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Will the new fesibilty study into the Severn Barrage be the first steps towards construction or another false dawn?

Secretary of State for Business John Hutton breathed new life into the long awaited Severn Barrage tidal power scheme last week by announcing a feasibility study into it.

He also said he would explore other options for tidal power in the Severn Estuary.

The significance of the announcement for groups backing tidal power in the region cannot be underestimated. It has been a long time coming.

Leading the pro-barrage lobby is the Severn Tidal Power Group (STPG), a consortium of Sir Robert McAlpine, Taylor Woodrow, Balfour Beatty and Alstom. This was first formed in 1981 to carry out engineering and environmental studies into a 16km barrage spanning the Severn between Cardiff and Weston-Super-Mare.

STPG's findings were published jointly with the Government in 1989, but subsequently fell from consideration following privatisation of the electricity industry in 1990.

In a separate move, Parsons Brinckerhoff examined the possibility of building a barrage smaller than STPG's proposal in 1989. Again the project was shelved following privatisation. The consultant only recently revived its Shoots barrage proposal, located further upstream than STPG's near the second Severn crossing, when last year’s Energy White Paper hinted at revived political interest in tidal power.

It is easy to understand why tidal power has now reappeared on the political radar – it is a clean, renewable source of energy that is more predictable than wind power and offers a secure supply of energy at a time when the UK is becoming increasingly dependent on foreign gas imports.

Given that in March, European Union leaders set a target for 20% of member nations' energy to come from renewable power by 2020, it is also easy to understand why STPG's proposal in particular is the main focus of the forthcoming study. Its project could provide 5% of UK electricity demand .

On the other hand, the barrage proposal comes with significant environmental concerns, not least concerning the impact on wading birds.
One might expect STPG members to be cynical about Hutton’s announcement after 26 years of frustration but, on the contrary, STPG spokesman and Sir Robert McAlpine engineer Roger Hull is full of optimism. He says he is delighted with the prospect of a new feasibility study.

"The key thing now is to make sure the private sector is involved," says Hull of the mammoth £14bn proposal. "It's going to be built by the private sector, so the private sector should make the business case."

After the publication of the Energy White Paper, STPG, together with PB, wrote to the Government in a bid to ensure any investigation of tidal power was led by power companies.

Hull adds: "There will also need to be construction companies like ourselves involved, from the City, consultants hired to carry out environmental studies and environmental groups themselves."

Hull maintains that to make the most of the opportunity that the study offers, it must be comprehensive. This means that, in addition to the companies involved with the study, there ought to be a steering panel of politicians, engineers and environmentalists.

"We need to come out of this with one study with both sides happy they have been listened to," says Hull.

"If either of the pro-barrage or environmental camp isn’t properly included they will go away and do another study, and the last thing we need is a series of studies."

Hull anticipates that such a comprehensive study would take two years. Under STPG and Parsons Brinckerhoff's proposed format, it would run in two phases.

First, there would be a six-month "showstopper" phase, looking at things like UK and EU environmental legislation that could potentially prevent schemes like STPG’s. This would also look at a wide range of tidal power options and make recommendations on those to carry forward for further examination.

This report would then be handed to government to consider for three months before the second phase – a 15-month detailed examination of a small number of possible schemes.

Hull's desire for a feasibility study that leaves no stone unturned is common in many who see the great potential in harnessing the Severn’s natural power – it has a tidal range of 14m, the second largest in the world after the Bay of Fundy on Canada’s east coast.

The greater the tidal range, the more pressure is exerted on turbines when water is released, making the Severn the most effective location for a tidal barrage in the UK.

Parsons Brinckerhoff planning and environment director Peter Kydd says his firm developed its Shoots barrage proposal because the opportunity to harness the Severn’s power ought not to be lost simply because politicians may be put off by the size and scale of STPG’s proposal.

"We are not against the Cardiff to Weston proposal," says Kydd. "But if it isn't deemed appropriate, there should be other schemes available for the Government to consider."

Due to its smaller scale and lesser environmental impact, the Shoots barrage is preferred by environmental groups (see box).

Last week, Friends of the Earth called on the Government to consider combining the scheme with tidal lagoons to achieve a similar generating capacity to the Cardiff to Weston-Super-Mare barrage without the loss of the Severn’s mud flats, deemed a Special Area for Conservation by the EU.

There are also concerns among the surfing community that a barrage would destroy the natural phenomenon that is the Severn bore, waves which travel upstream from the estuary. Kydd denies this.

"It wouldn't stop the bore – it would just put a price on it," he says. "To allow the bore to keep moving up the Severn it would mean keeping the sluice gates open, which might result in some temporary loss of generating capacity."


The Cardiff-Weston Barrage

At £14bn, STPG's barrage is the most costly option of any likely to be considered by the Government. It also offers the greatest potential electricity output Đ 8.64GW, the equivalent of two nuclear power stations.

The concrete dam-like structure would run from south of Cardiff to Weston-Super-Mare. Sluice gates would allow water to flow into the Severn’s tidal basin at high tide.

This water would be impounded until the water on the coastal side of the barrage had ebbed to its lowest point. Impounded water would then be released through the turbines to generate electricity.

It would also contain shipping locks to give access to the ports of Cardiff, Newport, Bristol and Gloucester.

Environmental objectors claim the barrage would ruin the natural habitat of several wading bird species that feed on the Severn basin's mud flats.

The Shoots Barrage

This uses the same technology , but on a smaller scale. It would be located further upstream where the Severn is narrower and cost £1.65bn to build. Generation capacity will be 1.05GW.

Tidal levels downstream would be similar to today, so it is preferred by environmental groups.

Tidal Lagoons

These circular concrete cofferdam-like structures are also preferred by environmental groups as they can be installed at the seaward end of the Severn and do not impound the estuary.

However, they would generate electricity in much the same way as a barrage does, allowing water to flow in through sluices gates, impounding it and then releasing through the turbines.

The challenge of building these concrete donuts without a land connection is likely to make them proportionally more expensive to build than a barrage.

Tidal Stream Turbines

These are simply turbines installed out at sea and are propelled by water currents.
STPG and PB see tidal stream turbines as a complementary, rather than competing technology.

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