A crosswind rigid flygen wing seems to be the most appropriate AWES for several reasons:

  • Flygen system is a natural design similar to the known design for planes with propellers.

  • Generators onboard are very light thanks to the high rotation speed and allow also take-off operation.The weight of Makani’ (flygen) and Ampyx’ (yoyo reeling) wings is similar for a given power. And the weight theoretically does not impact performance as shown on Flygen.

  • Flygen systems deliver a continuous power at high efficiency (no downwind swept area, no return phase) as shown on (3’15" from the beginning), and in the same time sweep a large area.

  • The most advanced AWES prototype for electricity production is Makani’s M600.

  • The maximization of the space can be achieved using several means, the main idea being sharing the swept disk to achieve a high level enough in Betz limit, taking account of safety requirements.

  • The research and development can be coupled with that of the electric plane like

When the flygen method will be selected as the probable AWES, companies will be focused on better flygen designs, accelerating possible implementation, that instead of scatter in directions leading most of the time to dead ends.

If it is true, the question would be if is it possible to do as well with a ground-based wind turbine. I think perhaps yes, by using the same method, putting light secondary turbines, avoiding a too massive generator as the wind turbine scales up. The weight of the flygen wing and the blades could be similar.

So we have a complex automated control, a higher land use due to the elevation angle of the tether, so difficult or not possible secondary use on a large area, or the requirement to implement AWES above forests or offshore or in deserts, all that against the mast and the heavier and less useful central part of the rotor. AWES could become a serious possibility.


Kite Scaling Laws and Aviation Regulations put severe limits on how much generator mass is practical. How big a Flygen do you predict is workable? The M600 is severely burdened to carry its mass and make high power in most-probable wind velocities. They are not proud of their tested power-curve, or they would share it.

kPower instead proposes the world’s largest existing generators, at GW scale, to be driven as Groundgens by power kite networks. This avoids Flygen mass scaling limits to exploit Utility Plant economy-of-scale and capital-legacy advantage.

Flygens work great up to about 5kW before issues like scaling laws, failure modes, safety factors, become critical. A formal aerospace scoring matrix would help better weigh positive against negative factors. The electrical tether is also problematic. Full M600 data made public would quickly settle all doubts.

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Really? How?

Scaling laws and aviation regulations are two different concerns.

M600 is far to be perfect but is the most advanced AWES for electricity production. As I mentioned several times (Flygen) some studies show there is no impact of the flying mass when the flygen method is used. Moreover the generators onboard are light thanks to the high apparent wind speed.

With scaling laws we have the A 380. And soft wings are also impacted with scaling laws: Is the modern Power Kite the answer to Kite Power?.

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Read Old Forum posts on how kite-driven cableways can be matched to existing generators.

Aviation regulations reflect scaling laws by accounting for mass and velocity. These are not “two different concerns”, but two views of the same physics.

M600 is “most advanced” only to anyone who thinks Google does advanced aerospace. Its at best an advanced failure, by Fort Felker’s own 2010 criteria.

It is not even sure that a rigid wing is heavier than a soft wing for the same power.

I am. A soft wing more efficiently distributes loads, so its easier to maintain max working load. The rigid wing also carries resin mass for compressive structure, and many extras, like maybe even back-up parachutes (DamonL, Makani).

It would be nice if you had followed this on the Old Forum, to no be so unsure still. At least consider the latest 1kg paraglider. A rigid glider must weigh far more for comparable power performance.

For about 20 m² and a use during about one month. Consider scaling-laws for a soft kite that are explained on Is the modern Power Kite the answer to Kite Power? :

13.5 tons for 900 m². Starting with the 1 kg paraglider would perhaps lead to a lower mass, but not so lower than that of a rigid wing for the same power.

It would be nice if you had listened @dougselsam’s explains about soft wings that are in the old forum.

Yes, add flygen mass to your rigid wing too.

Try and wear out a parglider in a month then.

Please quote Doug on soft wings. I have missed any expertise on that subject he may have.

As I mentioned it is a relatively low mass. And It doesn’t impact efficiency in flight operation. Please read the paper I mention on Flygen.

24 hrs/24 in crosswind kite with all wind conditions, perhaps less than one month without incidents. 720 hrs is more than paraglider’s lifetime of 500 hrs.

Doug wrote about soft wing as an inappropriate mean for electric energy production on the old forum since years. As he invents and built several SuperTurbine ™ that work, he can be seen as an expert in wind energy.

At HAWPcon09, the ST was seen to barely reach 15m altitude. A tower is better at that height. The Danes of Vestas are top real conventional wind experts who were not held back by “wind cranks”. My conventional wind expert top pick is Coy Harris, founder of the American Wind Power Museum, because he personally maintains and operates about a hundred different wind turbines, from a classic wooden post-mill to a modern megawatt HAWT, and everything in-between. Coy has a Dan Tracy Flygen, which flies far higher than any ST ever has, so Coy’s now into AWE as well.

Try to wear out a power kite, it takes a long time if you fly it properly. Power kites cover “all conditions” ideally with a quiver of kites. No single wing, soft or rigid, beats a soft quiver.

A concern with a heavy rigid flygen device is the power consumption due to take-off and landing operations that occur often because of its high cut-in speed. And the high expense in helicopter mode multiplies the global power consumption.

The problem is mentioned on

If Makani needs to VTOL to 400 m altitude and mass is 500 kg (just a wild guess), E=mgh gives us energy 1.9 MJ. This energy is recovered at 600 kW in 4 seconds. Even if you waste 10x, and produce 0.1x, you are still only using 6 minutes to recover the energy from a launch. I would not expect you to need to launch and land more than a few times a day at most sites.

See the example of Lilium on the tables 9, 11 and 12. Lilium weight is 490 kg. Total energy for take-off, landing, acceleration, deceleration: 5.1 kWh, so 18.36 MJ.

Makani M600 weight is one ton. By extrapolating the energy expense could be about 40 MJ (+ energy connected to the time for tether winding and unwinding) each time the wind speed is below the cut-in speed (5 or 6 m/s). And 600 kW would be a presumed power peak, considering a L/D ratio above 10, and for the rated wind speed.
A deeper study is needed to know the real power consumption as an underestimation of the cut-in speed potentially = crash. And for a day with an average wind speed of 7 m/s, some lower winds due to variations can occur numerous times.

I think you would not necessarily have to land all the time, as the kite probably flies in windspeeds that are not commercially profitable… Say minimum flight wind was 6 m/s but you did not produce much power before 9 m/s, you could wait for landing until the wind was 6 m/s, but you did not have to launch unless the wind was exceeding 9 m/s.

Given the cost of launching and landing, you could calculate the profitability of a certain rig at a certain site. I believe this might probably have been done?

9 m/s is also the full rated power wind speed as specified on
This low value can be due to the required TSR limit of the secondary turbines, assuming 600 kW can be reached with a L/D ratio being about 15.
And what about the M5 with its 10 tons?
And also takeoff and landings are the least problem while the wing is scaled…

FlygenKite (at 8:00) is the only one AWES I conceived and built and which flew while generating energy. At the time I was stopped by the impossibility of having a perfect smoothing to recharge computers. But this design contains potentials that I have not yet explored. Indeed the two stretched lines can be seen as structural elements allowing to settle complementary structure(s). A first example is given by the initial bar carrying the turbine(s) and which is supported by the two stretched lines.