Tidal Lagoons

[Bay City]

How Lagoons Work

There are a number of them at various states of water levels. There will always be power generated. Think of one large dam wall in a circle in a shallow sea, split it into three sections. The centre section could be 30 foot below the outer two and the high tide level, and fill up via the other two or the high tide.

It is a matter of having the lagoons filling and emptying at different times to ensure full power production 24/7. A test lagoon is being suggested at Swansea in South Wales.

This is different to tidal only at La Rance, France. La Rance is just one power station. It only generates when the tide is running one-way. It is quite old now - 1966. Pioneering it is.

Political Spite Makes Matters Worse

Hard nosed cost/benefit eliminated the British coal industry (or more political spite by Thatcher hating miners). Middle Eastern oil was buttons to buy and the North Sea was full of cheap gas. Mrs Thatcher was told to reserve the gas for primarily domestic use and not use it to generate electricity - use the masses of coal we have under the country to only generate electricity. She never. The coal industry disappeared with amazing stocks still under our feet. The North Sea is running out of oil and gas.

Fuel Poverty is a major Problem

Domestic gas prices went through the roof because of world market conditions - the Uks gas is mainly imported. Fuel poverty is now a major problem.

Long Term Political View is Important

We are now are semi-dependent on Russian gas as we used a lot of our own reserves needlessly. Russia refused to supply gas to the Ukraine a few years ago, so alarm bells rang. We need stable fuel supplies. We get oil and gas from the politically unstable Middle East and Russia - which is a political concern over cost/benefit. They have to look at the long term and stability, not short term gains of utility companies. Then there is the important eco angle too. Tidal lagoons are both the long-term practical answer and politically acceptable.

25 Year Project

It will take 25 years. However benefits will come quicker than expected.

• The electricity will be introduced in phases,
• Knock-on effect fresh water reservoirs from rock excavations to combat water shortages, bridges, etc, by rock excavations.
• Increased insulation levels in buildings at the same would reduce oil, coal and gas dependency rather quicker than expected.
• Coal, gas and nuclear stations can be decommissioned and any planned costs in introducing nuclear stations will off-set the lagoons building costs.
• Such a scheme would bring zero unemployment, saving on public social benefits over 25 years.
• There is the comfort of not being under the reliance of foreign countries for energy, and being over-friendly with countries you would rather not be.
• Savings on military as the world will be a more peaceful place - oil has created wars.

The UK over 25 years can easily construct and afford such a scheme. Advances in rock cutting & transporting machines and methods would ensue. The technology and design and build can be exported elsewhere for others too.

Unprecedented Project

To meet 100% of Britain and Ireland's need for energy, this is clearly possible and mostly involves hauling rock from mountains and valleys to the sea on an unprecedented scale.

• The British Isles geography is the best in the world for such an undertaking with its high tidal rises and falls.
• It involves moving about 2,500 million tons of rock to the Irish Sea
• Tidal lagoons created out of about 20% of the Irish Sea
• 100% of Britain and Ireland's electricity needs met.

The numbers are staggering but possible:

• A heavy train can move perhaps 500 plus tons of rock
• About 4 or 5 million train loads are needed
• The UKs waste can be dumped into the lagoon walls while under construction, saving on landfill and re-cycling costs.
• It would take maybe 30 railways to haul rock from say 30 large quarries over 25 years

There Are Many Knock-On Benefits

• The insides of hills and mountains can be cut out for the rock and lakes constructed top and bottom to make provision for instant use peak time hydro stations for half time energy peaks in major football games on TV.
• New valleys can be created
• New lakes
• Fresh water reservoirs
• Rail and road tunnels through mountains
• Rail and road bridges across the Irish Sea
• Deep water ship canals can be cut inland, reducing rail and road transport of goods - good result for quarried rock.
• Some lagoons can be supertanker harbour/terminals, keeping these massive pollution risk vessels away from the shore.
• The lagoon walls built can also be bridges
• The lagoons can also be anti tidal surge barriers. Empty the lagoons at low tide when a surge is expected and allow the lagoons to fill taking excess water - London will go under if nothing is done.
• Fish can be farmed inside the lagoons preventing foreign trawlers overfishing and all fish goes to the UK.

Fuel Poverty & Pollution Eliminated

Fuel poverty and pollution will be a thing of the past.

