Hi JoeF,

Thank you for including me in the FFAWE club. I very much appreciate the honor. It’s an area of aeronautics that I find fascinating. I look forward to finding out more about the research that has been done by the members of that group. So thank you for the reference.

In celebration and gratitude, please permit me to offer to you, and to others interested in that field, an invention of mine that is not currently of practical use, but which I find it most interesting from a theoretical perspective. It’s another invention, among many, that resulted from my Metatheory of Sailing (book in progress). It is a free-flight, buoyant kite that can sail directly downwind faster than the wind, and directly upwind against the wind, both at the same time! It’s purpose is to prove a principle, called the “Mill-Prop Principle of Sailing”.

Here is some background information: As you know, the Blackbird land yacht (built by Rick Cavallaro and John Borton, and their crew) demonstrated sailing directly downwind faster than the wind (DDWFTTW) at about 3 times the speed of the wind. That kind of land yacht is called a Bauer vehicle, after the first person to demonstrate sailing DDWFTTW, Andrew Bauer (now deceased). The wheels drive the air propeller! This vehicle is difficult to understand because it is based on the relative motion of the ground and the wind relative to the vehicle itself, as the frame of reference. The vehicle derives its power from the medium that is coming toward it faster (the ground) than the other medium (the air). So it functions rather like an upside-down windmill vehicle.

Then the Blackbird was modified to sail directly upwind at about 2 times the speed of the wind. The windmill drives the wheels. Both accomplishments were truly amazing. The engineering theory was not new, but the engineering execution was superb. Sailing that fast directly upwind was actually the greater technical achievement, but most people are more impressed by sailing DDWFTTW. What most people don’t know is that a conventional windmill land yacht, or windmill boat, can advance directly against the wind at only about 0.5 times the speed of the wind. That is because the windmill causes too much drag when the windmill is producing full power. So to go faster, it necessary to operate the windmill at less than maximum power and with the lowest possible lift to drag ratio of the blades. That is very hard to do.

There are still many people, including engineers, who insist that sailing DDWFTTW is impossible. Indeed, I was once censored for a year by a sailing organization for insisting it was possible and that it had been done by Andrew Bauer, an aeronautical engineer, plus writing articles on new ways to do it.

Engineering professors describe those two different ways of sailing (directly upwind, and DDWFTTW) mathematically using different formulae. But I show in my Metatheory of Sailing that the two different techniques are -- at a higher level of abstraction -- the exact same principle. I call the principle “Mill-Prop Sailing”. (It’s one of the four fundamental ways to sail.)

In order to demonstrate non-mathematically (since I’m not an engineer) that sailing DDWFTTW and sailing directly into the wind are based on exactly the same principle, I sketched a free-flight craft that could do both simultaneously (!), thus proving that the two different techniques must be based on the exact same principle (at a higher level abstraction – the level of Mills and Props). A Mill is a driving device, and a Prop is a driven device.

Here is a bit of theory on that subject: Mill-Prop Sailing craft use a Mill to drive a Prop. When a Blackbird land yacht sails DDWFTTW, it uses its rear wheels (the Mill) to drive its air propeller (the Prop). When the Blackbird land yacht sails directly into the wind, it uses its windmill (the Mill) to drive its wheels (the Prop). Wheels can be Mills or Props, depending upon how they function. I won’t go into greater detail because it can get a bit too lengthy.

So here is a sketch of a craft that is a free-flight blimp kite -- with a rigid tether (a tube) that can transmit torque. It uses a windmill (Mill) to drive an air propeller (Prop). In most cases, that would not be a useful/practical combination. But in this case, the free-flight blimp kite is able to sail DDWFTTW, and sail directly upwind, simultaneously! That may seem impossible, but I show how to do it.

What is important to understand about this Sharp Blimp is that each case (sailing DDWFTTW, and sailing directly upwind) uses a different frame of reference, and both inertial (meaning, not-accelerating) frames of reference are equally valid. As Einstein stressed, all motion is relative, and he wasn’t kidding. It takes some practice to learn to think that way. I know that because I struggled to learn how to do it better, and I still find that I need to practice because it is so counter-intuitive. So if it takes anyone a while to understand this sketch, that’s normal.

I hope that this free-flight, energy kite concept (invented in 2008) which is a Mill-Prop Sailing craft, provides a bit of intellectual pleasure to my fellow AWES members and now to my fellow FFAWES club members. Something that it illustrates is that windmills, sailing, and kiting are intimately intertwined and should be treated as variations on a common, underlying theme. To think of them as distinct and in competition can cause us to overlook ways to combine them into useful devices.

I find this simple device to be a lovely little bit of physics because it involves seeing a number of things in new ways. I hope that you enjoy it too.

Please forgive me for immodestly calling it a “Sharp Blimp”, but since inventing is my non-profit art-form, I like to at least sign my work.

PeterS

Hi JohnO,     (Hardensoft International Limited)

This subject interests me because my primary goal is to provide very poor farmers with cheap, clean energy for water pumping, electricity, and cooking by using my two windmills and related devices. Protecting crops from birds fits right in with that goal. Windmill manufacturers search for ways to keep birds away, especially raptors. Airports are of course concerned about birds.

http://irri.org/rice-today/don-t-scare-away-the-birds    Comments from the International Rice Research Institute, but I don’t know how relevant they are to Nigeria..

