The challenges of harnessing tidal energy

14 Oct 2013

At the end of 2012, the Select Committee on Energy and Climate Change began an inquiry into a proposal put forward by Hafren Power for a privately-funded, 18km tidal barrage across the Severn estuary.

Last month saw the publication of the Government’s response to the Select Committee’s report, in which it made clear that “more detailed, credible evidence” would be required before the proposal could be considered further.

The need for additional information on the development of the low-head turbines and the impacts of the barrage on ports, navigation and flood risk was highlighted, as was the requirement for more evidence to support claims about job creation and other proposed benefits. Specific reference was also made to the need for an in-depth study of environmental impacts.

The considerable impacts of a barrage on intertidal habitats, fish and bird populations, water quality, and water and sediment dynamics were the subject of much of the evidence provided to the inquiry, including in a submission from NERC, to which both myself and Mel Austen of the Plymouth Marine Laboratory contributed.

The Government’s response went further than simply calling for an Environmental Impact Assessment, in suggesting that a large-scale tidal project in the “sensitive and highly protected Severn” may face “insurmountable obstacles” in complying with requirements under the EU Habitats Directive to mitigate environmental impacts, adding that the high level of public interest provided by renewable energy would not lead to schemes securing automatic approval.

The Government’s position does not inspire confidence that a large-scale barrage will be given the go ahead any time soon, with even supporters of the Hafren Power proposal reportedly stating it was “dead in the water” for the moment.

So far, this latest inquiry suggests that little has changed since the conclusion of the last detailed feasibility study on a Severn Barrage in 2010.  However, there is one key difference, as the Government has given a clear signal that it is willing to consider alternative approaches to harnessing the energy within the Severn estuary, even going as far as to endorse as a “useful framework” the Balanced Technology Approach proposed by RegenSW and its partners.  This approach suggests a combination of tidal range (lagoon and small barrage), tidal stream, wave and offshore wind, that could possibly supply 10-15GW of energy.

There is already interest from developers in taking forward individual tidal lagoon schemes within the Severn, such as Stepping Stones and also the Swansea Bay tidal lagoon, for which stakeholder consultation has been undertaken and preliminary environmental information produced.

Taking a new approach to energy from the Severn estuary brings with it considerable challenges.  One of the attractions of a ‘traditional’ barrage is that it is a proven technique and the likely environmental impacts are comparatively well understood.  The Government has explicitly stated that it will only consider alternative schemes that can provide strong evidence of value for money, economic benefits, energy saving and environmental impact mitigation.

However, as RegenSW note in the Balanced Technology discussion document, there remain many engineering and environmental unknowns and uncertainties around deploying new marine energy technologies at a significant scale, both within individual projects and also in relation to the interactions between them.

Researchers within UKERC’s Energy and Environment theme are already working to help progress our understanding of some of these issues.  Scientists at the Plymouth Marine Laboratory and the Universities of Aberdeen, Southampton and East Anglia, are studying the colocation of marine energy with other coastal activities and public preferences for the attributes of tidal range and offshore wind schemes as well as modelling the cumulative effects of offshore wind farms and comparing the impacts of different energy technologies in full life cycle analysis on national and global ecosystem services.

The feasibility of a Severn Barrage has been considered since the 1920s. As the need for sustainable energy sources becomes more and more pressing, hopefully we won’t spend another 100 years repeatedly considering the same approach, but will rise to the challenge of developing alternative options for maximising energy from the Bristol Channel while minimising the associated environmental and social impacts.

Tara Hooper is an Environmental Economist at Plymouth Marine Laboratory. Tara’s research is being funded by the UK Energy Research Centre (UKERC).