OT: Plans to generate electricity from 6 tidal lagoons in the UK.

[Tim Streater]

Notice, too, that you have no control over *which* 14 hours a day you get some power. So you can't even match the 14 hours with the daily peaks.

[Tim Lamb]

In message , Tim Streater writes

Umm.. If you could find a site where raising the sea level does not devastate some holiday resort, perhaps this would overcome the lack of suitable sites for pumped storage?

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[Nightjar]

...

The problem is that you can only run flat out when there is sufficient head of water on one side of the barrier or the other, which will be rather less than half the day at times that will vary according to the tides.

[Nightjar]

On 02/03/2015 10:07, Chris Hogg wrote: ...

There are other technologies being investigated, such as compressed air storage and liquefied air storage. It is claimed that adiabatic compressed air storage plants currently under construction in Germany will achieve storage efficiencies of around 70%, compared to 70-80% for pumped water storage.

[The Natural Philosopher]

You cam live next to a 5GWH store of compressed air if you want. I'd FAR rather live next to a nuke...

[The Natural Philosopher]

efficiency of pumped storage is largely a matter of the actual 'head' so pumped storage over a 30ft drop wont be very efficient.

[dennis]

And no power as they are tiny.

Damming the Severn was only going to provide a couple of GW for a few hours a day.

[Tim Streater]

And you wouldn't get a single watt out of it until the whole barrage was complete.

[Chris Hogg]

The German RWE-ADELE says: "In day-to-day charging and discharging operations, a commercial plant should store some 1,000 MW hours of electrical energy and feed some 300 MWel into the grid for several hours"

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A major factor in maintaining the efficiency is recovering the heat of compression. Still a way to go yet, and the target above is only a tenth the capacity of Dinorwig which can store some 10,000 MWh (1,700 MW for 6 hours). You'd need quite a few compressed gas storage plants to store the massive amounts of power needed to iron out fluctuations in renewable sources.

More stuff of a general nature, here

[Chris Hogg]

Hydroelectric is very predictable. In Norway almost all of its electricity is hydroelectric

and it exports a substantial amount annually to Denmark when the wind doesn't blow there, to make up the shortfall. Sweden also uses a large amount of hydroelectricity, about 50%, with 40% nuclear .

These sources are predictable and available continuously, without 4 interruptions per day due to slack water. If any of the tidal systems get the go-ahead, not only will they be expensive to build, but the consumer will also have to pay for the back-up generators that need to be kept on stand-by, to be brought in at those slack water periods; paying twice, in other words. I just hope Ed Davey appreciates that.

[The Natural Philosopher]

I think we have all worked out that Bob Henson is a green blob shill for a tidal power company, by now.

Hydroelectricity is one of the most reliable and predictable sources of power. As long as it rains...

In Norway almost all of its

[tim.....]

Except that tidal power is available at entirely predictable times and by placing them along the coast line at (say) 30 minute "intervals" can be used to generate a fixed amount of load 24-7.

and I suspect that there is some flexibility in when you open the sluices so they can also be used to generate a peak load

what I don't understand is why does the second one cost so much less than the first

tim

[tim.....]

there is no reason at all why you can't use a half level tide to generate less electricity at a peak time instead of waiting for a full tide at a time when the power would be wasted

tim

[tim.....]

one tidal generate is useless in this respect, but you can usefully use a chain of them along the coast line

[Tim Streater]

Odd that no one has done it then, eh? I expect they costed it and found it to be a lot more expensive, in particular for maintenance, than might appear to be the case at first sight. Particularly since this stuff is, like the windmills, open to the elements and so will be a target for rust and getting clogged up with barnacles and mud. Unlike a nuke which is inside a nice weatherproof building.

I would have thought the sluices would be open all the time, to generate power in both directions.

[tim.....]

Oh I didn't say that it was cost effective, just that it was possible

Whether it can become cost effective depends upon the costs of the alternatives.

