Hi DaveS,

When you say, in reference to an extremely wide VAWT, “but it’s the upwind-downwind depth and slow rpm that saps it”, you comment makes no sense. If anything, the opposite of what you say is true. It is the upwind-downwind depth that permits the wind to speed up before reaching the downwind blades after passing through the upwind blades. So its depth is what makes it more efficient than is possible for HAWT. Its depth does not “sap” it. The opposite is true. Its depth enhances its efficiency. So as far as I can tell, you didn’t understand the concept.

Thanks for wishing the good luck to the VAWT community to disprove “myths” convincingly. But it would be more helpful if you would stop perpetuating those myths by making false statements about VAWT. I realize that you don’t know what is true and false about VAWT because you haven’t studied them, but you might at least try to be a bit skeptical about your assumptions before asserting them.

Did you ignore the Delft data on skewed VAWT?

PeterS

Hi DaveS,

Instead of considering the potential advantages of my new concept, you inform me that testing is the ultimate criterion. Is that how you encourage new ideas? It seems to be designed to discourage new ideas.

My sketch shows a new idea, and it has significant advantages over the similar concept in the patent. That’s what inventors do. They try to come up with better devices. Do you understand either concept well enough to make meaningful comparisons? I wonder if you want to skip immediately from first-concepts to testing prototypes so as to avoid careful analysis.

And although the subject is comparing two VAWT/kite concepts to each other, you switch the subject to insisting that there should be some final, ultimate comparison test between HAWT and VAWT to settle for all time the question of which works better. I wonder why. In any case, you have a serious misconception. There is no such final test possible. That is because both HAWT and VAWT will continue to evolve. New devices may, and often do, overcome the limitations of previous devices. That should be totally obvious. It’s called “progress”. Technology evolves.

Of course testing is necessary. That’s obvious. It’s indispensable. But to insist on testing something as a substitute for understanding it, now that may be just a way to avoid doing one’s homework.

There are cases where something works, but nobody knows why, and so testing before evaluating is reasonable. But those are rare cases.

Just to be clear, when I say “testing”, I’m referring to the final prototype performance testing phase of development, not to the preliminary trial and error testing that is part of refining a device or learning about its basic characteristics.

PeterS

Hi DaveS,

You are making a serious conceptual error. You are assuming that representative HAWT, VAWT, energy kites, and sails can be compared to determine which category is better by testing them, one against the other. That is impossible to do because there can be no single, representative device for each of those categories. Each category is constantly improving, constantly changing. Some devices are best in a particular niche, and not in others. There are dozens of niches. And more importantly, the boundaries between the categories will disappear as hybrids are invented. The Bird Windmill is a hybrid. The Sharp Cycloturbine below a balloon is a hybrid. The Sharp HAWT-Kite is a hybrid. Etc.

The best that can be done is to accurately understand the various technologies in those categories so as to better identify what combinations are more likely to work best. New ones will forever be created. So the advantages will swing back and forth between and among categories.

What is most important is to not exclude the potential of any of the categories, to not become partisans that denigrate the other categories and lie about them. That slows progress and wastes  time on foolish battles.

I think of WECS in terms of evolution. In evolution, there is a concept called “punctuated equilibrium”. All that means is that most of the time, change is very gradual, but once in a while, something comes along that upsets the apple cart, and lots of things change in a short period of time. A new ecosystem emerges. A good example is the Internet.

I showed factual evidence -- in my paper on how VAWT could replace HAWT – that VAWT can be more efficient than HAWT. But then I began to think about how I could prove myself wrong, and that’s when I invented the current version of the Sharp HAWT-Kite. It might be so cheap that it could outcompete my Sharp VAWT arrays, and my Bird Windmill arrays. It’s too soon to tell. But that’s an example of how it is impossible to pick a representative for each category. There is always something new and better coming along, sooner or later. The pendulum of progress swings in unpredictable directions.

PeterS

Hi DaveS,

Thank you for your willingness to debunk myths with facts.

You seem to have picked a particularly good example of false information about VAWT. He gives 4 disadvantages of VAWTs. They are all false. They are all myths. Anyone who has studied VAWT in any depth knows that they are wrong. They were proven wrong way back in the 1970’s, 40 years ago, by the experimental Giromill built and tested by McDonnell Aircraft Company under a DOE contract.

