Severn Barrage

Barrage locations considered over the years. The most westward locations around Ilfracombe and The Gower are not shown. Black indicates lines of most interest, with associated peak power generation at that location.

The Severn Barrage refers to a range of ideas for building a barrage from the English coast to the Welsh coast over the Severn tidal estuary. Ideas for damming or barraging the Severn estuary (and Bristol Channel) have existed since the 19th century. The building of such a barrage would be a huge engineering feat, comparable with some of the world's biggest construction projects. The purposes of such a project has typically been one, or several of: transport links, flood protection, harbour creation, or tidal power generation. In recent decades it is the latter that has grown to be the primary focus for barrage ideas, and the others are now seen as useful side-effects. Following the Severn Tidal Power Feasibility Study (2008–10), the British government concluded that there was no strategic case for building a barrage but to continue to investigate emerging technologies.[1] In June 2013 the Energy and Climate Change Select Committee[2] published its findings after an eight-month study of the arguments for and against the Barrage. MPs said the case for the barrage was unproven. They were not convinced the economic case was strong enough and said the developer, Hafren Power, had failed to answer serious environmental and economic concerns.[3]

Contents

  • History 1
    • Early projects 1.1
    • Bondi Committee – 1981 1.2
    • Hooker or Shoots Barrage – 1987 1.3
    • Severn Tidal Power Group – 1989 1.4
    • Severn Tidal Reef – 2007 1.5
    • Sustainable Development Commission – 2007 1.6
    • UK Government study announced – 2007 1.7
    • Corlan Hafren – 2011 1.8
  • Economic impact 2
    • Power generation potential 2.1
    • Construction costs 2.2
    • Local impact 2.3
  • Environmental impact 3
    • Tidal lagoon alternative 3.1
    • Tidal Fence 3.2
    • Effects of different site locations 3.3
  • Trans-barrage transport links 4
  • Opinions 5
    • Backers 5.1
    • Opponents 5.2
  • See also 6
  • References 7
  • External links 8

History

There have been numerous proposed projects over the years, initially to provide a safe harbour and more recently to generate electricity.

Early projects

Thomas Fulljames's own impression of his proposed Barrage

In 1849 Thomas Fulljames, a civil engineer and the county surveyor for Gloucestershire proposed a barrage from Beachley to Aust (now the site of the first Severn Bridge), a span of just over 1 mile (1.6 km). Since this was before commercial electricity production, the first proposals were based on the desire for a large shipping harbour in the Severn Estuary, road and railway transport, and flood protection.[4]

Diagram of a plan to harness tidal power on the River Severn circa 1921. Caption from Popular Mechanics Magazine 1921

No action was taken on Fulljames's proposals and three quarters of a century later, in 1925, an official study group was commissioned. An awareness of the large tidal range of 14 metres (46 ft),[5] second only to Bay of Fundy in Eastern Canada,[6][7] led to a proposal to generate 800 Megawatt (MW) of electricity at English Stones and although considered technically possible, it was prevented on economic grounds (then costing £25 million).[8] The viability was tested a few years later in 1931 when Paul Shishkoff,[9] a Russian immigrant, demonstrated a 300 horsepower (220 kW) prototype tidal generator at Avonmouth.[10] It included a novel mechanism for spreading the power output over 24 hours. The full barrage was estimated at £5 million at the time.[11]

In 1933 the Severn Barrage Committee Report (HMSO) from a committee chaired by Lord Brabazon recommended that an 800 MW barrage across the English Stones area would be the best option.[12] The work was interrupted by World War II and then revived in 1945 when engineers predicted an output of 2.2 terawatt hours (TWh) per year.[13] A further government study looked at barrage options in 1948 and estimated the construction costs at £60 million.[10] By the time of the next study in 1953 the estimated cost had risen to £200 million.

In 1971 a report by Dr Tom Shaw, a tidal Power expert and advocate proposed a barrage from Brean Down to Lavernock Point. The scheme was estimated to cost £500 million.[14] In 1975 the Central Electricity Generating Board (CEGB), published a study with evidence from Bristol and Salford universities for the Secretary of State’s Advisory Council on Research and Development for Fuel and Power.[15] As this was the era of cheap oil, the council established that a barrage could not be economically viable unless the energy situation deteriorated significantly.

Bondi Committee – 1981

Proposed location of Bondi Committee Barrage

After just such a deterioration (due to the Iranian Revolution and 1979 energy crisis) the plans were reinvestigated by the Severn Barrage Committee in 1981. This committee was known as the "Bondi Committee" (after Professor Sir Hermann Bondi). The committee investigated 6 possible barrage locations, from English Stones at the top of the estuary, down to a location largely at sea in the Bristol Channel between Lynmouth in North Devon and Porthcawl in South Wales. It produced a major energy paper,[16] which recommended a 10 miles (16 km) long barrage of concrete powerhouse between Brean Down and Lavernock Point, sluice and plain caissons together with sand and rock-fill embankments. It would have generated 7,200 MW on the flow of the tides (the largest barrage considered could have produced double that power output). This set of plans was strongly built on a few years later by the Severn Tidal Power Group.

In 1984 Wimpey Atkins proposed a smaller barrage at English Stones, in the hope of creating a smaller more economically viable project that would avoid the environmental impact of a large barrage.[17]

Hooker or Shoots Barrage – 1987

Cross section of Shoots Barrage turbine housing

This Wimpey Atkins 1984 study was criticised because it did not tackle the issue of siltingHL Deb, 07 March 1984 vol 449 cc263-5 and in 1987 Arthur Hooker OBE (a former partner of WS Atkins) in conjunction with Parsons Brinckerhoff prepared a revised barrage proposed at English Stones to better tackle this issue.

Parsons Brinckerhoff further updated their earlier proposal in 2006 and current estimates for this barrage (now known as the "Shoots Barrage") would cost £1.4 to £1.8 billion to build, and generate 2.75 TWh of power per year.[18] At the highest tidal range, it would develop a peak output of 1,050 MW, and 313 MW output on average throughout the year.