Here are some bits of information that seem helpful:

http://www.knowledgebank.irri.org/step-by-step-production/growth/pests-and-diseases/birds   IRRI overview on scaring birds away.

https://www.youtube.com/watch?v=PqLT8aKJuNQ   Good overview summary on current bird control by AfricaRice.

The problem with high kites for scaring birds is that they need wind, and so they don’t work on windless days.

http://www.gaskites.com/prod_appli_birdscaring.php  According to this manufacturer of the Helikite balloon ($50 per year), any hovering object will be perceived by birds as a hunting raptor, so it doesn’t even need to look like a hawk. This balloon works for large fields and does not require human labor once flying. Lower cost versions of this might be made locally; I believe that the patent has run out. Any sort of reflective, lifting balloon should work well. So I would test this Helikite first. And if it doesn’t work for some reason, then it could be improved upon.

It might be cheaper to use hydrogen even though it would require filling more often since hydrogen leaks so easily. The hydrogen could be produced locally using a solar panel or a small windmill. A buoyant Sharp Rotor should provide much better lift than a Helikite balloon. Its fast rotations would simulate flapping wings, and it could reflect a lot more flashes of sunlight if it used a reflective material.

Another idea would be a small, ultralight electric airplane/kite, in the shape of a hawk, that flew in high circles on a tether that conducted electricity from a ground mounted solar panel (a few watts) to the airplane’s electric motor. On windless days, once launched, it could fly slowly all day. On windy days, the rudder would be adjusted so that it would fly directly into the wind as a kite, with no electricity needed.

A large, black, tubular solar balloon will heat the air inside of itself and create enough buoyancy to fly. I’ve seen one for sale.

https://www.amazon.com/Toysmith-TSM7991-UFO-Solar-Balloon/dp/B001D21SUK     

https://publiclab.org/notes/mathew/5-29-2012/solar-hot-air-balloons  Do it yourself solar balloons. It could be very cheap (maybe made from black garbage bags). Experiments with the shape could give it some aerodynamic lift to handle wind. A problem with a solar balloon is that it wouldn’t fly near dawn and dusk when birds tend to feed. So manual scaring might be needed at those times.

For scaring away birds manually, and selectively, I would try using the equivalent of a casting rod normally used for fishing, and functioning as a very-long-distance whip. The child could stand in the center of a rice field and reach much of the field with his whip. The pole of the whip might be as long as 3 meters. The whip might reach 50 meters or more in all directions. If a person got good enough, he might use the whip with small bolo balls at the tip to hunt ducks in a rice field. A small weight would be whipped out and back. It might be fitted with a strip of leather to create a whip-cracking sound. Once birds learned that a child in the center of the field meant that they could be attacked from a long distance, the child could be replaced by a scarecrow replica of a child holding a whip. And the child would periodically use his whip to remind the “wrong” birds to stay away. The problem here is differentiating between the beneficial and the harmful birds. And the child should be in school. But if I were a bird, a whip like that would scare the hell out of me.

Another manual option would be to use boomerangs. They can fly high in large circles and would look like a circling hawk to birds. It takes some practice to fly them, but they cost very little to make out of plywood. And they are not hard to make. There are also cheap, plastic boomerangs that work quite well. One throw should scare away most of the birds in a rice field. A throw can be over 50 meters out and back. The record is well over 200 meters out and back.

https://www.youtube.com/watch?v=jPj53n33F7Q   Instructions.

https://www.youtube.com/watch?v=nRCmRAxBKmc   Explanation.

https://www.youtube.com/watch?v=VtpoA9bqrfs    Big ones in unusual shapes.

Here is a boomerang for scaring birds, although that was not its original purpose:

https://www.youtube.com/watch?v=5TXbYd2exU4  Whistles and bangs using bottle rockets.

https://www.youtube.com/watch?v=K9t3-DOevsU   Plastic, three-sided boomerang.

Well, if I think of, or find, anything else that might be cheap and practical, I’ll let you know.

PeterS

Hi JoeF,

Thanks for posting that Fiber Guide.

PeterS

Hi JohnO,

Thank you very much for your warm words and for forwarding my information. I’m glad that we share a concern for poor farmers. Thanks for telling me about the very low wind speeds in Nigeria. Under such conditions, kites may not be of much use, except for buoyant kites, or powered kites, as I mentioned previously.

Since the energy in the wind is proportional to the cube of the wind speed, very low wind speeds are an enormous disadvantage for windmills. Solar PV panels are then a better option. But even under such circumstances, small amounts of electricity might be cheaply generated by an extremely cheap windmill. Here is an example of what I mean:

https://www.youtube.com/watch?v=W85Yr1BwIsw

Small, green, Bird V-blade twists cords of a “twist-cord-accumulator/transmission” (TCAT) to light LED intermittently. The wind speed can be as low as about 1.5 meters per second. The cords are thin shock cords, which are cheap. As the wind speed increases, the TCAT spins the generator more frequently. This blade could be suspended between two trees or two poles or from a buoyant kite. In this case, the TCAT would be located above the blade. In this video, I am using my fingers instead of a TCAT to restrain the generator shaft -- because I had not yet built a TCAT. This blade was made from a recycled, plastic soda bottle. It is exceptionally durable.

https://www.youtube.com/watch?v=JsUUES--QGc

Drill spins TCAT to demonstrate how it works. Moderate torque and very low rpm input yields an intermittent high rpm output.. Inside of the TCAT, small magnets repel to keep the shaft from turning until the torque is high enough to overcome the resistance of the magnets. Then the generator shaft spins at a high rpm to generate electricity. Then the cycle repeats. When the generator spins, the voltage and amperage are always about the same, regardless of the wind speed.

