Messages in AirborneWindEnergy group.                          AWES 22722 to 22772 Page 347 of 440.

Group: AirborneWindEnergy Message: 22722 From: dave santos Date: 5/29/2017
Subject: Re: World looking at AWE

Group: AirborneWindEnergy Message: 22723 From: dave santos Date: 5/29/2017
Subject: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22724 From: dave santos Date: 5/29/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22725 From: dave santos Date: 5/30/2017
Subject: Zhang Lab informing multi-kite engineering science

Group: AirborneWindEnergy Message: 22726 From: Peter A. Sharp Date: 5/30/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp

Group: AirborneWindEnergy Message: 22727 From: dave santos Date: 5/30/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp

Group: AirborneWindEnergy Message: 22728 From: dougselsam Date: 5/30/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp

Group: AirborneWindEnergy Message: 22729 From: dougselsam Date: 5/30/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22730 From: Pierre BENHAIEM Date: 5/30/2017
Subject: Sharp VAWT

Group: AirborneWindEnergy Message: 22731 From: dave santos Date: 5/30/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22732 From: Peter A. Sharp Date: 5/31/2017
Subject: Sharp VAWT

Group: AirborneWindEnergy Message: 22733 From: Peter A. Sharp Date: 5/31/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22734 From: Peter A. Sharp Date: 5/31/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp

Group: AirborneWindEnergy Message: 22735 From: joe_f_90032 Date: 5/31/2017
Subject: Re: World looking at AWE

Group: AirborneWindEnergy Message: 22736 From: joe_f_90032 Date: 5/31/2017
Subject: Comparing Patent and Scientific Literature in Airborne Wind Energy

Group: AirborneWindEnergy Message: 22737 From: joe_f_90032 Date: 5/31/2017
Subject: Re: Jian Dai

Group: AirborneWindEnergy Message: 22738 From: dave santos Date: 6/1/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22739 From: dave santos Date: 6/1/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp

Group: AirborneWindEnergy Message: 22740 From: benhaiemp Date: 6/1/2017
Subject: Re: Sharp VAWT

Group: AirborneWindEnergy Message: 22742 From: joe_f_90032 Date: 6/2/2017
Subject: Re: Sharp VAWT

Group: AirborneWindEnergy Message: 22743 From: dougselsam Date: 6/2/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22744 From: Peter A. Sharp Date: 6/2/2017
Subject: Re: Sharp VAWT

Group: AirborneWindEnergy Message: 22745 From: Peter A. Sharp Date: 6/2/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22746 From: benhaiemp Date: 6/2/2017
Subject: Re: Sharp VAWT

Group: AirborneWindEnergy Message: 22747 From: joe_f_90032 Date: 6/2/2017
Subject: Kitewinder's news on ground generator

Group: AirborneWindEnergy Message: 22748 From: joe_f_90032 Date: 6/2/2017
Subject: Kitewinder will be at the O'zenergie event

Group: AirborneWindEnergy Message: 22749 From: dave santos Date: 6/2/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22750 From: dave santos Date: 6/2/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22751 From: olivierabristol Date: 6/3/2017
Subject: Re: Kitewinder's KiweeOne product nears release

Group: AirborneWindEnergy Message: 22752 From: joe_f_90032 Date: 6/3/2017
Subject: Re: Kitewinder's KiweeOne product nears release

Group: AirborneWindEnergy Message: 22753 From: olivierabristol Date: 6/3/2017
Subject: Re: Kitewinder's KiweeOne product nears release

Group: AirborneWindEnergy Message: 22754 From: Peter A. Sharp Date: 6/3/2017
Subject: Re: Sharp VAWT

Group: AirborneWindEnergy Message: 22755 From: dave santos Date: 6/5/2017
Subject: Re: Kitewinder's KiweeOne product nears release

Group: AirborneWindEnergy Message: 22756 From: Uwe Fechner Date: 6/5/2017
Subject: Summer job for C/C++ programmer on flight control

Group: AirborneWindEnergy Message: 22757 From: dougselsam Date: 6/5/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22758 From: dave santos Date: 6/6/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22759 From: dave santos Date: 6/6/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22760 From: Pierre BENHAIEM Date: 6/6/2017
Subject: Re: Sharp VAWT

Group: AirborneWindEnergy Message: 22761 From: Pierre BENHAIEM Date: 6/6/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22762 From: Peter A. Sharp Date: 6/6/2017
Subject: Re: Sharp VAWT

Group: AirborneWindEnergy Message: 22763 From: joe_f_90032 Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22764 From: dave santos Date: 6/7/2017
Subject: Pilot-Kite-lofted-Power-Kite and Varidrogue Tests (TX AWE Encampment

Group: AirborneWindEnergy Message: 22765 From: dave santos Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22766 From: dave santos Date: 6/7/2017
Subject: Re: Sharp VAWT

Group: AirborneWindEnergy Message: 22767 From: dave santos Date: 6/7/2017
Subject: Point-mass quasi-particle assumption in AWE physics simulations

Group: AirborneWindEnergy Message: 22768 From: Pierre BENHAIEM Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22769 From: joe_f_90032 Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22770 From: joe_f_90032 Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22771 From: dave santos Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

Group: AirborneWindEnergy Message: 22772 From: benhaiemp Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory




Group: AirborneWindEnergy Message: 22722 From: dave santos Date: 5/29/2017
Subject: Re: World looking at AWE
Good to see SkySails back after a brief insolvency, keeping the ship-kite in public play as Makani and Ampyx struggle to scale up.

The solar-kite yacht amounts to about 100-200kW of regen capability. We are seeing the large AWE ventures now breeze past KiteNRG's ~100kW record, so continued AWE progress tracked by peak power remains on track for MW scale electrical-utility units by about 2030.

Even as ship kites seem favored by engineering scaling laws and logged flight safety and reliability, actual kite farm design is wide open, particularly the mechanical interface of multiple giant kites to drive ~GW class generators at greatest economy-of-scale. This is the realm where small developers working with scale-prototype kitefarm experiments can accomplish great things in the next few years, as the unit-kite technology and LCOE contest plays out between the large ventures.

SkySails short pdf on its yacht kite system-


Race for Water yacht specs-


On ‎Monday‎, ‎May‎ ‎29‎, ‎2017‎ ‎01‎:‎28‎:‎12‎ ‎PM‎ ‎CDT, joefaust333@gmail.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

World looking at AWE

======================================


A 100-Ton Kitesurfer
This Kite system is an essential part of the Race for Water energy mix: Solar and Wind to complementarily generate energy, Batteries and Hydrogen to ...


Group: AirborneWindEnergy Message: 22723 From: dave santos Date: 5/29/2017
Subject: Kite String and Effective String Theory
As long conjectured on the AWES Forum, kite string and string theory should ultimately match up, after all, string is string. Mapping exact connections was a slow but pleasant process of learning a lot more about both kites and physics. Reality is not dull to the diligent student.

Kite string in the sky turns out to be special phase of condensed matter just as exotic as any lab experiment. "Effective" string theory turns out to be the keyword for seeking "physical" strings in any context, including kites. Similarly, "analogue" QM is the keyword for seeing real kite flight in a highly advanced theoretic framework.

Its only natural that advancing kite expertise seeks out all applicable physics; that such physics is rich and profound and inspires and drives fertile directions in AWES engineering science, like kite networks as a metamaterial technology. 

--------------

Effective string theory for vortex lines in fluids and superfluids

Bart Horn, Alberto Nicolis, Riccardo Penco,

Abstract

We discuss the effective string theory of vortex lines in ordinary fluids and low-temperature superfluids, by describing the bulk fluid flow in terms of a two-form field to which vortex lines can couple. We derive the most general low-energy effective Lagrangian that is compatible with (spontaneously broken) Poincaré invariance and worldsheet reparameterization invariance. This generalizes the effective action developed in [1, 2]. By applying standard field-theoretical techniques, we show that certain low-energy coupling constants — most notably the string tension — exhibit RG running already at the classical level. We discuss applications of our techniques to the study of Kelvin waves, vortex rings, and the coupling to bulk sound modes.


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Group: AirborneWindEnergy Message: 22724 From: dave santos Date: 5/29/2017
Subject: Re: Kite String and Effective String Theory
A bit of review for anyone new to advancing kite physics-


    - Assume high Debye temperature of UHMWPE to recover low temp QM dynamics.

    - Assign Planck's Constant's quantum-of-action to kite characteristic length (as the proper Planck Unit, and like Reynold's Number's (Re) L).

    - Consider twisted and braided line as vortical matter.

    - Recall the 2007 starting paradox, how a ship towing hawser (or kite tether) can transmit ~10MW at 100% efficiency over a large distance, yet remain cool to the touch (!).

    - [Van Veen, 97] was a start in identifying kite flight as chaos physics. Newton himself was a teenage kite experimenter. Our kite physics remains classical, via Bohmian mechanics (de Broglie pilot-wave QM).

On ‎Monday‎, ‎May‎ ‎29‎, ‎2017‎ ‎09‎:‎38‎:‎16‎ ‎PM‎ ‎CDT, dave santos santos137@yahoo.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

As long conjectured on the AWES Forum, kite string and string theory should ultimately match up, after all, string is string. Mapping exact connections was a slow but pleasant process of learning a lot more about both kites and physics. Reality is not dull to the diligent student.

Kite string in the sky turns out to be special phase of condensed matter just as exotic as any lab experiment. "Effective" string theory turns out to be the keyword for seeking "physical" strings in any context, including kites. Similarly, "analogue" QM is the keyword for seeing real kite flight in a highly advanced theoretic framework.

Its only natural that advancing kite expertise seeks out all applicable physics; that such physics is rich and profound and inspires and drives fertile directions in AWES engineering science, like kite networks as a metamaterial technology. 

--------------

Effective string theory for vortex lines in fluids and superfluids

Bart Horn, Alberto Nicolis, Riccardo Penco,

Abstract

We discuss the effective string theory of vortex lines in ordinary fluids and low-temperature superfluids, by describing the bulk fluid flow in terms of a two-form field to which vortex lines can couple. We derive the most general low-energy effective Lagrangian that is compatible with (spontaneously broken) Poincaré invariance and worldsheet reparameterization invariance. This generalizes the effective action developed in [1, 2]. By applying standard field-theoretical techniques, we show that certain low-energy coupling constants — most notably the string tension — exhibit RG running already at the classical level. We discuss applications of our techniques to the study of Kelvin waves, vortex rings, and the coupling to bulk sound modes.


-------------




Group: AirborneWindEnergy Message: 22725 From: dave santos Date: 5/30/2017
Subject: Zhang Lab informing multi-kite engineering science
In 2011, I visited Zhang Lab at NYU, and enjoyed discussions of AWE kites from the perspective of mathematical physics of biological and collective flight. Its been a pleasure since then to see an ongoing concordance of ideas presented on the AWES Forum and the research directions of the Lab. There is no doubt that Zhang's circle is increasingly able to formally define specific kite flight dynamics promising to AWE.

A recent major paper is a good example of the growing sophistication of the Lab's flight science, making the same sort insights as kPower advocates about "lattice-like or crystalline" orders of flying units with "spring-like fluid forces (that) may lead to collective vibrational modes, akin to phonons in conventional crystals". Expect further research along these lines to vitally inform and inspire AWES networked kite design.
-------
sample quote-

"...high-Reynolds-number animal collectives, from insect and krill swarms (Re∼102–104) to bird flocks and fish schools (Re∼103–106). The high densities in these groups suggest that flow effects are considerable [4–7,42]. Direct extrapolation of our results implies that such ensembles would assume lattice-like or crystalline arrangements, though it remains for future studies to investigate many-body arrays of free locomotors in 1D, 2D, and 3D configurations. Recent work on wings held at fixed spacing indicates the dominance of nearest-neighbor interactions [23], suggesting that two-body results may extend to the many-body problem.  In this case, the spring-like fluid forces may lead to collective vibrational modes, akin to phonons in conventional crystals."

--------

PHYSICAL REVIEW FLUIDS 1, 071201(R) (2016)

Flow interactions lead to orderly formations of flapping wings in forward flight

Sophie Ramananarivo,1 Fang Fang,1,* Anand Oza,1,* Jun Zhang,1,2 and Leif Ristroph1 1Applied Math Laboratory, Courant Institute, New York University, New York, New York, USA 2Department of Physics, New York University, New York, USA and New York University Shanghai, Shanghai, China


---------

Note that fluid-dynamics mostly applies in both forward and reverse time directions (commutative property), and that harvesting and locomotion are thus much like generation and motoring phases in AWES operation. This short paper covers some basics, as also covered in various posts on the AWES Forum-





Group: AirborneWindEnergy Message: 22726 From: Peter A. Sharp Date: 5/30/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp

Response to DougS,

Thank you for your comments. I will attempt to respond to them as best I can. Sometimes simple assertions can contain ambiguities and misconceptions that are tedious to sort out. Careful analysis and adequate explanations of technical issues can be time consuming, so I apologize for the length of some of my responses.

