Severn Estuary reef 'greener and more powerful' than barrage plan

AN alternative to proposals for an energy generating barrage across the Severn Estuary has been put forward by a Cornwall company which instead wants to build a ‘Severn Tidal Reef’ from Minehead to Aberthaw, in Wales.
The new scheme (illustrated, right, and below) is being promoted as a ‘totally new concept in tidal power generation’, by Joseph Evans and Sons Ltd, of Launceston.
Company owner Rupert Evans said the 12-mile reef plan was a ‘greener’ alternative a proposed 10-mile barrage between Cardiff and Weston-super-Mare.
Mr Evans said construction of the reef would not harm birds, fish, or shipping movements and would ensure fish species were unharmed by allowing safe passage through its proposed wind turbines.
The scheme is among 10 projects which the Government is assessing in an ongoing feasibility study into Severn Estuary tidal power.
Mr Evans said: “The reef was designed specifically to not harm the environment.
“I am even confident a canoeist would be able to pass through the turbines unhurt as they are slow moving and large.
“The reef is not being opposed by the Stop the Barrage Campaign or the various fishery groups because it is specifically designed so as not to cause damage to birds, fish, or to hinder shipping.
“The Severn Tidal Reef Project is a totally new concept in tidal power generation with the prospect of being environmentally benign.”
Mr Evans said the reef would generate as much, or even more, electricity than the Cardiff to Weston-super-Mare barrage.
It would include low visual impact and disruption, reduced risks of flooding, and maximum power generation.
“Unlike other monolithic tidal barrages designed to hold back the full height of the tide - the second highest in the world - the reef works with only two metres of fall but ‘slices off’ the power over a much longer generation period that is much easier to match to the peaks in electricity demand,” said Mr Evans.
“The full range of the tide is harnessed by a large number of simple low-head turbines along the 12-mile route.
“Massive, yes, but more economical in materials than the barrage or the ‘lagoon’ proposal, on account of the shape of the structure and very low pressure difference.
“The small difference in level between the sea and the estuary is critical when it comes to shipping, which can pass through opening sections of the reef on their way up to Avonmouth, a port in the midst of a massive redevelopment plan to accommodate the latest generation of container ships, and where any delays can be very expensive.
“The small difference in level also facilitates the safe passage of salmon and other fish through the special turbines, something that is not possible with conventional turbines with their high pressure drop and sharp-edged high-speed runners (rotors).
“Another unique feature is the ‘Active Tidal Control System’ that would allow the modification of the high water levels from tide to tide.
“A sophisticated computer system would know what high tide, even storm surge, was expected, and optimise the power extraction or free flow of water through the barrage to best meet the peaks in power demand, meet the navigation depth requirements for particular ships, and protect the wildlife and habitats by obtaining the right degree of variation in water levels.”