The Giromill was a constant rpm, straight bladed, cycloturbine. It used motors and belts to pitch the blades individually using a computer program and wind sensors. It achieved a Cp of .45. That was the same as HAWT of that time. (HAWT are now at a Cp of .51.) Based on wind tunnel tests, the testers believed that the Cp could be significantly higher, and that the reason that it was not was due to poor streamlining of the parts and their connections. As WWII fighter planes showed, careful streamlining can greatly increase performance. So let’s look at the disadvantages claimed in the video.

1)    VAWT are unable to control the motor speed mechanically. False. The Giromill was a constant rpm VAWT, which was achieved by changing the pitching of the blades so that it could remain at the same rpm over a wide range of wind speeds.

2)    The complexity of the VAWT aerodynamics is so complex that it cannot be analyzed. False. How else could they devise the pitch schedules to automatically control the rpm across a broad range of tip speed ratios?

3)    VAWT are unable to self-start due to low starting torque. False. The Giromill had good starting torque due to blade pitching.

4)    Due to low installation heights, VAWT can only access low wind environments. False. The Giromill was not limited to low installation heights.

This video guy is an ignoramus. His knowledge ends back at the first eggbeater Darrieus rotors around 1970. That is what his four VAWT disadvantages are based on. This guy is quite typical of the people who think that they understand VAWT and don’t. He doesn’t question his assumptions. He doesn’t look for counter-examples.

This guy is perpetuating 4 of the common myths about VAWT. But there are a great many more. If you don’t like calling them myths, then just call them anti-VAWT propaganda, or simply lies. He was duped into believing nonsense, which he repeats.

The main problem with this guy is that he doesn’t know anything about cycloturbine VAWT. Most people don’t, including most engineers. Cycloturbines with infinitely variable pitch control are the future of VAWT. (Some cycloturbines use sub-optimum pitch-schedules [usually cycloidal] due to flaws in their design.) And on the small and medium scale, passive, infinitely-variable pitch-control VAWT are the future. And the best one of those is the Sharp Cycloturbine, for many reasons.

If you wonder whatever happened to the Giromill, me too. It was quite promising, especially for a first attempt. But it was scuttled and no reasons were given. It should have been used for VAWT research on blade pitching. Imagine how much progress could have been made over the last 40 years. It was a precious machine. But it was thrown away. I strongly suspect that the reasons were political, and they may have been unethical. I, along with 39 other inventors, discovered how corrupt the DOE can be.

VAWT research has only recently returned to studying cycloturbines, and most of the research is still studying the cycloidal pitch system of the type shown in the Darrieus US patent of 1931!!!. Only a handful are studying infinitely variable pitch control. My paper on how VAWT could replace HAWT mentions some of them.

PeterS

Hi DaveS,

The Bird Windmill can use 3 basic blade shapes: straight, V, and C. It can also use variations on the V-blade, such as a diamond shape. And it can use streamlined blades, flat-surface blades, or fabric blades with the fabric braced in some way, such as like a conventional paper kite. The blades can be supported at their tips, or at their rocking arms if they have them. Straight blades are best for a blade suspended from poles because they double the swept area. When suspended from a kite, any of the blades work about equally well since there is no altitude restriction and straight blades no longer have an advantage.

The reason that the blades need to be rigid is that, if they are not, the bottom of the blade will tend to fold inward due to lift when the blade is upwind. There may be ways to get around that requirement, but I haven’t yet found one.

I’m not sure what you mean by “no rigid wing possible”. I showed with the Sharp Cycloturbine below a balloon how to launch and retrieve rigid wings, and I’m sure that many more launching techniques will be invented for rigid wings and entire VAWT. Maybe you are referring to just the KiteLab kites.

I’ve already given you what categories that I consider to be reasonable or not for the three devices in question, and my reasons. Your comment does not seem to take what I said into account.

All you are saying is that similarities and differences are arbitrary according to who is looking at them. I reject that. I’m talking about the physical principles involved. You are talking about ignoring the physical principles and focusing on superficialities that are not really distinguishing features -- using whatever categories one likes for whatever reasons.

Feel free, by all means. You can categorize the moon along with blue cheese if you like. But categories that don’t make sense in terms of their physical principles are going to obscure the physics and retard progress. Physics is more than personal opinion. It involves definitions based on observations that everybody can agree on objectively, and fairly consistently, and then refining those definitions as new data emerges. Ignoring facts is counter-productive.

