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Tidal lagoon touted as Somerset flooding solution

Energy-generating tidal lagoons could help reduce flooding in areas like the Somerset Levels, according to engineers studying the technology.

A proposed tidal lagoon at Bridgwater Bay in Somerset could generate up to 3.6GW of renewable electricity by passing sea water in and out through a series of turbines located in a 16km-long wall around the bay.

But such lagoons could also keep the high tide out when needed, preventing tidal flooding from storm surges and effectively lowering the sea level to allow water from river flooding to run off the land more quickly, according to Prof Roger Falconer of Cardiff University.

Speaking yesterday at a briefing organised by the Royal Academy of Engineering and the Science Media Centre, he said a tidal lagoon at Bridgwater Bay would make a ‘huge’ difference to the nearby Somerset Levels, which have been severely flooded in recent weeks.

‘In my view it would be an ideal solution in the Somerset Levels,’ he told The Engineer. ‘The problem is they’ve got a horizontal water surface slope. [A lagoon] would allow us to drop the sea water level and therefore create a water surface slope.’

He added that dredging the area’s waterways – a key focus in the recent debate on flooding – would typically have a limited impact in the Levels because of the flatness of the land but that lowering the sea level with a lagoon would make dredging far more effective.

Swansea-based Tidal Lagoon Power Ltd is ‘actively examining’ plans to build a lagoon at Bridgwater Bay after recently submitting a planning application for a 240MW lagoon in Swansea Bay, which would be the world’s first scheme of this kind.

Peter Kydd, director of strategic consulting at Parsons Brinckerhoff, which worked on a 2010 government study on tidal power generation in the Severn Estuary, said the added bonus of flood prevention might make tidal lagoons more attractive but that the business case would have to be based on electricity generation.

‘The advantage is that a lagoon would pay for itself in terms of energy generation whereas most flood defence schemes are based on the probability of a flood occurring, so the cost of avoided damage would be much higher,’ he told The Engineer.

‘But it’s very difficult to quantify multiple benefits … Part of the reason for that is the electricity sector is privatised and therefore generation schemes have to be able to raise money from consumers, whereas flood defence is paid for by taxpayers.’

He added that the £12bn to £18bn cost of the Bridgwater Bay lagoon, as estimated by the government study, made it unlikely that the scheme would be chosen primarily for its flood defence benefits.

‘But it’s not just about a pounds and pence logic, it’s also about hearts and minds. So if there was universal support for a scheme, no doubt that would be taken into consideration.’

Readers' comments (15)

  • All the money spent on Olympic stadiums, Millennium arenas, Wembley stadiums and the Canary Wharf development would have be better spent on digging a big hole somewhere down south and allowing it to fill with water so that in the rainy weather the water can be collected and used during the "hose-pipe ban" periods. This isn't rocket science and we don't live in a Third World country.

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  • Fred.....Not sure about a big hole
    in the South ,the natives would go incandescent . However your sentiment is not far off the mark . If the British thought as much about work as they do about sports and its facilities dear old UK would be in a better condition

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  • In a nutshell - "But it’s very difficult to quantify multiple benefits … Part of the reason for that is the electricity sector is privatised and therefore generation schemes have to be able to raise money from consumers, whereas flood defence is paid for by taxpayers."

    i.e. The government has abdicated responsibility for governance, and this idiocy is enshrined in EU legislation.

    The brainless ideologues tested the private sector's competence with Eurotunnel. It failed. They put all our eggs in the basket-case investment banks. They failed. Their dogma failed again with Railtrack. When will they ever learn?

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  • David, I agree.

    The private sector is good at managing the here and now and planning for risk into the near future.

    The private sector can only manage the mid term by building in huge contingncies for risk or fixing long term frameworks, thus making jobs terribly expensive.

    In my opinion the state must take responsibility for planning and financing large infrastructure projects spanning many years as only it has the "broad shoulders" and staying power. That's not to say the state should design, build or operate the things, the private sector is generally better at that but the two should work together delivering on eachothers strengths. Complemeting not competing.

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  • Yes Nathan - we sure do need a lot more co-operation for the common good, and competition between technologies is often a stumbling block for innovation and R&D. To my mind the 'elephant in the room' for all renewable developments is energy storage.

    There is no way I can test the estimate of 3.6GW peak that is claimed for the Bridgwater Bay lagoon. It used to be 1.36GW. If one compares it in size to the Severn Barrage at 8GW and the Swansea Bay project at 240MW, one can only surmise that they'll put a lot of turbines in the wall and run them for a shorter time on a higher head. That more 'peaky' generation is not ideal when you have no control over the time of the tide!

