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Published on July 8th, 2014 | by Mike Barnard


Sheerwind Invelox: All Hype, No Substance

July 8th, 2014 by  

Over the past several years, the Sheerwind Invelox ducted turbine has managed to rack up a couple of million in grants and other investments according to reports and has built two small prototypes. According to its press releases it has a New Zealand distributor and a couple of pilot projects targeted for Dubai and Minnesota.

sheerwind one

It makes the extraordinary claim of generating six times the energy of a comparable wind turbine, but in fact is likely generating about eighteen times less for perhaps ten times the material. Briefly, they propose putting a big funnel in the sky and channeling accelerated wind down to a small wind turbine at ground level.

Sheerwind has also racked up a lot of predictable hype from tech and penny stock sites as well as support from those opposed to actually effective wind generation technologies. Recently however the Sheerwind founder and Invelox inventor, Dr. Daryoush Allaei, co-authored a paper with Dr. Yiannis Andreopoulos, Professor of Energy Research of the Department of Mechanical Engineering of the City College of New York. It’s primarily a computation fluid dynamics (CFD) study but it includes statements in a credible journal about its output from field studies. The combination means that it is worth an assessment of their extraordinary claims to see if they stand up.

Real data comparison

First up, let’s look at their field comparison to see what it says. Apparently they are using a tiny wind turbine from Sunforce rated at 600 W for testing both inside the Invelox funnel and free-standing on the mast.  Since they are capturing much more swept area with their device than the swept area of the wind turbine, it’s at best a disturbingly naive comparison; more on this later.

Importantly, their tested Invelox device per the papers Table 3 is 18 meters (59 feet) at ‘hub’ height while the comparison wind turbine mast is only 10 meters (33 feet), and the wind is always stronger further off the ground. How much of a difference does that really make? Well, if the wind is an average of 4 meters per second (roughly 9 mph) at 10 meters — which is what the Sheerwind paper indicates –, it will be around 5 meters per second (11 mph) at 18 meters. As the energy in the wind goes up by the cube of the velocity, that means the wind energy available at 18 meters is going to be about two times the wind energy available at 10 meters.

The combination of much larger swept area much higher off of the ground means that they are pretending to make an apples-to-apples comparison while actually making a grapes-to-watermelon comparison. They are both fruit, but that’s about it.

Screen Shot 2014-07-08 at 11.31.24 AM

The intake to this funnel in cross-section to the wind is 40 feet by 20 feet (about 12 meters by 6 meters). That’s a swept area of 800 square feet (73 square meters). An actual comparison of value would be to a wind turbine with an equivalent swept area.

But that’s not what Sheerwind did.

Instead, they make a comparison between a device with a swept area of 800 square feet and one with about 28 square feet. That’s a factor of 28 difference between the areas presented to the wind. The wind turbine they compared to fits in the tiniest part of that massive structure, the constricted nozzle on the lower right.

If a conventional wind turbine were scaled up to 800 square feet, it would, all else being equal, generate 28 times more electricity from a given wind resource. Even pretending that putting the small wind turbine at close to half the height is reasonable, Sheerwind is only managing to exceed its capacity by a factor of six if their numbers are to be believed.

But of course there is still more. They have been claiming 600% for years, but what does the paper say?

The results show INVELOX generated 80–560% more electrical energy than the traditional WTGs. P-Day 8 means partial data was collected on the eighth day. The total average energy production improvement of INVELOX over 8 days is about 314%.

So they don’t actually get to 600% at all. And some days are generating less than twice as much energy with 28 times the swept area. On average, they are running only three times the generation according to their own numbers, or nine times less energy generation than a real comparison to a wind turbine with an equivalent swept area would have elicited. And remember that fully two-thirds of that is accounted for by the greater height of their device, the two-times factor shown above for differential wind velocity. An apples-to-apples comparison would likely see eighteen times less generation, requiring an input funnel perhaps eight times larger than a football field to produce the same electricity.

Eighteen times less generation. Not six times more. 

