Clean Power

Published on May 23rd, 2013 | by Zachary Shahan


Taller, Stronger Wind Turbines From Concrete

May 23rd, 2013 by  

Iowa State engineers have been working on making wind turbines taller and stronger by using concrete instead of steel. Will it stick?

Taller wind turbines are better — really, it’s been confirmed. So, making wind turbines taller and stronger seems like a never-ending goal (though, I imagine it does have its limits). Let’s just hope the concrete that is used is one of the greener and stronger types of concrete being developed.

For more details on the Iowa State research, here’s a full press release from Iowa State University:

Grant Schmitz studies a concrete test panel for signs of cracking under heavy loads. Larger photo. Photo by Mike Krapfl.

Grant Schmitz studies a concrete test panel for signs of cracking under heavy loads. (Click to enlarge.)
Image Credit: Mike Krapfl.

AMES, Iowa – Grant Schmitz, eyes inches from a 6.5-by-12-foot panel of ultra-high performance concrete, studied the smooth surface for tiny cracks. He and other research engineers carefully marked every one with black markers.

Schmitz, an Iowa State graduate student of civil, construction and environmental engineering, and Sri Sritharan, Iowa State’s Wilson Engineering Professor and leader of the ’s College of Engineering‘s Wind Energy Initiative, were trying to answer some basic questions about using concrete panels and columns to build wind turbine towers using prefabricated, easily transportable components.

Could assembled concrete towers be a viable alternative to the steel towers now used for wind turbines? Could concrete towers be a practical way to raise turbine towers from today’s 80 meters to the steadier winds at 100 meters and taller? Which of three ways to connect the columns and panels works best for wind turbine towers?

“We have definitely reached the limits of steel towers,” Sritharan said. “Increasing the steel tower by 20 meters will require significant cost increases and thus the wind energy industry is starting to say, ‘Why don’t we go to concrete?’”

And so, Sritharan and Schmitz watched as Doug Wood, engineering specialist and manager of Iowa State’s Structural Engineering Research Laboratory, typed in the commands for the lab’s hydraulic equipment to push or pull with bigger loads on a full-size test segment of a 100-meter concrete wind turbine tower. With each increase, the segment creaked and thumped.

The goal was to test three column-and-panel segments for the expected loads at the top of a turbine tower. The engineers wanted to see if the segments could handle 150,000 pounds of load, 20 percent over the extreme load at that height.

Sritharan and Schmitz designed the concrete towers to be built in hexagon-shaped segments, with six panels connected to six columns. They tested three methods to connect the panels and columns: bolted connections; horizontal, prestressed connections with cables running through the tower pieces; and a grout connection using ultra-high performance concrete poured into the joints between panels and columns. In addition, the concrete columns were attached to a foundation using prestressing methods.

Aaron Shelman -- green shirt, a doctoral student in structural engineering -- and Owen Steffens, red shirt, a research associate in civil, construction and environmental engineering -- check a concrete panel for signs of cracking. (Click to enlarge.) Image Credit: Mike Krapfl.

Aaron Shelman — green shirt, a doctoral student in structural engineering — and Owen Steffens, red shirt, a research associate in civil, construction and environmental engineering — check a concrete panel for signs of cracking. (Click to enlarge.)
Image Credit: Mike Krapfl.

All three versions of the test segments withstood 150,000 pounds of lateral load. The researchers also tested the segment with the grout connections under 170,000 pounds of load, 36 percent beyond extreme load. In each test, the segments performed well with no sign of distress at the operational load of 100,000 pounds. Some distress to the test segments was visible at the extreme load and beyond.

“Panel cracking was expected at very high loads and will be closed upon removal of the load,” Sritharan said. “This can also be avoided if this is requested by the industry.”

After all the testing, Schmitz said, “I definitely think we’re getting close to being able to use this technology in the industry.”

The concrete tower design offers several advantages over today’s steel towers:

  • increasing steel’s 20-year tower life by using ultra-high performance and high-strength concrete
  • easier transportation because pieces are small enough for standard trucking
  • precast concrete industry is established across the country
  • less reliance on imported steel for turbine towers
  • smaller precast pieces can be assembled on site in multiple ways
  • the concept is versatile and towers can be tailored for any turbine size or even a height beyond 100 meters.

