[tomtom]

Why are barrages necessary for tidal power? I don't get why it's not possible to build just a few underwater turbines with foundations on a few piles in the sea bed without the need to totally enclose a body of water. Surely any moving water will generate more power than moving air?

Ahem... as I said earlier....
Lots of issues to get around. such as bloody harsh environment, sometimes a need to move up and down with the tide to keep in the fastest flowing area, need to work over a range of velocities (during the tidal cycle), need to work in both directions (tide in, tide out etc..). Like wind energy there is also an economy of scale (larger leads to greater efficiency) but of course you only have so much depth of tidal flow...

And to add to that.. in many estuarine and marine environments (e.g. Severn, Humber - and places like Menai straights) the bed is mobile - ie its silt and sand, so moves about throughout the year as well as over longer time scales. This means that your impeller/turbine can be swamped by a sand bar (for example) or the fastest area of flow could move to the other side of the estuary - where your turbine is not...

[andy_e]

How's that turbine in the mouth of Strangford Lough doing?

[SA Chris]

Lots of issues to get around. such as bloody harsh environment, sometimes a need to move up and down with the tide to keep in the fastest flowing area, need to work over a range of velocities (during the tidal cycle), need to work in both directions (tide in, tide out etc..). Like wind energy there is also an economy of scale (larger leads to greater efficiency) but of course you only have so much depth of tidal flow...

And to add to that.. in many estuarine and marine environments (e.g. Severn, Humber - and places like Menai straights) the bed is mobile - ie its silt and sand, so moves about throughout the year as well as over longer time scales. This means that your impeller/turbine can be swamped by a sand bar (for example) or the fastest area of flow could move to the other side of the estuary - where your turbine is not...

Yup, all of which would be issues if it was a barrage (except maybe last). And all of which are issues which are dealt with by offshore O&G industry and other industries (like harbours) on a daily basis.

I'm sure there are problems, I'm just saying that surely tidal doesn't have to equate to barrage ?

[i.munro]

Personally I am strongly in favour of nuclear to fill the gap between weaning ourselves off fossil fuels and getting tidal/ solar/ fusion/ etc up to the required scale.

Bear in mind that a promising wave power program was cancelled in the 70s because the govt of the day 'lied' (they claim a convenient mistake) about the cost of nuclear . What's stopping development of RE is lack of govt funding & the only way nuclear is going to get built is by throwing huge amounts of govt money at it.

We need to solve this (in reality ten years ago) & nuclear has always proved expensive & slow to construct.

[tomtom]

Barrage is actually much simpler. Just thick sea wall enclosing a body of water. You then make a couple of holes in the wall and whack your turbines etc.. in there.. Folk have been doing the like for 100's of years. Sure, its loads more concrete, but much simpler and you don't have to worry about many of the challenges I outlined earlier..

The forces are also pretty high, with tidal flows going up to 3-4 m/s which means you have to have pretty strong anchors/foundations/piling etc.. The problem as I see it is that to generate enough electricity you would need (say across a tidal bay/estuary) 10-20 spread out across it instead of one big one... this makes your infrastructure, cabling, piling blah blah blah that much more expensive..

The tidal 'potential' in the UK is huge - but what is economically usable (once you factor in the engineering) is less huge...

Sorry if I'm sounding a bit down on it - like I said at work we've seen quite a few come and go - and go bust... There are also the tidal power devices that need electricity to generate electricity thats another chestnut...

[Johnny Brown]

the only way nuclear is going to get built is by throwing huge amounts of govt money at it.

We need to solve this (in reality ten years ago) & nuclear has always proved expensive & slow to construct.

I'm quite happy for the government to throw loads of money at it - I can think of no better cause. Renewables are hugely important but the country as a whole, and industry in particular, will still need a solid bed of carbon neutral generation capacity that is not weather/ season dependent. Nuclear may be slow but it remains the only available option to replace the current bed of coal-burning power stations.

I agree this debate should have been finished ten years ago. I am still in shock at Germany's decision to abandon nuclear. However well their renewables are doing their total power output has gone down, but CO2 production has gone up. All because of scare mongering after Fukushima at which, let's not forget, NO ONE DIED as a result of radiation. (And was caused by a freak natural event. Tsunamis are not a realistic risk to Germany).

[i.munro]

If the cost is comparable & (remember that we have no reliable figures for the cost of nuclear from start to finish as it's never been done) then I'd rather see the money go to a  Desertec style project I mentioned earlier.

Once done the problem is solved permanently & we gain food production capacity rather than losing it.

