Additional background information
Proposals for a dam or barrage in the Severn Estuary and Bristol Channel have existed since the 19th century for reasons such as transport links and flood protection.
More recently the focus has moved to considering the possibility of harnessing the huge 14-metre difference in the tides of the estuary to generate electricity. Studies in the 1970s and 1980s 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 focusing on the Cardiff-Weston barrage (Energy Paper 57) concluded that the scheme was technically feasible and would have an annual output of approximately 17 terawatt hours, or nearly 5 percent of the UK's current electricity. However, the government at the time 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, the Sustainable Development Commission (SDC) (an independent advisory body on sustainable development) were asked 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 5 percent of the UK's electricity
- the Severn estuary and Bristol Channel tidal stream resource is not one of the UK's 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
- it is necessary to carry out an appropriate assessment using up-to-date modelling techniques to really understand the impact
- compensatory habitat can be viewed as an environmental opportunity to combine climate change mitigation with adaptation of the compensatory habitat
- the Government should be responsible for the project.
Current feasibility study
Following the SDC report, terms of reference for the current feasibility study were published on 22 January 2008. The focus of the terms of reference is on tidal range (rather than tidal stream) technology 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 considers all tidal range technologies (including barrages, lagoons and others).