Swansea Bay–The Basic Facts
June 26, 2020
By Paul Homewood
Given the renewed interest in the Swansea Tidal Lagoon, it is worth republishing a post I published in June 2018. It still seems as valid now as it did then:
This letter appeared in the Telegraph the other day:
Leaving aside the question of HS2, the writer shows a total lack of understanding about Swansea Bay, which is probably due in turn to the wholly amateurish way it has been treated by most of the media.
So, for Tess’ benefit, here are a few basic calculations:
- Cost of lagoon – £1.3bn
- Electricity produced – 532 GWh pa, which is 0.15% of UK generation
- This is enough to supply on average 40,000 homes
- Therefore the cost per household is £32,500
- There are an estimated 107,500 households in Swansea, so the lagoon could not even supply half of the town.
- Even after the capital costs, ongoing costs will be substantial, for instance dredging and maintenance and replacement of turbines.
If Tess thinks that sounds like a good deal, heaven knows what a bad one looks like!
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NOT A LOT OF PEOPLE KNOW THAT 
On the other hand.
The generation of electricity will be predictable, unlike other renewable sources.
What are the savings generated by reduced flooding further upstream?
There will be jobs created.
Another source of income could come from putting a railroad on top of the polder/dam (that would also help reduce maintenance costs).
There is the possibility of bird life being harmed by loss of habitat. Such habitats can be recreated nearby utilising by products from the polder.
It’ll be a huge project.
Just because it’s difficult doesn’t mean we shouldn’t do it.
You seem to be thinking of the Severn Barrage, which IMHO would be a good idea. The Swansea lagoon would have no effect on up-stream flooding, you couldn’t put anything on top because it doesn’t go anywhere. You are right it would be a huge project, but one that gives very return on investment.
Harry
You are correct.
My mistake.
I think I’ll sit on the naughty step and keep quiet
Not quite no effect… The barrage would go right up to the mouth of the River Tawe. I suspect the construction would also affect the mouth of the River Afan which emerges at Port Talbot. Changes in the water circulation would likely lead to silting of channels into both ports (there is a scouring circulation around the bay from the Mumbles that performs some natural dredging).
Nope, you can’t have the naughty step. I’ve got it booked long term.
Stewart,
“The generation of electricity will be predictable, unlike other renewable sources.”
Predictability is not a virtue. Knowing my car will not start tomorrow morning is still rather annoying.
“What are the savings generated by reduced flooding further upstream?”
This is a tidal lagoon…..no “upstream” at all.
“There will be jobs created.”
Sweeping the street is also a job……so what.
“Another source of income could come from putting a railroad on top of the polder/dam (that would also help reduce maintenance costs).”
Where on earth do you think this “railroad” will be going from and to?
“There is the possibility of bird life being harmed by loss of habitat. Such habitats can be recreated nearby utilising by products from the polder.2
What habitat is being lost? This is a tidal lagoon around a bit of sea.
“It’ll be a huge project.
Just because it’s difficult doesn’t mean we shouldn’t do it.”
Is your name Tess Samuelson?
Nope, he has already admitted that he had confused it with the Severn Barrage. You would have known this had you followed the sound principle of “read before rant”
I dug out a PhD thesis I referred to when I was helping Roger Andrews and Euan Mearns with assessing tidal projects. This one dates from 1988, but is actually much more informative than some of the other papers and prepared to discuss some of the real practical problems. It provides a solid underpinning for the modelling used – the entire model is listed (in FORTRAN!) – a lesson for one N Ferguson, along with data and output for a Severn barrage, which was assessed as capable of generating some 12.8TWh/year. Those who want to dig for themselves can find it here:
Click to access 381648.pdf
I charted up the various water levels and generator output for a peak spring tide and a low amplitude neap tide to show what the optimised output would look like. There is a lot of waiting time after high tide before generation starts. Starting to generate earlier means that the head (difference in water levels) starts low, generating less power, and chases the tide level down, reducing the maximum output, and running out of head altogether as the tide starts rising again. There is almost a tenfold difference in energy output between the spring tide and the neap tide. Maximum power in the neap tide is barely a quarter of that in the spring tide, and the duration of generation is much shorter. Switching in 3GW of supply at the start of generation in a spring tide is no easy matter for the Grid to handle: in practice there would be a limit on ramp rate of say 100MW/min. Losing the 7GW peak output due to a fault would be a nightmare likely to result in blackout.
