And this is yet a very optimistic first assessment. You rightly mention:“The “fall-land area” is much larger than the disk of radius of length of the energy-kite system (AWES). Why? Breakaway wing sets with tethers could fall/drag for tens of kilometers and more”.
But most of all the area of 3000 meters x 1000 meters height that was granted by the Norwegian CAA to Kitemill is irrefutable proof of the land and space use problem and confirms what I am telling for years. The Norwegian CAA unterstands it but not AWE players. And the issue is similar whether for the no-fly zone, and the land area. It’s obvious.
I think it is not possible due to the tethers, particularly for crosswind AWES. It would perhaps be possible for small static AWES flying at a high elevation angle. So It must be admitted that a reserved space is essential, and therefore think of maximizing it, using the Power to space use ratio instead of the power/kite area ratio.
You need two pieces of information to be able to analyze the risk, for yoyo systems say: current and historic (1) wind shear and the ability of your system to (2) stay within their respective cones, even with wind shear.
We don’t know (1) and (2) is unknowable even for current employees at a company for future products, let alone outsiders.
We do know that (2) is probably absent for small static systems so you’d have to rely on more distance and smaller wind shear for those systems and you perhaps won’t be able to control their landing as accurately when they fail.
Someone interested in this problem could try to get accurate data on wind shear for a site and the size of the cones for different present and future systems and based on that information try to work out the spacing needed to limit landing due to wind shear below different percentages.
They could also try to work out solutions for when a system does fail, because [b]reakaway wing sets with tethers could fall/drag for tens of kilometers and more is a worst case scenario that could be eliminated just by detaching the tether from the kite for example. If you want that’s a case against using fabric kites as well.
The first safety measure would be to move the secondary use areas away from the place of energy extraction. The total area covered by AWES and comprising the tethers is a minimum. And I don’t think regulatory requirement authorities rules would do it on a case-by-case basis. Be realistic a minimum.
Crosswind AWES faces hazards of many sorts (mechanic, computer failures, weather…) for one rigid or even soft kite moving fast with its long tether. As a consequence dealing with these risks is not possible.
Things become yet worse if a kite-farm is implemented, due to wind shear added to other risks, requiring far more spacing that spacing sketched in publications in which the authors confuse the natural wind with a wind tunnel.
For small static systems the consequences would be lesser. A 100 watt static AWES flying at a high elevation angle of 60° is infinitely less dangerous than a crosswind kite of only 2000 W at the end of its highly tensioned 300 m rope and flying at high speed at a low angle of elevation of about 30°.
As a result the AWES area should be reserved and exclusive (no inhabitant, no secondary use as for an airport) for all crosswind kites, alone or within a farm, rigid or flexible. The only solution is to maximize the area so that the energy produced compensates for the blockage.
For another risk such like wing sets with tethers dragging for tens kilometers, thus largely leaving the reserved and exclusive area, it is another concern linked to the conception (and not only an uncertain tinkering in order to detach “the tether from the kite”) of the AWES.
IMHO the Danger zone should cover all the ground zone as a minimum, likely more. The kites should be spaced more, by at least a tether length, in order to mitigate unforeseen events such as wind shears.
Then some strategies allowing to maximize more the space occupied should be studied in order to increase the frontal airspace swept by the kite(s), such like Low radius loop or Vertical trajectory for yo-yo AWES? to stay in neighboring architectures. Other architectures like @Rodread’s Daisy network seem to have the potential to respond favorably to this major security and credibility issue and which is quantifiable by the Power to space use ratio.
Sure. But like I say because they probably have nil capability to deal with wind shear they’ll probably need to be spaced further apart if you want to maximize uptime and if you’ve determined wind shear is a problem at your site. They’re also largely irrelevant.
Unless you describe these risks better in your quantitative analysis a response to your concerns is not possible. You point out a potential problem, you don’t analyze the problem, you give an unimaginative solution to the problem, and then claim because your unimaginative solution probably won’t work dealing with these risks is not possible. That’s the exact wrong way to deal with any problem. That you can’t imagine a solution to a problem doesn’t mean that no one else can either.
You’re using the exact wrong framework to try to understand the issue. This one is better for example:
I let my kids play underneath my kite turbines, but even they aren’t stupid enough to go under a fast & powered up, rigid blade, kite turbine.
There will be no other land use permitted under early model AWES used for permanent utility.
