On the process of figuring out if AWE is commercially viable

We default to AWE not being commercialy viable, as today there exists no commercially interesting AWE. There may be some possible exceptions that we will not consider, this is more on a philosophical level.

A potential for commercial viability was shown many years ago, eg in the paper by Miles Loyd — «the holy grail»

Now if someone wants to tap into that potential, one must navigate the limitations that exist. These may be handling, tether drag, cost, gravity, robustness, technological complexity, aeroelasticity and so on.

If Alice puts forth an idea to find «the holy grail», it does provide some value for others to point to known limitations that will make that plan impossible or difficult to achieve. Eg. «the leading edge will not endure the beating from dust in the air». Alice may or may not have considered these limitation. But if Alice thinks such limitations are possible to overcome, it is fair to not tackle these immediately, and rather focus on riskier elements of the plan. Such feedback is very valuable though.

Also, Alice must expect to meet unexpected limitations once learning more, and these may or may not be showstoppers. This is the process of learning and exploration. Looking back at the previous paragraph, it is better to learn from other´s experience rather than making your own experiences. As a community we must respect that we are at different points in our learning and exploration process, and also that we arrived at different conclusions on the way.

On the other hand, it does not provide any value to make sweeping and vague negative comments as a proof that a certain venture is infeasible. Like: «Makani proved that flygen is not possible, because …». People presenting such claims I consider «naysayers» that do not believe in «the holy grail», or who are content with defaulting to AWE not being viable. These type of claims are just wasted time and provide negative value to the discussion. The feedback may refer to AWE in general, or just a part of AWE research, such as saying rigid wing AWE is impossible while soft wing AWE is possible.

Now I want to change focus to Makani, and what seems to be the reason that they crashed in the North Sea.

First a recap: When landing in VTOL, the nose was pointing more or less towards up, or even slightly away from the buoy. The kite started to roll, eventually leading to loss of control of the kite. The tether was the only means of stabilizing the kite in roll during VTOL. A contributing reason was lack of stabilizing moment in roll as the tether was facing mostly along the fuselage, and at the same time, the buoy motion interfered with the tether tension.

I believe this crash may have had significant impact on Makanis demise (pure guesswork though). I therefore make the claim that a reason that Makani failed was their inability to foresee this limitation. For someone to succeed in AWE i think it is of utmost importance that the team are able to identify and work around most limitations before they are discovered in flight.

It seems the Makani team either did not believe lack of stabilizing roll moment this would be a real limitation, or they did not see it coming. Either way, the failure was not in the design, rather the inability to remedy this at an earlier point.

I am not saying that @dougselsam agrees with me on this, but I think my conclusions are along the same lines as his. My conclusions on Makani and probably a few others in the AWE industry would be along the lines of: «You know nothing John Snow»

How can this be remedied? The only thing I can think of is having the right talent at the right place. It seems though Makani made an impressive presentation, they were still not sufficiently refined in their concept. No doubt AWE is either difficult or impossible to commercialize in 2020. Perhaps those with the required talent quickly end up in the «naysayers» camp and focus their energy elsewhere. Perhaps someone will eventually make it happen.


As a conclusion (from for example Mike Barnard) it could be stated that AWE is not reliable, not efficient, so not viable.

As an opposite conclusion (from M. Loyd’s paper) it could be stated that AWE is efficient, so viable (other issues such as reliability and power versus space used being set aside).

I think we are far from making a marketable utility scale AWE. But that doesn’t mean it couldn’t happen.

The evaluation of AWE viability can be based on inherent and circumstantial factual elements with all the nuances in between because one does not know what is only inherent or only circumstantial. A software could be elaborated in order to facilitate the choices among AWE methods, then among technologies, without forgetting the characteristics of the chosen site, then the favored hypotheses. Then iterations would lead to definite better what remains inherent, what remains circumstantial, with all the possible degrees of evaluation as well as the possibility of bridges between these two categories. During investigations and testing a technical issue which could be solved according to reasonable hypotheses would go from inherent category to circumstantial category, increasing the possibility of a viable AWE.