https://datawrapper.dwcdn.net/II88f/1/
Predictable – more or less, give or take storm surges, which can change timings as well as tide levels. But horribly gap toothed, and a grid nightmare, requiring extensive backup both to cover the gaps and spinning reserve to avoid blackout trips.
These exchanges tend to get emotional and the more factual and data oriented you get the worse it gets because then it appears that you “don’t care”.
Something most deniers may not appreciate is that the climate change thing is an emotional issue.
Bill McKibben for example. Even the scientists. Kate Marvel for one and that lady from Texas. Also that lady from Ireland shedding tears for the oceans being acidified. What is another science driven by emotion and legitimized by brandishing the word science?
I cannot agree that it is an emotional ‘issue’. The issue is surely one of scientific fact – the emotions are overlaid on various premises. For some obscure reason the progenitors get much more animated than the ‘deniers’ who deal in facts.
It shouldn’t be, but it is. Climate science has been co-opted by political operatives/social justice warriors, not credible scientists, and turned into an ism/ology.
Thank you for your input
chaamjamal, you could apply that to virtually anything in life from vegetarianism to fishing in the North Sea etc.
Maybe so. Thanks.
Looking at it from an investment perspective, the annual 532GWH equate to around £21.3m (at £40/ MWH). So knocking off some running costs and a sinking fund to replace plant I’d guess at a ‘return on investment’ of around £15m, or 1.15%. Most infra investors would be looking for a ROCE of
10-12%. It’s just not an ‘investable’ deal.
Ho, dondn’t worry they want a lot more than £40/ MWH, at least 3 times as much
Their original bid was for £168/MWh in 2012 money, guaranteed and indexed for 90 years. That would already be worth £194.84/MWh if they started generating tomorrow.
My memory is dusty but isn’t the businessman pushing the Swansea Lagoon project a little bit of a chancer?
Almost right. You should not have included “little bit of”.
From 4 years ago is this paper Wave and tidal current energy – A review of the current state of research beyond technology.
(https://www.sciencedirect.com/science/article/pii/S1364032115016676 )
The conclusion is very interesting —
They call for a “broad cost benefit analysis” of these systems, now that would be new for so called ‘sustainable’ or ‘renewable’ technology!
Has anything much changed since the late Roger Andrews skewered this 5 years ago? Sadly the site that hosted many of his diagrams folded, but you can see them on the wayback machine if you go here:
https://web.archive.org/web/20150528060550/http://euanmearns.com/a-trip-round-swansea-bay/
Yes there will be plenty of siltation to be cleared regularly before the turbines are compromised .
Before a letter goes to the Telegraph to bring Tess up to speed should we not be able to say what the feed tariff income will be as a return on the £32,500 capital cost per household.
And then there is the cost per dwelling of the zero carbon enhancements.
Its all a bit complicated but I’m sure that a Telegraph reader will relate to stats. expressed on a per household basis.
I think 13.3MWh per home is rather high for electricity (2.5-4+, depending on who is claiming…), but probably a bit low for overall household energy consumption. The “home” is one of the most flexible units of energy known to man. MTOE would be better!
This is Euan’s analysis of tidal, comments below are informative:
http://euanmearns.com/energy-externalities-day-13-tidal-stream-power/
I suspect you meant to link to the tidal lagoon evaluation rather than the tidal stream one. Tidal stream relies on fast flowing tides, such as the Meygen scheme in the tidal race between Scotland and the Orkneys.
Here’s the lagoon page
http://euanmearns.com/energy-externalities-day-10-tidal-lagoon-power-a-roundup-of-results/