Hey there, I’m brand new to this forum so forgive me if I am breaking some rules with this post.
As an engineering student, me and a couple of friends have picked up a passion project to design a small scale kite power generation system which would ideally be capable of supporting a small payload.
Currently we are planning on using a system which generates power by reeling out the kite, then reeling it back in once it has hit it’s maximum height to then release it again.
So, at the current point in the project we have hit a sort of roadblock; We have no idea which kite design would best suit our needs. From looking at KAP kites, we have found some possible models to use, such as a delta conyne, a maxi dopero, a rokkaku. We are trying to stay away from power kites since we are aiming to create a small scale system, and it would be difficult to anchor a power kite while remaining a small size.
I am hoping that some more experienced folks on this forum could possibly help us out? We are mostly aiming to be generating a net of 20 W of power, so very little compared to other designs I’ve seen posted here.
Please describe a bit more. Is the purpose of the rig to lift the payload with the kite? In that case a normal kite is sufficient. Also if you want to do something like kitewinder is doing. If you want to go drag mode or lift mode (eg Makani or Kitemill) you need something steerable with somewhat high lift-to-drag number. Or you may even go rotary?
It all depends on how you want to make 20 W. When I know I will supply more concrete suggestions…
Suggestion: Pick a stable KAP pilot-lifter of your choice, and use the line as guide to operate some sort of “kite-messenger”. That solves the flight-control challenges, and you just need to design and rig a PTO (power-take-off) line or loop.
Please share your results, and let us know of any problems.
@DudeInCorner intends to implement a yoyo (“reeling out” “then reeling back”) kite which is not a crosswind kite (“to stay away from power kites”). In these conditions a kite with a frame would be difficult to depower if it is even possible. A soft lifter kite could be partially or fully depowered by using an additional line that is fixed on the nose.
As a rule, a single-line pilot-lifter and a multi-line power kite do not perform each other’s function well. There are two basic soft PLs, a parafoil or SS (single-skin), and neither “powers” or “depowers” well. WPI did a pilot-sled AWES, but that’s not soft (has sticks), and it did not work well. Skysails uses a power kite, but its a rather complex solution with control-pod and software dependence.
A flat stick kite depowers better than a soft kite (but does not scale as well). The kite messenger in the video is seen depowering as a stick kite, proven “possible” as a traditional method. Depowering with an extra line on a lifter is hard to reel collectively for power and control.
Kite store practice is to carry only good kites and let the buyer choose as their heart wishes. KAP kites are great, with many fine web recommendations. The messenger completes the AWES without a “crosswind” power kite.
Personally, I would get a ten-foot Delta like this Gomberg Falcon, and make an extra large messenger to get 20W in moderate wind. Standard toy messengers are more like 5W equivalents.
Hi all, thanks very much for the replies and the help, allow me to catch up.
tallakt : The main purpose of the system is to produce power while remaining somewhat compact, the payload is just an additional accessory which would be fun to have but again is not really our main goal. Our current plans on making the 20 W are to have a reel in and out system, it appears this is called a “yoyo” system as Pierre posted below your comment. The Kitewinder seems really cool, however it also appears to be out of our skill range. Thanks!
PierreB: Thanks, we have not really considered that a stiff kite would be more difficult to depower than a soft kite. Though, would a soft kite still be able to generate the lift needed to support a payload? If I am thinking right, soft kites do not generate much force.
Kitefreak: We did not at all consider the usefulness of a kite messenger, but now this seems like it would end up being the best option for our goals, thank you very much!
So now I guess the question becomes what kite messenger to use? This parachute kite link you posted Pierre seems interesting however as kitefreak mentions wouldn’t a parachute kite have some issues ascending the line when tilted?
The answers you’ve gotten assume you want the system to work without you using your hands. You’ll be able to make more power and have more fun if you do use your hands, by flying a multi-line stunt kite or power kite. You’ll also be able to experiment with flying patterns and see what patterns generate more electricity.
A search for all Kite Messenger videos and pages will reveal many traditional variations, plans, and design ideas.
If you are being graded for AWES autonomy, the messenger is magic. Windy Skies is right for you not to neglect feeling kite power. Try a kite like this Prism Synapse, for ~50USD, and maybe get ideas for future work.
Consider AWE as a hot career path, not just a great student project idea.
A non crosswind yoyo reeling kite is not easy to do because of the expected low difference between the power and depower phases. With a crosswind kite (“with flying patterns” like @Windy_Skies indicates) the difference will be higher, allowing an easier management.
