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Clean Power Experimental "isocontours" data show the mean streamwise velocity along the center line of a scaled wind turbine array.
Image Credit: J.Newman/RPI

Published on October 30th, 2013 | by James Ayre

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New Insight Into Air Flow Patterns Of Wind Turbine Arrays

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October 30th, 2013 by
 
In a somewhat surprising new discovery, researchers from the Rensselaer Polytechnic Institute’s Department of Mathematical Sciences have found that changes in air flow patterns within wind turbine arrays can occur that result in wind energy becoming available from a rather unexpected direction — from below.

The finding was made while the researchers were modeling how variations in air flow patterns affect the output power of wind turbines — work which was being done to remedy the fact that most wind turbine array studies have overlooked the fact that important airflow changes occur inside the array, according to the researchers.

Experimental "isocontours" data show the mean streamwise velocity along the center line of a scaled wind turbine array. Image Credit: J.Newman/RPI

Experimental “isocontours” data show the mean streamwise velocity along the center line of a scaled wind turbine array.
Image Credit: J.Newman/RPI

“We discovered that a typical measure of the significance of flow changes was rather deficient,” states Jensen Newman, co-author of the new paper and a graduate student at Rensselaer Polytechnic Institute’s Department of Mathematical Sciences. “Inspired by a desire to describe the flow experienced by realistic wind turbine arrays in greater detail, the team created a model of how flow affects wind turbines’ output power.”

The new model provides a more considerably more accurate representation of the magnitude of the changes that occur than previous models have. “It shows that in addition to energy being made available to the turbines from above, energy is also transferred from below,” Newman explains.


The American Institute of Physics provides more:

The tools and methodologies developed by the team for calculating changes in the flow can now be applied to other studies — for any type of flow with a repetitive pattern. Since they were also able to show that energy comes from below the rotors, it may be possible to exploit this by developing wind farms that draw more heavily on this previously unidentified source of energy.

The researchers are now planning to continue this line of investigation by expanding the scope of the research: “We’ll apply this analysis to the case of two-bladed vs. three-bladed turbines to identify the critical differences in flow patterns and how these affect turbine power production,” Newman states. “Similar analysis will be performed using much larger turbines to examine how the physics discovered here scale with turbine size so that the extrapolation of the results to full-scale wind farms can be better understood.”

The new findings were detailed in a paper just published in the journal Physics of Fluids.

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.



  • Dave2020

    Where are the demonstration spots? – There’s one in the Mediterranean and the Chinese are working on VAWTs too, but the missing killer app is energy storage, which would displace the cost of over-capacity. The secondary component of my design is using a wave energy converter to stabilise the wind turbine. Installation, O&M and decommissioning are major cost factors for HAWTs offshore. The special vessels used at present would be redundant.

    http://www.windpowermonthly.com/article/1165176/2MW-vertical-axis-prototype-construction
    “Vertical axis turbines have prompted mixed views when compared to a classic horizontal axis turbine. Indeed, Nenuphar CEO Charles Smadja said that based on performance alone, horizontal axis turbines would always be superior to their vertical axis equivalent.”

    However, Smadja believes that vertical-axis turbines come out on top in terms of cost of energy and installation. The low centre of gravity makes the machine more stable and minimises the gyroscopic effects.

    And, although the highest point of the turbine will be 105-metres above sea level, the substructure of the platform will only be nine metres under the water. Taller horizontal turbines are as much as five times deeper. (or, in the case of ‘Hywind’, over ten times deeper!)

    The HAWT is simply not suited to off-shore use – wrong design premise, period.

    Stubborn dismissal of disruptive technology is the norm in industry.

  • Dave2020

    This far more significant research concludes that there is a great deal more to be gained from exploiting air-flow patterns around VAWTs, so how about a link to this related post Zach?

    “VAWTs have a much smaller footprint than their much more common horizontal axis counterparts and can be spaced much closer together. They are also slimmer and aren’t nearly as tall.” (They’re also cheaper to build and refurbish)

    “The global wind power available 30 feet off the ground is greater than the world’s electricity usage, several times over,” (Not to mention 30 feet above the surface of the seas and large lakes!)

    Read more at http://cleantechnica.com/2011/07/14/caltech-vertical-axis-wind-turbines-boost-wind-farm-power-efficiency-10x/#d3WQLWR3LfBl1fYB.99

    “Minimizing the space between VAWTs and having each turbine turn in the opposite direction of its neighbors minimized the amount of drag on each.”

    Embrace the future – floating VAWTs incorporating energy storage before-generator – you know it makes sense.

    • Matt

      Dave, VAWT so far have fallen into that “just around the corner” dream space. You see lots of “cheaper”, “easier to build”, etc. But no one generating much electric from them. If 1 VAWT cost 30% to build as the common horizontal; but I need 10 to get the same power it isn’t cheaper. If VAWTs produce power at 1/2, 1/4, 1/10 of common turbine; then where are they? Where are the demonstration spots?

      • Bob_Wallace

        Over 200 large VAWTs were installed back in the early days of wind farms. It was an evolutionary branch that died.

        Every few months someone tries to reinvent VAWTs. They create pretty art work. Never seem to create an convincing performance data.

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