[tomtom]

A reall good balanced blog post on the global impact of fracking (well worth a read). Interesting how the economics of the different fossil fuels lead to shifting (though not necessarily better) CO2 emissions:

http://www.carbonbrief.org/blog/2013/08/is-shale-gas-good-or-bad-for-climate-change

[Johnny Brown]

If the cost is comparable & (remember that we have no reliable figures for the cost of nuclear from start to finish as it's never been done) then I'd rather see the money go to a  Desertec style project I mentioned earlier.

Once done the problem is solved permanently & we gain food production capacity rather than losing it.

Desertec is a lovely idea but exactly the reason why we need new nuclear asap, to replace the fossil fuel base and bridge the gap to such technologies. PV in the desert might be current tech but storing and moving the power long distance is not, nor have we seen too many models of such international cooperation. I doubt the cost would be 'comparable' either.

[Stubbs]

The government needs to stop looking for private companies to invest and just suck up some more imaginary debt and get some nuclear power plants on line!

[SA Chris]

Desertec is a lovely idea but exactly the reason why we need new nuclear asap, to replace the fossil fuel base and bridge the gap to such technologies. PV in the desert might be current tech but storing and moving the power long distance is not, nor have we seen too many models of such international cooperation. I doubt the cost would be 'comparable' either.

Doesn't have to be moved too far;

http://www.clickgreen.org.uk/news/international-news/121654-dubai-tops-list-as-worlds-top-co2-polluter-from-energy-use.html

[tomtom]

The government needs to stop looking for private companies to invest and just suck up some more imaginary debt and get some nuclear power plants on line!

Yup. Its a bit more pressing than HS2 IMHO...

[outlawed]

the only way nuclear is going to get built is by throwing huge amounts of govt money at it.

We need to solve this (in reality ten years ago) & nuclear has always proved expensive & slow to construct.

I'm quite happy for the government to throw loads of money at it - I can think of no better cause. Renewables are hugely important but the country as a whole, and industry in particular, will still need a solid bed of carbon neutral generation capacity that is not weather/ season dependent. Nuclear may be slow but it remains the only available option to replace the current bed of coal-burning power stations.

I agree this debate should have been finished ten years ago. I am still in shock at Germany's decision to abandon nuclear. However well their renewables are doing their total power output has gone down, but CO2 production has gone up. All because of scare mongering after Fukushima at which, let's not forget, NO ONE DIED as a result of radiation. (And was caused by a freak natural event. Tsunamis are not a realistic risk to Germany).

Tsunamis are a UK risk, archaeological record for bristol channel and Norfolk prove that. When Scotland goes independent and no longer uses Douneray as a nuclear waste timebomb, where will England hide it's nuclear waste? London, Sheffield? We could always sell the toxic crap to third world countries and pretend it doesn't exist.

Nuclear energy has no place in a sane world. Embrace renewables or face extinction

[SA Chris]

Tsunamis are a UK risk, archaeological record for bristol channel and Norfolk prove that.

True; whilst not impossible, they are very highly improbable, and a minimal risk compared to that on the Pacific rim. Just build one at a sheltered spot like Ellesmere Port or Grangemouth it can only improve the look of these places.

[outlawed]

Tsunamis are a UK risk, archaeological record for bristol channel and Norfolk prove that.

True; whilst not impossible, they are very highly improbable, and a minimal risk compared to that on the Pacific rim. Just build one at a sheltered spot like Ellesmere Port or Grangemouth it can only improve the look of these places.

they do happen. That's a fact. The precautionary principle should govern judgement. UK has freak tsunamis every now and then due to plate tectonics.

So you're happy to have a nuclear plant in your garden and bury the waste under your house? If not dont wish it on anyone else.

No radiation deaths due to Fukushima? You gotta be kidding?  http://m.huffpost.com/us/entry/1790423

[jakes]

Some interesting comments on this thread. As usual with UKB there are a load of "good" evidence based points where people have researched a bit around the topic. However statements such as the following are misleading and do not give a correct picture of the environmental impact of different energy options.

I think severn barage and other tidal 'mills' should go ahead. Compare their minimal habitat loss to Chernobyl, 3 mile island, Fukushima, Windscale Irish Sea pollution etc.

Because of Hinckley Point and Oldbury nuclear power stations academic papers advise against eating resident fish such as flounder, because of toxic levels of mercury and cadmium in Bristol channel.

Are you really saying that Chernobyl, 3 mile island, Fukushima and Windscale Irish Sea pollution have caused more habitat loss than a potential Severn Barrage? If you truly mean this (and I have understood you correctly)  then you are clearly mis-informed. What habitat loss has been caused by the afore-mentioned nuclear accidents??? Yes, they resulted in the release of radioactive contamination into the environment. However this has NOT resulted in any substantial long term habitat loss.

