KiteGen Research High Altitude Wind Generation...

As usual AI = narrow AI = Software.^^

Yeah terribly sad to miss the potential scope of the statement. A true AI (ever remodeling, flexibly learning and x referencing (can you tell I’m an outsider really))… A true AI AWES would significantly weaponise the war on carbon energy

and everything else, including actual war.

@Massimo posted the following interesting message on Yahoo AWE forum:
"Tether Drag doesn’t affect the wing speed or the system AE.

The reasons are quite easy to figure out:

During the tests, we pushed a wing at 2400m and 65m/s observing no tether drag issues. This demonstrates KiteGen’s right to reject the overly simplistic analysis based on the “system drag” idea that combines rope and wing, which appeared for the first time in the Loyd patent, the validity of which is limited to tethered aircraft (A) equipped with a tail that drives and forces the pitch.

Thanks to in-depth research and simulation, it has been established that the drag of the rope is irrelevant to wing speed and energy production. It is, instead, simply a geometric dynamic, conceptually affecting the path in airspace only (B). Tether drag only limits the crosswind motion distance that can be achieved in one stroke, before the wing has to change direction. This is a feature that could be successfully exploited by the control in order to extend the wind power spot.

Issues related to transverse wave propagation on the rope. The wing is typically set to fly at 80 m/s. When the wing changes direction, a new displacement transverse wave acts upon the rope, while the axial wave is running at 270 m/s. Such a transverse wave is slow, due the air mass added to the rope’s linear density, taking several seconds to affect the entire rope. Thus, the wing has the freedom to fly for a few hundred meters before the rope bending will change its optimal angle toward the wind. The models adopted in literature expose an excessively tight time boundary or even a snapshot to track such behavior.

Rope drag is applied axially to the wing, the same effect that gravity has on gliders, that obviously never slows the aircraft. The force vector representing the drag of the ropes binding the wing is only manifested axially, thus thrusting the wing as with gliders. (above picture B case)

As Gustav Eiffel taught us, the Reynold number of the segment of rope near the wing reaches a high value where a new effect called the “drag crisis” takes place, greatly reducing it.

The tether drag issue is speculation based on a fixed cylinder in a flow experiment setup, with a measured coefficient ranging between 1.2 and 1.5. The ropes are light in specific weight which means they are locally free to oscillate and rotate on the axis, dynamically losing air pressure accumulation, thus they cannot be compared to a typical fixed cylinder in a flow.

Larger scales create a lessening of the significance of the issue; this due to the rope section and Reynolds surface ratio, rope section is squared function of the diametre and the drag surface is linear, an advantage that grows dramatically with increasing scale.

The scientific committee of KiteGen published an article trying to explain the limits and errors of the proposed models in the literature review, unfortunately no skilled audience.

Furthermore, in order to gain more flight freedom, KiteGen patented ropes that were appropriately tapered in order to reduce the drag coefficient to 0.03, instead of the classic 1.2 of a cylinder immersed in a fluid that the ropes are immersed in as well. This patent applies to the domain of possible and potential future enhanced optimization of the technology.

To repeat, as this is an extremely important concept, because the production of energy depends on the square of the flight speed, the drag of the ropes is not added to that of the wing, which remains free to fly at the speed of its glide factor or aerodynamic efficiency."

For me it is quite new. Thanks for your observations.

1 Like

Posting by Massimo from kitegen - Interactive Commentary on " Improving mid-altitude mesoscale wind speed forecasts using LiDAR-based observation nudging for Airborne Wind Energy Systems "

1 Like

Hi @Massimo could you precise some point on page 14. For example with a machine’s diameter of 1.13 km, the rotor, the stator, the electromechanics weights are given for respectively 5000 tons, 7500 tons, and 200 tons. Please what is the expected weight of the structure supporting them, onshore, offshore? Thanks.

http://www.kitegen.com/pdf/dossierkitegenen.pdf

I would add that 50 MW/12500 tons rotor and stator lead to 1 MW/250 tons. So this generator looks to be very heavy compared to current wind turbines or other AWE planned generators. Adding the structure to support it. The involved costs could brake or even stop carousel development or direct it towards other solutions.

And they still could not figure out that BOW kites (where the second generation had been on the kite surfing market for over 5 years already at that point) is more efficient than C kites…

I don’t know what they are doing now, I couldn’t find any info or video of their system in operation when I looked into that a while ago, but this - completely depowering the kite to reel it in by shortening one line compared to the other - doesn’t seem possible to do with a bow kite, although it looks sketchy to me regardless so maybe they’ve abandoned that: https://youtu.be/0y-KGi8g94c?t=443 (at the 7:23 minute mark.)