Let’s clarify about kite networks in this thread.
Kite networks undoubtedly make kite operations safer. Have no delusions here.
Kite networks stabilise kite motion by using wide tethering to limit the available flight path. That is a thing.
Kite networks enable redundant safety and control via back-lines, side-lines and multiple tethers.
Breakage of an airborne component in a kite network almost always depletes the capacity of the kite network to perform high energy aerobatics.
This is what I have used previously used to ask event organisers for as an excluision for running a kite turbine. On it’s own in a field it would require a 28m radius
That covers a good start toward safety improvement. I should think you all agree. I’m very keen to hear comments.
Next onto density of energy production 28m radius as mentioned above is a lot for a small 1.5kW turbine demonstration. This is early days. This is a parametrically reconfigurable network turbine.
It’s going to improve.
But here we can see an idea of a ground area covered in a volume of kite generation.
Before anyone says, … Yes, this is designed to take wind from any direction.
Is the lifting network optimised yet? no.
Is the turbine design optimised yet? no.
Has prototype performance smashed the other designs out of the park? yes.
Should it have because it’s small and therefore has relatively more drag? no.
Holy F, How many teams report working on this type? Only 3.
Will it actually scale?
Well a few tests here seem to say yes. Scaling by stacking works. I have also flown kite turbines with more drive kites per ring. Better demo coming soon.
To recap on a couple of scaling threads…
These sim sets show multiple Tensile Rotary Power Transfer rig designs work even on purely soft TRPT net designs given a good range of driving kite dynamics which inflate, lift and rotate the rig.
Concluding this post (at last and back to work) Adding to what I said at the start
There will be no other land use permitted under early model AWES used for permanent utility, if that’s how you develop your system.
It’s how you play with as you develop your system that counts.
See Myrons latest Maxim again…
The process you use to get to the future is the future you get.
Rod, the land use management looks to be reasonable. And also your system is potentially more suitable in regard to the land use issue for many reasons such like redundancy of constrained tethers in rotating columns of low radius, small elements in flight, and above all a far better potential of Power to space use ratio.
The network will work well when winds lead it in expansion. Problems can occur when winds will lead it in contraction. For these problems I would suggest to think about the AWES farm in bumper car mode concept. Why not using some lifter kites (for example some unities of the Sharp rotor that is stiff enough) as separators?
I particularly like your suggestion of Bumper car mode @PierreB
In order to make multiple rotary tower kite turbines compatible with collisions, their configuration needs to change so that the driving wings do not protrude outwards from the torque net.
The Djembe OM kite is a Dasiy type designed along those lines…
@Rodread I think the Bumper car mode could concern the upper layer with lifter kites. Both ground anchoring spacing and upper layer(s) spacing might be enough, the collision zones being only in the upper layers.
Implementing rigid elements such like inflatable or semi-rigid kites in each of the stitches would not be necessarily required.
It would suffice to place some of these elements in various orientations in order to allow the approximation until the collision included of the elements of the upper layer without the turbines colliding.
That said what you indicated above and I quote below looks to be a workable solution for turbines colliding. Thus the full Daisy network could work in Bumper car mode. It would be yet better.
Now a related question will be the securing of the superimposed rotors. The Bumper car mode could be not suitable even if some elements could add also some torque transfer.
I rather think about an accordion configuration, implementing retractable tethers.
kFarm started as a private airfield and hay farm that became an AWES R&D site for three years. It was shown that commercial hay-farming, cattle-grazing, kites, and aircraft easily co-exist. Integrating kites with general aviation is simply a matter of shared land and airspace, by coordinated operations. Several other AWES programs have validated similar spatial co-operations. Advancing airspace automation will support ever more complex airspace usage.
Land is not used intensively in many remote and rural parts, such as where I live.
Alternative land use wasn’t always a top priority for me …
However, everyone has food sustainability considerations at the moment.
In order to maintain layers of AWES and farming, there needs to be physical protection of the delicate biological and delicate kite materials.
The best way to grow food reliably here in our harsh, windy and cool conditions is inside a polycrub.
At 2m tall there’s not a lot of clearance to worry about. There have been some fairly large arrays of them. The convex polycarbonate shell offers good protection to workers inside. As a bonus the frame is made from recycled fish farm pipes, of which I have removed ~100m from local shores.
Depending on the compliance of your kite device, it could be landed on, bent over and attached onto these shells. Kite rings are pliant when not being flown.