The largest "habitat loss" in any of these cases is probably at Chernobyl, where the enforcement of the 30 km exclusion zone has removed people from this area. Only a very small number of species that commonly co-exist with humans have been effected, e.g. there has been a reduction in the abundance of barn swallows. The vast majority of species have benefited from the abandonment of contaminated land. If you have access to an academic library see the following as a starting point:  Pikulik, M. M. & Plenin, A. E. 1994 Dynamics of the biological diversity of fauna of Belarus after the Chernobyl nuclear disaster. Radiation Biol. Ecol. Special Issue, 33–34

Anyway I digress. It is good to see a debate surrounding the wider energy mix, than just "no fracking". At the end of the day we need to get our energy from somewhere. The difficulty is deciding which environmental impact is the most acceptable: habitat loss from tidal barrages, potential environmental contamination and long term waste storage issues with nuclear power or carbon releases from fossil fuels.

These impacts needs to be weighed up against one another. There is no such thing as energy without an environmental impact. It just depends what you think the most acceptable impact is...

[i.munro]

Desertec is a lovely idea but exactly the reason why we need new nuclear asap, to replace the fossil fuel base and bridge the gap to such technologies. PV in the desert might be current tech but storing and moving the power long distance is not, nor have we seen too many models of such international cooperation. I doubt the cost would be 'comparable' either.

It's thermal not PV so really old tech (in concept) & no need for storage. The infrastructure for moving it is , as you say, the expensive bit but I can see no reason it can't be as accurately costed as any big infrastructure project ( I doubt that can be said of nuclear)

[SA Chris]

Tsunamis are a UK risk, archaeological record for bristol channel and Norfolk prove that.

True; whilst not impossible, they are very highly improbable, and a minimal risk compared to that on the Pacific rim. Just build one at a sheltered spot like Ellesmere Port or Grangemouth it can only improve the look of these places.

they do happen. That's a fact. The precautionary principle should govern judgement. UK has freak tsunamis every now and then due to plate tectonics.

So you're happy to have a nuclear plant in your garden and bury the waste under your house? If not dont wish it on anyone else.

I thought the recorded ones were believed to be due to massive landslides on the Canaries (somewhere) and Norway? Given that arecheological records and supposition are the only knowledge about them, shows the remoteness of the risk.

And just because I'm saying your concerns regarding tsunamis are poorly grounded doesn't mean all of a sudden I want waste buried under my house, or indeed anyone's. Stop making suppositions.

[tomtom]

Outlawed - I like your passion for the debate..

But Tsunami risk in the UK is tiny - and those that historically have struck were small (1-2m) - their impact was probably much greater as there were effectively no coastal flood defences in that time.. Most of the East coast is protected against surge tide heights, so it would be unlucky for the very rare tsunami to hit at the same time as a king tide... (I'm not sure how you'd get one from the east coast..). Chris - the Canaries mega tsunami theories have recently been debunked my Tusnami/Landslide/Volcanologist colleague tells me (there were mega landslides, but earlier studies cocked up the tsunami estimation)..

I used to set my first year tutees (I'm an academic if you hadn't guessed) a 'get them warmed up' type essay on 'compare the impact of nuclear vs coal power on humans'. If you do a straight body count - then surprisingly (to them usually) you find that a few dozen people have died immediately after nuclear incidents (direct result) and c.5-50 000 total (make up your own numbers really in this range - that seems to be what the journal articles do) from shortened life expectancy from the accidents (mainly Chernobyll). When you look at coal - there are hundreds to low thousands of people every year who die in the extraction process (mining incidents etc..) - and several thousand to 10 thousand (per year) who have die prematurely due to the pollution of burning the stuff..

Its easily if not more 10:1 Coal to Nuclear in the body count... thats before you start factoring in any global warming effects which will start to come in at some point..

I appreciate the jist of this thread debate is more towards RE vs Fracking/Fossil fuels - but I think we need to consider that Nuclear power is possibly the lesser of several evils.

Put it another way - I've done some work at this place: ranger uranium mine in Australia. Its not an especially big pit (its tiny in the open cast mining scheme of things) but at one point in the early 90's, uranium from this mine was generating 10% of the WORLDS electricity... thats just one small (comparatively) sized hole compared to the huge tracts of the earth being removed for coal open cast mines...

(see edits on tsunamis made a couple of in after the OP)

[outlawed]

Tsunamis are a UK risk, archaeological record for bristol channel and Norfolk prove that.

True; whilst not impossible, they are very highly improbable, and a minimal risk compared to that on the Pacific rim. Just build one at a sheltered spot like Ellesmere Port or Grangemouth it can only improve the look of these places.

they do happen. That's a fact. The precautionary principle should govern judgement. UK has freak tsunamis every now and then due to plate tectonics.

So you're happy to have a nuclear plant in your garden and bury the waste under your house? If not dont wish it on anyone else.