Even wind speeds as low as about 1 meter per second can be utilized if the windmill has strong starting torque. A Savonius rotor can be used with a TCAT. And a cheap Sharp Cycloturbine can also be used with a TCAT because it has strong starting torque, and it spins 4 or 5 times as fast as a Savonius rotor. Here is a video showing how simple a Sharp Cycloturbine can be:

https://www.youtube.com/watch?v=M1BgTKf5vIw

In this case, the windmill is turning gears to spin a DC motor to generate electricity to light the LED. A TCAT could be substituted for the gears to light the LED intermittently. A TCAT is not efficient, but it is extremely cheap, and that makes it useful if it is driven by a very cheap windmill or watermill. These V-blades are made of paper, but they can be made of plastic from a recycled soda bottle. Much larger Sharp Cycloturbines can be constructed. It is a high efficiency windmill. The blades are balanced so that they control their own pitch angle. They do not stall, except when starting. They stall when starting so as to create high drag and strong starting torque.

Horizontal axis windmills could be used with a TCAT too. A recycled automobile fan should work well because it would produce strong torque.

I hope that this information may eventually be of use to you or someone you know.

PeterS

Hi DaveS,

Thanks for your feedback.

Your reference to Leacock’s poem talking about a fellow jumping on his horse and rushing off in all directions is funny. I like that. The Sharp Blimp is indeed kind of like that.

The belief that HAWT are twice as efficient as VAWT is actually a common myth. It stems from comparing inefficient VAWT to efficient HAWT. Actually, VAWT can be more efficient than is even possible for HAWT. I explained that in my article “How VAWTs Could Replace HAWT”. http://www.windpowerengineering.com/featured/business-news-projects/vawts-replace-hawts/

There are a lot of myths about VAWT that keep getting repeated, probably due mainly to Wikipedia. But there are lots of additional incorrect statements about VAWT all over the Internet. The Sharp Cycloturbine, based on relevant research, should have an efficiency of about 45% as compared to large-scale HAWT with an efficiency of about 51% currently. Stand-alone, computer controlled cycloturbine-VAWT are expected to equal the efficiency of HAWT, despite their small amount of extra drag. But efficiency can be misleading because it doesn’t take into account the response of a wind turbine to gusting, and a lot of energy is contained in gusts.

Consider that large, eggbeater Darrieus rotors have an efficiency of about 40%. So if HAWT were twice as efficient, they would be 80% efficient. But the Betz limit is 59.3%. A HAWT can’t be more efficient than that. So it would be impossible for HAWT to be twice as efficient as VAWT. I started collecting false statements about VAWT that I found on the Internet, but there are so many that it would take forever (or at least a book) to explain why they are false. For some reason, it is common for people to assume that they understand VAWT, even when they know very little about them. It’s puzzling. VAWT are quite varied, especially complex (as are kites), and significantly different from HAWT. Part of the problem seems to be “technological prejudices” on the part of HAWT partisans (including people working in the HAWT industry). People, including engineers, tend to take sides, as if HAWT and VAWT were competing football teams. People like to take sides, but that can make for poor science.

Efficiency can also be misleading if applied to energy kites. If measured the same way as wind turbines, most kites are extremely inefficient. But that’s only because most of them have an extremely low solidity ratio and because most have a low tip speed ratio.

You mention that there is a third significant frame of reference in my FFAWE model of the Sharp Blimp: the ground itself moving relative to the surface wind. Seeing the ground as moving is important in understanding a Bauer vehicle, but I don’t see why you think that it is significant in the sketch of the Sharp Blimp. Please explain. In the sketch, there are four main frames of reference: the ground, the lower air, the upper air, and the blimp. In some cases, as for understanding Mill-Prop craft, the craft itself is an important frame of reference (such as a Bauer vehicle on a conveyor belt). But there is no need, in the sketch, to give a complete analysis using each of the four frames of reference relative to each of the other three possible main frames of reference.

You mentioned practical barriers to the Sharp Blimp. No need to worry. It’s not intended to be a practical sailing craft or kite. Its purpose is only to demonstrate the Mill-Prop principle. To do that, it only has to be capable, in principle, of working as shown, even if it doesn’t work well in practice due to engineering problems. My emphasis is on the physics of the device, not on the engineering of the device. If the emphasis were on the engineering, then the device would need to go through the usual long series of iterations and modifications to refine it.

You mentioned communicating with the Blackbird crew. Yes, a lot of people probably conversed with the Blackbird group during their design process. Glad to hear you were part of it. I hope that you were able to contribute something. I added my own two-cents worth. I explained to them why their initial plan of using a drum-winding-a-cord transmission would invalidate their record, but they probably abandoned that design for other reasons. I also explained how to construct a device to adjust their chain drive, but they had already arrived at my suggestion themselves. So I don’t think I was of any help.

