Modelling the eco-hydraulic impacts of tidal energy projects

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The UK, is legally committed to reduce greenhouse gas emissions by 80% by 2050 and to meeting 15% of its energy from renewable sources by 2020. Research suggests that the combined operation of tidal stream and range power schemes can exceed 12% of the UK's energy demand from a sustainable, green energy source. In comparison with other renewable resources this comes with complete predictability which means that tidal can play a vital role in meeting the nation's energy needs. At the time of writing this proposal, pilot projects for tidal stream and range based energy generation are in the advanced stages of planning and development within the UK. The first tidal stream turbines installed within a pilot array in the Pentland Firth off of Scotland have just started to generate power (7 Dec 2016), with the next phase (project Stroma) confirmed on 15 Dec 2016. For tidal range, the UK Government's "Hendry review", released on the 10th of Feb 2017, recommended that tidal lagoons (tidal range structures) can play an important role in the UK's energy mix. This provides a roadmap towards the development of the Swansea Bay lagoon, the first tidal range energy structure of this type worldwide where construction could commence in 2018, with much larger projects to follow.We are thus at a crucial stage in the development of a new tidal-based renewable energy sector where the UK currently leads the world. This project seeks to build on this strong position by providing timely research on the ecological impacts of new, larger tidal developments in a manner that supports decision making by stakeholders, including coastal engineers, financiers, policy-makers and primarily those concerned with environmental impacts. This project builds upon a strong foundation of recent work at Imperial College London that has provided the preliminary demonstration of computational methods for the representation of turbine arrays and tidal range structures within multi-scale models, as well as the optimisation of array designs and tidal plant operations to maximise power or profit, while minimising environmental impacts. Importantly this optimisation is fully coupled to the underlying tidal dynamics, so that changes to the array design and lagoon operation can feed back to the resource and vice-versa.A major hurdle for large tidal energy projects is the uncertainty associated with environmental processes such as sedimentation, water quality and fish migration. In particular, fish mortality caused by encounters with turbines has consistently been a controversial issue that developers and environmental agencies alike have had to consider and mitigate. This project seeks to develop a new methodology that considers fish migration routes in estuarine and coastal areas. It will combine state-of-the-art regional scale ocean models developed at Imperial College with routing and optimisation algorithms developed with the support of experts in fisheries and aquaculture from CEFAS.Ultimately the objective is to apply the developed tools to several real-world sites under consideration: tidal lagoons in the Bristol Channel and tidal stream arrays in the Pentland Firth. These case studies offer the opportunity to provide immediate impact on the design of the first pilot schemes, and a route to support the successful development of larger projects using a more comprehensive ecological impact assessment. This project will therefore provide high impact outcomes to strengthen the UK's leading (academic and commercial) position within the international energy community.The applicant and the wider Imperial group (as well as the academic community in general) will benefit from new ecosystem/fisheries modelling capabilities within the open source Thetis framework. CEFAS will benefit from exposure to, and training on, state-of-the-art numerical modelling tools which have the flexibility to simulate both tidal range and tidal stream coastal infrastructure developments.