Tidal Turbines (vaguely boaty)

[aquaplane]

Am I right in thinking that the time of either high tide or peak flow varies around the coast?

I realise that the power output is going to vary with time at a specific location, but wondered if there would be some "smoothing" or whatever technical term they may use, as different places hit peak power output at different times.

[Telo]

Yes. It would allow a smoothing effect.

However there is a still a case imho for fuel cell R&D to capture the "surplus" energy produced outside of peak periods - would also make the windfarms more efficient imho.

[JackJ]

Got the answer from my friend Brendan on another forum. He too seems to be an expert at most things. His advice was not to bother as it would have a negligable effect on stopping the ozone layer. Thanks anyway.

[Alcyone]

He's correct, and I can see your confusion now. Putting a windmilly thing in the water won't stop the ozone layer. To stop the ozone layer, you'd need to put a much bigger windmilly thing in the air, and then spin it the opposite way to the way the ozone layer was spinning.

Seems like a lot of trouble to go to though, but good luck, anyway,

[Nick]

.

His advice was not to bother as it would have a negligable effect on stopping the ozone layer.

There are trailed generators available which are used by sailing yachts to produce electricity. There is no such thing as free power of course, so the drag created by the device will take a small amount off the boat's speed. On a power boat all such a device would do is increase the fuel consumption of the engine very slightly, thereby negating any beneficial environmental effect. Far better to simply fit a high power alternator if you require more amps for your wine cooler, as your engines are going to be running anyway.

The ozone layer was never really threatened by infernal combusion engines, it was the use of more exotic chemical propellants to spray our armpits (and other bits) that was the worry there. The ICE does however produce a lot of greenhouse gases, so if you wanted to do something to reduce your carbon footprint you could just ease back on the throttles a little bit in search of an ideal speed/fuel consumption balance for your particular boat.

[Olivepage]

"Putting a windmilly thing in the water won't stop the ozone layer"

True, but there is a strong economic argument for moving to other sources of electricity generation to replace fossil fuel.

The UK particularly is dependent upon imported fuel for gas, oil, coal and even nuclear fuel.

As such not only is there a security issue of maintaining supply in a potentially hostile world, but a substantial price risk. Witness the recent increases in oil and gas prices. If we could move to a system where a reasonable proportion of our capacity moves to water turbine systems these risks would be considerably mitigated if not completely eliminated.

I discount wind power as it is little more than a political gesture, and will never make a significant contribution to either CO2 reduction or risk mitigation.

Wave systems have much in common with wind - clearly so since one is the driving force of the other.

Tides and gravity are constant, and use of these forces is predictable and manageable, not to mention cheap) the prime requirements for a secure supply.

Add to this the elimination of "current account" (sorry for pun) costs for fuel and you have a solid business case to invest.

Why is it not been done?

Politics!

The government prefer to spend money to meet meaningless targets in a short timescale rather than invest over a longer scale to achieve a more effective and meaningful outcome.

One wonders why Kyoto targets were % of capacity none CO2 rather than defining a specific reduction in quantity of CO2 produced by generation, which would be much more meaningful.

[Alcyone]

Actually, I wasn't being serious.

[JackJ]

"you have a solid business case to invest."

Very interesting; you sound like my kind of chap.

Got any info on p/e, debt ratios, capitalisation, cash flow, and earnings to date and projected for any turbine companies. Might have a punt and even go long which makes a change for me (bit pissed off by the ban on short selling at the mo; cost my fund a few bob over the last couple of months, that and the unwinding of the yen carry trade - still made up for the latter by being in Belize ..... fund, not me!....and hedging through dollars).

and Nick, thanks for your cogent advice. Drogue a definite no go now if it reduces top speed (35 knots according to Fairline).

[Alcyone]

Actually, you could use one, but just when you were trolling.

[ParaHandy]

Is there any information on the duty cycle that these machines achieve?

The Rance barrier whilst not exactly the same might give a clue? the installed capactity is 240MW which generates 69,000 kwh (on average). If these figures from EDF are correct, the kwh ouput as a percentage of installed capacity is similar to that of one of the best offshore wind farms.

The tidal current in the Rance is second only in the world to Banff Bay in Canada and the operation of the Rance barrier would be more productive than would be the case at Strangford.

There is a good deal of scepticism over some of the reliability claims made about the Rance barrier. It narrowly avoided catastrophic turbine failure after severe corrosion was discovered and which was timeously cured by electrical charging of the structures. The cost of generation at £0.015 per kwh is also disputed by some who believe that the French authorities have magically omitted the barrier's capital costs.

[Olivepage]

I make that about 29%

Which is lower than I would have expected. Certainly the duty cycle, what proportion of the day they generate how much power, is a critical figure both for costing and to meet the sort of load it is planned to meet.

Not sure to what extent the barrage model would compare to a submarine turbine. I would expect a barrage to have an element of storage as well as producing an increase in water flow speed, which one would expect to give a better output.

Worth remembering that the thing is some 40 years old so presumably the capital cost has been paid.

Not sure to what extent the capital cost may have been credited to anything other than generation that the barrage may bring, transport, shipping, leisure etc.

[ParaHandy]

Which is lower than I expected .... which one would expect to give a better output.

that's what i thought and before scribbling i'd double-checked.

Worth remembering that the thing is some 40 years old so presumably the capital cost has been paid.

Ah ... Scottish Hydro were flogged off for nothing on the basis that the capital cost of renewal was so high! I think Hydro's generating costs were broadly similar? The Rance barrier is having all 10 of its turbines lifted out over the next 10 years and that is expensive apart from the loss in revenue.

[Olivepage]

Well all these things whether water, coal, gas or even nuclear need maintenance.

At a guess only 10% of big power stations will be able to deliver 100% of their rated capacity.

To make it worse these things can also go wrong, like the time they stripped down one of the 660MW sets at Drax. They were lifting the main rotor out of the turbine when the chain broke and dropped the thing -about 40 tonnes of it - back into the stator casing.

One of the saving graces of using a large number of relatively low power machines is that losing the odd one or two will not be missed.

[ParaHandy]

I make that about 29%

assuming slack water at either end reduces generating capacity by 15% each, which leaves 70% available, and assume average power generated is 50% of full load, then the generating capacity is 35%? Knock off a bit for removing lobster pots etc and you're at 29% or so?

It's not that attractive?

[Olivepage]

Why would you run the machine at only 50% of full load.

Whatever generation method you use will be inefficient if only run at half load.

Its really a question of how you fit this method of generation into the overall system. If you have a suitable spread of machines such that the total output is more or less constant then you would look to using this for base load, which will allow maximum output to be used.

I wonder if the French grid managers, having such a large base of nuclear capacity use this for base load and have the water turbines as a short notice back-up. Certainly, assuming your numbers are about right then having only Rance available it would be unlikely to be used for base load.

It could also be used as a back-up to wind power so that together they may be able to make a significant contribution, but again this limits you to 50% utilisation at best.

Which brings us back to government. Until someone starts to make some serious, long term investment decisions based on a properly thought out, long term strategy for power generation then it is difficult to make decisions for any particular method of generation. And since the government are looking six ways for Christmas on the subject it seems unlikely that anything will happen in the short term.

So we continue with the present system creaking along with equipment failures so that at times it is close to forcing voltage drops and soon, I would guess, power cuts.