Let us take Makani as an example of a leading AWE company. So as we can notice Makani’s failure (both crashes and no efficiency), we still cannot tell the part of what is inherent within the failure, then what hypothesis of improvement can be favored: weight in flight, higher kinetic energy downwards due to both weight and speed during large loops, Y-bridle tether connection not preventing destructive roll…

That said a significant element is what Makani or another company claimed and what (high) echo the AWE community in general accorded to their claims. Unfulfilled promises are not an element of credibility for AWE. So we should stop talking about marketing or claiming AWE as the future of wind energy (compare with what is really happening in marketed wind power) for a given year…

That’s quite a wandering post. And I’m not sure the title reflects the post. Maybe change the title a bit if you agree?

Reacting to the title, viable is context dependent. I don’t think any AWES is viable 30 years from now if a series of black swan events has made energy effectively free and ubiquitous.

AWE makes the discussion too broad to be of use. Only a few of the possible architectures have or are being developed, haltingly, to some degree. It’s an impossible task to prove a negative here – a single (unknown) positive example could prove the positive – , in the context of the 2020 markets, unless the context changes so much from the introduction of a new technology so that all other technologies are made obsolete.

Pretty sure
Makani folk had lost roll control in hover before the dook into the North Sea.
This was a known problem.
This problem would ideally be remedied in smaller less expensive models. See KiteKRAFT.

Makani took a lot of risks because they were being pushed too hard.
The problem here was (opinion) the deadlines imposed by investment.
This wasn’t a pure science. That would have taken too long.

This was rushed engineering which was devoid of the creative design phase.

A proper design process could have avoided this.

Is this too positive and naive an opinion to help AWES development? Maybe.

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Sometimes when you see something you decide to deal with it or just hope you will get by.

I also saw an earlier video with the problem. They had a warning. But yes, perhaps business pressure kept them from having an option to deal with this?

I dont believe in a pure scientific approach to solving this. It has to be science combined with some business pressure. If Makani had had more time, or seen this coming earlier… they may have made it further…

I agree @tallakt without pressure for commercial viability there won’t be investment.
To protect money.

Hope, however, is not a good strategy.
I thought X was all about owning and celebrating mistakes.
They may have needed to remove the straight-jacket business suit and Play with design more.

Commercial viability within low energy prices means we need large autonomous systems.

There is still a lot of scope to mess n mix designs up within these constraints… I suspect there is more chance of success on a more creative path.

Can a single rigid VTOL AWES be large enough? Would it work better in multi kite configurations or be networked?

Can we ask similar questions of AWES with glider prop launched rigid wings?
Is a circular runway needed for launching sets of these?

I have my own bonkers sets of questions
Please someone else answer.
Can you drop deploy a Daisy kite Network Turbine so it inflates on the way down?
You can drone drop deploy a lifter.

Autonomy of soft kite handling is a challenge I don’t think anyone has fully decided on.

Even the simple act of collecting / recapturing a lift kite
I don’t remember seeing a simple lifter winched down into a bridle choke ring. (Must have happened on yachts for deck space.)

To counter my argument
Skysails have done well
They took simple steps, a relatively simple redesign of the kite, a simple controller, a relatively straight forward mast capture.
However, The system seems limited to a few hundred kW. Still bloody useful.

I’d have to redo their mast before being able to use it for a kite turbine lifter.

Talking of mixing up design
A kite powered and controlled from a tail mounted device set so the main bridles can be winched straight into a fairlead. Haven’t seen one of those.

Or still on kite recovery handling…
If a lifter gets power from a frontal turbine like kiwione with controller… can the axis of the turbine be clamped to a winch before the controller pod is pulled down with bridles and power line into a choke ?

Here’s a couple quick sketch ideas (more fancy stuff not shared just yet) on how lifters and kite turbines can cooperate with recapture, action and launch.

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We require some creative thinking to establish the viability of AWE. Most designs are handled like a tethered aircraft which must be launched, operated and landed automatically. This is more critical than something like a self driving car since if things go wrong you can’t just stop the aircraft as you can in a car. The essence of the problem is how do we automatically and repeatedly launch and land a kite without human intervention? My concept is to restrain the kite from moving in any direction except up and down the line of the tether. This is achieved by attaching diagonal stays to the corners of the kite. If the wind dies down, the tension in the tether drops to zero and this must be compensated for by rapid retraction of the tether, which is equivalent to generating the force of wind on the kite. During retraction, the length of the diagonal stays must continuously be adjusted, so that the kite is restrained at all elevations. Retraction must also be performed if the winds are too strong (high tether tension) or there are changes in the wind direction.
I know that it will be difficult to operate a restrained kite in crosswind mode but isn’t it more important to develop a reliable automatic device which is relatively safe. We will already be able to operate in stronger and more consistant winds with a device a fraction of the weight of a conventional HAWT and with easily replaceable components.

