Sense, at last!

[Workingman]

It looks as though the tidal lagoon in Swansea bay is to get the go ahead.

In itself it is a big project, but it is also a test bed for things to come. At £1.3bn over its projected lifespan of 120 years it is a bargain when compared to other infrastructure projects. The building of it will put the UK at the cutting edge of the technology, which could be very profitable.

Also. if the producers can get a guaranteed price of £89.90/MWh, and charge us at the current average of about 12.5p/kWh, there is a big pot of money to be made and reinvest.

The main concern now is how it might affect the wildlife of the bay. It could be damaging, neutral or beneficial, nobody knows. However. it has to be built in order to find out and then see what might be needed for future projects.

I was reading the other day about how dams had created a problem with the increase in snails carrying a parasitic worm. Migratory prawns which fed on the the young snails had been locked out by the dams, yet still they were built. Projects are now under way to release young prawns upstream and modify the dams to allow them to migrate as they once did.

If the Swansea lagoon throws up any problems at least we will be able to mitigate them for the future.

[cromwell]

\Unlike the wind, you know that the tide is reliable!

[AliasAggers]

That really is good news.

As you say - Sense at last.

[Suff]

Sadly I've been looking at the figures and they don't add up.

11.5 sq km at 50m depth is 0.575 cubic km of water. The full potential energy of that water, falling 7m is 10 megawatts, if it all fell the whole 7 meters in one second. Notably the water in the lagoon is not 50m, their website says talks about feet but it is actually only 4m of water. 4M of water at 11.5 sq km is 501 kwh if it falls the full 4m. Which, of course, it can't because only the very top falls 4M, the rest falls ever reducing height. The longer it takes to fall the 4m, the less energy you get from it. I went through these calculations with the guys on the Arctic Forum last year.

So we know the whole water volume won't fall 4m. Yes the tidal influx will come in with tens of billions of tonnes of force behind it and will probably drive the turbines to the rated mwhrs. But the article claims it gets "all" the energy both in and out twice a day. influx comes twice a day for about 4 hours or so. So that's 8 hours per day. To get 320mwhrs for an equivalent 24 hours per day, it would have to get nearly a gigawatt of power on each tidal inflow.

I cannot see the claim to be true. The water force entering comes with the force of the entire ocean behind it. The water exiting is with the force of the difference between the water in the lagoon and the water outside.

Sadly it's not magic.

I'd love to see a breakdown of their figures for generation, but the breakdown is not there. I know quite a lot of guys who could do a very good analysis on the real figures to be delivered.

The problem with selling something like this is that it's worse than doing nothing. It is nothing more than an opportunity to make money with someone else footing the bill. When they fail to deliver, spectacularly, like the wind turbines which average, across the UK, 22% of the year delivering energy, then people simply don't believe there is a problem.

I'd love this to work, but I will be very surprised if it does. The size and numbers are simply not there for the stated power generation.

Also the "Strike Price" of the electricity is only slightly less ridiculous than Hinckley Point, which was £90 per mwh. Current market price per mwh is £45 and someone has to foot the bill on the difference.

I really hate being so negative on this, but I don't want to see another "failed wind turbine" effect thrown in my face 10 years down the line.

[Workingman]

I hear what you are saying, and it is obvious. The incoming tide, with billions of tonnes of water behind it, is way more powerful than the outgoing lagoon tide, but that is only only at one location. Great Britain, the island, has tides coming in virtually 24/7. A few barrages, from John O'Groats to Land's End, give us good cover. If they are coupled with solar, wind, and the much underused and ignored small scale hydro, we could be going places.

The fact is that Swansea going ahead is something we can learn from. It will not solve our energy problems, but it will pave the way for for more practical solutions in the future - small steps, and all that.

[Suff]

Yes I agree with that. But the claims being made are so outrageous we'll get a backlash when they fail to come in as promised.

[Suff]

So here is the reason that wind turbines are favourites.

I found this article which does a sanity check on the Swansea project.

In simple terms the mean generating power output is 48mw to generate the stated 420GW hours of energy per year.

OK so 48mw hours average.

What does this come down to with wind?

The largest turbine, today, is 8mw. So we would need 6 of these to average the Swansea project.

But. As we all know, wind turbines do not run for the whole time. Let's take offshore wind and assume only 10% utilisation (offshore tends to run at around 20% to 30% so we're good there. That means 60 x 8mw offshore wind turbines.

