Tidal

The August 2009 Cumbria Vision report said studies in the 1980s revealed that the Solway Firth and Morecambe Bay came second and third among UK estuaries, ranked for tidal potential. It is estimated that a 30-km tidal barrage across the mouth of the Solway could produce 5.5-8GW of power, which is only slightly less than a major Severn scheme. A barrage across Morecambe Bay could yield 3GW and a Duddon estuary barrage perhaps 500MW. Obviously, as there have been some major environmental objection to the Severn Barrage, these proposals would need to be carefully assessed.

Cumbria Vision said proposals which were current in 2009 were for relatively modest schemes. Bridge Across the Bay (BatB) has been investigating the potential for free-stream vertical axis tidal stream technology in Morecambe Bay. The 18-km bridge (providing an enhanced communication corridor between Barrow and the M6 near Morecambe) would support arrays of turbines in the main channels, augmented by wind turbines. It is estimated that it might have a capacity of 200MW.⁽¹⁾ The feasibility study killed off the plans according to the Lancaster Guardian. BatB, a private company, said the bridge between Heysham and Rampside, near Barrow, would cost £677m to build and would generate annual income of £84m, including £11m from tolls and £63m from wind and tidal energy. The North West Development Agency’s consultants, headed by Regeneris, disputed these figures. They said the bridge would cost £2.34billion to build and would only generate £51.6m of annual income – £2.8m from tolls, £39.4m from wind turbines and £9m from tidal power. ⁽²⁾

The Solway Energy Gateway Ltd (SEGL) is proposing the construction of a tidal energy generating system between Bowness on Solway and Seafield, Annan, at the point where a viaduct once spanned the Firth. The Firth is one mile across at this ‘pinch’ point, with the estuary widening on either side of it, consequently the tidal flow becomes concentrated. It has been calculated that there could be a capacity for about 250MW at this point. And, given the experience of the La Rance barrage at St Malo in France predictable energy could be produced for 14 of every 24 hours. Significantly the preferred site is within 3 miles of a major electricity grid connection at the NDA’s Chapelcross Power Station, site which ceased generating in 2002 .

A 2009/10 feasibility study, by Halcrow, considered a range of options and alignments including: barrages, tidal reefs, fences and lagoons. The Feasibility Study, and on-going consultation, has made it clear that a scheme entailing confinement of water and permanent inundation of the salt marsh lands and estuary east of the alignment would not be acceptable. The technology now being proposed is called VETT (Venturi-Enhanced Turbine Technology) (previously known as Spectral Marine Energy Converter (SMEC)) which creates a slight rise in the upstream water level as a result of its operation. It is, in effect, a porous weir. VETT only slows the tide ebb and flow thus maintaining the existing biodiversity and ecology. The Solway has a rich and diverse ecology. As a consequence of its unique environment it attracts the highest ratings of protection (RAMSAR, SPA, SAC, SSSI). Therefore any tidal capture project will have to be very sensitively approached ensuring balance is maintained.

SEGL and another company VerdErg have combined forces to develop VETT for Solway Tidal and 12 smaller Hydro schemes throughout Cumbria and South West Scotland. Tests have been carried out in Utrecht in the Netherlands to determine if a prototype of the VETT passes environmental assessments relating to potential impact on the fish population. Nigel Catterson, chairman of Solway Energy Gateway Ltd, says the tests could not have gone better.⁽³⁾ The next stage is to find development partners for the Bowness-Annan project with a view to getting the scheme up and running between 2018 and 2020. Anticipated investment needed is between £300m and £400m, and the lifespan of the technology would be at least 120 years. Energy produced by the Bowness-Annan scheme would be between 180-200 megawatt capacity, with a consistent output of about 50 megawatts .

There was no proposal for the Duddon Estuary at the time of the Cumbria Vision report in 2009. However in 2010 Britain’s Energy Coast commissioned energy consultant Parsons Brinckerhoff to explore tidal options for the Duddon. Tidal barrages, fences, reefs and other innovative technologies were all considered along with the potential for a road link between Millom and Barrow-in-Furness.⁽⁴⁾ Previous studies have suggested the Duddon Estuary has potential to generate around 100MW of energy and cut 17 miles off the journey between Millom and Barrow. Britain’s Energy Coast view this as a project that would support the development of new nuclear reactors at Sellafield (because of the road link).⁽⁵⁾ The Parsons Brinckerhoff study⁽⁶⁾ concluded that a Tidal Barrage generating 280GWh per year is technically feasible and could be constructed by 2020 (at the earliest) at a cost of between £650m and £750m, but progress would be subject to many commercial and environmental considerations. Including a transport link would add approximately £140m to the cost.

There are also now plans being developed for a Tidal Lagoon in the Solway, similar to plans for Swansea. ⁽⁷⁾