          "...you often talk about a tilted VAWT with short blades compared to diameter being able to intercept more area than if it were flat, as though it is unique and as though it has no downsides."

I don't know if it is unique, and I have never assumed or said that tilting VAWT have no downsides. I tilted my VAWT as a form of overspeed control way back in 1978. I only proposed tilting to increase the power after the Delft wind tunnel test showed that an ordinary H-VAWT could increase its power 35% by tipping 25 degrees into the wind. If you know of someone who proposed tilting a VAWT to increase the power before Delft, please tell me. As for the downsides of that technique, there are downsides to most techniques. As you know, engineering usually requires a great many compromises. I assume that my readers are sophisticated enough to know that.

 

          "Increasing swept area by tilting it may be true, but this configuration would still be judged and rated on its intercepted area when tilted."

At first glance, your assertion seems like a simple and sensible solution to the problem of measuring the swept area of tilted VAWT. But it isn’t workable.

For example, I use tipping (or swinging away) as an overspeed control technique. The VAWT starts in a vertical position. As the wind speed increases, the tilt angle increases. At first the power increases due to tipping and then it decreases, which provides overspeed control. The tilt angle varies with the wind speed. The tilt angle also varies with the tip speed ratio because a lower TSR means a lower rotor drag, and rotor drag is what determines the angle of tipping (or swinging away from the wind). So what is the swept area?

          Here is another complication: Placing a VAWT upright on top of the edge of a building or at the top of hill can produce the same effect as tilting, without tilting the VAWT at all, because the airflow is tilted, not the VAWT. So what then is the swept area of the VAWT? Does it change as the angle of the wind changes? If so, then there is no standard way to measure the swept area.

If you wish to insist that the intercepted area must be that which the wind “sees”, then all wind turbines should be measured the same way in order to maintain consistency. But since the direction of the wind is always shifting from side to side and up and down, the swept area of any wind turbine, as seen from the perspective of the wind, is constantly changing. So your technique leads to the conclusion that all wind turbines have a variable swept area. In fact, they all do, except perhaps in a wind tunnel. But then the calculation of the Cp curve must take that constantly changing swept area into account. But how, given that the angle of the wind is variable and unpredictable? The measuring of the swept area becomes almost impossibly complex.

From a scientific perspective, it makes sense to simplify the definition of the swept area -- to ignore the fluctuations in the angle of the wind and to assume that the swept area is the same as usual, with the wind flow at a right angle to the rotor. Similarly, it makes sense to ignore the tilt angle of the rotor, which in some cases is constantly changing, and to simply use the original swept area for the calculations of the Cp curve. The purpose of the Cp curve and the power curve is to allow different wind turbines to be compared.

          From a scientific perspective, the matter is simple to resolve: Use the original swept area as conventionally measured, and designate the performance curve as the “equivalent coefficient of performance (Cpe)” to make clear that the VAWT used tipping. It would also be informative to mark the power curve by designating each 5 degrees of tipping.

If you are still not convinced, then consider the effect of using your technique when measuring the performance of a SuperTurbine®. Since your rotors are pre-tilted, their swept area would be only what the wind “sees” from its perspective. That would give the multiple rotors about a 20% smaller swept area than when measured conventionally from a position directly in front of the rotors, and it would inflate the calculated Cp accordingly. That would make a SuperTurbine® seem much more efficient than it actually is. That would make for a great sales pitch. But do you still favor your method of measuring the swept area?

When a HAWT rotor is tilted to the wind, the swept area and power go down. When a VAWT with an initially rectangular swept area is tilted to the wind, the swept area and power go up at first and eventually go down as tipping angle increases further. That’s just basic solid-geometry and basic physics. It is an inherent advantage of VAWT over HAWT. It is not some phony partisan attempt to inflate the value of VAWT. It’s just a fact.


“The factors you do not mention:

Twice the tip-losses because each "short" blade has two ends (two sources of tip-losses), and that becomes more important because of the short blades, and”

          First, some preliminary comments:

As you know, the inner end of HAWT blades produce very little lift and thrust because they typically have a solidity ratio that is far too low for their very low TSR. So the inner end of HAWT blades are close to useless. However, despite that disadvantage, the outer blade tips can move fast enough, and sweep a much larger area, so that compensates -- because lift is proportional to the square of the air speed.

          VAWT blades are analogous to airplane wings (especially glider wings), which have two blade tips. Both large airplanes and small airplanes can use wings with a high aspect ratio. Tip losses are minimized by using a high aspect ratio wing (blade), plus tip vanes or tapered tips. The whole wing (blade) moves at the same speed. Airplanes move upwind, downwind, and cross-wind, as do VAWT blades.

The average air speed of the blades of H-rotor VAWT and 3-bladed HAWT are about the same (3 to 3.5). But HAWT blades are more efficient due to the higher TSR of the blade tips. But some VAWT blades (that pitch) are potentially more powerful because they sweep the swept area twice each revolution, and because the rotor can be tipped, plus additional advantages.

Now to your comment: You seem to be saying that the way you would design a very wide VAWT is to use the same three blades of a tall VAWT, but greatly reduce only their span, and not their chord. The result would be blades with an aspect ratio of something like 2 or less. So the blades would suffer enormously from tip losses. If that is what you are saying, then you would be correct. But what is not clear is why you are saying that. No aerodynamicist would design a VAWT like that. Consequently, your supposedly omitted “factor” is a non-problem. So why would you expect me to mention a non-problem as if it were a real problem?

If a VAWT is made very wide, instead of tall, it will require many small blades in order to maintain a reasonable blade-aspect-ratio and an adequate solidity ratio. Those blades will have both a shorter span and a shorter chord. But the blade-aspect-ratio could still be 10 or more to minimize tip losses. Tip vanes (or shaping the tips) could also be used to further reduce tip losses, as is often done for airplanes and VAWT. So tip losses need not be an issue for a very wide VAWT.

Please note carefully: The biggest problem for a very wide VAWT is not tip losses. It is that the many-more smaller-blades would have a substantially lower Reynolds number. They would not be as efficient as much larger blades of a tall VAWT.

However, because the VAWT is very wide, a relatively small amount of tipping can expose a large percentage of the downwind blade pass to clean air, while also reducing the back pressure on the upwind blade pass. So the gains could be much larger than the losses. The gains should still equal, or exceed, the 35% increase in power achieved by a Delft wind tunnel model with a more squared swept area.

Since you apparently assume that it is not possible to design a practical, wide VAWT, here is a brief description of one of many ways to design one that tilts to increase its swept area:

Use a very large-diameter, narrow, horizontal ring. Place a vertical shaft at the center of the ring. Use 3 spokes (cords or wires) from the ring to the top of the shaft, and 3 spokes to the bottom of the shaft. That creates the rough equivalent of a bicycle wheel shape with a wide hub section. Suspend the top of the shaft from an overhead cable using a long enough cord and a swivel bearing. Many such VAWT could be suspended from the same overhead cable strung between two guyed towers.

Mount many Sharp Cycloturbine blade-units around the circumference of the ring to achieve a solidity ratio of 0.2. Use a blade aspect ratio between 6 and 10, and add tip plates. Mount 3 RATs on the ring and space them 120 degrees apart.

Add a weight to the bottom of the shaft to control the rate at which the suspended VAWT swings away from the wind. Add an electrical cord and slip rings at the bottom of the shaft, and extend the electrical cords to the ground. Leave a lot of slack to allow the VAWT to swing in any direction. If the wind becomes too strong, the VAWT swings farther away from the wind and disrupts the pitch control to limit the power and the rpm. Additional refinements can be added if necessary. This VAWT has some downsides, but it would be cheap and efficient.

Each RAT would move at 3 to 4 times the wind speed. So it would produce the equivalent of roughly 27 to 64 stationary rotors of the same size. The RAT generators would spin 3 to 4 times as fast as stationary generators, so they could be much smaller and cheaper. A more sophisticated version of this VAWT, if necessary, would use two concentric rings rotating in opposite directions to cancel any gyroscopic effects. Other refinements are possible.

The main problems with this very wide VAWT are RAT rotor noise and bearing wear. Both can be solved reasonably well. Rotor noise can be reduced using higher solidity RAT rotors with a ring around the blade tips. Bearing wear can be reduced by using magnetic bearings or concentric bearings (one inside of the other to reduce the rpm of each).

 

“2)  You could remove the blades of any such vertical-axis turbine and throw them in the dumpster, then apply airfoils to the arms that held the blades, turn the whole thing 90 degrees, and make more power than the original vertical-axis machine.  V-A machines have quite a history: They seldom, if ever, work out, for many very good reasons, most of which I'm pretty sure you are aware of, but maybe tend to overlook when promoting V-A machines..”

          You might be surprised to know that I consider most VAWT to be inherently flawed or handicapped when compared to the Sharp Cycloturbine. Please note carefully: The main problems with most VAWT are that they allow blade stall and they produce a narrow and sharply peaked Cp curve. So they are not nearly as good as they could be at capturing the large amount of energy in wind gusts. When a gust hits, they lose a lot of that energy. But according to my informal observations and the hundreds of research papers I have read, the Sharp Cycloturbine should be able to capture most of the additional energy in wind gusts because the blades don’t stall, they react quickly to changes in the velocity of their apparent wind, and the torque curve is very wide. So when I refer to VAWT, I usually have the Sharp Cycloturbine in mind unless I indicate otherwise.

          Way back in the 1970’s, as you may recall, Terry Meekram sold medium-scale HAWT that had blades with no twist and no taper. They worked fine. They could not have been as efficient as HAWT with more refined blades, but his blades were relatively cheap to build, as I recall. And currently, the excellent Bergey small-scale HAWT uses blades with no twist or taper. So you are correct that just the blade support arms of an H-VAWT could be converted into useful HAWT blades. And that nicely illustrates that VAWT usually require more material, and weigh more, than HAWT. That is a disadvantage for most VAWT. (Although, the Bird Windmill has no support arms or shaft, and the Lux eggbeater Darrieus rotor has no support arms, no shaft, and no tower.) But it is not a decisive disadvantage because some VAWT may be cheaper to make than conventional HAWT. When comparing VAWT and HAWT, there are dozens of different designs and variables to consider. And there is still a lot of testing to be done of existing designs. One of my focuses is bringing new VAWT advantages to people’s attention. The bottom line is the average cost of the energy over the lifetime of the wind turbine.

          You claim that a HAWT made with just the support arms of a VAWT could produce more power than the original VAWT. That would depend on the aspect ratio of the VAWT because a tall VAWT would have relatively short support arms that would make for only two small HAWT rotors relative to the much larger swept area of the VAWT. So your assertion, as you stated it, is both right and wrong, depending upon the aspect ratio of the VAWT. Plus, some VAWT (as above) do not require support arms at all, so that comparison would obviously favor VAWT.

It’s true that most VAWT have not worked out. The same is true for most HAWT, especially small-scale HAWT. There are now a lot of new VAWT and HAWT being sold, and it is not yet clear which ones, if any, will endure. You know far better than I how difficult it is to develop a reliable wind turbine, and nothing is more important than reliability.

--------

          As for your SuperTurbine®, as you know, I’m a fan. I love it. It inspires me. I kick myself for not having invented it. I use it as a standard for comparison when inventing wind turbines.

PeterS

 

 

 

 

 

 

 

Group: AirborneWindEnergy Message: 22727 From: dave santos Date: 5/30/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp
What Peter and Doug really need are more small AWES demonstrators, actually flying, to show that scaling law predictions of poor power-to-weight are somehow mistaken. The picture looks so bleak to me, I don't see the ST approach even reaching 200ft harvest height by a partisan DIY effort. Then where is a typical Sharp Turbine to judge? Or why the dull confusion of whether an ST is being discussed in tower or flight mode? Is it OK for most folks to see HAWT predominance as technological reality. Is not everything else, excepting farm irrigation turbines, "fantasy turbines", as Gipe says?

