Severn barrage: tidal power from shallow lagoons versus strip barrier

Severn barrage: Row breaks out over UK's biggest renewables project
A plan to build shallow lagoons fitted with turbines rather than a strip barrier across the Severn would generate equal amounts of electricity at a far lower cost, say campaigners
John Vidal, The Guardian 5 Jan 09;

Government consultants have been accused of miscalculating the costs of a project to generate vast amounts of green electricity in the Severn estuary, promoting a 10 mile-long tidal barrier strongly backed by ministers in preference to a scheme that engineers and environmentalists say is far less damaging.

The US engineering firm Parsons Brinckerhoff has been hired by the Department of Energy and Climate Change (Decc) to assess technologies that could meet, from the Severn estuary, up to 7% of the electricity consumption of England and Wales. Its feasibility study for the estuary, which has the second highest tidal range in the world, has been sent to ministers, who will soon announce a shortlist of potential schemes based on the assessment.

Finding a way to harness the power of the Severn's tides is important as it would represent a big step towards Britain's target of generating 35% of all electricity from renewable sources by 2020.

Sources in Decc say the firm favourite is the 10-mile barrier, which would span the entire estuary and is costed at about £14bn. Parsons Brinckerhoff (PB) said the barrier could generate between 5GW and 8.6GW of renewable electricity at a cost of about 3p/kWh, but that it would impede shipping and lead to permanent flooding over more than 100 miles of shoreline.

Ministers have already called the scheme "visionary" and a "trailblazer for clean, green energy".

But correspondence seen by the Guardian shows that a row erupted between PB and a company promoting a scheme that environmental groups and other engineers claim would be far less damaging, as well as cheaper and more efficient.

Tidal Electric wants to generate electricity by using tidal lagoons built on the estuary floor from rock. Up to 13 lagoons would be dotted around the Severn estuary, not across it. These would trap water at high tide and release it later through electricity-generating turbines.

Studies carried out by the engineers AS Atkins, for Tidal Electric, have suggested that the lagoons could generate twice as much power, per square mile impounded, than the barrage, and therefore generate about 25-40% more energy without damaging the shoreline.

However, the plan sent by PB to ministers says the tidal lagoon option would be eight times more expensive than the barrage scheme and would not generate as much power.

But Peter Ullman, chief executive of Tidal Electric, said: "PB has made huge miscalculations. They have submitted [to ministers] cost-numbers on power from tidal lagoons that are roughly 800% higher than all the previous studies of tidal lagoon power conducted by UK engineering giant WS Atkins and corroborated by AEA Technology, Ofgem and Rothschild Bank. They have arrived at their extraordinarily high numbers by ignoring the technology developer's design parameters and introducing their own design."

One key issue is that Tidal Electric plans to site the lagoons in shallow water, while PB assumes they would be built – at a higher cost – in deeper water.

Tidal Electric is backed by many leading environment groups, including the Royal Society for the Protection of Birds, and Friends of the Earth, as well as a vocal west country lobby, which believes a barrage would be ecologically and socially disastrous. According to the Bristol-based group Stop the Barrage Now a barrage would add to local flooding, reduce fish stocks, damage bird life and destroy the Severn bore, as well as ruin mudflats across an area of more than 77 sq miles. They say a barrage would impede shipping, adversely affecting ports such as Bristol, Sharpness, Gloucester and Cardiff, and put at risk thousands of jobs.

A PB spokesman said: "We are unable to comment on Mr Ullman's complaint, but it is important to stress that during the selection process all options have been technically assessed to a common engineering and cost baseline.

"The same technical and energy yield approach has been applied to all options and the process and outcomes have been subject to peer review. The selection process is reviewed by an independent panel of experts appointed by Decc."

In correspondence with Tidal Electric, seen by the Guardian, PB executives note that the consultation will continue: "There [will be] ample opportunity for dialogue to continue even though the public consultation documents are in the final stages of preparation. The public consultation process provides you with the opportunity to formally respond to the consultation documents, which will include our appraisal of the long-listed schemes. If the offshore lagoon concept is shortlisted, specific optimisation of proposals will be carried out in the next phase, which will require further dialogue."

A range of barrage studies were made between 1974 and 1987 at a cost of £65m, out of which a specific Severn barrage scheme was drawn up by the Severn Tidal Power Group. A revised report was published in 2002 but all the plans were rejected at the time as being too expensive or too ecologically damaging.