/ Severn Barrage

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Rob Exile Ward on 10 Jun 2013
Call me stupid, but this seems a pretty good idea to me. 5% of UK's energy requirement for just 25 billion? A snip.
tony on 10 Jun 2013
In reply to Rob Exile Ward:

It's not 5% of the UK's energy - it's 5% of the UK's electricity. There's a big difference.

And is it the best way to spend 25bn on electricity? What could be done by spending that much money on more efficient use of the generation we have. Might we be better off with 25bn spend on CHP, or micro-generation, or lots of alternatives?

I don't know the answers, but the bald statement that the barrage could produce 5% for 25bn doesn't really cover a very wide range of complex issues.
teflonpete - on 10 Jun 2013
In reply to tony:

Only produces it at certain times of the day too (outgoing tide). Without other barrages which can provide supply at different tide phases, Solway Firth or the Mersey for instance, the Severn Barrage would still need to be backed up by conventional supply during the incoming tide. That said, the advantage for tidal power over wind or wave generated electricity is that it is predictable.

Agree with you re efficiency measures and reducing consumption, although that would have to be done in such a way as to prevent a possible rebound effect.
Rob Exile Ward on 10 Jun 2013
In reply to teflonpete: I though the point was that it could produce electricity on both phases of the tide? After all, once the water has come in - generating power - then it has to go back out again, surely it has the same potential in both directions?
tony on 10 Jun 2013
In reply to teflonpete:
> (In reply to tony)
>
> Only produces it at certain times of the day too (outgoing tide).

Are you sure about that? Why wouldn't it work on the incoming tide as well? According to the company website, it can deliver a bit over 15 hours per day although that 15 hours does vary with the tides, so there would be times when it's generating when demand is low.
Red Rover - on 10 Jun 2013
With a few more pumped storage things like Dinorwic it wouldnt matter that it didnt produce power constantly.
RCC - on 10 Jun 2013
In reply to tony:

> Are you sure about that? Why wouldn't it work on the incoming tide as well? According to the company website, it can deliver a bit over 15 hours per day although that 15 hours does vary with the tides, so there would be times when it's generating when demand is low.

Even then, there would be 4 peaks per day, with very little power generation in the hours around high and low water. There would also be variation due to the spring/neap cycle. Perhaps this variation is not important if there is suitable long distance distribution?
Rob Exile Ward on 10 Jun 2013
In reply to tony: I suppose I'm intrigued that MPs can dismiss what is admittedly a major infrastructure scheme that has the potential to make a major contribution to renewables and give a major boost to S Wales economy, quite so quickly.

Not many Tory votes in S Wales though, are there? And it's a bit out in the sticks.
jkarran - on 10 Jun 2013
In reply to Red Rover:

> With a few more pumped storage things like Dinorwic it wouldnt matter that it didnt produce power constantly.

You're right, many of these renewables work best in combination with other technologies, it's one of the things that makes them an easy target for critics. Conveniently the uk has a coastline that could be used to provide '3 phase' tidal power smoothing out the tidal supply ripple almost completely but it's obviously a *much* bigger project.

jk
jkarran - on 10 Jun 2013
In reply to RCC:

The variation's not important from a technical perspective if it's predictable and a relatively small fraction of the total supply which it is and it is. Dealing with the economics of it all looks a bit more challenging.
jk
teflonpete - on 10 Jun 2013
In reply to Rob Exile Ward:

You don't get as much generation overall with a 2 way system as the barrage limits the water inflow to the estuary so high tide doesn't get as high as it would without the barrage.

It's not a new idea, tidal generation using a Severn Barrage was studied in quite some depth in the '80s and it isn't without considerable environmental penalties.

http://en.wikipedia.org/wiki/Severn_Barrage#Bondi_Committee_.E2.80.93_1981
RCC - on 10 Jun 2013
In reply to jkarran:
> Conveniently the uk has a coastline that could be used to provide '3 phase' tidal power smoothing out the tidal supply ripple almost completely but it's obviously a *much* bigger project.


