Power from the oceans: Blue energy

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After years in the doldrums, the quest to harvest energy from the oceans is gathering speed.

Several kilometres off the coast near Perth in Western Australia, hidden beneath the waves and out of sight of watchful boaters, three giant buoys will soon begin producing electricity as they bob to the rhythm of the Indian Ocean. At 11 metres wide and 5 metres tall, the squat orange floats look a bit like giant pumpkins. As waves pass by, the tethered buoys will drive hydraulic pumps on the sea bottom, converting the motion of the ocean into 720 kilowatts of electricity to power a nearby naval base.

Carnegie Wave Energy of North Fremantle, Australia, plans to have the system — the latest attempt at harvesting power from the sea — up and running by June. The pilot project will generate a lot of press, but veterans of the marine-energy field will watch warily to see how it fares. This industry has taken a slow road: none of the myriad devices designed thus far has proved its worth in the highly competitive energy market, and few have survived prolonged exposure to the harsh conditions in the sea. Despite an overall investment of around US$735 million over the past decade by a dozen leading companies, marine power from tide and waves has yet to take off. In fact, it remains the most expensive form of power on Earth.

But the outlook has brightened for those hoping to tap this source of energy. In the past few years, several major industrial leaders have acquired start-up companies that harvest energy from tides, the easiest type of marine power to capture. In March, three projects were approved for Canada's Bay of Fundy, home to some of the largest tides on the globe. The wave-energy industry, which is targeting a much larger but more elusive resource, has had a few setbacks, including a decision to scale back plans for an array off the coast of Oregon last month. But there is little doubt that both types of marine energy will eventually grow. Last year, the London-based consultancy Bloomberg New Energy Finance projected that up to 22 tidal projects and 17 wave projects generating more than one megawatt of electricity — enough to power around 250 homes — could be installed by 2020.

In theory, oceans could power the entire globe without adding any pollution to the atmosphere. And they could provide a more dependable source of electricity than the wind or sun. They are also geographically convenient: roughly 44% of the global population lives within 150 kilometres of the coastline.

Some nations have been using large, dam-like structures to block off inlets and draw power from tidal flow for decades, but the latest approaches are designed to be less intrusive. Although the potential environmental impacts are still under investigation, many researchers say that the sea could turn out to be an even more benign source of power than wind.

Indeed, energy experts envisage a day when the sea will deliver a significant amount of reliable carbon-free power to islands and burgeoning coastal cities around the world. “It has proved harder than people had expected at the start, but it has also proved possible,” says Neil Kermode, managing director of the European Marine Energy Centre, the leading test facility for wave- and tidal-energy devices in the Orkney Islands, UK. “We have shown that you can make electricity from moving sea water, and that's a huge step forwards.”

Shifting tides

Twice a day, some 350 million cubic metres of tidal water flows through a narrow strait into Strangford Lough — a small inlet southeast of Belfast, UK — and then back out to sea. With each trip, it passes a pair of 16-metre-long propellers attached to a central tower that is anchored to the floor of the channel. The force of the water, equivalent to a wind blowing at 555 kilometres per hour, spins the propellers at up to 15 revolutions per minute, generating 1.2 megawatts of electricity.

In addition to the traditional propeller, tidal-power companies have experimented with contraptions such as corkscrews, hydrofoils and underwater kites. The device used in Strangford Lough, however, is leading the way. Built by Marine Current Turbines in Bristol, UK, the design has generated more than 90% of the industry's power to date, according to the company.

The achievements attracted the interest of engineering giant Siemens in Munich, Germany, which took control of the company in 2012. Marine Current Turbines is now preparing to deploy its first array of five 2-megawatt machines — each costing roughly £9 million (US$15 million) — off the coast of Wales by 2016. As well as boosting the size of the machines, the company added a third blade to reduce vibrations and make the machines more durable, says chairman Kai Kölmel. But he cautions that progress is likely to be incremental. “I think some of the venture capitalists are disillusioned, but this is not a quick-buck industry,” he says. “The wind industry didn't start up rapidly either.”

