Western Mail, 23 October 2013
It’s a real shame that Cardiff and Bristol councils are together exploring lagoons instead of the Cardiff Weston Barrage for the Severn estuary.
Lagoons in the Severn would produce only a fraction of the enormous power of the barrage, which is the only way of harnessing the full potential of the estuary.
For example, the lagoon proposed for Swansea Bay would generate one 50th, less than two per cent, of the barrage – and its electricity would cost twice to three times as much.
The power generated by tidal range technology, which includes lagoons and barrages, is proportional to the area enclosed times the height of the tidal range.
A lagoon has to build a relatively long perimeter wall to impound an area of water – in Swansea’s case, a nine kilometre wall – to create an area of five square kilometres.
The barrage, by contrast, only needs an 18 kilometre- long wall to enclose an area of 570 square kilometres: twice the length to enclose almost 100 times as much area.
Lagoons are simply not cost-effective, which means that electricity from lagoons will be much more expensive. Small projects like Swansea could easily complement the barrage, but Cardiff and Bristol are chasing an illusion if they imagine lagoons are a serious alternative.
Cardiff and Bristol suggest that lagoons take less space. But the Swansea lagoon is the size of 1,500 football pitches. That is massive. Yet it would take 50 of them to equal the power of one barrage. Where in the Severn – or the UK, for that matter – could we fit 50 lagoons of that size?
It is often claimed by wildlife and environmental groups that a lagoon will not have as much impact on the environment as the barrage. Obviously that would be the case for one lagoon – but what about 50 cluttering the estuary? What would the impact be then? Unless of course this cop-out option is not really about harnessing the full power of the Severn, merely a fraction of it.
The truth about lagoons, according to experts, is that we don’t know what the environmental impact will be. What will be their effects on tidal currents, waves, suspended sediment, sediment deposition, coastal morphology and water quality? We simply don’t know – particularly if we built so many of them, cluttering the estuary and affecting navigation for ports like Bristol, where the barrage locks allow easy shipping.
But we do know the environmental impact of the barrage: this has been studied and modelled for years, and solutions to any impacts on fish and bird life have already been developed.
We need to think seriously about energy. Demand for electricity is increasing and our supply is decreasing. According to the government, by 2025 there will be a 60 terawatt-hour gap between electricity supply and demand – that is 15% of our electricity consumption.
Where will that come from? What is the point of investing in expensive technologies that generate miniscule amounts of electricity? Why should we spend time building a lagoon that generates one 50th the electricity of a barrage, with electricity that costs two to three times as much?
The barrage would generate as much electricity as three to four nuclear power stations and at around the same cost. In addition it has a lifespan of at least 150 years, far longer than any other power plant – offshore wind farms last for 20 years, nuclear power stations like Hinkley for 60 years.
Do we want to keep the lights on? Are we serious about combating climate change? If we do not make big decisions now, in a few decades’ time, when parts of Somerset and South Wales are under water due to sea-level rise, the largest ships refuse to navigate the dangerous estuary waters up to Bristol Port, and the estuary is clogged with lagoons, our children will ask why we didn’t think long-term and prevent it all with the barrage.
Lagoons will not protect against sea level rise, unlike the barrage, which will defend 500 square kilometres and 90,000 properties from flooding.
At a time when our energy policy is in disarray and the costs to consumers are escalating, when our nuclear industry is in turmoil and being sold to France and China, and when the government wants to risk polluting our water table exploring for shale gas, we need big, cheap, long-term solutions – not the short-termist tokenism of lagoons in the Severn: a code for ‘do next to nothing’.
The answer is for city councils like Cardiff and Bristol to join the Welsh Government in getting behind the barrage, and its £25bn of private investment, (at no cost to the Treasury) generating 50,000 jobs, and putting Britain in the lead of bi-directional turbine technology.