Severn Barrage's Eight Gigawatts

If you want to imagine the Western Hemisphere’s equivalent to China’s Three Gorges Dam, look no further than the proposed Severn Barrage, which at peak output will deliver over 8 gigawatts of electricity, or about 50% of what the Three Gorges delivers. Even though the Three Gorges output decisively exceeds that of the Severn Barrage, if this massive civil engineering project is ever completed, it will dwarf every other power station in the world.

Environmental groups bitterly oppose the Severn Barrage, and if they are to strive for consistency, they certainly should oppose this monstrosity. The ten mile long dam will connect the English coast to the Welsh coast across the Severn Estuary, one of the largest, most precious, environmentally sensitive estuaries on Earth. Why on earth would any environmentalist support this project, or any tidal energy project, for that matter? The problem, of course, is we have to pick our poison – energy production, like food production – in a world destined to accomodate 8-9 billion people who aspire to live in peace and prosperity, is doomed to be dependent on commercial scale operations that are disruptive and potentially dangerous. Pick your poison. Nuclear? Hydroelectric? Fossil fuels?

The Severn Estuary and the
proposed barrage crossings.

The problem with tidal power certainly isn’t the scale – unlike wind turbines, which would have to be installed by the millions to make a dent in global power production, the Severn Barrage is a big deal. But to suggest the 8.6 gigawatt output is “equivalent to eight nuclear power plants” (presumably at 1.0 gigawatt each) is misleading.

Like other intermittant sources of energy such as wind and solar, and unlike nuclear power that operates continuously, tidal energy plants only operate at low tide, which is when the seawater sequestered behind the barrage during high tide can drain through the hydroelectric turbines. Like wind and solar, tidal energy has a “yield,” which in the case of the Severn Barrage is not quite 25%. In terms of actual average output, the Severn Barrage is only estimated to deliver 2.0 gigawatts of electricity, and at this point no serious discussion seems to be forthcoming as to how a fluctuation in grid input of 8.6 gigawatts is going to be offset. If there are designs that can smooth this massive energy flow, how much do they cost?

And what about the financial cost? At an average of 2.0 gigawatts of continuous power, the Severn Barrage will deliver about 17.5 terawatt-hours per year. Rounding up slightly from current estimates (because these projects never come in on budget), the entire project will cost about L 17.0 billion, or about $30 billion. Ouch! That equates to $15 billion per gigawatt-output, an amount that absolutely does not compare favorably to alternatives, including wind – installed, taking into account yields, probably half this amount or less – and certainly not natural gas, which can now be installed at about $1.0 billion per gigawatt output.

At $15+ billion per gigawatt (over $15.0 million per megawatt) installed, the Severn Barrage is a civil engineering boondoggle, being popularized based on global warming alarm and desire for energy security. While energy security is a compelling concern, it should be addressed in ways that reflect fiscal reality. A tidal energy system that costs $15 billion per gigawatt is not a financially competitive investment, even when compared to other alternative energy options. Try marine current turbines, which operate underwater on the ocean floor, or offshore wind – almost anything will cost less than the Severn Barrage, and almost anything would be less of a blight.

The location of the Severn Estuary
in the southeast of the U.K.

While we don’t dismiss global warming concerns, only remain committed to publishing credible material from the skeptic community (read our Climate section), one must consider this: It is virtually impossible to eliminate CO2 emissions to the levels the alarmist scenarios declare we must to avoid catastrophe.

It isn’t going to happen, no matter how many precious estuaries environmentalist policies destroy, or rainforests that environmentalist policies burn to grow subsidized “carbon neutral” biofuel. Global warming alarm is being used quite effectively as a trump card in almost every policy debate imaginable, but by the alarmists own logic, it is an utterly futile exercise.

Environmentalists should hope whatever climate changes we’re experiencing are from natural cycles, and return their focus to things that they can influence – the world’s estuaries and rivers, forests and floodplains, wilderness and wildlife; protecting precious natural beauty and eliminating genuine pollution.

Related Links:
Severn Barrage (Wikipedia)
Severn barrage will be costly ecological disaster (

6 Responses to “Severn Barrage's Eight Gigawatts”
  1. Alan Ford says:

    When proposing an argument could you at least please be sure to present all the facts for both sides. I am not sure whether you are deliberately “forgetting” those facts that don’t best aid your argument or have not taken the time to gather all the facts.

    There are a number of different proposals and designs under discussion, some of which can, as you state, only operate at low tide. However, others under discussion are capable of operating for 22 hours a day with only the hour of “slack tide” twice a day when turbines would be idle.