Cheap Fast Transport

The EU has a transport dept that looks at transport for the EU 20, 30, 40 years hence. The aim is super fast intercity trains between all major cities/centres. One idea is a tunnel between Liverpool and Dublin. As Holyhead is the halfway point between the two cities that appears a dumb suggestion and a loooooong expensive tunnel. But a tunnel from Ireland to North Wales at the shortest point and then a fast link to Liverpool, Manchester, Birmingham, London is feasible.

However, damming in the Irish Sea to make lagoons to produce all the power for the UK and Ireland would create maybe two land links anyhow and maybe one to the Isle of Man. This gives high speed transport bridges. Super fast Maglev trains between major centres and to Ireland become feasible as running cost are low.

All cars can be electric, and the auto industry is currently moving that way.

Overall the lagoon project is well worth looking much deeper into, and clearly looks highly feasible when all points are viewed.

[LABlue]

I have no problem with how the information on this post is presented - some good info

Thanks for posting

... and I am not being sarcastic

[thecityofgold]

I liked how it had nothing to do with architecture/skyscrapers/Liverpool but did manage to get trains in at the end.

[Bay City]

Originally Posted by thecityofgold

I liked how it had nothing to do with architecture/skyscrapers/Liverpool but did manage to get trains in at the end.

What didn't you understand?

[Tony Sebo]

Good idea Bay City.

[HollyBlack]

Originally Posted by Bay City

How Lagoons Work
...
Tidal lagoons are both the long-term practical answer and politically acceptable.
25 Year Project....

But THIS GUY:
Professor Richard Burrows
Department of Engineering
The University of Liverpool
PROPOSES SUBSTANTIALLY THE OPPOSITE (Barrages and free stream turbines)

Originally Posted by http://www.joulecentre.org/research/grants_tapping_the_tidal_power.htm

The most attractive locations for harnessing tidal power are estuaries with a high tidal range for barrages and other areas with large tidal currents (e.g. straits and headlands) for free-standing tidal stream turbines. ...

That is to say "just about every kind of water power other than tidal lagoons".

Like free stream turbines are going to survive the amount of flotsam in 21st century European waters for any number of years.

His barrage proposals will be environmental disasters and free stream turbine proposals will be short-lived engineering and/or economic disasters, and both will provide relatively minor spin-off benefits and fail to scale sufficiently.

And he has had the money to prove it by now
" Tapping the Tidal Power Potential of the Eastern Irish Sea. - Grant Awarded £288601 ... "
http://www.joulecentre.org/research/...idal_power.htm

[LABlue]

Originally Posted by thecityofgold

I liked how it had nothing to do with architecture/skyscrapers/Liverpool but did manage to get trains in at the end.

yes - I hadnt really focused on that that but I was prepared to go with it as there are examples of how large construction projects have spurred railway development.

I would like to redress the balance though and suggest that we use "Choo Choo" at the end of posts with nebulous railway references in the same way that "Ding Ding" seems to sneak in to any tram references.

Take your point though maybe this thread is better on the Beacon

[Bay City]

If lagoons get the go ahead, then this affects Liverpool in a big way. With the 4th highest tide in the world and very strong currents, the Mersey was bound to have some sort of water electricity generation. Lagoons may leave the river alone.

[Martin S]

I thought of having a go at looking how a tidal lagoon system might work:



I envisage there being two lagoons with a dam in between them. One would be the high tide lagoon and the other the low tide. The dam would contain turbines that would be in constant operation due to the head of water between the two lagoons.

The water level in the two lagoons would be controlled by lock type gates opened by water pressure in one direction but kept shut by water pressure in the other.

At high tide, the high tide lagoon gates would be opened by water pressure and the lagoon would fill up to its maximum level. As the tide receded, the gates would close and water would flow into the low tide lagoon. At low tide, the accumulated water in the low tide lagoon would open the gates and the level of the lagoon would drop to its minimum level.

The amount of power generated would be directly proportional to the difference in level between the two lagoons and to the number of turbines. Naturally, as water flowed from the high tide lagoon to the low tide, the level of the former would fall and the latter rise and, so to maintain a good head of water, the two lagoons would have to be of quite large area to ensure that run-off between the lagoons was not sufficient to reduce the head significantly over the period between high and low tides.

Just my idea of how something like this would work. By the way, the energy source for this would ultimately be the rotation of the moon about the earth which causes the tides. So tidal lagoons would slow the moon in its orbit and bring it closer to the earth. Not by a great deal though.

[Martin S]

I'll have a go at calculating the size of these lagoons based on the idea that the generators would produce the same amount of power as the Hoover Dam, which produces around 2000MW using seventeen generators with an average head of water of 520' (158m.).