You mention that both HAWT and VAWT would become too massive at large scale. I’m not sure what you mean by “large scale”. In the wind industry, “large-scale” typically starts at 1 MW. There are lots of large-scale HAWT. HAWT seem limited to about 10 MW. Maybe that’s what you mean. It is currently assumed that VAWT could be built larger then HAWT because they (straight bladed VAWT) do not have large, varying gravitational loads on their blades like HAWT do. But I show in my article, mentioned above, that the Square Cube Scaling Law works in favor of VAWT much more than HAWT, so there is no need to build gigantic VAWT. Arrays of smaller VAWT could be cheaper than a single, larger HAWT with the same swept area. Assuming it is correct, that observation seems to be not yet understood in the wind industry.

Thanks for mentioning Dale C. Kramer. I found his 2001 patent for a kite pulling a glider. Has he ever managed to fly one, maybe a model? Has anybody managed to fly free-flight kites, even using a buoyant top kite? It should be possible using radio control and a speedboat to chase it. It could be quite fast, even in small sizes. So testing would need to be done in light winds. I’m not aware of any successful flights other than the NASA balloon with a wing-sail suspended far below it, used for maneuvering. But it doesn’t seem to be in use.

You mentioned that you enjoyed the AYRS threads on DDWFTTW, and that Mad Tom was the contrarian. I must have missed that, perhaps because I dropped out of the AYRS before that. I started the controversy about sailing DDWFTTW way back around 2000 when I introduced a new way to sail. At that time, I couldn’t understand how a Bauer vehicle worked. So I got pissed off and decided to invent my own damn way of sailing in all directions faster than the wind. And I did, at least in theory. It’s called “Power Alternating Sailing” (PAS). That first article is only a partial, still incomplete, introduction to PAS. Dave Culp, who you know, generously helped me with it, as did kiter, inventor, and engineer, Theo Schmidt. And around 2004 I published an article on Mill-Prop Sailing to help explain Bauer vehicles. The articles started lots of discussions on the subject of sailing DDWFTTW. I published additional articles and letters on that subject until I was censored for about a year – because the editor just didn’t believe that sailing DDWFTTW was possible, despite the evidence available at that time. Technological prejudice. It’s quite common. In fact, the editor changed the title of my first paper, without my permission, so as to omit the words “faster than the wind” because he was sure that it wasn’t possible to sail directly upwind or downwind faster than the wind.

PAS may eventually be relevant to energy kites. Here is a sketch showing how to use two kites alternately pulling aft (downwind) to drive a boat upwind faster than the wind -- at least in principle, meaning that the physics says it could be done as long as the engineering were efficient enough (minimized inertia, low friction, rapid cycling, etc.). This is a specialized boat intended only to prove a point.

The float/drogue on the right is in the water, filled with water, and almost stationary. The float/drogue on the left is out of the water, empty of water, and swinging forward about twice as fast as the boat is moving forward. The forward movement of the boat is forcing the left float/drogue to swing forward. A switch activated by a bead on the tether of the “off” kite (being reeled in) reverses the half cycle. Then the long arm tips to place the forward drogue/float in the water, and lift the stationary drogue/float out of the water so that it can swing forward. The drogue/floats can fill and empty very quickly because they have open bottoms and an air valve on top. When full of water, they become extremely heavy (many tons) and their mass can resist the strong pull of a large kite. By the time the “on” kite starts to accelerate its drogue/float aft, the cycle reverses. So not much energy is lost to moving the mass of the drone/floats.

This basic design could be further improved and simplified. It is only intended to explain the basic concept. It is one of those crazy ideas that, in principle, would actually work. But the engineering would be quite difficult. Please be aware that it is not intended to be a practical craft. It shows future inventors what is theoretically possible. Most people assume that kites can’t sail directly upwind, much less directly upwind faster than the wind (DUFTTW). But that is just another sailing myth.

PeterS

Hi DaveS,

You regard the Bird Windmill and the Flexor Windmill to be the same invention. To me, they are not. There are important differences. If important differences are ignored, progress may be retarded.

Incidentally, Around 1975, I experimented with blade flutter, and built different kinds of miniature windmills based on amplified blade flutter, called Fluttermills. Amplified blade flutter is the basic principle used by your Flipwings (2009). But I don’t consider Fluttermills to be the same as the Flipwing. There are important differences. I invented Bird Windmill blades in 1976, and began developing them into a low-cost windmill around 2010.

I like the Flexor Windmill very much. But the Bird Windmill appears to be clearly superior. And perhaps for that reason, as I recall, David LaBrecque switched to developing it as a water-current version of the Flipwing, where it might be more competitive. Currently, their website seems to be discontinued, so I assume they gave up on the Flexor.

Here is a bit of background information: My experiments with Fluttermills led directly to the invention of Bird blades (by adding a counterweight out in front of the blade), and I abandoned research on Fluttermills because Bird blades were clearly superior at capturing wind energy.

My experiments with Bird blades led directly to the invention of the Sharp Cycloturbine (by adding support arms for the blades and a central shaft), and I abandoned research on Bird blades because the Sharp Cycloturbine was clearly superior at capturing wind energy.

Over the years, as I learned more about wind energy conversion devices, I began to see that efficiency was not necessarily the best criterion – that the cost of the energy was more important. And also, I suspected that inefficient devices could play an important role in situations where a very low first-cost was critically important, such as pumping water for farmers who earned less than $2 per day. So I took a more serious look at Bird blades, started experimenting again, and I was surprised by what I discovered. And furthermore, I wanted to return to experimenting with Fluttermills because they can be so cheap and easy to make.

