Mon, 18 May 2026 04:19:20 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195603#Comment_195603 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195603#Comment_195603 Fri, 07 Feb 2014 13:19:40 +0000 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195605#Comment_195605 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195605#Comment_195605 Fri, 07 Feb 2014 13:21:30 +0000 SteamyTea https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195606#Comment_195606 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195606#Comment_195606 Fri, 07 Feb 2014 13:23:18 +0000 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195607#Comment_195607 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195607#Comment_195607 Fri, 07 Feb 2014 13:23:43 +0000 owlman Could re name it Wetminster.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195608#Comment_195608 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195608#Comment_195608 Fri, 07 Feb 2014 13:24:45 +0000 SteamyTea Thing is they can have recreational usage as well, nice safe place to learn to sail in, maybe a bit of fishing or fish farming could take place too.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195609#Comment_195609 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195609#Comment_195609 Fri, 07 Feb 2014 13:25:25 +0000 jamesingram What about the uncontrollable nature of nature , wont these be at the mercy of the weather and like all
sea defences requiring constant maintenance to stop them getting washed away?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195612#Comment_195612 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195612#Comment_195612 Fri, 07 Feb 2014 13:30:57 +0000 SteamyTea https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195615#Comment_195615 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195615#Comment_195615 Fri, 07 Feb 2014 14:17:45 +0000 ferdinand2000
That's £550 per house per year.

- annual output of 420GW/h and a design life of 120 years.
- Tidal Lagoon Power has put in a development consent order under the Planning Act 2008, but must convince the government to provide subsidies of £156 per MW/h – even more than that going to offshore wind farms.
- the Swansea Bay tidal lagoon, which as well as providing light and warmth for 120,000 local homes could also become a centre for sailing and other recreation.

http://www.theguardian.com/business/2014/feb/06/swansea-bay-tidal-lagoon-power-planned

I wonder what the payback would be for spending £65m a year on EWI or other eco-projects given typical savings .

Ferdinand]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195616#Comment_195616 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195616#Comment_195616 Fri, 07 Feb 2014 14:19:10 +0000 skyewright Posted By: jamesingramwont these be at the mercy of the weather and like all
sea defences requiring constant maintenance to stop them getting washed away?
Hopefully they'd be used for generation and a proportion of the income would be directed to maintenance (& replacement)?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195617#Comment_195617 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195617#Comment_195617 Fri, 07 Feb 2014 14:24:09 +0000 SteamyTea https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195635#Comment_195635 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195635#Comment_195635 Fri, 07 Feb 2014 17:05:08 +0000 fostertom https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195643#Comment_195643 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195643#Comment_195643 Fri, 07 Feb 2014 18:25:21 +0000 Jonti
Ferdinand said

'According to the numbers in today's Guardian article the initial Cardiff Bay scheme needs an annual subsidy of £65m to provide electricity for 120,000 homes.

That's £550 per house per year.'

If we halved the average use that would mean 240'000 homes and if we charged these 240'000 households an average of £550 each then no need to subsidise. Simple really

Jonti]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195644#Comment_195644 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195644#Comment_195644 Fri, 07 Feb 2014 18:54:52 +0000 Seret Posted By: fostertomLike, the only mainline railway that makes an outright profit for its owners, so draws no govt subsidy, is GNER.

It's no unheard of for a rail franchise to not include subsidies. I know the Gatwick Express never took any subsidy before it was absorbed into the South Central franchise.

Folks overbidding for the rail franchises has been an issue, but hopefully in the future they won't be allowed to simply walk away when it hits the fan. This should discourage some of the silly bidding that's been going on.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195646#Comment_195646 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195646#Comment_195646 Fri, 07 Feb 2014 19:22:34 +0000 barney
I calculate it to be 500KW - so to displace a 1GWe thermal station we need a basin of 2000 km2 - obviously more depth would require less area - but it's still a pretty big patch of water given that the whole country is getting quite excited about significantly smaller areas of considerably less depth across Somerset.

Water doesn't really have the energy density needed to become mainstream

Regards

Barney]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195651#Comment_195651 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195651#Comment_195651 Fri, 07 Feb 2014 20:23:54 +0000 atomicbisf Posted By: barneyGoing back to "I love Lagoons", Taking an average 2m tidal range what is the daily average power available from 1km2 of water?

