Severn barrage

[nickwilliams]

Surely a tidal barrage would not have that drastic effects

It doesn't flood any more land, but it does keep large areas of mud flats under water which denies huge feeding grounds to water fowl.

The big problem is predicted to be that the reduction in flow which would result from keeping the water behind a barrier for significant periods between tides will increase the deposition of silt out of the water. This has the potential to dramatically alter the topology of the mud flats inside the barrier, and over time wil render the scheme ineffective unless a massive dredging and dumping operation is organised.

Nick.

 

[graham]

Surely a tidal barrage would not have that drastic effects

It doesn't flood any more land, but it does keep large areas of mud flats under water which denies huge feeding grounds to water fowl.

The big problem is predicted to be that the reduction in flow which would result from keeping the water behind a barrier for significant periods between tides will increase the deposition of silt out of the water. This has the potential to dramatically alter the topology of the mud flats inside the barrier, and over time wil render the scheme ineffective unless a massive dredging and dumping operation is organised.

Nick.

Correct. Anyone who wishes to see this should simply use Google Earth to take a look at the Severn estuary. This gives a very graphic illustration of just how much silt is carried downstream by the Severn.

 

[dunc]

There will always be agruements for and against such schemes.. But at the end of the day Earth has been screwed-up so much it makes no difference whether or not we have a barrage or nuclear or fossil power generating power for our obsessive needs.. Too little, too late.

Dear old Earth will heat up regardless of such minor schemes, if the effect known as global dimming is true it will heat up even more than has been predicted which means Otter would probably end up entirely sumped anyway, so enjoy it while you can!!

 

[Peter Burgess]

Maybe it's not the Earth that's screwed up, it's the human race. The Earth has been here before, albeit by natural means. I understand that when ocean sea levels have risen in the past, it happened over a matter of mere decades rather than centuries, and yet life adapted and went on. Whether humans could adapt so quickly, I doubt.

This era of periodic cooling and glaciations is a 'recent' phenomenon. Before that, much of the world was semi-tropical was it not?

Totally off topic but, hey, that's life.

 

[dunc]

This era of periodic cooling and glaciations is a 'recent' phenomenon. Before that, much of the world was semi-tropical was it not?

Fluctuations in temperature has occured at various times over many millions of years.. There are theories that suggest ice extended over most of the planet at one or two points over Earths past.
As for tropical, we are still in a cool phase and potentially warming up naturally, although thats probably been greatly enhanced by man!

 

[hoehlenforscher]

Cap n chris said

To produce 20% of UK power by windpower requires 95,000 wind turbines.

There was a energy calculator on the BBC homepage the other day where you could choose how you would produce the future energy needs of this country given a free choice. I choose a 20% reduction in energy consumption through technical means and education coupled with 100% renewables. It said to acheive this output would mean building 9500 new wind turbines (or their equivilant. This is very different to your figure. Now i do not know which one is correct but there is one hell of a difference between the 2....... :shock:

 

[martinr]

....I choose a 20% reduction in energy consumption through technical means and education coupled with 100% renewables. It said to acheive this output would mean building 9500 new wind turbines (or their equivilant. This is very different to your figure. Now i do not know which one is correct but there is one hell of a difference between the 2.......

I've just repeated the calculation using your figures. http://news.bbc.co.uk/1/shared/spl/hi/uk/06/electricity_calc/html/1.stm

It says You'll be building 0 new fossil fuel power stations, 0 new nuclear reactors and 9,255 new wind turbines plus other renewable installations, insulating 28m houses and buying 0% of electricity from overseas. It then adds: ! Electric generated far exceeds projected demand, this is unrealistic! You can now try again.


If you lok at the notes at http://news.bbc.co.uk/1/hi/sci/tech/4721284.stm
it explains that:

Wind turbines
The number of new wind turbines does not exceed 9,255, even if 400bn kWh of electricity is selected on the renewable electricity slider. This is because the calculator is calibrated to switch to alternative renewable power sources once wind power reaches a certain level.

Capn Chris is right when he says To produce 20% of UK power by windpower requires 95,000 wind turbines. It is just that the the BBC model allows only a max of 9255 turbines. After that, you have to add tidal barrages etc to generate the required power from renewable sources.

 

[emgee]

The big problem is predicted to be that the reduction in flow which would result from keeping the water behind a barrier for significant periods between tides will increase the deposition of silt out of the water. This has the potential to dramatically alter the topology of the mud flats inside the barrier, and over time wil render the scheme ineffective unless a massive dredging and dumping operation is organised.

Nick.

Indeed but you should be able to flog the stuff off to farmers. The annual deposit of silt from the Nile has been the foundation of the Egyptian economy for millenia.

Inside the barrier will eventually be fresh water which will of course has it's own impact on what were previously tidal waters.

It might actually improve the water in the entrance to otter hole

 

[Hughie]

The big problem is predicted to be that the reduction in flow which would result from keeping the water behind a barrier for significant periods between tides will increase the deposition of silt out of the water. This has the potential to dramatically alter the topology of the mud flats inside the barrier, and over time wil render the scheme ineffective unless a massive dredging and dumping operation is organised.

Nick.