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The design below is not new but its implementation looks to be easier. It is a little between Sky WindPower and Makani with its secondary turbines which are also used for take-off. The only control for all flight operations is for the angle of attack, the rest being dedicated to meteorological data analysis. Sure it cannot scale too much. But testing easier systems can be a part of the process of figuring out if AWE is commercially viable.

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Flygen is a part of AWE research, in a similar way as the choice between soft and rigid wing AWE. Moreover AWE is not a religion, so "do not believe in the “holy grail” is not (more) an issue. By the same I refute qualifiers such as “positive” or “negative”, preferring “true” or “wrong” terms because “positive” or “negative” concepts imply an attitude of appreciation in regard to the concerned field which one should adhere to from the outset.

I am surprised that this topic is about the process of figuring out if AWE is commercially viable by mainly evoking Makani’s journey ending to a serious failure concerning reliability and efficiency, while their conditions of work were exceptional.

I mentioned a possible method to try to determine what is inherent (with low possibility of improvement) and what is circumstantial. Y-bridle tether connection might have caused a problem of roll leading to crashes and lower efficiency, but inherent causes can be envisaged, such like the weight in flight (see the curves with 10 m/s then 12 m/s wind speed, and also the good curve of a previous smaller wing).

After all telling that «Makani proved that flygen is not possible, because …» would be more positive that stating «Makani proved that AWE is not possible, because …», although not more true because if we take a perspective on global renewable energy financing, the halt in AWE funding can be quite positive. That could be the trend after Makani’s experience.

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I was referring to the nature of the argument. Let me present two arguments:

  • (a) Makani have shown that flygen AWE with a rigid wing is not possible.
  • (b) Dust in the air will erode the leading edge of the kite, making it unusable after year’s worth of use

I believe (a) provides negative value (taking value out of the discussion) while (b) is good input. (a) cannot be countered in a discussion because it is vague and also it is not possible to disprove a method using this kind of argumentation.

My reference to «the holy grail» does not refer at all to religion. I just state that a lot of people I have met do not believe any AWE is possible to implement, then they try to find reasons to support that. Because we are already defaulting to AWE not being possible, this also doesnt add value. Right now, only methods to actually untap the potential of AWE makes sense.

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But the previous similar argument in the form was:

because…” leads to a possible argument which could modify a) in b).

That said all these nuances, these assumptions, these observations should be categorized and potentially transformed because of the complexity of the AWE domain. So we can agree on a method.

@PierreB It seems you would like a computation of AWES

inherent and circumstantial factual elements

So back in 2015 I went through this exercise and published an AWE System scoring matrix

These criteria were weighted
Build and installation Cost
Design and development cost
Power scaling
Control Cost
Time to market
IP maintenance
Windspeed range
Generation surface efficiency
Land use efficiency
Stack arrayable in the air
Drone field management
O&M cost
Generator height demand

Somewhat vague notions and hard to quantify

Criteria Definition
Build and installation Cost As a product how expensive will this option likely be per investment? (ROI)
Design and development cost How expensive will this product be to develop to TRL9?
Safety Once installed, How many different dangerous failure modes will still exist?
Power scaling Does this architecture have mass scale limitations?
Reliability Is there a likelihood of catastrophic failure?
Control Cost Will the system fly itself or does it need complex control and optimisation?
Time to market How many years until public and product are ready for each other?
IP maintenance Is FAA certification standard easily atainable and open to public optimisation?
Windspeed range What is the cut in speed and can it keep generating in a hurricane?
Generation surface efficiency Can the system develop to hard fast efficient blade surfaces or does it have to be flappy cloth?
Land use efficiency How much land do you need per kwh?
Stack arrayable in the air Can you stack and pack the turbines high into multiple working altitudes?
Drone field management Can field operations be handled automatically or will it need expensive human workforce?
O&M cost How intense are the operation and maintenance costs likely to be?
Generator height demand Does the architecture use energy to lift the generator?

