Electricity can be generated through the conversion of the kinetic energy that resides in tidal currents in a similar way to a wind turbine. The ubiquitous nature of tidal energy, and the predictability and reliability of tidal currents, gives tidal-stream energy distinct advantages compared to other renewable energy technologies. Individual tidal energy devices have been installed and proven, with commercial arrays planned throughout the world. Yet, the true global resource and ocean conditions are broadly unknown, affecting optimal global device design. Present methods are unsuitable as the industry matures beyond the fast, shallow, well-mixed, and wave sheltered "demonstration" sites - influencing investor confidence. Transformative understanding of this sustainable natural resource for the coming century is therefore needed to bring a step change towards a sustainable, high-tech and globally exportable, UK renewable energy industry.

CHALLENGE 1: How much tidal energy is there in the world and how is it distributed?
OBJECTIVE 1: Resolve the true tidal-stream energy resource using unique datasets, consistent modelling framework, and state-of-the-art modelling techniques.
Global tidal resource assessments are based on coarse, data constrained, models that are not validated for the few tidal energy sites resolved, as developed for other applications (e.g. global energy budgets); therefore, the global tidal energy resource is only broadly known. Fine-scale bathymetric constrictions (e.g. coral reef passes), biological communities (e.g. flow diverted around kelp beds) and ocean currents, can all accelerate currents between constrictions; meaning many sites initially dismissed as commercially unviable may actually be suitable. A consistent modelling framework (e.g. resolution and physics), and comparison of modelling techniques, will be developed to reduce bias and determine the potential global resource.

CHALLENGE 2: How do conditions vary globally and will this change in the coming century?
OBJECTIVE 2: Realistic oceanographic conditions at potential tidal-stream energy sites for the coming century will be determined
For sustainable device design, realistic oceanographic conditions must be characterised for the lifetime of deployments, and cascaded through high-fidelity device-scale models (e.g. CFD); yet oceanographic conditions, and the impact of climate change, at tidal energy sites is largely unknown. Previously unviable tidal energy regions may become economically viable in the future (as near-resonant tidal systems and their associated currents are sensitive to sea-level rise), and, due to wave-tide interaction processes, oceanographic conditions at tidal energy sites may change. Dynamically coupled wave-tide ocean-scale models will be developed to inform the developing industry (e.g. optimal and resilient design), with new techniques that can simulate the interaction between the resource and devices.

CHALLENGE 3: Are current methods of suitable as the industry develops?
OBJECTIVE 3: Improved methods of device behaviour in resource and environmental assessment models
The industry is evolving beyond fast, shallow, well-mixed and wave sheltered sites, to areas of the world with complex oceanographic conditions (e.g. ocean currents and swell wave dominated climates). New approaches are needed to understand the interactions between devices, resource and environment. Device-scale interaction studies assume well-mixed (i.e. homogenous) channelized flows, with tidal turbine loading from waves assessed assuming waves travel in-line with tidal currents (waves following or opposing current), which is not the case beyond an extremely limited number of tidal straits (e.g. Pentland Firth). Furthermore, device interaction with the flow must also be resolved within resource assessment, beyond simplified momentum sink terms. Device behaviour and interactions will improved at both ocean and device scales.

Potential Impact:
A globally exportable and high-tech industry that can meet renewable energy targets is of international importance. Global resource distribution (thus market potential) and likely conditions during the lifetime of deployments is essential for optimal, resilient device design and improved investor confidence. Ensuring feedbacks between renewable energy extraction and the environment are minimised is also crucial for a sustainable industry. The predictability and ubiquitous nature of tidal energy makes this research essential for the future of UK innovation and world leading research. This research will directly benefit the Offshore Renewable Energy (ORE) sector, bringing a step change in the development of a sustainable, globally exportable, renewable energy industry - reducing our dependence carbon based electricity sources, and providing long-term socio-economical gains for remote or fuel poverty communities.

METRIC has three core challenges, each with direct impact:
C1. How much tidal energy is there in the world and how is it distributed?
This will inform policy as to the potential size of the marine renewable industry

C2. How do conditions vary globally and will this change in the coming century?
This will inform global optimal and resilient design

C3. Are current methods of suitable as the industry develops?
Informing industry standards and ensuring sustainability and investor confidence

By developing methods to understand ocean conditions at high tidal dissipation sites, this research will also lead to improved understanding of environmental change in the most productive coastal zones of the world; applications include coastal flood risk and coastal engineering, including all offshore renewable energy industries. Improved modelling methods during this will project will directly translated to academic and industry through direct placements at some of the world's leading hydrodynamic modelling teams: Netherlands (Deltares), USA (USGS), Australia (CSIRO), UK universities and UK Met Office.

The development of coupled wave-tide modelling method, downscaled with climate model data, will allow assessments of the changing nature of the resource and conditions at high tidal energy dissipation regions in a global context. Furthermore, as sea-state is influenced by wave-tide interaction (e.g. wave growth, breaking and steepness), improved understanding of wave-tide interaction for cabling resilience (of ORE installations) as well as resilience in all offshore engineering (e.g. floating platforms).

This fellowship will directly be working with the new Offshore Renewable Energy Supergen Consortium (Deborah Greaves as Project Partner and steering committee), and therefore has excellent pathways for impact within the entire industry and research field. iMARDIS data portal (www.imardis.org) will host the outputs of this project, and this data portal will enable interested parties to read about the project and download model data as soon as it comes available. Open access, peer-reviews, journal articles will form important outreach - and 6 articles are planned in leading high impact journals. Dissemination through international and national conferences will also form an important part of outreach - with ORE conferences (AWTEC, EWTEC, PRIMARE, ICOE) as well as main-stream earth science and oceanography conferences (ALSO/AGU, EGU, Int. Waves workshop) planned. A recently established Marine Renewable Energy MSc at Bangor University will be used to communicated relevant project outcomes to student and establish links for the future of science and innovation.

Atlantis are an agreed project partner to this fellowship, allowing direct dissemination to industry, which will be broadened to nine other tidal energy developers through the European-funded Bangor-led SEACAMS projects (www.seacams.ac.uk), who are also the data managers of the Crown Estate's West Anglesey tidal-stream energy demonstration zone.