The Swansea Bay Tidal Lagoon: the folly & corruption of the political, media & business elite

Comments

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   Hanging is Far Too Good for Them

   10 June 2015, 03:43

   Mr W,
   You should google the Bishop Hill blog for the 9th June for a lot more info. WARNING: you will probably blow your top like Mt. Etna when you discover the full extent of this crime against sanity.

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   Striebs

   10 June 2015, 03:47

   Tom . Sorry long post but here is my back of an envelope calculation :-

   Like socialism , it may be necessary just to give it a go so people can see the realities for themselves .

   Assumptions :-
   - a tidal range of 7m and an infinitely steep beach . the volume of water in a full 1 km squared tidal lagoon using the shore as one side = 7,000,000 cubic metres .

   Density of sea water 1,020kg/m3

   Mass of water in a full 1 km squared tidal lagoon (or waiting to fill and empty 1km squared tidal lagoon) = 7,140,000,000 kg

   Constant for acceleration due to gravity 9.81 .

   If drained instantaneously at low tide , or filled from empty at high tide average “head of water” would be 7/2 = 3.5m

   Potential energy in a full/completely empty 1 km squared tidal lagoon

   = 7,140,000,000 X 3.5 X 9.81 = 245,151,900,000 joules = approx 245 billion joules

   The amount of potential energy which can be theoretically captured over the course of a day is 4 X the above i.e. approx 980 billion joules

   This is a theoretical maximum and would require the lagoon to be filled instantaneously at high tide and discharged instantaneously at low tide which of course is impossible . For arguments sake lets assume than 100% of the theoretical energy is converted to electricity for a consumer who needs it at high/low tide .

   By comparison , an AP1000 reactor electrical output power = 1,200 MW = 1,200,000,000 joules/second = 1.2 billion watts/second

   Seconds in a day = 86,400 .

   Joules electrical energy output in a day by AP1000 = 103,680 billion joules .
   i.e. one small compact nuclear reactor outputs over 100 times the theoretical maximum output of a 1km squared tidal lagoon .

   The practical maximum output of a lagoon is going to be less than 50% of the theoretical maximum .

   A single (as opposed to dual) tidal lagoon would be too dangerous for recreational use because it would have to be filled/discharged at artificially fast rates .

   I’m not saying that it couldn’t be done , just that I can’t see many suitable locations in this country and by the time local opposition has been overcome something better may have come along .

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   Striebs

   10 June 2015, 05:16

   Plugging in the numbers for the Swansea Bay tidal lagoon :-

   Acceleration due to gravity : 9.8 m/s/s Mass of seawater : 1,020kg/m3

   Swansea specifics :-
   - Max tidal range at Swansea : 10m
   - The breakwater is only 9.6km which would be enough to enclose a 7.3km2 circle but they are using the shore and thus enclosing 11.5km2 .

   Potential energy in a full/completely empty 1 km squared tidal lagoon with a 10m tidal range :-

   = 10,200,000,000 X 10/2 X 9.81 = 500,310,000,000 joules = approx 500 billion joules

   For a circular lagoon with an 11.5km area , the amount of potential energy which can be stored is :-

   500 billion joules * 11.5 = 5,750 billion joules

   The amount of potential energy which can be theoretically captured over the course of a day is 4 X the above i.e. approx 23,000 billion joules .

   The claim is that Swansea Lagoon will convert close to 60% of the stored potential energy into electrical energy when new . I’m a bit sceptical of this figure .

   However , using average tidal ranges of 9m and 60% efficiency, it should generate on average
   12,420 billion joules per day i.e. 12% of an AP1000 – though it still will not be despatchable energy .

   This amounts to 143.75 MW average electrical power but they claim “320MW installed capacity and 14 hours of reliable generation every day” so they are quoting peak output .

   At least it’s a lagoon rather than a barrage which would spell the end for migratory eels .

   For the sort of people who lap this sort of thing up , fish are only there to provide food for birds .

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   J P Spaghetti

   10 June 2015, 06:41

   Oh, I do love that bay – more about this to be found here:

   http://www.tidallagoonswanseabay.com/the-project/faqs/59/

   The following quote in particular made me a little uneasy “We have used independent expert modellers who communicated the results to our engineering team, who then adjusted the design to minimise the impact where possible.”!

   Anyway Striebs – blimey!

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   J P Spaghetti

   10 June 2015, 07:37

   Striebs – isn’t the average potential energy in a 1 km squared tidal lagoon with a max. depth of 10 m (so taking the average to be 5 m) equal to 50 (not 500) GJ?

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   J P Spaghetti

   10 June 2015, 08:08

   Tom – just one more from me re. the reality of global warming before I head out to enjoy the benefits of our nearest star. I don’t think there’s any reasonable doubt that it’s happening, but the extent to which it is being driven by the activities of mankind is the issue. Perhaps Striebs would like to have a stab at estimating just how much more energy is thrown our way via the interplanetary void during heightened solar activity when coronal mass ejections are observed – qualitatively, at least, the effect of anything we do here is minuscule by comparison.

   That’s not to say our activity isn’t exacerbating it. I suspect it is to some degree, but I believe the jury is still out on the extent to which what we’re experiencing is fundamentally part of a natural cycle, one occurring on the sort of timescale over which our politicians should be deciding energy policy (rather than one of parliaments).

   Vested interests aside, it seems to almost whiff of anthropocentric (don’t really think there’s a suitable alternative to that) arrogance to claim it’s dominated by human activity…

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   Striebs

   10 June 2015, 09:12

   J P Spaghetti ,

   The force is in newtons , not kg so we must multiply by the acceleration due to gravity of 9.81 metres per second per second .

   Thus the potential energy in 1kg raised 1 metre = 1 X 1 X 9.81 = is 9.81 joules

   I find it difficult to get angry about this whilst the traitorous Cameron is attempting to dock the UK permanently with the EU .

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   Marvin

   10 June 2015, 10:13

   Nice one. I’m going to get George Monbiot on the case.
   It’s time he got away from slagging off aspirational parents.

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   wildrides

   10 June 2015, 10:22

   As a former resident of Weston – Super – Mud and Bristol area for 20 years I know the area well . I am a deluded lefty and proud of it . However I am against the scheme but not for any of the reasons stated above . Why ? The waters of the bay are full of suspended clay carried down from eroded topography within the catchment of the river feeding the estuary . Hence the muddy waters and mud at weston . Geologists will all tell you that when you slow down the speed of water and limit currents to near the turbines sediment will fall out of the water settling at the bottom . The whole lagoon apart from a small channel near each turbine will silt up . This is how sedimentary rocks are formed . In 30 years there wont be a lagoon ……… just a clay filled basin full of reeds . Our country is too small ……. this is a secret land reclaimation project via the back door . Not a conspiracy because no one knows yet !
   If you want proof ……… there is a tidal bathing lagoon at Weston – Super Mare- called the Marine Lake . It fills with the tide each day and can be used by swimmers & bathers when the tide is out . The tide goes out about half a mile so it saves a long walk through thigh deep mud ( I am serious) which can be very dangerous . The lagoon silts up every year and the mud has to be dug out with bull dozers ready for the season . Thats what happens when you still a tidal flow ……… sedimentation at a very high rate .

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    J P Spaghetti

    11 June 2015, 06:35

    STRIEBS – I do realise that(!) but I skim read your post and think I might have misinterpreted what you meant (and sorry for dredging this up again – no pun intended there – but it was niggling me!). Anyway, there are more pressing issues over at NEW…