Design tools for the optimal exploitation of tidal-stream renewable energy

Abstract

Tidal stream power generation is attractive for a number of reasons. However, this will only be deployed on a commercial scale, in arrays of tens to hundreds of turbines, if these arrays can be shown to be viable from economic, engineering and environmental perspectives. With limited experience from real arrays and constraints on the size of lab-based experiments, advanced numerical tools are needed to both predict and maximise power yield. These tools can be used to prove viability of new sites and aid array design in this fledgling industry. Holistic economic models are needed to aid the industry's move from demonstrator arrays to commercially sized arrays that can compete at a lower subsidy level.

This thesis investigates economic models for evaluating the performance of arrays and different cost reduction methods, which may help to bring the cost of tidal energy in line with other sustainable energy sources. A methodology to optimise array design with respect to complex economic models is presented. This method builds an emulator of the trade-off curve between total yield and number of turbines, generated from a computationally expensive set of optimisation loops. It enables far more robust analysis of the implications of changes to the economic models than is possible through direct optimisation alone.

A tool is created to investigate further cost reductions that could be obtained through the assessment of a range of different turbine rotor sizes and rated capacities, as well as other array design specifications. The tool is used to make preliminary assessments of array design choices, while adhering to practical constraints such as sea bed depth and steepness, along with legal constraints such as consents on the number of turbines and spacing between them. The tool developed can be applied to early-stage assessments and narrowing down the scope of array design specifications.