The Acro Kite was sold as a RC stunt kite. Perhaps it can be transformed in a yoyo kite.
Hi. I’m going to go against the wood grain here compared to the other guys on the forum and give you some alternative recommendations (not to say that the other recommendations are bad).
As the scale is so small, weight is not a big issue. If you want to loop, a RC sailplane should be able to do the trick and have everything pre-assembled. You could use a plane without a propeller, although a plane with propeller will allow you to launch easier - perhaps some kind of hover capable plane is usable if you have the flying skills. Make sure the plane has dihedral or swept wings. I can’t vouch for any of the following planes, but they could be a starting point:
The tether should be in the approximate length 50x-100x the wingspan, and should not be thicker than absolutely necessary. Use dyneema fishing line that takes only the exact load you require. You might also want a slightly weaker piece of rope to use as a weak link to protect your wing from breakage. Remember the wing is only dimensioned to withstand the approximate weight of the fuselage. Perhaps do some simple tests with weak links before you fly. Fasten the line around the center of gravity below the fuselage. All of this will probably take quite a bit of tuning in order to make it work.
If you want to increase the load, perhaps take a look at the “hydrid bridle” described in Windlift’s patent.
The problem will be actually flying the thing. I recommend using a bridge or a tower to practice so that the kite will not hit the ground. Another alternative is buying a simple KAP kite of Pilot kite (1-2 square meter for light winds) and fix the tether for the RC plane somewhere on the tether of the large kite. If you use a kite like this, flying the RC plane will feel really spongy. In ideal conditions, you might be able to loop the kite using only the rudder.
Dont use a winch until you are comfortable looping in wind. Just tie it down at first.
Once you are capable of flying this, add the winch and then possibly a servo controller to program the flying paths.
I should warn you that what I described will take heaps of effort, broken propellers, crashed planes etc etc. But it’s a lot of fun though.
Take care with the heavier model - they will be lethal weapons once subjected to wind.
Following up on Tallak’s suggestions, kPower has long proposed that passive pilot-lift solves excessive crash-risk of current software-dependent kiteplanes. Note the wing remounted upside down for “negative-lift”, the turbine-guard as added forward vertical surface, expanded empennage surfaces, and fully self-flying dynamics.
Lets be very careful advising students in AWE, a demanding aerospace field.
Students should design and fly at least a 3x tether-load safety margin, not zero safety margin. Moderate loss of performance for a student is not a problem, and limited velocity is safer. Very few students have easy access to the bloated airspace and extreme altitude being implicitly recommended (“50x-100x the wingspan”).
Be careful about costs, most students are poor. Pay-to-play tech is bad education. Kiteplane advocates rightly assert many crashes will occur, but how many replacement gliders should a student buy? Not as many as oversold Venture Capitalists can buy. A cut-and-paste shopping selection of gliders is more consumeristic display than great education.
I personally use the products suggested, and know the developers. kPower salvaged the same cheap junk Foamy UBonn suggests, and did not even need the radio/servo/control elements. Instead of ~1000euros, kPower only spent 30USD for a Dan Tracy flygen turbine, and a good pilot lifter is not much more than 100USD.
Critical-flaws inherent to common kiteplane AWES architectures are mentioned, but a student might not heed concerns. While risk is fairly low here, advocating known-dangerous AWES architectures presents moral and legal risk. Student projects should not fail due to buggy third-party beta code either, unless its a computer science class.
A modest AWES demo can be more revolutionary than a flashy VC fad architecture. Lets not saddle students with high-complexity AWES nightmares. Traditionally progressive toy and hobby kite culture is the best match to popular and student AWE interest and resources. Such kite culture teaches AWES topology exploration far better than AWE VCs so far. Low Complexity creative exploration is where AWES educational gold lies, and maybe also for industrial gold.
This should not be a question of optimal architecture. I believe if the smaller planes are chosen, it is not very expensive not very dangerous in case of an accident. For sure find a place to fly where noone gets hurt.
They wanted to build a yoyo rig, so thats the advice I gave. They might have wanted to build any other rig I would have welcomed that also.
With regard to cost, its always nice to find something used/disposed and make it work for free. But sometimes its also nice to get the correct parts in time and without too much searching. Even so, the costs for the listed equipment is almost as low as you could hope for.
The comments you made in the post above seem out of proportion and even non subject for the thread.
So I stand by my initial advice as pretty sound. Also read DS’ comments about safety and be careful.