Sheerwind Invelox: an informed look

Recently, several people have brought a published paper by Dr. Daryoush Allaei, inventor of the Invelox ducted wind generator, to my attention. Here’s the opening statement of the published paper to get a sense of why it might be worth questioning:

A new concept in wind power harnessing is described which significantly outperforms traditional wind turbines of the same diameter and aerodynamic characteristics under the same wind conditions and it delivers significantly higher output, at reduced cost.

The paper makes the following claim:

Fig. 10 shows the daily energy production improvements of INVELOX with respect to the traditional WTG system. 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%.

This is an extraordinary claim. Modern horizontal axis wind turbines achieve 80% of Betz’ Limit. 80% more energy would imply exceeding Betz’ limit by an extraordinary amount, and 560% more electrical energy would imply exceeding the total energy available in a volume of wind by a considerable amount. Extraordinary claims require extraordinary evidence.

I’ve written briefly about the Invelox before in my ongoing assessment of good and bad bets in wind generation innovative technologies. The Invelox didn’t fare well:

This product and company score eight out of thirteen red flags. They’ve racked up a couple of million in grants and investment as well, and are still getting press as if they were somehow promoting something that hadn’t been failed 90 years ago per Robert W. Righter’s book “Wind Energy in America: A History.”

The odds: bad bet

However, that assessment is a fairly straightforward set of thirteen questions useful in identifying red flags about new wind generation technologies based on fairly quickly assessable items such as claims to exceed Betz’ Limit and principals with no backgrounds in wind generation.

The Sheerwind had never made any of their data and assessments public, so there was no meat to chew on, just hyperbolic statements in the popular press not dissimilar to the oddly aggrandizing statement that opens their paper. This published paper finally provided the meat.

There was a challenge however. Most of the paper deals with computational fluid dynamics modelling (CFD), an area where I don’t pretend expertise, but merely know a couple of simple rules of thumb which are useful. The paper was developed with a Professor of Energy Research of the Department of Mechanical Engineering of the City College of New York, Yiannis Andreopoulos. Thankfully, one of my regular, if anonymous, correspondents is an expert on CFD having done helicopter blade design CFD studies, as well as using CFD to assess wind generation approaches. He prefers to fly under the radar personally, but agreed to let me publish his thoughts on the paper with the proviso that I position them as a set of questions related to the paper, as if he were peer-reviewing it.

All content between the dashed lines is from my correspondent. I’ve edited his emailed remarks slightly for minor typos and formatting, so assume any errors were introduced in this process and are not attributable to him.


1. CFD Tool Assessment/Methods used for Invelox.

ANSYS and COMSOL are generally accepted tools for CFD analysis. Much of the effort in CFD revolves around screen-mesh sizing (higher meshing results in higher accuracy of estimation), method used for CFD (this is the actual aerodynamic priniciples expressed formulaically in code) and parameters set for high-speed computing (eg, wind-speeds, mass flow rate, surface friction, heat dissipations, etc). Generally a RANS solver (Reynolds Averaged Navier Stokes) is used to handle the high powered aero calculations which was used in this study.

Good things about the approach: ANSYS and COMSOL are excellent programs to use for CFD and the method – RANS — is standard. They also used Lewis Panel Method for axisymmetric potential flow modelling. That’s fair to do. A turbulence model was used, k-epsilon, which is very commonly used. So nothing crazy there, but I would have used the Spalart-Allmaras turbulence model, because k-epsilon is simplistic and has a host of uncertainty build into it. As far as the meshing is concerned they did model up to 3 million points, so that’s fair, but a higher point mesh for this machine (simply the size of it) would have been preferred.

Not Good: 

a. Constant input velocity. Bad simulation. Real wind, close to terrain boundaries (ground) is erratic; it is not constant generally. The CFD should have been modeled with Spalart-Allmaras to include in the parameter turbulent free stream flow field with shifting wind-speeds and cross-winds for the site of the turbine. Although Betz also used constant velocity and pressure distribution across the actuator disc in his test, this is an ideal and never replicable for real-world operation. ANSYS and COMSOL are designed to check fluctuating input velocity and it was not setup to do so based on this report.

b. Steady state flow condition without a turbine inside is also bad for this CFD. And that is noted in the report for the CFD test in ANSYS and COMSOL. This will lead to uber-rosy results for any duct or venturi tube without blockage (prop, actuator disk, etc). They basically modeled air flowing real fast at a constant speed through an empty tube with the ground helping out for the concentration effect. Red Flag. One must do the opposite for 3-D simulations like these.

c. All the CFD was done without a turbine inside. From the report:

The CFD results are based on a steady-state formulation and therefore the model does not include the unsteady motion of the INVELOX system or turbine. Furthermore, these simulations did not involve any rotating turbine. The only meaningful comparison between CFD and experiments (i.e. field data) are the velocity distributions, speed ratios, and mass flow rates in the absence of the turbine.

At the very least, they should have used a screen mesh to model the rotors, and to provide pressure drop references for the rotors. I would accept that as a substitute for rotors. But if they are running ANSYS, it would have been wise if they had actually modelled spinning rotors in the CFC because ANSYS is set up to do that. That’s what ANSYS does. It tells you what to expect when you tell it what it is actually solving for. Red Flag.