So when I recently saw your (KiteLab collectively?) tunable Flipwing, I was very impressed. Using a blade flutter kite suspended from a pilot kite strikes me as an excellent combination that might provide very cheap water pumping. Flipwings include automatic kite control, which is a huge advantage – there is no need for a human to steer the kite.

However, as far as I know, there is not as yet any complete Flipwing system that includes launching and retrieval without human input. Automatic launching-and retrieval is critically important to the success of energy kites. Yet, rather little research seems to have been done on how to build them. If automatic launching systems prove to be too complicated (unreliable) and/or too costly, energy kites will probably not be competitive with small-scale windmills and wind turbines.

You state that Bird Windmills and Flexor Windmills are very similar to your Flipwings. I respectfully disagree. Flipwings do not use the same principle, which is centrifugal spring pitch control. (The type of centrifugal spring is not the same in both windmills.) And Flipwings oscillate instead of rotate -- like they do. So the similarity seems limited to the fact that all three use a single, substantially vertical, cross-flow blade.

However, Bird blades and Flexor blades could probably both be suspended in the same manner as a Flipwing and produce a short-pull, pumping oscillations of the tether like a Flipwing. Although, for technical reasons, I’m not sure if a Flexor blade could do that without mofifications. I do know that a Bird blade could do that because I’ve tested Bird blades where the tether is tipped away from the wind. Self-starting is delayed, but the blade still functions normally as long as the axis of rotation is not tipped too much.

In principle, a vertical Bird blade should be much more powerful than a Flipwing because the blade is typically heavier and moves a lot faster. So for the same size blade, a Bird blade should produce a much stronger pumping force -- at about the same frequency.

But in practice, the advantage of a kite-supported Bird blade over a Flipwing might not exist. That is because the Bird blade is intended to rotate about a vertical axis (or a horizontal axis that orients to the wind). If it is considerably tilted away from the wind, it cannot start easily. But a Flipwing can. So a Bird blade might require a significantly higher wind speed before it could begin to operate. And if the tether angle were too much, the Bird blade would not start at all. If a Bird blade’s tether is tilted into the wind, it can start much more easily. But that tilt is opposite the usual tilt of a kite tether. So my guess is that a Flipwing is better overall than a vertical Bird blade if they are compared by suspending them on the tether of a pilot kite.

However, a horizontal Bird blade (Cyclo-Kite) orbiting with a horizontal axis might work especially well because the pilot kite automatically orients to the wind. The angle of the pilot kite tether would not matter because the axis of the Bird blade would remain horizontal. A technical problem to solve is how to pull the substantially horizontal blade tethers apart to provide the necessary tension on the Bird blade. If that can be solved (perhaps by using two pilot kites pulling apart, or by using light [inflatable?] spacer rods above and below the Bird blade), then the Bird blade would produce its strongest pull downward. So the Bird blade would act to pull the pilot kite downward, and the rising of the pilot kite would provide the short power stroke of the pumping cycle. If the orbit diameter is relatively small, a small Cyclo-Kite can create a strong, cyclic pulling force.

On the subject of short-pull pumping kites suspended by pilot kites, it seems to me that a particularly good kite for short-pull pumping, when suspended from a pilot kite, is the axial flow, soft-kite, looping-kite demonstrated in KiteLab videos. I’m not sure who invented it. (JoeF? You? Or does KiteLab treat all inventions as collective inventions?) It is very impressive. It’s beautiful.

A potentially even better short-pull pumping kite suspended from a pilot kite might be a variation of the axial-flow, single-blade, Sharp HAWT-Kite using a solid wing and automatic centrifugal pitch control based on the T-Rule. When suspended below a pilot kite, the tension in the tether could be used to enable to blade orbit to expand without the need for springs and drums. The extra weight and high blade speed (TSR of 5 or 6) could produce a very powerful short-pull pumping-force. If the pilot kite were a buoyant, lifting kite, perhaps a Sharp Rotor, that would largely solve the launching and retrieval problem because the kite could remain aloft for long periods at a time. But how to insure that the blade would self-start easily would require experimenting. I have some simple ideas for how to do it, and I think it could be done. See the attached sketch of a HAWT-Kite. A couple of thin shock cords could hold the blade perpendicular to the blade tether cords if the axis of rotation were more vertical, as when suspended from a pilot kite. Then another thin shock cord might be able to control the pitch angle of the blade for self-stating. A small counterweight on the other side of the tether might help. Once started, the blade would be quite powerful. I hope to do the experiments when I can, using a tiny blade for safety.

I think that is worth keeping in mind that the Bird Windmill, when suspended between two poles, solves the kite-problems of 1) automatic-launching, 2) automatic-control to achieve a large swept area, and automatic overspeed control (by adding a couple of short cords that cause the blade to feather). As a kite, that makes is quite advanced – despite its relatively low elevation, even when using tall poles to support it – because it solves those three kite-problems using inexpensive materials and a simple construction, and with no need for human or computer controls. So for small-scale, short-pull pumping-kites, it makes a good standard for comparisons. It’s dirt cheap and hard to beat.