Indeed but you should be able to flog the stuff off to farmers. The annual deposit of silt from the Nile has been the foundation of the Egyptian economy for millenia.

Inside the barrier will eventually be fresh water which will of course has it's own impact on what were previously tidal waters.

It might actually improve the water in the entrance to otter hole

Nice idea but wont work. Way too much bureaucracy.

 

[hoehlenforscher]

Hi Martin.,

I stand corrected since I did not read the notes! :shock: I just tried to see how many windmills would be needed to produce 100% of our needs using their model. I must admit to being a bit suprised it was such a low figure but on the basis of 95000 windmills for 20% then 9500 windmills would only produce 2% of the countries energy needs. Fair enough so why set up the exercise to then say that we would need no nuclear and no fossil fuel plants..... Makes no sense

trouble with this country is that real power is held by the minority and there is absolutely no politcal will to implement smaller scale local energy production. If its not big then it won't get any backing. We could create a huge amount of the coutries energy needs from small scale local power plants in the community be they biomass, water, solar, wind biofuels etc BUT there will be no big fat profits and no rich shareholders and hence no incentives are offered to get such initiatives off the ground. Indeed planners seem able to actively discourage any such community schemes. There is obviously no easy answers but it must surely begin with energy conservation and using what we now have more efficiently..

 

[emgee]

The big problem is predicted to be that the reduction in flow which would result from keeping the water behind a barrier for significant periods between tides will increase the deposition of silt out of the water. This has the potential to dramatically alter the topology of the mud flats inside the barrier, and over time wil render the scheme ineffective unless a massive dredging and dumping operation is organised.

Nick.

Indeed but you should be able to flog the stuff off to farmers. The annual deposit of silt from the Nile has been the foundation of the Egyptian economy for millenia.

Inside the barrier will eventually be fresh water which will of course has it's own impact on what were previously tidal waters.

It might actually improve the water in the entrance to otter hole

Nice idea but wont work. Way too much bureaucracy.

Just make it illegal to collect the silt and sell it to farmers the black market will take care of the rest.

 

[nickwilliams]

trouble with this country is that real power is held by the minority and there is absolutely no politcal will to implement smaller scale local energy production. If its not big then it won't get any backing. We could create a huge amount of the coutries energy needs from small scale local power plants in the community be they biomass, water, solar, wind biofuels etc BUT there will be no big fat profits and no rich shareholders and hence no incentives are offered to get such initiatives off the ground.

You have a point, but the other side to the same argument is that it is relatively simple for central government to cause the creation of a few large scale plants (be they nuclear or fossil fuel or something else). However, as the power plants get smaller it gets progressively harder for central government to make them happen. If you take your proposal to its logical extreme, and build a plant of some description in every community, you'd have to create a whole new layer of government to both build and run them. In the village I live in, for instance, there is no way the parish council is competent to run any kind of power station even if it was economically viable (which it isn't, no matter how big the tax breaks are). It might work administratively if you go right down to the individual consumer level, but you'd still need a grid and some central generation to compensate for load variations. You'd also have to largely re-wire the country since a grid which relies on lots of small scale local generating capacity rather than a relatively small number of vary large plants needs to be designed in a very different way to what we have at present. And, finally, you have to face the fact that if you are going to use any fossil fuels at all, it is actually far more efficient in terms of energy conversion and greenhouse gas emissions to run fewer bigger power stations than lots of small ones.

I have some sympathy with central government's predicament on this issue. It's very easy for everyone not in power, and who doesn't have to take any real responsibility for the problem (and can conveniently ignore the very real technical and financial challenges) to say "do this, do that" but it's actually a very complex problem to balance the needs of all the different users, and make sure that the lights stay on 100% of the time. There's a very big difference between an approach which might provide most of the energy we need and one which guarantees to provide all of it, and the government can only be in the business of providing the latter.

If I have a criticism of goverment, it is that it's absolutely appalling that it's taken them 20 years to realise they need think about the problem on a 50 year timescale and not leave it to short term market forces. Anyone with an ounce of foresight could have told them 20 years ago that we needed to be thinking about what happens when gas becomes too expensive to waste on electricity generation. One of the responsibilities of government is to identify challenges like this and deal with them before they become a crisis, but governments of all flavours in the last 50 years have been too focussed on their ideology and not enough on the boring but necessary job of actually making sure the country continues to function.

Enough!

Nick.

 

[martinr]

....I stand corrected since I did not read the notes! ..

Hi hoehlenforscher

It took me ages to work out why, whatever options you choose, the BBC calculator has a max of 9255 wind turbines. I had to search for the answer. There must be thousands of people who think this number of wind turbines can solve all our problems.

I live on Morecambe Bay. There is a railway viaduct not more than 100 yards from where I live. Upstream of the viaduct is the port of Milnthorpe. Except, it is no longer a port. When the viaduct was constructed in the 1800's, some of the tidal energy was lost as friction against the columns of the viaduct. As a result, the incoming tide is slowed down. On spring tides, the incoming tide at the viaduct can be 2 metres higher than the river upstream of the viaduct. Consequently, the scouring action of the tide on the bed of the estuary was reduced and the river silted up so that ships (or more likely, barges) could no longer reach Milnthorpe, which is about 3 miles upsteam of the viaduct.