I understand that the tidal range in the Mersey is around 25' (7.6m) and I'm assuming that the average head between the two lagoons would be 90% of that - 6.8m.

As the amount of power that can be generated from water is directly proportional to its head, to obtain the same amount of power from a Liverpool Bay tidal lagoon as that from the Hoover Dam, 158/6.8 = 23 times the generating capacity would be needed and, consequently 23 x the flow rate.

The amount of water that goes through the turbines at Hoover Dam is 38m3 per second. Therefore, our tidal lagoon would have 23 x 38 = 874 m3 per second flowing from the high tide to the low tide lagoon.

This is where it begins to get complicated.

At high tide, the level of water in the high tide lagoon will be 7.6m above low tide level but the low tide lagoon will have been filling up at 874m3 per second since its gates were closed at low tide 6 hours before and, things will get worse over the following six hours as the low tide receives another 874m3 per second and the high tide loses the same amount. So, just prior to the low tide gates opening, the head will be at its minimum and will have been reduced by 3 x 874m3 per second over a period of six hours. that is 56.6 million cubic metres.

So, if we are going to only allow a 10% reduction in head (and, of course, ignoring other effects such as rainfall, leakage through walls or gates etc) then that 56.6 million cubic metres will need to only reduce the level of one lagoon by 0.76m. Which would require an area of 74 million square metres per lagoon that would require each to be 9.7km. in diameter (assuming them to be circular).

Does this make sense and am I making reasonable assumptions?

[LABlue]

I think your logic seems right Martin

I will try and take a run at looking at the calcs when I get chance. Good thing about hydropower calcs is that you dont need to be an electrcal engineer to do them they are just Newtonian physics. I will try and compare them with some of the low head hydro plants on the Colombia river if I can dig out the figures.

The only assumption that sticks out at me is the reduction in head at 10% I think this is low and a low head hydro turbine designed for this use should be able to accomodate more than that so that makes the lagoons smaller. I wonder how the Dubai palms compare in size?

[LABlue]

Originally Posted by Bay City

If lagoons get the go ahead, then this affects Liverpool in a big way. With the 4th highest tide in the world and very strong currents, the Mersey was bound to have some sort of water electricity generation. Lagoons may leave the river alone.

Its a natural and the environmental impact of the estuary has always been an issue. If they could move the facility into the Irish sea then that at least reduces that issue.

Another different type of barrier to overcome is that with deregulation in 1990 power generation facilities are the domain of the private sector. I am thinking this would have to be a very large public project so would require a policy change.

[Bay City]

The lagoon generators will not work like the traditional dam generators, which tend to operate on head (height), pressure. They act via linear flow more than anything - current, low head. High water volumes and low head (pressure). High water volums is a not a problem in open sea, it is in dams with a limited amount of stored water.

BTW, ships could sail through these lagoons.

[Bay City]

Originally Posted by LABlue

Its a natural and the environmental impact of the estuary has always been an issue. If they could move the facility into the Irish sea then that at least reduces that issue.

Until recently the river was dead. So, environmental impact can't be that great.

Damming in the river brings many benefits. The strong currents and high tidal rise is a problem in many areas. They would be virtually eliminated. vessels would have freer movement around the estuary.

Another different type of barrier to overcome is that with deregulation in 1990 power generation facilities are the domain of the private sector. I am thinking this would have to be a very large public project so would require a policy change.

That is easily done if the political motive is strong. If the calculations check put, then it would save the country in many ways.

[HollyBlack]

Originally Posted by Martin S

...
I envisage there being two lagoons with a dam in between them. One would be the high tide lagoon and the other the low tide. The dam would contain turbines that would be in constant operation due to the head of water between the two lagoons.
Just my idea of how something like this would work. By the way, the energy source for this would ultimately be the rotation of the moon about the earth which causes the tides. So tidal lagoons would slow the moon in its orbit and bring it closer to the earth. Not by a great deal though.

That is certainly a good way to arrange things if you were building a "peaker" plant. It is the way to calculate the maximum power output assuming the plant is kept substantially idle until the demand materialises at some arbitrary (otherwise inconvenient) worst-case moment in time (which a totally reasonable scenario).

No design with only two lagoons can operate continuously, you need at least three. And the 432MW Rhyl proposal has three of vaguely 5 to 10 square miles each.

