AWE no for upper winds, this is nonsense. For low altitude we have HAWT which work very well.
“Pivoting” to something else is only a mean to avoid facing major failure.
For the rest, I will refrain from repeating the arguments I just mentioned.
To resume: a kite is good for lift, as lifter for several things including solar panels; but a kite is not designed for wind power generation by itself.
Let’s say the floor is lava, or you’re off shore, then a train of lifter kites with laundry solar kites with on board batteries might be fun to play with. For lower altitudes you might use a power cable. Gliders are also nice.
If the floor isn’t lava, I don’t think it’s that unlikely that good solar panels will begin to approach the durability and lifetime of hardened glass. Good luck competing with that.
Flying solar panel (ASWES) have about as much chance of competing with ground-mounted solar panels as AWES have of competing with HAWT, I would tell even a little more.
Granted, flexible solar cells have a limited lifespan compared to heavier ground-mounted installations, but the goal is to provide additional solar area capacity.
As for AWES flying at an elevation angle of about 30 degrees, there is one thing we can be sure of: there is almost no place for their implementation. Some flexible crosswind AWES produce some electricity: where are they installed?
And static kites have always flown at a high angle of elevation (see stacked static kites in kite festivals), as for aerostats. So kytoons for more lift capacity looks to be a natural solution.
The pressure at 6 km is half that at sea level, so the lift to maintain the weight would require twice the wing area.
Lets assume a 1 MW plant. At 200 W per sqm we would need 5.000 m2 area.
Also lets assume the altitude 6000 m and tether length 8000 m.
If the voltage is, say, 2 kV, the current would be around 500 A. The wire would have to be 1000 kcmil [?] meaning a weight of 5 kg per meter. Total cable mass 40 ton. Lift per square meter must be 8 kg weight per square meter. That is before we consider kite mass, solar panel mass, actuation, electronics, projected area etc etc
A C_L 1.0 wing at this altitude would lift 0.7 kg weight at 5 m/s wind speed per square meter, 4.3 kg at 12 m/s.
It seems to me a lot of optimization is necessary here…
http://www.energykitesystems.net/FAA/FAAfromMakani.pdf :
Page 3:
M5 Specs
Rated power: 5 MW
Full rated power wind speed: 9 m/s
Wing mass: 9,900 kg
Generation system: 8 brushless DC motors
Wing
Wing spar: carbon fiber
Wing skin: e-glass
Length: 1,060 m
Tether
Mass: 3,660 kg
Conductor: aluminum
Structure: pultruded carbon fiber
Voltage: 8 kV
Tether weight: 3.45 kg per meter for the 5 MW wing.
M600 Specs
Rated power: 600 kW
Full rated power wind speed: 9m/s
Wing mass: 1,050 kg
Generation system: 8 brushless DC motors
Wing
Wing spar: carbon fiber
Wing skin: e-glass
Length: 440m
Tether
Mass: 250 kg
Conductor: aluminum
Structure: pultruded carbon fiber
Voltage: 8 kV
Tether weight: 0.57 kg per meter for the 600 kW wing.
Half the power too… 
Not solar energy.
And wind is used only for lift, not to generate power…
Oh yeah, solar - sorry, I forgot. I guess the above is a spec from a Makani design.
Close to the ground the average wind speed is about 6 m/s.
At 6000 meters (where the sun shines almost always) the average wind speed is about 20 m/s.
At 0 km, air density is about 1.225 kg/m³.
At 6 km, air density is about 0.66 kg/m³.
So the average lift / m² is 22 N (about 2.2 kg) close to the ground, and 132 N at 6000 m.
Respective powers / m² would be 132 W and 2640 W.
Of course these numbers vary strongly. It is interesting that a solar kytoon including a thermal solar balloon will gain efficiency when the wind speed decreases, because the convection also decreases. However this gain will not compensate the loss by the lack of wind on the kite side. In all cases the global lift should be far higher than the global weight and also compensate for the tether drag, in order to keep a high elevation angle which is the essential thing for any implementation of AWE systems. So helium or hydrogen balloons should likely be added.
To resume: at 6000 m, sun energy is predictable, unlike wind energy.