This is the problem with barrages - they extract energy from the sysyem with unforseen consequences. Much bettter to build tidal lagoons. These can fill and empty with each tide, yet allow the tide to contiue up the estuary leaving ecosystems relatively undisturrbed.

 

[martinr]

...Anyone with an ounce of foresight could have told them 20 years ago that we needed to be thinking about what happens when gas becomes too expensive to waste on electricity generation.

As I recall, government policy 20 years ago was that North Sea Gas should not be used to generate electricty. Mrs Thatchers government then changed the rules to allow our gas to be wasted in this way. She went for the short term fix of allowing gas powered electicity generation as part of her opposition to the power of the miners and Trades Unions.

 

[graham]

Enough!

Nick.

Nah, this thread hasn't generated anywhere near enough of anything yet.

 

[cap n chris]

And there was me thinking that governments only tend to work on a 4-5 year basis; i.e. tell the electorate what they want to hear so they don't vote the other buggers in!

 

[hoehlenforscher]

http://news.bbc.co.uk/1/hi/scotland/glasgow_and_west/4951236.stm

now if 140 windmills can generate enough for 200000 homes and assuming a home houses an average of 3 people and a population of 60 million then a bit of simple maths says that 21000 windmills would do the job. Obviously this does not accoutn for inductrial use and there needs to be ways to generate electric when there is no wind and or peak demand. BUT again the figure of 95000 windmills only able to provide 20% of our needs seems exagerated. Something doesn't add up (and it is more than likely BBC reporting if I know anything about it!)

Hey Nick

why stop the debate now its getting interesting.

 

[martinr]

http://news.bbc.co.uk/1/hi/scotland/glasgow_and_west/4951236.stm

now if 140 windmills can generate enough for 200000 homes.....

Scottish Power said its £300m Whitelee project .... will generate 322 megawatts of electricity - enough to power nearly every house in Glasgow. But that is peak output. It wont generate 322 megawatts continuously. So it will only generate enough to power nearly every house in Glasgow some of the time. Trouble is, Glasgow wants elec all of the time so will need traditional power stations on permanent standby to generate the shortfall

 

[graham]

http://news.bbc.co.uk/1/hi/scotland/glasgow_and_west/4951236.stm

now if 140 windmills can generate enough for 200000 homes.....

Scottish Power said its £300m Whitelee project .... will generate 322 megawatts of electricity - enough to power nearly every house in Glasgow. But that is peak output. It wont generate 322 megawatts continuously. So it will only generate enough to power nearly every house in Glasgow some of the time. Trouble is, Glasgow wants elec all of the time so will need traditional power stations on permanent standby to generate the shortfall

Are you sure that was a peak & not an average figure?

 

[nickwilliams]

Hey Nick

why stop the debate now its getting interesting.

Sorry, that wasn't quite what I meant. I'd spent about 45 minutes drafting my message when I should have been doing something else, so I meant to say that was enough from me for now, not that it was enough on the topic as a whole!

For those who are interested in some of the technicalities of this discussion, there's an interesting discussion on the efficiency of fossil fuel fired power stations running on another bulletin board I frequent at http://www.practicalmachinist.com/ubb/ultimatebb.php/topic/15/591.html. It's very 'Merkin-centric and the signal to noise ratio is fairly low, but there's some interesting stuff from people who really know about fossil fuel and hydro power design in there if you dig deep enough.

I'd be delighted to see the debate continue on ukcaving.com but it would be nice to see some input from people with some direct hands-on experience of the technical challenges rather than the fairly airy-fairy assertions we've seen so far. I've not done a lot of power generation and distribution related work, but I have done some and I do know enough about it to understand that the technical challenges of keeping the lights on for the next 50 years are not trivial. There is an awful lot of wishful thinking goes on by people who don't ever have to back up the noise they make by real action and I'm afraid I have little time for the people who can't face the reality of the fact that renewables are not going to provide the whole answer to the problem in our lifetimes no matter how much we might all wish it were so.

Getting back to the discussion in hand, there was a discussion on the Severn Barrage on R4 'You and Yours' today. Y+Y is not a program I have a great deal of time for (in depth and technical it ain't!), but the interesting fact was there was a spokesman from the Welsh Assembly and it's clear that the Cap'n's assertion that this is just something dreamed up by one pissed off individual to spite the planners is very far from the case. Personally I doubt there will be a Severn Barrage in my lifetime, mainly because there ain't enough money in the system to pay for it (think channel tunnel), but there's sure going to be some arguments about it.

Probably more relevant to this particular forum is the potential for the increase in the use of coal for power generation, which I would have said is pretty much a certainty. At the moment, something like 2500 tons of Peak District limestone is used every day at Drax alone for flue gas de-sulphurisation. If the amount of coal burned at power stations around the country goes up then the amount of limestone needed for FGD will also increase, and that means more of cavers' favourite landscapes being quarried away to provide it. How long before the country's energy demands means that quarries which we thought were dead for ever (Fairy Cave? Eldon Hill?) get opened up again?

Nick.