Yes Pierre I somehow got sucked into that discussion on Linked-in too. I advised Massimo that I did not realize they were that far along and they should consider a building a smaller version. He said something about too many forces trying to hold back their technology and prevent them from moving forward.
This is very typical for efforts to develop new types of wind turbine.
There is always this push to build things way way way bigger than a proof of concept would require. To me, it’s a convenient excuse, to conveniently not do anything. It seems to me that if any team with a lot of funding really believed in their concepts, they would jump at the chance to build a small one, which would then work so well that world would demand a larger one.
For people who say they want to replace hardware with software, well, go ahead - what’s stopping you? Build at a scale you can manage easily and prove your concept at a scale you can achieve. This whole drama has been going on for so many years now. Oh well, same old thing, different day… :slight_smile:

Yes seems really risky to just flag out the kite and hope it is pulled in fast enough that it does not just fall to the ground and that it starts flying again when it reaches the bottom of the pull in phase and they tighten up the other lines again. But i guess they would have to do something like that because the depower range is so small on a C-kite. So really just another point in favor of a BOW kite with its much larger depower range while it is still flying.

1 Like

Yep, and when the tension comes back on the winch which was looser in retraction…
As @Windy_Skies was looking at yesterday … that’s gonna pinch, wriggle, twist, mangle, bite, snarl and generally go bye bye

1 Like

Hi Doug, I have just seen a comment from Massimo. The beginning of this comment:

My experience is the opposite, KiteGen fully designed and industrialized both the ground machines and the wings. No more research or experimental activity is required. The energy conversion is hundred times cheaper than a wind turbine.

With such ideas you cannot fail…to fail. That said, KiteGen has the merit of seeking to exploit as wide a frontal sweep area as possible of the powerful high altitude winds. This is where KiteGen stands out. A small prototype could be made.

About KiteGen:

I like those guys from Italy - they’ve even stopped by here for a visit, and we all had fun.
But statements like “a hundred times cheaper than a wind turbine” point toward a departure from reality.
If they have something to run, run it! :slight_smile:

1 Like

Do you think anyone is going to want to build a carousel 1 km or more in diameter?

I made one 1 m in diameter, driven by a tilted rotor, and called a rotating reel. It doesn’t spin well. Things are far better when the carousel and the rotor are parallel (examples Daisy or The Pyramid).

http://www.kitegen.com/pdf/IEEECSM200712.pdf

An extract page 2:

The KiteGen project has designed and simulated a small-scale prototype (see Figure 2). The two kite lines are rolled around two drums and linked to two electric drives, which are fixed to the ground. The flight of the kite is controlled by regulating the pulling force on each line. Energy is collected when the wind force on the kite unrolls the lines, and the electric drives act as generators due to the rotation of the drums. When the maximal line length of about 300 m is reached, the drives act as motors to recover the kite, spending a small percentage (about 12%, see the “Simulation Results” section for details) of the previously generated energy [4]. This yo-yo configuration is under the control of the kite steering unit (KSU, see Figure 3), which includes the electric drives (for a total power of 40 kW), the drums, and all of the hardware needed to control a single kite. The aims of the prototype are to demonstrate the ability to control the flight of a single kite, to produce a significant amount of energy, and to verify the energy production levels predicted in simulation studies.

A video of KiteGen Kite Steering Unit (KSU):

Hello @ChristianH , do you think if we can transform the KiteGen Kite Steering Unit (KSU) into a OKE Precision Winch "Reel and Rotate" Technology?

1 Like

This two line system has tremendous control, you can see the power in the system by the responsiveness of the kite. The OKE actually does not possess a right line control winch in the nacelle, The purpose of the OKE is primarily to facilitate the rotation of the left line (orbital line) around the tether line (right line). A secondary feature is that it has independent reeling and depower functions.

To answer your question Pierre, an OKE would control the left and depower lines in the KiteGen system shown above, The right line would pass through the center of the OKE and connect KiteGen’s winch to the kite.

The addition of an OKE would allow the KiteGen system to perform any maneuver a two line kite can produce without twisting the line. Control engineers would really enjoy plotting efficient flight paths irrespective of line twisting.

Is it not rather “around the tether line ([right or fixed] line)”?

Does this also cause the orbital line winch to rotate around the fixed line winch?