There will (IMHO) come a rime when we no longer have "cheap" plentiful fossil fuels (but not in my lifetime), but, of coure we are going to have invented nuclear fusion by then :-)

surely the preferred method of generation will be: fill the lagoon up completely at high tide, empty it completely at low tide providing 4 "peaks" of electricity every 24 hours BICBW

[The Other Mike]

Yes tides work like that but they also vary drastically in range making tidal generation in many areas of the coast useless, coincidentally they tend to be the ones prone to coastal erosion so you can't even use the barrier in a dual role as sea defences.

So it's expensive, uses astronomical quantities of concrete and aggregate, needs an enormous subsidy to even get someone remotely interested in building, is unproven on a large scale, has unknown, unquantifiable environmental implications, and requires multiple landscape destroying sites to intermittently supply less than 10% of current demand, displacing reliable despatchable generation and making it even more uneconomic.

Wind turbines, tidal, wave, solar and biomass are not the solution.

[The Other Mike]

You might have but I haven't and see no reason why I nor anyone else would

Or snows

[The Other Mike]

Of course it will be viable with a subsidy like that, you'd have to have the engineering abilities of Harriet Harman and the financial abilities of Ed Balls to not make it viable.

There is no indication of what the electrical output of this tidal scheme will be, just the usual media ecobollocks spin that it will supply 155000 homes

So for the purposes of this calculation I'll assume a ballpark figure of 4MWh per annum per household (equal to around 450W steady load 24/7/365) that retails at around 500 quid per annum at 2015 prices

So that means they are looking at generating a maximum of 620GWh / annum

Or to put it another way the averaged output of this tidal scheme is

620x10^9 Wh / 8760 = 70MW

Yes I know that is 24 hours a day rather than the possible 14 hours per day but at least it is something to work with.

We know the subsidy for this tidal monstrosity is £168 per MWh, that is 28.2 million pounds of subsidy per annum, not that much you might say when there is supposed to be a 1bn investment. Why is a subsidy even needed to make the project 'viable' at a level of around 3% of capex per annum?

I can go out now and buy off the shelf a brand new 65% thermally efficient CCGT power station that produce around 1.2GWe for less than that, that's everything, the site, the connection to the grid, the planning, the gas pipeline. It commands no subsidy.

That 1billion investment together with the output of around 15% of a sister station would ensure reliable supplies round the clock for at least the next twenty years to over 2 million homes, at under 10p per unit retail, albeit with some volatility on fuel prices.

2 million homes supplied reliably for 20 years or 155000 homes supplied on an intermittent basis that, if all those homes carried the entire cost of the subsidy, would hike their existing bills by 182 quid per annum or 36%

Why should the consumer have to stuff the pockets of some tax exempt green wanker just to keep theirs lights on, cook and keep warm for maybe 14 hours per day? Do we need new clock faces with just 7 hours marked and then a 5 hour stop period where we all go into deep hibernation?

The question has to be asked is why does it cost 1billion pounds for something with just 70MW average output? It's landscape destroying crap, subsidised by the consumer. The greens and their offshore pseudosocialist benefactors will love it.

[Jethro_uk]

When I worked in the garage trade, our compressor had to be inspected visually every year, and every 2 years have an internal inspection (oo err missis !).

The assesor who carried out the inspection removed a plate which was mounted internally against the wall of the tank, and used a torch and endoscope to look at the surface, and check for corrosion. He didn't expect to find any, but warned us what the workshop - or rather what would be left of the workshop - would look like if the tank blew at full pressure.

In this case full pressure would have been about 180psi (OK, I admit it , I hate imperial, but really can't recall psibar ... about 6 bar ?) and the tank was rated up to 200, with a metal plate certifying it had been hydraulically tested to 312psi.

I dread to think what pressure would be needed to contain 5GW !!!!

A rough guess of "motor power" x "time to pressurise tank" with volume of tank thrown in (about 2m3) suggests that the tank at full pressure (180) would have stored about 2Kw x 180 = 360Kw. One wonders what energy is released when a grenade goes off ?

As an aside, that tank was built in 1964. The quality of fabrication is flawless - it's still in daily use apparently. Along with the lathe built in the 1930s - a Colchester.