Some people are contrarians who just don’t like to agree. Some people have trouble determining which differences and similarities are superficial and which are more fundamental, so they can’t prioritize them. But those people are unlikely to do good science.

The type of pitch control is fundamental. Rotation vs. oscillation is a fundamental difference. The vertical angle of the central axis is fundamental. Rigid blade vs. soft blade is less fundamental. (The Bird windmill could use non rigid blades if it were mounted like the Flexor, and it would still work better than the Flexor.) The attachment of the tether to the tips or to somewhere else on the blade is less fundamental. Rigidity vs softness is fairly fundamental. The blade material is less fundamental. The color is not at all fundamental. Etc. All of the variables need to be considered and prioritized as best as possible in order to determine what categories are logical. In some cases, it may be arbitrary, but that doesn’t mean that all cases are therefore arbitrary. If you don’t like my selection of similarities and differences, feel free to improve on them, and then we can argue as to which is better and why. If you really want to put all three devices in the same category, just use the category I gave you: cross-flow windmills. Cross-flow windmills are VAWT. Axial-flow windmills are HAWT. The Flipwing is a VAWT. The Flexor is a VAWT. The Bird Windmill is a VAWT.

Consequently, VAWT myths apply to the Flipwing, since it is a VAWT. So when you argue that VAWT are inferior to HAWT, keep in mind that you are claiming that the Flipwing is inferior to HAWT.

PeterS.

Hi DaveS,

I can’t access the website due to Yahoo being a yahoo. I would love to see how the launching is done. Please send me the address.

PeterS.

Hi JoeF,

Good points. The category of “oblique axis wind turbine” (OAWT) is useful and necessary. Thank you. There is a wind turbine that uses an oblique axis. It was invented a few decades ago, as I recall. The shaft is at a 45 degree vertical angle to the ground. The blades (he used two) are at a 45 degree angle away from the shaft, and pointing downwind. In other words, the blades form a 90 degree angle to each other. When one blade is above the shaft and pointing straight up, the other blade is below the shaft and horizontal. As I recall, it worked reasonably well. It was mounted low on a large boat that oriented to the wind. The wind turbine was quite large relative to the size of the boat. I can’t remember what the wind turbine was called, or the inventor’s name. Whether the design would work well as a kite, I don’t know. But I suspect that a HAWT would work better.

Another way to think about the difference between HAWT and VAWT is the orientation of the blades to the central shaft or tether. Blades that are parallel with the shaft or tether are vertical axis. Blades that are perpendicular to the shaft or tether are horizontal axis. This assumes that the shaft or tether is at a roughly 45 degree angle to the ground. HAWT seem more versatile unless the shaft or tether is substantially vertical. And HAWT spin roughly twice as fast.

When a kite sweeps across the wind, it functions like the downwind blades of a VAWT. When a kite flies in circles, it functions like the blades of a HAWT. When a kite flies in a figure 8 pattern, it alternates between functioning like the blades of a HAWT and a VAWT. When a kite flies upward, or downward (constant tether length), it functions like the blades of a VAWT that is on its side. Rotary kites function as cross-flow devices, which means they function like a VAWT with its shaft horizontal. Kites that are mounted parallel to the tether, and oscillate (like the Flipwing), are a type of VAWT. Kites or blade that are mounted horizontal and perpendicular to the wind, and oscillate, are also cross-wind devices, and VAWT.

Tethers can be shaped like a wing, and counterweighted to convert them into Bird Windmill blades, but the tether needs to be substantially vertical.

If the tether is shaped like a blade or a flat ribbon, it can be made to oscillate rapidly due to blade flutter. Around 1975, I made a tiny Fluttermill (a VAWT) that was surprisingly powerful. It used a 5 foot long, narrow strip of paper with the tether taped along a long edge of the paper. It fluttered rapidly and randomly, with different parts of the blade moving in different directions. So the short pull-strokes were random in frequency and length. The windmill was able to rapidly oscillate a heavy horseshoe magnet (constrained by a spring) against a coil of wire (from a 120 volt fish tank pump) to generate a voltage when the wires from the coil were snapped across each other. The “tether-blade” probably weighed a gram or two. A young, healthy neighbor expressed skepticism that such a skinny, flimsy blade could generate any useful power. So I had him hold the bare wires and snap the wires together. He almost jumped out of his shoes from the shock. He became an instant believer.

