Tutorial over AWES ?
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http://www.energykitesystems.net/Tutorials/index.html

Status at my desk: 

In support of the clarification to Joe by Robert: 

Joe,

it is unpractical to adopt a fixed ratio between the Vwind and Vreelout in groundgen concept.
Machine emergy evaluations impose a well designed operational force limit.
Emergy is mainly affected by the operational force and the dynamic behavior, instead the cost of the operational speed, is negligible.
Power=F*V then is better to focus the design on speed modulation.
Then the optimised mean reel-out speed in groundgen is Vwind - k.
k is pretty a constant function depending of the aerodynamic efficiency of airborne equipments and the chosen force limit, both assumed constants in a wide conditions range.
In this approach the machine dynamic is strongly stabilized providing further emergy advantage.
I've just read a doubtful comment about our (KiteGen) "pretty glasshouse", this is a misunderstanding, the gasshouse is a  precise functional component, designed to cut the effects of residual dynamic excess of the equipment with the wind interaction .
The aim to always look for the extreme maximum power that could extracted by the wind typically named "optimization", it is a scientific papers common error, mainly due the young and unaware attitude of the students.  

in other words:
if the wing reach the full operational force at 5m/s of wind speed, a wind of 6m/s allows a reel-out of 1 m/s and a wind of 15 allows 10m/s.
Strategies to exploit very slow winds with lower force limits are planned optimization tests, but with an output that is small fraction of the nominal power and with a limited occurring frequency.
Massimo

I would like to add some possibilities and configurations.

A wiki might be the best format for these tutorials. Start a new thread and I will pick it up with you.

Robert,
I would like to see your spreadsheet. I am familiar with excel so I don't care about it being less than presentable.

I think I listed the ability to have different kites for different wind speeds as an advantage of groundgen. So no I don't think it is necessary.

I should have used the word cyclic power production rather than intermittent. You are correct that the intermittent nature of the output is trivial to eliminate.
The cyclic nature of the output means that if reel in time is 1/3 of total then 33% of the flying weight and thus the ROI are decreased by the same. Doug posted about it being 50% and that he thought that it was a show-stopper. But AWE can be as little as 10% the weight of a ground based turbine so I don't think that even 1/2 reel-in time is an insurmountable problem. This reminds me of how in a 4-cycle engine a cylinder is only producing power 1/4 of the time. They weigh more than 2-cycle or turbine engines but have no problem with "intermittent" power.

I was using the 1/3 wind speed reel out in my weight lifting loss estimate so a 15 mph wind. And yes the kite would be huge. But neither seemed to be important to the calculation so I left them out.

I think the conductivity of steel does preclude it as a flygen tether but I have not done the math on that. Your point however that the cost of the tether material can be significant enough to warrant a different choice is certainly true.

Brian

A flygen produces far less fatigue on it's tether. Maybe 1/1000 as much. But being that UHMWPE is more that 1000 better in fatigue your point still stands. But for aluminum vs copper I am not as sure. I would have to research that. Yes copper is much better at fatigue than aluminum but not orders of magnitude. It depends on the exact numbers of weight, tensile, temper, load on and on. That is a whole different thread.

My apologies for the 70% number. It was off the top of my head. But here's a shot at explaining my thinking. if the tether fails at 2% stretch and you have a factor 2 safety margin then it will stretch 1% of it's length between zero and max load. If you pull it only 2% of it's length in a cycle then the stretch takes up 50% of your motion. I threw in another 20% for the sag that comes and goes. I know that is a gross oversimplification and there are numerous things that can be done to mitigate this, but I think the point holds. I don't see short stroke groundgen as a practical competitor to coal.

Brian

On Fri, 2012-03-23 at 09:53 +0000, blturner3 wrote:
Good point. I think early reel in/out systems will have to live with
only 50% energy production time. However, as our budgets increase we can
build more aerodynamic kites and high speed reel-in systems and I think
90% production cycles should be possible. Before Dave S. argues with
this suggestion I will undertake to provide evidence for this prediction
when I get the time.

Look at birds. The bigger they are the harder they have to work to take
off. Aircraft are the same. I therefore think that arrays of numerous
kites is the way to go rather than trying to build really big ones.

