In some sense we attempted to make “the pyramid”, or at least a simplified version of it The video is from August 2020 (almost 2 years ago). We did run it much faster, but couldn’t find that video easily. Our idea was just that it would be best to start making the prototype with the aid of static stability (higher tower, and a main boom).
Once we had a product commercialised we could later transition towards an airborne version if we found that path suitable.
The prototype was succesfull and produced meaningful power. For the next iteration we decided to make a mode sturdy design with a 3d printed tail. This in turn require more tip mass and the planes became too heavy for the structure - we ended up with the most nasty of oscillations in the rotor.
I find the concept very interesting/compelling. One might even add a guyed tower to reduce the cosine losses :D. There is still a lot of details to be worried about - and even making a system with passive (like ours) stability is tricky.
Another issue we faced was the phase lag in pitch/ angle of attack even with the ultra low moment of inertia wing - as the wing moves through wind shear and on a slightly inclined plane. Active control can solve this, but we never attempted.
I was looking for this video then found it. Bladetips Energy seem to use a similar scheme to increase bridle size like The Pyramid. It is a bounding design with pulling energy transfer though [yoyo] while the Pyramid is rotary energy transfer hovering AWE [stationary].
For the Pyramid the wings are similar to Kitemill/Ampyx kites but this is largely just a graphical thing. A detailed design phase would give a kite design that is most suited. I am for example also open to using soft kites in the Pyramid. Many options are on the table. Also assymetric blades such as Bladetips were showing. To be honest, I am unsure if you can load the blades fully with the tether connected only on one side of the blade, the way shown in Bladetips’ video.
One important difference is Pyramid connects the tether directly to the fuselage close to CG. Bladetips connect to one end of the wing. I think this is likely the way to go. One thing, the kites could release and land safely one by one. But also, in production the bridle connected to the wingtip is a very new and risky design, according to aircraft tradition. So I dont really see the bladetips kites/blades being superior to a stabdard glider with tether connected at CG.
Remember also The Pyramid is just a concept sketch, much work remains to make something usable.
I can also add, using an off the shelf glider design would accelerate testing the concept. The assymetric wing would most likely give gains in a smaller looping radius, but Im not sure if that is very important
I would think that if you attached the tether to the wing tip, if lift increased beyond the weight of the glider itself it would behave like I would think a control line controlled model airplane would and fly in a narrower and narrower cone until the reduced lift from the lower projected area of the wing matches the weight of the airplane, and possibly crash in interesting ways.
Or maybe with the centrifugal force and the low radius that we see here it works out.
I think it would fly in a cone to some extent. With a larger looping radius [and scale], the cone would become steeper. As the «ideal» way to spend the lift would be to have it aligned to the rotary plane [my assumption, probably not a generic truth], having the tether at one end with the cone seems a wrong starting point.
The tether should be attached near center of lift, or on a bridle connected at either sides of center of lift
Related, Pierre’s comment has what looks like good research.
I was thinking if you fly a control line plane on a long tether (with the tether attached to one of the wing tips), if you fly it faster and increase the lift of the plane, it would fly in a narrower and narrower cone above your head. So then the lift of the plane would increasingly contribute to narrowing the cone and less toward fighting gravity, reducing tether tension and… But you still have the propeller so I don’t know anymore, or if it is a perfect analogy.
The analogy would be for what would happen if instead of attaching your tether to the center of lift of your kite, you attach it to one of your wing tips, like Bladetips’ animation shows.
If this concept is for yo-yo
It sounds like the Diehl, kiteswarms, Leuthold et al Mawes pumping
A control line plane gives a light airframe but with 2 lines to drag.
For the Mark D Moore CSR concept - excellent link BTW. He already suggests how it can be used in both classic AWES modes (not rotary). Pretty sure the tether would be better attached to the centre of lift not the tip (inside rotor tip) for efficient transfer of lift to the lines.
The Pyramid could be a good AWE plan for offshore installations. Its possible limitations in altitude, comparable to that of regular wind turbines (HAWT), would not be an obstacle. Indeed, the wind gradient is lower in the open sea, which leads to lower gains by gaining altitude. And the advantages compared to HAWT would be: less mass as expected, less concreting, less destruction of the marine environment, more easily accessible generator… And compared to other AWES: less length of rope obstructing the maritime traffic…
Thanks. I would maybe tend to go further, maybe high altitude AWE is not as feasible as first anticipated, driving all groups to shorter tethers to reduce drag.
Compared to a HAWT though, you should still see a noticeable increase in altitude for the same power
If you don’t do that you put your system efficiency so low that it makes no sense in competition with HAWT.
Also, short tether means less usage of ground area.
This is pure speculation of course.
I also agree that offshore is where The Pyramid would shine. Mostly due to excessive free space and the likelyhood of a crash being fatal is small. This is not specific to The Pyramid though
The nice thing about the high altitude theme was nobody was going to ask anyone where their current high altitude wind energy system was, because it sounds like it might be difficult, therefore it served as a delaying tactic to keep people excited, without expecting anything actually working anytime soon. It allowed the big-talkers and questionable dreamers to dream and talk big, even comparing themselves to Einstein and The Wright Brothers, without ever having to show a working system. When questioned, they could say “Einstein was just a theoretician - are you arguing with Einstein?”