2. Field Data Comparison to CFD Analysis

From the report:

In order to compare the field data with those generated by the CFD models, we collected wind speed data when the turbine was not placed inside the Venturi section of INVELOX.

and then in the very next sentence, it says:

Fig. 8a shows the measured free stream and Venturi wind speeds for 24 data sets with Sunforce turbine inside the Venturi section of INVELOX.

This is confusing. But nonetheless, they are presenting real data (or that’s what they call it) that shows agreement to the simplistic and challenged CFD analysis they performed. So I am skeptical based on this statement from the report:

In this paper, a small sample of the results is presented here.

I have no way of knowing how many days (is it 2 years, 1 year) of actual data and monitoring that was done to even begin to determine if the “small sample” size is significant enough to extrapolate. I would say no. The sample size presented in this report of real world data is not big enough. We need AEP and 12 months of data to assess any benefit long-term or short term of this machine. I have no way of knowing if the test data presented for real world results is true or not, since ANSYS and COMSOL were done without an operating turbine and power output extrapolated.

The other question I have is they use the phrase “when the turbine is inside the Venturi or Invelox”. Is the turbine actually spinning inside the Invelox. Is it producing power and what is the power output? It could be that the turbine may not actually be spinning inside the INVELOX during this test on Jan 2, 2013, but literally just sitting in there to block flow so they can align the test to CFD analysis (which was done without modelling a turbine). They do not show the wake flow velocity and pressure downstream of the turbine, and that is essential for power analysis. I have too many questions about the turbine ‘sitting” inside the tube as opposed to “operating” inside the tube. Nonetheless, it does appear that they demonstrated mass flow augmentation, which really is no big deal since mass flow augmentation is well known and previously documented over the last 50 years for ducted machines. What I am skeptical about is the actual benefit of mass flow on an operating turbine in the Invelox absent any wake flow data. They say that they did, but wake flow data is not presented and that’s the missing piece to determine if any useful power is being created. It’s capacity factor and LCOE that matter for modern wind energy.

The paper does not show the results for the un-ducted turbine either. So how can any comparison be made by casual on-lookers like ourselves? There is no data presented for the un-ducted turbine. The report data just shows a % increase between Invelox and the micro-wind turbine. What it does show, if the test data is true, although grossly incomplete, is that Invelox just made the most expensive and biggest 600 watt turbine ever. Look at the size of that thing … 600Watts! If they want more power out of the Invelox, then they will have to make a bigger duct system. The un-ducted machine can simply extend its blades at a fraction of the cost it would take Invelox to make their entire duct work bigger to increase power or better yet, just add solar panels to the un-ducted machine and the Invelox is beaten (if their test data isn’t rigged). Take note also, the un-ducted micro-turbine is on a 10m tower and the Invelox is at 18m – 8 meters higher. That’s not a good comparison. The un-ducted machine is also material efficient orders of magnitude than Invelox.

Invelox is still not displacing Big Wind, anytime soon, or anytime at all.


I will clarify something regarding my correspondent’s comments. The appropriate comparison is between the swept area of the duct entry and the swept area of the unducted turbine. That’s an apples-to-apples comparison of generation from a given volume of air. So while my correspondent pointed out clearly the disparity in height of the openings, he only implied the challenge of not comparing actual swept areas.

My correspondent’s extensive remarks are the type of thing that would have been good to have been caught in peer review, especially in a journal like Energy. I had hoped that he would be amenable to submitting them as a published critique in the journal, but he prefers not to.

Based on the weaknesses in their methodology and the challenges with their inappropriate comparisons, I cannot agree with the author’s conclusion that:

INVELOX has a strong potential and is worthy of further development.

In the hopes of stimulating a useful discussion, I am extending an invitation to Drs. Allaei and Andreopoulos to provide their responses to my correspondent’s expert critique here, just as many of the leading researchers in the area of airborne wind energy provided extensive comments on my assessment of the engineering compromises involved in that area of wind generation innovation.





  1. Thanks. I shared this on my Green Brain, Facebook page. We had a little discussion just last week about another company making outrageous claims about their ‘revolutionary’ wind turbine, AND we have a small company in Buffalo, NY that hasn’t built anything, but is making claims that their design will convert 86% of wind energy to electricity, while large wind turbines only convert 1%!! There are a lot of claims like this out there and it’s to be expected that there will ALWAYS be con men who get some investment money, then disappear, or claim ‘they’ sabotaged the work. But the part that gets under my skin is when people who appeal to others’ hopes for cleaner energy, by LYING and bashing the people who really ARE doing something…they spread the lies of the deluded opponents…”OUR wind turbine does NOT slaughter millions of birds…will NOT cause Wind Turbine Syndrome (fake)..etc.” The one I saw recently claimed they had only a few moving parts, while large generators have over 8,000 moving parts!