Let’s look at a scale comparison of how deceptive Sheerwind is being:

Screen Shot 2014-07-08 at 1.25.14 PM

Note the vast difference in scale and height of the comparable wind generation devices in the top and bottom picture? Well, that’s just one of the lessons to learn from this.

The second is that it wouldn’t matter if the Sheerwind device generated less electricity if it were a lot cheaper to build. But it won’t be and can’t. The conventional turbine has a hollow metal tower which will use a lot less material than the funnel of the Sheerwind device. And it’s freestanding on its foundation, unlike the Sheerwind which requires a heavy supporting framework. The Sheerwind device will take probably ten times the material and a lot longer to install, as current pre-fab utility-scale wind turbines can be up in under three days.

The third is less obvious. Utility scale wind turbines survive hurricane-force winds simply by pitching their blades so that they don’t catch the wind. The Sheerwind is more of a sheet-metal tent which cannot be feathered. It will have to be engineered to be much more robust than Sheerwind acknowledges to survive high winds. Any production version will be even more expensive than the simple materials comparison that the prototype version affords.

CFD modeling

So the real world data paints a disturbing picture of vastly inappropriate comparisons and hyperbolic inflation of results, assuming that the results are even reported accurately. What about the quality of the computational fluid dynamics? Personally, I only have a rule of thumb for CFD results: they never match the real world. That’s obviously not enough, so I asked an expert for his opinion on the quality of the modelling showing in the Sheerwind paper. He wasn’t particularly complimentary.

He indicated that the basics of tool and model use were okay, but had a bunch of concerns related to the application of the tools and model.

  1. Higher mesh points on the models would have been preferred.
  2. Constant input velocity of wind as opposed to more realistic turbulent flow means the results are inaccurate.
  3. Steady state flow condition without a turbine inside which will lead to “uber-rosy results for any duct or venturi tube without blockage”.
  4. All the CFD was done without a turbine inside which leads to substantially overstated results.

All of these points are possible to do with the tools used by Drs. Allaei and Andreopoulos. Point one requires more computational horsepower than they probably had available. An additional CFD model is required for point 2, but the tools support it.

For those interested in the details of the analysis, it’s available here. Drs. Allaei and Andreopoulos vacillated on commenting on it, originally saying that they would provide a response, then deciding not to and cutting off all communication. The analysis is not published as a critique or rapid response in a peer-reviewed journal, so it is reasonable for at least Dr. Andreopoulos to not respond in detail.

Sadly, this is another case of a paper with obvious and deep flaws being published in a good peer-reviewed journal. Energy is a respected journal, multiply indexed and with an impact factor of 4.686. So how did such a poor paper make it past the fairly high standards of the journal and its peer-reviewers? Well, it’s likely that part of the reason is that this paper didn’t show up in the main journal, but in a special issue, Energy & Environment: Bringing together Economics and Engineering. Special issues have a bulk of studies coming in at roughly the same time, requiring overlapping peer reviewers and as a result quality can tend to suffer. In this case the co-author is from a relatively highly ranked school and has a number of publications in CFD as well (although none pertaining to wind generation), which tends to increase the odds of publication. And so grossly incorrect papers such as this one get published and then are used downstream to provide credibility where none exists. That’s certainly what Sheerwind is doing.

Prior art

Of course, the poor performance of the Sheerwind device is no surprise. The first attempt to accelerate airflow by putting a wind turbine inside of a funnel was done 90 years ago according to Robert W. Righter’s book Wind Energy in America: A History. Yet people continue to invest in this without doing their due diligence. One of those investors has commented at length on prior analyses of the Sheerwind Invelox including my blog post on the CFD report, finally sparking Mike Bergey to comment in return (reproduced with permission).

Concentrators and ducted fans have been proposed and promoted by the dozens over the last 35 years that I have been in the industry. In your due diligence you must have missed Next-Gen Wind, Vortec, TurboDynamX, Enflo, Enco, Ring Turbine, Smart Wind, Wind Cube (Wind Sphere), WindTammer, Sky Wolf, Elena, Catching Wind Power, and OptiWind, to name a few. The fatal flaw in all these unsuccessful attempts to build a better wind turbine is the promoters failure to account for the wind’s ability and preference to go around a blockage like the entrance to a funnel. The operating environment of a wind turbine is nothing like the constraining ducting of a hose or a wind tunnel and that dooms the concept to poorer performance. And the dishonest use of the rotor area instead of the total intercepted area to inflate the calculated efficiency doesn’t change the physics.

