Huge world-first man-made tidal lagoon could power over 155,000 homes


August 18, 2014

Tidal Lagoon Swansea Bay would be the world’s first man-made energy-generating lagoon

Tidal Lagoon Swansea Bay would be the world’s first man-made energy-generating lagoon

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Energy trade association RenewableUK calls the UK "the undisputed global leader in marine energy." If plans for a tidal lagoon in Swansea Bay go ahead, that claim will be reinforced. Tidal Lagoon Swansea Bay would be the world’s first man-made energy-generating lagoon and could power over 155,000 homes.

Renewable energy is, of course, an area of huge importance and growth. A 2011 study by researchers at University of California-Davis and Stanford University suggests that the world could be powered completely by clean energy within 20-40 years.

Of the renewable options available, tidal is particularly intriguing. Renewable UK says wave and tidal energy could produce around 20 percent of the UK’s current electricity needs, and that the ongoing reduction in its technology costs will make it increasingly viable from a commercial perspective.

Swansea Bay has a high tidal range of up to 10.5 m (34 ft), making it an ideal location for tidal power generation. The proposal would see a 9.5 km (6 mi) lagoon wall constructed, halfway round which would be a 550 m (1,804 ft) turbine housing. The turbine housing would provide a means of allowing water to flow in and out of the lagoon as the tide rises and falls. Up to 26 turbines would be contained in the housing and would be driven with the flow of water in and out of the lagoon.

The Tidal Lagoon (Swansea Bay) development group says the lagoon would provide an energy production capacity of 320 MW and would provide sustainable and predictable electricity for 120 years of operation. In addition to generating electricity, the lagoon would provide opportunities for arts, culture, education, recreation and conservation activities.

Naturally, watersports such as sailing and rowing would be possible in the lagoon, along with cycling and running around the lagoon wall itself. A visitor center will provide a place to learn about tidal power and the construction of the lagoon, whilst a community marine farm would be created in the shallows of the lagoon. It is thought that the lagoon would also help to stimulate local regeneration and the creation of jobs.

The lagoon has been accepted for consideration as a Nationally Significant Infrastructure Project. Planning and marine license decisions are expected in early 2015.

The video below provides an introduction to the project.

Source: Tidal Lagoon Swansea Bay

About the Author
Stu Robarts Stu is a tech writer based in Liverpool, UK. He has previously worked on global digital estate management at Amaze and headed up digital strategy for FACT (Foundation for Art and Creative Technology). He likes cups of tea, bacon sandwiches and RSS feeds. All articles by Stu Robarts

I wonder when they'll come to the realization that these motive mean are just a mean to the ends of electric induction. Surely there are wiser methods of freeing up electrons than magnetic force through motion. I mean, at the nano scale where minute forces are near constant or simply some form of catalyst to free the electrons without motion.. Essentially one is freeing up electrons from the surrounding air, are there no reprocussions to such a syphoning? I just see the motive method so last century.. I'm not gonna throw out answers, but the least I can do is provide questions.


It looks like it should work but it is going to change the beach and near shore environment.


@ BT Provide a theory on how to do it or you are just spouting nonsense.


The one thing they all conveniently forget to tell you is that they need a standby power station ready to roll if a constant power output is needed.

The tide has two slack periods a day, periods when no electricity can be generated because the water is almost stationary. In fact if you plot the generated output of such schemes you get a square wave like form - from nothing, then a rise which falls back to nothing repeated twice a day. Absolutely no good for base load, in fact not much good for any real load without the power station backup.


Great inspiration and if it is cheaper than a nuclear site it has everything going for it. The winning idea here is that the head of water created by the tide could be used as a massive battery to store the power and release it when required. Also the leisure WinWin is fantastic you can't water ski, wind surf or swim inside a nuclear reactor. You could also provide a sailing marina or a safe sailing area to build up a tourism attraction. Let's invest in this now.

Martin Rayner

Huge world-first man-made tidal lagoon could power over 155,000 homes

Financially, how would that solution work as compared to a nuclear power plant?

Also, will it be able to provide the same amount of energy 24/7, and if not, what's the backup plan (which, obviously, can't be a fossil-fueled power plant)?

A 2011 study by researchers at University of California-Davis and Stanford University suggests that the world could be powered completely by clean energy within 20-40 years.

