Severn Barrage
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.
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.
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.
[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.
In 1971 a report by Dr Tom Shaw, a tidal Power expert and advocate proposed a barrage from Brean Down to Lavernock Point.
[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.
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.
above Cardiff and Bristol on the estuary—and so much smaller locks would be needed for upstream access to Sharpness and Gloucester docks as the large ports of Portbury and Avonmouth would be unaffected.
It would be built of rock fill embankment at the coastal sides (more like the proposals for "Tidal Lagoons"), but like the STPG would be sluice caissons and turbines with powerhouse in the middle section.
In April 2009 the Liberal Democrats produced a report called "A Tidal Solution—The Way Forward" that backed the Shoots Barrage along with a number of additional measures for power generation in the Severn Estuary.
[23] The STPG appraisal concluded that the electricity generated from the barrage would make the scheme economically viable if given certain "green" advantages, and that the environmental impact was acceptable.
However, since then global warming has radically altered the public perception of environmental damage; and soaring oil, gas and energy costs have made the economics of the barrage much more favourable.
Atkins commissioned by the RSPB) be significantly greater than for the Cardiff-Weston Barrage, and is in part a result of siting the structure at the "outer" Minehead to Aberthaw line, which roughly doubles the volume of tidal water available.
The SDC also commissioned a programme of public and stakeholder engagement, which included a national opinion poll and a series of local and regional workshops.
A publicly led project would enable the use of a low discount rate (2%), which would result in a competitive cost of electricity, and would limit the economic impact of even a very large-scale compensatory habitats package.
The study aims to gather and assess evidence to enable the Government to decide whether it could support a tidal power scheme in the Severn Estuary and if so on what basis.
In September 2010, The Observer reported that the government intended to rule out the possibility of public funding for a complete barrage, while recommending that further feasibility studies be carried out on smaller projects.
On 14 January 2014 it was announced that the chairman and Chief Executive of Hafren Power had resigned, putting an end to the Severn Barrage project.
[40] The Severn Barrage plans would provide a predictable source of sustainable energy during lifetime of the scheme, with claims of up to 5% of the UK's electricity output from the 10-mile version.
There would, though, be secondary knock-on costs from the tidal power project that might be met by the tax-payer, such as modifying existing ports, provision of compensatory habitat and dealing with environmental change.
[2] Some say that a large-scale barrage would create leisure-friendly water conditions behind it but with around 10 m rise and fall this would still be one of the largest tidal ranges in the UK bringing with it significant danger to any leisure users.
This blocks light-penetration and means that the Severn Estuary marine environment is actually a relative desert, in terms of both plant and fish life.
Any barrage would be likely to stimulate coastal erosion in some areas, and create a negative visual impact upon the landscape (subjective, similar to wind turbines).
The lagoons could be sub-divided so power would be generated at more states of the tide than a barrage, with lower peak output, giving economic advantages to set against the higher construction cost of longer barriers.
[64] This would attempt to maximise the potential power generated whilst allowing for shipping to reach Cardiff and Bristol without hindrance (through gaps at least 650 m wide) and wildlife to maintain their existing habitats.
[66] A second approach to a tidal fence being explored by VerdErg uses a different way of generating electricity called the Spectral Machine Energy Converter (SMEC).
One of the proposed routes for an Irish Sea Tunnel is from Fishguard, which would generate large amounts of extra freight traffic which the current Severn tunnel—already operating at capacity—could not handle.
If the barrage is built further west, any transport connection would instead link more isolated areas of the Devon-Cornwall peninsula with the cities of South Wales and the ports of Pembrokeshire.