PeterS

Hi DaveS,

I was asking you for the address of the information of launching kites that you can use for your Flipwing. Could you please send it to me? I can’t access the AWES material.

Thanks.

If you wish to ignore the most meaningful distinctions and to create confusing categories based on secondary, less important characteristics, you will.

As far as I can tell, you have not understood what I have said on that subject.

PeterS

Hi DaveS,

As far as I can tell, you did not understand what I said.

PeterS

Hi Daves,

I have read this before. I have Gipe’s books and he’s excellent on wind power in general. But he is not a technical guy. For example, I explained to him that his description of blade lift in one of his drawings in one of his books was incorrect. He doesn’t have a much understanding, if any, of cycloturbines. His focus is on what works in the marketplace. He has no interest in theory or new VAWT concepts. For example, I sent him a Bird Windmill model blade, and he simply ignored it. He didn’t even try it out. It had no interest for him because it wasn’t being sold as a commercial wind turbine. That is fine with me. He does a good job in general. Most of his criticisms of VAWT on the market are ones that I agree with. I regard most VAWT as inferior to the Sharp Cycloturbine, for a number of technical reasons. His interest is only in seeing a fully tested and marketed VAWT that produces reliable, cheap energy, and that is a valid position to take. He is strongly anti-VAWT and anti-theoretical. Fine. That’s who he is and what he wants.

This excerpt from his 2009 book is one I agree with. His point is that current VAWT are not competitive with HAWT, and that nobody should be fooled by the hype from VAWT manufacturers. I agree. In my person opinion, most VAWT are crap from a technical and cost perspective. But that doesn’t say anything about the potential of new kinds of VAWT. I’m interested in improving VAWT to the point that they are superior to HAWT. And I have shown how that can be done by taking advantage of the unique characteristics of VAWT.

About the only half-truth in his article is the assertion that VAWT require more mass than HAWT. The Bird Windmill demonstrates that a VAWT can be built with even less mass than a HAWT. So that criticism about VAWT is not true about all VAWT. Strictly speaking, as in science, if a single exception to an assertion (law, hypothesis, theory, principle) can be found, that assertion is invalidated. So from that perspective, the assertion that VAWT require more mass than HAWT is a myth. And it becomes irrelevant that most VAWT require more mass than HAWT. So the true assertion is this: “Most VAWT require more mass than HAWT, but not all do.”

As I have mentioned, there are a large number of misconceptions about VAWT on the Internet. They could fill a book. I can’t spend the time to go through them all with you. And worse, when I explain errors to you, you don’t seem to understand them. And if you do understand them, you don’t acknowledge them as errors. For example, you gave me a video that I then showed you contained false statements about VAWT, and why they were false. You did not acknowledge that those statements were false, and that your belief in those statements was wrong. If that is the way you seek the truth, there is no point in arguing technical issues with you. You must be able to concede a point when you are wrong.

It is clear that you have not read my paper, “How VAWT Could Replace HAWT”. A lot of the information on this topic is included in that paper. Check the references I listed. Please do your homework.

PeterS

Hi DaveS and PierreB,

Please explain how Darrieus rotors can be HAWT facing the wind. Are you thinking of an eggbeater Darrieus with its shaft parallel to the wind? Or do you have something else in mind?

PeterS

Hi PierreB and DaveS,

Thanks much for the clarification. Nice patent.

PeterS

Hi DaveS,

Thank you for attempting to paraphrase what I am saying.

You have it partly right and partly wrong because you are over-simplifying. I say that there are many myths about VAWT that are retarding their progress. A myth, as I am using the term here, is a fallacy – a false belief. And it goes further than that. The myths I’m referring to are technological prejudices. Technological prejudices are false beliefs about a technology that do harm to that technology by retarding its progress. I have shown you many examples.

Technological prejudices are analogous to racial prejudices. Racial prejudices are false beliefs about a group of people that do harm to that group of people. For example, “Colored people are below average in intelligence, so we should not waste money on good schools for them.” That is a false belief that is contradicted by a mountain of evidence. But a lot of people still believe it, which limits funding for colored students.