Would it not be (proportionally) far more expensive to build similar generating capacity at other points around the UK? As I understood it, the tidal range and area of the Severn estuary makes it something of a special case (in the UK at least).
teflonpete - on 10 Jun 2013
In reply to RCC:
> (In reply to jkarran)
> [...]
>
>
> Would it not be (proportionally) far more expensive to build similar generating capacity at other points around the UK? As I understood it, the tidal range and area of the Severn estuary makes it something of a special case (in the UK at least).

The Severn estuary is the main one as it gets the full tidal surge off the Atlantic and the biggest height differences between high and low tides. As I said above, Solway Firth in Scotland and the Mersey estuary on the west coast are also viable sites, as is The Wash on the East coast. Those other sites have less technical potential and far less economic potential than the Severn though.
jkarran - on 10 Jun 2013
In reply to RCC:

> Would it not be (proportionally) far more expensive to build similar generating capacity at other points around the UK? As I understood it, the tidal range and area of the Severn estuary makes it something of a special case (in the UK at least).

In a word, yes.

The Severn estuary is well suited to a barrage as are a few smaller locations around the coast but it may be better to look at tidal flow devices in pinch-points elsewhere. I suspect in the medium term they (and the barrage) will meet with insurmountable opposition from a broad range of pressure groups.

jk
gethin_allen on 10 Jun 2013
In reply to Rob Exile Ward:
It's the environmental impact that worries me, that is to say that I don't really know what impact it will have as nobody entirely impartial has put anything into wide circulation.
Anyone on here able to shed some light on this?
ring ouzel on 10 Jun 2013
In reply to gethin_allen: No as I am not impartial. I did my MSc on tidal power stations and I looked at the environmental damage it would cause. Thousands of birds would die as their wintering areas would be under water. It would also cause immense disruption to fish and invertebrates. I went from knowing nothing about them to being very anti.
Gentleman Antiquarian - on 10 Jun 2013
The La Rance tidal barrage on the northern coast of Brittany has had a massive environmental impact with silting causing the destruction of the formerly massive local oyster trade and a rising saline water table inland.

The opponents of the previous Severn Barrage proposal brought two hydro-engineers over from the Dutch State Hydro Board to categorically state that barrages are a bad thing. The construction of the Markerwaarddijk in 1975 across the IJsselmeer has led to the accumulation of massive amounts of pollutants in the sediments of the Markermeer and it is costing the Dutch Govt billions to clear the mess up.

The Severn may be a very dynamic river and estuary but its hydrography and current patterns are poorly understood. It is also fringed by massive industrial developments such as Avonmouth cheek-by-jowl with wetlands of world importance such as Slimbridge and Goldcliffe.

Instead to consuming more energy and emitting more carbon in pursuit of more "green" power, why don't we just save energy or is that too obvious?
Neil Williams - on 10 Jun 2013
In reply to Gentleman Antiquarian:

In practice we are doing, e.g. by using energy saving light bulbs rather than tungsten etc, and by modern devices being more energy efficient.

But some nuclear power stations are being decommissioned, and something has to replace them. Personally I think that should be more nuclear power stations, but I suspect I'm in the minority.

Neil
EeeByGum - on 10 Jun 2013
In reply to Rob Exile Ward:
> (In reply to tony) I suppose I'm intrigued that MPs can dismiss what is admittedly a major infrastructure scheme that has the potential to make a major contribution to renewables and give a major boost to S Wales economy, quite so quickly.

I agree with your sentiment but this is hardly a new idea and I would imagine that its dismissal is more political than practical. The coalition is currently pretty weak, especially with the current lobbyist scandal starting to build momentum. The Severn Barrage project has the potential to stir deep seated emotions on both sides of the debate and would certainly bog down any government that proposed the idea as viable.
teflonpete - on 10 Jun 2013
In reply to ring ouzel: My understanding of barrages is far more limited than yours having only studied them briefly as a second year undergrad, but from what I remember other arguments against barrages included siltation and hydrogen sulphide gas emissions caused by the stagnation of water on the upstream side of the barrage.

