The Severn Barrage Review

A talk by Mr David Kerr
May 9th 2007

Mr David Kerr, formerly Chief Design Engineer of Sir Robert McAlpine given to Joint RPEC and SWEHS meeting held on 10th Oct. 2007 at Bristol.

Mr Kerr started by outlining the background. Much would be the result of work by the Severn Tidal Power Group, the Sir Robert McAlpine, Balfour Beatty, Taylor Woodrow and Alstom consortium. The first major study by Bondi produced EP (Energy Paper) 46 in 1981. A tripartite study, EP57 - 1989, costing £4 x106, defined the present scheme. A Definition Study was produced in 2002 for the DTI. If work started soon, the scheme could be producing power by 2017 - the La Rance Scheme at St Malo in northern France is already forty years old.

Severn Barrage Addressing the technicalities he outlined the various options, showing that "ebb generation" was preferable to "flood" or "two-way". Positioning proposals ranged from The Shoots, just north of the first Severn crossing at Aust, clear of significant shipping interests, right down to a north-south line slightly west of Minehead. The preferred scheme has the barrage running approximately NW from just south of Brean Down to Lavernock Point south of Cardiff, via Steep Holm. The anticipated annual output would be 17 TWh, representing approximately 5% of the UK total consumption, from an installed capacity of 8.64 GW. The barrage would make no contribution to the "renewables" obligation of the UK of 15% by 2015, but could provide the whole 17 TWh of the next tranche to 20% by 2020, provided it is sanctioned soon. Electricity costs might be 6-7 pence per unit.

In 1989 the projected capital cost was £8 billion, rising to £14-15 billion by 2005, but re-estimating would be essential because of various changes since then. The environmental lobby feels neglected, but in 1989 50% of the cost of the estimates was spent on seventy environmental studies. While there would be environmental negatives, there would be a significant number of positive outcomes. There may be an environmental balance achieved, but all issues would be studied. He emphasized that openness is a prerequisite for success in a project of this magnitude.

The barrage would be able to carry a road and rail link if factored in early, but there are doubts about this. The generator cells would necessarily lie in the deepest parts of the channel and would be formed from prefabricated caissons 80m square. These would house the total of 214 generators driven by 9m diameter bulb turbines, a tried and tested 40MW design. After a 4 year re-appraisal, construction would take six years and 200,000 man-years, providing 35,000 jobs at the peak and leading to between 10,000 and 40,000 permanent new jobs in the region around the estuary. [There is some background information, replicating some of Mr Kerr's illustrations, at www.reuk.co.uk/UK-Hydro-Power-Stations.html .]

Mr M Hield opened the questions, giving us a considerable résumé of his studies of the scheme. He covered issues of sediment, debris, flooding, sourcing materials and wind-power. The remaining questions were very wide ranging, mainly on environmental issues, from sourcing and transporting the fill material to the effects of the works on the local infrastructures, but also to considering alternative generation methods and, last but not least, the question of finance and ownership.

The definitive answers to many would depend on studies yet to be determined, but Mr Kerr was very clear that everything that could be affected would be considered. He was clear that the majority of the materials required would come by sea, the volumes rendering vehicular or rail transport uneconomic.

As John Conybeare, Chairman of RPEC, chaired the meeting, David Hutton, Chairman of SWEHS, proposed the vote of thanks to which the audience of 84 responded enthusiastically.

Andrew Smith

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