Get the voltage high enough and even carbon fibre is OK as my
spreadsheet demonstrates. Generators can be wound to produce tens of kV
directly without the need for any airborne electrics.

Robert.

Hi,

My spreadsheet looking at the properties of possible kite tethers is
finally posted at
http://www.copcutt.me.uk/Tether.ods

It is in Open Office format. I can convert it to xls if need be.

It is not complete - let's make filling it out more an open source
project. One of the big time wasters has been getting ball-park costs of
the various materials. Obviously these vary depending upon cable size
and special deals made with suppliers so if anyone has any suggested
figures please let me know.

Robert.

Kite: Three sets of parts reacting in a flowing media: wing set, tether set, resistive set (perhaps another wing set.  Kite systems may be used to power the needs of civilization by smart use in water and air.

Thanks very much for compiling this.  I wish I could open any kind of spreadsheet file; they used to be so handy, but I havn't actually seen one work for years.  

The discussions about groundgen versus flygen seem to be blind to types of groundgen that do not involve cyclic reeling-in and reeling-out  (and thus not the drum wear on tethers; some even avoid drum-hold of tether altogether); and some of these are short-stroke and some long-stroke operations.  

It seems sensible to use a separate section for repeated reeling and unreeling.  Metal tape is 99% efficient as a belt drive, so it would be a good candidate.  It might be clipped to the tether at intermediate points in certain weather patterns.

I'm watching CNBC and they announce a helium shortage and the CEO of Airgas being interviewed.
So I check Google news and:
1) They are blaming the helium shortage" on party balloons
2) "Scientists" want party balloons banned immediately
3) There is a "problem" we never knew about:
a) Helium is suddenly a big "huffing" problem (According to the "HUFFINGton Post")
b) most huffing deaths suddenly involve helium - who knew?
c) all sorts of big-name acronym agencies are instantly onboard to suddenly "educate the children" about this "persistent", yet "brand-new", "problem" (can yew say "oxymoron"?)
d)stats are cited that something like 9 kids died from helium in Florida in just the last year (alligator-wrestling using helium?) Extrapolate to 50 states and the numbers rival auto-accident deaths! - Wow helium is suddenly one of the biggest dangers faced by kidkind! (no adults die from inhaling helium - they are too smart - adults get away with it, while children die in large numbers)
e) All news stories cite the "need to educate the children" about this "new" "problem"...
f) The news stories themselves did NOTHING to "educate" the reader about what, exactly, is so dangerous about inhaling helium, with no examples given, nor does any news story go into any detail of how anyone has supposedly died from inhaling helium. They only cite that helium contains no oxygen, and the term "embolism" is peripherally mentioned, as though using a "big word" proves the thesis.

Both articles I read made similar hysterical points:
"Do you realize a 4-year-old can buy one of these things and there's not even a warning on it?" - OK the other article said "5-year-old" (These articles are independently written by different authors, ya see...)

Wow yeah a warning label would have stopped that 4-year old- within a couple years, just so he has time to learn to read... And now what exactly happened to this illiterate 4-year-old upon grabbing the string of his own destruction?

Nothing whatsoever happened to this daring 4- or 5-year-old, I'm sure, but I digress - hey this is an emergency! This could be as serious of an emergency as "global warming"... Noooooo Mr. Bill!

Seems like the national whatever of drug abuse and the national whatever of inhalation and huffing problems have no details to offer US, they just want to educate "the children"...
(No doubt they need a lot of your tax money to do it)

What a bunch of press-release crap.
So tired of reading press-releases masquerading as science.
Seems like the former trumps the latter - why even bother with facts these days?

All I can say is, now that there is a confirmed helium shortage, Dave Santos warned us that I was the culprit with the couple of tanks I blew through at Oroville a couple years ago - I was a sinner - I was "bad". I was wasting helium. That was a waste - bringing a flying wind energy device to a flying wind energy device conference - of all the nerve! You don't see anyone else bringing a flying wind energy device do you Doug? Get a clue!

I feel somewhat relieved that the national news did not flag me as the culprit, instead erroneously believing that party balloons were to blame.

