising existing offshore certification guidance. Developers must therefore balance the competing requirements of designing economically viable and yet robust devices. Reliability assessment (including physical component testing and statistical analysis) enables device developers to determine component suitability and reliability in a cost-effective way prior to full-scale prototype deployment. Within the context of the collaborative European project DTOcean (Optimal Design Tools for Ocean Energy Arrays), this paper summarises recent research activities conducted by the University of Exeter at two purpose-built test facilities designed for MRE device concepts that are at TRLs 4-7; post-design validation and pre-full-scale testing. Studies investigating the performance and long-term durability of mooring components for MRE devices are reported which have utilised the Dynamic Marine Component (DMaC) test facility and the South West Mooring Test Facility (SWMTF). In addition progress is reported on the development of numerical methods to predict component reliability. This research provides valuable and previously unreported insight into long-term component use and system design for MRE devices.