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Wednesday, April 02, 2008

Wind Power That Floats

Advances in floating platforms could take wind farms far from coasts, reducing costs and skirting controversy.

By Peter Fairley
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Ocean bound: Since December, this prototype 80-kilowatt floating wind turbine has been absorbing wind energy off Puglia, Italy, in 108-meter-deep water, beyond the economically viable depth for turbines mounted on the seabed. Data from the machine’s interactions with wind and waves will inform the final design and control schemes for full-size floating turbines.
Credit: Blue H Technologies
Multimedia
•  See the construction and launch of a floating wind-energy platform.

Offshore wind-farm developers would love to build in deep water more than 32 kilometers from shore, where stronger and steadier winds prevail and complaints about marred scenery are less likely. But building foundations to support wind turbines in water deeper than 20 meters is prohibitively expensive. Now, technology developers are stepping up work in floating turbines to make such farms feasible.

Several companies are on their way to demonstrating systems by borrowing heavily from oil and gas offshore platform technology. In December, the Dutch floating-turbine developer Blue H Technologies launched a test platform off Italy's southern coast; last month, the company announced its plans to install an additional test turbine off the coast of Massachusetts, and possibly begin constructing a full wind farm off the Italian coast, next year. Close behind is SWAY, based in Bergen, Norway, which raised $29 million last fall and plans to field a prototype of its floating wind turbine in 2010.

If these efforts succeed, they could open up a resource of immense scale. For example, according to a 2006 analysis by the U.S. Department of Energy, General Electric, and the Massachusetts Technology Collaborative, offshore wind resources on the Atlantic and Pacific coasts exceed the current electricity generation of the entire U.S. power industry.

The success of the floating turbine could hold the key to exploiting that resource. Wind farms such as those installed in Denmark, Germany, and other European waters and proposed for Nantucket Sound, in Massachusetts, suffer from a limited supply of marine construction equipment such as pile drivers and cranes. Emerging Energy Research, a consultancy based in Cambridge, MA, said last week that the global market for offshore wind energy could reach 40,000 megawatts by 2020--enough to power more than 30 million U.S. homes, and more than twice the scale of last year's wind installations worldwide--but only with greatly expanded marine construction capacity. Building even 2,000 megawatts of offshore wind over the next five years will require a significant increase in the marine supply chain, according to Keith Hays, the consultancy's research director.

Floating turbines can be assembled onshore and towed into position, making an end run around the offshore construction bottleneck. The platform that Blue H towed out of Brindisi Harbor in Puglia, Italy, this winter is called a tension-leg platform, a conventional offshore oil and gas platform design that floats below the surface, held rigidly in place by chains running to steel or concrete anchors on the seabed. Installed on top is an 80-kilowatt wind turbine fitted out with sensors to record the wave and wind forces experienced 10 kilometers offshore. Much bigger floating versions--2.5-megawatt and 3.5-megawatt turbines of the scale used in today's offshore wind farms--are under construction by Blue H and could be installed as soon as this fall.

What's unusual about Blue H's design is the turbine's two-bladed rotor--a design that lost out to the three-blade design in the 1990s as the wind-turbine industry scaled up. Martin Jakubowski, Blue H cofounder and chief technology officer, says that the noise and jarringly high rotation speeds that made two-bladers a loser on land are either irrelevant or a plus offshore. Faster rotation, meanwhile, offers two benefits. Jakubowski says that the 30-to-35-revolutions-per-minute frequency, twice that of a three-bladed turbine, is less susceptible to interference from the back-and-forth swing of the platform under wave action.

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Comments

  • Finally!
    SVE on 04/02/2008 at 2:06 AM
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    Using the 70% of the planet that is not inhabited for wind power siting is definitely the right approach!
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  • Phoenix Project, Anyone?
    blunney on 04/02/2008 at 3:01 AM
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    I wonder if these folks have read the Phoenix Project, by Harry Braun?

    http://www.phoenixprojectfoundation.us/
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  • How this make for cheaper wind energy ?
    DJTal on 04/02/2008 at 3:33 AM
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    Building wind turbines a long distance from where the energy is needed requiring miles of cable , and situating them on massive epensive floating platforms , needing thousands of tons of balast does not make for cheaper wind energy . If you scale the size of the floation device shown in the picture up to that of megawatt size turbines , each turbine would require a ridiculously big platform . This is not economical .

    Underwater tidal turbines would be much cheaper , and would not be visible at all providing a predictable supply of energy . Like the one just installed in the mouth of Strangford Loch in Northern Ireland .