Even with major companies such as Siemens entering the game, the biggest challenge remains attracting the money needed to do the engineering and build prototypes, says Christopher Sauer, chief executive of Ocean Renewable Power Company, based in Portland, Maine. Sauer's company has developed and deployed, albeit briefly, a unique device off the coast of Maine that looks a bit like the spinning blades of a combine harvester. The company is now working on a second-generation device that should be ready for deployment as early as 2015. “We're doing the best that we can with the money we have,” he says.

Waves of energy

The power of waves is vast, but developing machines that can reliably extract that energy and withstand the often-punishing environment represents a wholly different kind of challenge. Companies have explored designs ranging from swinging flaps to gyroscopic devices that convert the rocking of a ship into a circular motion to drive an onboard generator. Each has its advantages, but the idea behind Carnegie Wave Energy's bobbing buoys in Australia was to escape the rough battering of waves at the surface. The submersion has the added advantage of keeping the devices out of sight and avoiding the debates over aesthetics that have arisen with wind farms.

As the waves carry the buoys up and down, the sea-floor pumps circulate fluid through a closed loop that extends roughly 3 kilometres to an onshore generation facility (see 'Water works'). Operating like a bagpipe, the system accumulates pressure and then releases it gradually to generate a constant flow of electricity. Each of the three devices can generate up to 240 kilowatts of energy.

“This is obviously not a commercial project, but there's not a commercial wave-energy facility in the world at the moment,” says Carnegie's chief operating officer Greg Allen. Nonetheless, it represents progress, he says: each device generates three times more power than the version that was tested in the same waters in 2011. Allen says that the first commercial projects could come as early as 2018. To gain a toehold in the market, the company aims to compete with diesel-fired power generators on islands.

Written By: Jeff Tollefson
continue to source article at nature.com

18 COMMENTS

  1. @OP – Marine Current Turbines’ tidal-energy converter in Strangford Lough, UK, generates power with underwater blades that can be raised for maintenance.

    The Strangford Lough, turbines are a very early experiment. Many other projects have followed.

    There is a vast source of electricity to be harvested from tidal energy.

    I linked these articles on an earlier 2011 discussion;- http://old.richarddawkins.net/discussions/632627-harness-the-sea-national-geographic-june-2011-tidal-wave-power-generation

    http://ngm.nationalgeographic.com/2011/06/visions-now-next#/next/1

    http://ngm.nationalgeographic.com/2011/06/visions-now-next#/next

    There is also this prototype tidal turbine system in New York.

    http://energy.gov/articles/turbines-nyc-east-river-will-provide-power-9500-residents

    The Scottish company Atlantis Tidal Turbines http://atlantisresourcesltd.com/about-atlantis.html has projects off Orkney and a big project in India.

    The state of Gujarat in north western India is working actively to exploit its vast resources of wind, solar and tidal energy to establish an international hub for renewable power. – http://atlantisresourcesltd.com/projects/india.html

    • In reply to #1 by Alan4discussion:

      @OP – Marine Current Turbines’ tidal-energy converter in Strangford Lough, UK, generates power with underwater blades that can be raised for maintenance.

      The Strangford Lough, turbines are a very early experiment. Many other projects have followed.

      There is a vast source of electricity to be harv…

      You clearly know quite a lot about this subject, so I’d like to ask you if I’m right in thinking that the geological features of France are prone to flooding, making it difficult and dangerous for the French to extract coal, and that’s why they rely so heavily on nuclear power?

      • In reply to #3 by Stafford Gordon:
        >

        I’d like to ask you if I’m right in thinking that the geological features of France are prone to flooding, making it difficult and dangerous for the French to extract coal, and that’s why they rely so heavily on nuclear power?

        You are correct, that a lack of endemic carbon fuels has led France to develop nuclear and tidal energy.