OK, Peter and Doug are not NASA, nor GoogleX, nor Stanford, nor MIT, and there are two third-party torque-driven semi-vertical experiments (Rod and Christof), but its time for this design space face its scaling challenge, without excuses, like blaming a lack of comprehension on the part of all the other teams busy advancing other architectures.

Let the quasi-VAWT AWES prepare to test against all others, if it is not too marginal to even make the race. Lets see more bigger better VAWT AWES demos, to justify the extraordinary claims. All the other architectures (soft-kite, tethered-glider, flygen-kiteplane, etc) are on track to be flying high in the looming great AWE race, after hundreds of incremental developmental prototypes.

On ‎Tuesday‎, ‎May‎ ‎30‎, ‎2017‎ ‎11‎:‎58‎:‎11‎ ‎AM‎ ‎CDT, 'Peter A. Sharp' sharpencil@sbcglobal.net [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

Response to DougS,

Thank you for your comments. I will attempt to respond to them as best I can. Sometimes simple assertions can contain ambiguities and misconceptions that are tedious to sort out. Careful analysis and adequate explanations of technical issues can be time consuming, so I apologize for the length of some of my responses.

          "...you often talk about a tilted VAWT with short blades compared to diameter being able to intercept more area than if it were flat, as though it is unique and as though it has no downsides."

I don't know if it is unique, and I have never assumed or said that tilting VAWT have no downsides. I tilted my VAWT as a form of overspeed control way back in 1978. I only proposed tilting to increase the power after the Delft wind tunnel test showed that an ordinary H-VAWT could increase its power 35% by tipping 25 degrees into the wind. If you know of someone who proposed tilting a VAWT to increase the power before Delft, please tell me. As for the downsides of that technique, there are downsides to most techniques. As you know, engineering usually requires a great many compromises. I assume that my readers are sophisticated enough to know that.

 

          "Increasing swept area by tilting it may be true, but this configuration would still be judged and rated on its intercepted area when tilted."

At first glance, your assertion seems like a simple and sensible solution to the problem of measuring the swept area of tilted VAWT. But it isn’t workable.

For example, I use tipping (or swinging away) as an overspeed control technique. The VAWT starts in a vertical position. As the wind speed increases, the tilt angle increases. At first the power increases due to tipping and then it decreases, which provides overspeed control. The tilt angle varies with the wind speed. The tilt angle also varies with the tip speed ratio because a lower TSR means a lower rotor drag, and rotor drag is what determines the angle of tipping (or swinging away from the wind). So what is the swept area?

          Here is another complication: Placing a VAWT upright on top of the edge of a building or at the top of hill can produce the same effect as tilting, without tilting the VAWT at all, because the airflow is tilted, not the VAWT. So what then is the swept area of the VAWT? Does it change as the angle of the wind changes? If so, then there is no standard way to measure the swept area.

If you wish to insist that the intercepted area must be that which the wind “sees”, then all wind turbines should be measured the same way in order to maintain consistency. But since the direction of the wind is always shifting from side to side and up and down, the swept area of any wind turbine, as seen from the perspective of the wind, is constantly changing. So your technique leads to the conclusion that all wind turbines have a variable swept area. In fact, they all do, except perhaps in a wind tunnel. But then the calculation of the Cp curve must take that constantly changing swept area into account. But how, given that the angle of the wind is variable and unpredictable? The measuring of the swept area becomes almost impossibly complex.

From a scientific perspective, it makes sense to simplify the definition of the swept area -- to ignore the fluctuations in the angle of the wind and to assume that the swept area is the same as usual, with the wind flow at a right angle to the rotor. Similarly, it makes sense to ignore the tilt angle of the rotor, which in some cases is constantly changing, and to simply use the original swept area for the calculations of the Cp curve. The purpose of the Cp curve and the power curve is to allow different wind turbines to be compared.

          From a scientific perspective, the matter is simple to resolve: Use the original swept area as conventionally measured, and designate the performance curve as the “equivalent coefficient of performance (Cpe)” to make clear that the VAWT used tipping. It would also be informative to mark the power curve by designating each 5 degrees of tipping.

If you are still not convinced, then consider the effect of using your technique when measuring the performance of a SuperTurbine®. Since your rotors are pre-tilted, their swept area would be only what the wind “sees” from its perspective. That would give the multiple rotors about a 20% smaller swept area than when measured conventionally from a position directly in front of the rotors, and it would inflate the calculated Cp accordingly. That would make a SuperTurbine® seem much more efficient than it actually is. That would make for a great sales pitch. But do you still favor your method of measuring the swept area?

When a HAWT rotor is tilted to the wind, the swept area and power go down. When a VAWT with an initially rectangular swept area is tilted to the wind, the swept area and power go up at first and eventually go down as tipping angle increases further. That’s just basic solid-geometry and basic physics. It is an inherent advantage of VAWT over HAWT. It is not some phony partisan attempt to inflate the value of VAWT. It’s just a fact.


“The factors you do not mention:

Twice the tip-losses because each "short" blade has two ends (two sources of tip-losses), and that becomes more important because of the short blades, and”

          First, some preliminary comments:

As you know, the inner end of HAWT blades produce very little lift and thrust because they typically have a solidity ratio that is far too low for their very low TSR. So the inner end of HAWT blades are close to useless. However, despite that disadvantage, the outer blade tips can move fast enough, and sweep a much larger area, so that compensates -- because lift is proportional to the square of the air speed.

          VAWT blades are analogous to airplane wings (especially glider wings), which have two blade tips. Both large airplanes and small airplanes can use wings with a high aspect ratio. Tip losses are minimized by using a high aspect ratio wing (blade), plus tip vanes or tapered tips. The whole wing (blade) moves at the same speed. Airplanes move upwind, downwind, and cross-wind, as do VAWT blades.

The average air speed of the blades of H-rotor VAWT and 3-bladed HAWT are about the same (3 to 3.5). But HAWT blades are more efficient due to the higher TSR of the blade tips. But some VAWT blades (that pitch) are potentially more powerful because they sweep the swept area twice each revolution, and because the rotor can be tipped, plus additional advantages.

Now to your comment: You seem to be saying that the way you would design a very wide VAWT is to use the same three blades of a tall VAWT, but greatly reduce only their span, and not their chord. The result would be blades with an aspect ratio of something like 2 or less. So the blades would suffer enormously from tip losses. If that is what you are saying, then you would be correct. But what is not clear is why you are saying that. No aerodynamicist would design a VAWT like that. Consequently, your supposedly omitted “factor” is a non-problem. So why would you expect me to mention a non-problem as if it were a real problem?

If a VAWT is made very wide, instead of tall, it will require many small blades in order to maintain a reasonable blade-aspect-ratio and an adequate solidity ratio. Those blades will have both a shorter span and a shorter chord. But the blade-aspect-ratio could still be 10 or more to minimize tip losses. Tip vanes (or shaping the tips) could also be used to further reduce tip losses, as is often done for airplanes and VAWT. So tip losses need not be an issue for a very wide VAWT.

Please note carefully: The biggest problem for a very wide VAWT is not tip losses. It is that the many-more smaller-blades would have a substantially lower Reynolds number. They would not be as efficient as much larger blades of a tall VAWT.

However, because the VAWT is very wide, a relatively small amount of tipping can expose a large percentage of the downwind blade pass to clean air, while also reducing the back pressure on the upwind blade pass. So the gains could be much larger than the losses. The gains should still equal, or exceed, the 35% increase in power achieved by a Delft wind tunnel model with a more squared swept area.

Since you apparently assume that it is not possible to design a practical, wide VAWT, here is a brief description of one of many ways to design one that tilts to increase its swept area:

Use a very large-diameter, narrow, horizontal ring. Place a vertical shaft at the center of the ring. Use 3 spokes (cords or wires) from the ring to the top of the shaft, and 3 spokes to the bottom of the shaft. That creates the rough equivalent of a bicycle wheel shape with a wide hub section. Suspend the top of the shaft from an overhead cable using a long enough cord and a swivel bearing. Many such VAWT could be suspended from the same overhead cable strung between two guyed towers.

Mount many Sharp Cycloturbine blade-units around the circumference of the ring to achieve a solidity ratio of 0.2. Use a blade aspect ratio between 6 and 10, and add tip plates. Mount 3 RATs on the ring and space them 120 degrees apart.

Add a weight to the bottom of the shaft to control the rate at which the suspended VAWT swings away from the wind. Add an electrical cord and slip rings at the bottom of the shaft, and extend the electrical cords to the ground. Leave a lot of slack to allow the VAWT to swing in any direction. If the wind becomes too strong, the VAWT swings farther away from the wind and disrupts the pitch control to limit the power and the rpm. Additional refinements can be added if necessary. This VAWT has some downsides, but it would be cheap and efficient.

Each RAT would move at 3 to 4 times the wind speed. So it would produce the equivalent of roughly 27 to 64 stationary rotors of the same size. The RAT generators would spin 3 to 4 times as fast as stationary generators, so they could be much smaller and cheaper. A more sophisticated version of this VAWT, if necessary, would use two concentric rings rotating in opposite directions to cancel any gyroscopic effects. Other refinements are possible.

The main problems with this very wide VAWT are RAT rotor noise and bearing wear. Both can be solved reasonably well. Rotor noise can be reduced using higher solidity RAT rotors with a ring around the blade tips. Bearing wear can be reduced by using magnetic bearings or concentric bearings (one inside of the other to reduce the rpm of each).

 

“2)  You could remove the blades of any such vertical-axis turbine and throw them in the dumpster, then apply airfoils to the arms that held the blades, turn the whole thing 90 degrees, and make more power than the original vertical-axis machine.  V-A machines have quite a history: They seldom, if ever, work out, for many very good reasons, most of which I'm pretty sure you are aware of, but maybe tend to overlook when promoting V-A machines..”

          You might be surprised to know that I consider most VAWT to be inherently flawed or handicapped when compared to the Sharp Cycloturbine. Please note carefully: The main problems with most VAWT are that they allow blade stall and they produce a narrow and sharply peaked Cp curve. So they are not nearly as good as they could be at capturing the large amount of energy in wind gusts. When a gust hits, they lose a lot of that energy. But according to my informal observations and the hundreds of research papers I have read, the Sharp Cycloturbine should be able to capture most of the additional energy in wind gusts because the blades don’t stall, they react quickly to changes in the velocity of their apparent wind, and the torque curve is very wide. So when I refer to VAWT, I usually have the Sharp Cycloturbine in mind unless I indicate otherwise.

          Way back in the 1970’s, as you may recall, Terry Meekram sold medium-scale HAWT that had blades with no twist and no taper. They worked fine. They could not have been as efficient as HAWT with more refined blades, but his blades were relatively cheap to build, as I recall. And currently, the excellent Bergey small-scale HAWT uses blades with no twist or taper. So you are correct that just the blade support arms of an H-VAWT could be converted into useful HAWT blades. And that nicely illustrates that VAWT usually require more material, and weigh more, than HAWT. That is a disadvantage for most VAWT. (Although, the Bird Windmill has no support arms or shaft, and the Lux eggbeater Darrieus rotor has no support arms, no shaft, and no tower.) But it is not a decisive disadvantage because some VAWT may be cheaper to make than conventional HAWT. When comparing VAWT and HAWT, there are dozens of different designs and variables to consider. And there is still a lot of testing to be done of existing designs. One of my focuses is bringing new VAWT advantages to people’s attention. The bottom line is the average cost of the energy over the lifetime of the wind turbine.

          You claim that a HAWT made with just the support arms of a VAWT could produce more power than the original VAWT. That would depend on the aspect ratio of the VAWT because a tall VAWT would have relatively short support arms that would make for only two small HAWT rotors relative to the much larger swept area of the VAWT. So your assertion, as you stated it, is both right and wrong, depending upon the aspect ratio of the VAWT. Plus, some VAWT (as above) do not require support arms at all, so that comparison would obviously favor VAWT.

It’s true that most VAWT have not worked out. The same is true for most HAWT, especially small-scale HAWT. There are now a lot of new VAWT and HAWT being sold, and it is not yet clear which ones, if any, will endure. You know far better than I how difficult it is to develop a reliable wind turbine, and nothing is more important than reliability.

--------

          As for your SuperTurbine®, as you know, I’m a fan. I love it. It inspires me. I kick myself for not having invented it. I use it as a standard for comparison when inventing wind turbines.