Anyway, the good news is, the shortage is temporary. For some reason the producers say there's no long-term problem coming up with the amount of helium demand every year, just some short-term bottleneck.

Whew, I am relieved that the problem that offered no explanation (helium shortage) complicated by another problem that offered no explanation (children dying in large numbers from helium) has been solved by a solution with no explanation (well there's a shortage today but it won't last so don't worry).

Gee I'm glad I spend the time to listen to "the news"... I'd hate to be uninformed!

Nobody drills for helium. It's a by-product of natural gas production, which is increasing in the U.S. nowadays. We've been exporting half of our helium. We could stop exporting if we really needed to.

Anyway I could not think of a better whacked out place to announce this whacked-out news, than here!
:)
Doug S.
Maboomba!

Drat
I was wrong then,
I tought we'd be treated to a short video of a spring return measuring tape with a wee dynamo plugged into the axle unwinding and winding....
I do like the idea Bob.

vague scientist eh sorry New Scientist ran a story on this a couple years ago.
http://www.newscientist.com/article/mg20727735.700-nobel-prizewinner-we-are-running-out-of-helium.html
luckily fibre optics are still being made, so we can keep sharing the story....

Ice caps are melting, so the land will rise, but with less helium underground.

Doug you've saved us all, thank you! How can we ever repay you?

Thanks!
reading now .

It's the same pitch they've had for a while though.

It'd be nice to see what fruits are coming from the single line control.

They need to string some daisys.

Gosh Rod, you're embarrassing me now - thanks I'm flattered.
How 'bout a Nobel Prize like Al Gore, for inventing the Algorithm?
Or like W. for inventing the www-dot internet?

I'm not sure if I'm on board with the idea that you have to say his name 3 times to get on the web "dubyuh, dubyah, dubyah, dot..." but I think that goes back to casting a magic spell out of ancient Egypt, kind of an "abra-cadabra" kind of thing...

Like saying the shortened version of Tutankh-amen at the end of a prayer to "open a door" - "amen"...

"dubyuh, dubyuh, dubyuh, dot I pray to thee that thou wilst open the door of the web unto mine eyes"

"dubyuh, dubyuh, dubyuh, dot" droned the zombie slaves as they stumbled forward, descending endlessly downward, deeeper and deeper into the mine, to painstakingly remove dilithium crystals from the cave walls - it could only be done by hand...

Hey is that helium I smell?

You can't smell helium.

That could be a problem.

yes, what about "the children"?

Where's dubyuh-dot when ya need him?

I propose we start a "National Center for Stuff that Will Never Work", and institute a 10-year program to never build anything.

Joe Faust shows another possibility in message 5186 that has been a little in discussion.As MW-scale should be offshore or in deserts or big farms (the tether marks a part of the radius of inhabited zone) minuses of maritime implementation (corrosion with salt...) of this scheme (crosswind "SwimGen"?) are not higher than for another scheme implemented offshore.And pluses are accumulated flygen and groundgen pluses without minuses.

But possible minuses could be repercussions of bustles on the maritime environment in regard to fauna and flora;possible mechanical losses due to the motion of hydroturbine in rapport to eight figures of the kite...

The message 5186 showing perhaps the most promising way,we should study more this scheme.

PierreB 

http://flygenkite.com (the configuration of flygenkite is adapted for "swimgen")

     

Yes, I would called this a towed launch. We did this with hang gliders back in the early '80s. They have improved it quite a bit since then. Model sailplanes do a similar thing with what they call a high-start. A rubber-band and string arrangement.

It has the disadvantage of taking room. Whenever I see a more complicated launch mechanism I compare it to towed launch and look for the reasons why. I think that they are usually trying to simplify for automated launch/landing which is somewhat understandable.

Brian

Excellent sheet. I found a price on aluminum here.
http://www.cable.alcan.com/NR/rdonlyres/EB55A5AC-4960-4C6A-842C-E70709E2E7FA/0/Service.pdf

I knew that generators could be made to whatever voltage you liked. But I thought that there was some upper limit in the few thousand volts range. I googled high voltage generators and found that ABB is making one that puts out 34kv! So yes at those voltages steel would work fine. There is a sweet spot where the tether can handle both the tension and the amperage. You have opened my eyes to a new line of thinking.