And so many newfangled wind energy proposals rest on their laurels, by citing use-cases that are too large, too expensive, too complicated, or too remote, to implement now, so they can just keep talk-talk-talking about it, while never having to prove it.
Think: “Laddermill”.
“This is a great breakthrough!”
“So why don’t you build one?”
“It would be too hard!”
“Then what are you talking about?”
“Shut up! We’re busy flying kites!”
Do you really think this argumentation is valid for «The Pyramid», or are we just seeing the cracked record repeating itself?
I was never involved nor very optimistic about the Laddermill.
I have done considerable work on «The Pyramid». Though it is so far only on paper. Talk is cheap. But that also means in a sense talk is good. The earlier you can invalidate a design the better. If you never have to build a prototype you saved so much time.
I had so many poor ideas over the years I am glad I didnt build most of it. And also started so many projects that never were completed. Total waste.
If discussing ideas bore you maybe just leave them alone…
Building «The Pyramid» would take many weeks, months or even years to complete. You may appreciate that having that amount of spare time is difficult to achieve. And then theres always the question that I am in fact already spending all my work hours building AWE systems at Kitemill.
Hi Doug, You said that SuperTurbine ™ was the logical continuation of Laddermill. But The Pyramid seems to be considered by his author as "my “Superturbine” ". by a similar reasoning.
Indeed we have a large number of theoretical studies around AWE, and also some data from real experiments that are valuable. A cross-check with necessary extrapolations specific to the investigated method can be sufficient to determine if such a method can be promising.
With a little practice we can debunk our own bad ideas, without having to build prototypes.
And yourself @dougselsam , do you never debunk some AWES (kite-reeling for example)? Do you build prototypes for this?
That said, when a thorough investigation finally holds up, building a prototype eventually becomes necessary.
I tried to see if some data could be transposed for The Pyramid, taking as a basis @Ollie’s thesis , pages 64, 65, 69, and Fig. 3.7 (photo of rigid Daisy p. 65) and Fig. 3.10 (p. 69).
Page 64:
Similar to the soft wings they are mounted on a carbon fiber ring with a radius of 1.52 m. The outer tip of the wings, when flat to the rotor plane, have a radius of 2.22 m. Therefore, 0.3 m of the wings span is inside of the rotor ring.
The Fig. 3.10 confirms the diameter of 3.04 m for the carbon fiber ring. The diameter of the following ring is 1.64 m. The distance of the two rings (corresponding to The Pyramid’s tether length), is 3.6 m.
I kept only these two rings for making something more or less similar to the The Pyramid, because there are no rigid parts between these rings, only tethers. The lower ring would be the cartwheel, and the upper ring would be the three kites (blades) sweeping a loop of 4.44 m diameter.
So: r0 radius is 0.82 m; r1 radius is 1.52 m, and 2.22 m with the wings; tether length is 3.6 m. Please @Rodread could you evaluate the power at 12 m/s (I remember more than 1 kW but I am not sure for the wind speed), and also the TSR (4?) then the lift-to-drag ratio. These values would be compared to the theoretical values. The area of each Daisy’s blade (0.2 m² ?) seems to be equivalent to that of each Excalibur (0.19 m²).
According to my rough preliminary evaluation, the values of the rigid Daisy tests could well correspond more or less to the theoretical values provided or expected for The Pyramid, especially since the transfer rings of the base will have been removed, keeping only the 2 upper rings, including the rotor.
Hi Tallak:
I was just having a little fun there, don’t take it too harshly.
It is actually nice to see people finally gravitating toward some of the vast possibilities offered by the general SuperTurbine or Rotary concept.
But I think we all tend to spend too much time theorizing and sometimes seeing how complicated-sounding we can make something, how many formulae we can apply, etc.
Just as I think many wannabe experimenters spend too much time “on paper”, maybe I spend too much time “on computer”. It has just been too tempting, from the very beginning, having seen the similarities of AWE efforts to the many crackpot wind energy wannabe efforts of the past, not to mention it. It started out as a friendly warning to the various early big-talkers in AWE, but turned into an ongoing debunking effort due to the early resistance of some of these wannabe innovators to facts versus fantasy. I love all the ideas. Heck I have so many myself. But as with laddermill, all this “effort” of talk-talk-talking about ideas is no substitute for a working system.
Also, I did not mean to imply that Tallak was a promoter of Laddermill.
My only point is it is easy to take any raw idea and extrapolate toward where it “would” work really well, when it remains to be seen if it works at all. The laddermill subject is just one example. There are a million excuses to not try something, such as with laddermill, how difficult it would be to build a really good version. My take is, how about starting with a version that even works at all, even if it totally sucks at first, and there is where the actual learning curve can begin, because as long as an effort remains “on-paper”, in “theoretical-land”, especially in wind energy, little-to-no no real knowledge is gained, and meanwhile it becomes easy to just move on and forget about the whole idea that seemed so exciting in a hypothetical context.