    1. Hyperbole and overinflated investment hype from not-so-great wind ‘innovations’ is challenging. It feeds into an anti-renewables campaign from people like Bjorn Lomborg and a subset of conservatives to spend millions on research and development instead of billions on deploying what works today. It’s a frustrating and tenacious meme that I’m doing my little bit to stamp out.

  2. Ritwik Sarker · · Reply

    Venting any fluid throw a constricted pipeline increases its velocity correct, one can easily experience that whenever they step on a water hose. Moving into a bit more detailed venturi effect analogy of the invelox concept makes sense perfectly, but, the moment other laws of physics are considered the idea makes a swan dive into a bottomless pit.

    1. Idle air concept as it moves through the vent. Some air sticks to the surface.

    2. The fact that wind loses a lot of energy as the molecules bounces around inside the pipeline.

    3. Put in a generator with any significant production capability and the resistance there is much higher than of any other entry point which would cause the air to simple reroute itself out of one of the entry points with lower pressure. Ofc one could prevent it with a uni-directional valve of some sort [like the one in human heart], but wind would lose energy getting in then as the valve will take up quite a bit.

    4. Barnard I shared a video with you about a working invelox [with a Generator !!!] that sheerwind put on their website. Except by the looks of it, it seems like one of those handheld rotors kids have that are made out of plastic or paper.

    5. What about the exit funnel? Which direction would it be in? Think about the wind blowing from that direction, basically means pressure at entry point and exit point is the same? Doubt Mr Wind would like to go inside in such conditions.

    6. The CEO of Invelox, or Dr..A……….. goes into every other forum changing names and making comments such as “I have people working with me who have been fluid dynamics experts for 30 years”, and goes on flaming anyone questioning Inveox. His typing pattern has given away his identity far too many times. I doubt a person of Logic/authenticity would display such behavior in random blogs/forums.

    I am no expert, nor is Mr Wind my best buddy or anything. But so far, HAWT technology is the most advanced among the turbine types, given the research done for its improvement. And I think it is safe to say, anything shrouded isnt coming anywhere close to modern HAWT’s anytime soon, given more or less equal cost/space taken.

    I wont give my personal opinion on BETz limit or exceeding it, as new laws are made everyday, with every new invention and discoveries [Pluto isnt even a planet anymore]. But considering efficiency, HAWT stands as the undisputed champion today.

  3. Frank Frost · · Reply

    This is very interesting discussion. However it seems Mike Barnard has overreached on his non-technical analysis. Below are a few examples to shed some light on this matter. I assume he is fair and balance and will post this comment, if not, it will appear elsewhere.
    Fact No 1)
    Betz limit has nothing to do with energy production. Betz limit has to do with power coefficient of an energy conversion system, such as a rotor or disk. Betz puts a limit on Power Coefficient (known as Cp) of about 59%, meaning a rotor cannot convert more than 59% of the wind power to mechanical energy that is the rotation of the rotor. Energy is power times the hours in day, months, or years. For example, if the total power of in wind is about 100kW (this is known as maximum power available to turbine) at a given wind speed, and one has at particular speed Cp=40%, this turbine can capture only P=48kW of the wind power at that wind speed. If the turbine runs for 10 hours, then the total energy is E=P*h = 480kWh. If the turbine runs at 100 hours, then E=48,000 kWh. What this means about the data published in the journal paper is that they can generate 300% or 1000% more energy if the traditional turbine was not turning or not ruining fast enough and the INVELOX turbine was turning due to speed increase. In short, increased in energy production has nothing to do with Betz limit.
    Fact No 2)
    In his previous articles Mike was arguing that SheerWind does not show its data and does not allow 3rd party review. Now that 2 peer reviewed papers were published, he is arguing the data. In other words, what Mike is saying is that the three experts (Ph.D. most likely) reviewed each paper (total 6 Ph.D.) and the professors at City College of NY have missed all these points, and Mike who has no or little credential in this area (except writing a blog), he found mistakes in the paper. What am I missing here? Do we even know what peer review means? Is Mike criticizing the two well established journal (ASME and Energy) publications and all those who have reviewed the work? Is good to be skeptic but we all look bad if we start writing things that don’t add up.

    Fact No 3)
    Mike writes the current wind turbines have power coefficient that reaches 80% of the Betz limit. OK, well he really did not say this because he did not know that Betz limit is not about energy production, it is only about power conversion. But let’s say he made a few typos. Is this true that the current turbines reach 80% of the Betz limit. The highest Cp I have seen is about 48% and Betz limit is about 59%. This means Cp is about 81% of the Betz limit. However, what Mike does not know or has neglected to mention is this very sad fact about the current turbines. Current wind turbines reach their nameplate power about 11 to 12 m/s. for example, when they say the turbine is rated at 100kW, it means it generates 100kW power at 11 to 12 m/s, depending on the type of turbine. The reported Cp is only valid at 8 to 9 m/s, and only in a narrow wind speed range. Below chart shows Cp values for wind speed ranging from 7 to 22 m/s for a traditional turbine. It is noted that Cp is about 77% of the betz limit only at lower wind speed when the power has not reached its nameplate power. In the wind speed of 12 to 22 m/s, when the turbine is running at its maximum power (or nameplate), Cp is only 5% to 58% of the Betz limit. It is a good idea to do your homework and learn about Betz limit and the power coefficient before you write on them as if you know it all. If you are a fair blogger, you owe your readers an apology for misleading them. I assume it was not intentional.