There is a price trade-off that hides in the details of all of this. I will work on your spreadsheet and see if I can tease it out in my thinking. If I modify the sheet I will send it back to you.

Thanks,
Brian

So I have been studying aluminum vs copper fatigue today and I have to throw my hands up. The yield strength varies by 8 fold for aluminum and 6 fold for copper based on tempers and alloys. The variations mean that either copper or aluminum could be stronger depending on exactly what alloy and temper your talking about. The conductivity is all over the place. The weight is the only fairly constant property. Aluminum fatigues constantly no matter how low the stress. It just gets weaker and weaker. I could not find the same data for copper. For steel I did find if the stress is less than about half the ultimate strength that it fatigues real slowly. Orders of magnitude slower than aluminum. I thought that all metals did this. I don't know if the same is true for copper, but I would take Dave S.s word for it at this point. I am thinking that only a professional metallurgist could pick what to compare with what. I caught myself playing a game of rock, paper, scissors. But it was copper, aluminum, steel.

Yes, UHMWPE AKA Spectra or Dyneema is the clear winner for non-conductive tether material. The aramids and other exotic fibers seem to only beat it by a bit in one category or another, usually at a much higher price. At least until carbon-nanotubes live up to their grand billing and also become affordable.

Clearly I need more study on tethers. If I catch some time I will try and figure a way to estimate out how big a pain a composite tether would be.

Yes, Winching not towing. I will go correct that post as well.

Brian

Today I'm eating humble pie. The correct term here is winching not towing. Dave S. pointed this out. It's been 30+ years and I was young at the time so I was a bit fuzzy. I called my dad and asked him "didn't we tow?" Yes, we did tow hang-gliders. But we also winched them.

Brian

Great input. I read the 1/3 wind speed rule in a previous post and thought that I really should go read Lloyd's paper. It seemed to me that number would be more fluid but I did not have the experience to say. You have helped explain that yes it is more fluid.

Sorry about the "Pretty glass house" comment. I just did not see the point of the expense of glass walls. The shape makes some sense to me. And the crane makes sense. Inflated concrete domes I think would be cheaper and similar in function. The glass does provide excellent situational awareness to any operators inside the dome but I would think it would all be fly by wire from a control console.

Brian

Steel is unusual in having a fatigue limit.  If your part is good for a million reversals of stress, it has an indefinite life.  Non-ferrous metals generally have no such limit, and continue to weaken.

I'd worry about getting any version of your machine up and running, assuming you have anything in mind capable of being built and run. The exact best tether material for production systems is the type of thing best worked out over time.
Or assign the task to the "Ministry of Stuff that Will Never Work" and let them include in their "10-year Program to Never Build Anything"...
:)

Hybrid winch/tow (or both at once) options: 

Images and video are yet to be launched.  

Two video links and recycled kite arch and other links are up flying now

Here is the press release.

http://www.altaerosenergies.com/AltaerosPressRelease032712.pdf

It has a picture but othwise reads like the artical.

Brian

Imagine if we were sitting over an ocean of fish, everyone talking about dropping a hook with a worm, maybe several hooks with worms, lures etc.
We all sit around talking about various hook ideas, line ideas, then there are people with nets, etc.
One group has all the money cuz they wanna fish deeper thsn the rest and at great expense they have pulled up a few of those ugly fish with lights and antennae from way down deep.
With nary a boat in the water, nary a worm on a hook, or a hook on a line, they endlessly seek to create huge bureaucracies, to engage huge bureuacracies, to create vast arrays of, not fishing tackle, but paperwork.
Rather than fishing the oceans clean as we almost have, imagine all the "fishermen" on land, at Starbucks, etc...
:)

This is exactly what I've been saying: any idiot can build a working AWE system using off-the-shelf components. There is no mystery, only laziness and lack of even a minimal amount of understanding/creativity. Like I've been saying also, this is a workable concept (whether it is an advantageous concept in any way is yet to be shown)

Skystream is a big, heavy choice, but at least it can be purchased today and used tomorrow. They have an abysmal record of reliability over the long haul. A large percentage are "not working" at any given moment, after many years of development including help from NREL.

:)
Doug Selsam