E. M. Evans


An investigation into the feasibility of tidal stream energy extraction is presented. The first part of the work is concerned with the economics, technology and costing of free stream tide mills for the deployment off the Channel Islands of Jersey, Guernsey and Alderney. Future fossil fuel prices are represented by three uniform rates of increase corresponding to overall increases of 200%, 100% and 50% in a 25 year period. Fuel replacement arguments indicate potential levels of investment in tide mills, pe r rate d kW, of £2040, £1574 and £1340 for Jersey and Guernsey and £3269, £2521 and £2148 for Alderney, for each of the above rates of fuel price rise respectively. An outline specification of a device rated at 500kW is costed at 2187£/kW(rated) using a top-down approach combined with costs from analogous applications. Preliminary consideration of resource characteristics indicates the potential for improved economics via a contribution to firm power with the exploitation of pairs of tide mills situated in out-of-phase streams. In the second part of the work the general problems of tidal stream prediction and description are discussed and a new approach suggested. Tidal streams are modelled using a high resolution numerical scheme. The model developed involves the solution of the full y non-linear, depth averaged hydrodynamic equations with a grid spacing of 740m. The scheme includes a simplified technique to model coastal drying regions. Results of modelling indicate the locations of a number of sites off each island where the potential power output per device exceeds 300kW(rated). Levels of deployment are discussed for each of the islands and in the cases of Jersey and Guernsey levels of 2MW are suggested and a contribution to firm power demonstrated.

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