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Tidal Power Update in Cardiff

At the Welsh Renewable Energy Conference in Cardiff in November 2006, Morgan Parry of the World Wildlife Fund (WWF) took on advocates of the Severn Tidal Barrage including its pioneer, Tom Shaw. Robert Kirby described how ecology in the La Rance estuary is flourishing post-barrage, but in fact blockage of that estuary during construction and a strongly reduced salinity wiped out the pre-barrage water life.

Morgan Parry argued the comparison estuary is NOT the tiny La Rance (20 times smaller in area and 30 times less powerful than the Severn) but the Bay of Fundy, Canada. There the existing small barrage has found problems in fish loss and shoreline erosion downstream, causing plans for a larger barrage to be dropped.

He reported that the Countryside Council, English Nature and the Environment Agency have come out strongly critical, saying that the Severn barrage would cause "irreversible impacts to features of international importance" (Engineering our future nature: the dilemma of the Severn), as detailed below.

The view of the statutory agencies on the Severn Tidal Barrage

• The Severn Estuary is an internationally important habitat with unique ecology
• Nature and scale of barrage proposals would cause irreversible impacts to features, species and habitats of international importance
• Direct impact on Severn Estuary Special Protection Area (SPA), proposed Special Area of Conservation (pSAC), and the rivers Wye and Usk SACs
• A Severn Barrage development would not be possible within the current legal framework provided by the EU Habitats and Birds Directives
• Cannot envisage how required compensatory habitat could be provided to replace those that would be lost
• The case for a barrage is being promoted without proper consideration of other, potentially less environmentally damaging options
• Water quality would be affected as a direct result of the barrage (through the) modification of the sediment regime (and) nutrient flux
• Barrage would fundamentally alter the basis for determining appropriate limits for discharges to and abstractions from the estuary and the rivers that feed into it
• Existing defences and new strategies in preparation will manage the flooding impacts of climate change without a barrage
• May be a downstream increase in vulnerability to tidal and storm surge flooding and consequent erosion caused by reflected tidal waves at the barrage face
• Major environmental impacts due to the vast amounts of materials required
• Substantial ancillary and infrastructure development including the need to modify or build new port facilities
• Difficult to envisage how the proposal would fit with the requirements of the Water Framework Directive, e.g. requirement to aim to meet good status by 2015
• A major programme of predictive environmental studies will be needed, (taking) several years to complete

English Nature, Countryside Council for Wales, Environment Agency 2006

Morgan Parry, WWF Cymru
"We cannot take the attitude that Climate Change is so important that we can trash habitats."

Morgan compared in general terms four types of tidal power - Tidal Stream Energy devices, Tidal Fences, Tidal Lagoons and Tidal Barrages. The impacts on wildlife and sediment regime, the resources needed, the uncertainties and construction times increase with type in this order and WWF argue for tidal stream turbines for minimal impact and expanding by adding modules. Details are reported in his presentation.

Peter Fraenkel described the current advances in tidal stream devices, mainly his own company's Seaflow test-of-concept and Seagen prototype destined for Stangford Loch Narrows. He showed pictures of the turbines, gear-box and monopile with construction details and under test. The 1.2 MW prototype will come out at £5200/kW and electricity cost of 16.2p/kWh. His presentation is not on any open website.

Peter Fraenkel said the next stage is planned as a demo project in the Anglesey Skerries (NW of the island) at 10.5MW and 11.7p/kWh, to be followed by a 'commercial' 51MW array producing at 7.9p/kWh (independent costing by Black & Veatch). For the next generation, he envisages moving to larger turbine rotors than the current 8 metres and to a fence-like array sharing a base.

Another project in the offing is a smaller Severn Barrage, crossing the estuary near the second road crossing and called the Shoots Barrage. This smaller-scale 1000MW Severn barrage scheme would cost about £1800M and produce 20% cheaper electricity. PB Power (of Parsons Brinkerhoff Ltd.) say it's more practical than the larger barrage, at a tenth of the size. 'The big barrage has had a lot of publicity and money poured in over the years, but our barrage lends itself to a high-speed rail link across the estuary and is much more connectable into the grid.' Their brochure (not on the internet) points out the much reduced environmental impact, non-interferance with major shipping to Cardiff and Bristol, and co-existence with tidal stream projects in the mid estuary. Construction would take 4 years rather than 7 years and relatively little building aggregates.

The Sustainable Development Commission has the task of reviewing all aspects of developing tidal power. They say the review
'will look at the costs, the environmental impacts, the social side of it, whether it can actually be done in the UK's energy market, and how it fits into the UK power grid. The intention of the DTI is to give it a clear idea of where they should prioritise in future. If we came out heavily in favour of going in a particular area then that might encourage a review of a particular option.'

report by Max Wallis, Cardiff

Swanturbine's system (drawing above) works like an underwater wind turbine. The device is submerged so it cannot be seen and it only has one moving part. www.swanturbines.co.uk

The TidEl system has floating turbines chained to the seabed www.marinet.org.uk/refts/tturbine.html

Statkraft (Norway) has twin turbines submerged under a floating anchored steel supporting structure www.marinet.org.uk/refts/statkraft.html

The SeaFlow and SeaGen devices are pictured at www.marinet.org.uk/refts/cirianov03.html and www.marinet.org.uk/refts/wavetidalsymposium.html

LINKS

Renewable Energy Conference 4th March 2004

The Dilemma of the Severn   Report by Morgan Parry

Conference Presentation   by Morgan Parry (Powerpoint)

Report from Hemscott Group   UK govt's Sustainable Development Commission launches review of tidal power