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Mammoth 50 MW wind turbine blades could revolutionise offshore wind

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CleanTechnica

A new design for mammoth wind turbine blades longer than two football fields could deliver 50MW offshore wind turbines.

The research for the new wind turbine blades designs has been conducted by the Sandia National Laboratories, a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the US Department of Energy’s National Nuclear Security Administration.

According to Sandia, it was challenged to design a low-cost offshore 50 MW turbine with wind turbine blades of more than 650 feet, or 200 meters in length.

That’s two and a half times longer than any existing wind turbine blade.

“Exascale turbines take advantage of economies of scale,” said Todd Griffith, lead blade designer on the project and technical lead for Sandia’s Offshore Wind Energy Program. Sandia has been working on wind turbine designs for a while now — including 13 MW systems using 100 meter blades, which are the basis for Sandia’s Segmented Ultralight Morphing Rotor (SUMR) designs.

Sandia’s 100-meter blade is the basis for the Segmented Ultralight Morphing Rotor (SUMR), a new low-cost offshore 50-MW wind turbine. At dangerous wind speeds, the blades are stowed and aligned with the wind direction, reducing the risk of damage. At lower wind speeds, the blades spread out more to maximize energy production. (Illustration courtesy of TrevorJohnston.com/Popular Science)

Sandia’s 100-meter blade is the basis for the Segmented Ultralight Morphing Rotor (SUMR), a new low-cost offshore 50-MW wind turbine. At dangerous wind speeds, the blades are stowed and aligned with the wind direction, reducing the risk of damage. At lower wind speeds, the blades spread out more to maximize energy production. (Illustration courtesy of TrevorJohnston.com/Popular Science)

50 MW wind turbines are a long way off, but according to Sandia, “studies show that load alignment can dramatically reduce peak stresses and fatigue on the rotor blades.” This would not only reduce blade costs, but eventually lead to the mythical 50 MW wind turbines.

And these developments are vital to the offshore wind industry in the US.

“The US has great offshore wind energy potential, but offshore installations are expensive, so larger turbines are needed to capture that energy at an affordable cost,” Griffith said.

“Conventional upwind blades are expensive to manufacture, deploy and maintain beyond 10-15 MW. They must be stiff, to avoid fatigue and eliminate the risk of tower strikes in strong gusts. Those stiff blades are heavy, and their mass, which is directly related to cost, becomes even more problematic at the extreme scale due to gravity loads and other changes.”

That’s where Sandia’s segmented designs come in (as seen above). Not only do they provide more cost-effective manufacturing and installation — as the blades can be manufactured in segments rather than as a massive long blade, which extends to transportation and installation as well — but, inspired by how palm trees move in storms, the blades would be positioned downwind, and the segmented sections would bend in the wind while retaining segment stiffness.

“At dangerous wind speeds, the blades are stowed and aligned with the wind direction, reducing the risk of damage,” explained Griffith. “At lower wind speeds, the blades spread out more to maximize energy production.”

Source: CleanTechnica. Reproduced with permission.  

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  • DoRightThing

    Excellent and obvious idea, but the continuous oscillating stress on each blade passing through the turbulent wake of the tower may be a problem.
    This could be mitigated if the tower was an aerofoil shape, but then the whole tower would need to rotate into the wind.

    • Mark Roest

      Actually, an outer fairing could do the rotating around a stationary primary structure.

      • DoRightThing

        Good idea, and I would suggest greater distance of the blades from the tower to allow for the fairing’s tail to restore laminar flow.

        • Pedro

          Would also need to counter balance on the upwind side I expect

          • DoRightThing

            Plenty of mass in the generator to offset that. Would just need a longer driveshaft, and it probably wouldn’t hurt to make it a little front-heavy to compensate for the drag of the blades.

          • Pedro

            They need to employ us to solve the engineering problems 😉

      • Jens Stubbe

        Great idea and used a lot for smaller wind turbines for boats and urban areas because it cancels a lot of noise caused by wind induced vibrations.

        Also dynamic stabilizers akin to those used for tall buildings are obvious and also under development and ready to enter mainstream turbines.

        Also common aerodynamic tricks that limits the laminar flow instability and thereby the formation of larger and dangerous vortices are standard knowledge for all CFD experts and ready to go into wind turbine designs.

        I do not fancy the hinged blade idea too much and wonder if anyone will bet on it for real.

        Currently the blade technology improve at a steady pace and just moving the blades behind the tower will allow for a great extension of the blade and make winglets practical without tower collision danger.

        The feasibility of a 50MW turbine with current technologies is probably ok but the economics of such a leap out of current form factor is probably not sufficiently attractive.