    Or perhaps wind turbines could be situated on the same towers as tidal turbines to reduce the cost . There isn't a lack of space on land for wind turbines , it just takes time for people to get used to them and to see the benefits . There are plenty of wasted spaces on rooftops for turbines .
    Rate this comment: 12345
    • Re: How this make for cheaper wind energy ?
      DennisBuller on 04/02/2008 at 9:35 PM
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      I agree with you on all points.
         Except, after 30 years of development, wind is successful and people will invest in it.
         Underwater turbines have yet to prove themselves, and have not gone through this development process.
         Unfortunately, I do not see this technology getting the money it needs to really come to the front, where it belongs....
         For all the talk of alternative energy, if a government somewhere does not pay to develop the technology, I do not see private investors doing it.
         And yes I know about Verdant, but like I have said, to little money for them really to grow like they need to.
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    • Re: How this make for cheaper wind energy ?
      Siphon on 04/03/2008 at 5:52 AM
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      Remember, there are many offshore locations with stronger winds than onshore locations, so the disadvantage of higher capital and installation costs would be partially offset by higher electricity production.

      Also, if Tubercle technology is as advertised, they could plausibly produce power for much less, as they could greatly increase the output per turbine - which is inversely proportional with costs per kWh. Superconducting technology could also help, to make the generator much lighter and so reduce structural costs. Scaleup to even bigger sizes, say 5MWe (already commercially available) could reduce the cost even more.

      It's like the article says, if they can get the cost down, there really is great potential for floating offshore wind, with an extremely large resource base, consistent and reliable winds, and virtually no public opposition.
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      • Re: How this make for cheaper wind energy ?
        neiljg on 04/06/2008 at 6:38 PM
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        In power system terms wind power is a toy, albeit one that delights environmentalists. Every power grid needs to have base load generation so that power is available all the time. If it is a nuclear base generation then wind power is not really necessary because the power generation must be sized to supply power when the wind is not blowing. The same applies for a coal-fired base load generation system because for every MW of wind generator on line spinning reserve must be supplied - ie turbines must be on line and running to pick up any slack when the wind changes. Thus any saving to a coal based system is reduced- the same coal generators need to be there and running whether we have a wind system or not. Also if a large proportion of a power system was wind powered sytem stability problems could arise.
        If wind power was used in a system where a hydro-electric pump storage system was available then it would make much more sense.
        I support alternative energy but not just for feel-good reasons - they must work.
        As far as I understand it the only technology suitable for base-load generation is the experimental Carnot engine driven by temperature differentials in the ocean
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        • Re: How this make for cheaper wind energy ?
          Siphon on 04/08/2008 at 12:25 PM
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          No. Nuclear power is simply too expensive. New projects cost more than 5000 per kWe installed, and getting more expensive almost every month.

          Nuclear cannot compete with wind/caes schemes, especially now with Tubercles.

          Also, nuclear power plants are inflexible, they cannot follow a load because of thermal cycling stresses which make O&M prohibitive, if it can be done at all with existing reactor designs with regards to safety and reliability.

          We already have 20% nuclear, more than enough for baseload. New ones are too expensive, and building a large number would require them to either follow the load, which is expensive, or complement them with natural gas peakers, which is also expensive.

          Flexible, dispatchable electricity systems is what we should be looking for.
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    • Re: How this make for cheaper wind energy ?
      MakeSense on 04/03/2008 at 11:46 AM
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      It bemuses me that someone can declare a project uneconomical two seconds after reading it; whereas, the principles have studied it for years. The advantages of putting turbines far offshore are huge. Stronger, more consistent winds improve the capacity factor, making turbines highly productive and less intermittent. The same turbine can produce 50% to 100% more electricity. The ability to place wind anywhere along the coast actually brings wind closer to populations than previously possible. 90% of Americans live near a coastline and could become a market for offshore wind power.

      I like the two-blade and downwind designs. NREL and the Wind Turbine Company designed a two-blade, downwind turbine years ago that saved on material costs. These should do the same.
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      • Re: How this make for cheaper wind energy ?
        Kevin Bullis on 04/03/2008 at 1:55 PM        		 Technology Review TR Staff
        Nanotechnology and Materials Science Editor
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        Great comment MakeSense. This agrees with what several experts in the area have said.
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        • Re: How this make for cheaper wind energy ?
          DJTal on 04/05/2008 at 4:08 AM
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          You can always find 'some' experts in the field who agree with your point of view , kbullis .

