Yes folks, its cheaper to heat with electricity!

[dennis]

That was on a reactor that only generated stuff for weapons too. Not really constructed with safety in mind.

[Andrew Gabriel]

That's what we've been doing for the last 25 years. The English mis-trust of nuclear means we've been paying the French to build them for us along their north coast and ship the power over.

[dennis]

Say 1.5km sq so 2,250,000 m2 Say 3m tide, so average of 6,750,000 m3 About 6,750,000,000,000 kg lift(fall) through 1.5m average. About 10,125,000,000,000 Joules of energy. About 10GJ. So that is 10Gwatts for one second or about 2MW for an hour. Not worth doing for 1 square mile.

Note: assuming 100% efficiency.

[The Natural Philosopher]

Assume a square mile of water that goes up and down 10 meters at every tide.

1600 x 1600 x 10 meters is the volume in cubic meters, hence the weight in tonnes

the drop is ten metres, so its 1600x1600x10x10x1000 joules. Or watt seconds

So divide by 12x3600 to get the power in watts.

I make that 6Gw at 100% efficiency.

So we either have more tidal range than that, more than square mile, or more than 100% efficiency, or someone is lying.

MM. a quick google nets a tidal range of 15meters, so 12Gw at 100% efficiency at peak tides for a square mile.

I very much doubt that much better that 50% efficiency is possible with such low drops or that a 15 meter tide is the average..its the peak.

Or that consstruction costs are sane..

Event at 6GW, its still less than 2% of total energy needed, and the Severn is the only place where such a tidal flow is realisable, so it is really 'completeley change the landscape of the severn estuary at unknown cost, and knock out two out of a 100 nuclear powers stations needed'

[Roger]

The message from "dennis@home" contains these words:

I am sure the promoters of the scheme would not risk £billions without being sure of their figures.

FWIW you don't seem to have any idea of the scale of the project. The footprint quoted is for the barrage and roadway. The enclosed water (somewhere in the region of 200 square miles) is not part of the footprint as the high water mark remains much the same. The barrage differs from a conventional dam in that it doesn't flood any previously dry ground. What it may do is reduce the effectiveness of the Severn Bore and make the coastline within it less at risk from flooding during extreme tide events.

That just might work for London. A barrage across the mouth of the Thames would not generate enough power to be a viable proposition as a generator but as a flood defence it might be the only thing that would protect London in the medium term, and the generation would then be an added bonus. (Oh yes and sod the bloody wildlife:-)).

Little problem with a sunk shipload of unstable HE to deal with first but that needs to be dealt with some time soon anyway.

[The Natural Philosopher]

That is pure weasel.

200 square miles of tidal estuary vanish, to become essentially non tidal.

And thats the same impact as a nuclear power station?

The barrage

The coastline depends on flooding during extreme tidal events to make it what it is.

London needs about 35Gw to run. You wont get that from a Thames barrier.

All this stuff is technically interesting, but doesn't really dent the overall power needs of the UK.

Its a distraction, not a solution.

We need mass produced power stations that can generate somehow the 350GW of energy we need to run the place, that currently is met by burning hydrocarbons and carbon.

There is only one faintly viable place for a tidal scheme, or maybe two, and both would utterly destroy unique habitats.

To what end? they can't supply more than a tiny fraction of the countries needs.

Why bother?

[The Natural Philosopher]

Not very much sadly.

2GW only.

[tony sayer]

Well I'm sure they can parall a few up;)..

[AJH]

NP>> I confused Calder hall with windscale.

I think the site that housed both was called windscale at that time

Actually unlikely, you didn't pay attention to what I said in my post, the reaction was between the uranium that ruptured from the sheathed fuel rods and the air. The initial overheat came for spontaneous release of energy stored in deformation/dislocation of the graphite lattice. Graphite didn't burn in the conventional sense and indeed doesn't easily except in pure oxygen below 1300C and the pile didn't get above 1300.

It looks like it was a simple air cooled pile rather than a contained reactor as used in a power station.

Still apart from being an interesting chat between lay people this doesn't have much to do with diy!

AJH

[AJH]

Did you buy shares in Chunnel? ;-)

AJH

[AJH]

It's only the top bit that goes up and down 10 metres! in this hypothetical case isn't the average fall just 5?

AJH

[Dave Liquorice]

Eh 35GW? Current national demand is ony 44.278GW...

Ah I think you need to clarify, you are talking total energy demand not just electricity. So including the energy consumed in the form of petrol and diesel for transport, gas and oil for heating etc.

[Doctor Drivel]

Maxie, I'm amazed - especially as you are a fabulist too. Coming from the mouth of a man who starts the conga line in Butlins and is even in a Paddy band too, I am shocked.