I guess "energy" here means "electricity": How likely will we have electric trucks, cargo ships and airliners in 20-40 years?


Harnessing tidal forces, will affect the rate the moon's orbit, right?

Jerry Reyes

It looks nice and all, but like people have pointed out, it's only effective at certain times, and other times it sits idle. Id' be a little more in favor of it if they revealed some new fangled battery tech that could store the power so it could be used in a controlled manner at peak load times.

Where I live (South Dakota) 65% of our electricity is from renewables.

Derek Howe

Assuming that you can control the release of water from the lagoon doesn't this mean that you could avoid a 'slack period'. It would work like any other hydro electric project where the volume of water in the lagoon is effectively a store of energy. If you had a smaller pond/lagoon that you didn't fill initially, but filled during the slack period. After the tide started to move again you could allow both ponds to drain. Am I missing something (apart from a cost benefit analysis)? Presumably yes.

Wesley Dart

I suggest you all read this:

Its one of 6 planned tidal lagoons for the UK, which will produce energy at a similar cost to new nuclear power plants, and a lot cheaper than the daft windmills they have stuck all around our coast. If all 6 come into operation it would supply approx 8% of the UKs annual electricity needs.

and more info from a detailed report:

"Of course a tidal lagoon does not generate electricity ‘baseload’, and other capacity will be required to provide electricity when the tide is turning. However the requirement for this will be known in advance and so its provision can be planned and optimised in advance.

Because high and low tides occur at different times around the coastline, then a portfolio of appropriately - sited tidal lagoons would have a much smoother generation profile than a single lagoon, thus reducing the requirement for generation from other sources."


Ocean is huge and reliable source of energy so I am happy that people start to see it. I am working in energy business and believe me producing and distributing energy is enormous effort. Anyway, keep a good work. We need renewable power sources. Today turbogenerators operates at 99% efficiency but turbines that e.g. gas or steam have only 40%. In my understanding if we run turbine with tidal force we get close to this 99% in contrary to gas or coal power plants with only max of 65%.


It will NOT be the first man-made tidal lagoon, there is one in Woodbridge, Suffolk, [one of two in the UK] that powers a tidal mill, that is on a site that has been used for such since 1170. It produces mechanical energy, rather than electrical energy, but it is still energy, and it still grinds out flour. See;

Also I'm sure that Holland has man made lagoons that also generate power.


Long overdue. Tidal power is consistent and will remain so until the moon disappears. That there are 2 slack periods each day is of course a glitch but if there are many of these projects around the Island we live on and they are connected to a national grid we will have a constant supply of electricity that really is clean and green. It beggars belief that wind energy has been the focus of governments for so long when as an Island nation we are surrounded by the greatest harvest-able power on earth,the tides. I could be a sceptic and suggest that there are politicians who stand to make considerable financial gains from supporting wind power but of course I have no proof of that.


Nice idea - tidal power is greatly under used. It gives a predictable output and if it doesn't, then we have more serious things to worry about!

Not being continuous doesn't matter, its just part of a mix, and if there was enough lagoon systems along the coastline then it could be virtually a continuous output from them (High water time varies along the coast).

Tidal is one of the most reliable and predictable of all the renewals its only disadvantage is surviving winter storms etc. But otherwise go for it!

Brian M

@ ivan4 By controlling the the rate of flow into and out of the lagoons and providing separate holding pools the periods of tidal slack become a non-issue.


If we can now give thorium nuclear reactors, which are load-following and 'walk away safe', a kick start, we won't need to worry about slack tides and associated low power generation.

It would greatly help the renewables cause if we can have more of these so that we can do away with all those wind turbines that annoy people so much - me included - and in so doing turn people off the whole idea of removing our dependence of fossil fuels.

Mel Tisdale

I hope this scheme gets the go-ahead, because it is benign, environmentally, compared with nuclear power.

As several people have pointed out, it is the best form of energy storage, because it can be released at a convenient time (depending on tides, which are different every day) Many tides will probably coincide with peak usage, or release can be shifted to suit requirements within several hours. Obviously incoming tides must be used as they happen.

