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Background

Proposals for damming or barraging the Severn Estuary (and Bristol Channel) have existed since the 19th century for reasons such as transport links and flood protection.

In more recent decades the focus has moved to considering the possibility of harnessing the huge 14 metre tides of the Estuary to generate electricity. Studies in the 1970s and 80s investigated six possible barrage locations and concluded that an ebb generation scheme (one that generates electricity as the tide goes out) between Lavernock Point and Brean Down (the ‘Cardiff-Weston’ barrage) was the preferred barrage option. In 1989 a detailed study focussing on the Cardiff-Weston barrage (Energy Paper 57) concluded that the scheme was technically feasible and would have an annual output of approximately 17 terrawatt hours. (Or nearly 5% of UK electricity today). However, Government decided that a Severn Barrage was not a cost-effective option for generating electricity at that time.

Energy Review 2006

In May 2006, with the growing evidence of climate change and rising fossil fuel prices, Government asked the Sustainable Development Commission (SDC) (Government’s independent advisory body on sustainable development) to look again at tidal power options in the Severn Estuary.

Their report (which looked at tidal stream and tidal range technologies) concluded in October 2007 that:

• The Severn Estuary tidal range can generate some 5% of UK electricity
• The Severn Estuary (and Bristol Channel) tidal stream resource is not one of UK top ten sites
• It is possible to build a barrage that meets the principles of sustainable development but it must comply with the Habitats Directive and other environmental legislation in force – no derogations
• Government needs to carry out an ‘appropriate assessment’ using up-to-date modelling techniques to really understand the impact
• Compensatory habitat can be viewed as ‘environmental opportunity’ - combine climate change mitigation (the barrage) with adaptation (the compensatory habitat)
• HMG should own and lead the project

The SDC study (and six supporting reports) can be found on the Sustainable Development Commission (SDC): Tidal Power webpage.

Current Feasibility Study

Following the SDC report, the Government published terms of reference for the current feasibility study on 22 January 2008. The focus of the terms of reference is on tidal range (rather than tidal stream) technologies as this is where the energy potential in the Severn Estuary is greatest. As the SDC report did not (and did not aim to) provide a detailed analysis of all tidal range technologies, the feasibility study will consider all tidal range technologies (including barrages, lagoons and others) at this stage.

• Severn tidal power feasibility study: terms of reference (29KB)
  URN 08/585