I thought the recorded ones were believed to be due to massive landslides on the Canaries (somewhere) and Norway? Given that arecheological records and supposition are the only knowledge about them, shows the remoteness of the risk.

And just because I'm saying your concerns regarding tsunamis are poorly grounded doesn't mean all of a sudden I want waste buried under my house, or indeed anyone's. Stop making suppositions.

first paragraph. There's no proven known reason for these occasional tsunamis, except that we know they do happen.

Second paragraph. You're right. My bad for being a tad spikey. Accept my apologies

[outlawed]

Outlawed - I like your passion for the debate..

But Tsunami risk in the UK is tiny - and those that historically have struck were small (1-2m) - their impact was probably much greater as there were effectively no coastal flood defences in that time.. Most of the East coast is protected against surge tide heights, so it would be unlucky for the very rare tsunami to hit at the same time as a king tide... (I'm not sure how you'd get one from the east coast..). Chris - the Canaries mega tsunami theories have recently been debunked my Tusnami/Landslide/Volcanologist colleague tells me (there were mega landslides, but earlier studies cocked up the tsunami estimation)..

I used to set my first year tutees (I'm an academic if you hadn't guessed) a 'get them warmed up' type essay on 'compare the impact of nuclear vs coal power on humans'. If you do a straight body count - then surprisingly (to them usually) you find that a few dozen people have died immediately after nuclear incidents (direct result) and c.5-50 000 total (make up your own numbers really in this range - that seems to be what the journal articles do) from shortened life expectancy from the accidents (mainly Chernobyll). When you look at coal - there are hundreds to low thousands of people every year who die in the extraction process (mining incidents etc..) - and several thousand to 10 thousand (per year) who have die prematurely due to the pollution of burning the stuff..

Its easily if not more 10:1 Coal to Nuclear in the body count... thats before you start factoring in any global warming effects which will start to come in at some point..

I appreciate the jist of this thread debate is more towards RE vs Fracking/Fossil fuels - but I think we need to consider that Nuclear power is possibly the lesser of several evils.

Put it another way - I've done some work at this place: ranger uranium mine in Australia. Its not an especially big pit (its tiny in the open cast mining scheme of things) but at one point in the early 90's, uranium from this mine was generating 10% of the WORLDS electricity... thats just one small (comparatively) sized hole compared to the huge tracts of the earth being removed for coal open cast mines...

(see edits on tsunamis made a couple of in after the OP)

but if UK can be RE energy self sufficient, we should challenge nuclear and fossil fuel lobbies. Not just sit back and take their crap? We've sat back long enough, and paid for the privilege of not questioning their hegemony.

[Johnny Brown]

they do happen. That's a fact. The precautionary principle should govern judgement.

If the precautionary principle was used to that level we wouldn't be able to do anything! What if there were a big earthquake in London? It would fall down! By showing you fear a UK Tsunami shows you have no ability to assess risk, and thereby rather undermines your assessment of the risk posed by nuclear.

So you're happy to have a nuclear plant in your garden and bury the waste under your house? If not dont wish it on anyone else.

Well for one, no one is suggesting putting a plant in my garden. If they were to bury it with the kind of schemes mooted, in suitable geology I wouldn't give a toss, no. Far too much emotion and not enough judgement in this debate. Which coming from climbers, whose hobby involves assessing risk, is disappointing.

Secondly though, and far more importantly, if we were to build an IFR, the current waste would be the fuel, and it would be recycled until none were left.

No radiation deaths due to Fukushima? You gotta be kidding?  http://m.huffpost.com/us/entry/1790423

As Tomtom said 'make up your own figures'. The official figure is zero - unlike the figure for coal. Renewables are the long term ideal, but Nuclear is the only hope we have to wean ourselves off fossils fast enough to avoid serious climate change. Renewables alone are not a solution.

[slackline]

Which coming from climbers, whose hobby involves assessing risk, is disappointing.

Very different scales of risk though, skills in one may not be directly transferable to the other.

[SA Chris]

but if UK can be RE energy self sufficient, we should challenge nuclear and fossil fuel lobbies. Not just sit back and take their crap? We've sat back long enough, and paid for the privilege of not questioning their hegemony.

You are 100% on the money. And maybe in the future we may be renewable energy self sufficient, but I think for now it's a case of either fossil or nuclear. Neither is sadly not an option.

Can't deny everyone has to do as much as they feel they can to reduce consumption in the first place though.

[tomtom]

Which coming from climbers, whose hobby involves assessing risk, is disappointing.

Very different scales of risk though, skills in one may not be directly transferable to the other.

Just to chip in, the classic economic formula for calculating risk is

Risk = probability(from 0-1) x cost