“…our panel converts moisture from the air into hydrogen gas.”, so without electrolyser, without carrying water. That could become a useful technology for some AWES if the panels become soft and light.
The engineering fundamental limiting Zeppelin’s that killed their travel and military markets was slow speed (high drag). Jet travel near Mach1 (and beyond) won. No one expects past temporary success of LTA to repeat, once better solutions took over.
This is the quote that made it look like Pierre (suddenly) believed in LTA, in the AWE context-
My opinion evolved after seeing a link provided by @Windy_Skies:
No one has tested LTA more broadly in AWE than me (KiteShip and KiteLab Portland, 2007), starting from an actual background in hot air and He LTA going back to 1970s.
I settled on the power kite after trying many directions. Not too surprising that “pure kite” (“rag and string”) is a good bet. Power kite sports and ship-kites well confirm “possibility in wind production”.
In the paper the amount of PV plant is calculated to fully inflate the airship during a year.
For a use as AWES it is only necessary to fill the leaks which are less than 10% volume/year (according to different parameters such like porosity, and by taking account of the size of the studied airship in the paper), decreasing with altitude. Compression and storage of hydrogen are unnecessary, both on the ground and in flight, which saves weight and cost.
We add wings for this balloon in order to keep a lift-to-drag ratio (with wind turbines on board) over 1 even by high winds, another option being using Sharp rotor assuring a L/D ratio of about 2.3 (without the turbines aloft). This would be a (not crosswind excepted for the propellers motion) static system.
As an hypothesis we install (lighter thanks to ground generators) @Kitewinder propellers with rope-drive transmission on the wings or elsewhere.
Indeed you omit to mention that your 600 m3 lifter could lift a payload of 500 kg which makes it more interesting, itself being inflated by a ~5 kg device. If you could make it withstand any wind plausible I guess it would make a good substitute for a radio tower.
I am still not convinced of the practicality of this. But the idea is indeed intriguing.
I still believe that using rams to keep it’s shape in wind could be a good addition to the design, to prevent adding a pump to the design.
I’d like to expand on the idea if a combined ram air kite/ hydrogen aerostat.
Say the ram air kite had a flat shape in winds, thus a moderate drag. Inside the belly of the ram air kite there is a room where a bladder is contained. In normal use, the bladder is quite inflated, thus providing lift and also making the kite have a lot more drag. In the event of extreme strong winds, the bladder gas could be expelled so that the kite could regain it’s slim profile.
The reason for doing this would be to make the kite pull a lot less in extreme winds (by reducing the drag and then indirectly the required aerodynamic lift). Thus the dimension of the tether and auxillary systems would be reduced (perhaps into feasibility).
Just throwing out some random ideas here, I have not done any thorough analysis.
How would that work? [Edit: never mind, I see your followup post] If you want to make a balloon that is able to withstand higher winds you would already increase the pressure inside to withstand deformation from the wind, and you’d perhaps limit the size so you can increase internal pressure more with identical thickness of envelope material. You could also make the balloon more into the shape of a teardrop (1) instead of a sphere.
If you temporarily want to increase pressure, you could add ballonnets inside the balloon and then fill them with nitrogen for example. After the storm has passed you could vent the nitrogen.
https://www.empa.ch/web/s307 intended to fill the kite with helium. Indeed I think a small electrolyser and a 1 m² PV would be enough to keep the LEI kite inflated, even if the available volume is likely not sufficient to keep it in the air. However with the process I describe, the pressure will be that of the ambient air, no more, except if we add a compressor or… a pump, involving in additional weight and cost.
Another possibility: a central lifter kite-balloon with PV-electrolyser on board and dancing kites (possibly comprising also PV-electrolyser) around.
Note also the link for a new (but not still available) technology to produce directly hydrogen with solar on
Plus 100 kg of water to make the 120 m³ of hydrogen, by year. This can be still workable, but the process to produce hydrogen directly could be better if it becomes available. Another possibility is waiting for large storms (1/month?) to recovery the system and refuel water (about 10 kg). Another possibility is collect water in flight (rain, dew).
H2 loss will be 100% in a bad storm, without a hangar or required deflation. Slow H2 leakage also corresponds with increasing air contamination and unacceptable explosion risk, and still adds greenhouse gas.
Harvesting water vapor aloft instead of raising water will be comparatively marginal.
Endosmose is also a problem with He also, where air contamination is only parasitic of lift. The gas gets replaced in bulk, sooner if lift-force operating margin is accordingly smaller.
A new balloon is effectively gas-tight but delicate, and soon develops tiny leaks over time that relentlessly dilute the lifting gas, with no easy solution. Thermal cycles and general envelope motions help push lifting gas out and air in.
I used to store micro-blimps in a dark quiet stable temperature room, nose-up, and only replace the bottom gas, with its higher air content, from the tail-cap.
“…a substantially airtight chamber for storing lighter-than-air gases”.
The chamber must be airtight enough to avoid the process of endosmosis leading to an “unacceptable explosion risk” as @kitefreak rightly indicates, while being still light enough.