PeterS

 

 

 

 

 

 

 

Group: AirborneWindEnergy Message: 22728 From: dougselsam Date: 5/30/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp

PeterS noted: "If a VAWT is made very wide, instead of tall, it will require many small blades in order to maintain a reasonable blade-aspect-ratio and an adequate solidity ratio. Those blades will have both a shorter span and a shorter chord. But the blade-aspect-ratio could still be 10 or more to minimize tip losses. Tip vanes (or shaping the tips) could also be used to further reduce tip losses, as is often done for airplanes and VAWT. So tip losses need not be an issue for a very wide VAWT.

Please note carefully: The biggest problem for a very wide VAWT is not tip losses. It is that the many-more smaller-blades would have a substantially lower Reynolds number. They would not be as efficient as much larger blades of a tall VAWT"

DougS remarks:

***Hi Peter, and thanks for the kind words regarding SuperTurbine(R).  I almost did not post that last message to you because I can tell you already know everything I wrote.  Not much I can add to what you wrote above.   I think it was just for the benefit of "the rest of the class".  I DO think it IS a very interesting observation that you pointed out: the fact that you CAN increase the swept area of a V-A machine by tilting it.  But that interesting fact may not be enough to "rescue" the V-A concept.  Machines that naturally want to tear themselves apart start with quite a disadvantage, from that standpoint.  Some of this stuff starts as "all you gotta do is...", but the "all you gotta do" starts to add up to a much more complicated and less reliable configuration than the simple propeller, so it is not really "all you gotta do" so much as "additional steps and material required to achieve lower performance than the status quo".  Someone is always trying to "rescue" the V-A concept with more "all you gotta do's" but so far, nobody has had much luck.  But let's never stop thinking, and let's never stop trying to come up with an improved wind energy device!

I, like most other wind inventors, of course also have many pet vertical-axis designs that run through my mind, so I am not coming from the camp of saying V-A machines will never be useful.  And also it's good to keep in mind that tilted axes have advantages.  The Bergey 10-kW machine here is tilted something like 10 degrees, with little downside.  The blades work fine with a constant pitch and chord, mostly because of a choice of a high-lift airfoil that still works at a steep pitch out near the tips because the resulting lower AoA at the tip, which offers less lift, is offset by the way larger chord than necessary.  But it makes the blades twice as heavy as they need to be, which is bad for bearing longevity, and that low AoA can be very noisy in strong winds.  (Is that a freight-train or a Huey helicopter?)  Just a month or so ago, during a big storm where we can stand in the garage protected, but hear all the turbines very well, my girlfriend said "your turbines are better than the Bergey because yours are quiet".  I told her thanks, but also that being quieter does not make a 1.5 kW turbine "better" than a 10-kW turbine (that can hit 14 kW).  Still, one of my millions of projects that I will probably never get to, is putting better blades on the Bergey.

Group: AirborneWindEnergy Message: 22729 From: dougselsam Date: 5/30/2017
Subject: Re: Kite String and Effective String Theory
DaveS noted: " - Recall the 2007 starting paradox, how a ship towing hawser (or kite tether) can transmit ~10MW at 100% efficiency over a large distance, yet remain cool to the touch (!)."

DougS remarks: *** I do not know of anyone else who would call it a paradox that a rope towing something does not heat up, due to energy of force x distance.   ("Perpetual motion"?)

Stationary reference frame: The energy put in at one end of the rope is extracted from the other end, so, no net energy remaining in the rope, no heating expected.

Moving reference frame:  force applied, no relative distance moved, so force x distance = 0, no net energy used.

Placing a rope under tension is not a constant source of heat for the rope, no matter the chosen frame of reference.  This has never been seen as a paradox, as far as I know.  Seems like a case of thinking too hard, but not thoroughly.

Group: AirborneWindEnergy Message: 22730 From: Pierre BENHAIEM Date: 5/30/2017
Subject: Sharp VAWT

Hi Peter,

 There are a lot of points in your wide last message. The following concern can be interesting and, in my opinion looks to be the main point: please can you detail it, providing potential research papers to do? 

Thanks.

~~ Pierre

 PeterS had stated

"Please note carefully: The main problems with most VAWT are that they allow blade stall and they produce a narrow and sharply peaked Cp curve. So they are not nearly as good as they could be at capturing the large amount of energy in wind gusts. When a gust hits, they lose a lot of that energy. But according to my informal observations and the hundreds of research papers I have read, the Sharp Cycloturbine should be able to capture most of the additional energy in wind gusts because the blades don’t stall, they react quickly to changes in the velocity of their apparent wind, and the torque curve is very wide. So when I refer to VAWT, I usually have the Sharp Cycloturbine in mind unless I indicate otherwise."

 


Group: AirborneWindEnergy Message: 22731 From: dave santos Date: 5/30/2017
Subject: Re: Kite String and Effective String Theory
If Doug does not see advanced kite physics as a rich source of paradoxes, at least he knows one person who does.

Tow ropes in fact do move with respect to the media or global frame, and that to do any work the rope must first load up with energy of tension (zero-point energy), which adds thermodynamic order while reducing entropy, and that high phonon energy is being transmitted from point a to point b, without loss. A rope simply in static tension may be just as cool, but is not transmitting any energy.

The engineering paradox is that force super-conductance is normally considered as an exotic electrical mode, but somehow ordinary rope does super-conductance too. A drive shaft has similar super-conductance, but with poorer power-to-mass performance.

On ‎Tuesday‎, ‎May‎ ‎30‎, ‎2017‎ ‎05‎:‎36‎:‎27‎ ‎PM‎ ‎CDT, dougselsam@gmail.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

DaveS noted: " - Recall the 2007 starting paradox, how a ship towing hawser (or kite tether) can transmit ~10MW at 100% efficiency over a large distance, yet remain cool to the touch (!)."

DougS remarks: *** I do not know of anyone else who would call it a paradox that a rope towing something does not heat up, due to energy of force x distance.   ("Perpetual motion"?)

Stationary reference frame: The energy put in at one end of the rope is extracted from the other end, so, no net energy remaining in the rope, no heating expected.

Moving reference frame:  force applied, no relative distance moved, so force x distance = 0, no net energy used.

Placing a rope under tension is not a constant source of heat for the rope, no matter the chosen frame of reference.  This has never been seen as a paradox, as far as I know.  Seems like a case of thinking too hard, but not thoroughly.

Group: AirborneWindEnergy Message: 22732 From: Peter A. Sharp Date: 5/31/2017
Subject: Sharp VAWT

Hi Pierre,

You asked about blade stall and the narrow coefficient of performance curves (Cp) of most VAWT.

To start off, take a look at the Cp curves in Figure 2.11 on page 24 in this paper by Chougule (2015 PhD thesis): “Innovative Design of a Darrieus Straight Bladed Vertical Axis Wind Turbine by using Multi Element Airfoil”. The URL usually doesn’t work, so it needs to be searched for on Google. Note that the label underneath the horizontal line in that figure reads “Wind Speed”. That’s an error. It should read “Tip Speed Ratio”. Note how much wider the curve is for active pitching as opposed to fixed-blades and collective pitching (by which he means that the blades all use the same pitch schedule at all TSR). An example of a VAWT like that is the Pinson Cycloturbine which used a cam and pushrods to pitch the blades. That pitch control was accurate only at one TSR, which is why the curve is narrow and sharply peaked. The curve for the Sharp VAWT should be about the same as the active pitching curve on the left side of that curve, up to a Cp of about .45 where the curve would level off and then move downward on the right side about the same as the curve for the fixed-blades. What is desirable is a wide, flat section near the maximum Cp so that quick changes in the velocity of the wind have only a minor effect on the efficiency of the VAWT. A narrow, peaked curve indicates that the VAWT will seldom be operating at its maximum efficiency. So that basically answers your question. If you want more background information about VAWT, you can read the rest of my Email. If you want to learn about how the Sharp VAWT works, I have a paper about just that.

--------------------------

I’ll give you a quick overview of VAWT to put things in context. Most VAWT are lift-type Darrieus rotors and work similarly to the two VAWT that he patented in the US in 1931 after obtaining a French patent. One of his VAWTs is a fixed-blade eggbeater. The eggbeater typically spins at a TSR of 4 to 6. At that TSR, the blades don't stall because the angle of the apparent wind (the combination of the true wind and the relative wind created by the forward movement of the blade) is small and below the stall angle of the blades. In other words, the Cp curve is fairly flat and fairly broad at close to maximum. The best Cp max.so far is 0.46. The eggbeater typically has negative torque when starting and all the way up to a TSR above 2. That’s why they need a motor to get them started, or they need to be attached to a secondary wind turbine such as a Savonius rotor to provide starting torque. In my opinion, the most promising eggbeater is the Lux, which is moderate to large-scale and uses no blade support arms or central shaft because thin wires brace the blades to each other and make the rotor very stiff. The main problem is the large cantilever of the rotor above its base which requires guy wires and more land area, and the need for starting and braking mechanisms and a source of electricity.

The other Darrieus rotor is an H-rotor with a cycloidal pitch control that produces the same, cyclic pitching schedule all the time, regardless of the tip speed ratio. The amount of pitching is the same for upwind and downwind. That provides easy starting, but not a lot of torque except at one TSR where the fixed pitch schedule is just right for that TSR. That TSR will vary according to how much the blades pitch. The pitching H-rotor has a typical TSR of 3 to 3.5 as long as it uses a low moderate solidity ratio of about 0.2. The Cp max. is usually lower than for fixed blades because when the TSR exceeds roughly 3 because it is best that the blades do not pitch then in order to produce the highest angles of attack – just below stall.

HAWT are even better at preventing blade stall because they typically have a TSR of 5 to 7. But as they get larger, they take more time to turn toward the wind when the angle of the wind changes, as typically happens when the wind gusts. (So researchers are developing LIDAR systems for them to anticipate wind gusts.) HAWT have a broad Cp curve and the Cp max. is typically around 0.45 for small-scale HAWT, and up to 0.50 so far for large-scale HAWT. That is desirable because the rotor can maintain a high efficiency when the wind speed quickly speeds up or slows down. HAWT are really hard to beat. The Betz limit for a HAWT is 0.593.

VAWT have a higher Betz limit, but it should vary with the aspect ratio of the rotor. Wider seems to be better. So the max. Cp for VAWT is not yet fully worked out. In practice, the Cp will depend a lot on the type of VAWT. VAWT are quite varied.

Most current VAWT are some sort of H-rotor (rectangular swept area) because eggbeater blades can be more expensive to produce, and because eggbeaters require a lot of cantilever if they are mounted on towers where guy wires to the top of the VAWT are less easy to use. H-rotors come in many configurations. The blade support arms can be just one per blade, or two. If two, they can be placed at the tips of the blades or inward from the tips. A very tall VAWT might use multiple sets of support arms to help brace the blades against centrifugal force. The blades can be fixed, or they can use various types of blade-pitching. Blade pitching requires straight blades. Fixed blades can be helical, which smooths out the torque pulses and rotor drag pulses particularly well, but helical blades may be less efficient. Fixed-straight blades are now usually given a nose-out pre-pitch angle of 2 or 3 degrees so as to enable the rotor to self-start. Fixed-blades have very low or negative starting torque (like an eggbeater) unless pre-pitched.

The most efficient VAWT would be an H-rotor with motors to pitch each blade individually, with the motors controlled by a computer using wind sensors mounted on the VAWT. A few have been constructed for sale, but they are expensive and have reduced reliability due to so many high-tech parts. They can have high starting torque, strong running torque, and an especially broad Cp curve, as can be seen in the Chougule curve mentioned above. The Cp max should be higher than for HAWT, but different studies predict different Cp max., ranging from about 0.52 to about 0.60. The flow of wind through a VAWT with blade pitching is extremely complex. So predictions can vary a lot depending upon what flow model is used and precisely what the pitching angles are. Difference of one degree can be significant. HAWT are now moving toward blade pitching in order to maximize their response to quick changes in the velocity (speed and direction) of the wind, including wind gusts. Computer pitching is best for VAWT close to 100 kW and above because small VAWT spin too fast for the blades to have time to pitch correctly

There are about 10 ways to pitch VAWT blades, but most of them don’t work very well. In addition to computer-pitching, one way that works fairly well is cyclic pitching where the pitch schedule is constantly changed to match the TSR. That can be done actively, or passively (the Blackhawk VAWT). But that kind of pitching is usually moderately expensive to achieve. Passive-pitching can work quite well, but most passive-pitching VAWT use an inefficient type of pitch-control. Only the Sharp VAWT and the Verastegui VAWTs work well. The Verastegui VAWT uses aerodynamic pitching, but it requires three pairs of blades and precision parts, so it would be expensive.

The Sharp VAWT uses a variety of shapes (including V-blades), but it’s basically an H-rotor. It is not a Darrieus rotor nor a Darrieus rotor derivative. Each blade-unit pitches itself using passive pitch-control. There is no additional pitching mechanism required. The reason the Sharp VAWT works well is that its centrifugal pendulum spring is exceptionally strong – because the blade itself is part of the pendulum bob. I have a paper on how the Sharp VAWT works if you get interested. The pitch schedule is infinitely variable. In other words, each blade determines the best pitch angle for each azimuth and each local TSR, and they can adjust quickly to changes in the velocity of the wind, including gusts. The Cp max is predicted by various studies of passive pitching VAWT to be 0.45, or slightly less than for fixed-blades. That is because the Sharp blades still pitch a tiny bit above a TSR of roughly 3. And the blades can’t pitch as precisely as computer pitching. Optimum computer pitching requires the blades to pitch in small ways that the Sharp VAWT cannot do. But the Sharp VAWT seems to have a Cp curve that is almost as wide as computer pitching at a TSR below 3.5, although the curve is not as high (.45 vs. .52). However, with tipping, the Cpe curve (“equivalent Cp”, my term) should exceed the max. of the Cp curve for computer pitching. And other techniques may further increase the height of the its Cpe curve. Since the pitch-control costs almost nothing, and there is almost nothing to wear out, the Sharp VAWT offers the best compromise between efficiency, versatility, durability, and low cost. It’s easy and cheap to make.

During start-up, most VAWT blades stall over a wide azimuth angle arc and so produce only low torque, if any, during start-up. The Sharp VAWT uses blade stall during start-up to produce strong starting torque. For most VAWT, if a strong wind gust hits the VAWT when it is at its design TSR, that will drop the TSR, so the blades will stall at certain azimuth angles and lower the Cp. They have narrow, peaked Cp curves, so dropping the TSR, or raising the TSR (due to a sudden lull), can greatly reduce the Cp. N.C.K. Pawsey in his 2002 PhD thesis calculated the typical drop would be about 28% as compared to accurate passive pitching which would have a drop of only about 10%. So most of the time, A Sharp VAWT would be operating at a higher Cp than fixed-blades or collective-pitching blades. If VAWT blades don’t pitch, or if they have a fixed pitch-schedule, the whole rotor needs to speed up to get the blades back up to a TSR where the blade will be below stall at all azimuth angles. But the Sharp blades just pitch quickly and considerably increase the torque, so as to quickly accelerate the VAWT, while storing the gust energy in the “flywheel” that is the VAWT. My models reach maximum torque at a TSR of 2, which is quite unusual and quite useful for capturing gust energy. Similarly, if a lull hits, the blades stop pitching, and coast (like fixed-blades) until there is enough wind energy to pitch the blades at the TSR they are at.

High efficiency and a broad Cp curve are important. But of most importance is high reliability (including low maintenance) especially in high winds. Next comes a low first-cost. Other factors are low shipping and installation costs, minimum land use, ease of service (access to the rotor) and low service costs, low insurance, plus easy access to parts and repairmen. A good guarantee is important, but only if you can actually get the service and the parts when you need them. Proper zoning and permits are needed, including height limitations and radar interference regulations. Then there are neighbor-friendly factors, such as quite running, a low number of bird and bat strikes, safety to people and animals from thrown blades or fallen towers, minimal shadow casting and shadow flicker, and beauty and/or unobtrusiveness, plus the “wow” factor and/or the curiosity factor. And finally comes a good resale value. Small-scale energy kites should be subject to the same considerations.

PeterS

 

 

 

 

 

 

 

 

 

 

 

Group: AirborneWindEnergy Message: 22733 From: Peter A. Sharp Date: 5/31/2017
Subject: Re: Kite String and Effective String Theory
I agree with DougS's analysis. Judging from DaveS's response, DaveS does not
understand the concept of frames of reference, and so cannot understand
DougS's analysis.
PeterS
Group: AirborneWindEnergy Message: 22734 From: Peter A. Sharp Date: 5/31/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp
Hi DougS,
Thanks for your response. And special thanks for that information about the
Bergey 10 kW machine. Enlightening information for me.
I'm glad to hear that you have an open mind on the future of VAWT, despite
all the failures.
If you would like to discuss your VAWT concept confidentially, feel free to
contact me in private. It would be great fun. I would sign a non-disclosure
agreement if you wished. I have had a lot of practice at analyzing new VAWT
concepts and finding the hidden flaws in PhD theses that aerodynamicists
have missed. If your VAWT is better than the Sharp VAWT, I would be
disappointed personally, but delighted for you and for the wind industry.
I agree that lots of people make claims about new VAWT innovations that
don't hold up. I hope that I'm not one of them. If you question anything I
say, I would very much appreciate your telling me so. I value your comments.
And I find that I inevitably learn something when what I say is challenged.
It forces me to think more deeply and more carefully.
PeterS
Group: AirborneWindEnergy Message: 22735 From: joe_f_90032 Date: 5/31/2017
Subject: Re: World looking at AWE

Kitty Knowles is a Senior Features Writer at The Memo; she composed a confident note: 

Kite wind farms take off in UK as future of energy

BY KITTY KNOWLES 30 MAY 2017

She concluded with " There is great potential for the sector:

Its rise won’t be a case of ‘if’ but ‘when’."



Group: AirborneWindEnergy Message: 22736 From: joe_f_90032 Date: 5/31/2017
Subject: Comparing Patent and Scientific Literature in Airborne Wind Energy

Sustainability 20179(6), 915; doi: 10.3390/su9060915

Review
Comparing Patent and Scientific Literature in Airborne Wind Energy
Anny Key de Souza Mendonça *, Caroline Rodrigues Vaz, Álvaro Guillermo Rojas Lezana, Cristiane Alves Anacleto and Edson Pacheco Paladini
Department of Industrial and Systems Engineering, Federal University of Santa Catarina, Florianópolis, 88040-900 Santa Catarina, Brazil
*
Correspondence: Tel.: +55-48-3721-7024
Academic Editor: Tomonobu Senjyu
Received: 20 February 2017 / Accepted: 25 May 2017 / Published: 31 May 2017


Group: AirborneWindEnergy Message: 22737 From: joe_f_90032 Date: 5/31/2017
Subject: Re: Jian Dai

Another by: 

High altitude generator apparatus 

WO 2013097578 A1


DAI, Ning [CN/CN]; (CN).

DAI, Jian [AR/CN]; (CN).


Group: AirborneWindEnergy Message: 22738 From: dave santos Date: 6/1/2017
Subject: Re: Kite String and Effective String Theory

Correction to both Doug and PeterS then- A tow-rope really does move compared to a static rope under the same tension. I strongly disagree with Doug's general view that kite physics is not amazing. Even 17th century kite physics was amazing, and flourishing 21st century physics just adds wonder on wonder-


On ‎Wednesday‎, ‎May‎ ‎31‎, ‎2017‎ ‎12‎:‎45‎:‎15‎ ‎PM‎ ‎CDT, 'Peter A. Sharp' sharpencil@sbcglobal.net [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

I agree with DougS's analysis. Judging from DaveS's response, DaveS does not
understand the concept of frames of reference, and so cannot understand
DougS's analysis.
PeterS

Group: AirborneWindEnergy Message: 22739 From: dave santos Date: 6/1/2017
Subject: Re: Sharp Intermeshing VAWT; Sharp VAWT with Flyball Governor; Sharp
Note that Fry & Hise, and Harburg, are the older trail of prior patent art in tilted-axis multi-rotor AWES category.

On ‎Wednesday‎, ‎May‎ ‎31‎, ‎2017‎ ‎12‎:‎48‎:‎11‎ ‎PM‎ ‎CDT, 'Peter A. Sharp' sharpencil@sbcglobal.net [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

Hi DougS,
Thanks for your response. And special thanks for that information about the
Bergey 10 kW machine. Enlightening information for me.
I'm glad to hear that you have an open mind on the future of VAWT, despite
all the failures.
If you would like to discuss your VAWT concept confidentially, feel free to
contact me in private. It would be great fun. I would sign a non-disclosure
agreement if you wished. I have had a lot of practice at analyzing new VAWT
concepts and finding the hidden flaws in PhD theses that aerodynamicists
have missed. If your VAWT is better than the Sharp VAWT, I would be
disappointed personally, but delighted for you and for the wind industry.
I agree that lots of people make claims about new VAWT innovations that
don't hold up. I hope that I'm not one of them. If you question anything I
say, I would very much appreciate your telling me so. I value your comments.
And I find that I inevitably learn something when what I say is challenged.
It forces me to think more deeply and more carefully.
PeterS

Group: AirborneWindEnergy Message: 22740 From: benhaiemp Date: 6/1/2017
Subject: Re: Sharp VAWT
Thanks for the informations PeterS. Indeed I saw your correction of the mentioned paper. Please can you detail the curve both for Sharp VAWT and VAWT at different pitch control types, providing drawings if possible. Precisely why Sharp VAWT curve can be as wide as individual pitch control VAWT, adding CP of about .45? Thanks.
Group: AirborneWindEnergy Message: 22742 From: joe_f_90032 Date: 6/2/2017
Subject: Re: Sharp VAWT

This links to a PDF on Peter A. Sharp's VAWT   ... How it works.


http://tinyurl.com/SharpVAWT


Group: AirborneWindEnergy Message: 22743 From: dougselsam Date: 6/2/2017
Subject: Re: Kite String and Effective String Theory
I strongly disagree with Doug's general view that kite physics is not amazing."
*** Dave with all due respect, that is a typical example of what you so often decry: constructing a "straw-man" to argue against.
I explained why a tow rope does not experience significant heating by virtue of moving under tension.  Simple physics says you can look at it in any reference frame, including the reference frame of the two boats, wherein the boats are considered as stationary with the rest of the world (universe) moving.
The entire world around you is under either compression or tension, and, depending on frames of reference chosen, could be considered "in-motion", yet everything around you is not undergoing constant heating by virtue of a force traveling over a distance. I have never known anyone to consider this a paradox.
Anyway, trying to counter such simple and well-known facts that a rope under tension does not thereby undergo heating, by saying I have a general view that kites are not amazing, does not have any logical basis, and is also very wrong.  I have always been a huge fan of kites, and even sometimes fly under a man-carrying kite for fun.  Why anyone would claim I am somehow against kites I cannot fathom.  I just don't subscribe to the notion that "everything is a kite".  For example the anchors to my wind turbine guy wires are not kites, or "wings" in my opinion.  Most engineers would agree with that opinion.
Group: AirborneWindEnergy Message: 22744 From: Peter A. Sharp Date: 6/2/2017
Subject: Re: Sharp VAWT

Hi PierreB,

Per your request, I'll ask JoeF to please post my paper on how the Sharp VAWT works because it contains my approximated Cp curve for the Sharp VAWT combined with the 3 curves from Chougule. The curves are not exact duplicates of Chougule’s because it's hard to draw curves exactly when using my CAD program. But they are close enough to show the comparisons.

Note that the Sharp VAWT uses passive, individual blade pitch control, just like the active pitch computer control.

The reason that the Sharp VAWT is not quite as accurate as the active, computer pitch control is that the Sharp VAWT blades only pitch nose-out when upwind and only nose-in when downwind. But active pitch control can add a bit of nose-in when just starting the upwind pass, and a bit of nose-out when just finishing the downwind pass. By doing so, the computer pitch control can produce a higher angle of attack at those two points, and therefore additional thrust and torque. But the blades have to pitch very quickly, and that would be difficult for the motors to handle for smaller VAWT.

Also, when operating at a higher TSR above about 3.5, the computer control can keep the angle of attack larger than is possible for the Sharp VAWT, which functions like a fixed-blade VAWT at those higher TSR. At the lower TSR below about 3, the Sharp blades can pitch a large amount and they can pitch very quickly because they store energy to be used for pitching. So then the Sharp VAWT can pitch just about as well as computer pitching at the lower TSR. The computer control might be able to produce a starting torque that is a little higher than can the Sharp VAWT, but there are many factors to consider, and the starting torque of the Sharp VAWT can be further optimized if it were necessary to do so.

In sizes of 1 kW and less, I could probably make a Sharp rotor, not including the generator, for about 1/5 of the cost of a computer controlled VAWT. That advantage gets smaller as the sizes of the VAWT increase up to about somewhere around 50 to 100 kW. After that, the computer controlled VAWT would still cost a lot more, but its additional energy production would compensate – as long as it was reliable, and that is still an open question. The Sharp VAWT should be quite reliable because it is so simple and because the blades experience reduced stresses due to the fact that they are free-floating and have built-in shock absorbers if they use cord bearings.

PeterS

Group: AirborneWindEnergy Message: 22745 From: Peter A. Sharp Date: 6/2/2017
Subject: Re: Kite String and Effective String Theory
I concur with DougS. DaveS's straw-man argument is also, once again, a
personal attack -- in the form of an accusatory characterization of DougS.
A fundamental principle in physics is the equivalence of all inertial frames
of reference. DaveS can research that topic if he wants to understand his
error. Thinking about frames of reference can be confusing. Understanding
many of my inventions involves shifting frames of reference. I found that
thinking about them requires practice. Sometimes they can be
counter-intuitive. So DaveS is not alone in having some trouble
understanding them.
I appreciate the courtesy and clarity of DougS's response.
PeterS
--------------
DaveS: "I strongly disagree with Doug's general view that kite physics is
not amazing."
DougS: *** Dave with all due respect, that is a typical example of what you
so often decry: constructing a "straw-man" to argue against.
I explained why a tow rope does not experience significant heating by virtue
of moving under tension. Simple physics says you can look at it in any
reference frame, including the reference frame of the two boats, wherein the
boats are considered as stationary with the rest of the world (universe)
moving.
The entire world around you is under either compression or tension, and,
depending on frames of reference chosen, could be considered "in-motion",
yet everything around you is not undergoing constant heating by virtue of a
force traveling over a distance. I have never known anyone to consider this
a paradox.
Anyway, trying to counter such simple and well-known facts that a rope under
tension does not thereby undergo heating, by saying I have a general view
that kites are not amazing, does not have any logical basis, and is also
very wrong. I have always been a huge fan of kites, and even sometimes fly
under a man-carrying kite for fun. Why anyone would claim I am somehow
against kites I cannot fathom. I just don't subscribe to the notion that
"everything is a kite". For example the anchors to my wind turbine guy
wires are not kites, or "wings" in my opinion. Most engineers would agree
with that opinion.
Group: AirborneWindEnergy Message: 22746 From: benhaiemp Date: 6/2/2017
Subject: Re: Sharp VAWT

I am beginning to read, again and better, Sharp's paper. I have some questions for now and later.

As VAWT the masses are as external as possible, making it a suitable configuration for centrifugally stiffened rotor. But probably PeterS already produced such a remark, and the same for the followed question. 

Is this rotor also studied as it is tilted? What are comparison with tilted HAWT like SuperTurbine (tm)?

I thank both DougS and PeterS as they produce real and interesting contains with a courtesy tone.


Pierre

Group: AirborneWindEnergy Message: 22747 From: joe_f_90032 Date: 6/2/2017
Subject: Kitewinder's news on ground generator
Group: AirborneWindEnergy Message: 22748 From: joe_f_90032 Date: 6/2/2017
Subject: Kitewinder will be at the O'zenergie event

Kitewinder will be at the O'zenergie event

=====================================

We will be at the O'zenergie to introduce you to KiweeOne !

Join us on August 11, 12 & 13  of 2017, at Séranon (06, France) !

Group: AirborneWindEnergy Message: 22749 From: dave santos Date: 6/2/2017
Subject: Re: Kite String and Effective String Theory
PeteS,

If you review the AWES Forum, its Doug who mostly made personal attacks, and more crudely, than anyone, if you really care on that point. I have perhaps mistakenly concluded that Doug is not excited about advanced kite physics after hundreds of messages over a decade, where his characteristic take on kites and kite energy is fatalistic despair. Let anyone show where Doug has ever shown delight over the physics of flight, and I will happily stand corrected.

As for intertial frames of reference, I stand by Wikipedia, that all frames of reference are moving under Galilean Relativity. Its an illusion or idealization if a frame of reference seems stationary. You and Doug seem claim the tow rope does not move, "Yet it does move", as Galileo said. Doug is even confusing a tow-rope physics with "perpetual motion".

It would be great if you and Doug help advance the shappiypecific topic of effective string theory for possible AWE insights, not just call into doubt Wikipedia on inertial reference frames, and feel unfairly misunderstood by everyone,

daveS



On ‎Friday‎, ‎June‎ ‎02‎, ‎2017‎ ‎12‎:‎06‎:‎43‎ ‎PM‎ ‎CDT, 'Peter A. Sharp' sharpencil@sbcglobal.net [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

I concur with DougS. DaveS's straw-man argument is also, once again, a
personal attack -- in the form of an accusatory characterization of DougS.
A fundamental principle in physics is the equivalence of all inertial frames
of reference. DaveS can research that topic if he wants to understand his
error. Thinking about frames of reference can be confusing. Understanding
many of my inventions involves shifting frames of reference. I found that
thinking about them requires practice. Sometimes they can be
counter-intuitive. So DaveS is not alone in having some trouble
understanding them.
I appreciate the courtesy and clarity of DougS's response.
PeterS
--------------
DaveS: "I strongly disagree with Doug's general view that kite physics is
not amazing."
DougS: *** Dave with all due respect, that is a typical example of what you
so often decry: constructing a "straw-man" to argue against.
I explained why a tow rope does not experience significant heating by virtue
of moving under tension. Simple physics says you can look at it in any
reference frame, including the reference frame of the two boats, wherein the
boats are considered as stationary with the rest of the world (universe)
moving.
The entire world around you is under either compression or tension, and,
depending on frames of reference chosen, could be considered "in-motion",
yet everything around you is not undergoing constant heating by virtue of a
force traveling over a distance. I have never known anyone to consider this
a paradox.
Anyway, trying to counter such simple and well-known facts that a rope under
tension does not thereby undergo heating, by saying I have a general view
that kites are not amazing, does not have any logical basis, and is also
very wrong. I have always been a huge fan of kites, and even sometimes fly
under a man-carrying kite for fun. Why anyone would claim I am somehow
against kites I cannot fathom. I just don't subscribe to the notion that
"everything is a kite". For example the anchors to my wind turbine guy
wires are not kites, or "wings" in my opinion. Most engineers would agree
with that opinion.

Group: AirborneWindEnergy Message: 22750 From: dave santos Date: 6/2/2017
Subject: Re: Kite String and Effective String Theory
Perhaps a review of old discussion will help understanding.

Compare two ships with an electrical transmission line between them, rather than a tow rope of equivalent length. One ship can transmit electrical power to the other, for tow-equivalent motor-propulsion, but there will be considerable continuous heat loss in the conductors, or they will be very massive, unless they are superconducting, which is still impractical. The lighter cheaper TRL9 tow rope is effectively superconducting. Similarly, if Effective String Theory in physics is applied to kites, the superconducting state is included.

Superfluidity is a similar case class, and our high-tech lines are formally liquid-crystal. Its standard practice to extend physics by analogy. Its not productive to complain over this. As for how someone deeply passionate about physics expresses the joy, Feynman has us spoiled. Doug seems to find joy in not reading AWE physics classics, like Loyd's seminal paper. One can't grok advanced kite physics without doing the homework, and it helps to find joy in it. Effective String Theory is a legitimate kite topic for the prepared mind.

How theories in physics are extended in new directions, with phonons as the apt example-




On ‎Friday‎, ‎June‎ ‎02‎, ‎2017‎ ‎03‎:‎04‎:‎06‎ ‎PM‎ ‎CDT, dave santos santos137@yahoo.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

PeteS,

If you review the AWES Forum, its Doug who mostly made personal attacks, and more crudely, than anyone, if you really care on that point. I have perhaps mistakenly concluded that Doug is not excited about advanced kite physics after hundreds of messages over a decade, where his characteristic take on kites and kite energy is fatalistic despair. Let anyone show where Doug has ever shown delight over the physics of flight, and I will happily stand corrected.

As for intertial frames of reference, I stand by Wikipedia, that all frames of reference are moving under Galilean Relativity. Its an illusion or idealization if a frame of reference seems stationary. You and Doug seem claim the tow rope does not move, "Yet it does move", as Galileo said. Doug is even confusing a tow-rope physics with "perpetual motion".

It would be great if you and Doug help advance the shappiypecific topic of effective string theory for possible AWE insights, not just call into doubt Wikipedia on inertial reference frames, and feel unfairly misunderstood by everyone,

daveS



On ‎Friday‎, ‎June‎ ‎02‎, ‎2017‎ ‎12‎:‎06‎:‎43‎ ‎PM‎ ‎CDT, 'Peter A. Sharp' sharpencil@sbcglobal.net [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

I concur with DougS. DaveS's straw-man argument is also, once again, a
personal attack -- in the form of an accusatory characterization of DougS.
A fundamental principle in physics is the equivalence of all inertial frames
of reference. DaveS can research that topic if he wants to understand his
error. Thinking about frames of reference can be confusing. Understanding
many of my inventions involves shifting frames of reference. I found that
thinking about them requires practice. Sometimes they can be
counter-intuitive. So DaveS is not alone in having some trouble
understanding them.
I appreciate the courtesy and clarity of DougS's response.
PeterS
--------------
DaveS: "I strongly disagree with Doug's general view that kite physics is
not amazing."
DougS: *** Dave with all due respect, that is a typical example of what you
so often decry: constructing a "straw-man" to argue against.
I explained why a tow rope does not experience significant heating by virtue
of moving under tension. Simple physics says you can look at it in any
reference frame, including the reference frame of the two boats, wherein the
boats are considered as stationary with the rest of the world (universe)
moving.
The entire world around you is under either compression or tension, and,
depending on frames of reference chosen, could be considered "in-motion",
yet everything around you is not undergoing constant heating by virtue of a
force traveling over a distance. I have never known anyone to consider this
a paradox.
Anyway, trying to counter such simple and well-known facts that a rope under
tension does not thereby undergo heating, by saying I have a general view
that kites are not amazing, does not have any logical basis, and is also
very wrong. I have always been a huge fan of kites, and even sometimes fly
under a man-carrying kite for fun. Why anyone would claim I am somehow
against kites I cannot fathom. I just don't subscribe to the notion that
"everything is a kite". For example the anchors to my wind turbine guy
wires are not kites, or "wings" in my opinion. Most engineers would agree
with that opinion.

Group: AirborneWindEnergy Message: 22751 From: olivierabristol Date: 6/3/2017
Subject: Re: Kitewinder's KiweeOne product nears release
Thanks Joe for reposting our news. It could be helpful for us to have some feedback about our ground generator.
Some infos :  It's an aluminium and stainless steel casing weighing around 1.5 kg. Equipped with a planetary gearbox brushless DC motor that can act as generator or as motor for retrieval operation.
It is equipped with a 120 meters dyneema loop but you can store up to 250 meters if needed.
The electronics box does not appears yet but it is linked to the ground generator through a 1.5 meter cable. You can have a 13.8 Volts outptut ( car plug style ) or a 220Volts AC output ( universal ) depending on your needs. It also contains a 100Wh battery for minigrid needs and retrieval operation.
220 AC output will be a little more costly as it needs more electronics than 13.8 Volts output.

The ground station is automatic, it detects low wind and self retract by itself.  
under strong winds you can also retract with the manual winch and the help of the motor. 
We will display some videos soon so that  you can see it at work for real .

So what do you think about our Kiwee ground generator ? Do you like the design ? do you like the features ?

Olivier 
Group: AirborneWindEnergy Message: 22752 From: joe_f_90032 Date: 6/3/2017
Subject: Re: Kitewinder's KiweeOne product nears release

Congrats! Exciting!.

Some starts.

Q1. Grounding and electrical safety text for user?

Q2. Suppose lull from gust followed by sustaining wind occurs: Would self-retraction start and then stop for resuming regular generation?