PeterS

Hi DaveS,

I don’t mean to be impolite when I say this, but when you say that VAWT are not as efficient as HAWT because they cannot be as high on their tower as HAWT, you are simply stating another VAWT myth while insisting that it isn’t a myth. A VAWT can be made where the straight blades are half above the top of the tower and half below the top of the tower, the same as for HAWT. I built one a long time ago. See the red Sharp Cycloturbine in the attached photo. See it also mounted on a model land yacht that could sailing in all directions including directly upwind. I believe it was the first lift-type VAWT to do so (1978) Here are other VAWT examples that are more current:

http://aquaponicfun.com/step-by-step/wind-turbine/

http://scruss.com/gallery/main.php?g2_itemId=5097 

http://www.windgenerators.cn/500w_vawt.html 

http://www.anew-institute.com/

http://www.alt-energy.info/wind-power/blackhawk-tilt-rotor-vawt-testing-underway-at-the-doe-idaho-national-laboratory/ 

It is also possible to mount VAWT blades such that most of the blade area is above the tower.

https://www.youtube.com/watch?v=jF1XqQ3X3dA 

It is also possible to mount a VAWT completely above its tower.

https://www.youtube.com/watch?v=LNV8WSmkAI4  

http://www.treehugger.com/wind-technology/new-version-aerogenerator-x-10mw-vawt-works.html 

So if your argument has merit, the last three examples would lead you to conclude that some VAWT have a large tower advantage over HAWT, and that therefore VAWT are more efficient than HAWT. In practice, the elevation of the rotor relative to the tower is a minor consideration that does not have much affect on cost or efficiency in most cases. Where it does have an significant effect, the difference favors VAWT. If you still wish to believe your claim, then please show me the research, and please explain how it accounts for all of the examples above that clearly contradict your claim. VAWT are exceptionally varied, so generalizing about all of them is like walking on thin ice.

VAWT do have more parasitic drag and do require more parts moving through the wind than HAWT. But the parts can be simpler and cheaper than HAWT blades. And the parasitic drag is quite low for streamlined blade-support-arms, so there is very little loss of efficiency due to that parasitic drag.

HAWT blades are able to operate at a relatively constant angle of attack, which is an advantage. But VAWT blades sweep across the same wind twice, and the full blade is at the maximum rotor radius, not just the tips, which enables VAWT to make up for their lower tip speed ratio. In other words, both VAWT and HAWT have many advantages and disadvantages relative to each other, which don’t sum to a clear conclusion that one is superior to the other. (I’m referring only to stand-alone wind turbines, because arrays highly favor VAWT.) A number of academic researchers find that computer-controlled cycloturbine VAWT could be as efficient as HAWT. I have shown how VAWT can be more efficient than is even possible for HAWT. If you disagree, then I would enjoy reading your reasoning and your references.

Please keep in mind that better VAWT are still being invented and tested. I’ve tried very long and hard (hundreds of Emails) to get engineers to build and test full-scale Sharp Cycloturbines and Bird Windmills because they do seem to have the potential to produce cheaper energy than HAWT. But perhaps HAWT engineers don’t want to prove themselves wrong. I have only one wind engineering professor, so far, who took enough time to understand them well enough to conclude that they really do deserve testing and analysis. But he has no money because most research money goes to HAWT, the conservative choice. Those two VAWT are especially difficult to understand because of the great many interacting variables, even though they are simple to construct. Engineers don’t find fault with them, they just ignore them. I also suspect that engineering professors wish to avoid being taught by an amateur because it puts them back in the student role which they worked so long and hard to surmount. Not many engineering professors would be comfortable with an amateur teaching them about the physics of passive pitch control.

I try to be as honest as I can with my assessment of VAWT, including my own. Most VAWT have limitations that are not necessary. In that sense, they are flawed or incomplete. Decades of research leads me to conclude the Sharp Cycloturbine is, most likely, the best of all 3-bladed VAWT because of its high efficiency (according to relevant academic research) combined with simplicity and low cost. And the Bird Windmill might produce even cheaper energy due to its extreme simplicity and extremely low cost. Typically, when I wish to present to engineers my technical reasons for my conclusions, in order to obtain help with testing and analysis, I am told to test and analyze it to show that it is worth testing and analyzing. That is the quality of the thinking I encounter among wind engineers – that is, if they will even bother to say anything at all. Most engineers and most engineering professors do not like things that they cannot understand, and they cannot understand my windmills without studying them in considerable depth. Apparently, they begin with the false assumption that VAWT are inferior to HAWT, so they figure, “Why bother?” Closed minds are hard to crack. Technological prejudice.

When you say that the present dominance of HAWT proves their superiority over VAWT, with all due respect, I believe that you are using flawed reasoning. At one time, steam cars were dominant over internal combustion cars. At one time, incandescent light bulbs were dominant over fluorescent bulbs and LEDs. Etc. Progress happens. VAWT are many decades behind HAWT in their development. And there are many more kinds of VAWT than HAWT. So there is a lot more to research, and it takes a lot more time. It’s an uphill battle because the investments and research money go toward HAWT as the more mature technology. Money follows money.

As I mentioned before, there are a great many myths about VAWT, and those myths serve to seriously retard research. Because of their deleterious effects, they are worse than just myths; they are technological prejudices that impede VAWT progress. And what bothers me most is that really cheap energy from my windmills and related devices could end up saving about 2 million lives per year that are currently lost to drinking contaminated water and breathing contaminated indoor air in developing countries. Lives are at stake. Technological prejudices kill. And most of the deaths are babies and small children. Ignorance kills. It’s a hidden holocaust. With global warming, the problems will intensify.

