Rance Tidal Power Station, France

Background to the Rance Tidal Power Station

After a construction phase lasting five years, the Rance Tidal Power Station was opened on the 26th November 1966. This was the first power station to take advantage of tidal water flow to produce electricity (tidal energy). In order to be able to construct the structure across the estuary, two dams had to be built to block the Rance river during the first two years of the construction phase to ensure that the estuary was completely drained.

The reason that the Rance River estuary was chosen was due to its large tidal range; it actually has highest tidal range in France. It has an average tidal range of 8m between low and high tide, while the spring and neap range can be as big as 13.5m.

Rance Tidal Power Station and the Tidal Flow

When the tide is coming in, the water on the sea side of the barrage is higher than the estuary side; therefore water will flow from the sea side through the turbine into the estuary. When the tide is going out, the exact opposite occurs. As such, the turbines that were installed in the Rance Power Station have the capability to produce power in either direction.

The Rance Barrage is 750m long and 13m high, while the actual power generating portion of it is 330m long. This section houses 24 Bulb electricity turbines each rated at 10MW so the maximum capacity of the power station is 240MW. In practice the amount of power it actually produces is about 96MW, supplying approximately 600GWh per year to the grid, which would power approximately 130,000 houses a year

One of the major drawbacks about tidal energy is that it is not a constant source of electricity. There are two tides a day, when the tidal range is at is maximum, and the generating capacity will be at it’s maximum, however there are times when the water level on either side will pretty much be equal, so it will produce no power.

The advantage of tidal energy and therefore the power plant at Rance, is that the tides are totally predictable, so you can very easily factor this into the energy mix, while other intermittent renewable energy sources such as solar PV and wind farms are a lot less predictable.

Rance Power Station Cost

The Rance Power plant was expensive to build in its day and took about 20 years to actually pay for itself. This is one of the major reasons the proposed £30bn Severn Barrage has not gone ahead, it is simply too expensive to undertake this kind of construction challenge in these tough economical times. However the project is being looked at once again to see if it can be constructed at a lower cost.

Since the power plant was constructed though in 1965, it has produced approximately 27,600GWh of electricity. At today’s prices, that quantity of electricity would cost £3.30bn.

Rance Tidal Power Station Environmental Assessment

Since the tidal barrage construction needed to drain the estuary in the initial years after the construction was completed, there were severe impacts to the local environment; however 10 years later it was considered that the Rance estuary once again had a rich diversity of aquatic life.

The sluice gates and the lock (built to allow boats to get through the barrage) allow a fairly easy transition from one side to the other for all aquatic animals, so this did not have any real affect on species there either. The one impact it did have was that the mud flats were severely diminished so birds that used the mud flats as a hunting ground had to adapt or move elsewhere to feed.

Rance Tidal Power Station Final Assessment

Upon reflection it must be recognised that building the Rance Power Plant was quite the engineering feet, and one that perhaps in the Western world will not be reproduced, not even with new tidal energy solutions. The fact it produces plentiful, 100% clean electricity 46 years after construction and has become a tourist attraction in its own right has proved why it was such a sensible project to start in the first place.

    My hope for Tidal energy!

    March 15, 2013

New Tidal Energy Projects

In late February, I came across the news that a £70m tidal project in Anglesey has been given the final go-ahead. I think this is fantastic news, since it is one of the few large-scale tidal projects that has actually received funding (I am still hopeful in time the Severn Estuary will have a tidal barrier installed – but more on why I think that is a great idea can be found here).

The plan is that Marine Current Turbines (owned by Siemens) will position five 2MW tidal stream turbines between Skerries and Carmel Head. Combined, these turbines will produce enough electricity to supply 10,000 homes. I know this is not the millions of homes that a nuclear power plant can power, but we need to start somewhere.

Anyway, what was interesting about this was that I was talking to a friend of mine who goes to Holyhead most weekends and has done since he was little and he said there was uproar in the local community over these proposed turbines.

‘Those bloody turbines everywhere – ruin the beauty of the place’

Educating the masses on Renewables!

Now, he is my friend so I certainly won’t name and shame him, but these turbines are actually under the water, so unless he happens to be swimming in close proximity, the view will only be dampened by 5 buoys that show the position of the turbines under the water to help boats navigate.

