Analytical estimates of the energy yield potential from the Alderney Race (Channel Islands), using marine current energy converters

Energy from marine currents offers the promise of regular and predictable electrical generation at higher power densities than other renewables. The marine current resource is potentially large but mainly concentrated in a number of sites around the world. The power density for a horizontal axis turbine operating in such currents has a similar form to that of a wind turbine and is dependent on the cube of the velocity and the fluid density which for water is about 1000 times that of air. These two factors imply that the power density for marine current energy converters will be appreciably higher than that of wind generators resulting in smaller and hence more manageable size turbines.In the UK, for example, tidal races which exist in the waters around the Channel Islands and the ‘Sounds’ off the Scottish west coast are well known. The energy density at such sites is high due land mass constrictions which result in large current velocities at depths which are suitable for the installation of multiple arrays of turbines. This study was undertaken for the purpose of quantifying the potential of generating electricity from the Alderney Race in the Channel Islands. The work quantifies the resource, identifies fluid currents that could be used for the establishment of various size arrays in the race and constructs some logical course of action and direction for the installation of marine current turbines in arrays in the Race. The analytically predicted results for the selected site of the Alderney race showed that such installations can realise energy yields in excess of 7.4 TWh which is equivalent to 2% of the UK requirements for the year 2000. However, despite the totally predictable resource the energy yield of the site followed an uneven power production which could be used in a planned mixed power production structure. The analysis, although based on data from Admiralty Charts, has shown that there is a large potential for energy generation from such sites. Furthermore, and by virtue of the topography of the site, it is feasible to envisage a modular approach to the installation of size-dependent marine energy conversion devices or turbines to be deployed in phases taking into account technology progression and developments.