        Nuclear power in France -Wiki

        As of 2012 France’s electricity price to household customers is the 7th cheapest amongst the 27 member European Union and the seventh-cheapest to industrial consumers, behind other nations which produce the majority of their electricity from hydroelectric and nuclear power plants such as Bulgaria, but substantially cheaper than Germany.[6] Drawing such a large percentage of overall electrical production from nuclear power is unique to France. This reliance has resulted in certain necessary deviations from the standard design and function of other nuclear power programs. For instance, in order to meet changing demand throughout the day, some plants must work as peaking power plant, whereas most nuclear plants in the world operate as base-load plants, and allow other fossil or hydro units to adjust to demand. Nuclear power in France has a total capacity factor of around 77%, which is low due to load following. However availability is around 84%, indicating excellent overall performance of the plants.

        However, some of these plants are old and have already had an extended life.

        • In reply to #4 by Alan4discussion:

          In reply to #3 by Stafford Gordon:

          I’d like to ask you if I’m right in thinking that the geological features of France are prone to flooding, making it difficult and dangerous for the French to extract coal, and that’s why they rely so heavily on nuclear power?

          You are correct, that a lack of ende…

          Thanks for the confirmation; believe it or not, I learnt about French coal mining from Zola’s Germinal.

          • In reply to #7 by Stafford Gordon:

            Thanks for the confirmation; believe it or not, I learnt about French coal mining from Zola’s Germinal.

            Great book! I read it as well and became engrossed in the whole series of books following the lives of the loosely connected cast of characters.

          • In reply to #9 by Nitya:

            In reply to #7 by Stafford Gordon:

            Thanks for the confirmation; believe it or not, I learnt about French coal mining from Zola’s Germinal.

            Great book! I read it as well and became engrossed in the whole series of books following the lives of the loosely connected cast of characters.

            Interesting; I played Souvarine in a stage adaptation.

  2. @OP – Some nations have been using large, dam-like structures to block off inlets and draw power from tidal flow for decades, but the latest approaches are designed to be less intrusive. Although the potential environmental impacts are still under investigation, many researchers say that the sea could turn out to be an even more benign source of power than wind.

    We should not forget this well proven tidal barrage generation system even if the UK government is dithering over plans.

    How France eclipsed the UK with Brittany tidal success story

    The UK may have turned its back on the Severn barrage but across the channel they have been harnessing tidal energy from the River Rance for more than 40 years – and it may yet point to a way forward for smaller-scale renewable projects.

    The sea has actually been harnessed for centuries. Indeed, tidal mills were a medieval invention for milling grain, and were first mentioned as far back as the 12th century in both England and France. They became increasingly common until well into modern times.

    These mills were built in low-lying areas, close to the sea. Dams containing swinging gates were built along shallow creeks. As the tide came in, the gates swung open inward, away from the sea. Water filled the area behind the dam. When the tide turned, the gates swung shut, forcing the water to flow seaward through the watercourse of the tidal mill.

    In the 1950s the French started to put a major dam construction programme in place, although at the time there were no real success stories of harnessing tidal energy on a commercial scale anywhere in the world.

    The construction of the Rance tidal power plant started in 1960. The project involved building a barrage 330 metres long in which the turbines were to be housed, a lock to allow the passage of small craft, a rockfill dam 165 metres long, and a mobile weir with six gates to rapidly balance the levels for the emptying and filling of the reservoir. The barrage was completed in November 1966 and was inaugurated by Charles de Gaulle. The plant was connected to the French national power grid on 4 December 1967.

    In total, the plant cost 620 million Francs – roughly 94.5 million Euros at today’s prices. The plant produces 0.012 per cent of the power consumed by France, with a peak rating of 240 Megawatts for its 24 turbines. By comparison, a large coal or nuclear power plant generates about 1,000 MW of electricity. Annual output is about 600 million kWh, or an average of about 68MW. In spite of the high cost of the project, the plant’s costs have now been recovered, and electricity production costs are lower, at 18 Euro cents per kWh, compared with nuclear generation at 25 per kWh.

    Special reversible turbines were developed to be used in the Rance barrage. They can produce energy during both the rising and falling tides so that efficiency is increased. Two dozen turbines were installed each with a capacity of 10MW which makes for a total peak power of 240MW, enough to provide energy to 250,000 households.

  3. I’ve always felt that harnessing tidal power is a lot more reliable than acres of windfarms. Here in SW UK we have in the Bristol Channel the second highest tidal ranges in the world. I wonder how much energy turbines strung across the river Severn would generate. Anyone know if a feasability study has been done?