1 more thought. Not strictly land use… Tensile kite lattice frameworks were proposed as an enabler of vertical farming support. Personally I’m concerned the wet mass implications of such design concepts would be a show stopper.
It can be a possibility in some cases. AWES designers, and farmers, could agree on the compatible sorts of AWES and farming.
That said knowing that “A Polycrub is a permanent structure”, the “build typically takes around 50 — 100 hours, depending on size, ground conditions and any internal fit-out”, I would be curious about the price of its implementation on a whole land area of a basic AWES (about 1 km² by taking account of the wind rose). We will likely not see poly tunnels under AWES for a long time…
Polytunnels are a great idea under giant soft kites. Underground concrete bunkers had been suggested in the past for operations under high-mass high-velocity AWES [Old Forum, Feb 9, 2010].
The tunnel form is not only apt to not snag active kites, but could comprise special kite support structures to store and dry kites (solar and/or forced-air), as a giant “spinnaker-sock”, or a long gallery suited to lay out line rigging, or even assemble giant kites on-site. Polytunnels could protect vehicle and pedestrian traffic across a kite field.
The Shetland Polycrub is a particularly outstanding wind-resistant design, based on poly-tube reuse. It could be a ready basis for scaling up Inuit Windsled design. Such structure is inherently lightweight, and could even evolve into airborne service, as an Aerotecture design option.
Commercial pilots sometimes joke, “I work in aluminum tubing”. An AWES pilot might someday be said to work in poly-tubing.
A word of warning in this video to anyone who swears that just by using a network of tethers (that sounds like me) That nothing can go wrong.
If you don’t maintain failed or failing tethers extra load goes to the remaining set.
We all knew this was coming to Arecibo radar telescope … but it’s still tragic to watch science be abandoned.
@PierreB you have performed research into the ground use efficiency of AWES
e.g. how many m2 land is used / kW power generated.
Generally - AWES have a ground footprint and a sky footprint (Wingprint?)
For a given wing-print area an AWES has a safe working permitted ground print area
Relating these areas gives a very simple number to compare systems.
(Kinda like solidity in rotor analysis - rotor solidity relates swept area / blade area )
Single ground station designs may like to claim that ground footprint is minimal and the equation is simply like looking at the solid angle or field of view of their wing in the sky
but fall safety zones are much more important to overall ground use.
For me it seems right that stacked rotors able to work in close arrays will win out on this comparison of land use / sky use…
Anyone got a good reference to better analysis?
@Rodread I had already discussed the land use issue, taking account of your observations.
My model is not yet refined and mainly apply to utility-scale rigid crosswind kites which fly at a low elevation angle, a large part of the tether being close to the ground, this because they accumulate dangers such as the high speed of both aircraft and tether, high mass, high kinetic energy. So in a preliminary approach secondary use is not possible or not easy on more than a perimeter were the tether is the radius, so much for land use that space use.
The footprint is another thing I think and concerns the area of the installations on the ground. For all AWES said area is very small. But for utility-scale rigid crosswind kites, land use prevails. For some other AWES, comprising rotary stationary systems, land (and space) use could be lower as the flight path is restrained and the rigid elements (for Daisy) can be smaller, so less dangerous.
The ideal is that the land use could be closer to the footprint. It would be more possible with stationary or slow AWES flying at high elevation angle. In kite festival we can see that the land use is not much larger than the footprint for even huge static kites which are very close each other and are only separated by their respective wing span. Similarly land (sea) use of crosswind kites can be reduced towards their moving footprint when unities go in the same direction, as for kite surfing competitions, or perhaps AWES using a track with two elongate parts as for NTS video at 1:22 or Kitefarms patent published.
I’m not sure if we discussed this; land use may increase due to the tether going really slack in the return phase for yoyo. If the tether is totally slack the tether will be free falling. So there needs to be a slight tether tension on return. This tension is hugely detrimental to cycle average power. So - weighing pros and cons, you are likely to not want trees, poles, buildings etc in the area surrounding a such AWE installation.
I think the increase in land area use may be substantial enough to include in a model
I think so too, and there are probably other issues that we just don’t imagine yet. That said during the reel-in phase, and in particular if the reeling speed of the tether is high (for example for rigid kites), a lower tension of said tether can be sufficient so that it does not fall, and all the more so that the tether gets shorter during the operation.