However, your design is not how you would build a baseline power plant still less an opportunist generator. Long term (annual) average power would be greater if you ran the turbines between a lagoon and the sea (in both directions according to the state of the tide). But that would not give you peaker capability. Nonetheless it is good that the tides are extremely predicable. Also there is some (relatively minor) gain from the difference in tide times between North and South - with appropriate modeling many large scale lagoons could be sited to tend to cause North-South sea currents and so amplify those effects and so provide for diversity in state of tide constraints.

I want to be clear on that, a two-lagoon peaker design would give greatest maximum power, and that power would be available any time, on demand. But a whole new set of calculations is needed to calculate what is the best design for total annual energy output, and the average output would be less than the maximum output of the peaker design but more than the average output of the peaker design.

Nonetheless Martin your (peaker) calculations will be useful and necessary, they just won't be sufficient is all. It will be interesting to see how they stack up against the cited 20MW per square mile of the present 432MW proposal. And do forget the Spring Tide / Neap Tide phenomenon - that provides minima and maxima constraints of its own.

A good thing is that with spread sheet programs these days it becomes easy to insert multiple alternatives and have the computer calculate it every which way.

[HollyBlack]

Originally Posted by LABlue

... Another different type of barrier to overcome is that with deregulation in 1990 power generation facilities are the domain of the private sector. I am thinking this would have to be a very large public project so would require a policy change.

The way to deal with that is to write 100 year leases on tracts of the sea - with the rent to be paid as an amount expressed in kilowatt hours. The best answers are often not to convert everything into money

[LABlue]

Originally Posted by HollyBlack

The way to deal with that is to write 100 year leases on tracts of the sea - with the rent to be paid as an amount expressed in kilowatt hours. The best answers are often not to convert everything into money

Don't disagree - I am not familiar with the ownership rights to the seabed but I couldn't imagine any developer being given freehold and so they woudl have to obtain a lease.

My comments on the funding is more to do the size of the cost. I have no idea what the civils works would cost for these lagoons but the power developer industry had real funding challenges raising large sums of money before the current crisis and lenders are very leary about new technology. Thats why I could see them having to be developed as public power projects or at least with public backing to mitigate the development and operational risks. We are having to offer 20 year power offtake contracts to get wind and solar built (some of which can still not get financing -especially large solar) and they have a longer track record than lagoons.

Maybe its out there somewhere does anyone have any budget figures on the civil's costs of the 432MW scheme.

[LABlue]

Originally Posted by Bay City

The lagoon generators will not work like the traditional dam generators, which tend to operate on head (height), pressure. They act via linear flow more than anything - current, low head. High water volumes and low head (pressure). High water volums is a not a problem in open sea, it is in dams with a limited amount of stored water.

BTW, ships could sail through these lagoons.

Low head hydro is very common and a well proven technology so that's not a problem. The main difference is turbine design and the lack fo need for long penstocks to deliver the water to the turbine

There is a limitation on stored water (and so ultimately the amount of energy produced per tide) as it is a factor of the amount of water contained by the lagoon and the amount of water flow which is a factor the amount of head. The turbine size woudl be deisgned based on what type of output profile you want as well as the timing of the head produced.

You would need a lock system to accommodate ships passage which would be another added costs that these scheme could probably do without if possible.

[LABlue]

Originally Posted by Bay City

Until recently the river was dead. So, environmental impact can't be that great./quote]

If were talking about the Mersey there are mud banks that are regarded as majorly important (on an international scale) for bird migration. Theres an interesting report here:

http://www.severnestuary.net/sep/pdf.../36dwaston.pdf

Damming in the river brings many benefits. The strong currents and high tidal rise is a problem in many areas. They would be virtually eliminated. vessels would have freer movement around the estuary.

Depending on the location that could well be true but that would have to be balanced against the environmental impact and cost.

That is easily done if the political motive is strong. If the calculations check put, then it would save the country in many ways.

I would contend that having supporting calcs are only one factor in obtaining strong political motivation.

[LABlue]

Originally Posted by Bay City

Until recently the river was dead. So, environmental impact can't be that great.

Damming in the river brings many benefits. The strong currents and high tidal rise is a problem in many areas. They would be virtually eliminated. vessels would have freer movement around the estuary.

That is easily done if the political motive is strong. If the calculations check put, then it would save the country in many ways.

If were talking about the Mersey there are mud banks that are regarded as majorly important (on an international scale) for bird migration. Theres an interesting report here:

http://www.severnestuary.net/sep/pdf.../36dwaston.pdf


Depending on the location that could well be true but that would have to be balanced against the environmental impact and cost.


I would contend that having supporting calcs are only one factor in obtaining strong political motivation.