Resource characterization of a commercial tidal stream energy site: Morlais, Irish Sea

Tidal stream energy conversion is an attractive renewable energy option due to the predictability of tides and high energy density. Yet, before sites can be exploited to their full potential, detailed resource characterization is required to optimize device selection and array configuration, and to minimize environmental impacts. This study focuses on the Morlais tidal energy site in North Wales, where developers have been awarded 38 MW of tidal stream generation capacity by the UK Government. The study analyses sea bed and water column data collected across the site over the past decade, including multibeam echosounder data, multiple acoustic Doppler current profiler (ADCP) time series, meteorological and wave data. Additionally, high-resolution tidal and wave models are applied to further characterize the spatio-temporal variability. The undisturbed power density exceeds 10 kW/m 2 at Morlais, with the most energetic locations closest to the shore — facilitating power export to the grid. There is significant interaction of waves and currents across the site. However, this mainly influences wave properties, which could affect maintenance of moorings or devices (due to increased wave steepness), rather than directly influencing the tidal energy resource. There are variations in flood/ebb asymmetry between ADCP moorings, and this is relatively strong at some locations. • Morlais is a 35 km 2 grid-connected tidal energy site in N Wales, UK • Data has been collected including multibeam and 4 ADCP time series • The data analysis is supplemented by wave and tidal models • The site is highly asymmetric with power densities up to 10 kW/m 2 • Tidal currents modulate waves, but waves minimally affect tidal power.