Not that I disagree, but taking the opposite position: good luck milking your ants and trying to make a profit, I’ll be over here minding my cows.
Aren’t larger systems easier to control, like it is easier to balance a broomstick than a pencil?
Probably the biggest uncertainty and dislike I have about AWE is that the tether is almost a consumable. So trying to improve that early on is good I think.
The maximum power of the 3 m² plane Ampyx looks to be good enough, unlike the average power. So there is likely much energy expended during reel-in phase.
Perhaps a rigid plane can plane, but how towing it with its long tether while it planes? As the rigid plane stall speed is rather high, I guess that increases the energy consumption even while decreasing the reel-in time. And the weight and drag of the alternatively (?) slack (?) and tense (?) tether during reel-in phase does not help matters.
Sticking with your metaphors…
It’s easier to balance a pencil case holding 10 pencils in 1 hand than 10 pencils with 1 on each finger.
As for ants and cows
Ants are super adaptable and socially scalable. They build their own protection in massive colonies. They collectively solve for group problems with resilient and efficient communication over massive networks.
Even with the enormity of human intervention
ants “monopolize 15—20% of the terrestrial animal biomass
About 10x the mass of livestock
Considering in this animal metaphor that wind energy efficiency is equivalent of feed conversion ratio
A cow needs many stomachs and regurgitations to partly digest a lot of cud.
An ant takes a bit of a blade of grass back to the nest to feed the colony over a long period, in a house made from it’s own shite - Impressive (although the decoration is not to my personal taste)
Also with the tether being a consumable already. That sounds like a highly optimised comodity. Use it carefully and efficiently like the well tested manufacturer spec sheet asks. don’t abrade it.
Here’s a good video on factors which affect rope longevity… albeit through cutting https://youtu.be/IL2r_f2g4Sw
There are some simple things: a rigid kite less than 50 kg can be handled easily even in strong wind. Not so for a 300 kg wing. And there is also the cost issue, and it is real. No omelette without a few broken eggs unfortunately.
On the small scale, at a certain size your components are getting too heavy. For instance we have a certain unit weiging a few hundred grams and spending power like there was no tomorrow. It just doesnt make sense to do a downscaling project for these components. Also too small wings and you are getting reynolds effects and you need really small fingers.
The sweet spot for me seems to be 3-8 m wing span (both Kitemills KM0 and KM1 are in this range). Still attending here in a personal capacity, not for Kitemill though, so I will not elaborate too much on that.
From the chart shown it seems they only have a selected few data points, and that the average power is quite low. They did not clear level 1 yet
There is little data, however the maximum values are far above the average values.
Full curves would be useful and maybe reveal a problem (too much power consumption) during reel-in phase. For flexible kites such (now old) curves exist and show a long time for the reel-in phase, about half the time, but also a reasonable power consumption. For rigid kites, for what I know, only Ampyx 3 m² plane data is available.
No I wasn’t pointing to that. To milk ants you’d need tiny hands and tiny buckets and tiny lorries, and lots of time. With luck and lots of R&D you could produce maybe a liter of ant milk a week. How are you going to compete with the farmer down the road with a bit more of a sensible business plan? The product looks the same on the shelves.
Hey I didn’t say it was a good metaphor.
It’s terrible.
I prefer oat drink to milk now anyways.
Let’s instead look at the practicality of farming Ants V Cows in your garden, for eating.
That new cow has already knocked down the chintzy garden fence and is ruining your neighbours magnolias.
You have on the other hand successfully already grown ants in your garden without serious issue ever since moving in.
My main problem with big wings however isn’t their horrendous control. It’s the speed of wind needed just to support the structure as a kite. Game over for big traditional manufacture rigid AWES wings in my view. There will be hybrids and ram air solutions
OK so we’re down to milking ants vs cows. Sure.
