Floating offshore wind turbine (FOWT) deployments are predicted to increase in the future and the outlook is that globally, 6.2 GW of FOWTs will be built in the next 10 years (https://tinyurl.com/camyybxk). Highly dynamic, free hanging power cables transport power generated by these FOWTs to substations and the onshore grid. Safety critical design of such power cables in order for them to operate in the ocean without failure is of utmost importance, given that these cables are highly expensive to install and replace and any down-time of turbine electrical output results in huge revenue loss. In FOWTs, a large length of the power cable, from the base of the floating foundation to the seabed, is directly exposed to dynamic loading caused by ocean waves, currents, and turbulence. Waves move the floating foundation, and currents produce cable oscillations generated by vortex shedding. In the water column a cable experiences enhanced dynamic loads and undergoes complicated motions. When a dynamic cable is installed in deep water, the upper portion of the cable is exposed to high mechanical load and fatigue, and the lower part to substantial hydrostatic pressure. Motion of the floating foundation in surge, sway, and heave causes the power cable to undergo oscillatory motions that in turn promote vortex-induced vibration (VIV) - which is analogous to the vibration experienced by long marine risers used in offshore oil and gas platforms. As a result, large and complex deflections of the cable occur at various locations along its length, altering its mechanical properties and strength, and eventually leading to fatigue-induced failure. The dynamic forces produce cyclical motions of the cable, and a sharp transition in cable stiffness is expected in cases where these motions and loads concentrate toward a rigid connection point. Repetition of the foregoing process and over-bending can also lead to fatigue damage to the cable. To date, hardly any research has been undertaken to investigate the 3-dimensional nature of VIV, dynamic loads, and motion of power cables subject to combined waves, currents, and turbulence. Moreover, no detailed guidance is given in design standards for the offshore wind industry on how to predict, assess, and suppress fatigue failure of dynamic cables under wave-current-turbulence conditions. Power cable failure is much more likely to occur if the design of such cables is based on poor understanding of the hydrodynamic interactions between cables and the ocean environment. This fundamental scientific research aims to investigate the dynamic loading, motion response, impact of vortex induced vibration and its suppression mechanism, and fatigue failure of subsea power cables subjected to combined 3-dimensional waves, currents, and turbulence. This research will be approached by both numerical and physical modelling of power cable's response. Controlled experimental tests on scale models of power cables will be undertaken in Edinburgh University's FloWave wave-current facility where multi-directional waves and currents of various combinations of amplitudes, frequencies, and directions can be generated. Advanced novel phenomenological wake oscillator models, calibrated and validated with FloWave experimental results, will be used to simulate the hydrodynamic behaviour of power cables. The resulting software tools, experimental data, analysis techniques for characterising cable dynamics and VIV, methodologies established for fatigue analysis, and other outcomes of this research will enhance the design of cost-effective power cables. By reducing uncertainty, our research will lead to increased reliability of offshore power cables, of benefit to the power cable manufacturing industry.

The NHP-WEC project aims to advance data-driven monitoring and control in connection to both device technology and sea state predictions for WEC arrays. The research proposed is simultaneously generic while also significantly contributing to the development of an existing concept device that has shown potential, namely the multi-axis TALOS that has been developed and tank tested at Lancaster University (LU). TALOS is a novel multi-axis point absorber-style built as a 1/100th scale representation, with a solid outer hull containing all the moving parts (like a submarine or a PS Frog style WEC device). The internal PTO system is made up of an inertial mass with hydraulic cylinders that attach it to the hull. The mass makes up a significant proportion of the device, hence it moves around as the hull is pushed by various wave motions. The motion of the ball moves hydraulic cylinders causing them to pump hydraulic fluid through a circuit. The flow of this hydraulic fluid is used to turn a hydraulic motor, which is coupled to an electrical generator, to generate electricity i.e. an inertial mass PTO approach. Key strengths include: The arrangement of the rams allows for the mass ball to move in multiple directions, allowing energy to be captured from multiple degrees of freedom. The flow of hydraulic fluid will change as the ball's motion changes, so an internal hydraulic smoothing circuit is utilised to regulate the output. The latest design has proven to be successful in wave tank testing and the PTO system yields a smooth output in response to time-varying inputs from waves. An analytical model has also been developed to combine data from the hull model and hydraulic rig, yielding a predicted power output of up to 3.2 kW. However, TALOS is at a very early stage of development and requires further research to advance its Technology Readiness Level (TRL). The design, development, deployment and operation of WECs, such as TALOS and their potential commercial use requires a holistic understanding of the marine environment, including on-line monitoring to enhance control combined with prediction. Potential WEC deployment sites and energy resource from single devices and arrays must be determined. Operational conditions, including wave characteristics must be quantified to estimate dynamic loads on WEC, constraining manufacturing and their real-time operation. In this context, SmartWave, developed by the UoH, with the ORE Catapult and Orsted, is a tool capable of deriving high resolution sea state conditions from satellite images using machine learning. Key strengths: SmartWave is based on a novel forecasting methodology, capable of resolving sea state within offshore windfarms for sector O&M logistics. It integrates recent advances in all-weather satellite monitoring to map and study the temporal and spatial distribution of sea surface wave characteristics. However, existing limitations must be addressed to advance the TRL of WEC capabilities and hence fully exploit this new technology. For example, it has been developed to characterize significant wave height, whilst further research is essential in order to extract other sea state parameters, including wave height, direction and frequency. Nonetheless, since it is capable of global reach remotely, without the use of in situ sensors, SmartWave is uniquely placed to identify the selection of appropriate deployment sites depending on the device size and specification, for optimal production of electricity. The NHP-WEC project brings together key aspects of WEC technology and the global deployment potential of SmartWave, allowing integration of novel methodologies across optimisation, control, condition monitoring and resource forecasting. These advances will together drive evidenced reductions in costs and hence provide confidence on the benefits of wave energy technology to developers and investors.

The Ocean-REFuel project brings together a multidisciplinary, world-leading team of researchers to consider at a fundamental level a whole-energy system to maximise ocean renewable energy (Offshore wind and Marine Renewable Energy) potential for conversion to zero carbon fuels. The project has transformative ambition addressing a number of big questions concerning our Energy future: How to maximise ocean energy potential in a safe, affordable, sustainable and environmentally sensitive manner? How to alleviate the intermittency of the ocean renewable energy resource? How ocean renewable energy can support renewable heat, industrial and transport demands through vectors other than electricity? How ocean renewable energy can support local, national and international whole energy systems? Ocean-REFuel is a large project integrating upstream, transportation and storage to end use cases which will over an extended period of time address these questions in an innovative manner developing an understanding of the multiple criteria involved and their interactions.