Resource assessment for future generations of tidal-stream energy arrays

TLDR

Tidal‑stream energy devices require spring‑tide velocities above 2.5 m s⁻¹ and water depths of 25–50 m, and the Irish Sea—an important development region—was evaluated using a 3‑D hydrodynamic model that incorporates both existing and prospective technologies. The authors employed a 3‑D hydrodynamic model with three grid resolutions and two boundary‑forcing products, all of which were extensively validated. The analysis indicates only 4 TJ of annual mean energy within a 90 km² area using current turbine technology, suggesting limited long‑term sustainability, but shows that lowering the required spring‑tide velocity to >2 m s⁻¹ and permitting deployment in any depth >25 m could increase the resource sevenfold, while also revealing that misaligned flood/ebb currents, a 20° rectilinear flow error (≈3° for lower velocities/deeper sites), and sensitivity to model resolution (<500 m) constrain practical resource estimates.

Abstract

Tidal-stream energy devices currently require spring tide velocities (SV) in excess of 2.5 m/s and water depths in the range 25–50 m. The tidal-stream energy resource of the Irish Sea, a key strategic region for development, was analysed using a 3D hydrodynamic model assuming existing, and potential future technology. Three computational grid resolutions and two boundary forcing products were used within model configuration, each being extensively validated. A limited resource (annual mean of 4 TJ within a 90 km2 extent) was calculated assuming current turbine technology, with limited scope for long-term sustainability of the industry. Analysis revealed that the resource could increase seven fold if technology were developed to efficiently harvest tidal-streams 20% lower than currently required (SV > 2 m/s) and be deployed in any water depths greater than 25 m. Moreover, there is considerable misalignment between the flood and ebb current directions, which may reduce the practical resource. An average error within the assumption of rectilinear flow was calculated to be 20°, but this error reduced to ∼3° if lower velocity or deeper water sites were included. We found resource estimation is sensitive to hydrodynamic model resolution, and finer spatial resolution (<500 m) is required for regional-scale resource assessment when considering future tidal-stream energy strategies.