The Gravity Slowdown Patent

I did not realize it was public. We could discuss the patent here…

Let me be clear; this patent came up first in a joke post demonstrating the chatgpt AI to make a business plan. But the patent is 100% Kitemill and 100% (well maybe 99%) serious

1 Like

A post was merged into an existing topic: The Pyramid Business Plan Comes to Life

Hi Tallak - I tried reading the patent application, but after several pages it still wasn’t saying anything, and I gave up. And the summary did not seem to mention any details either. Too much fine print to wade through. I was wondering if you could summarize the gist of this invention for us.(?) Thanks! :slight_smile:

Hi Doug,
I think that the gist of the invention is in its title:


The paragraphs 28-33 can bring some clear up about the purpose:

[0028] In light wind conditions, gravity induced speed change adds to the problem of keeping the kite airborne. This in turn increases the cut-in wind speed necessary for operation of the power plant, relative to a kite flying at substantially constant speed. This is shown in figure 2 . The cut-in wind speed of the uncompensated system is at approximately 10 m/s while the cut-in wind speed of the compensated systems compensated as disclosed herein is only around 6-7 m/s. This difference is expected to increase with scale.

[0029] If the kite is travelling faster relative to the nominal path, it should be depowered by reducing lift and/or adding drag to slow it down to allow it to obtain the speed according to the nominal path. Such a high speed may be affected by the kite flying in a flight direction component toward the ground (see also figs. 6 and 7 ).

[0030] The reason why the kite should slow down may be one or more of the following:
to protect the structural integrity of the kite
to protect the structural integrity of the tether
to protect the power electronics from high currents, high power, high temperatures etc.
to protect the tether from high current and/or temperature
to protect the winch from high torque, power or temperature

[0031] A kite flying in a flight direction having component away from the ground needs to counter act gravity to gain altitude. If no counter measures are taken, the kite will slow down. Being slowed down by gravity typically leads to less power being harvested from the surrounding wind. If the kite should be slowed down intentionally, this also causes less power to be harvested from the surrounding wind.

[0032] The invention aims to use a one or more of six measures to counteract gravity induced speed changes thereby indirectly reduce speed variation(s) of the kite during production.

[0033] The reduction of speed variation can be described in term of “instil” kinetic energy into the kite". Within the concept of instil kinetic energy is considered that the kinetic energy can be increased or decreased. That is, instil can also refer to removal kinetic energy since such a removal is instil with opposite sign.

Some means are envisaged. An interesting embodiment is provided:

[0038] When using direct thrust e.g. with propellers and/or RAT, the invention suggests in some embodiments adding energy storage on the kite to store energy harvested in the down stroke such that it might later provide thrust in the upstroke. The amount of energy stored in this manner may advantageously be a substantial portion of the change in gravitational potential energy between the kite at its highest point on the nominal path and its lowest point.

If we remember, Makani wing had a problem by going down at high speed, leading to high kinetic energy towards the ground (I mentioned it somewhere), then going up with difficulty and slowly, and even with the help of generators as motors.

The invention intends to overcome this issue, among other purposes. At least that’s what I think I understood after a first reading.

Hi Pierre: Thanks for the explanation, but I DO understand the issue (problem) the invention seeks to overcome. Anyone who saw the Makani videos could see “the problem”. (Which all the “smart people”, “modeling”, and “CFD studies” did not predict or prevent…) (???)
What was missing for me was the solution to the problem - the actual invention. We could all see “the problem”. What I wanted to understand was the “solution”. I guess powering the craft upward is an obvious step to take. Obviously, the energy required for that would reduce overall output. Not sure how storing energy onboard is relevant, since power is available from the tether. All I see this patent application doing is re-stating the problem, not outlining the solution. Since I don’t have the time or the patience to read any further in the text, I just gave up. I was hoping for a simple explanation of a few brief sentences as to what this supposed “invention” consists of. Such should be in the “summary of the invention” section. Not the problem the invention purports to solve, but an answer to the simple question “What is the invention?” Why drag it out? Why not just explain what it is immediately in the first paragraph? These freakin’ patents are all the same - they start out explaining background information, as though people reading an AWE patent need to have every simple fact in the surrounding world explained to the point that you can read page after page and never find what the invention even is. I give up. I can only spend so much time reading long-winded patents, especially when it looks like they are going nowhere anyway. :slight_smile:


To say it very briefly we are talking mainly about a combination between what Makani was doing to ensure constant flying speed and what Kitemill is doing for power production.

We could use a prop/turbine or winch reeling to the same effect.

The basis is anyways the anti-gravity winch (prop) controller which states that the reeling speed of the winch is given by an average reel out speed plus the additional speed needed to exactly match the added power in the winch to the power performed by gravity in flight.