For those not familiar with Mr. Bergey, he’s twice past-President of AWEA, served on the AWEA board for 26 years, has manufactured the top-selling small wind turbine for roughly the past 30 years and chaired governmental committees around wind energy. He’s been multiply awarded for his efforts and his direct, ongoing and committed involvement in all aspects of wind generation are second-to-none.

Compare Mr. Bergey’s experience to Dr. Allaei. According to his research publication history and consultancy, he’s an expert on vibration. Like many other ‘innovators’ in wind energy, he has no prior history of any involvement in wind energy. This is so common, that it’s a separate red flag question in my material which aims to inoculate investors against bad wind energy bets. Sheerwind managed to rack up eight red flags based on this sieve, including this statement about conventional wind turbines which is extraordinary to see in a peer-reviewed paper:

They are also expensive, unwieldy, inefficient, and hazardous to people and wildlife.

The inability of devices like Sheerwind to do anything except suck money out of investors’ wallets is well-documented and an ongoing proof of PT Barnum’s axiom.

In summary

Sheerwind makes radically inappropriate comparisons between their long-disproven approach to wind generation and actually useful wind generation. The numbers show that they are likely about eighteen times worse at generating electricity from moving air than a truly equivalent wind turbine would be, and will require an order of magnitude more material to achieve that.

The claims that they make aren’t supported by their own data, and their data is distorted beyond credible defence. Their device will produce much less electricity at much greater cost than conventional wind generators.

Potential investors: stay away. Current investors: don’t expect to see your money again.

(Author’s note: an earlier version of this article had miscalculated the energy difference available in the wind by squaring instead of cubing velocity. That is corrected throughout now.)


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About the Author

is Senior Fellow -- Wind, with the Energy and Policy Institute. He has been a deeply interested observer of energy systems for three decades. His work as a business and technical architect on large initiatives in a variety of domains gives him the systems thinking perspective and stakeholder analysis skills to engage effectively with an area as complex as the grid. He’s regularly asked to peer-review academic and non-academic publications related to wind energy by journals, organizations and individuals. Through the Energy & Policy Institute,, his blog and other venues, he focuses on bringing data-centric reality to bear in policy, siting and social license discussions related to wind around the world.

  • Joseph Kool

    Hundreds of years worth of fossil fuels and we’re toiling with technologies that aren’t ready yet.


    … I was looking for this clearance Mr. Barnard, thank you very much.

  • MT1

    Not to throw another log on the fire, But the bend to turbine distance is too short.

    For air flow to return to lamilar, (smooth, not turbulent) the formula in a minimum of 10 times the diameter. That is 60 feet, not 30. And I’d add some for insurance. At 30 feet the flow instability will rip that turbine apart.

    The top wind speed is an issue too. Water becomes abrasive at 500 ft/sec. With an 18 to 1 area ratio that’s about 26 MPH. So it can’t go above 26 MPH if it’s raining. That is for the sides of the tunnel. Not turbine tip combined speeds. And I’ve seen some 6 ft rotors with the tips completely eroded away. Mounted 10 feet above the ground.

  • John Gnahz

    I personally talked to Dr (??) Allaei a few times, this guy is either a crook, or a total moron. That is all I want to say. Mike Bernard, thanks for spending time writing this article, but you are wasting your time arguing with a crook/moron. :-)

  • Jake Hackman

    I think the point was that it’s more efficient per dollar spent. And was the control wind turbine at a lower height because that’s how high a turbine of similiar cost would be? You’re right that it seems fishy, but maybe by dollar it’s cheaper and a good low speed wind turbine would be good for homeowners.

    • Bob_Wallace

      How could the cost per kWh produced be less than the wind turbines we are now using?

