Severn Tidal Power Consultation

The government is consulting not about a final decision, but over which projects should be taken forward on the shortlist for further study — or which ones should be added. Marinet supports much opinion and local people in large majority who want the “mega-barrage” dropped from the shortlist:

  • Cardiff-Weston megabarrage, Lavernock to Brean Down
  • Shoots barrage, near the newest Severn road bridge and rail tunnel
  • Beachley barrage, just up from the river Wye
  • Fleming Lagoon, up from Newport attached to the Welsh coast
  • Bridgewater Bay Lagoon, outside the European-protected estuary

Many conservationists argue that the ‘tidal fence’ and ‘tidal reef’ proposals lower down the estuary (Aberthaw to Minehead) should be studied further, as they generate large amounts of power and can be run in tandem with lagoons, with little impact on nature conservation or interference with shipping etc.
Severn Tidal Power response — Outline basic case

First note there is much false information around, aimed at dividing environmentalists — must we sacrifice nature in the conservation-protected estuary for the sake of huge amounts of power, needed to combat climate change?

In reality, the favoured mega-barrage does not give “huge” amounts of power. The claim (Fred Pearce, New Scientist magazine of 18th April) that it replaces 6 coal-fired power stations is nonsense. That’s based on the maximum generation (8.6GW) but the average is little more than one coal-fired plant (1.4GW). Moreover, to fill in the gaps at incoming tides, it would require 3 such coal-fired stations serving as ‘slaves’. Pearce also states that 20 tidal current sites operating at the ”theoretical limit” would only just replace the mega-barrage, but that again is nonsense. The Pentland Firth alone is estimated to easily exceed the mega-barrage in power generation. And the official figures for other sites are pessimistic lower limits.

On the new PG assessment of the inner Severn options, the mega-barrage gives very costly electricity (15-20 pence/unit) as do the other barrages and lagoon projects. This makes it poor value compared with modular marine current turbines (8p/unit, decreasing with larger numbers) and wave power devices (12p/unit, decreasing).

The tidal fence and tidal reef alternatives (Aberthaw to Minehead) make little impact on the inner Severn conservation area. The ‘fence’ of marine current turbines uses technology now under test (in Strangford Lough) while the ‘reef’ is a new idea that allows shipping through without costly locks. Let’s argue for both to be added to the shortlist.

All the schemes that take up habitat in the inner estuary have to provide compensatory habitat elsewhere. While the consultants included costs of this, the possible areas are quite insufficient to compensate for the mega-barrage. The Conservation Agencies stated it will fail on this ground alone.

The mega-barrage can’t be built for many years, eg. 15 years till commissioned, longer than all others because of studies and permitting processes. In particular, it will be challenged through to Europe under conservation laws. Instead of wasting time and money in legal cases, let’s go for clearly feasible options.

With generation only on the ebb tide, the mega-barrage needs two or three fossil-fuelled ‘slave’ generators the size of Aberthaw power station to fill in the gaps. Proponents hope some storage system will be found, but any such system has a cost and loses efficiency, so raising the real cost as well as introducing a major uncertainty.

Options with secondary basins as with lagoons allow power to be used for pumped storage, as well as delivering power when required to meet peak demands (when TV ‘soaps’ end or TV football intervals). So keep these on the shortlist and study the real value of this storage and delivery flexibility.

Those who wanted the Lavernock to Brean Down barrage for a road link and potential for associated development find no support in the present assessment, which finds the extra cost for such a road to be huge. But the Shoots Barrage carrying a railway to replace the Severn Tunnel is quite feasible. Let’s say the road across and the fantasy of a Severnside metropolis should be completely ruled out.

The new argument for the mega-barrage is as tidal defence against high predictions of sea-level rise. But that makes it a different project, to be reassessed in a few years time when more definite predictions can be made for the Antarctic and Greenland icecaps.
Responses to Consultation (pdf files)

Further information: Marinet’s general briefing (against the mega-barrage) www.marinet.org.uk/refts/7estuarydebate.html

“Third Generation” tidal stream turbines — see the 16-page evaluation by Stuart Ballard of Save Our Severn here (pdf file).


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