Advanced computational modelling of large-scale tidal energy systems: optimising the trade-off between environmental impacts and power generation

Abstract

The future of the UK tidal industry is uncertain. The usefulness of tidal power is not in question, but, as a relatively untested energy source, its practicality and impacts are. In this thesis, the environmental impacts of tidal development are contrasted with the potential to produce power and profit. Initially, the interaction between power generation and alteration of the current is posed as a multi-objective optimisation problem. A methodology is presented to effectively optimise array formation for conflicting societal objectives. In the test cases presented, areas around a tidal array can at times be protected from change at minimal cost to an array’s power generation capacity. Habitat suitability modelling is then incorporated into the array design process and, by selecting two species sensitive to changes in the flow, both positive and negative interactions with tidal development are evaluated. Using the Pentland Firth as a test case, the trade-offs between profit generation and habitat extent of the chosen species are determined, and a Pareto set of optimal array designs is found. A coastal model of the whole UK is then produced, and all prospective areas of tidal development are identified. This ’maximum development’ tidal scenario aligns with the Crown Estate’s estimate of the UK’s theoretical resource. Large changes in the flow regime are seen within 10 km of farms, while small changes are seen up to 120 km away. The impact of these changes on UK marine habitat is assessed for a set of six habitat indicator species. The impact is generally low, but, in the vicinity of the farms themselves, up to 8 % of habitat is affected. Finally, aspects of the Ocean Health Index, a global measure of ocean health, are used to compare the profit- generating potential of the tidal industry with its potential impact on habitat. Under this measure, all impacts on ocean health are small, and, importantly, the overall impact is positive.