“What we have shown is that this system can potentially be deployed to a 100-meter height for a 2.5 to 3 megawatt system,” Sritharan said.

Moving from 80- to 100-meter towers is important for wind energy producers.

Sritharan said wind conditions at 100 meters are steadier and less turbulent. Taller towers also allow for longer turbine blades. Studies indicate all of that can increase energy production by 15 percent.

Sritharan said as turbine size increases, the need for taller towers will be inevitable.

“A lot of people are talking about taller, concrete wind turbine towers,” he said. “And we’ve already established a new versatile concept with multiple construction options.”

Sritharan said the studies of concrete turbine towers will continue at Iowa State. The project has been supported, in part, by a $109,000 grant from the Grow Iowa Values Fund, a state economic-development program. Industry partners in the experimental program are Clipper Windpower, a company based in Carpinteria, Calif., with a turbine design and manufacturing facility in Cedar Rapids; Lafarge North America Inc. of Calgary, Alberta, Canada; and Coreslab Structures (OMAHA) Inc. of Bellevue, Neb.

And Schmitz, who’s describing the project for his master’s thesis, could breathe a little easier after the successful testing.

“There is a lot of preparation for this,” he said. “We started coordinating the tests in August. We had to arrange for the precast and transportation and assembly through the fall. It’s definitely a relief when you see it handling the capacity it has to meet.”

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is tryin' to help society help itself (and other species) with the power of the typed word. He spends most of his time here on CleanTechnica as its director and chief editor, but he's also the president of Important Media and the director/founder of EV Obsession, Solar Love, and Bikocity. Zach is recognized globally as a solar energy, electric car, and energy storage expert. Zach has long-term investments in TSLA, FSLR, SPWR, SEDG, & ABB — after years of covering solar and EVs, he simply has a lot of faith in these particular companies and feels like they are good cleantech companies to invest in.

  • ThomasGerke

    Very curious news, since companies like Enercon have been using mass produced segmented concrete towers for years. They just opened another plant in Austria to produce 200 towers for 2-3 MW turbines with hub hights of 80-130 meters.

    Hope this isn’t a bummer for those students… but steel towers are not at all common IMHO.
    Building 100+ meter large wooden towers is the new thing. 😉

    • Sean

      beat me to it.

      keep in mind this is the marketing department for a US collage. They really should employ someone to do some basic editing before making fools of themselves.

    • Hans

      I think it is American arrogance: If it is new to the US it must be new to the world.

      • ThomasGerke

        Well, it certainly displays a lack of academic awareness & cooperation… or an inability to do basic research. 😉

        Here’s a german language TV documentary about the construction of a E-126 (back in 2010 I think).

        (Minute 21 is also kinda cool 😉 )

    • we have covered wooden wind turbines. i almost mentioned it in the intro.

  • James Wimberley

    It’s a bit disturbing to hear that steel towers only have a 20-year life. Can you confirm this?

    What usually happens as equipment ages is that inspections get more frequent until a problem shows up. In the case of wind, technical progress also means that repowering becomes economic, with a new tower and turbine on the same site..

    • Bob_Wallace

      I’m pretty sure that’s inaccurate.

      The wind turbines now being taken down at Altamont Pass wind farm have been operating for 30 years. As far as I know the reason that they are being replaced is not due to tower fatigue, but that maintenance costs for the turbines was starting to increase and it made more sense to replace them with newer, more efficient units on taller towers.

      A few years back there was speculation that concrete footings on poor quality soil might give out after twenty years use. This, I think, morphed into some sort of 20 year lifetime for wind turbines. That along with a misunderstanding of the use of 20 year financing in LCOE calculations.

      I’ve never heard of a tower failure. Might have happened, but if so it’s probably as rare as a turbine bursting into flames.

      • Ronald Brak

        It’s not the same thing, but steel transmission towers in the US apparently have an estimated lifespan of 100 years and their footings 80 years. South Australia’s steel and concrete stobie poles have a lifespan of about 80 years, but tragically are considered to be impractical beyond 36 meters, making them unsuitable for both wind turbine and space elevator construction.

        • Bob_Wallace

          We gotta’ get back to work on that space elevator thing.

          I’m getting tired of taking the stairs….

      • Otis11

        Added benefit – the new wind turbines in the Altamont Pass wind farm (aka the taller wind turbines) are also significantly more bird friendly!