    Wind Speed, m/s Cp Percent of Betz Limit (59%)
    7 45% 77%
    8 46% 77%
    9 44% 74%
    10 43% 72%
    11 39% 65%
    12 34% 58%
    13 28% 48%
    14 23% 40%
    15 19% 32%
    16 16% 27%
    17 13% 22%
    18 11% 19%
    19 9% 16%
    20 8% 14%
    21 7% 12%
    22 6% 10%
    23 5% 9%

    Fra Frost

    1. Frank, thanks for letting me know that there is a second published paper available. Please post a link to it for assessment.

      Regardless, you seem to be confusing a couple of things in your response regarding capacity factor and coefficient of power, but accepting the points where you make sense, it’s worth responding. Sheerwind’s extraordinary claims rest on a comparison of the same rotor swept area without a duct and with a duct. However, the appropriate measure is to a wind turbine of the same swept area as the input to the duct, not the point of greatest compression and acceleration.

      Per Figure 2 in the paper, the simplest view of the input area is 20 ft by 40 ft in the models. This is a swept area of 800 square feet. The rotor has a six foot diameter for a swept area of about 28.3 square feet. This is just over 28 times the swept area.

      For over 28 times the swept area and much more material, Sheerwind claims to achieve just over three times the generated energy.

      Scaling up the rotor to an equivalent swept area would require a 16 foot diameter, or blades about 13 feet longer than the modelled device’s. This is a small amount of additional material compared to the duct that Sheerwind has constructed, and would likely result in 28 times the generation of the smaller rotor based on the available power. This is about nine times the claimed increase of the Invelox.

      I will also point out that Sheerwind has stated many times in the past that they achieved 600% increases, while their paper only claims 314% to 560% increases.

      No one is saying you can’t increase generation of a rotor of the same size by making the wind go by it faster using ducting or whatever. What I and others are saying is that you don’t get any value out of doing this because it’s much cheaper, easier and more effective to just to make the blades longer.

      We have interacted before, Frank. I understand that you are invested in this company. But their claims do not stand scrutiny. As I’ve said before, the hard questions you should be asking are of them, not skeptics.

      Note: Fact checking by AndrewNZ in another comment found that I had made a calculation error in my quick remark to Frank in which I had used the diameter instead of the radius in pi*rˆ2. This comment more clearly shows the extraordinarily poor performance for the same swept area that this approach provides. Thanks Andrew.

  4. Frank Frost · · Reply

    Mike, you made me laugh today, thanks for that.

    When I read your line “Regardless, you seem to be confusing a couple of things in your response regarding capacity factor and coefficient of power.” While you made me laugh, yet, it was disappointing that you chose the response you did. Based on this line, I must conclude that you are innocent and don’t have bad intentions, you are simply not educated in this area at all. May I ask what I wrote that made you draw the conclusion? Or is this your debate tactic to change the subject and turn it around. It would have been much more graceful to accept the mistakes you made, but you did not.

    First of all, I was explaining to you that 600% or 1000% more in energy production does not mean Betz limit is violated. Furthermore, Betz limit is related to power not energy, they have different units. But you did not get it or you chose to change the subject. Furthermore, claiming the current wind turbines have power coefficient that is 80% of the Betz limit is simply wrong. Unless you post a power coefficient curve (Cp versus wind speed) that shows 80% of the Betz limit above 12 m/s, I suggest you reconsider blowing people off by this kind of statement. All three facts I wrote you was to help you and your readers. I want to see how you dispute them with physics and data, the very physics and data you have asked others to provide in order to prove their claims.

    Second, all papers are on the SheerWind web site. But you choose not to find it, right? Their FAQ answers most of the questions you raise in a more logical manner. Please read.

    Third, you mentioned I am one of the investors in SheerWind. That is true. Are you funded by the traditional wind group? It seems you do everything, even saying things that don’t make sense at all, to knock down any technology that takes on traditional wind. As I acknowledged I am an investor, you should come out and tell the truth.

    Fourth, if you had any business sense, you knew no investor invests money (particularly true in Midwest USA) unless they have done due diligence on the technology and people. True some companies do not make it, and true SheerWind may not make it, but trust me it will not be for the reasons you have outlined or because of any influence your blog has had. No investor in the right mind, considers your blog and the way you write, credible at all. You cannot compare your blog with two peer review papers and 100s of experts who have gone through the details of the technology and test data, and yet have decided to invest. Well you can, but makes people laugh. I know what you may write next, why the company doesn’t puts such information out. This shows your naivety how the high tech development works.

    Maybe you should check with your secret CFD expert that also made me laugh. If he has good points, he should send them to the editor or the authors. FYI information, scientist and researchers don’t communicate through people like you and blogs like yours or mine, those who do, are not experts. I don’t think your secret CFD expert is anyone but one of your friends, your shadow, or one your friends in traditional wind who is funding your blog. The way you wrote as a “CFD expert” makes me and others laugh. You are entertaining, that I give you.