Anyway, I just noticed this “story” in a real wind energy publication, dateline May 21, 2021:
https://nawindpower.com/rwe-constructing-irish-test-center-to-investigate-airborne-wind-energy-systems
A future AWE test site in Mayo County, Ireland, for Ampyx and possibly others…
I got a bit of a DejaVu when I saw this story. I thought: "This sounds very familiar, besides the now-bankrupt previous KPS announcements of “renting office space” and securing a test facility in Scotland(?) where they weren’t allowed to test most of the time (how convenient) I felt as though I had already read this same story in the past. So I cut-pasted some of the article into Google and searched, and found a strikingly similar article from four (4) years ago:
The dateline of this older article was:
12 Apr 2017 (Last Updated April 12th, 2017 18:30)
but this dateline says the article was “updated” on April 12, 2017, so I’m not sure when the article originally appeared.
Now I certainly realize this stuff doesn’t necessarily happen in a few days, but we’ve been watching this “stay tuned!” drama for well over a decade at this point, and the theme still seems to be just finding or developing a place to even test - in the future. Really? After more than a decade, still no place to test? That’s what’s holding up progress?
I’m kind of thinking, why not just go test in a remote-yet-easily-accessible area, like, for example, the vast and mostly-empty Mojave Desert, and just do the testing without necessarily having to issue a press-release to let everyone know all the supposed details, years before they even happen, as though since it is AWE, all “accomplishments” are OK to perpetually take place in future-tense only (all accomplishments are (years) “in the future” and always will be)(?)
I just had a look at kitemill progress . @tallakt it seems you guys made great progress with a nice running device on the video. that would be great to have more details about kitemill. When did you plan to launch your product ? I’d like to have infos about that. I keep thinking the more AWE product available, the better for every companies as it help promoting AWE as a whole.
We are currently working on long duration flights. Right now the goal is 5 hrs hands off flights, starting from the landing platform.
Longer term we will install 12 units in a farm in the «Green Flyway» project located in sourheast Norway, close to Sweden. The wind resource there is quite ok.
The kites in this project will be «KM2» as opposed to the current «KM1» with 7.5 m wingspan. The KM2 is currently being designed with a nameplate capacity of 100 kW. That would be average power delivered to the grid, so the mechanical power in the tether would be slightly higher, and peak power during loops considerably higher.
This project again is funded by EU, as was our last project at Lista.
Anyways the «current» project is still underway, installing more «KM1» units at Lista Airport where we have our test site. The aim for these is to get more operational experience and tune the system at smaller scale. I can say this is a project of high complexity where we are making continuous progress. Though we are far from ready to present a power curve for the KM1. Anyways, the KM2 has a power curve fr advanced from KM1, designed a while ago when we knew less about AWE.
The design for KM2 is looking really nice with high capacity factor. Wingspan may be around 15 m (ish). Though I could not share more details, like in general I can only share what was already shared publicly.
The Green Flyway Project EU Innovation Fund awards 3.35 million to Kitemill
The Green Flyway may be considered a delivery of our end product, though really it is intended just a stepping stone to even larger scale.
In addition to the stop and go issue, the generator for a reeling yo-yo kite works at a lower rpm than that of a regular wind turbine, because the reel-out tether speed (during power phase) is about 1/3 wind speed.
As a result it looks that at similar power, the ground station is heavier than the nacelle of a regular wind turbine (HAWT) (see a comparative example below).
This likely involves additional costs, although I would like know if you can confirm it by your analysis or your experience.
RATED POWER
100 kW
1. Ground Station (GS)
Converts the mechanical energy of the kite into electrical power and reels the kite in by using the generator as a motor.
- Dimensions:2.44 m x 2.60 m x 6.06 m
- Weight:9.6 t
- IP Rating:IP64
- Lifetime:25 years
Hummer H25.0-100KW
Poids de la nacelle (weight of the nacelle):
2.2 t
So 9.6 t for the weight of the Falcon ground station, vs 2.2 t for the weight of the nacelle. Perhaps the difference would be lesser with other 100 kW wind turbines, and also by taking account of elements (such the winch) which are not used for HAWT. But it looks that the difference of weight is significant.