On sailing DDWFTTW, you are referring to “slippage” relative to the ground – perhaps because the Sharp Blimp does not have wheels on the ground. But consider that the windmill is interacting with a medium (the lower air) that is moving substantially faster than the ground to begin with. Relative to the ground, any “slippage” is forward, not backward,. So the relative motion is something like the opposite of “slippage“. But I see nothing to be gained in understanding by introducing the concepts of “slippage” or its opposite to the sketch.

If I understand you correctly, you are saying that all claims of priority about sailing DDWFTTW have been shown to be invalid by prior art. Your comment could be interpreted to mean that you discredit the accomplishments of Andrew Bauer and his Bauer Vehicle. But I assume that is not what you are referring to. If, by some chance, it is, please show me the prior art that invalidates Andrew Bauer’s first demonstration of sailing DDWFTTW (about 1969). He also made a video in 1995 of a model on a conveyor belt, at AeroVironment, the company of Paul McCready, of human-powered flight fame. Bauer was not trying to claim a record or to compete with anyone. He just wanted to show that sailing DDWFTTW was possible, and he did. I’m talking about his demonstration, not about the origin of the concept, which he said came from a student. And my guess is that the student may have invented the Bauer vehicle conceptually after learning about the Brennan torpedo that used similar relative motions for propulsion.

https://en.wikipedia.org/wiki/Brennan_torpedo

You mention the logical next step for me. The logical next step for me, if only it were that easy, is to cure my arthritis so I can get back to building and testing. I’ve been able to do very little for the last year and a half, and it’s quite discouraging.

PeterS

Hi DaveS,

You want to know why the Bird Windmill, the Flexor Windmill, and the Flipwing are different enough that they do not belong in the same group. All three devices are cross-flow devices. They do belong in the larger group of short-pull, pumping kites because they are all different ways of producing a similar effect. But the ways they do it are substantially different with respect to their physics.

n  The best type of blade for a Bird Windmill is a straight, rigid, non-fabric, streamlined profile, blade, with rocking arms perpendicular to the blade, and with the tethers attached to the other end of the rocking arms, not to the tips of the blade. The blade can still function well if it is a rigid, flat-surface blade, such as a blade made Coroplast.

Here is a video of a flat-surface, Coroplast blade  to help clarify. http://www.youtube.com/watch?v=WO4ZaTEl1Ok 

This shows a typical straight-blade with the rocking arms, each located a quarter span from the tips of the blade. The reason for deliberately not attaching the tethers to rocking arms at the tips of the blade is to double the span of the blade that can be suspended from a given tower height.

n  The Bird blade works best when it is non-fabric, although it can be fabric and still work well. So two of your criteria for similarity are not supported – your observation that all three types of blades are supported at their blade tips, and that all three blades are fabric.

Here are some major differences:

n  The Flexor and the Flipwing are drag-type devices, and they are stalled most of the time, whereas the Bird is a lift-type device that doesn’t stall. In general, lift devices are about twice as efficient as drag devices.

n  The Flexor and the Bird are rotary devices, whereas the Flipwing is an oscillatory device.

n  The Bird and the Flexor are supported by poles, whereas the Flipwing is not, but the Flexor attaches directly to a support structure and the Bird blade attaches to a tether, part or all of which is elastic shock cord.

n  The Flexor uses a fixed orbit diameter, whereas the Bird uses an extremely variable orbit diameter, and the Flipwing does not use an orbit diameter.

n  The Bird and the Flexor use centrifugal springs for pitch control, whereas the Flipwing does not. The Bird and the Flexor use different kinds of centrifugal springs.

n  The Bird uses a counterweight out in front of the blade, whereas the Flexor uses an internal weight ahead of the center of pressure, and the Flipwing has no counterweight.

n  The Flexor produces a pulling motion parallel to its axis of rotation, whereas the Bird produces a pulling motion at right angles to its axis of rotation, and also a rotary motion at the base of its axis of rotation. In contrast, the Flipwing produces a pulling motion substantially parallel with its approximate axis of oscillation, and its axis of oscillation is well forward of the blade.

I could go into more and more detail, such as discussing the various kinds of centrifugal springs and how they differ, but I think the differences I listed are sufficient to explain why the three devices don’t belong in the same sub-group. If you wanted to put the Bird and the Flexor into a subgroup of devices that use centrifugal springs for pitch control, that would make sense. But you seem to think that they are equivalent because they are similar, as if they are essentially the same device. Not so. Big differences. The Flexor is an inferior device. To treat them as equal would be to denigrate the Bird Windmill.

Therefore, please note that there is no such thing as a “Sharp-LaBreque VAWT”, just as there is no such thing as a “Sharp-Santos Flipwing”. Please note that the “Sharp VAWT is another name for the Sharp Cycloturbine, not the Bird Windmill.

You said that you want to be very clear that the AWE is about tapping much higher winds than any poles can reach, so I assume that you are referring to the Bird Windmill. Ideally, yes. Let’s get as high as possible. That is definitely the main goal. But most energy kites can’t even get off the ground by themselves without a human in the loop. The Bird blade, when using poles to support it, can’t get up very high as compared to kites in general, and that is a serious disadvantage. But a fully functioning low-kite is a lot more useful than a non-functioning high-kite. Energy kites that can’t launch themselves automatically are not fully functional . They are not competitive with windmills. As I have explained previously, a Bird blade can be suspended from a pilot kite in more than one way to produce energy, but I don’t have a way to launch such a kite automatically. So those are not yet a viable devices. Since kites can be extremely light, I think that automated helicopter drones may eventually become a cheap way to launch them.