    Comparing the intake area with the traditional systems tells you how much you don’t understand the system. One of the claims made is that smaller rotors can do as good or better as long as wind speed is increased to a level that allows more output.

    You wrote that they have claimed 600% more energy but the paper reports 314% to 560%. And you are questioning it. Is this the best you could come up with after I showed you how wrong your analysis was? Ok, you can assume their claim was off by small amount. Even if they generate 100% more energy, it makes their system far more efficient.

    Your mentioned what you and others say. With all due respect, who are others? I just wrote that 100s of experts have reviewed the technology, even those who are in the traditional wind, and have come with the conclusion that INVELOX may be the future. You even pick on peer reviewed paper with no respect for the same expert you claim you call on. And it is you and some of your readers (my guess is they are your friends) whose arguments does not hold any water at all. If your blog mattered at all, the company could not have had over 10MW of project delivery in the next two years, massive number of supply chain as partners, a good number of technical and business advisory members, and a large number of investors on their side. If they did not have much to offer, two of the giants would not have called and explore the possibility of investing. Of course, you believe it when you see it, right? That will be your answer. I ask them to send you a post card.

    Let’s allow your readers judge by providing simple answers yes or no to the following questions.

    1) Are you claiming that the current horizontal axis turbines have power coefficient that is 80% of the Betz limit in the range of wind speed over 12 m/s? If yes, please provide source and CP versus wind speed data.
    2) Are you claiming that 600% more energy production violates Betz limit. If yes, please explain what happens when one turbine does not turn and the other turns due to different cut-in speed. Assume the two turbines are horizontal axis turbines with the same power coefficient. This is not about INVELOX, just two standard wind turbines.
    3) Are you claiming that all the experts (over 100 experts) representing the SheerWind investors and those who have reviewed the two journal papers, did not see what you have pointed out?
    4) It is funny your so called expert questions if the data was really measured. This comes from desperation and frustration at your end. Are you seriously questioning the fact that they presented real measured test data?
    5) The paper clearly explains the data was compared with the same turbine subjected to free wind speed. It is in pure English. Did you not read that part?
    I don’t want to go on, I don’t think you really after balanced and fair assessment. But I had a few minutes of laugh, I thought I try to educate you a little.

    Fra Frost

    1. Frank, I’ve engaged directly with Drs. Andreopoulos and Allaei and am expecting a moderately formal response from them in a couple of weeks for this blog. Dr. Andreopoulos has already asserted that exceeding Betz in ducted turbines is in fact what is happening and I’ve asked for clarification regarding intake or compression point.

      To be clear, Invelox has claimed to exceed Betz’ limit, Dr. Andreopolous is claiming to exceed Betz’ Limit and 314% to 560% is not supported in either a Betz’ point-in-time perspective nor actual generation of electricity. It’s unclear what they are basing their claims upon, and the claims are extraordinary. The burden of proof lies with those making extraordinary claims.

      Please understand that your continued defense is interesting but fairly irrelevant.

  5. Mr. Frost, I’m sorry, but unless you and the other investors in Sheerwind can find bigger fools you are destined to lose your money. The Sheerwind turbine will not be commercially successful because the performance will be far less (I predict less than 10%) of the wildly optimistic current claims and the cost of construction will exceed that of the wind turbines of similar output on the market today. Not only is Sheerwind not a breakthrough, its just one more sad wind technology delusion (or scam, TBD) based on the improper application of the venturi principle to wind turbines.

    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.

    I’m sorry you got hoodwinked, but I also hope you don’t find that bigger fool.

  6. Frank Frost · · Reply


    This is getting more interesting as you write. I checked with Professor Andreopoulos and Dr. Allaei. Professor Andreopoulos claims you absolutely misrepresented what he briefly wrote to you and then discontinued writing anymore. Dr. Allaei has had no exchange with you. This is not good that you miss informed your readers. However, it is an indication of your assessment and fact findings. The best thing is to post what Dr. Allaei or Professor Andreopoulos wrote to you to set the record clear.
    Fra Frost

    1. You’ll understand if I don’t consider you a reliable source of information, Frank. I’ve requested clarification and confirmation from Dr. Andreopoulos.

      If nothing is forthcoming, I certainly will publish what he has provided to date.

  7. Frank Frost · · Reply

    Mr. Bergey,

    You are good entertainer, thanks for the laughter you gave me and my friends. We enjoyed it.
    You are a little late to the party. The old technologies have been brought up many times. Where have you been Mr. Expert? I hope this helps you to wake up and smell the roses.

    Also, thanks for expressing your feelings, we like you too but for the reasons that you made me and others who read what you wrote laugh. Calling others fool and yourself smart mouth does not help anyone. Ok, it made us laugh, I give you that. But perhaps you suffer from being one of the Mike’s friends and write such a defensive response that states no fact. I suggest you don’t waste your time to feel sorry for anyone. Rather if you can, please use your knowledge of physics, fluid dynamics, and years of experience to dispute the facts I wrote on Mike’s blog. If you cannot, stop writing nonsense unless you can talk logical and based on physics or science.

