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Published on August 20th, 2012 | by Joshua S Hill

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New Construction Methods Could Make Offshore Wind Turbines More Efficient



 
A Cambridge University engineer is urging the wind power industry to look at the designs for offshore wind turbines in an effort to increase their efficiency and decrease the amount of energy required to produce and install the massive towers at sea.

Jim Platts of the Institute for Manufacturing at the University of Cambridge believes that the wind power sector could achieve much higher payback ratios if turbines were installed using guyed towers rather than the heavy free-standing towers currently in use.

“The development of the wind turbine industry, and the way in which it works with the civil engineers who make the heavy supporting towers and foundations, which are not visible out at sea once the turbines are installed, mean that we have ignored something which is almost embarrassingly obvious in our race to meet the targets set for renewable energy production,” said Platts.

“We urgently need to reduce the high levels of energy embedded in offshore wind turbines which make them both ineffective in energy payback and costly in financial terms. We can do this fairly easily if we invest in more innovative methods for making and installing the towers and foundations that support them.”

The effectiveness of a wind turbine is determined by one key figure: it’s harvesting ratio.

This ratio is a measure of the energy it provides compared to the amount of energy required to manufacture the tower.

Wind turbines comprise three main elements: the blades that harness the wind energy; the gearbox and generator mechanisms that produce the electricity; the tower that supports these moving parts; and the foundations that hold the tower in place. The tower is conventionally made of steel and the foundation in steel and concrete.

A turbine used on land will see two-thirds of the total energy invested to produce the tower embeeded in the moving parts, with the final third invested into the tower structure. Onshore turbines usually achieve a harvesting ratio of 40:1.

However, when you situate a turbine offshore, with the need for heavier towers and massive foundations, the harvesting ratio drops to 15:1. “When you look at offshore wind turbines you see a series of slim structures – what you don’t see are the far heavier supporting structures below the surface that they slot into,” said Platts.
 

 
“Steel is prone to corrosion and to fatigue,” Platts added. “This begs the question: could we do better with other materials. The answer is yes, we can use composites for towers just as we do for blades. They are lighter, stronger, corrosion free and more resilient than steel.”

A preliminary study conducted by the University Institute for Manufacturing suggests that guyed towers could offer significant advantages that conventional heavy towers lack. The use of steel cables fixed to the sea bed by screw anchors could result in significantly slimmer towers and less weighty foundations.

The study found that with the resulting reduction in steel and concrete, the harvesting ratio would increase to 25:1.

“The use of guyed towers is just the first step for the industry to take. The second step would be to make towers in composite materials which are less energy intensive to make than steel which relies on smelting and concrete that also depends on a chemical reduction process in manufacturing cement.  Composites also have a longer life than steel as they stand up to fatigue much better. Using these new materials could increase the harvesting ratio still further to 32:1 and extend the lifetime of a turbine installation from the present 20 years to up to 60 years,” said Platts.

“The Finnish wind turbine manufacturer Mervento has shown the way with a guyed turbine designed for use in the Baltic. Other producers – such as those making turbines for sites in the North Sea – need to take heed and invest in research into designs that take a similar approach to making the industry far more energy efficient and sustainable.”

Source: University of Cambridge
Image Source: Phil Hollman

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About the Author

I'm a Christian, a nerd, a geek, a liberal left-winger, and believe that we're pretty quickly directing planet-Earth into hell in a handbasket! I work as Associate Editor for the Important Media Network and write for CleanTechnica and Planetsave. I also write for Fantasy Book Review (.co.uk), Amazing Stories, the Stabley Times and Medium.   I love words with a passion, both creating them and reading them.



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  • Dave2020

    I think this research could be better focussed on the development of marine renewables that are ideal for Europe. It fails to address any of the critical issues here. This is the wrong design premise.

    Round 3 UK windfarms are now being planned for water depths in excess of 50 metres. Obviously the foundations and towers will be getting ever more expensive, even if there can be some savings from new designs and materials.