      Can you imagine the cost of building a 3 MW version of one of these things and the massive tower it would take to get it up 80 meters in the air?

  • Rozbix

    The comparison you’ve made is not fair.
    Just think more about the real cost per Kwh for two concepts, man.
    The constructing cost of such structure is nothing to cost of those giants Turbine..especially in poor countries…
    Think smarter.

    • Bob_Wallace

      Sorry, you’re the one who needs to think. Read more carefully and think.

      “those giants” are now producing electricity cheaper than any other source. They are by far the cheapest way to bring new electricity onto the grid in the US.

  • Shaking My Head

    In my community, there are two giant wind turbines that sit dormant month after month. I’ve seen the Sheerwind demos and the founder’s track record is not only impressive, he is a game changer time and time again. Not surprising there is empty opposition from those who fear new technology. And so, one can only revert to illusory techniques and misdirection to discredit Dr. Daryoush Allaei.

    • Bob_Wallace

      How about this, Mr. Head. Why don’t you come back for a visit after a couple of years and let us know how much Sheerwind has been installed and what it’s selling price per MWh might be?

      That would be a fair test to see if you or Mike know the most about what you’re talking about, don’t cha think?

  • Skeet

    I see nothing about grants on or anywhere. Where did you get this information?

  • cmuel

    They have customers, they must be doing something right. No way in hell anyone would pay for something that big if it didn’t work. Even if it is half as good as they say it is an improvement to free stream turbines.

    • Bob_Wallace

      Are you unfamiliar with the dietary supplement industry?

      Ever wonder how many rabbit feet have been sold over the years?

  • Mark Sch

    I think this article does a pretty good job off showing how SheerWinds claims are very misleading. However, I don’t think the analysis from Mr. Bergey should have been part of your analysis, as he develops a product that would compete with SheerWind (if it ever actually gets off the ground). This creates a clear conflict of interest.

    • DR_W

      One major factor being ignored in this analysis is the thermal heating of the funnel and duct. The air column will be heated by solar radiation causing a “chimney effect” which in turn will tend to reverse the flow of air in the duct, at least to the point of impairment.

    • Shaking My Head

      Yes, a clear conflict of interest, rather than objective journalism. This is strike #3 against this article. I pointed out strike #1 and #2 above in response to Edgar’s useful comments.

  • plaintruthforidiots

    “The Sheerwind device will take PROBABLY ten times the material and a lot longer to install,”
    Based on what evidence?

    • Bob_Wallace

      You could simply look at the device to answer that question.

      Now, let me ask you. How much material would it take to position the intake up high enough to grab good, clean air?

      How much structure would it take to make that device hold up to a Force 3 tornado or hurricane with minimal damage?

    • hud

      Look at it.. Just look at it. . Theres your evidence.
      Your name is ironic

  • plaintruthforidiots

    “The intake to this funnel in cross-section to the wind is 40 feet by 20 feet (about 12 meters by 6 meters). That’s a swept area of 800 square feet (73 square meters). An actual comparison of value would be to a wind turbine with an equivalent swept area.” LOL again. No, the ONLY thing that matters is the cost per kilowatt hour, which you strangely seem to be avoiding… If wind turbines with an equivalent swept area cost five times as much as the Sheerwind concentrator over its lifetime, and smaller wind turbines used in it, then maybe the Sheerwind is better? (You will need more than one wind turbine of an equivalent swept area to last as long as the Sheerwind concentrator…)

    • Bob_Wallace

      You are now spamming.

      You’ve made your point. Now let’s see you back up your claims with data.

  • plaintruthforidiots

    Since they are capturing much more swept area with their device than the swept area of the wind turbine, it’s at best a disturbingly naive comparison; more on this later.”
    WTF? This is hilarious. Barnard, you are beyond stupid. The concentrator is a static piece of equipment. It has no moving parts, it requires no maintenance. It will outlast any turbine you place in it. How much does a wind turbine of equivalent swept area cost, how much is the tower for it, how long will it last before needing replacement, so how many will you need to purchase over the life of the Sheerwind concentrator? Three? Five? You have done no calculations and can’t even seem to grasp the basic concept of how this works. I designed wind concentrators which work on the same principle when I was 16, and I’m sure thousands of other people have done the same – you use sails, or buildings designed to concentrate the wind from all directions, into a central area where you place a wind turbine. The buildings were going to be built anyway, you just change their shape and location to maximise the Venturi effect. You have no understanding of the basics of physics, it’s laughable.