          If you want bring wind energy close to the people , MakeSense , then place wind turbines on roof tops , no need to build expensive new supporting towers for the turbines , and the same goes for the solar power industry . Reducing the number of turbine blades reduces the wieght by a tiny amount compared to the rest of the structure .
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          • Re: How this make for cheaper wind energy ?
            MakeSense on 04/06/2008 at 2:33 PM
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            The economics of residential wind lags that of utility wind, though it is improving fast. The vast majority of homes and other buildings would not be appropriate for residential (small-scale) wind because of turbulent winds. The more the merrier, though. And that's how I feel about the tremendous potential of offshore wind. It can provide inexpensive, high quality power and lots of it. Architectural wind seems like a good option too.
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    • Re: How this make for cheaper wind energy ?
      lkrndu on 04/07/2008 at 2:44 AM
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      Oops. Oops! In fact, quite a few 'oops's' here.

      ALL of this sounds fantastic. So let the engineers, i.e. the sharp-pencil crew, get to work. After all the word 'engineering' is sometimes coupled to 'economy'. As if that weren't an oxymoron.

      Do the math. If the economies and compromises work out, great.

      Here are a couple of things that HAVE changed since 1975, and certainly since 1920, the two time benchmarks in the Phoenix project schema:

      Permanent magnet alternators are simpler, cheaper, and much more productive than in the past thanks to better magnet technology.

      Solid-state power conversion technology is far more capable than even a few years ago.

      There are more rooftops than ever.

      And here are some things that are true now, just as they have been, forever:

      AC at high voltage may be transmitted over longer distances with less line loss and using smaller, cheaper conductors than can lower voltages or DC.

      Rooftops are lousy places for wind turbines, beween the turbulence and obstructions to airflow that abound and the structural and nuisance effects of noise and vibration loads.

      And yet, re-animations of some OLD turbine designs (Darrius and its variants, among several possibilities) offer decent efficiencies combined with rather handsome, one might even say beautiful forms.

      Who knows? Might work.
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  • [no subject]
    zig158 on 04/02/2008 at 5:41 AM
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    I find it interesting that spokespeople talk about the carbon-emissions trading markets. Right now there are no carbon-emissions trading markets, what makes them so sure there will be one in the future? A lot of the stuff out there right now is looking promising but unless you can compete with oil on a fair footing it will never be more than just a nitch market.

    With a good mass reproducible modular design, this could be a top contender.

    By the way, carbon-emissions trading are subsidies. They are artificially imposed by the government.
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    • Re:
      jpontin on 04/02/2008 at 10:01 AM      		 Technology Review TR Staff
      Editor in Chief and Publisher
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      Of course there is a carbon market--indeed, a very large and robust one--in Europe.
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    • Re:
      franquellim on 04/07/2008 at 1:04 PM
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      You describe carbon-emissions trading as a subsidy, but I think you're missing the point. Conventional power generation is currently "subsidized" by the fact that it does not factor in external costs, such as health care costs and environmental damage caused by its generation. In addition, if you factor in the massive government subsidies for oil extraction, wind power can be more than merely competitive. The extraction industry benefits greatly from the US military presence in the Gulf region and around the world, not to mention the significant subsidies that are provided to these corporations to exploit public lands for corporate profit.
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    • Re:
      Tysto on 05/13/2008 at 1:04 AM
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      "unless you can compete with oil on a fair footing it will never be more than just a nitch market."

      Toilets, plumbing, sewage pipes, and sewage treatment plants can't compete "on a fair footing" with throwing your poop in the street, but we all agree the higher cost is worth it.
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  • Reducing costs
    m.pivoda on 04/02/2008 at 7:45 AM
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    What about moving a manufacturing to the platform so that generated energy can be consumed in the same place? There would be no need for expensive undewater cables.
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  • Deep Water Wave Action
    jgkneuer on 04/02/2008 at 8:45 AM
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    Wave action would seem to be a challenge to securely anchoring an off-shore wind turbine, unless the floating structure was designed to minimize the effects of that wave action. An interesting challenge would be to design energy absorbing hydrodynamics - essentially creating a dual fuel power station.
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  • Electrolysis and offshore wind gen
    rlindsl on 04/02/2008 at 11:57 AM
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    IF we ARE going to be a hydrogen economy... then why are not we having the most obvious and elementary of discussions? Generation and storage of hydrogen offshore (wind, electric, electrolysis, hydrogen) seemes like the greenest technology possible. It trades the transmission losses back to the coast for the electrolysis-based conversion loss.

