Tidal Modelling - Interactions: Analysis and Conclusions Report

Abstract:

Launched in October 2011 this project involved Black & Veatch, in collaboration with HR Wallingford and the University of Edinburgh to develop a model of the UK Continental Shelf and North European Waters, 100 times more accurate than existing marine data. This has been used to assess the tidal energy potential around the UK (tidal range and tidal streams), to inform the design of energy harnessing schemes, to assess their interactions, and to evaluate their impact on European coasts. It can also be used to renew and inform flood defences, coastal erosion and aggregate extraction. Now completed, the project has been launched to market under the brand of SMARTtide. This is available to the marine industry under licence from HR Wallingford.

The Project develops and verifies a set of modelling tools, and performs an initial analysis of the impact of energy extraction at various potential tidal range and tidal stream energy extraction sites. This document describes the results of TRM modelling runs to determine if there are interactions between potential future Tidal Stream and Tidal Range schemes.

In this analysis, a series of tidal current and tidal range energy schemes have been defined and implemented in the DCSM that generally reflect realistic developments for different time horizons (2020, 2030, 2040 and 2050), dependent upon the available technology and political will (optimistic, medium or pessimistic). Extreme and special cases have also been included.

Clear conclusions were:

• That any credible tidal current development does not impact on the tidal range sites.
• That there is only a minimal impact of tidal range sites on tidal current sites, in the most extreme cases. In less extreme cases, there is essentiallyno impact.
• Extreme scenarios suggest that the Severn Outer barrage has a significantly more severe far-field impact (on tidal current sites) in comparison with the combination of the Cardiff-Weston barrage and Bridgewater Bay lagoon.
• ‘Mega’ schemes with dual generation (Severn Outer, Solway Firth) do not work as intended, and effectively cannot move the water away fast enough, impeding generation. Noticeable benefits in using Rolls-Royce turbines in dual-mode schemes were observed for the Solway Firth, Mersey, and the Wash as there are reduced impacts on downstream tidal range than equivalent dual schemes.
• Large reduction in downstream tidal range for major barrages/lagoons in estuaries (Bridgwater Bay, Cardiff-Weston, Mersey, Thames, Wash, Humber) reduces their energy output compared to 0D modelling, as expected.
• Much less effect on downstream tidal range for lagoons on open coastlines (Rye, Dymchurch, Cumbria, Wigtown) or smaller lagoons, suggesting these may be worth further investigation.
• The increased tidal range which is visible, in particular in the Irish Sea and surroundings, when there is large scale deployment of tidal range schemes in that area, is unlikely to be acceptable in terms of environmental (and safety) impacts.
• Significant interactions (i.e. a negative effect on tidal range and potential energy) within the Severn – e.g. the Cardiff-Weston barrage reduces energy output for lagoons downstream.
• Almost no interaction between tidal range schemes in Irish Sea, despite the impacts on increased tidal range discussed earlier.
• In UK waters, large scale utilisation of the tidal resource requires significant optimisation to avoid potentially unacceptable cumulative impacts and to ensure the most energy can be extracted from the resource (potentially at least cost, with least impact on the grid etc.).

Publication Year:

2014

Publisher:

ETI

DOI:

https://doi.org/10.5286/UKERC.EDC.000833

Author(s):

Black & Veatch and HR Wallingford