What Price Power from the Severn?

Gwyn Williams, Head of Reserves and Protected Areas, contributes this blog about the Severn Barrage, following this week’s publicity around a new proposal by Hafren Power:

With a week gone, Martin’s prediction that it was likely to be a quiet fortnight is looking a little insecure, given the coverage over the weekend [19 August] to a new proposal from Hafren Power for an energy-generating barrage across the Severn!

In thinking about energy, the RSPB starts from a similar place to most, including those who support a Severn Barrage: we need a renewable energy revolution to combat climate change. However, if energy developments are not to put even more pressure on a natural environment that is already deeply stressed and further threatened by climate change, we need to make sure we use the right renewables in the right places.

The potential for energy generation from the Severn has attracted engineers since Victorian times. The most recent DECC study focussed on whether a scheme generating maximum power using current technology could be economic, and if so with what side-effects, including - very much as a secondary consideration - impacts on the natural environment. The RSPB strongly criticised this approach: we thought that the starting point should be to look for a type of technology which could provide maximum energy output from the Severn for minimum environmental harm. It took two years and a small forest of paper to conclude that construction of a high-head barrage with high-velocity turbines would be too costly, and result in big negative environmental side effects.

Now Hafren Power has resurrected the idea, with a lower-head, low-velocity turbine concept, that it believes can still produce c5% of UK electricity needs, but with less harm to the environment than the high-head, high-velocity options which have been the focus of barrage proposals to date. The company has now presented its ideas to the Prime Minister, David Cameron, in a meeting brokered by ex-Welsh Secretary, Peter Hain MP. Mr Cameron is reported as being very interested and has instructed officials to look into the project.  Powerful sponsorship indeed!

The undertaking remains mammoth – a wall over 18km long, housing over 1,000 turbines of 9 metres in diameter across an estuary with the second highest tidal range in the world.

The company claims the barrage can be built without up front public funding, and that it can raise £30bn needed without public money, using sovereign funds from Qatar and Kuwait. Its ask of the UK Government is that the electricity generated should be subsidised in the same way as offshore wind energy, and that time should be made available for the ‘hybrid’ Parliamentary Bill necessary to give powers to the company to construct it.

The big worry is obvious – that in order to give investors confidence to back the scheme, Government will reduce the scrutiny process to a minimum (think red-tape challenge, and all the proposals for planning reform!). We can expect the checks and balances on development projects created by the Birds and Habitats Directives to come under renewed pressure. It is also obvious that consumers will be expected to pay for the scheme through the new subsidy system that Government is currently designing as part of the Energy Bill, and that will be key to the scheme‘s viability. This will also have considerable implications for other forms of renewable power generation, given the current Treasury cap on renewable generation subsidies.

So what are the environmental concerns? The big one is that whilst a lower-head barrage should reduce the immediate loss of mudflats, which are the reason why the Severn is so important for wildlife, the geomorphological impact of the structure will be felt for many decades and quite possibly over several centuries – and could eventually result in an impact as severe as the high head option. Removal of so much energy from the Severn is likely to result in sustained erosion of mudflats and saltmarshes, as the estuary seeks to find a new equilibrium to match the conditions created by the presence and operation of a barrage. 

Once lifted by the tides, sediment is likely to be deposited into the deepest parts of the estuary in an attempt to reduce the depth of the channel. The result could be the loss of protective mudflats and the undermining sea-defences within the estuary - bad for wildlife and bad for people. The Dutch understand this well, having seen changes of this kind following the Eastern Scheldt barrage.

The risk of extinction of important fish populations has always been a major concern in relation to tidal power generation in the Severn. The threat to migratory fish from low-velocity turbines should be less, but to date we have not seen evidence to support this, and much will depend on the design and deployment of untested technology.

We continue to regard estuarine barrages with scepticism because of their high cost and potential for environmental damage.  However, as with the DECC study, we will seek to work constructively with Hafren Power to contribute to understanding of the implications of their proposals. A structure that will be with us for more than a century is just too big to get wrong!