Assessing hydrodynamic impacts of tidal range energy impoundments in UK coastal waters

Tidal range energy comprises a vast theoretical resource of 9,220 TWh per year, globally, with advantageous characteristics of predictability, generation flexibility and reliability. Approximately 13% of this resource lies within the United Kingdom’s (UK) coastal waters, where it could supply up to 12% of annual electricity demand. Tidal range energy conversion traditionally involves constructing and operating large-scale coastal or offshore impoundments ( O 10-100 km 2 ), which will redefine near and far-field water levels and flow patterns. The relationship between the scale of the impoundment area and hydrodynamic impact has not been investigated for UK sites. To address this, we develop a two-dimensional (depth-averaged) TELEMAC model of the Irish Sea, and simulate six scenarios involving tidal range schemes of increasing basin area, from 25 to 150 km 2 , located on the North Wales coast in an open coastal basin setting. Results indicate that far-field ( 30 − 150 km) changes to the amplitude of the semi-diurnal ( M 2 ) tidal constituent exhibit a linear relationship with impoundment area and volume (correlation coefficient R = 0 . 95 and R = 0 . 96 , respectively). The largest impoundment (150 km 2 ) caused far-field changes in maximum surface elevation ( 2 < η m a x < 3 cm); near-field surface elevation was reduced ( η m a x > 3 cm). • The UK has a vast and untapped tidal range energy resource. • Uncertainty regarding hydrodynamic impacts are a key barrier to tidal range energy conversion. • Tidal range impoundment size is linearly correlated with changes in tidal amplitudes. • Tidal amplitudes are reduced near the impoundment ( < 50 km), and increased in the far-field ( > 50 km).