[The Natural Philosopher]

Oh yes they would. Its known as 'Channel Tunnel Vision' :-) There are MANY unknowns in a one off project of this size and scale. There are huge uncertainties in what the ground will be like, so how big foundations will have to be, whether the specialised turbines will perform as predicted,or worse, or just break. We have seen windmills disintegrate before now..

There are also uncertainties in what the spot and average electricity prices will be. IF we built a 100 or so nuclear power stations at a very predictable cost, and to a standard pattern, the electricity cost might run below break even for this project, easily.

Anyone with a vested interest in this project would be the first to dis any nuclear option. As the greens currently are.

[Roger]

The message from The Natural Philosopher contains these words:

How on earth do you come to that conclusion? The scheme would mean that the tidal range would be reduced by half. The birds might feel the impact (assumimg the food they get there is the limiting condition on their overall numbers) but no one else is going to mourn the loss from sight of acres of mudflats.

First erect your strawman ...

Tell that to the 307 who died on the East Coast and the more than 2000 who died in Holland during the Great Flood.

I wasn't suggesting you would. Only that any power from a flood defence scheme would be a bonus.

Every little helps and 2 GW of dependable power is more than a little and much more dependable than 2 GW of wind power.

Every estuary is a potential tide mill. Dam enough and you could provide for all the UKs needs 24/7.

Every little (and not so little helps). A better bet than relying on fickle wind and secondhand wind (wave) power.

[The Natural Philosopher]

Oh yes.

At current oil prices everything is up for grabs. With oil at the prices it is, it makes economic sense to use as little as possible, and teh alternative is non fuel generated electricity, for which a distribution system, albeit under strength by a factor of about three, already exists.

The very title of the thread reflects that the economics of electrical power on our most efficient stations undercuts road delivered domestic fuel for HEATING. Not running cars on.

I think the UK needs more than 44GW electricity however..I thought peak demand was nearer 100GW...it might well be 44GW average.

I got the 350GW from a peak to mean calculation and a notional 40% efficiency applied to total energy usage in the UK....probably worth re-doing though.

We have to have enough CAPACITY to run the country on the coldest days assuming very minimal storage available.

Since I was looking originally at the ability of windmills to deliver it reliably as against nuclear power - in neither case is there any appreciable 'fuel costs' the *average* levels were not of interest.

It was an excercise in comparing the capital cost of windmills and the much much larger grid (and possible storage systems) against nuclear, and the simply larger grid, and both working on the assumptions of viable battery/electric vehicles.

Because I cannot see that we can rely predominantly on imported carbon fuel to maintain any standard of acceptable living, at current prices.

I can predict what wil happen: At least one more seriously big coal fired station will be built, and then EDF or EON will buy British energy

- almost recouping half the taxpayers purchase of Northern Rock (govt stake in BGY is about £35 bn) and start putting up new power stations on old sites.

The national grid will be a pain in the arse, but will eventually go into the sort of continuous upgrade mode needed to keep pace with demand, and little people like me will be putting in heat pumps and electric boilers.

Meanhile someone will come up with leasable electric cars, as no one will want to take the risk of the batteries being crap, and uptake for small domestic use will be large.

And the government will quietly start taxing electricity up to recoup the losses it will be seeing as fuel taxes drop, under probably the guise of some eco-tax.

Windmills will simply fade way, as will tidal schemes. As the overall cost of them is finally realised.

[The Natural Philosopher]

At a million quid a mile?

More expensive than supercapacitors ;-)

[Roger]

The message from AJH contains these words:

No, I thought it too risky but the risk was to the shareholders, not the developers who probably were well rewarded. The basic mistake the chunnellers made was to underestimate the degree to which the ferry companies could reduce their cartel prices and still be profitable.

[Doctor Drivel]

What Maxie fails to recognise is that the water is running downhill of 180 foot. Probably 200 foot at low tide and only 160 foot at high tide. That 40 foot difference in level can make the difference - the idea is to keep it around 200 foot. They were also talking about cutting out restrictions to improve the water rate as it travels downhill. The bank sides can restrict the flow as all the water is funnelled between the banks. And it will back up as it just cannot run down fast enough. The river is a pipe with the top cut off. Make it wider at some points, deeper in others to hold more water, smooth out bends or put in short canals to assist in flow at bends, etc. Weirs upstream can keep water back too.

They recognised that water entering the tidal estuary was not flowing in faster enough because at times as the estuary water level was too high - high tide. This water backed up and restricted river flow.

[Jules]

Bah, run the wires through the channel tunnel. When the blackouts start, what's more important - power for the country, or convenient access to a dirty weekend in France? :-)