    • In reply to #5 by JeffVader67:

      I’ve always felt that harnessing tidal power is a lot more reliable than acres of windfarms. Here in SW UK we have in the Bristol Channel the second highest tidal ranges in the world. I wonder how much energy turbines strung across the river Severn would generate. Anyone know if a feasability study has been done?

      http://www.tidalenergy.eu/severntidalbarrage.html

      The relatively small scale of many renewable energy generation projects, in contrast with traditional power stations, prevents them from benefiting from economies of scale. This is not a critism that can be levelled against Hafren Power’s proposed Severn tidal barrage.
      Propenents of the scheme argue that as a major infrastructure project, with the projected capability of producing 5% of the UK’s electricity needs, the barrage would benefit from those economies of scale and, as a result, would keep prices down to make it one of the only truly cost-competitive renewable technologies. The strike price would be lower than offshore wind’s and close to nuclear’s. After the price-support period, it would generate virtually free electricity at around £20/MWh – less than half the cost of today’s dirtiest fuel sources. They point to the example of Norway which invested in hydroelectricity some decades ago. Now, 98% of their domestic electricity comes from hydroelectric sources and their consumer electricity prices are 65% lower than in the UK.
      The minimum lifespan of a barrage is 120 years, although engineers estimate 250 years to be more accurate. This compares well with the 60-year lifespan of a nuclear plant or 15 years for an offshore wind farm, and would mean that for at least 100 years, the barrage wouldbe generate the cheapest electricity in the UK.
      The Severn tidal project would cost an estimated £30 billion and plans had been scrapped due to the adverse financial situation.
      The plans envisaged a 10-mile long tidal barrage across the Severn Estuary stretching from Cardiff to Weston-super-Mare, incorporating some 200 turbines, able to generate about 5% of the UK’s annual electricity requirements.

      The project originally received government backing and would play a leading role in plans to meet climate-change targets (40% of UK electricity should be generated from renewable sources by 2020 if EU targets are to be met).
      Opposition to the project has grown over recent years and a coalition of 10 groups including the National Trust, the RSPB and WWF (but not Greenpeace) say the barrage would be a mistake, both economically and environmentally.
      The groups commissioned a report from the economics consultancy Frontier Economics, that concluded that more power could be generated more cheaply by using other green technologies.

      This seems to have given Carbonaceous Cameron and Co. the ideal opportunity to cut green taxes on polluters, dither over carbon reduction targets, and get on with promoting and subsidising gas-fracking and oil-drilling on behalf of the pseudo-green oil and gas companies.

      http://www.greenwisebusiness.co.uk/news/government-rejects-25bn-severn-tidal-barrage-proposal-4088.aspx#.U1kPRqKW9PY

      Doubts over alternative schemes
      One proposal put forward by South West renewable energy experts Regen SW and consultancy firm Marine Energy Matters, puts forward a combination of tidal lagoons and tidal fences, deployed in conjunction with tidal stream technology, wave and wind power, which it claims would generate double the amount of energy as the Severn Barrage and would be far less harmful to the environment.

      But the Government cast doubt on alternative schemes, saying it could take years to develop the technology and said there was no strategic case for funding further studies about alternative schemes at the taxpayers expense.

      These capital based schemes don’t meet with the criteria of minimum effort short-termist irresponsible quick profits which are so loved by carbon Luddite polluters! With bribable politicians collecting “consultancy fees” and sponsorship, it is more profitable to pay stooges to pretend green energy is more expensive than coal, and hike up consumer energy prices, than to get on with developing the sustainable energy-systems of the future!

      There are various other articles and reports on the Severn barrage Scheme if you Google them.

  4. blue energy

    But is it “green’? i.e.,

    environmental impact

    So glad this article includes the serious consideration of effects on mother nature. Love the idea of harnessing energy via tides, but at the same time, large blades and noise sounds like another assault (water creatures). To wit – humans vs nature conundrum.

    • In reply to #6 by bluebird:

      blue energy

      But is it “green’? To wit – humans vs nature conundrum.