        Just FYI for people who dislike Wind for “environmental” reasons. :Insert eye-roll here:

  • disqus_ooeOMumBe6

    Why do you need a tower?

    • Bob_Wallace

      Because to date no one has demonstrated a cheaper way to turn wind into electricity than a horizontal axis wind turbine, mounted way up high where the wind is strong and clean.

      If new, better technologies emerge then they will replace other approaches.

      “To date” and “if” are important.

      • disqus_ooeOMumBe6

        Try looking at the web site link – They’ve just demonstrated kite power!

        • Bob_Wallace

          For how much are they selling electricity to the grid?

          • disqus_ooeOMumBe6

            From their FAQ:-

            Makani estimates that the cost of energy will generally be about half the cost of conventional wind.

          • Bob_Wallace

            Sorry. That is not a statement for how much they are selling electricity. That’s a projection of what they might be able to sell electricity for if things work out as they hope. That problematic “if” stuff.

            Let’s circle back –

            “Why do you need a tower?

            “Because to date no one has demonstrated a cheaper way to turn wind into electricity than a horizontal axis wind turbine, mounted way up high where the wind is strong and clean.”

          • Matt

            Bob is so on point here. In the work of engineering there is the “best solution to date” and then their is research into other options. The best solution can be different for different constraints. But so far the best for wind power is three blade horizontal axis wind turbine on tall towers.
            Well research and dreams. You never know whenwhat the next great solution will be. But be sure it will take effort way past a you-tube video of a mock-up.

          • disqus_ooeOMumBe6

            My question was intended to be rhetorical. Yes, the current best is a wind turbine “mounted on a tall tower” but this firm (who I don’t have any links with) have got rid of the concrete/steel tower and replaced it with a simple tether to a kite which has the turbines mounted on it. Videos on their site (I believe) show actual flights rather than just mock-ups. By extending/retracting the tether, they can take advantage of different winds at different heights during the day which is what you can’t do with a fixed tower.

          • Bob_Wallace

            Do you understand that until they turn ideas and test flights into proven technology that they cannot replace something that has been proven to work?

            The big point –

            1) There is technology which has been proven. We can take the best of that and put it to use.

            2) There are ideas which are interesting but until they actually are proven they have no practical value.

          • disqus_ooeOMumBe6

            At what point does technology become “proven”?

            I would have thought that was when it was shown to do what it was designed to do. In this case when electricity is generated by their method then their technology is “proven”

            OK, it hasn’t quite got into being delivered to customers yet but the basic idea is “Proven”.

            To paraphrase the original question “Why does a turbine need a tower to sit upon when it can use a tethered kite (or something else) instead?” Technology doesn’t sit still.

          • Bob_Wallace

            Just arguing for the fun of arguing?

          • disqus_ooeOMumBe6

            No. I post a link to a firm that looks like it is going to make the original article redundant which I thought everyone would be interested in especially as it’s clean, innovative and cheaper than the current solution and I get “It’s not proven technology therefore we won’t consider it” which is an attitude I don’t agree with. In my opinion, the best attitude for an engineer is to keep asking questions like “why do we need this?” and “Is there a better solution to this problem?”. Sometimes we can’t see how to improve matters, but by asking the questions we are at least thinking about improving matters which is what we as engineers need to do.

          • disqus_ooeOMumBe6
          • Bob_Wallace

            Look, you do not know that this device is cheaper. There aren’t any producing electricity.

            Learn to tell the difference between reality and wishing.

            I’m done with this one.

          • Matt

            Even building a prototype and proving it works does not mean a solution will take off. Look at OTEC, the US gov build a prototype in HA and proved it work. But not one want to spent the funds needed to build a full scale plant.

            I like the kite idea, Google dropped some cash because they believe also. I like the generation on the ground (yo-yo) version better, like keeping more on the ground. Less noise. But there are a couple issues. Thing FAA, those cables require restriction air space, and radar impact. They already want to limit where a short 1000 foot tower goes, think how they will fell about a kite flying at 10-20k feet.

    • Otis11

      Great link – may not be economical ATM, but looks like some promising research.

      @ZShahan3:disqus – Potential article? (Also news worthy – apparently they were recently acquired by google…)

  • arne-nl

    I know of even more greener concrete 😉

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