Open-source Höhenwindkraftwerk (Drachen) in Freecad - FreeCAD Forum (open-source airborne wind energy project in freecad)

that’s how I see it too. a friend of mine is a pilot, he says there is often turbulence at around 400 meters. However, an automatic take-off and landing system makes sense at altitude.

For what I understand and I have experimented this device work like a yo-yo (pumping) system where the reel-in (recovery) phase is assumed by the spring and during lulls, leading to short strokes. There is no crosswind flight, only the traction of the kite(s) going downwind in each power stroke during gusts.

1 Like

yes, that’s how it is explained

So to be clear, the amount of energy extractable with this method will depend on the magnitude and frequency of gusts.
Is that correct?

yes, you can say that. the greater the difference in wind speed between the maximum value of the wind gust and the lower wind speed shortly before the next wind gust builds up, the more energy can be obtained.

Initially, it will be easier to try to develop this product by flying close to the ground, taking advantage of the turbulence that, moreover, other wind power systems have difficulty in capturing effectively. Scaling up close to the ground should be feasible to a point.

Perhaps the system comprising the “vorsegel” (power) kite could scale cheaply by using a Stratta-Tarp-Kite and a light generator coupled to a dog leash, or the ground system that is already developed.

I don’t think so, see my previous comment about trees being like pendulums.

Also now aeroelastic flutter springs to mind.

the more it is tested, the better. i have tested for years with a wide variety of constructions. a spring manufacturer told me that torsion springs can only withstand this frequency for a few days. hence the construction with the spiral and the weight. my test system is installed in a chevy g20 van. as soon as I get a permit for 3,000 to 7,000 meters somewhere, I can go there and test.

I think it’s an interesting thing to brainstorm about. I think you can imagine it like a seesaw with a kite on one end and a weight on the other. The generator is the fulcrum. You would like to be able to move the fulcrum to account for different wind speeds, and perhaps also change the weight.

Here’s my submission:

a: drum for kite line
b1,b2: continuously variable transmission (CVT), see: https://www.youtube.com/watch?v=eFShKSFnrGw
c: drum for weight line
d1,d2: gearing between weight shaft and generator shaft
e: generator

Note the significant gear reduction from kite line to generator shaft, this increases the stroke length of the kite line.

I think this is another way to do reel-in-reel-out, using the weight instead of supplying electricity to the generator to reel the kite line in. Now you can decide for yourself if you want to generate electricity reeling in or reeling out. Or perhaps both if you can quickly “move the fulcrum”.

yes, i can imagine optimizing the mechanics. the greater the possible power transmission, the better. in order to replace a nuclear power plant, 1000 awe power plants with an output of 1000 kw will be used. the gearbox and the mechanics would have to be designed for this.

I believe such a system can not perform well in a wide range of wind conditions. Please prove me wrong…

I can only prove something when I can test in the heights. my hope is that the kite will automatically move up and down with the highest wind speed.

The energy band your are harvesting is reliant on the amplitude of modulation of line tension from gusts and how that resonates with your spring tensioning system.
My instinct is… It’s a limited resource in comparison to the constant mass flow energy of harvesting wind instead of gusts.

it may be that it is so. on the other hand, neither enerkite nor skysails has so far generated significant amounts of energy.

Have you contacted this center for advice?

Nationales Erprobungszentrum für Unbemannte Luftfahrtsysteme
https://www.dlr.de/ux/de/desktopdefault.aspx/tabid-13303/23288_read-67121/

Some of the interesting articles in their news section:

https://www.dlr.de/content/de/artikel/news/2020/02/20200519_dlr-forscht-an-flexibler-fluegelhaut.html;jsessionid=4DC7AB8072A6283C194DB5E6E577F44D.delivery-replication1?nn=0cb29f2b-41da-48a5-aa41-05bfb73de2e4

https://www.dlr.de/content/de/artikel/news/2019/04/20191119_supereffiziente-fluegel-heben-ab.html;jsessionid=2F58F268CB8C41BACAA6CE42BE93D751.delivery-replication2?nn=0cb29f2b-41da-48a5-aa41-05bfb73de2e4

1 Like

no, I didn’t know that yet. thanks for the hint. I will try to get in touch with it

How can it suit your kite and spring selection, if you cont control the motion of the wing. Eg. in high winds the spring will be fully compressed resting towards end stop. Remember drag is windspeed squared. And in low winds, the wind may not be turbulent or if it is turbulent not strong enough to compress the spring significantly.

I think for this to make sense, you must have a way to power/depower on command. Relying on the natural wind to fit your control needs seems like a longshot

But Enerkite and Skysails at least have a good story to make people believe that they may produce power in the future. If someone were not convinced they would not get funding. And I am pretty sure people will not part with their money very easily.

I am not trying to kill your project here. Or I kind of am, but you should be able to convince me I’m wrong. I could even help you make an argument in the future for someone important to you. But I will not give you a BJ, i will say exactly what I believe is true, it may not be easy to hear…

i am in close contact with skysails. that is the reason for my development. from the beginning i was of the opinion that skysails was made too complicated. I have time. at some point is the right time. at the latest when there is no more oil for the aircraft, our kites can fly in the jet stream.

You could potentially change the hold point on a variable force coil spring…
e.g. by having a wider span of grip on the ends of the spring in light winds… more length and thinner material would be available for the central unwinding spool… You’d have to tighten up the grip ends towards the centre and take shorter strokes in higher wind