    Humor me and write about your massive experience in the area.

    BTW, I am not sure what physics you are talking about, but we are not talking about high school physics here, you might be way over your head. I suggest you swim to shore before you drown.

    The fact that others could not make the wind concentration work, it does not mean it never works. If that was the case, we would never advance science or engineering. Past failures usually bring us one step closer to a solution that works. You need to be a little positive in life or live with facts not angry emotions.

    I hope you don’t feel embarrassed, and I hope I don’t ruin your day by writing this to you.
    Being 35 years in the wind industry is exactly tour problem. You have been in the industry way too long. But no need to panic, if sheerwind concept or airborne concepts (by half a dozen companies in west coast) or other new wind technologies do not work, you guys can continue making the blades bigger and bigger.

    But I don’t think you have any experience, those in the field know better than writing the way you wrote. My guess is you are like Mike’s imaginary CFD expert or imaginary exchange he has had with professors at college or at sheerwind.

    It would have been really helpful to you and would have prevented embarrassment for you if you would have at least read the FAQs on the sheerwind web site. But you decided to just write in rush and defend your friend. Everybody in the field knows about the old wind concentration methods, and if you think you are the only one that knows about them, it tells me you have been sleeping on the wheel.

    In fact, you don’t need to go far, just check FAQs on the sheerwind web site. Below are the links to make it easier for you. Don’t get stress, just laugh, life is all about laughter and being happy.

    And no need to feel embarrassed, we all make fool of ourselves from time to time. I do feel sorry for you though since only a few of us manage to do so when many can see. ——– See the last FAQ

    If you guys only read!!

    The rest of your write up is not worthy of reply but I suggest you send it to one of the comedy channels, who knows, you may get rich by just being funny.

    Fra Frost

    1. Frank, you obviously have no idea who Mike Bergey is or his bona fides in all aspects of small wind generation. I’d suggest a little research might be in order, as your ignorance is quite telling.

  8. Frank Frost · · Reply

    Mike is that the best you can come up with? it was obvious he is your friend otherwise why do you defend him. Why don’t you let him write for himself? You are hopeless.

    I thought your blog says “Be nice, be respectful, be relevant.” are you relevant by calling those who oppose your view ignorant or fool, etc.? the more you write, the better it gets.

    it is best to let your readers get to know who you really are.

    1. Since you seem incapable of Googling, here’s part of Mike’s profile.
      He has twice served as president of the American Wind Energy Association (AWEA) and served on the AWEA Board of Directors from 1981 to 2007. He is a past chairman of the U.S. Export Council for Renewable Energy, member of the U.S. Department of Commerce “Environmental Technology Trade Advisory Committee”, and a past president of the Oklahoma Renewable Energy Council.
      Mr. Bergey is the acting-president of the newly formed national trade association, the Distributed Wind Energy Association.
      He chaired the AWEA Small Wind Turbine Committee for over 20 years and authored the 2002 AWEA “U.S. Small Wind Turbine Industry Roadmap: A 20-year Industry Plan for Small Wind Technology”. He chairs the AWEA Small Wind Turbine Certification Committee, which drafted the AWEA 9.1-2009 certification standard has been adopted in the U.K. (as a BWEA standard). U.S. and Canadian adoption is pending. Mr. Bergey initiated the formation of and serves on the board of the Small Wind Certification Council (SWCC).
      In 1981 he was recognized by AWEA for development of the “For Leadership in the Development of a National Performance Standard for Small Wind Turbines”, which was the basis for the IEC 61400-12 performance testing standard. In 1994 he was recognized as AWEA’s “Wind Industry Man of the Year”


      Frank, your ignorance and unwillingness to learn are embarrassing you.

  9. Matt · · Reply

    What an interesting comment section. I have looked at the data and while not as sophisticated as your comments; mine match up. And yes, I applaud your education of Frank Frost on Mike Bergey (the imaginary wind system developer, manufacturer, wind advocate and downright nice guy).

    Fra Frost – Mike Bergey is not imaginary, he is real but alas, I do not think you are or you are one of the poor investors in this scheme.

    Keep up the good work Mike.

    From imaginary Matt

  10. AndrewNZ · · Reply

    Hi Mike (well both Mikes actually!)

    I have been looking at the Invelox paper in the past week – after an enquiry from someone interested in the technology. I am neither a turbine designer or a CFD expert so I accepted the papers results at face value but quickly came to the conclusion that the ducted tower achieved nothing that couldn’t be achieved more efficiently by buying a Bergey Excel (rough calcs suggesting that the Bergey would put out at least three times the energy of an Invelox of this size in the 6.7 m/s wind environment). Hence very good to see Mike Bergey joining in this discussion.

    For Mike Barnard I have a small correction for you – up in the fifth comment you say…..
    “The rotor has a six foot diameter for a swept area of about 113 square feet. This is just over seven times the swept area.”
    Actually you are being too kind. A six foot diameter is an area of 28.3 square feet meaning that the funnel intake is 28 times the size of the rotor.