      I agree entirely. All these schemes seem incredibly costly in terms of money and resources, when a simpler solution would be to just turn off some lights, whilst we work on ways to reduce our population down to One Planet Living or less. The trouble is that humans never want to go backwards – we apparently must always do more, bigger and errr better?

  5. In the seventies and eighties I was vehemently anti nuclear, but now that we’ve painted ourselves into the corner apropos of power it’s become an essential part of the mix.

    The principal concern about it now is that some fundamentalist fruitcakes will cop hold of some fusionable material; then we can all follow the instructions that used to be disseminated by our gloriously governments: get under the kitchen table, adopt an upright fetal position, head between knees, and, – kiss your arse goodbye!

    • In reply to #8 by Stafford Gordon:

      In the seventies and eighties I was vehemently anti nuclear, but now that we’ve painted ourselves into the corner apropos of power it’s become an essential part of the mix.

      It can be relative safe and fairly clean if we get on with developing the (non-military) Thorium Nuclear Generation

      The world is waking up to the huge potential of Thorium to solve the looming energy crisis; ThEC12 in Shanghai was the event of the year for everyone with an interest in the future of Thorium Energy and its many related fields. China is taking the lead in exploring fresh approaches to nuclear fission in its quest for sustainable, environment-responsible energy that can be delivered reliably and in quantity.

      The principal concern about it now is that some fundamentalist fruitcakes will cop hold of some fissionable material; then we c…

      There is and will be, a lot of dangerous stuff around for a very long time to come – but those politicians and generals just HAD TO HAVE bombs, – so Uranium and Plutonium were the choice instead of Thorium: – after all – You can generate nuclear electricity with Thorium, but can’t make bombs with it!

      The choice was obvious for the no-brainers of brinkmanship government!

      • In reply to #13 by Alan4discussion:

        In reply to #8 by Stafford Gordon:

        In the seventies and eighties I was vehemently anti nuclear, but now that we’ve painted ourselves into the corner apropos of power it’s become an essential part of the mix.

        It can be relative safe and fairly clean if we get on with developing the (non-military) T…

        I totally agree about the ego trips over the bomb. I knew Brigadier Winterbottom who was a stalwart campaigner against nuclear weapons; as a military strategist he knew that they were useless; he likened so called nuclear defence to walking around with the barrel of a gun in your mouth, threatening to pull the trigger if anyone threatened you.

        And waste; well, we and thousands of future generations are stuck with it.

        But the potential of Thorium puts a totally different light on the matter.

        It’s a pity cold fusion was a con.

    • In reply to #15 by mildcat:

      So wind energy is easier than water current energy. Does water current energy kill fish as wind energy kills birds? Which is greener?

      One of the aims of the Strangford Lough experiment was to test environmental effects.

      http://en.wikipedia.org/wiki/Strangford-Lough#Tidal-electricity

      In 2007 Strangford Lough became home to the world’s first commercial tidal stream power station, SeaGen. The 1.2 megawatt underwater tidal electricity generator, part of Northern Ireland’s Environment and Renewable Energy Fund scheme, takes advantage of the fast tidal flow in the lough which can be up to 4 m/s. Although the generator is powerful enough to power up to a thousand homes, the turbine has a minimal environmental impact, as it is almost entirely submerged, and the rotors turn slowly enough that they pose no danger to wildlife.

      Malik Priestley (executive creator of SeaGen) said “tidal power will provide sustainable amounts of green, renewable energy and pose no threats to surrounding wild life”.

      They claim there are minimal environmental problems. Waves and storms are likely to be a much greater danger to wildlife.

      Vastly more tidal and wave energy is dissipated smashing into coastlines.

  6. I am surprised this article on power from the oceans limits itself to tides and waves. There is no mention of Ocean thermal energy conversion (OTEC), which uses the temperature difference between cooler deep and warmer shallow or surface ocean waters to generate electricity Admittedly this process is only likely to be relevant in tropical areas where the temperature differential is significant-and particularly in areas-such as islands- where there is where there is deep ocean not far from the coast. Ocean cold water can also save energy by cooling/air-conditioning as done in Bora Bora.

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