    • Bob_Wallace

      And how many of your designs are in commercial production?

      Where can we find your published data which shows how well your concentrators work?

      Where’s your cost comparison to a normal wind turbine?

  • plaintruthforidiots

    How much does a tower for an equivalent ‘swept area’ turbine cost, Barnard? How much does a huge turbine cost, compared to the tiny ones in the Sheerwind device? How much does it cost to perform maintenance on a huge turbine, 100ft off the ground, etc., compared to a 6ft one (or however big it is) at ground level, which can be carried away by two men on foot? Did any of those advantages occur to you? The funnel will be able to last for many decades without any degradation, whereas turbine blades never do, and cost a lot to make.

    • Bob_Wallace

      Look, plain, you’re just tossing stuff out. “A huge turbine, 100 ft off the ground” is simply going to smoke a box a few feet off the ground. If you had read the article you might have some sort of a clue about height and wind speed.

      Best you quit trying to put Mike down. You don’t know enough to be critical.

  • plaintruthforidiots

    LOL. What’s the cost per kilowatt hour, Mike Barnard? That is ALL that matters. A static structure like the Sheerwind funnel structure is going to cost less to build than a turbine of the same ‘swept area’ as you laughably put it… What’s the cost per kilowatt hour?

    • Bob_Wallace

      Where do you get your cost data?

      My guesstimator finds the opposite of what you claim. The funnel stuff has a lot of materials in it compared to a simple tower of the same height and a longer set of blades.

    • hud

      no it isnt.

  • Is it really that bad?

    Doesn’t the technology reviewed here somewhat mirror the operation of a hydroelectric dam? In a dam static fluid at high potential energy is converted to useful energy (thru a turbine) by sending it through a channel at high speed. It does not change the amount of available energy it simply changes its form to something mechanically useful.

    Why do you feel that wind would (or should) behave so differently with a properly designed system?

    I do not have any argument about the higher cost of the structure or the unbalanced energy comparisons in the paper, as you correctly point out.

    If the accepted practice of energy conversion with water is to ‘tunnel’ it (static –> high velocity) then why must it be the accepted practice of wind to accept only the air speed provided by nature?

    • Bob_Wallace

      Mirror a hydroelectric dam? Not really.

      Dams create power by entrapping water and creating “head”, the turbine is mounted at the bottom of the dam with lots of pounds of water concentrating energy at the turbine level. Air is not as dense as water.

    • plaintruthforidiots

      Well said. Barnard is a cretin who can’t even think outside the box. Obviously using cheap, static funnels, or sails, is a very efficient and COST EFFECTIVE way to concentrate the power of the wind onto a small, cheap wind turbine. He doesn’t like it because his brain doesn’t work well enough to even think of things like this…

      • Bob_Wallace

        Name calling is a violation of site rules.

        Best you step back and see if you can post in a more adult fashion.

    • hud

      No. Hydro electric gets its power from gravity. This gets its power from speed. THis stupid big contraption funnel tower thingy is exactly as bad as the author of this article says it is. I wasted a year of my life building, designing, testing funneled wind systems. Every singly thing the author of this article says is right. If you disagree, its because your missing something. .

  • Shazux

    I don’t see a problem in publishing something like this. the journals are meant to publish new ideas and let the other researcher to discuss it (like how you did here). To say that only the papers that support my idea have to be published can be regarded as totalitarianism. In this respect, I would like you to invite you to have a look at the history of laser development. an innovation which was described as toyish, useless or at best ineffective nowadays cant be separated from the current-day modern applications.

    • Mike Barnard

      Peer reviewed engineering journals are expected to have high standards and filters in place to prevent self-serving and deceptive material from being published. In this case the review process failed to correct the paper and then published it lending credibility to something which has none. Pointing that out is not totalitarianism.