Features
• Ultra-light solar films with only 60 g /m2 or 2.000 W per kg
• Customizable in width / length and voltage / current
• Interconnected cell arrays by a laser patterning process
• Rollable form factor
• Simple contacting of solar array on first and last cell
• Unbreakable and vibration resistant
• Made in SwitzerlandWeight [g / m2] 60
Nominal power [W / m2] 100-140Application platform for:
• Foldable or rollable ultra-light solar sun sails for space applications
• Ultra-light solar films for covering airship and stratospheric balloons
• Ultra-light Solar films for integration into drones and Aircrafts
• Solar blimps
• Fast deployable Military and Emergency respond solar applications
• Off-grid and Mobility solar solutions
• Solar automotive integrations into sunroofs
• Solar blinds, awnings and solar sunshades
• Integration into BIPV facades
• Integration into glass tubes for agricultural PV
• Integration to power IoT and sensor devices
• And many more ideas
120 W per square meter is even much lower than I assumed…
Excess wind would be absorbed by a wind turbine producing energy as long as the elevation angle remains within the right margin.
In first ASWES could be implemented in sunny areas to restrict tether length.
I don’t like that unit - Circular mil - Wikipedia. That’s 506.7\ mm^{2}, which is 4.5 kg per meter for just the copper I think, and ignoring if that wire size is available.
I can’t verify that. Two different formulas give me three different results:
This formula gives me for your values: \frac{2000V}{500A} = 4\ Ω , A = \frac{8000 \cdot 1.724 \cdot 10^{-8}}{4} = 1.3792 \cdot 10^{-4} \ m^2 , weight of just the copper: 8960 \cdot 1.3792 \cdot 10^{-4} = 1.23\ kg/m .
A = \frac{2 \cdot l \cdot I}{\gamma \cdot U_a} => A = \frac{2 \cdot 8000 \cdot 500}{58 \cdot 3} = 45977\ mm^2, 20 times the value the calculator on the page gets: 2298.85\ mm² …
Relevant: IEC 60228 - Wikipedia
I just found a high voltage wire online, and looking at the specs.
Something like this may serve as a starting point. Note 2 kV and 500 A [to be on average for an 1 MW plant].
Maybe also aluminum or other material could give more amps per weight. And of course, a graphene superconductor would be nice, though we are no longer COTS
Thermal and e-film solar kytoon (balloon + kite) systems could also be implemented at very low altitude, for projects such as Desertec - Wikipedia , the difference being that solar panels would not be directly on the ground, which would allow secondary uses, including perhaps food crops that would be facilitated by the shadows (thanks Joe Faust) carried by the solar kytoons, in addition to lowering the temperature and making some places easier to live.
Maybe probably
https://www.anixter.com/en_gb/resources/literature/wire-wisdom/copper-vs-aluminum-conductors.html
So we have only 120 W per sqm that means 8500 m2 area of the kite. And the mass of the condictive metal half, only 20 ton needing a lift of 2.3 N per sqm, achieveable around 8 m/s I guess. A 300 x 30 m wing may do the trick
I’m glad to hear solar films of such light weight are available. Inflatable support of any kind, whether flying or not, might become “a thing”.
I’ve been watch this explode the last few days.
I’d like to throw braided cables into the mix
Just for an example. I am I presses by the wealth of information here on awes. As far as I know braiding is usually stronger than standard cable. I’ve seen milling machines covered in this stuff. Usually as part of armoured cables. They do come in a variety of conductive materials. Carbon nanotubes Ive heard are extremely good conductors. They can be interwoven into polymer cables. Seen it done with a YouTube video but it something I’m yet to have a go at. Years back memory a little hazy. I believe solar panels are using nanotubes. As primary conductors mainly down to thermal resistance. Though don’t know more than that. I believe it was a US University that did the research some years back. When there was a load of excitement over carbon nanotubes. If the blimp it’s could be made from flexible panels in-bedded In the to skin? Then it wouldn’t take much to build it! And the light bending? Then it S.I.G for Aswes!
After a preliminary review, it appears that ASWES flying at an altitude of 6000 m, where the sun shines almost always everywhere, and at a high elevation angle, is not achievable without additional balloons inflated with hydrogen or helium, even if thermal solar aerostatic lift is used.
That said light available solar e-film leads to some AWE possibilities like solar kytoons at low altitude, and that free up the land for other uses. In this case the wind and thermal solar aerostatic lift are used for lift, the problem of mass of the rope being almost eliminated.
But we should keep the first goal of AWE, and perhaps add solar energy. I think about a helium or hydrogen balloon altitude base connected to the ground by an electric cable with a very high elevation angle. From this base of altitude would leave various AWES or ASWES.
An airborne test facility!