You predicted that a Flexor kite would not be expected to succeed at dynamic soaring under water. But the Flexor never used dynamic soaring in air. So why would it use dynamic soaring in water? It is not a dynamic soaring device. The Bird Windmill doesn’t use dynamic soaring either. It uses a circular orbit that is only loosely analogous to dynamic soaring. The wind speed is the same over the whole swept area. Dynamic soaring requires two different wind speeds moving parallel with each other, that intercept two sides of the swept area. If you re-read what I said, you will see that I mentioned that the Flexor was used in water as a Flipwing. I saw a video of it working as a Flipwing in water. But my guess is that it didn’t work well enough to warrant further development.

Incidentally, some experimenters have used non-rotating cylinders that oscillate back and forth due to vortex shedding. So a variation on your Flipwing might be an inflatable cylinder. I have no idea how well it might be made to work as compared to your Flipwing, which seems to work quite well.

You mentioned that, referring to my Fluttermill experiments back around 1975, I did not have success trying to make a Flipwing. So you advised me about what I might have missed. I believe you read something that I did not write. I said that I built some small Fluttermills, meaning windmills that used blades that flutter. I used paper blades. They worked, and I invented some things that might interest you. I didn’t try to build a Flipwing because I had no way to automatically launch it. I’m interested to learn more about proven kite launching techniques.

PeterS

Hi DaveS,

Actually, it is possible to optimize a single factor of a VAWT to make it more efficient than is possible for HAWT. Simply make it extremely wide as compared to tall. That gives the wind time to speed up before reaching the downwind blades after passing through the upwind blades. A VAWT typically captures 80% of its energy during the upwind blade pass, and 20% during the downwind blade pass. If the downwind blade pass can be increased to, say, 50% of the upwind blade pass, and the upwind blade pass, due to reduced back pressure can be increased by 10%, then the total efficiency of a VAWT that would normally be 45% efficient, would be 59.4% efficiency, which is just above the Betz limit for HAWT of 59.3%. VAWT do not have the same Betz limit as HAWT. In fact, if made wider and wider, their Betz limit keeps increasing to a much higher limit than HAWT – probably close to 80%. In practice, extremely wide VAWT are not built because it does not offer any cost advantage to do so. But stacked rotors may end up being extremely wide as compared to tall, in some cases. If the HAWT-VAWT debate is truly old-hat, then you know all this.

Saying the Bauer is likely the earliest inventor of the Bauer vehicle, just not the earliest known, makes no sense. It has no meaning. Nothing in science is ever proven to be absolute, so to look for absolutes is not part of the scientific process. Maybe you mean to say that scientific findings are always tentative, pending new evidence.

The “mystery” of HAWT dominance is no mystery at all, which I explained. So now your position is that theory is only theory, and only empirical evidence will suffice. In other words, you intend to hold on to your pro-HAWT beliefs despite the theoretical evidence that contradicts it – until such time as testing demonstrates VAWT superiority. But if you had read my theoretical paper on how VAWT could replace HAWT, you would know that testing has already shown the superiority of VAWT. I refer to the wind tunnel tests at Delft University on skewing VAWT 25 degrees to the wind to obtain a 35% increase in power. So if you start with a VAWT that is 45% efficient, achieved back in the 1970’s by the original Giromill, a 35% increase yields an efficiency of 61%, which is above the Betz limit for VAWT. And if a straight-blade, fixed-blade Darrieus rotor is used, as it was in the wind tunnel tests, then the efficiency would still be 54%, which is higher than the current maximum efficiency of large-scale HAWT, which is 51%. So the matter is settled, based on empirical evidence.

You claim that AWES have the highest power-to-weight ratio of all WECS. That is true only if the amount of land around a kite-base required for safety is not considered, including all the trees, shrubs, rocks and dirt that may need to be removed or shifted. If they are considered, then AWES have the worst power-to-weight ratio of all WECS. So AWES research needs to focus on minimizing the safety circle in some way. An example would be some sort of mandatory parachute system for any heavy parts, and a collapsing or shredding system for large, soft parts in case of failure or breakaway.

Don’t get me wrong. I love energy kites and I see great promise in them. But progress requires that we be completely honest about all of the problems that remain to be solved – so that we can solve them. We cannot afford to deny evidence, whatever form it is in.

Do we agree?

PeterS

Hi JoeF,

Thanks for posting the Flexor information. I found the Hydroflexor video I remembered where the Flexor functioned as a Flipwing. Their patent helped me better understand the placement of the mass they were using. They didn’t seem to understand the pitch control that was happening. It was quite poor, and the blade seemed to rotate way too slowly. I wrote to David LeBreque, but he didn’t want any information, even though it was all in the public domain. I think that there might be a problem: Maybe when a patent holder finds prior art, they are required to add it to their patent if the patent hasn’t been issued yet, and if it has, the patent might be invalidated. If that is actually the case, then it would be an impediment to progress.

PeterS

Hi JoeF,

Interesting observation. I’m going to remember to look more closely from now on.

PeterS

Hi JoeF,

Here is a much better way to do suspend vertical axis wind turbines from a buoyant balloon.

PeterS

Hi JoeF,

For me, this document wouldn’t load.

PeterS