        Vestas is building a test wind turbine at approximately 3,6MW and 150 meter hub height this year so taller onshore wind turbines is a clear trend to look for in the future.

    • Colin Nicholson

      There are ways to turn the big vortices into little vortices. The spirals on Chimneys for instance. Forcing a “virtual aerofoil” is another … but it will need careful attention.

      • Alastair Leith

        is that the source idea of spiral brick chimneys from queen anne era and before?

        • Colin Nicholson

          Probably. Certainly modern Chimneys were built with spiral paths around the circumference to minimize vibration. It certainly was the motivation for wrapping cord around and around your board racks to stop the roof of the car drumming at speed.

  • George Papadopoulos

    It was the down wind blades that NASA scientists found to be cause major infrasound issues: http://www.nrel.gov/docs/legosti/old/1166.pdf

    • Colin Nicholson

      Good to see you are back George. The MOD turbine had a gantry type support, not a pylon, and as the report clearly points out the Lattice type construction resulted in most of the noise being generated as the rotor blades passed the lattice work. Give me the opportunity and I’ll keep quoting the report. but here is a bit below and, which bit of “off” and “shore” don’t you understand?

      “4.1 AEROACOUSTIC NOISE GENERATION MECHANISMS

      As discussed in Section 3.1.1, the source of the residents’ complaints was

      traced to the acoustic impulses being ‘generated as the rotor blades passed

      through the wakes of the large, cylindrical tower legs. “

      • George Papadopoulos

        So can you guarantee this model won’t produce significant infrasound?

        • Colin Nicholson

          Here you go again. “significant”. There is significant infrasound where I am at the moment in Melbourne. If you mean will the WT be annoying to humans 5 km away – only to the occasional yachtie who penetrates the nogo zone. You would do more to worry about the off shore effects of aeroplanes which can avoid noise abatement restrictions by flying over the ocean and making lots of noise. Remember your confusion over Mascot? Then you could ban tunnel boring machines – They are designed by their very nature to make lots of noise, but it is to be used underground with the escape of a bit of infrasound.. There has always been a suspicion that you are looking to ban any noise making machine from anywhere on the globe.

          • George Papadopoulos

            Colin, infrasound at the very low range (say 1 hertz) travel far longer than 5km…

            I find it fascinating, how we barely have started a conversation and your already resorting personal attacks. Some weakness there?

          • Colin Nicholson

            George First of all I keep everything you say for me to present to the next senate inquiry, They may find it interesting in your continual fallback to a claim of “personal attack”. Last time you will recall, you quoted draft instead of final reports – all duly noted. I’m hoping for more of the same. But to your point. You obviously have little knowledge of the background infrasound generated by a 20knot wind fetching over the ocean particularly where wave patterns meet.. There are several studies on power spectral densities generated by the ocean one around the 0.8Hz region. .Infrasound may travel around the globe several times as was witnessed during atmospheric testing of nuclear weapons – To suggest that 50MW turbines in any number can produce significant infrasound compared to the ocean is ludicrous

          • George Papadopoulos

            Colin I think you lack any understanding of qualitative aspects of infrasound and what it means. For example, you have read the NASA paper, but you didn’t understand the semantics of why wind turbine infrasound was causing issues to the local inhabitants.

          • Colin Nicholson

            Are you talking to the topic here George? If so, then the local inhabitants are sea gulls who may in fact be able to “read” infrasound better than humans.

          • George Papadopoulos

            Colin, sorry but are the offshore 50MW monstrous atrocities going to be placed in the middle of the Pacific Ocean, or somewhere close to Australia’s coastal towns, perhaps Botany Bay or maybe Sydney Harbour, or maybe Lake Macquarie actually or even more “appropriately” the Barrier Reef?

          • Colin Nicholson

            Oh Boy the Senators are really going to love this stuff. How many offshore turbines are there currently in Sydney Harbour, How many at lake Macquarie. Good reason for that. I also notice that the GBR is not exactly swamped in wind turbines. How many are planned for these locations? Do you know the cost of offshore wind? Once you know the cost, there is not enough offshore wind in any of these locations. The most likely location for these large turbines is Dogger Bank. Still, I encourage you to keep this up

          • George Papadopoulos

            So where do you propose to put them? In the deep ocean underwater?

          • Colin Nicholson

            As I said above Dogger Bank

          • DogzOwn

            About travel distance, they say that air is so clear in East Texas that, visibility good enough to be able to see the back of your own head! On infrasound, Is a fart, often louder when close to WT, capable of world circumnavigation?

  • Gabriel A Petrie

    It looks like the blades “fold-in” orthogonal to their spread position. Maybe you should give the fold-cuts an angle, so that when folded-in, the blades present more of a helix shape, to continue to take advantage of the passing wind.