I think this is part of the problem, there are people that hate renewables full-stop. I appreciate that and there is nothing I can really do about it, but this guy is full of praise for what we are trying to do here at TheGreenAge and he helps spread the word for renewables, he just seems unwilling to accept them if they could potentially sit on his doorstep.

Tidal energy has a great deal of potential as a renewable energy source, since the electricity generation is more predictable because we know when the tides run. In addition these submerged turbines don’t have the same visual impact of wind turbines. The UK also has enormous potential tidal resource; a recent report by the crown estate stated that tidal energy could provide a maximum capacity of 91GW of electricity (approximately 216TWh per year). Maximum capacity in the UK is currently about 65GW, and the total electricity used in 2011 was 374TWh.

I think this shows that we still have a hell of a long way to go to educating the general public about renewables. We need to get behind these new innovative technologies, because one day we really could become reliant on them for all our energy needs.

For more information on Tidal energy, including case studies – please visit our Tidal Energy section.

Author: James Alcock





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      The Severn Barrage – Might It Finally Happen?!

      August 23, 2012

    I heard some really good news this week that David Cameron has asked for a re-examination of the Severn Barrage business case. This ambitious construction proposal was killed off as a project back in 2010 due to the environmental concerns and soaring costs, but it now appears that it is back on the radar.

    First a bit of background though – the Severn Estuary has a tidal range of 14m, the second biggest in the world, making it ideally suited to tidal energy. The idea of using the Estuary to create power was first mooted in 1849 by Thomas Fulljames, but it was not until 1971, when Dr Tom Shaw suggested building the barrage to span the entire length of the estuary, from the Northern Somerset coast up to Lavernock Point in Wales. This proposal was also shot down in the early 70’s due to an abundance of cheap oil making it uneconomical. Over the following years the business case was continually revisited however the soaring prices of the proposed project have always made it unattractive.

    So fast-forward to 2012 and what has changed? Well we are in the middle of a massive recession, and the need to create jobs via large infrastructure projects may hold the key to our recovery. The theory is that the proposed Severn Barrage, at a potential cost of £30bn, could be just the type of infrastructure project required to kick-start the economy.

    The plan would be to fund the barrage through a consortium of investors rather than through public funding. Although backing from the Government would be absolutely key, as for the project to be economically viable the subsidies available for renewables would need to be available.

    Its construction would be the biggest infrastructure project since the channel tunnel, with the potential to create 20,000 new construction jobs and 1000s of operational  jobs in the local area when it gets completed.

    The UK is also facing an uncertain energy future, with issues regarding energy security and our planned nuclear plans due for decommissioning before the end of the decade.  The Severn barrage has the potential to create 5% of the UK’s energy from a clean, predictable, renewable source, with an installed capacity of 8.64GW, producing about 17TWh of electricity per year. Based on an average home using 4800kWh a year, the barrage would provide enough electricity for approximately 3,000,000 homes

    By getting such a large proportion of our energy from this 100% renewable energy source, it would also help the UK to hit its emission reduction targets. Also tides are more predictable unlike the sun shining for solar power plants and the wind blowing for wind farms, making this energy source less intermittent.

    Opposition to the barrage is still widespread though, due to the Estuary’s unique ecology. The RSPB is particularly against the barrage, as its presence would disrupt the feeding ground of over 85,000 birds, but there are other concerns that it would prevent the easy passage of ships moving up and down the Severn (although the Rance Tidal Power Station in France has locks within its barrage to allow easy passage, so I presume these would be present if the project does go ahead).

    My personal feelings are that the Severn barrage is a great idea particularly if this can be funded privately. I know there will be a significant impact on the local environment, but I think the potential for an abundance of clean renewable energy especially at this time where at any moment any of the electricity that we import as a country could be at risk. Creating more energy supplies in the UK by using our unique topography has to be good for our country in terms of enhancing energy security and safeguarding highly skilled jobs in the construction & engineering sectors.


    In January 2013, Peter Hain announced that the Severn Barrage could get parliamentary approval by the end of the year, since it has been rethought so there is no threat to fish or birdlife. If approved it could be completed by 2024, helping to supply 5% of the UK’s energy demands. In addition it is thought the new proposal will only be comprised of private funding.

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