Seldom do prejudiced people believe that they are prejudiced. Instead, they regard their false beliefs as true beliefs, as common sense, so they do not make any effort to look for counter examples that would refute their beliefs. In fact, when counter-examples are presented to them, they dismiss the evidence because they are sure that the evidence could not be true because it does not agree with what they know to be true. They ignore contradictory evidence. They engage in psychological denial. One way or another, they find a way to dismiss contradictory evidence.

I was very surprised to discover technological prejudices. It seems absurd that anyone would bother holding on to a technological prejudice. Physics is physics; what is true is true; what we don’t know, we don’t know. What works, works, and what doesn’t, doesn’t. But beliefs trump logic and facts – even when it comes to technologies.

Here is a technological prejudice contained in your present Email: You state that passive pitch is old hat because kites use it successfully. So you regard the passive pitching of the Bird Windmill and the Sharp Cycloturbine as old hat, meaning nothing new or special. The false belief in your statement is that all passive pitching is the same, or at least of equal value.

I am not aware of any kites (broad definition) that can pitch as cycloturbine VAWT blades -- other than the Flexor, and it does not pitch very well at all.

Consider that power kites will be in the same position that VAWT are now in when power kites start to sell. They will encounter a lot of half-truths, fallacies, and lies that will retard or prevent their acceptance into the market place. For now, energy kites are the next big thing, so some academic research funding is available. That will change.

My personal experience is that I can’t get help from academic researchers to do testing and analysis of my two windmills because even VAWT researchers have technological prejudices about passive pitch VAWT. They have seen some poor performing passive pitch VAWT, so they believe that all passive pitching VAWT will now and forever be poor performers. They simply refuse to look at my evidence that contradicts their belief. They are in denial. (So when I am able to do so, I will try to pursue other channels.) They want me to go test my windmills before they will help me to test my windmills. Catch-22.

You paraphrase me as saying that I discount test engineering to settle speculation about VAWTs. That is partly right and mostly wrong because you missed the point. Eventually, testing, including long-term use, will determine which WECS produce the cheapest energy in each different context (land, water, jet stream, small-scale, large-scale, etc.). And those results will stand until something better comes along. What I’m saying is that there is no single VAWT or HAWT that can be taken as representing every kind of wind turbine in all different contexts. So what exactly would you test? Name them specifically, and specify all of the relevant details, including how much they have been tested. For example, who makes it, how big is it, what does it cost, how much does the energy cost, what wind regime is it intended for, how long has it been in use?  You will find that you simply can’t pick representatives because you can’t make fair matches to compare. I am all in favor of extensive testing and I’ve said so repeatedly. That is not the issue. The issue is that you can’t find the VAWT and HAWT to make a fair comparison. Go ahead and try if you don’t believe me. I’m just trying to save you the time and trouble.

PeterS

Hi DaveS,

You sent me Gipe’s article as an example of criticisms of VAWT that contain myths. I gave you one and explained why it’s a myth, a false belief. You ignored it. That implies that you will repeat the myth even though you know it’s false.

I’m trying to obtain the analysis and testing from researchers that you are asking me for. I can’t get it, at least not yet, due mostly to the technological prejudices I have mentioned. So there isn’t any secondary source information. One wind engineering professor thinks that I may be right, so he wants to do testing, but he has no money at present for graduate students. And Prof. John Dabiri thinks I might be right so he is following my progress on the Bird Windmill, but he developed his own (conventional) VAWT, so he has a conflict of interest. In my experience, most wind engineers want to develop their own devices, even if something else might be much better, such as my two cycloturbines. As one engineer told me when I showed him how to build a far cheaper wind pump, “Nobody wants to sit on somebody else’s egg.” And if people will die as a consequence, nobody cares. Sadly, technology is mostly about ego, not helping people, or even about money.

Since I’ve already mentioned that I can’t yet get help to analyze and test my windmills, you know that already. So asking me specifically for what you know I don’t have, and insisting on only secondary sources, seems to me a slick way to avoid learning. Well done. If you actually believed what you are saying, you would not make positive claims about your work to anyone, but would instead refer them to secondary, neutral sources they could consider more reliable than you.

It actually is a dishonor to you if you perpetuate myths about VAWT that retard their progress. That is especially true for you when the VAWTs also function as kites, which means that you retard kite progress. Nevertheless, thank you for the compliment.

