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In this video a "brim" is placed around a wind turbine and the power generated doubles. A simple static mechanism that doubles the efficiency of a turbine seems too good to be true. Is this a legitimate breakthrough?

Additional links (but they all seem to be to non-primary-source articles) can be found by searching for "wind lens"

  • 2
    This is certainly credible. The mechanism looks similar to the Dyson Fan. Either way, I suspect that physics.sx could answer this question better. – Konrad Rudolph Aug 31 '11 at 13:53
  • Not the Dyson fan, which has no blades in the middle, but certainly similar to e.g. turbofan aeroengines. – DJClayworth Aug 31 '11 at 15:30
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    I think the biggest question here is what constitutes a breakthrough. Is something that provides a signifigant increase in effiency to a very limited and minor subset of the market a breakthrough? I think in order for this to be the case then it would have to lead to an incredible growth in the market share of these small household generators. This is an answer that will probably take a decade or more to really find out. – Chad Sep 9 '11 at 13:05
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    @RikShep it's precisely because it's not scalable, that it's not a breakthrough. Such things have been tried many times before, and the barrier is the mechanical stresses placed on the lens: it simply doesn't scale. And anyway, the efficiency of converting the wind's kinetic energy into the turbine's kinetic energy isn't a big issue, and hasn't been for 20 years. So no, the wind lens is not a breakthrough by any stretch. – EnergyNumbers May 1 '12 at 10:46
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    I would note that ducted fans (for use in aircraft) have been around for at least 50+ years. Therefore, I think calling this a "breakthrough" is rather hyperbolic. It may be a clever application of existing technology, but it's not revolutionary. – Fake Name May 1 '12 at 20:43
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Yes, it appears to be significant and valid.

Update: due to the questions below on scale, I have emailed the author of the paper, Dr. Yuji Ohya, to request his input on any potential issues with the increased size that will be required for industrial applications. Here is the email.


I searched google scholar for the named professor in the video, Dr. Yuji Ohya (see his web page on the Kyushu University site). Searching for him there reveals that he is quite well published in areas of fluid mechanics and modeling/simulation.

In any case, searching "Yuji Ohya lens" brought me to what appears to be his published work on this concept:

Ohya Y., Karasudani T. A Shrouded Wind Turbine Generating High Output Power with Wind-lens Technology. Energies. 2010; 3(4):634-649..

The full text is available for download at that link. Notable quotes from the text follow below.


Abstract:

We have developed a new wind turbine system that consists of a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it. The shrouded wind turbine with a brimmed diffuser has demonstrated power augmentation by a factor of about 2–5 compared with a bare wind turbine, for a given turbine diameter and wind speed. This is because a low-pressure region, due to a strong vortex formation behind the broad brim, draws more mass flow to the wind turbine inside the diffuser shroud.


They begin with an discussion of "nozzles" vs. "diffusers" (pg. 636):

diffuser vs. nozzle


They present the characteristics of their modified diffuser (pg. 638):

modified diffuser


They also provide power generation data for a wind turbine only vs. one fitted with their diffuser/"lens" device (pg. 639):

power data


Here is a description and picture of their experimental setup (pg. 641):

experimental setup


Some summary points about the design (pg. 638):

The important features of this wind turbine equipped with a brimmed diffuser shroud are as follows.

(1) Four-fivefold increase in output power compared to conventional wind turbines due to concentration of the wind energy (“wind-lens” technology).

(2) Brim-based yaw control: The brim at the exit of the diffuser makes wind turbines equipped with a brimmed diffuser rotate following the change in the wind direction, like a weathercock. As a result, the wind turbine automatically turns to face the wind.

(3) Significant reduction in wind turbine noise: Basically, an airfoil section of the turbine blade, which gives the best performance in a low-tip speed ratio range, is chosen. Since the vortices generated from the blade tips are considerably suppressed through the interference with the boundary layer within the diffuser shroud, the aerodynamic noise is reduced substantially.

(4) Improved safety: The wind turbine, rotating at a high speed, is shrouded by a structure and is also safe against damage from broken blades.

(5) As for demerits, wind load to a wind turbine and structural weight are increased.


So, to conclude, it appears as though this is, indeed, valid research with documented results from actual experimentation. Regarding rebuttals, one may need to see if any appear citing this down the road. Honestly, though, as long as someone can replicate the trial, I don't see much to argue with -- it's power collected with and without the device. It either works or it doesn't.

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    While the research certianly seems legit I would think that we should wait until it is inplace and how it works at scale. If it truely is a break through then businesses should start adopting it at least for testing as if it will double their output it will double their bottom line. I dont think it is really safe to say that we can achieve these types of gains reliably across the industry until we see it in practice. I would consider it plausible rather than valid. – Chad Aug 31 '11 at 20:40
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    @Chad: Eh. I'm not such a fan of the distinction. See their paper, section 3.4. They conducted a field experiment and got real world data for their add on and show it plotted against a bare wind turbine. Define "at scale" for me. The question is whether or not this addition has shown significant improvements over devices without it. The answer is, "Yes." The question was not, "How will this scale across "the industry"?" (another term you need to define). – Hendy Aug 31 '11 at 20:55
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    The you tube video seems to at least strongly imply that adding this technology to existing windfarms would improve the effeciency cost effectively. I do not know that what works at a scale of ~1m will work any where near that effectively at 50m+. If it does not at least provide signifigant gains +15% at that scale then its not really a break through as we already knew this worked on small props. – Chad Aug 31 '11 at 21:02
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    A tl;dr caveat might be that the field experiment in section 3.4 describes a 2.5M diameter rotor, which is significantly smaller than what I think of as "industrial-sized" wind turbines. – Larry OBrien Aug 31 '11 at 22:06
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    They are comparing how effective is bare turbine vs same turbine with brim. To make comparison worth anything, they should have compared how effective is turbine with brim vs turbine of diameter of whole brim contraption. – vartec Apr 30 '12 at 22:09
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This technology is not new. Google "Wind Tamer" you will find a US company that implemented this type of funnel technology in the past.

Stating an increase in efficiency due to the addition of a funnel is misleading. Efficiency is typically calculated based on the swept path of the turbine blades. The funnel effectively increases the functional area exposed to the wind and should be included in the efficiency calculations.

The "wind lens" increased efficiency is calculated by accounting for the additional energy captured by the wind lens without accounting for the additional swept area of the lens.

When all is said and done the additional power output of a wind lens system could be duplicated by simply increasing the diameter of the wind turbine blades to match the outer diameter of the wind lens. Both scenarios accomplish the same thing which is increasing the wind turbine area exposed to oncoming wind.

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

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    Welcome to Skeptics! Please provide some references to support your claims. Rather than asking each of the readers to perform a Google search, please do it yourself and post an appropriate link with a description (or quote) or what it contains. Having a ring around the turbine blades sounds cheaper to produce than an equivalently large set of blades. Please provide references to support the claim that they are equivalent. – Oddthinking Mar 21 '14 at 22:20

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