By far the largest and most controversial project contained in the Energy Department (DECC) consultation is the Cardiff-Weston Barrage. This would cost around £20.9 billion and generate 16.8 terawatts hours per year or some 5% of UK’s electricity consumption. It could save some 7.2 million tonnes of carbon dioxide a year.
There are two proposals for impoundments, each adjacent to shorelines of the estuary. The Fleming lagoon, on the Welsh shore between Newport and the Severn road crossings, would cost around £4 billion and could generate 2.3TWh/year. The £3.8 billion Bridgwater Bay lagoon on the English shore between Hinkley Point and Weston-Super-Mare could generate 2.6TWh/year.
There are also two smaller barrage proposals. The £3.2 billion Shoots Barrage, near the Severn road crossings, generating some 2.7TWh/year, or almost 1% of UK electricity. This would be equivalent to a large fossil fuel power station.
The smaller £2.3 billion Beachley Barrage, further upstream, and upstream of the Wye, would generate around 1.6TWh/year.
Mr Miliband also announced an additional £0.5m of government funding to help bring forward less developed, more innovative options including tidal reefs and tidal fences.
A final decision is still some way off, with a second consultation due in about 2010, taking into account progress in more novel options.