    There is an interesting calculation in the paper (at the end of Section 3) where they present the effective aperture of the intake and tell us that Ao = 4.4 m2 – I take that to mean that of the whole intake area 800 sq. feet or 72m2 only 4.4m2 is effective. There’s a big efficiency question right there.



    1. Andrew, much appreciate the fact check. Yes, I slipped and used diameter instead of radius in pi*rˆ2. Fixed now in the comment in question.

      That’s an interesting point regarding ‘effective’ intake as well. That’s like saying that of the swept area of a wind turbines blades, only the outer quarter should be considered.

  11. Frank Frost · · Reply


    Well, it seems your defense is no longer physics and logical analysis that you so pretend you have, rather bio of your friends has become your defense. Maybe your friends should stop calling others fool and write something that make sense, if they are capable of doing so.

    It appears you change the rules to fit your responses. If it is time to show off bios, why don’t you go and look at the bio of the management team, board of directors, technical advisory board, business advisory board, and the technical background of over 30 supply chains that are listed on the invelox web site. For example, check out the bio of the former CEO/Chairman of Xcel Energy, former President of NSP, and former CEO of RES America, CTO of IBM, etc. and the list goes on. Next put your bio and your friend’s bios on one side of scale and see if your bios even mean anything at all or not. I know what your response is, all these experts are fool and you know something that no one else knows. When you started to dispute two peer reviewed journal papers, one of which was reviewed by scientists and engineers at NREL, then your argument becomes meaningless. All you had to do was read and find out who the organizer of the ASME paper was. Maybe you need to find someone with a longer bio to support you.

    It is simple, instead of changing the rules and showing off bios of others, simply answer the basic questions I raised. Hummer me and correct my charts and logic. How come you have not yet? I know you are working hard to make your blog relevant, but believe me it has no value except making serious people laugh. Same goes for your primitive so call overview of airborne wind turbines.

    By the way, for you and your mathematician (Andrew) in NZ, I have no clue how he or you did the math, but you both are wrong. It is not worth making correction.

    Finally, I read your blog in airborne wind turbines, it is interesting what one of the comments says and what your response is.
    I like this line from Mark D.: “– well, it’s obvious to me that you aren’t a system analyst who has been working this research topic. That’s OK, as long as you don’t claim to know the answers – but essentially you do….”

    Part of your response: “….. I would be pleased to improve the framework I’ve suggested with you to make this a peer-reviewed contribution to the discussion, and ….”
    Since when you believe in peer-reviewed contribution? I know, since it is in your favor.

    Mike Moor makes good comments on your airborne story. I suggest you all read it.

    Fra Frost

    1. That you don’t recognize the relevance of Mike Bergey’s resume to the authority of his comments says even more clearly that your mind is closed and that you are merely trying and failing to shoot the messenger. Pity you invested so much as you will just lose it.

    2. AndrewNZ · · Reply

      Hi Frank.
      It is worth you getting a clue about how I did the math and it is certainly worth making a correction if there is one to be made. The only bit of math Mike and I had in common is fairly simple – I’ll set it out more clearly and you can let me know what I have wrong.

      Fig 2 of the Allaei & Andreopoulos paper shows the dimensions of the Invelox structure. The venturi (where the wind generator sits) has a diameter of 6 feet (radius 3 feet) Area = Pi x 3 ft^2 = 28.3 square feet.

      The omnidirectional intake has overall dimensions of 20ft high and 40 ft wide, hence for any random direction that the wind approaches the intake has a face area of 20 x 40 = 800 square feet.

      The ratio 800 to 28.3 is 28. I do acknowledge that whenever the wind is coming in at the desired 45 degrees to the fin orientation the face area is a little smaller = sqrt(2) * 20 ft * 20 ft = 566 sq ft and the ratio is then 566/28.3 = 20.

      So – for the cost of building a structure that takes up at least 20 times more sky (not to mention the tower to support it) the turbine yield improves by 3 times. This can only be an economic proposition if the entire tower structure can be built for less cost than a conventional wind turbine with 3 times the swept area of the venturi throat (so 85 sq ft or 10.4 feet diameter).

      So – what is the tower projected to cost?


  12. WindyCity · · Reply

    In general, I appreciate the premise of the original article. I do not have confidence in Sheerwind’s claims and it is refreshing to see some debate about them. We do, however, need to clear up this issue about the Betz limit.

    In my experience following the Sheerwind folks, as soon as someone says something inaccurate about the Betz limit, they denounce the other person’s technical competence and declare victory. I would ask Frank to please apply some professional courtesy to those you communicate with, including inadvertent errors which to not necessarily debunk their main thrust of their argument. This is raising the straw man and is a childish debate tactic we should all do well to avoid. You will notice that no one on this comment board has denounced your intelligence merely because you do not write or spell very well. Let us all be gracious toward each other and keep the focus on the things that have some bearing on the topic being discussed.

