Silt laden Severn water - all this fine silt will be deposited if the flow is forcibly reduced

The Severn: we don’t have to dam it

02.01.09

There’s a widely-held view that, to extract power from the Severn Estuary, you don’t have a choice: you have to build a large-scale barrage such as the Cardiff-Weston or the Shoots Barrage. If the environmental cost is catastrophic, it’s too bad we have to make sacrifices.

But we don’t. There are superior, lower impact alternatives that can do the same job, without the environmental damage.

A new generation of tidal turbine
A new generation of tidal turbines, being developed at Exeter University with funding from BERR (the Department of Business Enterprise and Regulatory Reform), has the potential to match the output of any barrage proposal - with very low environmental impact. And, crucially, without damming the river.

The moorable MRev Lift and Drag turbine is ideally suited to the Severn as it can be deployed in shallow depths and a wide range of flow speeds. Its compact size and flexibility means turbine arrays can be tailored precisely to a location. It also works on the flow and ebb (barrages only work on the ebb), producing a much smoother 24-hour power output cycle than barrages.

The turbine’s exceptional efficiency means that it could match the power output of any barrage proposal. And, unlike a barrage whose lifespan could be severely curtailed by silting, it could go on and on providing power, as a truly renewable energy source.

The problem with silty estuaries
Supporters of the Severn barrage often cite the small-scale success of La Rance in Brittany. Sure, it has worked well, but La Rance is not a silty estuary. Ask the Canadians about the Bay of Fundy and you get a different picture. Over there, silt has caused massive problems. No barrage proposal has satisfactorily addressed the massive problem of silting. In the case of the Severn, it would impede the efficiency of a barrage and reduce its useful working life. In short, barrage tidal power on a large-scale in a silty estuary is not a proven technology.

The need for transparency and scientific objectivity
As the debate moves on, one thing is absolutely essential. Tidal power solutions must be assessed on the grounds of technical efficiency, financial cost and environmental impact. It should be recognised that some of the engineering consultancies and sponsored “academics” involved in the consultation process have a vested interest in the construction of a multi-billion pound barrage. Can their advice be treated as wholly objective?

2 comments so far

Hi Stuart. I’m at student at Cardiff University and we have been discussing some of the matters you mention above. We wanted to watch a documentary about this at our next Uni meeting. It was on BBC Wales’ Week In, Week Out last year hosted by Jonathan Porritt. Do you know anyone who has a copy of this? It used to be on iPlayer. Ian

Hi Ian, have a look at my comment on the program here: http://saveoursevern.org/archives/31

Hello Stuart! I’m a high school student at a and I was looking into this new 3rd generation of tidal turbines for a GIS project. However I’ve been unsuccessful in finding out the velocity or volume movement of water in order to move these new barrage free turbines. If there is any way you could share that information or send me in the right direction it would be greatly appreciated.

Hi Dan, contact Alexei at www.aquascientific.com, he’ll be able to give you technical details.



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