This really is the best form of free energy, as it is totally predictable compared with wind and solar. Of course any form of renewable energy is worth having, except I remember reading last year that a wind farm was paid £2 million for electricity which it generated, but unfortunately was not required by the National Grid. The taxpayer had to cough up for this.

I've just had a thought: why not have a double row of turbines? Would this work? It would be a double lagoon system.


For me the bottom line is... Is it clean? Are there other benefits? Is the cost of the electricity better as good as other sources? Will it be economically viable to the investors, showing a good return and therefor encouraging further tidal power stations?

I do have reservations when the company doesn't worry about the smaller details of some of the things quoted in the video... 1. "16 MW/h" - this does not make sense and any technical person should know this. A MW is a MJ/s, which already has the time included in the unit. 2. "11.5 km squared" means 132.5 km2. What they should say is "11.5 square km", which is an area of 3.4 km by 3.4 km. Yes, it does matter because lives have been lost over people who are sloppy with units.

I hope it goes ahead, even though I'd rather see one across the Severn River.

Mark Windsor

This scheme or one similar has been talked about for at least 30 years.If it takes 20 years to be approved and built I won't be around to seeit.


There are passive and active storage choices, some new, some still emerging. The point is to get going on any given choice where each is most suited. At Niagara Falls, NY there is a giant lagoon that is filled at night and run down during the day. Effectively, Niagara Falls is turned off at about 11:00pm to fill the NY side lagoon and then during the day the Falls run full bore for the visitors. Electricity is produced continually from turbines on the NY and Ontario side and fed to the NY & Ontario grids. One of the emerging pieces needed to transform the grid is local storage, battery storage of various kinds are slowly evolving. At some not too distant time we will look back and somehow it will seem obvious. Until then ChillLax, things will get better.



Sorry but there is no combination of lagoons and pools that will provide anything like the output you may get at full tide.

The only way you could do it would be by taking a lot of the power generated and pump the water to a much higher level for storage. There is also a problem with doing that - where are you going to store enough water to get hydro power for two hours twice a day.

Another thing, have they calculated the cost of dredging the lagoon and included it in their running costs?


I agree with the the others as far as just build 21st century generation nuclear power plants. They are safe, cannot go critical, produce very very little in waste, do not even use water so is not a ground water contaminant risk.

With these tidal pools and wind mills and solar arrays, you are visual pollution, altering natural habitats, blocking vistas, etc.

Rann Xeroxx

@ StWils About 70% during the day.

@ ivan4 Ten hours of harvesting energy from a small difference in water level but you need a high drop for the next two hours? You need three retention ponds. The smaller two each equal to about 25% the large ones capacity.


The system depicted stops producing around half tide not at slack water –as it is working on head difference not tidal flow rate. At either slack water there should be maximum head difference between the lagoon and the ocean. However there is a way around such intermittent generation from tidal systems. Some years ago I read about a tidal scheme (in France, as I recall). I thought it had been built but it may have only been a proposal. It had two lagoons with the turbines generating power between them. Each lagoon had flood-gates (giant check valves) connecting them to the ocean. Those for one lagoon only let water into that lagoon (so it was full by the time the tide was high) while the other set for the other lagoon only let water out. Thus it was emptied by the time the tide was low. The power turbines between the two would then operate on the difference between the two reservoirs independently of the tide.

Lindsey Roke

Interesting concept, I wonder though if they have completely worked out the building costs, environmental issues, and the real average MW capacity factor. There is the Rance Tidal Power Station, located on the estuary of the Rance River in Brittany, which has been in full operation since 1967. It has 24 turbines, with a peak output of 240 MW, but it only averages 62 MW, which gives a capacity factor of 26%. So the Tidal Lagoon Swansea Bay might claim to have a peak output of 320 MW, but if Rance is anything to go by, it's not going to get anywhere near this in normal operation.


@ Lindsey Roke How much head difference you needs depends on how you are trying to harvest the energy.


It should help fill the gaps in the wind powered supply anyway


Lunar power added to solar power. Slick.


Hello, I think is different energy than power, energy is measure in joules, and power in watts, then it isn't a measure of energy "320 MW".

I think that man-made tidal lagoon energy will be less than 3 millions of megajoules, more or less the energy of a hundred thousand litres of gasoline, then it is a very ambitious project, but insufficient for 155,000 homes, I think. Bye.

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