Severn Tidal Power - Latest Developments

The publication of the interim report by the Sustainable Development Commission on options for tidal power in the Severn (reported on previously on this blog) has resulted in the original list of ten projects (shown above) being reduced to five.

The five proposals for harnessing the tidal power of the river all involve tidal range technologies. This involves creating a barrier which is effectively a hydroelectric dam. The incoming tide is allowed to pass through the barrier and then held back behind it as the tide recedes. At or around low tide, the waters behind the barrage are released in a controlled way and passed through a series of turbines, generating electricity.

While barrages are walls built right across a river, lagoons are formed by irregular-shaped walls that have their two ends on the same side of the river as each other.


The five proposals, all of which use this tidal range technology, are as follows:

1. The Cardiff to Weston Barrage. This barrage would cost an estimated £19-22 billion and would produce approximately 4.8% of the UK's current electricity needs. As well as the cost, this barrage would impact on migratory fish in the Severn and would result in the destruction of 20,000 hectres of wildfowl habitat upstream, much of it internationally protected.
   
2. The Inner Barrage. Located near the Severn Road Bridge, this barrage would be identical in function to the one above, but being smaller would generate less electricity (1% of UK output) and cause less destruction of habitat (5,000 hectres).
3. The Beachley Barrage would be upstream of the point at which the River Wye enters the Severn, producing less energy than either of the above proposals and creating less habitat destruction. The price tag is estimated at £2.5 billion.
   
4. The Fleming Lagoon would have one end at Newport and the other at or near the Severn crossings. It would result in considerable inter-tidal habitat loss and would cost £4.9 billion.
   
5. Bridgewater Bay Lagoon. Stretching from Hinckley Point to Weston-super-Mare, this lagoon would be similar to the one above and would have similar cost and environmental impact.

The full text of the SDC report can be found here while a shorter summary for simple west country folk like me can be seen here. Once the information has been read and inwardly digested, members of the public are invited to respond and express their views before April 23rd 2009.

Tidal movements in the Severn Estuary are among the largest in the world, with water levels rising up to 14 metres from low to high tide.

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