The tidal flow systems that JK mentioned above seem to be a far better option for the Severn Estuary environmentally.
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Simon4 - on 10 Jun 2013
In reply to EeeByGum:

> I agree with your sentiment but this is hardly a new idea and I would imagine that its dismissal is more political than practical.

There will always be a substantial political component to such a decision, but as outlined above in the wikipedia description of previous studies, apart from informed comments by people like Ring-Ouzel, there are very substantial practical problems. It may just not be as good a scheme as it first sounds like.

> The coalition is currently pretty weak, especially with the current lobbyist scandal starting to build momentum

There opponents are even weaker however, while lobbying seems like standard Westminster village froth.

> The Severn Barrage project has the potential to stir deep seated emotions on both sides of the debate and would certainly bog down any government that proposed the idea as viable.

Similar to HS2, most people are in favour and it sounds like a magic bullet, until the costs and details become more apparent. But any major infrastructure project in a country as crowded as the UK is going to arouse masses of passionate objection, that does not mean we can forever put them off.

Rob Exile Ward on 10 Jun 2013
In reply to ring ouzel: I do understand that there are environmental considerations, but I'd like to make a few of points. 1) How easy is it assess the environmental impact of such schemes - you can never have exact examples to work from, every case must be unique. 2) Environmentalists have a habit of overstating their case - wasn't Cardiff Bay supposed to become an environmental disaster? As a lay person, it doesn't look that way to me. 3) Even if these schemes go ahead, they don't destroy environments - they change them, with new ecological niches, environments and all the rest - just like what happens in nature. Yes some habitats might be compromised, but others might well be created. Stasis is not an option long term, whether change is created by us or by nature.
EeeByGum - on 10 Jun 2013
In reply to Simon4:
>
> There opponents are even weaker however, while lobbying seems like standard Westminster village froth.

True, but they are very vocal and more than likely to use unorthodox methods to get their point across. I guarantee that this debate will rumble on forever whilst never being built.
ring ouzel on 10 Jun 2013
In reply to teflonpete: Oh I'm no expert Pete! Yes there are problems as the longer you increase the through time for particulates the more particulates will fall out of the water column. These particulates may be silt or they may be sewage. They will accumulate and that does cause problems, except where the water flows through the turbines themselves when you can get scouring of the sea bed on the downstream side. Thats not really my area though. Black tailed godwits on the other hand I can talk to you about!
ring ouzel on 10 Jun 2013
In reply to Rob Exile Ward: No it's not easy Rob as we have little to compare it against. The Severn has the second largest tidal range in the world which makes it difficult to predict with any certainty how it will affect all the various habitat types. The reason we hyper ventilate about these things is we see how much is lost and the overall effect this is having on things like birds. We dont know everything about birds by any means but what we do know shows they are in trouble and because the birds involved are long distance travellers they are not just UK birds, they also 'belong' to countries all the way from South Africa to Russia. If we then look at other groups such as fish and invertebrates where our knowledge is patchy at best we can only guess what will happen. If the scheme goes ahead it will destroy certain habitats. Things like periodically flooded mudfalts will disappear. Other things such as saltmarsh will change but I dont know by how much. I totally agree stasis is not an option but in the past the changes have tended to be slower than what we are proposing and also there was less development so losing or radically altering a habitat means that often there is nowhere left to mop up the displaced animals and they will simply die off. And we could try to recreate mudflats but it is time consuming and requires space and would need to be started decades before any construction work.