    It would be better to do away with them altogether, and here’s yet another reason why:-

    http://www.businessgreen.com/bg/news/2199437/germany-delays-windfarm-because-its-not-fit-for-porpoise-yet

  • Dave2020

    “The effectiveness of a wind turbine is determined by one key figure: it’s harvesting ratio.”

    No it’s not. The effectiveness of ANY variable renewable energy source is determined by the dispatchability of the electricity it produces. QED. The harvesting ratio isn’t a key figure – it’s irrelevant. Try starting again, Jim.

    It is grossly inefficient to generate electricity when you can’t use it.

    If you want to harvest more energy, what about the wave power that you have ignored?

    “invest in more innovative methods for making and installing the towers and the foundations that support them.”

    How about investing in sensible innovative designs that have NO towers OR foundations? How about putting your undoubted talents to work to design systems that supply electricity when there is a market demand for it?

    “The use of guyed towers is just the first step for the industry to take. The second step would be to make towers in composite materials.”

    Wrong steps in the wrong directions. Jim Platt – look at what the industry is already doing on floating off-shore wind and TRY to THINK ahead of them. That’s the way to go.

    • http://www.facebook.com/people/Stan-Stein/1756064509 Stan Stein

      Oh brother…. an up and cumming master of hypothesese and self servitude….”when there is a market demand for it”?
      As long as there are fossile fuel powerplants…..there is a demand for green power…..there IS no “good” fossile fuel power…none of it is environmentally good…..or safe
      Please enlighten us, as to your qualifications which would allow for your critical and condecending comments to Jim.

      • Tom G.

        Hi Stan:

        I don’t see the “critical and condescending” part but you are certainly entitled to your opinion. I know I express mine all the time, LOL.

        To me, the article would have been better served with a slightly different title. Instead of “…Offshore Wind Turbines More Efficient” I would have replaced this with – More Cost Effective – because I believe that is what we are talking about. A more cost effective turbine is one that costs less to manufacturer, install and operate and is therefor more competitive. I guess we could then say it is a more efficient use of resources.

        But by the same token Bob is correct since the output [kWh] of a turbine is based on other factors.

        I think we are all talking about oranges and oranges [efficiency] but view the results differently. The English language is not always precise? LOL.

        • Dave2020

          Thank you for your comment Tom. I agree with you.

          Somehow, strangely, Stan seems to assume that I’d advocate the fossil fuel option. Nothing could be further from the truth.

          Stan should read this article:-

          http://www.businessgreen.com/bg/news/2193500/osborne-moves-to-kill-green-economy-with-gas-manifesto

          and understand that the sole purpose of my radical approach to marine renewables is to make gas-powered generation commercially unsustainable. Integrated (before generator) energy storage seems to be the best way to do that. High capital outlay – yes, but much lower running costs and zero carbon in operation. A WEC is also an essential part of the (more bang for your buck) solution, I think:-

          Clean Technica (http://s.tt/1lPFQ)

          The “unworkable” Energy Bill is trying to rig the market in order to ‘grandfather’ gas plant (without CCS) up to 2045. The UK will have to import most of that gas! – insane!

          The UK Chancellor is a fool of the highest order. The Treasury and the DECC both exemplify the saying “the lunatics have taken over the asylum”. But the lunatics are fighting amongst themselves too!

    • Bob_Wallace

      That’s incorrect Dave. Effectiveness of wind turbines is measured by output. Nothing more.

      You are correct that dispatchable energy sometimes has higher value than does power from a non-controllable variable source, but we aren’t at that point on any of the US grids yet.

      We are many years from the point at which we will need to add storage and/or backup generation in order to utilize variable input generation. We already have sufficient dispatchable generation and storage to allow our grids to become 25% (Eastern grid) to 35% (Hawaiian grid) variable renewable. EVs on line will boost that percentage higher.

      In fact, those 25% to 35% limits will be shoved upwards as coal is replaced with natural gas generation.

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