By my reckoning then the Makani architecture scored worst in the set of AWES technologies.
The overall scoring mix did not stay consistent with my current view.
However the criteria are still interesting when considering if AWE is commercially viable.

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These information will be likely modified during the process of R&D from the idea to the complete prototype. So that can be only hypotheses as a start, then verified statements after some level of testing or/and simulation.

In the meantime, said initial information will have changed or even be reversed. Software could facilitate the detail of all these transformations (information content during the transition from hypotheses to verified statements).

I’d be fascinated to meet the folks with the software capable of recording and balancing the complexity of concepts as diverse as those listed above and mixing this with evaluation calculations from kite theory and practice. Once we talk to GPT3 enough maybe.

The software would work in stages and as an auxiliary for the developer.

As far as new investors are concerned, I am afraid that Makani’s experience will take precedence over everything else, except perhaps for crowdfunding.

For all the people who think blades pushing propellers is the best way to do wind energy, it is interesting that nobody ever bothers to try building even one (1) simple tower-mounted wind turbine using blade-tip-mounted secondary rotors as a power extraction method. Why is that? Is it a good idea or not? Could it be that when isolated from exterior complicating hype factors, the rotor-tip-rotor idea does not seem even worthwhile to pursue, on its face?

Images from my first wind energy patent:

I agree with most of what Tallak is saying in his post, but I would distinguish between whether anyone has produced a viable AWE method, versus whether the concept of AWE is a viable concept.


OK I think we need to distinguish between what caused a single crash and what caused the demise of Makani as a company. In my opinion, and I think others as well, there were many signs that Makani was never “firing on all cylinders” in the first place. The fact that a single lame-ass crash was the end of the company just shows that the whole thing was a facade all along. With all that funding, after that many years, why should a single crash kill the whole company? Answer: because all they had accomplished, in all those years, with all that money, and all that supposed “talent” was a single oversized-for-its-level-of-development prototype, that was seldom flown, lest they damage their impressive “work of art”, best kept hanging from the ceiling in a museum if a crash would kill the company. Then you have the simple fact that if such a single crash could kill the company, why were they flying it in the North Sea? I think the answers are obvious: The North Sea flight was a symbolic “hail-Mary” last-ditch effort to gain a foothold on a new symbolic ledge, from which they may have dragged things out for a few more years before officially throwing in the towel. It had become obvious years previously that their forward-looking statements of powering the grid in the 50th state were meaningless and never close to happening. It was obvious that they really didn’t have much true faith in what they were doing because if they were serious about it, they would have had many operational units, of various sizes by that time, with ongoing experimental daily operation at various scales, whereby the crash of any one unit would not even be worth mentioning. Not even newsworthy. Nobody would expect to advance in a field like AWE without many crashes. To me, it was easy to see many years ago that Makani had lost faith in what they were doing. Right about the time they hired Fort Felker away from the NWTC, I could see they had already just about given up. I think that crash was just really the excuse they needed to officially abandon the effort. Fort’s real role may have been to give them the bad news that they didn’t really know what they were doing. Meanwhile I do not see that some version of the general concept could not work. They did not prove the concept doesn’t work, they just proved that they were unable to sufficiently advance or develop the overall concept. Some version they never hit upon might work great!
And I do not think anyone’s naysaying on some chat group is worth over-analyzing. people have a right to their opinions, and anyone who knows what they are doing will not care. Any idea, person, or team that gets attention will always find detractive comments. Ask any famous person - someone is always pointing out detractive points, Often they are correct. If you look at my observations over the years, assuming you could still dig them up, most have turned out to be accurate. Doesn’t stop anyone from accomplishing what they know will work.

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Thats some interesting thoughts:

  • Why did they not run the smaller units 24/7 while building the larger units. One should think hiring, say five operators, and building 20 clones, should keep them running for a long time at low cost.

  • At what point did the central thinkers at Makani lose faith in their project, if they did, and how long after that did they continue.

It does seem now in hindsight that more offshore testing could have been done with smaller teams using smaller kites using less resources before the M600 was deployed.

I guess these questions may remain only speculation even after having read the abundant documentation left behind by Makani.