Extension of UKCMER Core Research, Industry and International Engagement

Wave and tidal energy devices are subjected to normal everyday loadings and abnormal extreme loadings. Extreme loadings are severe and less frequent. The repetitive loadings arising from wave-device interaction or current-blade-structure interaction are lower and occur very frequently in normal operation. Economic designs that will survive have to withstand, without structural failure, a combination of these types of loading over the design life of the device and its subsystems. Cumulative fatigue damage in the wave or turbulent-current environment could occur earlier than anticipated in the life of wave or tidal current technologies and needs to be better understood to predict wear-out or failure and ensure designs are robust without entailing excessive cost. This work will explore numerically through computer modelling, and physically through preliminary model- and sea-testing, the interaction of tidal and wave devices with their sea that surrounds them, one another, their moorings and the electricity network to understand the cyclic and irregular forces acting and the structural loadings arising, ultimately aiming to reduce fatigue effects and increase reliability.

Tidal and wave energy converters are being demonstrated at full-scale in UK waters, supplying the electricity network. Meeting the 2020 and later targets for installed marine energy capacity mandates that single-device installations are up-scaled into arrays, farms and parks. Concurrently fledgling and new technologies must be systematically de-risked. With increased operational service and experience, it is now timely and necessary to explore cyclic loadings and consequent fatigue effects and their consequences for reliability to avoid early component or device failure.

The work proposed will model, predict and measure the repetitive cyclic and irregular forces on devices as the interact with the sea, one another, their moorings and the electricity network. The forecast loading regimes will be used to explore the cumulative fatigue damage and how this could affect wear out and failure of devices, structures, subsystems or components.

Device developers, manufacturers, installers, operating and maintenance companies, and marine energy farm owners will benefit by the findings of this research. Structures, subsystems or component parts, subject to repetitive loadings and stresses could be better designed, manufactured, installed, operated and maintained to avoid premature failure and costly downtime, or more expensive repair or replacement.

Standards and certification authorities will be advised by the findings for future evolution of design codes for the marine energy environment.

The wider sector will benefit by the prior avoidance of failure and associated reputational risk.