    Offshore wind and solar power generating arrays could become the largest manmade structures in history, there are scales of economy and fewer logistical constraints compared to land based solar and wind gen facilities. There are even financial and regulatory incentives to offshoring hydrogen generation. Given the hoopla over gas terminals and the flexibility in sites possible of the offshore facilities, hydrogen pipelines may be better than tanker storage and transport in some places.
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    • Re: Electrolysis and offshore wind gen
      Siphon on 04/03/2008 at 5:42 AM
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      Considering that transporting hydrogen is far more lossy than electricity, and that centralised storage would almost certainly be more economical than storage on hundreds of wind sites, and that hydrogen storage systems have far greater capital costs than e.g. AACAES, not to mention inherently greater losses, this is not the best proposal I've heard.
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      • Re: Electrolysis and offshore wind gen
        rlindsl on 04/12/2008 at 10:36 PM
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        Low pressure gas lines are not more expensive then electrical lines. Underwater high voltage lines have several unique electromechanical issues, I think you are aluding to tanker transport of Hydrogen....
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        • Re: Electrolysis and offshore wind gen
          Siphon on 06/04/2008 at 9:59 AM
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          Natural gas infrastructure, maybe. But hydrogen embrittles many materials used in the natural gas industry, so expensive materials would be required for the hydrogen pipeline. Also, there are more safety issues with hydrogen. I'm not saying it's dangerous; making it safe is quite feasible. But it adds even more to the costs. There is also the fact that there is relatively little experience in hydrogen infrastructure technology compared to electrical infrastructure.

          But the losses inherent to the hydrogen scheme make it uncompetitive to transporting electricity, even when the downsides of the latter are considered.
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    • Re: Electrolysis and offshore wind gen
      MakeSense on 04/03/2008 at 11:51 AM
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      We will never be a hydrogen economy.
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  • 3-in-one
    exushri on 04/02/2008 at 12:21 PM
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    Couldn't they build a structure that supports win  turbine on the top + solar panel on the base + wave power below the surface. They could maximize the energy potential of such structures.
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    • Re: 3-in-one
      MakeSense on 04/06/2008 at 2:26 PM
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      Where favorable conditions overlap, those options would be important. Windy areas do not necessarily lie in sunny areas or where predictable currents exist. But where they do, it could be profitable to add on.
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  • Wind Power That Floats
    kearns on 04/02/2008 at 5:36 PM
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    How do they manage to transfer the power to the mainland to use?  Recall that you're moving high voltage through seawater over tens of miles.  Is it transferred as AC and if so at what frequency?
    Obviously they do it, but that area gets little attention.  Usually the pumping losses for electricity are pretty large over long distances.
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    • Re: Wind Power That Floats
      MakeSense on 04/03/2008 at 11:58 AM
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      Over distances of 20 or 30 miles, AC losses are pretty small, say a few percent compared to the greatly improved sizes and capacity factors possible at those locations.

      High voltage DC (HVDC) lines have become the best choice for long distances. If many wind farms are put offshore, it could be advantageous to collect power from them through a connected system of HVDC lines. Since wind power produces DC power, no conversion to AC would be needed, thus saving money and weight. The added bonus would be a great reduction in intermittency.
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      • Re: Wind Power That Floats
        lkrndu on 04/07/2008 at 3:03 AM
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        'Since wind power produces DC power, no conversion to AC would be needed, thus saving money and weight.'

        In fact wind power may produce AC - or DC, depending on choice of hardware, i.e. alternator or DC generator driven by the turbine. I'm not certain which has the upper hand in productivity and economics but imagine the factors involved to be many: distance to consumer, mode of transmission, capacity of turbines, siting, and more.

        In theory an alternator might be made to produce high-voltage low-current power, which may be efficiently transmitted over some distance.

        Then again wind turbines which spin at variable rates produce AC with variable frequencies. Harnessing several together thus becomes a trick which can be met by rectifying the output of each turbine-alternator to DC at high enough voltage to make long-distance transmission economical.
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        • Re: Wind Power That Floats
          MakeSense on 04/08/2008 at 12:32 PM
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          Wind turbines produce DC power natively, as do solar power technologies. It must be converted to AC current. Usually the converter is in the tower base. This equipment would not be needed if the turbine connected directly to an HVDC conduit. Where the HVDC line entered the AC transmission grid, a conversion to AC would be needed.
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  • Wind Power That Floats
    jmaximus9 on 04/02/2008 at 9:39 PM
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    I say millionaire waterfront property owners are just going to have to get used to seeing Windmills a few miles offshore.
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