    The wind industry uses the same 'trick' - i.e. quote peak (nameplate) capacity and let everyone guess how many GWhs you'll actually get on average.

    Isn't it about time the renewables technologists grasped the energy storage nettle?

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  • The 'Hoover' dam on the Colorado river was built primarily for river flow control (flood prevention) reasons, not the fuel-free electricity generation it is understandably famous for.

    It seems there is a good analogy here.

    How about a referendum

    1) Less than £100bn: Bridgewater Bay, Severn Barrage and Swansea Bay schemes yielding fuel-free electricity and in at least on case flood prevention ( no water in your back yard)

    2) £100bn: HS2 for 1/2 an hour off a journey and a railway line (in your back yard)

    On politicains decison making track record the answer is a 'no drainer'

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  • Where did you get the £100bn figure for HS2 from? Maximum estimates are £50bn with rolling stock.

  • Well done Prof., must be engineering logic here - better way to spend public funds than eg. HS2. Regardless of the expected Power output, it will be green, have a quantifiable return, whilst helping to save the useful land resource of Somerset.

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  • Why not reclaim land at the lower levels but instead of housing plant lots of trees. If they flood it will not matter. The rest of the time they are helping the environment sucking up water and capturing carbon

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  • I would like to expand on my good idea/bad idea theme (2/2/14):-

    Thousands of generators under water or housed in 300-ton nacelles 100m above the waves - both bad ideas.

    Fracking + CCS, or any thermal-generated electricity, all bad ideas.

    HS2: Little economic merit. A bad way to spend £42bn at this time. What's the hurry? Running it on electricity with any CO2 emissions is a bad idea.

    "lowering the sea level would make dredging far more effective." - Well, obviously a good idea. How about a big drain pipe to bypass Bridgwater too? Lower the cost of future dredging? A single motor/generator turbine to extract a few MWhs from the flow most of the year and pump like hell when it rains too much.

    The Jubilee River looks like it was a bad idea, especially to those living downstream!

    @ Robert Baker. The devil is in the detail:-

    The Cardiff-Weston Barrage: Wrong location. 1,026 generators. No energy storage. Circa £30bn. A very bad idea. 18kms of wrong design.

    The Bridgwater lagoon: Pointless, if a sensible barrage is built from Minehead to Breaksea Point. Lagoon wall - 16 kms of wrong design. No energy storage. Circa £12bn. A bad idea.

    Swansea Bay Lagoon: Too small - a 9 km breakwater in the wrong place. 26 generators. A bad idea. An 11 km string of caissons would give six times 250 MW. No energy storage. It should have an umbilical link to a totally redesigned Atlantic Array.

    The Atlantic Array: 240 sea-bed fixed HAWT generators. Circa £4bn. Judged a technical failure AND uneconomic. A bad idea. Low c of g VAWTs, mounted on four-float wave energy converters, should pump water to Swansea Bay to share its storage and generators. Joined up thinking.

    Pelamis - not good. Seatricity - potentially much better (with energy storage):-

    The Minehead-Breaksea Point Barrage: 20 kms of energy storage caissons, with an umbilical attachment to floating wind/wave, sharing 40 generators @ say 200 MW. Circa £42bn. Fuel-free, secure, dispatchable electricity from here to eternity. Radical, disruptive innovation is key to the UK's manufacturing renaissance. There's a global market for the kit AND the IPR. What's not to like?

    Designed to last 200 years; the plaque on the barrier bears the inscription: "Here the tide is ruled, by the wind, the moon and us." Oosterscheldekering. WANTED, in 2015 - intelligent politicians with guts and vision.

    "No one really knows what will happen when renewables reach 35% of the market, as government policy requires in 2020, let alone if they reach the national target of 80% in 2050."

    Nonsense. Technically, WE CAN determine what will happen if we apply visionary engineering forethought - energy storage.

    Politically, WE CAN decide what will happen if we learn these lessons from history:-

    "Over the past 30 years European governments have been trying to deregulate energy markets, privatising state-owned companies and splitting electricity generation from transmission and distribution. The aims were to increase competition, boost efficiency and cut prices."

    Patently a bad idea, as proven by the failure of "competition" to drive innovation, OR boost efficiency, OR cut prices. I rest my case.

    To the Editors: Sorry I can't make it any more concise. This subject matter is too complex for an understanding to be conveyed within an 'elevator pitch'!

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  • Unreserved apology rgearding the HS2 estimate - I thought I had seen that figure somewhere.

    It seems that storage is the major hurdle for cyclic clean energy generation, apart from the Minehead-Breaksea Point Barrage proposal.

    Coud the Minehead-Breaksea Point Barrage storage approach be applied to the Bridgewater flood defence scheme?

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