We are using this to great effect at the moment. The anti-gravity winch controller is simple to implement and quite effective to maintain constant flying speed.

Also the thrust prop and turbine solution is a little bit farfetched at current scales (1-300 kW) but simulations show that this could largely compensate for square cube losses in kite mass, thus also compensate for its own weight. Overall this could allow scaling some factor bigger before hitting the wall.

I may share a bit more in time, though I was not aware the patent was public before just now. So I havent really though through what to do with it.

I can also add that Kitemill is not paying the upkeep for this patent so I guess it may be considered free for all to use

1 Like

So does that not constitute prior art and invalidate the patent? If Makini used the motors to maintain speed going up is that not exactly the same as what this patent claims is a novel idea?

It is more of a problem than a solution because the generators should not be used as motors: the wing must produce and convert energy, not consume it. I saw a problem for Makani, whereas the patent discussed here seems to present a solution for this problem, if I understood correctly.

You can also see some explanations on a previous comment and on the patent itself, particularly the Fig.4, Fig.5, and the Fig.6 which indicates: “Negative thrust applied moving downwards”; and the text [0023] page 4 about Figure 4, indicating:

Figure 4 schematically illustrates an embodiment of a kite for direct thrust control without a conducting tether featuring a RAT for negative thrust (power generation) and a motor and propeller for positive thrust (power consumption).

This problem (and the “band-aid” solutions) constitutes one more data point indicating the incomplete thinking going into today’s AWE concepts.

I dont think Makani disclosed the details of this, in any case the patent regards the algorithm itself.

I agree maybe the patent is hard to defend if Makani made good prior art. Also remember the patent may have been started before Makani went bankrupt. I dont know the details. Anyways, using both winch and propeller at the same time would be novel and also the most probable implementation, if you got that far

Yes and no. Maybe. Depends on how they were using the props. Anyways its a moot argument as the patent is not paid for and open to anyone to use.

Well I am not saying that it would be straighforward to implement though the black and white thinking («should not consume») is not very helpful in my opinion. You could consume some energy on the wing if that benefited the greater good. There would be some balance point where it no longer made sense to expend more energy on the wing. I think actually most AWE designs in existense would use a little power on the wing, we are just suggesting maybe we should use more. The bottleneck may be getting the energy to the ground, not extracting it from the air in the first place.

And I would be careful to call this a band-aid. Because it may extend the possibility envelope of AWE, and so making success more likely rather than being a sign that it is impossible to get to a working solution.

Maybe one reason you are so opposed to this is if you havent spent enough time to look at what happens with rigid wing AWE in its current forms when you scale to its biggest practical scale…

Well, I am not really to bothered if you dont «see the light» on this one. Its ok. We must all figure out for ourselves where this is heading, or wait and see

1 Like

Any time your wind energy system must stop producing power in a good wind is a red-flag, and any “solution” that does not eliminate the pause (interruption) (stoppage) (cessation) in output is “a band-aid”. It is the people using the band-aids that are not seeing things clearly.

What exactly are you referring to here? Yoyo return phase?

Yes, that, and what I thought you are talking about, using a reel to pump a kite(?), feeding power to props for the uphill trip like Makani(?) - none produce sustained, uninterrupted output. Every minute you are not generating, no energy is being produced, and you aren’t making any money with your machine in however many hours the wind event lasts. So that is a bad feature. Most every other energy source has constant output. I think I might not quite be understanding the reeling you are talking about, actually.

As you would initially be reeling out by 1/3 windspeed (super simplified though), which would be eg. 4 m/s at 12 m/s wind. Then, according to the patent you may reel out at 2 m/s to 6 m/s depending on the direction of flight of the kite.

You get some intermittency but on the other hand the average power output and cut-in wind speed is improved.

I think all companies in the «Yoyo» group already do this or will eventually.

1 Like

Ok. So it’s more just a public disclosure thing than a patent?

I think that is not the case as this would probably be «decorated» by some public announcement from Kitemill.

I don’t know why it turned out like this actually. I guess prioritization of existing patents Kitemill already maintain. Maybe related to which people taking decisions changing slightly over time. Maybe a lot like Google’s new management shutting down Makani.

Whatever the reason, release of the patent should only be a possible benefit for the other actors in the AWE sphere.

Personally I was only involved in writing the patent not so much in deciding what to do with it. I was not in favor of ending the upkeep payments on the patent, but it is very hard for me being deeply involved in the idea to have a balanced business view on a matter.

The search report of EP4071353A1 contains four “X” (particularly relevant if taken alone) of which EP3334928B1 from also Kitemill and including a common figure (Fig.1 for EP4071353A1 and Fig.1A for EP3334928B1).

Thanks Tallak. Just for clarification, at which point in the rotation (up or down) would the reel-out speed be 2 m/s vs 6 m/s?