      • plaintruthforidiots

        What ‘corrections’ did the paper need? They compared the turbine outside the Sheerwind structure to one INSIDE it. And you didn’t like the result, because you don’t even understand how the Venturi effect works, presumably.

        • Bob_Wallace

          You didn’t read well enough.

          The box intake was higher than the pole mounted turbine.

          “Importantly, their tested Invelox device per the papers Table 3 is 18 meters (59 feet) at ‘hub’ height while the comparison wind turbine mast is only 10 meters (33 feet), and the wind is always stronger further off the ground. How much of a difference does that really make? Well, if the wind is an average of 4 meters per second (roughly 9 mph) at 10 meters — which is what the Sheerwind paper indicates –, it will be around 5 meters per second (11 mph) at 18 meters. As the energy in the wind goes up by the cube of the velocity, that means the wind energy available at 18 meters is going to be about two times the wind energy available at 10 meters.”

          It’s a research design flaw which invalidates their data.

  • Edgar Roock

    Not sure about your efficiency calculations. What is the industry standard to compare wind turbine devices? The swept area as you say, the output per unit as they say, or perhaps output per cost? It looks like everybody uses the measures that support their agenda. Can we have a common ground here?

    • Shaking My Head

      I am finding it interesting that Mr. Barnard, who (#1) has clear bias to support current technology and poke holes in any game-changing technology that might displace the inefficient, ugly wind turbines, (#2) only responds to comments that are favorable and support his article. I too would like to learn, what is the industry standard to compare apples to apples? This seems like a classic case of misdirection, and the illusion of fair journalism. I was listening, and looking for truth in this article, but I’ve found these two strong strikes against it.

  • Calamity_Jean

    In addition to being inefficient, the darned thing is just freaking ugly. And people complain about conventional wind turbines!

    • plaintruthforidiots

      So it’s “inefficient”, is it? According to whom? And it’s “ugly”? Really? And conventional, bird killing wind turbines aren’t?

  • Mike Barnard

    My motivation is a bit simpler. We are a very rich world and can easily afford a couple of million here or there wasted on nonsense like the Invelox.

    My problem is that these ‘innovations’ provide ammunition to those opposed to broad deployment of current wind energy, which is extremely effective and getting more effective annually through incremental innovation. People like Bjorn Lomborg — who paid himself $750K last year according to a Guardian piece, mostly from fossil fuel sources such as the Koch Brothers — are advocating spending on research and development instead of spending on deployment.

    There’s a subgroup of Republicans who are trying to get the party to stop denying the science of climate change, but their solution isn’t to put in place technologies that work, but to invest in R&D instead.

    When organizations like Sheerwind, Ogin, Saphon, Makani and other money wasters get fawning press — whether they slam mainstream wind generation as Sheerwind does in the process or not — it feeds into the ‘don’t deploy, do more research’ mantra.

    • Hans

      “There’s a subgroup of Republicans who are trying to get the party to
      stop denying the science of climate change, but their solution isn’t to
      put in place technologies that work, but to invest in R&D instead.”

      Which brings us back to square one. Because this is the same thing what they did first with climate change. A lot of the funding for climate change research was established by the republicans, with exactly the same aim: let’s do more research to buy time.

    • Shaking My Head

      At least deploy current technologies that actually work, while new technologies develop and displace those that don’t.

      • Bob_Wallace

        Where’s the data that convinces objective people that this Sheerwind turbine works?

  • Offgridmanpolktn

    Mr Barnard,
    Thank you for this and your other analytical breakdowns of the feasibility of these ‘improvements’ to the wind energy sector.
    As a retired engineer just a view of the diagrams provided with their initial paper make it doubtful that the added infrastructure would be economically worth the claimed benefits.
    But for all those without my background you are providing very valuable input and so if they should fail to voice their appreciation I wanted to at least show mine.

    • Mike Barnard

      You are welcome Richard. Thanks for letting me know.

    • Matt

      A double “Hear! Hear!”

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