Looking at the cost per MWH of wind turbines, China naturally as EU costs are nearly double, we get a cost of €192 million. Or £167 million. let's double that for installation costs on offshore. So we get £334 million for an offshore installation which can pretty much be guaranteed to deliver more than the Swansea project, when the wind is blowing of course. In fact when the wind is blowing it will deliver 10 times the output of the Swansea project.

In terms of cost you get 4 times as many offshore wind farms as you do Swansea Tidal barriers. Oh and if anyone believes the cost of Swansea will really be £1.3bn think on. These construction projects always overrun by at least 20%, sometimes up to 100%.

This is why Wind is still the darling of the renewable energy market and why I believe that we would need something more like tidal rise fall and HDR geothermal than wind or tidal lagoon.

Sad, really. Very sad. The only thing the Lagoon really has over wind is the renewal windows of the turbines will likely be 10 to 20 times longer. But, of course, the wind turbine generators will be cheaper than the whole infrastructure to replace.

Sad fact of life. Tide has the capability to give us what we need, but would need to be much larger in scope, about 1/4 of the price and be deployed on the entire western seaboard of the UK.

[Kaz]

Great idea

[Workingman]

I found this article which does a sanity check on the Swansea project.

What a strange critique of the project. The man tells us that it is a back of an envelope calculation, he then admits that the numbers are not substantiated by any real world observations. He also makes assumptions on how the project will operate because, as he freely states, he did not have access to the details. Nevertheless he ploughs on with his 'note' based on a non-existent and theoretical alternative at Port Talbot.

So let us do another envelope calculation. The average nameplate output of an offshore wind turbine is ~3MW, but with an efficiency of 33% (it is much less, but bear with me) it is effectively 1MW. The average cost of such a turbine is £3.1 and they have a lifespan of 20-25 years. If offshore wind was to replace the lagoon, taking his figures, the raw cost over its lifetime would be ~£820m. Add in maintenance, commissioning and decommissioning and the figure will be near to the £1.3bn of the lagoon. However, if we take the middle ground between his figures and those of the developers the costs go through the roof.

The thing about Swansea is that it is a pathfinder test bed. Somebody, somewhere, is going to build one, it might as well be the UK. The coastline of GB is about 18,000km and there will be a number of other sites where lagoons, if they work, could be located. The idea that they would all need be on the western seaboard is a fantasy. Only ten the size of Swansea would provide 5% of the UK's current annual demand. I agree that they would not be the whole solution, nothing ever is, but as part of a mix of all renewables they can be extremely useful.

[Suff]

It is a ROM article. Rough order of magnitude. All the points that he dismisses are areas which might reduce, not increase the yield.

The Wind turbines are not 33% efficient, they are 100% efficient to the stated power capacity, when the wind blows to that level. Which only happens, at best, 33% of the time.

I took a worst case argument and said it only blows at that rate for 10% of the time and you still get 4 wind farms for your one Swansea.

What I would like to avoid is the same situation we had with the wind farms. 20 years ago wind was going to save our power lives. All we had to do was stick up the masts and the wind would do the rest, job done. Nobody would hear arguments against it. Look where we are with wind today.

Portugal already harvests wave power, France has had tidal power for decades. This is not new, it's just not easily transferred to baseload power any more that wind is. Yes we have a long coastline, yes the coast spans more than 7.5 hours which means we're always generating power somewhere and pushing it into the grid. But the sheer size and cost of the installations, for the returned power generation, are going to turn people off eventually.

OK lets look at the reality.

Swansea

1.3bn 0.53TWh per year

Hinckley Point C

Assuming 24 hour operation 80% of the year.

18bn, 42TWh per year

Or, in other words, to create the same power generation capacity as Hinckley Point C, using Swansea tidal lagoon technology, would cost £29bn. As we use, currently, 301TWh per year for our current power needs, that's around 200 billion to replace the current grid power.

That doesn't actually sound so bad does it? Until you realise that when the wind turbines were being put in the figures used were quoting 50% - 60% useful generation time average overall. The reality? Overall average is nearer 20%. If the same were to happen with Swansea, we'd be spending the entire Annual GDP to replace our grid when we could get it for, potentially, £150 billion using Nuclear. Of course Nuclear fuel comes with it's own issues, most glaringly scarcity of fuel.

But you get my drift.

I worry that a good idea becomes abandoned because it was sold too high. If I were to hear a 100 year commitment to total grid replacement with wind, wave and tidal lagoon, I'd know they were really serious.