    To Mike (the author), Frank is right that you should not compare Sheerwind’s claim of hundreds of percent improved energy production over “ordinary turbines” to the Betz limit. Forgetting for the moment that Frank’s statement, “Betz limit has nothing to do with energy production” is a gross oversimplification that implies a lack of formal education in these matters, the reason is that Sheerwind’s numbers for improved energy capture are for predominantly low and varying wind speeds. It represents experimental data not so easily compared to the Betz limit. The percentages could be compared to the Betz limit if for each timestep during the experiment the velocity and density over the appropriate physical area were known. One could then calculate how much energy a theoretical machine with Cp = 59% for all wind speeds would have produced and compare the Sheerwind machine to this value.

    It is entirely possible for me to build something for $300 in my garage that achieves many hundreds of percent energy capture over mainstream wind turbines for wind resources where my low cut-in speed results in my turbine often running while the industry’s darling is sitting idle. This does NOT mean my turbine is cost effective or worth investing in, it is just a matter of me tailoring the test to achieve the desired results. This is of course the mainstay of good salesmen peddling bad products – choose the terms of the contest so that you always win. I think that time will tell us if Sheerwind is offering a good product, but the way investment seems to be leading, not lagging, the hard facts implies that whatever their product, the salesmen are good.

    My problem with Sheerwind’s claims is not one of exceeding the Betz limit per se, it is more to do with Sheerwind narrowly discussing only certain performance characteristics and comparing them to “ordinary turbines” in a naive and highly biased way. I would very much like to see a comparison that goes like this: state the wind resource and choose the best HAWT for that resource in terms of levelized cost of electricity (LCOE). Next, explain what the LCOE would be for a properly designed Invelox machine operating in that very same wind. Feel free to make all sorts of simplifying assumptions such as the cost of interconnection and electrical equipment being equal, no height restrictions (let cost drive the height as it does in most practical applications), choose a year of hourly wind data from a well documented site, etc.

    Any competent developer has folks on staff capable of this analysis. There are plenty of commercial software products to help you out with the HAWT performance. I believe this is the sort of fair and unbiased analysis that would show Sheerwind’s product to be less effective than the status quo.

    1. I agree completely. Which is why my assessment in CleanTechnica, written after excellent comments from a variety of people as well as Frank’s grain-of-truth statements, does not deal with Betz but goes after an apple to apple comparison.

      Please have a look and see what you think.

      1. WindyCity · ·

        I was just sifting through some of the internet articles that are listed on Sheerwind’s site as well as those I could find using Google to see how the comment sections were doing on other sites where the articles were giving a neutral or a positive spin to the company’s claims. I was curious to see if there were other critics and/or other hardline champions out there as well as see how those conversations turned out. What I found makes me think I might be giving Frank a little too much leeway.

        Turns out there is some consensus that our friend Frank is the CEO of Sheerwind. His style of writing, particularly the over-the-top insults delivered with awkward politeness that come out when others disagree with his meandering arguments, seem to support the assertion.

        Here is “Fraforst” taking a familiar approach:

        Below is a link where you find the same person with a new name (Brother Ziba) where the other comment writers seemed to find him out based on his writing style, his presence on many comment boards, and his consistent use of the letter Q instead of the word “question”. One poster even checked personal correspondence with Dr. Allaei and saw the same pattern with the Q’s. I noticed “Fraforst” doing the same thing on the wonderfulengineering article.

        It is funny to imagine a company CEO posting to message boards in secret, trying to drum up support among the plebes. In one sense though, I do understand it. For a guy who clearly believes in perpetual motion, it must be frustrating to deal with naysayers. See Dr. Allaei’s patent application for turbines scooping air from moving vehicles to INCREASE fuel economy. It is just a hop and skip from here to turbines mounted on the wings of planes.

      2. Personally, I don’t buy the Frank Frost = Dr. Allaei theory. There are a couple of Frank Frosts in Minnesota and perhaps a dozen in the midwest in general. There have been Frost’s there for over a century. It would be a bit absurd of Dr. Allaei — who does have an academic publication history unrelated to wind energy in the area of vibration of industrial equipment — to false front with such an uncommon and easily checked name.

        I’m fairly convinced that Frank is who he says he is, a local investor in Invelox who just doesn’t understand the space sufficiently to realize how bad Sheerwind’s claims really are. He and I have chatted before in other places where the Invelox has been touted, and I’ve seen the claim that he is actually Dr. Allaei, but the credibility of the person saying that seemed a bit low to me, as did the evidence.

      3. WindyCity · ·

        Mike, I forgot to add that I thought your CleanTechnica article was well done. An article like that was definitely due. I agree with your motivation to try to clear away some of these distractions which can be abused by those wishing to direct funds disproportionately toward concepts that don’t even pass rudimentary tests of feasibility. I am for research, but only in those directions that show promise.

  13. You’d think, at this point, Sheerwind would simply build a full-sized working model with some of the cash from their grants and investors and let it rip. It’ll take a little time to see if what they’re claiming is on the up and up, but that’s all. If it works, they’ll have all the investors they need to expand and grow. If it doesn’t, they can close up shop and move on to the next “big thing”… Why spend money defending and promoting themselves if they KNOW what they say is true? I’ve never understood that.

    Might it be that they have no clue? Or worse, that they do?

Be nice, be respectful, be relevant.

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


Get every new post delivered to your Inbox.

Join 1,229 other followers

%d bloggers like this: