Attachments :

fly_gen.jpg

What is the point of the lifter kite? Can the looping kite not also provide lift?

Hi Lou,   The Lifter Kite provides "passive control", the autonomous flight function, without avionics. Without the lifter the unstable sport kite would quickly crash. That's why these demos are so easy & cheap compared to "active control" (or helium aerostat) based AWE. You'll find a lot of related discussion in earlier posts & linked off JoeF's site.   The largest kite in history, the biggest wing ever, was Osborne's parafoil "lifter" flown near Ilwaco here (Long Beach, Washington), just over 17,000 sq. ft., so the scaling potential of this approach is vast. (Such a lifter could easily loft a hot 5000 sq. ft. looping parafoil as its multi-megawatt power element.)   Sadly, Osborne's Monster killed Edeiken on its maiden flight, but many lessons were learned. The fact that a community college sewing teacher could create such a wing is significant. Osborne also set the "official" kite endurance record (180 hours) on this same beach. Stormy Weathers topped 12,000 ft. altitude here with his sparred sled, a lifter (lifting line). Many of KiteLab's AWE experiments take place on this hallowed spot. The World Kite Museum is also located here. The winds are great year around.   Kite show lifters carry large exotic "line laundry" aloft & lifting AWE elements is a natural application. The greatest professional practitioners of giant show lifters are Peter Lynn & David Gomberg, with much online info available. KiteShip's (Culp & Jordan) huge OL traction kites can be stabilized as super lifters (KiteLab has stabilized an OL). Jordan's large parafoil lifters are some of the best ever.   Its been an honor to meet & learn from these pioneers, who have considerably advanced & perfected the art of giant kites. Its funny how certain "kite gods" forget the festival ancestors & fall for UAV aerospace to develop AWE.   daveS

Dear Dave,

Hi Dave & Chris,
 
 
Your discussion provides insight into the wisdom behind the LadderMill . . . how to support the weight of large (and heavy) cables needed to access the powerful winds at higher elevations. At lower elevations, the LadderMill leading airfoils merely support the weight of the cable below them while the airfoils at higher altitudes generate the power.
 
 
Harry
 

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To: AirborneWindEnergy@yahoogroups.com
From: christopher.m.carlin@btinternet.com
Date: Sun, 5 Jul 2009 18:47:09 +0100
Subject: Re: [AirborneWindEnergy] Re: Tripod Tether COTS AWE Demo

---

Windows Live helps you keep up with all your friends, in one place.

Hi Chris (& Harry),   Excuse the long post, but the issues are fascinating & complex.   (You must mean 5000 sq meters or 50,000 sq ft, not 50,000 sq meters, for a large tall ship sail area. JoeF might edit the typo out of the list archive)   A key point is that a displacement vessel is hull-speed limited & not able to accelerate like a kite & sweep a vast area in apparent wind many times true wind. So your correct estimate of about 5 megawatts for the ship is much less than the potential of a kite of similar area. The 5000 sq ft sweeping wing under a 17,000 sq ft lifter mentioned could in principle be sweeping a quarter mile loop at around 300 kts & roughly match or exceed the power of the tall ship's greater sail area in the same true wind. Existing parafoils like the 80's Flexifoil can do 100+ kts.   Yes, actuation force required to stabilize a kite increases with wind speed/load. The simplest way to input this force is to pull strings from the ground, not fly servos. A beauty of passive-control is that it is self-powered. In rising wind the kite gets increased actuation force for key stability mechanisms. Holland identified "snowplow stability" where a side gust kicks a leading edge back & the kite yaws (kiter's "roll") to meet the new wind direction. Weathercocking assisted by a tail does the same correction but with useful dampening & added drag. These mechanisms scale reasonably.    Unfortunately the pendulum stability of a CG aft of the bridle-point/tether-axis does not increase in higher winds & the kite becomes more prone to flat spin (kiter's "roll" or "loop"). Adding tail adds aft mass & water ballast might be taken on, but only to  the point the added mass becomes a greater liability. Active onboard actuation does not scale well, weight penalizing the kite critically in normal wind, but a "quiver" of actuation packages to match conditions might serve.   You are so right that flying clouds of "sail" in the sky will be a challenge, but what a glorious job it will be, a New Golden Age. The problem will be broken down into managable pieces (~100 sq m units?), just as a tall ship rig is a thicket of stability & control features allowing the "ants" to cope. A useful analogy is how crystaline solar cells cannot be made large & must be ganged. Another is to remember how discrete transistors gave way to integrated circuits. Kite elements can be interlinked in arrays for enhanced stability & even achieve general synchrony, effects already seen in festival kite trains & arches.   Harry, you make a good point about kite trains & how multiple elements can support each other. This will make a good topic to discuss further.     NOTES-  1) A kite with sufficient ground clearance can loop periodically without anything bad happening. There is a small loss of altitude to make up, which a lifter module handles well for a looper module. 2) A deeply keeled kite can lock into a dive by random initial conditions. 3) Weak active actuation can interfere with the harmonic process of repeated undesirable looping (chaotic control). Similarly, a small trim input can poise a lifter kite against the handedness of prevailing wind helicity. 4) Wind chaos near a kite's limits creates momentary crisises to deal with. "Punch turning", as used by stunt fliers, is the sudden release of "stored" tension on one side of the kite (punching motion) to shift CP. This does not require high real-time force, but the tension has to be replenished, perhaps by the same tiny servo-winch that provides trim input.      Re: Edeiken Tragedy   Your interest in failure cases is ultimately very valuable. In computer science such analysis is processed as case-based reasoning (CBR) as inspired by best legal & medical practice. It is a worthy compliment to Alister's connectionist genetic algorithm (GA) approach to solve poorly defined problems. but is opaque compared to CBR's transparency. CBR over GA would be so cool.   Poor Edeiken was swept up by the bridle lines as The Monster launched unexpectedly with what was described as the "roar of a 747". Several lines had parted due to poor attachment & one of these coiled like a snake around an ankle. When it released him he was about 100 feet high. Kay Buesing, director of the World Kite Museum witnessed the fatality & described it to me just last week.      The 25th anniversary of the tragedy just passed & the AKA magazine devoted a section to it which i clipped. Its yours for you file when we next meet.   The PTSD continues to traumatize fun kiting & the AKA's highest prize is the Edeiken Award. Peter Lynn describes being tripped by sweeping lines on launch in his excellent big=kite safety piece on Gomberg's site. Another common big kite accident is like ballooning where tag line handlers don't let go & are lofted.   The Monster only came down when it parted its 3 inch Kevlar cable. Aft bridles should be elastic & passively dump excess tether force by reducing AoA, allowing lighter lines. Traditional kiting changes tethers with wind changes. at the drop of a hat I was astounded watching Jim Patton promptly reverse the completed hour-long launch process of his 1000 ft classic train simply to substitute lighter line in anticipation of changed conditions. As with sailing one must fly the hell out kites to  fully maximize performance.   Some Lessons- 1) Stay out of the lateral scope of the launch/flight & never stand or walk inside the bridle/control lines of a big kite, 2) Kite Killers required for high consequence operation, 3) No loose lines or seams allowed, 4) Controlled launch mechanism required. 5) Hook knife required for all handlers & maybe a clip on carabiner/body tether if one is somehow dragged aloft.   The Controlled Launch requirement can be met by various means. A kite can be stoppered like a spinnaker or packed like a parachute, lofted, & popped at altitude. Towing or winching a kite aloft is a powerful technique. Stands with releases might be practical, etc.. Foxholes &/or trenches may be useful on mega-kite field. Large kite handling robots might be a solution.   Current giant kites are still belly launched & tend to flip over as one side gets more lift, a severe scaling limitation restricting handler ants to the current 10,000 sq ft.  A giant parafoil or sled might best be launched flaked & laid on its side so it can be constrained from the key nose point with launch crew ideally always outside the scope. Such a prepared kite inflates progressively by unfanfolding, stands up, & lift off; a pretty sight. This is how sleds self relaunch after landing on a side. This launch method avoids launching directly into the power zone. Note also that an overly short-lined kite tends to oscillate violently as the line's natural frequency matches/couples with the kite's natural frequency, a hazard of short-line launch.     ds

"might edit the typo out of the list archive"

Posted messages cannot be edited. A workaround when wanted: An author may delete their own post and posted an edited version again on a thread. Or the author may ask me to delete a post entirely with or without a new edited version.

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JoeF

PS: Differently, any page in http://EnergyKiteSystems.net may be edited; please send corrections, additions, deletion reequests to me for that space. Thanks.

Dear Dave,

Chris,   The loads are fantastic but manageable, as they are purely tensile. Currently Spectra is the preferred load path fiber across ripstop polyester or nonprepreg carbon ribbon sandwiched in a polyester membrane is also good. Graphene (bucky tubes) is in the pipeline & will give another order of magnitude to play with.   Wingloading by unit area remains constant across scale, so the same fabric is used in mega kites as small ones, but a progressive loadpath network must gather the mega stress to the bridle/flight lines. 50,000 sq ft flies on paper, but looks like an operational "kitemare"   Reinforced loadpaths can run fully within the single skin of KiteShip's OL to its minimalist 3 line bridle. It has been scaled to 5000 sq ft.. To scale up giant parafoils proliferate bridle lines as needed all along the span. "Sticky" kite designs are limited to about 100ft dimensions using airbeams. Carbon or bamboo spars only work to 30 ft or so before becoming too weak or heavy. Giant kites must be soft.   Spectra & Kevlar mooring & towing lines exist for shipping at least 8 in across & have been hyped as able to carry the power of a nuke plant, but by my calcs only if moving at high speed. One could spin/weave these together into ever greater diameters.   A key insight is that the ground itself is "free" kite structure to spread out & hold kites in shape or place ("staking out"). Since it doesn't fly it adds no weight aloft. Lift & drag provide spreading function in the remaining dimensions.   For a Lifter/Looper combo each kite lives in its own load & performance regime. A 5000 sq ft hot parafoil for the looping element seems to limit the whole system at present. The Membrane Wing Mill with airbeam battens might expand this scale constraint by perhaps 2X.   ds

I just received a news item that T. Boone Pickens is scaling back his (tower-based) wind power venture in Texas. Instead of a mega-wind farm, he's opting for several smaller wind farms. Perhaps one of the airborne wind power proponents could let Mr Pickens know of the advantages of airborne wind power and towerless wind power.
 
 
Harry 

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Internet Explorer 8 makes surfing easier. Get it now!

Welcome Ugo Bardi.
http://www.energykitesystems.net/KITESA/FAQelectric/researchers.html#UgoBardi

http://tinyurl.com/UgoBardi

The favorable response of his July 6, 2009, post
along with the responses' content's points for discussing
are energizing AWE. Ugo, welcome. And thanks for your
works and investing.

High altitude wind power: an era of abundance?
Posted by Ugo Bardi on July 6, 2009 - 7:06am in The Oil Drum: Europe
Topic: Alternative energy.
See:
http://europe.theoildrum.com/node/5538

http://www.energykitesystems.net/notices/membersent.html
Several members introduced Ugo Bardi to me. Thanks to DaveS and Wolf.

Ugo Bardi is founder and president of Association for the Study of Peak Oil (ASPO Italia)
http://www.aspoitalia.it/

Benvenuto,

JoeF

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Lift to all,
JoeF

Hi, I am a new member and am trying to get my head around some of the figures
implicit in high or medium altitude wind

Instead of the Kitegen set-up, I looked at the SkySail, which is, if not fully
operational, at least well into prototype sea trials.
Of course the technologies are not identical, as it is being used by them to
drag a ship along, but it is certainly analogous.
They provide fair documentation of what they are up to, but being no engineer
the exact calculations are beyond me.
Perhaps someone would be interested in taking a look and coming up with some
figures?
We are told here that it takes around 500square metres of kite to generate 5MW:
http://www.livescience.com/environment/ ... s-big.html

On the SkySails site they prefer to talk in terms of effective load, and say
that their base system, of 160square metres, generates an effective load of 8
tonnes, which they say equates to around 600-1000kw of main engine force
depending on tractive conditions and resistance.
http://www.skysails.info/fileadmin/user ... profit.pdf
The largest they are current in the process of building is 600 sq metres.

They aim, we are told, in the present series of product development to go up to
130 tons of effective tractive load.

Am I right in figuring that this might be a kite of around 15MW power?
And as a pure guess, would the area of the kite be around 2500 square metres?

I don't really see why the swept area would be much larger than the smaller
system, but perhaps the whole relationship in what they are doing with swept
area and the physical area of the kite is very different to this naive
extrapolation.

In any case, I am pretty confident that SkySails are well aware of the strengths
of the materials they are using, although of course the costs may escalate more
than they hope.
Presumably using such a system for energy generation rather than traction could
also alter the rate at which the line needed to spool, so the materials
constraints might be rather different.

I would be grateful if anyone could shed any light on this whole system.

I found it argues here that parasitic loss would be very important indeed,
greatly reducing available power:
http://windlift.wordpress.com/2007/06/2 ... er-output/
So apparently for towing you have no parasitic phase.
He reckons you get around 1/5th the energy that you would for towing.
That means that to get a 3MW power kite you need to go to the same level as you
would get at the end of the Skysail development program, and on those figures
and assumptions you end up the same as an offshore wind turbine.
Capacity factors would still be higher though, and you could possibly avoid the
heavy infrastructure and stick to a buoy.


http://www.livescience.com/environment/ ... s-big.html
'"One of the major problems for offshore wind parks today is the needed time of
excellent weather to install the units," Hoffschmidt said. Kites, on the other
hand, could be installed on anchored buoys, "which can easily be installed and
de-installed with a lower environment impact."


Since I am based in the UK I am particularly interested in systems which could
be moored on buoys, as this would be a lot cheaper than building conventional
wind turbines off-shore, and would take advantage of the high winds available at
around 300 metres at sea, comparable I understand to around 800 metres for most
areas on land.
This would overcome the severe space constraints in England and allow siting
much nearer to where it is needed.

My interest in the SkySails project in relation to wind is that many of the
control systems must be analogous, and they have done sea-trials for some time
with fairly large kites.
Of course generating power and providing traction are two very different things.

Welcome David.

I am still studying your welcomed post. Others will probably chime in on the calculations.

A first reply concerns your final sentence:

Such teases out one of my niche favorites:
Let traction work hydro turbines (for oceans, lakes, ponds, seas, bays) (or soil-friction wheel-driven turbines on land) Let huge kites tow a hydro-turbined-saturated barge; use the ambient solar and the hydro-turbined generated electricity to convert ambient water to obtain and compress hydrogen for delivery to need points. The barge could path freely or on constrained crosswind cable for constrained space use. The barge of turbines might be an at-sea vacation ship that just enjoys being out at sea.

Consider various secondary uses of skyhook lifter kytoons

 besides a main use of giving a tensional tower in the sky for holding AWE systems. 

 Tensional towers will be a disruptive technology for renewable sustainable energy production; having secondary and tertiary uses of the skyhook ...the ever-up platform... will enhance the scene.   Watch out,  Sir Hard-Towered-Turbine Industry, for there is a new player in town: tensional towers for AWE ...with secondary uses.

1.   Communications antenna.  Relay station.   $$$  Part of a constellation ...ringing earth.

2.   Observation deck. Have admission $  involved.

3.   Entertainment platform. Parties. Weddings.  Fee-based. $$

4.   Rangers' perma-home.     Even have an indoor swimming pool. Capture atmospheric water.

5.   Home sweet home for some people.

6.   Launch pad for hang gliders of the framed sort and the unframed limp sort (paragliders).   $$$

7.   Telescope station.  Photography.   Fee-based. $$

8.   Manufacturing environment where the given cold, solar radiation,  clean air, and atmospheric pressure form a just-right situation.   Drop-fly-glide the products to destination points in rural or urban areas.

9.   Recreational ride. Ride up the Laddermill and fly down or ride the Laddermill down.

10.  Super bungee launch pad.   $$$      

11.  Above-cloud PV station for energy making also besides the main AWE situation.

12.  Vacation-days destination.   $$

13.   Solar-powered aircraft landing strip. Fly from one AWE lifter kytoon to the next AWE lifter kytoon.

14.   Super big swing adventure ride.   $$

14. . ..............................................[  All members are invited to this thread for posting  more secondary and tertiary uses ...  .   ]

 

 

There was a very valuable post over on the Oil drum by Massimo Ippolito of Kitegen on the projected efficiencies of the kite plus cable in his system.
I trust he will not object to my pasting it here:
'The data are you looking for, can be summarized in the aerodynamic efficency of the arieal part of the kiteGen, wing+cables.
Up to now we operated with 8-12 efficent systems and our foreseeable target is about 28.

This value mainly affect the minimun wind speed requirement needed to produce the full (130% of nominal) power of the KiteGen Stem.

based to the current design, an efficency of:
8 require a wind of 23,8m/s to reach the machine full power
here follow the list:

efficency / min wind speed m/s
8 / 23,8
12 / 13,3
16 / 9,7
20 / 8,0
24 / 7,1
28 / 6,5
32 / 6,2

with an efficency over 24 the KiteGen Stem supply about 8760 MWh/MW

Attachments :

Attached Image:   Chicago Times Herald, 16 August 1896.

Greetings to the subscribers of the AWE mailing list.

Joe Faust wrote to me with kind words, accepting my request to be
added to this mailing list: he also suggested to introduce myself.
I think I won't write so much because I'm here to read and learn.
I'm one of the founders of WOW
http://www.windoperationsworldwide.eu/en/who-we-are/

I added a link to AWE on our website and let me link here a page
http://www.windoperationsworldwide.eu/en/faq/
which contains long technical papers on KiteGen that are not so easy
to find on the net, perhaps (I mean the works of Fagiano and Maneia).

Thank you and have a nice day.

--
Carlo Perassi - http://perassi.org/

Hi Dave,
I was just wondering if you could illustrate the working principle behind the TTCA (Tripod Tether COTS AWE) further so to replicate the experiment at home.
..It looks like lines are hoocked somewhere on the ground in a circle pattern around the generator ..
Hope you are not on vacation yet (so selfish).

Gabe

Hi Gabe,   The legs of the string tripod in the video run to an equilateral (~30ft/9m) triangle of three sand anchors with a "corner block" pulley each. The strings run from there to a center crank & drive it by a three phase sequence of tension-slack with no "dead zone".   The tripod is much more robust to line maladjustment than i first thought, requiring only crude slacking of a "sheet" line from pulley to a windward anchor to tilt the tripod downwind as the wind rounds. Simple variations are under study to automate this adjustment for true "fly & forget" & you may hit on a good solution.   One minor problem with the looping kite scheme is that the swivels may need a tiny line spreader to operate freely (see JoeF's AWE DIY page coming soon). Sand is a problem for me & i am currently using a  fisherman's six step swivel for the least resistance. Oiling & over-specifying fishing swivels is smart as they overheat in air.   An improvement may be to have three sheets, from the crank workcell to the anchors, which can place the mobile workcell wherever best adjusts the tripod tilt. Also consider merely turning a bike on its side & driving a pedal, as a drive train. A generator can be driven off the rear wheel at high speed.   Please get back to JoeF or the list with your progress.   dave   PS stay tuned for an even simpler "passive eights" COTS demo

Please resend the attachment video link.  Thanks

---

To: AirborneWindEnergy@yahoogroups.com
From: gb2910@gmail.com
Date: Fri, 31 Jul 2009 09:32:10 +0000
Subject: [AirborneWindEnergy] Re: Tripod Tether COTS AWE Demo

 

Hi Dave,
thank you very much for being so exhaustive and patient with this 'wind power guide for dummies' thing  :)
I sketched up a kite(s) / generator set as I evinced from video and description you provided :

http://sites.google.com/site/closedsteam/Home/TTCA.jpg


Can you spot any anomaly ?

Questions:

1. How many lines do control the kite (3)?
2. How do you prevent kite lines from getting tangled while kite keeps rotating around Z axis ?
3. (Deriving from my kite dynamics ignorance) Is the 'cheap X-kite sport-kite' allways facing the right direction  without external intervention ,not being influenced by wind changes ?

I keep my ears open for:

•  'even simpler "passive eights" COTS demo'
•  JoeF's AWE DIY page coming soon..

and I surely will keep you updated with eventual progresses .

x Darin You can check the video here:

video:
http://d.yimg.com/kq/groups/24857016/1398141728/name/tripodtether.mpg

message:
http://tech.groups.yahoo.com/group/AirborneWindEnergy/message/166

Gabriele,   The drawing is close, but there are key details to refine-

--- In AirborneWindEnergy@yahoogroups.com, Gabriele <gb2910@... Gabriele and All:
The folder and offerings for the new DIY AWE are modest yet.
All are invited to generate notes, images, and detail plans
for AWE experiments that have some successes involved.

http://www.EnergyKiteSystems.net/DIY/\

Lift,
JoeF

Hi Dave,
I re-uploaded an updated version of the sketch :
http://sites.google.com/site/closedsteam/Home/TTCA.jpg
..did I get it right this time ?

(If positive should the sketch image be posted to JoeF's AWE DIY page ?)

Hi Gabriele,   Wow, your sketch is very beautiful & clear. JoeF will surely feature the illustration & any others you do. Maybe KiteLab can help you somehow, like a small stipend. Your drafts are, of course, already online in this message thread. A comparative set of concept sketches would be, well, AWEsome.   There are key small details you may want to add-

Hi Dave,
as we manage updating the sketch of your kite power-set I would like to thank you for your appreciation.
I won't ask any money for having fun :)
I would be more than happy to illustrate other stuff if needed , just ask.

updated illustration:
http://sites.google.com/site/closedsteam/Home/TTCA.jpg

Gabriele and Dave,
 
 
I commend you both on your innovative thinking in regard to the single-kite and tripod system to drive a crankshaft. While there is merit to using sprags (one-way clutches), the crank system will ultimately involve less complication and require less maintenance over the long-term.
 
 
The tripod and crank system will have application on a larger scale in many parts of th world. Gabriele's illustration shows a desert setting . . . and there is wind galore over many of the deserts (and offshore islands) around the world. Lets hope that this idea gets developed on a larger scale.
 
 
Quite often its not the massive amounts of money given to the politically-favored that produces worthwhile results. There are many examples of some one's hobby that was undertaken on a shoe-string budget that ultimately evolved into somethng that served the needs of a large population.
 
 
Regards,
 
Harry 
 

 

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To: AirborneWindEnergy@yahoogroups.com
From: gb2910@gmail.com
Date: Mon, 3 Aug 2009 12:16:53 +0200
Subject: Re: [AirborneWindEnergy] Re: Tripod Tether COTS AWE Demo

 

Hi Gabriele, do you do illustrations, for hire and if so how much and do you have a resume. I have some designs that need touching up. spacecannon
---- Gabriele <gb2910@gmail.com

The crank may drive through a planetary gearbox to increase rotational speed on a flywheel that would maintain momentum. Another method is to actually build a small scale model of the tripod and develop ways to keep the crank continually rotating using cyclic-tension inputs only. In actually practice a compound winch mechanism would translate large movements of the kite into the required stroke of the crankshaft.
 
 
Harry
 

---

To: AirborneWindEnergy@yahoogroups.com
CC: gb2910@gmail.com
From: SeattleDL@comcast.net
Date: Mon, 3 Aug 2009 10:35:25 -0700
Subject: Re: [AirborneWindEnergy] Re: Tripod Tether COTS AWE Demo

 

Attachments :

kitehel2.jpg
helkite3.jpg

The single center generator scales poorly, but the tri-tether itself scales well. To scale into upper winds a tri-tether merely needs more distance between legs. The triangle base can be quite small the lower stretch the tethers are, the thinner (less wind catenary), the lighter (less grav catenary), & the better tuned the tri-tether. To get to the stratosphere an anchor triangle of six miles to a side, with a reel-generator at each anchor, will not suffer too much "wash-out". Other measures will work too, a net geometry can be suspended aloft by various means for as tensioners, spreaders, or a "leg up" for tri-tethers.   Yes, helium can serve the pilot lifter function nicely, but at a considerable cost. I've done small helium UAVs since the eighties, & find Helium problematic. A compromise is to use a tiny helium pilot to launch a lifter that then launches the looper. In 2007 i used single party balloons with a "skyhook" kite wing & soft delta to initiate staged relaunches with fine results. [see attached jpgs]   If we are talking grid scale AWE at truly high altitudes, the best solution for calm may be to tow the kites in a circle by the tri-tether, perhaps at a lower altitude. As for competing with conventional wind turbines at low altitude, its plausible that low capital cost AWE can dominate where financing is scarce & labor is cheap, or "instant" or mobile wind energy is desired.

An anchor triangle of 6-miles per side is possible on some offshore islands and in remote windswept regions. There are some 1600 offshore islands on the eastern side of Hudson Bay and James Bay, just to the west of Quebec . . . and within range of the James Bay hydroelectric installations (transmission lines along Quebec's west coast along Hudson Bay and James Bay). There are powerful winter winds that blow over the eastern side of both bays.
 
Perhaps we have a suitable North America geographic location for a large-scale tri-tether power kite wind conversion technology. Power Authority of New York has initiated discussions with Canadian authorities on increasing pumped hydraulic capacity that will involve a new international hydroelectric installation . . . which would certainly be compatible with high-altitude wind power.
 
 
Harry
 

---

To: AirborneWindEnergy@yahoogroups.com
From: santos137@yahoo.com
Date: Mon, 3 Aug 2009 22:37:43 -0700
Subject: RE: [AirborneWindEnergy] Re: Tripod Tether COTS AWE Demo [3 Attachments]

 

Sounds a bit greedy to me!
On-shore you get very decent winds at around 800 metres, offshore at
around 300 metres.
For the UK, a few moored buoys should provide a base for the tripod, and
get a fair amount of wind without pushing the technology.
Helium is a very scarce resource, which escapes the atmosphere and
leaves the earth forever.
It is useful or essential for a lot of uses such as in medicine and much
sophisticated equipment.
It would seem foolish to me to use it to float balloons.
Hydrogen would do fine - it's explosivity is much exaggerated.

--- In AirborneWindEnergy@yahoogroups.com, harry valentine <harrycv@... wrote:
islands and in remote windswept regions. There are some 1600 offshore
islands on the eastern side of Hudson Bay and James Bay, just to the
west of Quebec . . . and within range of the James Bay hydroelectric
installations (transmission lines along Quebec's west coast along Hudson
Bay and James Bay). There are powerful winter winds that blow over the
eastern side of both bays.
large-scale tri-tether power kite wind conversion technology. Power
Authority of New York has initiated discussions with Canadian
authorities on increasing pumped hydraulic capacity that will involve a
new international hydroelectric installation . . . which would certainly
be compatible with high-altitude wind power.
Attachments]
scales well. To scale into upper winds a tri-tether merely needs more
distance between legs. The triangle base can be quite small the lower
stretch the tethers are, the thinner (less wind catenary), the lighter
(less grav catenary), & the better tuned the tri-tether. To get to the
stratosphere an anchor triangle of six miles to a side, with a
reel-generator at each anchor, will not suffer too much "wash-out".
Other measures will work too, a net geometry can be suspended aloft by
various means for as tensioners, spreaders, or a "leg up" for
tri-tethers.
considerable cost. I've done small helium UAVs since the eighties, &
find Helium problematic. A compromise is to use a tiny helium pilot to
launch a lifter that then launches the looper. In 2007 i used single
party balloons with a "skyhook" kite wing & soft delta to initiate
staged relaunches with fine results. [see attached jpgs]
solution for calm may be to tow the kites in a circle by the tri-tether,
perhaps at a lower altitude. As for competing with conventional wind
turbines at low altitude, its plausible that low capital cost AWE can
dominate where financing is scarce & labor is cheap, or "instant" or
mobile wind energy is desired.
speed on a flywheel that would maintain momentum. Another method is to
actually build a small scale model of the tripod and develop ways to
keep the crank continually rotating using cyclic-tension inputs only. In
actually practice a compound winch mechanism would translate large
movements of the kite into the required stroke of the crankshaft.
length), it appears that at some altitude, the required "geometrical
underpinnings" may "wash out", ie. as the lines get longer,
differential tensions tend to disappear (for a given oscillation
amplitude), and the loaded generator crank may stall as it resists
rotation. This is of course because the effective "end-to-end line
stiffness" goes down with length, and the subtended oscillation angles
(viewed from the ground) of the oscillating kite becomes smaller which
washes out geometrically induced strain differential (assuming that the
kite's oscillation amplitude is not increased with altitude).
power generation? 2. What is the relationship between oscillation
amplitude and altitude (ie. effect of ground constraint on the
oscillation) ?
successfully take on the conventional turbine industry, AWE power
schemes will have operate at least out of the boundary layer in which
the turbines live....I would thing 500 feet and above
balloon....voila, the no-wind situation is solved :-)!
to thank you for your appreciation.
ask.
it simple.

It is not necessary to go directly from a 5 watt system to gigawatt
system. It should be a simple matter to build a 100-1000 watt
(continuous, average power output) test model, and determine many of
these answers. A cooperative effort (Dave S. does the hands-on work;
from materials and cash raised/donated by the group; technology
belongs to all, for instance) might be indicated.

Dave

   I too have a biz to run and have been too busy to be involved lately but what DaveL brings up is a very important issue. One thing that would really help the research here is a good set of data acquisition tools. Accelerometers and load cells and wind speed sensors with data logger mounted on kites
and several locations on the lines so all of these forces may recorded in synch. Wireless com to a ground based controller could provide enough data to use those forces to our advantage.

   If the funding were to become available I may be able to convince my  brother to take a look at the technology. His company Signalysis does vibration monitoring and both destructive and non-destructive  QC testing and one of their software products is called ResTrak. ResTrak looks for resonant frequencies in objects as they are being vibrated and adjusts the shaker frequencies to force a fatigue failure. If we were to develop a good system of kite and line testing procedures I think we could come up with a way to use all of those drawbacks of long lines as an advantage. A feedback control system that tunes the kite's motion to the resonant frequency of the lines in real time could actually enhance the desired forces. 

  I know this would be an expensive and time consuming project to undertake (I still have yet to find the time to build out my universal energy harvester I started last year) but it would go a long way in helping sell the idea to the rest of the engineering community. My limited experience with designing test fixture for the company tells me the cost of such a data acquisition system would run about $30,000 to $50,000 to have them do it. In the past I have suggested that they look into it but their main customers(GM) kept them really busy. As we all know GM subcontractors have a lot of free time on their hands these days and since Signalysis's latest jobs have been validating wind turbine blades they may be more likely to take a look at the project, (although the tower/turbine people my want to squash any competing tech) .

   Anyway, at some point there will need to be some really good detailed testing to make this tech competitive and we need to figure that into any future funding request.

Just  a thought.....

-brooks

So kind of you,I am not taking credit for Dave's creation though ..
I think it is a very functional set that could evolve to a practical
application, exspecially in less developed countries.

My pleasure ..

I am not into illustrations (average programmer resume) ..
'I have some designs that need touching up' -- You can maybe avoid human intervention by using:
- a cheap pc and
- a simple neural net based computer vision system
- that learns from humans
- how to perform kite flight maintenance.

Gabe

Dear Dave,

Nice discussion. I would suggest the winner in the whole thing will be
the one who takes a KISS approach.

Regards,

Chris

That will depend upon what the last "S" in KISS stands for.

---

To: AirborneWindEnergy@yahoogroups.com
From: christopher.m.carlin@btinternet.com
Date: Wed, 19 Aug 2009 17:41:59 +0100
Subject: Re: [AirborneWindEnergy] Kite Vibes- AWE Flight Dynamics

 

What is needed is more comparative evaluation of the most promising AWE schemes rather than one-off studies. DaveC's suggestion of group sponsored validation of the looper under a lifter tugging on a tri-tether is welcome, but it would be even better to micro-fund all the talented experimenters on this list. Some independent study of the AWE options could begin this fall by University of Texas Aerospace students, on a shoestring budget, as suggested last winter.   Empirical study is great at the human scale, but nothing scales better than good speculative calculation in advance of upsizing. DaveL is probably the worlds leading tether dynamicist. His tethered physics program would be a great foundation to build on. Brooks'  brother (& dad) would be excellent researchers of kite harmonic physics, they are a vibration science dynasty. The dad, who taught me a lot back-in-the-day, worked on Space Shuttle vibration modeling & the son founded a business doing such analysis. (Yo Brooks, if they can start to just look at the AWE problems now there seems to be opportunity for all who get prepared.) Jeroen Breukels with the Delft group is also a gifted numerical AWE dynamicist. What a team all four might make.   Many helped get to the better understanding of the AWE problem. It was Dave Culp who told me about the the looping kite idea in '07, which seemingly originates with Payne & McCutchen in '76. Loyd's '78 filing does not add much new, yet he did see that a tri-tether  from a crankshaft aloft can drive a crankshaft below by three phase sequential tugging. His solution had several shortcomings in detail- complex triple-crank shaft, twisting/chafing issues, etc..These are solved in the latest tripod/swivel geometry.   Looping tethered foils were reviewed in "03 by Pete Lynn, but but he was skeptical of power transfer by simple mechanical means to a ground generator. Payne & MacC's scheme of directly driving a crank by a single line suffered from the washout factor Dave Lang mentioned. P & C also considered a kite flying crosswind along a long pulley loop, which had little washout.   Peter Lynn & David Gomberg in the 90s revived the Victorian pilot kite (pioneered by Eddy (Blue Hill), Baden-Powell, & Cody) for stabilizing modern giant inflated theme kites.   The latest scheme combines the best of various approaches & adds a spread 2D (triangular) footprint to operate in any wind direction by minimal means. The advance is intuitive & qualitative & does not require very deep analysis to see the power of it.

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Hi all,
it doesn't seem to have been mentioned here that I remember but 'Nature' had a 3 page report on high altitude wind energy a couple of weeks ago.

For those who have a subscription the article is here:
http://www.nature.com/news/2009/090729/full/460564a.html

I don't really want to put the article online as I don't want to risk the University's subscription (it's unbelievably expensive). But I'll send the pdf to people who are interested, just email me.

Actually, considering it is one of the two premier journals, there's nothing new or particularly insightful in there. Makani feature prominantly as expected (their 30m carbon fibre wing weighs a tonne!), as do skywindpower, also Joby Energy?
There is the typical failure to differentiate between ground level generation of power and generating the power at high altitude and wiring it down- so no real critical analysis of different ways of making the technology work. Still, it's good to see it featured in such a high impact publication, even if the tone of the article is not exactly super enthusastic- it ends with the story of a prototype snapping in two in flight!.....

Well, there's a 28mph cross-shore breeze on. Time for a break from C coding I think!

Yes, please send me the .pdf article to: darin_selby@hotmail.com  Thanks!  ~Darin
 

---

To: AirborneWindEnergy@yahoogroups.com
From: adjf20@sussex.ac.uk
Date: Thu, 20 Aug 2009 16:01:51 +0000
Subject: [AirborneWindEnergy] Nature AWE article

 

please send a copy to me also.
---- Darin Selby <darin_selby@hotmail.com