"Autonomous Airborne Wind Energy systems: accomplishments and challenges"

Authors: Lorenzo Fagiano, Manfred Quack, Florian Bauer, Lode Carnel, and Espen Oland
Annual Review of Control, Robotics, and Autonomous Systems 2022 5:1

An interesting publication comprising features and reports of tests from different AWE architectures and companies. The figure 15 is particularly significant.

Below is a pre-print:

Those Kitemill numbers were interesting to me also :slight_smile:

More blah-blah-blah. Can’t even read it. Skipped to the conclusion. All accomplishments perpetually in the future.

1 Like

Hi Doug, I would think that some accomplishments are rather in the past. Indeed, concerning pumping power, measurements on tests were carried out.

Ruppert 2012 pdf is available on the link below:
Table 8 page 44, dataset 5: Mutiny (25 m² kite, see page 8), 8 m/s wind speed, 5.19 kW average power, 14.1 kW average generation phase.

The average cycle power / average generation phase ratio is roughly the same as said ratio deduced from Figure 15 (average power 92 kW, with peaks of 300-400 kW). However, the scale has increased considerably.

Hello Pierre:
Perhaps I exaggerated somewhat, but the theme continues - unlimited projections for the future, little or nothing to show for today.
As I’ve long-stated, there are unlimited ways to get some power from the wind. The question is whether you have an economical energy solution or not. Wildly optimistic predictions for 13 years, of powering hundreds of homes, then more (usually at some remote site, such as an island), but where is a single house powered by AWE today? Some things have not changed at all. Read the hype, then forget all you read, don’t ask any questions, to clear your mind in preparation to then read more hype. How many times can one go through this cycle?

AWE after 13 years of this hype, still doesn’t understand the most basic terminology in wind energy: a lift-based system versus a drag-based system.
“Hello, may I thpeak with Profethor Crackpot, pleathe?”

Page 20:

earlier KM0 prototype, with a wingspan of 4 m

Page 22:

Figure 18
Experimental results with Kitemill’s KM0 functional prototype. Generated mechanical power over
several pumping cycles.

This Figure 18 looks very clear. During reel-out phases the (positive) mechanical power seems to be about 1000 W and less, then 500 W and less, while during reel-in phases the (negative) power consumption is about -1000 W, which seems huge (limited depower?), even considering that reel-in phases is only about 1/3 or 1/4 time (less than for flexible wings) of reel-out phases. By taking account of these values, the average power could be very low.

Not the KM0 nor the KM1 so far are geared towards making maximum power output. Getting there requires a lot of other steps to be completed first. Eg staying airborne for more than an hour at a time and measuring the wind (presumably by LIDAR). Right now Kitemill is flying the KM1 (~7 m wingspan) on a regular basis (more than a few times per month), and trying to increase the robustness of flight and other practical matters.

I am sure Kitemill headquaters will announce when we have actually produced something close to the expected average power output.

I cant go into details about exactly what we are working on, but I can say the gap between thinking you could produce power in theory and actually doing it requires a lot of «boring» work to be done, and things like weather conditions cant be accellerated…


From 3:07 : comparison between reeling 3 m² plane (2.5% of potential, huge difference between average power and maximum power per cycle) and fly-gen 4 m² (25% of potential, so 10 times more). Was the fly-gen plane more optimized? Not sure.

During reel-in phase the weight of the plane (increasing more as it scales up) must be compensated by lift to allow effective control. Lift leads to some drag, and the apparent wind due to reel-in operation adds to real wind… So huge power consumption is not so surprising, and avoiding it looks difficult.

And as it seems (albeit with a high degree of approximation) that, despite years of research, the average cycle power / average generation phase ratio has hardly changed between the old and recent tests of soft wings in yo-yo mode, as I pointed out, one could deduce that the optimization for energy production of a rigid wing also in yo-yo mode could prove difficult for the less.

1 Like

Wow, agonizing to watch.

Already for the reproduced comparison page.