JoeF
Group: AirborneWindEnergy Message: 22753 From: olivierabristol Date: 6/3/2017
Subject: Re: Kitewinder's KiweeOne product nears release
Not sure I understand well Q1 but I try to answer anyway :

We have many built in electrical protection :

Battery Management System
Maximum Power Point Tracking function
Electronic System Control for BLDC
Automatic Braking Control to prevent overcharge

All the electronics have a protective coating for waterproofing and the casing are also watertight
We use aeronautical standard for testing and dimensioning (DO160 standards)

Q2 :  Here is the strategy based on roughly 100 hours of flight .
If lull from gust occurs , first we stop the electric generation and check how Kiwee reacts. Has the aeronautical drag of the blades decrease the elevation angle usually ( always to be true ) increase.  If the elevation angle remains in a acceptable windows, we just wait and see, ready to re start the electric generation.
If after blades stop the elevation angle is still not acceptable for a definite time ( that can be tuned but it is around 30 seconds ) , then we self retract.
this way you are sure to have kiwee at 5 meters around you and ready to restart when the wind comes back.
Group: AirborneWindEnergy Message: 22754 From: Peter A. Sharp Date: 6/3/2017
Subject: Re: Sharp VAWT
Hi PierreB,

PierreB: "As VAWT the masses are as external as possible, making it a
suitable configuration for centrifugally stiffened rotor."
Answer: Yes, that is correct. By using the blade as part of the weight of
the centrifugal pendulum spring, the Sharp blade-unit can produce an
especially high centrifugal restoring force to resist pitching. Other
passive-pitching systems that use centrifugal springs of some sort tend to
be much weaker, so the blade's pitch too much and the angle of attack is too
low for maximum thrust.

PierreB: "Is this rotor also studied as it is tilted?
Answer: Yes, I have tilted Sharp Cycloturbine models to stop them. What I
discovered is that they can be tipped to about 20 degrees, but further
tilting will begin to noticeably disrupt the pitch control. That is one
reason that I like the idea of using very wide rotors because they can
increase their swept area a lot while tilting less than 20 degrees.

PierreB: "What are comparison with tilted HAWT like SuperTurbine (tm)?"
Answer: Both the Sharp VAWT (and all VAWT with a rectangular swept area) and
the SuperTurbine(R) can be tilted to expose additional swept area to clean
air. The SuperTurbine can expose an essentially unlimited amount of
additional swept area to clean air, whereas the Sharp VAWT is much more
limited -- probably to a maximum 50% increase in swept area for a very wide
VAWT
However, the Sharp VAWT can be stacked vertically with many rotors
separated by a gap, so in that sense it is similar to a SuperTurbine(R).
Dynamically balanced Sharp VAWTs could be mounted along a horizontal shaft
and perpendicular to the wind, plus a tilt-back angle, and gaps between the
rotors to take advantage of the tilt-back angle. That would be even more
similar to the SuperTurbine(R) concept.
However, it would be more practical to eliminate the gaps between
Sharp VAWT that were stacked along the same shaft -- vertically or
horizontally -- because that would provide a greater swept area than tilting
would provide. So stacked Sharp VAWT, whether vertical or horizontal, should
not use tilting for that reason.
The SuperTurbine(R) is intended to maximize the rpm that can be
obtained from a given swept area. That is important because as HAWT become
larger in diameter to increase their swept area, their rpm decreases, thus
increasing the cost of the gearing and/or the size of a direct-drive
generator. By increasing the rpm, the generator can be much smaller and
cheaper for a given swept area. The many small rotors may also be cheaper
than one big rotor due to the square-cube law of scaling. It's an ingenious
solution. The downside is a loss of perhaps 20% in efficiency due to the
reduced swept area of the HAWT rotors when tilted. But that can be overcome
by simply adding more rotors along the shaft to compensate.
A Sharp VAWT can be stacked for the same reason. A tall stack of
Sharp VAWT can spin faster than a conventional HAWT rotor. Most VAWT (if
they are all the same diameter) cannot be stacked vertically without
sacrificing some efficiency due to the wind gradient. The Sharp VAWT has a
broad performance curve, so it can afford to have the top VAWT in the stack
operating at the same rpm but at a lower TSR than the bottom VAWT without
sacrificing much efficiency. The SuperTurbine(R) operates with all of the
rotors at about the same height, so the wind gradient is relevant only in
terms of the height of the tower. That would be true as well for a
horizontally stacked VAWT.
If a horizontal stack of VAWT is compared to a SuperTurbine(R), and
if they both use the same rotor diameter and the same shaft length, the VAWT
stack will produce more power (due to closer spacing of the rotors) but the
SuperTurbine(R) stack will have about twice the rpm. If the VAWT rotors were
half the diameter of the HAWT rotors, both stacks would have about the same
rpm, and their power would be more equal, depending upon the optimum spacing
of the HAWT rotors. This assumes that both have the same efficiency. But I
would prefer the SuperTurbine for its simplicity since dynamically balanced
Sharp VAWT are more complex than a standard Sharp VAWT. Fixed-blade VAWT
could be stacked horizontally as long as they used some sort of starting
device, and they would be simpler than a horizontal stack of dynamically
balanced Sharp VAWT.
As you can see, comparisons can get pretty complicated.
If DougS spots an error or omission in what I said, I invite him to
correct me because I do not wish to misrepresent his SuperTurbine(R) in any
way.
PeterS
Group: AirborneWindEnergy Message: 22755 From: dave santos Date: 6/5/2017
Subject: Re: Kitewinder's KiweeOne product nears release
There is little electrical risk from the Kitewinder generator at the inherent low voltage and wattage specified.

The remaining major risk factors are dropped-mass risk and blade-strike to an eye. The turbine should be well secured to the lifter-kite, with the drive-loop as the weak-link, so that the unit glides down in a break-away. Rigid turbine blades should be preplaced by safer softer versions, like EPP foam or fabric sail on a carbon tube, with nearly as good performance at far lower cost..




On ‎Saturday‎, ‎June‎ ‎03‎, ‎2017‎ ‎10‎:‎48‎:‎37‎ ‎AM‎ ‎CDT, olivierabristol@yahoo.fr [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

Not sure I understand well Q1 but I try to answer anyway :


We have many built in electrical protection :

Battery Management System
Maximum Power Point Tracking function
Electronic System Control for BLDC
Automatic Braking Control to prevent overcharge

All the electronics have a protective coating for waterproofing and the casing are also watertight
We use aeronautical standard for testing and dimensioning (DO160 standards)

Q2 :  Here is the strategy based on roughly 100 hours of flight .
If lull from gust occurs , first we stop the electric generation and check how Kiwee reacts. Has the aeronautical drag of the blades decrease the elevation angle usually ( always to be true ) increase.  If the elevation angle remains in a acceptable windows, we just wait and see, ready to re start the electric generation.
If after blades stop the elevation angle is still not acceptable for a definite time ( that can be tuned but it is around 30 seconds ) , then we self retract.
this way you are sure to have kiwee at 5 meters around you and ready to restart when the wind comes back.
Group: AirborneWindEnergy Message: 22756 From: Uwe Fechner Date: 6/5/2017
Subject: Summer job for C/C++ programmer on flight control

Hello,

we are looking for someone, who can spend 2 months in Den Haag to help use with the development
of a new flight control software for rigid wing kite power systems.

This job might be suitable for students, if they can decide quickly and can come to The Netherlands
not later than 15th of June.

For details see:

https://www.linkedin.com/jobs/cap/view/305661450

We are making airborne wind energy work!

Uwe

-------------------------------
Dr. Uwe Fechner

aenarete - Wind Drones
Paets van Troostwijkstraat 277
2522DT Den Haag

www.aenarete.eu Tel.: 06-2529-2059


Group: AirborneWindEnergy Message: 22757 From: dougselsam Date: 6/5/2017
Subject: Re: Kite String and Effective String Theory
DaveS said:
"Perhaps a review of old discussion will help understanding.  Compare two ships with an electrical transmission line between them, rather than a tow rope of equivalent length. One ship can transmit electrical power to the other, for tow-equivalent motor-propulsion, but there will be considerable continuous heat loss in the conductors, or they will be very massive, unless they are superconducting, which is still impractical."

DougS remarks:
*** You implied that the losses in a rope should equal tension x distance = like Loyd's seminal paper. One can't grok advanced kite physics without doing the homework, and it helps to find joy in it. Effective String Theory is a legitimate kite topic for the prepared mind."

DougS remarks:
*** This would appear to be one more personal attack, and an inaccurate attack at that.  I didn't need to read a "paper" explaining the obvious, that is true.  I don't need to read a paper explaining that one can safely cross a street, nor that 2 + 2 = 4.  Loyd's paper was published in 1980, AFTER I had already understood the concept of crosswind kite power and, with the laddermill concept already invented by me a few years earlier, I had already, by that time, invented SuperTurbine(R).  So it was already old information for me when published.  Some things are obvious and do not require reading a paper to understand, for those with the requisite background.  With my previous history of flying model airplanes, sailing, hang-gliding, and building and flying kites, I was well-versed in aerodynamics and completely understood that wind power had transitioned to 100% crosswind power 2000 years earlier, and that "crosswind" was so germane to wind energy that it was seldom even mentioned, but simply taken for granted.   I have nothing against someone writing such a paper, and if others need to read that paper to understand what is in it, then that is fine for them, but in this case it did not apply to me.  Thank you for your opinion.

Group: AirborneWindEnergy Message: 22758 From: dave santos Date: 6/6/2017
Subject: Re: Kite String and Effective String Theory
Doug is mistaken. I am claiming that there is NO heating of the tow rope after its put in tension, same as the static non-towing rope under tension. A conventional electrical conductor would heat up in comparable transmission.

There does not seem to be any public record that Doug understood Loyd's crosswind power principle before the AWES Forum. His early laddermill would primarily move downwind and upwind as shown, and his ST is also angled away from the crosswind plane. Similarly, its not expected Doug can productively discuss effective string theory in this kite context without reading and understanding the science.


On ‎Monday‎, ‎June‎ ‎05‎, ‎2017‎ ‎03‎:‎40‎:‎19‎ ‎PM‎ ‎CDT, dougselsam@gmail.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

DaveS said:
"Perhaps a review of old discussion will help understanding.  Compare two ships with an electrical transmission line between them, rather than a tow rope of equivalent length. One ship can transmit electrical power to the other, for tow-equivalent motor-propulsion, but there will be considerable continuous heat loss in the conductors, or they will be very massive, unless they are superconducting, which is still impractical."

DougS remarks:
*** You implied that the losses in a rope should equal tension x distance = like Loyd's seminal paper. One can't grok advanced kite physics without doing the homework, and it helps to find joy in it. Effective String Theory is a legitimate kite topic for the prepared mind."

DougS remarks:
*** This would appear to be one more personal attack, and an inaccurate attack at that.  I didn't need to read a "paper" explaining the obvious, that is true.  I don't need to read a paper explaining that one can safely cross a street, nor that 2 + 2 = 4.  Loyd's paper was published in 1980, AFTER I had already understood the concept of crosswind kite power and, with the laddermill concept already invented by me a few years earlier, I had already, by that time, invented SuperTurbine(R).  So it was already old information for me when published.  Some things are obvious and do not require reading a paper to understand, for those with the requisite background.  With my previous history of flying model airplanes, sailing, hang-gliding, and building and flying kites, I was well-versed in aerodynamics and completely understood that wind power had transitioned to 100% crosswind power 2000 years earlier, and that "crosswind" was so germane to wind energy that it was seldom even mentioned, but simply taken for granted.   I have nothing against someone writing such a paper, and if others need to read that paper to understand what is in it, then that is fine for them, but in this case it did not apply to me.  Thank you for your opinion.

Group: AirborneWindEnergy Message: 22759 From: dave santos Date: 6/6/2017
Subject: Re: Kite String and Effective String Theory
Its not enough to only read the AWES Forum but not read extensive technical background knowledge.

Let's review the physics that meaningfully explains why the tow rope is such a formidable energy transmission media, starting with Debye. Follow the links to the extended physics. Its really wonderful how applicable kite physics is revealed by reading AND flying diligently.




On ‎Tuesday‎, ‎June‎ ‎06‎, ‎2017‎ ‎08‎:‎23‎:‎58‎ ‎AM‎ ‎CDT, dave santos santos137@yahoo.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

Doug is mistaken. I am claiming that there is NO heating of the tow rope after its put in tension, same as the static non-towing rope under tension. A conventional electrical conductor would heat up in comparable transmission.

There does not seem to be any public record that Doug understood Loyd's crosswind power principle before the AWES Forum. His early laddermill would primarily move downwind and upwind as shown, and his ST is also angled away from the crosswind plane. Similarly, its not expected Doug can productively discuss effective string theory in this kite context without reading and understanding the science.


On ‎Monday‎, ‎June‎ ‎05‎, ‎2017‎ ‎03‎:‎40‎:‎19‎ ‎PM‎ ‎CDT, dougselsam@gmail.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

DaveS said:
"Perhaps a review of old discussion will help understanding.  Compare two ships with an electrical transmission line between them, rather than a tow rope of equivalent length. One ship can transmit electrical power to the other, for tow-equivalent motor-propulsion, but there will be considerable continuous heat loss in the conductors, or they will be very massive, unless they are superconducting, which is still impractical."