    Using one of these designs greatly changes the facts for much of your arguments so I suggest you either improve your memory or your fact finding capabilities before you next provide what has proven to be a very biased argument based on partial facts only.

  2. Ed Ring says:

    Alan: You make a good point – I wasn’t aware of proposed designs for the Severn Barrage that will smooth the power delivery, but I’m pretty sure the annual estimated output of roughly 17 terawatt-hours is accurate – which equates to an average output of 2.0 gigawatts. And for $30 billion, that is an extremely expensive energy option. My main argument is not regarding the load balancing, it is regarding the installation expense. In any event, you are welcome to provide links to whatever more in-depth information is available online, and I have edited the post somewhat based on your comments. We value our credibility and welcome continued discussion here on the Severn Barrage.

  3. As the builder of the first ‘Tidal Current Turbine’ in the UK some 15 years ago and proposer of the ‘Severn Tidal Power Reef’, I would suggest that there are more than one way of harnessing the tides of the Severn, and that it is possible to do it in an environmentally friendly way as well as an economic way. I agree that the power available is equivalent to two or three nuclear power plants, but remember that that it is two or thee plants every thirty years or so for ever! (not just the life of a reactor….and you don’t have the waste or danger of terrorism….so the price is not just financial. I agree with what you say about the Cardiff-Weston ‘big barrage’ but most people do not differentiate between the different proposals, so all get tarred with the same brush, which isn’t exactly helpful. What I am proposing is a cooperative of all those who are involved, from wildlife to navigation and the engineering is designed to deliver a benign solution….not easy but possible.

  4. Ed Ring says:

    Rupert: Thank you very much for your comment. If you would like to forward information regarding alternatives to the ‘big barrage’ I would be honored to publish them here – if that is of interest to you email

  5. Neil Law says:

    Thanks for publishing the article . As Alan Ford says, it DOES have shortcomings, but on an issue of such complexity, that is inevitable. I submitted a report to the UK government’s Strategic Environmental Assessment on the issue.

    I am one of the bore riders/tidal bore surfers, and I would have to say that initially I was out of step with my surfing brethren, in that I was prepared to contemplate losing the Severn Bore for the greater good. However, I am also a resident of the Severn Valley,and after the dangers my family and I had to face after the floods of July 07, I began my own research. I downloaded and read the whole of the “Turning the Tide” report by the Sustainable Development Commission, and I started from there.

    I have looked at the barrage which is being used as a comparison to justify the Severn proposals: La Rance, near St Malo. I have compared that to both the Severn estuary and other tidal power projects in the Bay of Fundy across the Atlantic, and I have consulted academic opinion on the matter. What I have found out is that La Rance is a spurious comparison. The river across which it is built carries little or no silt. The Severn, on the other hand, carries an enormous silt load. The experience from projects such as Moncton in New Brunswick is that when a fine-particled sediment such as this meets seawater, it forms liquid mud. That is ok, until the water is stilled, or slowed. In building any form of tidal power plant, we are attempting to mine energy from the flow, or as in this case, the head of the tide. When the flow is reduced by half, the energy is reduced by an order of magnitude. And the energy within the flow is directly related to how much sediment it can carry.

    When this liquid mud settles out, the action of marine micro-organisms makes it incredibly persistent and sticky: more mud will stick to it.In fact it has been shown to be more than 80 times more resistant to erosion than sand-based deposits (which the engineering models are based on!) And this can all happen with amazing speed. Dredging such deposits will generate the need for ever-greater amounts of dredging, and every cut of the dredger will need careful planning, because it will create areas of high-energy flow, which may well pick up sediments from areas best left settled.

    That is just one of the arguments I laid out in my report. Another would be to question how come a company who proposed one of the barrages, and who have been working to get a structure built for some considerable time, and who had other companies within their group submitting evidence to the come they were allocated the job of assessing whether or not the project should go ahead? Somebody needs to be asking uncomfortable questions of both the BERR, and of Parsons-Brinckerhoff.

    The concept is based on misinformation and in some cases, blind stupidity. I wholeheartedly welcome your opposition to it. As a footnote, I would also like to say that the only proposal which really did seem to put environmental concerns at it’s core, was that of the Tidal Reef. Mr Armstrong Evans, you have my respect for that. However, I still remain to be convinced that even this proposal will not lead to widespread problems of siltation.

  6. Since this article was posted a consortium of 12 environmental groups collectively endorsed the principal of an environmentally friendly reef type structure, so naturally the Government wanted a ‘big company’ consortium to pust it forward, so no prises for guessing what they have done!


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