I am firmly behind thorium nuclear as the best of a bad bunch.
EeeByGum - on 10 Jun 2013
In reply to ring ouzel: But then I suppose if we do nothing, the chances are that all that habitat will be lost to global warming anyway. At least that theory is based on as much fact as predictions about lost habitat should the barrier be built.
Lord of Starkness - on 10 Jun 2013
In reply to Rob Exile Ward:

Some interesting reading here -- http://www.foe.co.uk/resource/briefings/severn_barrage_lagoons.pdf

As an engineer I find it an interesting concept, that seems to address a lot of the environmental concerns over silting caused by a tidal barrage on a river estuary or the likes of Morecambe Bay or the Solway.
Sarah G on 10 Jun 2013
This one was never going to fly. We were chewing over the possibillity over 25 years ago, and the inherent (and very expensive) issues haven't gone away- namely the high cost of the set up and maintenance, saltw*ter corrosion (and therefore ?longevity), interfering with the navigation of the area, and environmental impacts.

Sx
Trangia - on 10 Jun 2013
In reply to teflonpete:
> (In reply to RCC)
> [...]
>
> The Severn estuary is the main one as it gets the full tidal surge off the Atlantic and the biggest height differences between high and low tides. As I said above, Solway Firth in Scotland and the Mersey estuary on the west coast are also viable sites, as is The Wash on the East coast. Those other sites have less technical potential and far less economic potential than the Severn though.

What about the Thames? And IIRC the Solent which has 4 tides a day?

RCC - on 10 Jun 2013
In reply to Trangia:

> What about the Thames? And IIRC the Solent which has 4 tides a day?


The Solent doesn't have 4 tides a day, it has a double high tide (which is slightly different).

One of the reasons that the Severn has such a large tidal range is that it is a long way from the north Atlantic amphidrome. The same is not true in on the east coast, as there are a number of amphidromic systems in the north sea.
EeeByGum - on 10 Jun 2013
In reply to Trangia:

> And IIRC the Solent which has 4 tides a day?

Indeed - but that would mess with Cowes week so that is dead in the water before it even starts! :-)
wintertree - on 10 Jun 2013
In reply to Red Rover:
> With a few more pumped storage things like Dinorwic it wouldnt matter that it didnt produce power constantly.

Wrong answer. Dinrowic can buffer something like 30sec of power.

There aren't enough sites in the UK to make it workable, and if there were, converting them to pumped storage would be an environmental disaster eclipsed only by the Severn Barrage.
Red Rover - on 10 Jun 2013
In reply to wintertree: But if Dinorwic can't provide power for long, can't it absorb the extra power, caused by the tide going out of the severn barage when power isnt needed, for a lot longer?
jkarran - on 10 Jun 2013
In reply to wintertree:

> Wrong answer. Dinrowic can buffer something like 30sec of power.

Draining Dinorwic in 30 seconds would be pretty exciting*. From full, running at peak output of 1.8GW it has around 5hrs of energy stored. Whether they can keep it cool for 5hrs flat out...

*read utterly devastating and thankfully impossible

> There aren't enough sites in the UK to make it workable, and if there were, converting them to pumped storage would be an environmental disaster eclipsed only by the Severn Barrage.

There are 100s of sites in the uk that are physically suitable for pumped storage. You're right, there's an environmental cost associated with their development but then that's true of doing nothing as well.

jk
tony on 10 Jun 2013
In reply to wintertree:
> (In reply to Red Rover)
> [...]
>
> Wrong answer. Dinrowic can buffer something like 30sec of power.

Are you sure about that?
JJL - on 10 Jun 2013
In reply to ring ouzel:

> I am firmly behind thorium nuclear as the best of a bad bunch.

Curious about this. Don't you end up with Radon as a by-product? Although non-fertile is better, a gas is inconvenient...

Agree about the requirement for nuclear though.
wintertree - on 10 Jun 2013
In reply to tony:
> (In reply to wintertree)
> [...]
>
> Are you sure about that?

Apparently not. It was the figure I had in my head, it seems 30sec is more like the startup time from cold. Perhaps also it's the duration of the kettle induced spikes it often smoothed out and the end of corrie/Eastenders.

.

In reply to Rob Exile Ward: They have electricity in Wales? :-0

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