DougS remarks:
*** You implied that the losses in a rope should equal tension x distance = like Loyd's seminal paper. One can't grok advanced kite physics without doing the homework, and it helps to find joy in it. Effective String Theory is a legitimate kite topic for the prepared mind."

DougS remarks:
*** This would appear to be one more personal attack, and an inaccurate attack at that.  I didn't need to read a "paper" explaining the obvious, that is true.  I don't need to read a paper explaining that one can safely cross a street, nor that 2 + 2 = 4.  Loyd's paper was published in 1980, AFTER I had already understood the concept of crosswind kite power and, with the laddermill concept already invented by me a few years earlier, I had already, by that time, invented SuperTurbine(R).  So it was already old information for me when published.  Some things are obvious and do not require reading a paper to understand, for those with the requisite background.  With my previous history of flying model airplanes, sailing, hang-gliding, and building and flying kites, I was well-versed in aerodynamics and completely understood that wind power had transitioned to 100% crosswind power 2000 years earlier, and that "crosswind" was so germane to wind energy that it was seldom even mentioned, but simply taken for granted.   I have nothing against someone writing such a paper, and if others need to read that paper to understand what is in it, then that is fine for them, but in this case it did not apply to me.  Thank you for your opinion.

Group: AirborneWindEnergy Message: 22760 From: Pierre BENHAIEM Date: 6/6/2017
Subject: Re: Sharp VAWT

Hi PeterS,

 

Thank for your detailed answer.

As the rotor is not too large, the centrifugal force can also allow to counter wind force, the rotor keeping its shape more or less.

 

PierreB

 

 

Group: AirborneWindEnergy Message: 22761 From: Pierre BENHAIEM Date: 6/6/2017
Subject: Re: Kite String and Effective String Theory

DougS provides a clear description of tension x distance, towing, heating, in the last posts. But his description is perhaps still not enough for DaveS' understanding. So DaveS could learn with basic documentation about frame of reference, about towing, about heating etc.

By the same all wind energy makers know _without telling it as it is too obvious_ that the blades work crosswind, even perfectly crosswing, unlike (partially crosswind) kites as M.Loyd mentions. In Loyd's paper the power calculation is connected to the kite area. In wind energy the power calculation is connected to the swept area.

It is good for both DaveS and me that specialists _PeterS and DougS_ in wind turbines now write on AWE forum. 

 

PierreB

 

 

 

Group: AirborneWindEnergy Message: 22762 From: Peter A. Sharp Date: 6/6/2017
Subject: Re: Sharp VAWT
Hi PierreB,
Pierre said, "As the rotor is not too large, the centrifugal force can also
allow to counter wind force, the rotor keeping its shape more or less."
Yes, centrifugal force can act like compression members to counter wind
forces. The Bird Windmill demonstrates that especially well. And the Sharp
VAWT spins faster, so the centrifugal forces are higher. I have found that
flimsy Sharp VAWTs can be made quite stiff by using centrifugal force.
The rotor can scale up, meaning that the centrifugal force stays high
because the mass of the blades increases by the cube as the VAWT becomes
larger. So centrifugal force can still be used for stiffening larger rotors.
The forces continue to balance as the rotor scales up.
PeterS
Group: AirborneWindEnergy Message: 22763 From: joe_f_90032 Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory


For me, much yet is to be made clear. The design of lines will make a difference; in real kited tether strings where tension is never perfectly constant there is much going on in the line that could receive more careful analysis. Lines not in a vacuum are ever interacting with other matter. The thermodynamics of a real line in a kite are not simple.  Here is a hint of the realm:

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

Group: AirborneWindEnergy Message: 22764 From: dave santos Date: 6/7/2017
Subject: Pilot-Kite-lofted-Power-Kite and Varidrogue Tests (TX AWE Encampment
In Austin yesterday, in good wind, saw the repeating cycle of miscellaneous AWE tests, in the patient quest to "test everything" as far as possible.

The pilot-kite (Kayakite) was, as usual, providing the flight automation basis, but in this case supporting a steerable power-kite (Prism 1.8). The effect is to fly up the power-kite window well above the surface, where the kite window becomes fully circular (less oblate), and the power-kite can no longer crash accidentally. This is a huge advantage for training human kite pilots, and for potential passive-dynamic energy harvesting. This is not a new idea, but the rigging details continue to be perfected. Popping the lofted power-kite from a pack is a promising launch method.

The varidrogue (Sedgewick's UFO kite skin; spars removed, SS bridling added) performed well, both in pumping like a jellyfish on-demand, and in sweeping iso-directionally in gusts. This was the second test of this WECS; the first last year in low wind, and better wind really perked up performance. Drogues are in fact aerospace workhorses, if not in constant oscillation as WECS. The varidrogue looks like a nice novelty WECS, perhaps suited to pump loads, effectively a pulsing jellyfish on a pole. It kills very nicely by holding apex lines while margin lines are slacked.

The entire spectrum of AWE WECS, from rigid-wing to power-kite to varidrogue, continue in play until fully evaluated for cost and tested for performance.

Open-AWE_IP-Cloud
Group: AirborneWindEnergy Message: 22765 From: dave santos Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory
Yes Pierre, Doug's years of statements regarding kite physics really are not clear to me, and he fails to address effective string theory at all. If avoiding Loyd is a virtue, Doug should have something better. You may recall how Doug weirdly insists that mass can be sustained in HTA flight without power (!)

If Doug and Peter have something important to teach about kites, effective string theory of kites is still not the best topic for them to offer help.  JoeF is right, there is far more to these topics than a dismissive view can see. Good luck to anyone serious about the physics.

On ‎Wednesday‎, ‎June‎ ‎07‎, ‎2017‎ ‎08‎:‎40‎:‎29‎ ‎AM‎ ‎CDT, joefaust333@gmail.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  


For me, much yet is to be made clear. The design of lines will make a difference; in real kited tether strings where tension is never perfectly constant there is much going on in the line that could receive more careful analysis. Lines not in a vacuum are ever interacting with other matter. The thermodynamics of a real line in a kite are not simple.  Here is a hint of the realm:

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

Group: AirborneWindEnergy Message: 22766 From: dave santos Date: 6/7/2017
Subject: Re: Sharp VAWT
PeterS wrote: "The rotor can scale up, meaning that the centrifugal force stays high
because the mass of the blades increases by the cube as the VAWT becomes
larger."

AWES engineering perspective: Unfortunately, cubic-mass scaling law sets a severe practical limit to how large such a rotor can be and still fly effectively. Excess mass is "toxic" to flight performance, and highest power-to-mass designs are favored.


On ‎Tuesday‎, ‎June‎ ‎06‎, ‎2017‎ ‎03‎:‎06‎:‎07‎ ‎PM‎ ‎CDT, 'Peter A. Sharp' sharpencil@sbcglobal.net [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

Hi PierreB,
Pierre said, "As the rotor is not too large, the centrifugal force can also
allow to counter wind force, the rotor keeping its shape more or less."
Yes, centrifugal force can act like compression members to counter wind
forces. The Bird Windmill demonstrates that especially well. And the Sharp
VAWT spins faster, so the centrifugal forces are higher. I have found that
flimsy Sharp VAWTs can be made quite stiff by using centrifugal force.
The rotor can scale up, meaning that the centrifugal force stays high
because the mass of the blades increases by the cube as the VAWT becomes
larger. So centrifugal force can still be used for stiffening larger rotors.
The forces continue to balance as the rotor scales up.
PeterS

Group: AirborneWindEnergy Message: 22767 From: dave santos Date: 6/7/2017
Subject: Point-mass quasi-particle assumption in AWE physics simulations
Lay-folk may deny or ridicule that particle physics applies to kites-as-quasiparticles, but AWE's academic players naturally apply the principles as needed. A common example is the adoption of a point-mass particle assumption in kite simulations, to ease calculation. No time is wasted arguing that a kite is not a quasiparticle, as its macroscopic bosonic character is explored.

In particular, I recall UweF discussing his point-mass kite assumption in a paper, but the Ampyx example below came up sooner in search. "Effective" physics theories are standard in advanced aerospace engineering, and open ontological questions are respectable and fascinating. In fact, advanced AWE kite physics may well help inform broad theoretic physics, as a special physical analogue case.

---- typical example -----

Ampyx- "...simulation using validated point-mass dynamics..."

A NEW WIND-POWER GENERATION METHOD
EMPLOYED WITH HIGH ALTITUDE WIND

Breukelman, Kruijff Fujii, & Maruyama


Group: AirborneWindEnergy Message: 22768 From: Pierre BENHAIEM Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

JoeF and DaveS are something rightly wrong or wrongly right about widening this topic until elasticity considerations comprising enthalpy and entropy. I do not know if there are suitable applications for kite energy, but I experimented this: as you sit down, your chair is compressed and becomes hot, and as you stand up your chair becomes cold. Please don't take the present post as a joke, not more than JoeF and DaveS' previous posts.

 

PierreB


Group: AirborneWindEnergy Message: 22769 From: joe_f_90032 Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

Or Wrightly-right in aims. Exploring! 


Introduction to Little String Theory by David Kutasov, Department of Physics, University of Chicago, Chicago, USA


Lectures given at the Spring School on Superstrings and Related Matters, Trieste, 2-10 April 2001


==============================================================

On long tethers in many real working kite systems, the atmosphere provides a ready heat sink. Also, the sun provides a ready source of radiation that will affect kite strings in various ways depending on the material and color and surface treatment of the strings; the affects will play with the atmospheric heat sink affair.


During time the strings of kite systems will be altered by the affects of tension cycles, resultant oscillations,  radiation interactions, and the interactions with the atmosphere. There well may be suitable works for the altered status of kite lines. We have already noticed signaling, illumination, conspicuity, entertainment, production of electricity for some of the fine alterations in lines.  Designing lines to meet particular works is an open creative space.   Lines may be shaped in many ways; lines may be broad or compactly circular in cross section, etc. Lines may be constructed to emphasize certain oscillations. Indeed, lines in a kite are wings open to unending choices for shape, texture, density, color, material, surface treatment, role in the kite system, and more.  Just where a useful model for so many aspects for strings might be found may be open. Explore.

Group: AirborneWindEnergy Message: 22770 From: joe_f_90032 Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

Correction:  "the affects will play with the atmospheric heat sink affair"  to

the effects will play with the atmospheric heat sink affair

Thanks.

==============================================================

Some:

http://www.superstringtheory.com/index.html

What is theoretical physics? /

/ Particles and relativity /

/ Why strings? /

/ What is string theory? /

/ How many are there?
How are string theories related? /

/ Is there a more fundamental theory?


==============================================================

Read with an AWE eye?



Group: AirborneWindEnergy Message: 22771 From: dave santos Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory
For anyone who mistakenly imagines string theory is limited to sub-atomic scales, and that the core concepts are not broadly applicable at any scale, this article helps catch up. In fact, for over two decades now, strings are theorized to span the cosmos at intergalactic scale-


As the basic process is grasped, of how physics theories are routinely extended as "effective theories", the idea of productively mapping string theory to kite string and membrane cases is not so wild. The AWES Metamaterial paradigm naturally emerged from fertile applicable physics concepts. Our AWE engineering imagination would be severely diminished without such models to build on.

Once again-

On ‎Wednesday‎, ‎June‎ ‎07‎, ‎2017‎ ‎05‎:‎16‎:‎39‎ ‎PM‎ ‎CDT, joefaust333@gmail.com [AirborneWindEnergy] <AirborneWindEnergy@yahoogroups.com  

Correction:  "the affects will play with the atmospheric heat sink affair"  to

the effects will play with the atmospheric heat sink affair

Thanks.

==============================================================

Some:

http://www.superstringtheory.com/index.html

What is theoretical physics? /

/ Particles and relativity /

/ Why strings? /

/ What is string theory? /

/ How many are there?
How are string theories related? /

/ Is there a more fundamental theory?


==============================================================

Read with an AWE eye?



Group: AirborneWindEnergy Message: 22772 From: benhaiemp Date: 6/7/2017
Subject: Re: Kite String and Effective String Theory

Page 167: "Whenever this limit gives to an interacting theory, it corresponds to a local quantum field theory (QFT)...".

Great! This paper looks to illustrate both Quantum and String theories. But this paper has nothing to do with kites: there is no reference about any scientific publication about kite systems.

It is easy to produce a lot of scientific papers with words like quantum and string.

So we agree that this sort of reference is quite irrelevant, drowning out DougS' fine arguments.


PierreB