I calculate it to be 500KW - so to displace a 1GWe thermal station we need a basin of 2000 km2 - obviously more depth would require less area - but it's still a pretty big patch of water given that the whole country is getting quite excited about significantly smaller areas of considerably less depth across Somerset.

Water doesn't really have the energy density needed to become mainstream

Regards

Barney

Hmm, I think not as all the largest power stations in the world are hydroelectric. Itaipu in Brazil/Paraguay and the Three Gorges in China both produce roughly 100 TWh per year (the UK consumed 363 TWh in 2010).

Obviously the UK doesn't have any rivers to compare with the Parana or Yangtze but most of the projections for a Severn barrage from Brean Down give about 17 TWh per year.

Ed]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195652#Comment_195652 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195652#Comment_195652 Fri, 07 Feb 2014 20:27:38 +0000 Seret 2 lagoon in the Bristol Channel you could get 22MW to play with.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195653#Comment_195653 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195653#Comment_195653 Fri, 07 Feb 2014 20:51:45 +0000 barney
1W = 1Mm/s

1m3 water weighs 1000kg or approx. 10kN.

1km2 water 2m high weighs 1000 x 1000 x 2 x 10kN = 20GN

Average head is 1m so stored energy is 20GJ

The tidal cycle is 11hr = 40 000s.

The average power is 20 exp 9 /40 000 = 500 kJ/s = 500kW.

So that 1km at say 10m head would only give you 5MW ?

Or have I got my sums wrong

Regards

Barney]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195654#Comment_195654 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195654#Comment_195654 Fri, 07 Feb 2014 21:07:18 +0000 SteamyTea
Power = Watts
m = mass flow rate (kg/(litre.s))
g = gravity (9.81 m/s^2)
h = head height (m)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195655#Comment_195655 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195655#Comment_195655 Fri, 07 Feb 2014 21:12:18 +0000 barney
Regards

Barney]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195656#Comment_195656 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195656#Comment_195656 Fri, 07 Feb 2014 21:18:20 +0000 Seret
E = 0.5Aρgh²

Where E = energy, A = area in sq m, ρ = density (approx 1025kg m^-3 for seawater), g = gravity, h = tidal range in m.

Since the tide cycles twice per day you double that, then divide by 86400s per day to get the average power in watts. That's a bit of an artificial figure though, since the actual power output is more like a chopped sine wave. Obviously turbine efficiency comes into it too, but modern turbogenerators are pretty efficient.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195658#Comment_195658 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195658#Comment_195658 Fri, 07 Feb 2014 21:19:19 +0000 Ed Davies https://en.wikipedia.org/wiki/Rance_Tidal_Power_Station

“Its 24 turbines reach peak output at 240 megawatts and average 62 megawatts, … The power plant portion of the dam is 332.5 m (1,091 ft) long and the tidal basin measures 22.5 km2 (9 sq mi).”

So 2.75 MW/km² on average.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195660#Comment_195660 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195660#Comment_195660 Fri, 07 Feb 2014 21:28:54 +0000 Ed Davies https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195661#Comment_195661 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195661#Comment_195661 Fri, 07 Feb 2014 21:30:56 +0000 barney
If we take Rance as an example, then 330 km2

Regards

Barney]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195662#Comment_195662 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195662#Comment_195662 Fri, 07 Feb 2014 21:48:11 +0000 SteamyTea 22.5 km^2 x 16.13 = 363 km^2

Gravity is very weak really. RE is very diffused.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195683#Comment_195683 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195683#Comment_195683 Sat, 08 Feb 2014 11:31:13 +0000 HalcyonRichard
Richard]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195686#Comment_195686 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195686#Comment_195686 Sat, 08 Feb 2014 11:42:17 +0000 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195713#Comment_195713 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=11724&Focus=195713#Comment_195713 Sat, 08 Feb 2014 22:07:24 +0000 atomicbisf
Brean Down to Lavernock, the focus of most of the proposals gives about 17 TWh/year.

It's a little difficult to compare with a fossil fuel power station as the output will not be constant but dependent on the tide. On the other hand, many fossil fuel plants (especially gas) do not run constantly either, but are modulated to meet demand.

But if you average out 17 TWh/year it would be 1940 MW.

Ed]]>