PeterS

Hi PierreB,

Thanks for the photo of the Savonius rotary kite. Yes, there is a big cross-over between VAWT and kites.

Yes, Darrieus rotors do not create kite lift when they are horizontal and perpendicular to the wind. The lift of the blades is in the downwind direction, the same as when they are vertical.

I recommend that rotary kites not be referred to as “flip wings” because some don’t flip at all. The Sharp Rotor rotates smoothly with no vibration because it doesn’t “flip”. If a Sharp Rotor is a flip wing, then a Flettner rotor is a flip wing, and that makes no sense. A more accurate term would be a “cross-flow rotary kite”.

I wish somebody would do a series of tests to determine the coefficients of lift and drag of the various rotary kites. I know from my experiments with gliding models that a Savonius rotor has a L/D of 1, whereas a Donaldson rotor and a Sharp Rotor have an L/D of 2. The L/D, at least, could probably be determined by simply measuring the angle of the tether. Or, the angle of descent of gliding models could be measured.

PeterS

Hi PierreB,

Thanks for asking.

The Sharp Rotor generates lift using the Kramer effect. It is closely related to the Magnus effect. The two effects often overlap.

The Savonius rotor and the Donaldson rotor generate lift due to the Kramer effect too.

The Kramer effect is this: A wing which is rapidly increasing its angle of attack will delay stall. That means that the stall angle is greatly increased, and the lift can be greatly increased. The drag will also greatly increase.

Rotary kites like these typically rotate with a surface speed that is about the same as the wind speed. Their spin ratio is 1.

Notice that when a rotary kite like the Donaldson rotor rotates, one wing surface after the other – the top of the wing -- is increasing its angle of attack. The rotor rotates with the upper part moving away from the wind.

The Donaldson rotor has two wing surfaces. The Sharp Rotor has three wing surfaces. In both cases, the top wing surface is continuously increasing its angle of attack as the rotor rotates. The top surface of a wing creates more lift than the bottom surface. The same is true for these rotary kites. The top surface created much more lift than the bottom surface. The lift can be moderately high but I don’t know the exact lift coefficient for each of these rotors.

If a Donaldson rotor is spun using a motor to create more lift, it will create very high lift like a Flettner rotor. The lift will then be due to the Magnus effect. But it requires a huge amount of energy to spin a two-sided rotor faster than a spin ratio of 1. That is because it acts like a fan blowing air in all directions (except to the side).

In contrast, a Sharp Rotor can be spun at a high spin ratio like a Flettner rotor, because spinning it with a motor requires only a little more energy than is required to spin a Flettner rotor.

Just to be clear, a Flettner rotor is a cylinder with end discs. It creates lift entirely due to the Magnus effect. At a spin ratio of 1, it creates almost no lift, and if the cylinder is smooth, it actually can create negative lift. (At the moment, I can’t recall the name of that effect.) The most lift for the least energy occurs at a spin ratio of 4. There is no limit on the spin ratio or on the coefficient of lift. The best wings with slats and flaps can reach a coefficient of lift of about 3. A Flettner rotor can reach a coefficient as high as 10 without requiring excessive energy to spin it. But above that coefficient, the energy required to spin the rotor becomes excessive. A coefficient of lift of 17 has been achieved in a wind tunnel. But it is not of practical use due to the high power required.

A Sharp Rotor combines the high lift of a Donaldson rotor (at a spin ratio of 1), with the high lift of a Flettner rotor (at a spin ratio well above 1). At a spin ratio above 1, the lift should be about as high as for a Flettner rotor.

In small, model sizes, a Sharp Rotor has an L/D of 2. That L/D should increase as the size of the rotor increases, which is the case for Flettner rotors. Large Flettner rotors has a L/D of roughly 3, and sometimes higher if the aspect ratio is large.

Sharp Rotors do not have any “dead spots” that inhibit self-starting. Two-sided rotors have two dead spots.

The Sharp Rotor does not create vibrations when creating lift because the surfaces do not stall. Two-sided rotors create high vibrations when each surface stalls momentarily.

Sharp Rotors typically have very low torque. But increasing the reverse camber near the trailing edge of the wind surfaces should increase their torque if necessary.

An advantage of low torque is that a brake could be used to control their lift when they are auto-rotating.

PeterS