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

[Tim w]

The company has been working on the Swansea lagoon proposals for some years and it seems likely that they will get the go-ahead from the Secretary of State very soon.

The news item is simply the publication of a list of sites for possible new lagoons, where some draft specifications have been drawn up and some research and consultation has already begun in private (which is how I know).The most important factor in site selection is tidal range, so the Bristol Channel sites are really the front runners.

My own view is that as much as I would love to see clean, green energy secured for years to come there are several issues on which the lagoon company is unable to do more than flannel, cross their fingers and hope for the best. The most significant of these is 'siltation', impossible to model accurately the extent of it, but sure to happen. The publicity shots of a clear blue Swansea lagoon with fish swimming under windsurfers is fantasy. The reality is it may fill very rapidly with mud and become a monument to wishful thinking.

Hopefully the Swansea experiment will be allowed to run before construction begins on any of the others because the potential for environmental damage in terms of the effect on rivers, estuaries and shores - the ecosystems, wildlife, the erosion rates, the flooding, the visual impact etc.- is enormous.

Tim W

[The Natural Philosopher]

Well no, we don't. Wave power changes with the weather, tidal power changes with the moon. Its fundamentally different

As crap as any other intermittent undispatchable energy source

[The Natural Philosopher]

the economics depend on them being run flat out and they will always - like wind sell what they have on a use it or lose it basis.

[The Natural Philosopher]

absolutely. four times a day every day the tides are not coming in or going out.

Every seamen knows that. Didn't you?

I treat that with the total contempt it deserves

No, but it seems you really are.

[The Natural Philosopher]

Just before they start going out, you unbelievable moron!

[The Natural Philosopher]

The key lie is of course how much the energy will cost people like the national grid, who have to connect to it, and the operators of gas power, who will see this power eat into their income, and yet still have to keep their power stations running for the 4 times a day the tidal power ain't producing anything.

[cl]

But tidal is surely only available for about half the time, you can of course 'turn it up and down' while using it, in fact water driven turbines are very useful from this point of view for responding fast to changes in demand. However, as I said, surely the tidal lagoons can only provide power while there's a water level difference between one side and the other and that cannot always be true.

[charles]

even though I'm not a seaman, I have heard of "slack water"

[Chris Hogg]

The point being that, as the Beeb article says, the power from these lagoons will only be available for 14 hours a day. A similar situation will exist for any tidal electricity scheme, whether barrage, lagoon or tidal stream generator. So where does the electricity come from for the remaining 4 periods of 2.5 hours each, especially on calm cloudy days when wind, wave and solar aren't producing anything either? If you can store massive amounts of electricity or the energy equivalent, especially from renewable sources, you can store it when there's excess available on the grid to carry you over for when the wind doesn't blow, the tide turns, the sea's flat calm and the sun don't shine (assuming of course that you've spent gazillions on Renewables to provide that excess generating capacity and to reconstruct the grid to handle the extra power, in the first place). Only in that way can you safely close fossil-fuel-burning dispatchable generators to minimise CO2 output, assuming that that's actually necessary. Alternatively, eliminate CO2 by building nukes, like the French. Costs no more than lagoons, and runs 24/7/52.

PS: TNP is right; wave power should not be confused with tidal power, whether from lagoons, barrages or tidal stream generators. The sources of energy are different, for a start. Wave power is another form of wind power, whereas as you point out, the others derive from the gravitational pull of the moon. They will require different technologies to harvest the energy in them.

[Andy Dingley]

Wave power sucks. It's trying to extract from a relatively small total amou nt of energy (waves are smaller than tides), and doing it from the active s urface of the sea, an environment infamous for wrecking ships, stripping pa int and growing barnacles over the remainder.

Tidal power makes much more sense.

The low-hanging fruit for tidal power are free-standing submerged turbines. We have the knowledge and spare yard capacity post North Sea to build them , even to export worldwide. They operate in a relatively benign environment of shallow seawater, permanently submerged and out of the waves. The opt imum sites are the intra-island tidal races already avoided by shipping. Th eir cost is tiny in comparison to mega-barrages.

For impounded tidal on the Severn, why not go low-cost and use the existing and abandoned dock infrastructure of Barry, Newport and others? Turn those into tidal pounds, an idea that has been around since the Medieval peri.od . No monster earthworks to build, quick turnaround and no environmental tra shing of a major estuary.

[The Natural Philosopher]

First correction 'any power at all'

The whole point is the huge cost that renewable intermittency imposes on everyone else EXCEPT the people who are building and running 'green' technology.

The red herring is the argument that knowing when your power source will let you down reduces the cost of dealing with it. It doesn't.

[dennis]

Bob is being silly, wind mills are stupid but wave power is also powered by the wind so it must also be stupid.

I hate to think how much more dangerous building and working on the wave gubbins would be when compared to a nuke.

Even building a tidal barrage would be more dangerous than a nuke. We have figures to say how many are killed in each of these generating schemes and nukes are not the worst.

[Tim Watts]

It's a newspaper comment section. It's part of the national effort to keep the mentally ill off the streets.

Pick a story - any story - the comments are roughly thus:

"Earn $$$ doing something..."

"This is stupid"

"This is great"

"You're racist"

"The Muslamics are taking over the world - why am I not allowed to comment on "

And if you are lucky, 2 insightful comments out of 765.

Slashdot solved this problem years ago...

This is why I set Adblock to actually knock out the entire comment section on most rags I read.

[The Other Mike]

usenet postings can be written at one time and batch sent minutes hours or days later

I read the article before I commented here

[Theo Markettos]

Yes, but the tide times across the country are different.

At the moment it's low tide at Anglesey, rising tide at Swansea, high tide at Whitby and falling tide at Aberdeen. If you build enough tidal plants in different places you get to average the tides across the country. And the distances are short enough that it isn't infeasible for Anglesey to keep the lights on in Swansea when Swansea is at slack water. It isn't like solar where you need to go thousands of miles to be always connected to somewhere where the sun is shining.

Theo

[The Natural Philosopher]

Oh dear Theo

guess what the tidal range at - say - whitby - is, compared to swansea?

Do you know anything about tides?

Here. guess the answers to

what is the tidal range at: Cardiff Copenhagen Cyprus

[Chris Hogg]

For those wishing find support for tidal power in whatever form, MacKay has some encouraging words on the matter.

and following pages. He gets more technical and quantitative here and following pages. All rather theoretical, and nothing about cost, though.

[Theo Markettos]

Yes, you get less height of tide. Those places weren't picked specifically for their suitability, just random tide times. However you can still manage in a place of lower tides by building a larger lagoon. Though I don't know what the minimum hydrostatic pressure is to make it worthwhile - what the breakeven height of tide is.

Since the only part of the water column that matters is the intertidal zone, there may be places where the seabed is shallower and it's cheaper to build a larger lagoon, compared with places with higher tides but you have to go deeper to build the seawall. I haven't looked at the proposed sites in detail.

Theo

[Nightjar]

I didn't from your first post on the subject, as wave power is quite different from a barrage system. The Severn barrage would cause massive ecological harm for no discernible benefit, while wave power has yet to be made to work.

It probably carries similar risks to other hydro powers systems, which would make it about 2.5 times more likely per TWh to kill people than nuclear; 25 times if you ignore Chernobyl as a one off, or 35 times if you include both Chernobyl and Banqiao.

[Tim Streater]

And the minimum is zero, and there's nothing you can do about that. Meaning you need other forms of power to back it up.