Page 232 of Part I (thanks to @Rodread to indicate me the curve in the figure 3 with the text below) :
Figure 3: Power curves for the M600, showing the large gap between original design intent and
the realized system. Data shown is a subset of flight test data to isolate a single configuration.
Note that our modeling tools accurately predict the performance deficiency of the M600.
That confirms my observations about power curves of videos on some previous posts like this one or this or this another.
Hello Pierre:
I completely agree with your assessment regarding the lost opportunity for harvesting electrical power while the heavy aircraft laboriously struggles to fly uphill with every rotation. It goes back to what I’ve been saying for well over a decade now, regarding most AWE efforts: these people don’t know what they’re doing. I don’t care how many fans they had accumulated, how many flattering articles were published repeating their public relations statements, how many “highly-talented” engineers and programmers they hired, a thousand flies can all be wrong, when the basic concept has such blatant holes in it. I would go on to explain more, but at some point I’d rather let people figure it out for themselves. Whether they ever will or not, I don’t know. Maybe I’ll get around to explaining it someday, but it basically goes back to not understanding, or maybe just not sufficiently appreciating, possibly just ignoring, how existing technology works, sufficiently to retain certain overwhelming advantages, gained over thousands of years of wind energy development. Where did they go wrong? If you don’t see it, I’m not gonna mention it. Ignore what was already known 1000 years ago, and you get what you get.
Hi Doug,
Indeed the high speed of the wing accentuates its kinetic energy (wing mass X wing speed² / 2), and this roughly two times more while going downwards than upwards due to gravity, the wing speed² doubling. Downward momentum + gravity is like a “double penalty”. I think Makani more or less mentioned this issue by using “potential energy” expression.
I saw the Makani movie just now and it is clear that they were far from a fine tuned AWE unit. We will never know, but I only know that what was shown was a lower limit to performance that could only be improved upon. Sure complexity and large mass is a big deal. Mass could be alleviated by using three simultaneous kites in a triangle (not solving lower wind range though). Complexity - well I dont know. But it seems they were pretty close to something, and that something could be made to work. But at a cost that did not make the effort worthwhile… I say this opens up the door for anyone who can figure out how to do this cheaper and with smaller mass…
As an interesting takeaway, they made a carbon fiber tether. This could increase the strength to diameter ratio. I leave the details to anyone mechanically inclined. Anyways, their test failed.
The effect this sudden release of Makani data and media is interesting.
OK the film is inspiring but myopic. This is the documentary of 1 engineering company not of the field of AWE Science and engineering (unlike the AWE documentary by Chase Honaker)
The list of employed jobs at the end tells a large part of the story too.
The work was massively impressive but deserves generalisation across AWES.
With the claimed intent of work … The results should probably have been shared more frequently in smaller just as fabulous bite size releases.
Suggested edit… here is the film documentary
I was getting right into studying the fairings on the tether and bridle
But then the last minute of this video is black
From what I remember there was a ground power overload (They were kicking out a lot on this test) and the power up the tether was cut from the base station. You can still hear the commentary.
It’s odd, looks like the (large) tether fairings are set on the tether really firmly and use an aerodynamic force to align.
Some freaky sideways flying in this vid, the camera angle is great.
There are 2 other camera angle of the incident.
This one
Really shows the shift in balance between the frame and bridling through the last few loops.
Great to have the control audio too really reference each point from
I think they should have waited with the fairing tests until they had the rest under control. But now that they did it, it does seem to work. There are some other fairing videos from the bridle where the fairings went into oscillary pitch angle.
and analysing side-slip
One thing really bugging me is the pylons don’t seem to match the overall asymmetry built for encouraging rotary flight… Maybe I’m seeing them wrong
The video below shows a largely positive generation with about 12 m/s wind speed. We can deduce that it would be the same with lower winds for a lighter wing.
The robustness issue could perhaps be mitigated with the implementation of other structures such as the biplanes developed by KiteKRAFT.
If only I had 10th of the data in this 1 report for Kite Turbine performance analysis.
As beautiful as the data is. This is hard science time.
So in the words of Richard P. Feynman
First you guess. Don’t laugh, this is the most important step. Then you compute the consequences. Compare the consequences to experience. If it disagrees with experience, the guess is wrong. In that simple statement is the key to science. It doesn’t matter how beautiful your guess is or how smart you are or what your name is. If it disagrees with experience, it’s wrong. That’s all there is to it.
Makani’s kite was susceptible to “roll excursion” in hovering. This was likely the most severe problem of the concept and led to several crashes or almost-crashes of small and large kites.
Makani used a Y-bridle tether connection at the kite which in principle should give a restoring moment for any roll excursion, both in crosswind flight as well as in hover.[…]
In the technical report https://storage.googleapis.com/x-prod.appspot.com/files/Makani_TheEnergyKiteReport_Part1.pdf p. 26, 59 as well as 253 and following, further challenges of Makani’s kites are explained. It provides a justification for the low power generation efficiency.
So there is matter to discuss about the real importance of the Makani’s Y-bridle tether connection as “a justification for the low power generation efficiency”, and also concerning crashes.
Are there not more fundamental structural causes resulting from the weight in flight and the stress on the wing?
Exclusive: Airborne Wind Energy Company Closes Shop, Opens Patents
Former chief engineer of Makani speaks to Spectrum about energy kites and the future of AWE
Don’t take Makani’s word for it, though, says Echeverri. Not only is the company releasing its patents into the wild, it’s also giving away its code base, flight logs, and a Makani flyer simulation tool called KiteFAST.
“I think that the physics and the technical aspects are still such that, in floating offshore wind, there’s a ton of opportunity for innovation,” says Echeverri.
One of the factors the Makani team didn’t anticipate in the company’s early years, she said, was how precipitously electricity prices would continue to drop, leaving precious little room at the margins for new technologies like AWEs to blossom and grow.
“We’re thinking about the existing airborne wind industry,” Echeverri said. “For people working on the particular problems we’d been working on, we don’t want to bury those lessons. We also found this to be a really inspiring journey for us as engineers—a joyful journey… It is worthwhile to work on hard problems.”