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


Reminds me of a paper I was reading last night

The idea being not to use the brake lines on a cargo parafoil guided delivery system
Yeah, makes it look like AWES should just drop out of the sky working already
Although for some primary school kids… That is what happens

Some kids get the ideas involved in AWES straight away.

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Seems like a diversion - changing the subject. Fluff. At some point, either you have an economical energy solution or you don’t.

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He starts off with just drawing things in the CAD program but after page 40 or so also does some modest testing. Not enough though. He reminds me of every beginning inventor too in love with his idea and drawing it in CAD to test if it actually works. He does seem to accept feedback and new information so if he doesn’t give up he may get somewhere in a number of years. He has made some progress already, with the help of the other forum participants.

The most obvious problems with the design to me are, I think he assumes the wind has a fixed 1Hz frequency of gusts and lulls, even at height… and he seems to want to use a 7 kilometer rope to lift a weight 1.3 meters 60 times a minute.

Some links and quotes from the thread:

Chassis Design of a Control Pod for a Kite Power System
Master Thesis Report at SkySails GmbH, Hamburg for Royal Institute of Technology, Stockholm.

New to me, and looks more promising to me, Horst Bendix:
New inland wind turbine opens up the high winds - Onshore wind energy urgently needs innovations that multiply the annual energy yield per plant and location. A contribution by Horst Bendix.

Thanks for the attention. What I did not find here is that there is a working small test system:


Good to see someone actually putting effort into testing a solution @thomas_neemann
Well done.

here is a video with explanations. with youtube’s automatic translation, subtitles can be displayed in other languages.


Hi Thomas, welcome to the forum.

I think you’re doing very well, testing and learning. Here’s my input:

I think your “stroke length” (1.3 meters) and “stroke duration” (1 second) are too short.

A test you could do is: attach a long (hundreds of meters) rope to a weight and use that rope to suspend the weight from a pulley or a ring. Now pull on the weight from different distances (5, 10, 20, 50, 100, 200, … meters) and see what stroke lengths and stroke durations you can achieve.

My guess is, the longer the rope, the longer your stroke lengths and stroke durations need to be. I would guess it is related to the sag in the line and the elasticity of the line, the speed of sound in the rope material, and how fast a wave can travel in the rope, among other things.

Don’t take this too seriously, I can find what I think are problems in every single thing. You’re doing well.

thank you for your cooperation. i also believe that it is a vibrating system. the length of the back and forth movement has a small range, which depends on the realizable size of the spiral disc. the size of the spinnaker and the elasticity of the folding mechanism have a large variable range. I also believe that it takes a lot of effort to get the best results

Greetings Thomas

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Here you start talking about the shape of your spiral disk: Open-source Höhenwindkraftwerk (Drachen) in Freecad - Page 39 - FreeCAD Forum

A little later you link this: Golden Spiral. - FreeCAD Forum

Can you explain why you want to use a logarithmic spiral? Most other ideas just wind the rope on a drum. To make sure the rope wraps around the drum correctly they also have an extra guide that the rope goes through that travels up and down the drum.

When you pull on a rope wrapped around a drum, the rope already always pulls perpendicularly to the lever?

It’s okay to write in German if you prefer. Some of us can read German, some of us can use Google Translate.

I do this so that even small gusts of wind can be harvested. In addition, very strong gusts of wind can also be used compared to an average diameter.

So this has 2 parts:

(1) Gusts, what are they, where are they, and how much power is in them, and (2) you use the logarithmic spiral as a kind of variable gear, what are the pros and cons of that and is that the best solution.

I think the first part is more fundamental and I think a bit more interesting and relevant to more AWE ideas, so let’s explore that a bit.

Perhaps an easy thing you can do to test how gusty the wind is where you are is to attach wool tufts to a kite line. You can do that at different locations and at different times to see how it changes. I’d be interested to see how it changes the higher you go.

Similar: How to use wool tufts to test car aerodynamics, though perhaps you may want to use longer tufts. And I don’t know if you’d better put little (styrofoam) balls on the ends or not.

the topic of wind gusts was discussed a lot in the freecad forum. many people believe the energy yield is too low.
there is a graphic in the forum about wind gusts.
my observations in nature are the treetops that swing back and forth in the wind.
the functioning test system confirms the possibility of obtaining energy from it.

That doesn’t need to be because of wind gusts. Apparently trees are like springs or cantilevered beams or pendulums.

Questions I would have are: what natural frequency does my system have, and how much damping (energy extraction) can I do?

Here are some results I get from searching for “trees swaying in the wind”:

The Secret Messages of Swaying Trees - WSJ.

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from my point of view the main problem is the permit in the airspace. I did not receive any. skysails power has got a limited term of up to 700 meters. as long as the problem is not resolved, i cannot continue. if someone is anywhere in the world where it is possible and they want to continue testing i can support them via the internet

Almost nothing in your design necessitates testing things above 100 meters. Pick a windy day and an open field and you can get 95% of the work done, I think.

Perhaps if you want to see what effect using a longer line would have you can put a pulley a couple of hundred meters from your ground station and run your kite line through that.

Your ground station as it is now is easy enough to make from plywood and steel tubes and steel angles. You don’t have a generator. Perhaps you can make a flywheel to test things instead?

yes you could do that. the generator is available and can be seen in action in the video.

but i don’t know whether it will achieve optimal results. if not, it would encourage the critics. the system is not very efficient, but that doesn’t matter at 7000 meters because there is always a storm there. it can generate base load electricity at night and when there is no wind on the ground. this information should reach the decision-makers. at the moment it is believed that the wind cannot deliver a base load of electricity.
that is the key point. you can’t demonstrate and prove that in 100 meters

I think Iceland has few limitations…

that could be. i heard in canada it is possible

It won’t achieve optimum results. That’s why you do it. To test it and improve upon it. No one is going to let you test things at 7 kilometers, or give you money to test things, if you can’t show results at 100 meters.

You can set a goal for yourself, for example: in 10m/s wind speeds it can generate an average of a 1000 Watts, and it can do this unsupervised for at least one hour. No one really cares if you achieved that at an altitude of a 100 meters or 2000 meters. You were able to light a light bulb. That’s a good result. It might be possible to improve upon it.

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