Hello Pierre:
The first thing to notice is the regular wind turbines are available now, in production, whereas the kite-reeling systems are perpetually “coming soon”. That should tell us one thing: They can’t quite even get kite-reeling systems ready for general use, no matter how long time goes on. We’re at 15 years now. Still pretty much nothing working on a regular basis. There must be real reasons, with all the talent and effort behind it.
I’m thinking the problems start with reliable launch and landing, extending to undue wear in the tether reeling system, possibly with gearing wear, maybe generator overheating, problems getting the software tuned right, and maybe kite wear in general, since I know hang gliders and paragliders are only good for so many hundred hours before needing replacement.
As far as the extra weight, I think it speaks to the excess mechanical complication involved, as well as possibly the lack of any reason to need the ground station to be lightweight, since it is not on a tower, and indeed maybe an advantage of it being heavy, so it is not dragged away by the wind, and can be used as-is, without attachment to the ground (no anchors?). The shipping container alone weighs 5000 lbs., which is two-and-a-half tons.
As far as the Hummer and Chinese turbines in general, it is a roll-of-the-dice, and you are definitely taking your chances. They do not have a good reputation for reliability. In fact, if you Google “hummer wind turbine problem”, you will find a lot of warnings about them:
hummer wind turbine problem - Google Search
Some of the discussions degenerate into accusations that the people posting work for competing Chinese turbine companies, talking up their own products or talking down the competitor’s products.
This illustrates how “the wind is brutal” and even just copying what is known to work well is difficult. You’d probably be better off buying a used Vestas from the 1980’s, and rebuilding it.
The thing about wind energy that escapes most would-be innovators is any machinery likes to work in a sweet spot where no component is overly-stressed, where forces balance, and do not reverse a lot, but rather stay more constant.
Think of buying a new car and immediately driving it off-road at high speed on a regular basis. It will quickly start falling apart. Drive the same car at reasonable speeds on smooth roads and it will last many years before having a problem. Same with any machinery. If you want it to last, it has to be designed and built to last, and operated conservatively. 
Hi Doug, thanks for the information.
Typically an empty 20 foot shipping container weighs between 1.8-2.2 metric tonnes (about 3,970 - 4,850 lb)
Poids de la nacelle [weight of the nacelle]: 4.6 t
Here the respective masses get closer, taking into account the mass of the container.
Furthermore, as you indicate, and taking into account all the elements, the mass of the ground station does not necessarily imply an additional cost of the generator.
This may not be completely true, because for the classic wind turbine the power take-off is at the hub, where the linear speed is low.
Intermittent operation in two phases (reeling-out and in) can indeed cause wear on the generator itself, the winch, as well as the kite.
Yes well, I just happened to know the weight of shipping containers since I was looking for one to use for actual storage, and found I have a neighbor who is a dealer. I was referring to a high-cube 20-footer, a foot taller, which weighs a bit more than a standard 20-footer.
Don’t forget, a gearbox or drive-belt setup will raise the RPM of the generator/motor.
Also, I didn’t mention, above, whatever difficulties might arise in automating the flight path of the “kites”.
There are other factors about current approaches to kite-reeling that seem problematic to me, which I choose not to mention, on the basis of sometimes keeping my opinions to myself, in the category of “if they don’t see it, I’m not about to try to explain it”.
Well, and also the cost.
Gearboxes are used to LOWER the cost compared to direct drive generators.
Direct-drive (low RPM) generators are bigger, heavier, and more expensive, but with less wear, last longer. Gears wear out.
Hello Doug:
Yes, the intermittency of the reeling mode and the irregularity of power in crosswind flight (with a notable exception by using flexible kites in Low radius loop) are certain handicaps and cause possibly crippling problems.
But the yo-yo mode allows you to limit the mass in flight and generate a lot of power.
And generating properly with something like a conventional wind turbine or a Kiwee requires too much lift as the dimensions increase.
Agreed, but these well-discussed characteristics are not what I was referring to.
You were referring to:
It’s the operating principle that’s wrong. It’s like moving a wind turbine downwind to unwind a winch. Soon in this forum we will become SuperDoug 
.