See Info on hydrogen and (tethered) hydrogen aerostats for the topic of this thread.
This topic was split from: An alternative method to tap high altitude winds [producing chemical energy at altitude]
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See the “Table 5 Reference photovoltaic plant considered for hydrogen production”.
The photovoltaic plant is onboard. Interesting.
I don’t get that from the text? Reference [43] says this:
And there’s also table 7 that talks about the size of the solar park. If there is a solar park onboard it is for propulsion I think. I find the paper confusing to be honest.
Quotes from the Abstract:
“The MAAT cruiser feeder system is based on two different airships, the cruiser, which remains airborne for long times, and the feeder, which connects the cruiser with the ground and vice versa.”
“The on board generation of hydrogen as an energy system is very convenient on long permanence airships because the replacement buoyant gas can be produced on board.”
From 10 Energy needs for flight:
“The energy production has estimated in a precedent paper [20] for square meter of photovoltaic surface at various latitudes. The photovoltaic surface has estimated about 61,000 m3.”
Indeed this is not quite explicit. But as it is sure that hydrogen as buoyant gas is produced on board, and by a photovoltaic plant, one can suppose that the photovoltaic plant is on board, on the top of the envelope in a similar way as for an industrial roof. Propulsion is supplied by electricity produced by the photovoltaic plant also.
The paper fails to identify well-known engineering factors that make hydrogen such a remote hope.
For examples, huge balloon hangars are needed to survive storms, unless the H2 is dumped, but its a powerful greenhouse gas that must not be dumped. Advocates agree it leaks anyway, the molecules are so small. Overlooked is the need for dumping or purification upon eventual air contamination threatening explosiveness. A single tracer bullet can bring down the mightiest new H2 airship.
AWE is such a great emerging engineering opportunity compared to more LTA marginalization. They are not synergistic; LTA is the hurtful partner. Pure Kite Lift is superior.
Related topics: AWES using LTA with PV for hydrogen production on board
Is an electrically heated balloon lift support for AWES possible? .
I’ve lost interest in the idea from the first post. I’d like to now explore the idea of just using a hydrogen balloon instead of, or in addition to, lifter kites a bit more.
Perhaps you could do pressurization tests of balloons too. Like this for example:
“endosmose” is the archaic form of endosmosis. It is not the right term for this phenomenon I think. The book is also from 1840, technology has moved on.
Because you will always try to have a higher internal pressure than atmospheric pressure, gas should flow out, not in.
Also permeability of an envelope to hydrogen is much higher than permeability of that envelope to air. So instead of air seeping in, you would sooner see the balloon just deflating. But of course you’d have a pressure gauge inside the balloon to measure pressure and if it became too low you’d either inflate a ballonnet to increase pressure again or take the balloon down for inspection.
@Windy_Skies Endosmose (here in French language) is related to the density of the fluids. The archaic form of endosmosis is none other than the initial term in French, “endosmose” (or “osmose”), for a phenomenon described by Henri Dultrochet
The English translation of some passages is:
“The endosmosis or osmosis discovered by Henri Dutrochet describes the way in which two fluids of different density conduct themselves which are only separated by a porous and breathable membrane.”
“The velocities with which two gases pass through a weak orifice of a membrane, are in inverse proportion to the square root of their density.”
endosmose of which I provided the link for the book from 1840 describes the same phenomenon (but without precise details), and has nothing to do with pressure as such, whether in its archaic form or not.
No. As I report the explanations above, it is an affair of density, not pressure.
But from the first post:
This is not the same as “just using a hydrogen balloon” which would be off-topic in regard to the content of your initial post. So a discussion about “just using a hydrogen balloon” would require another topic.
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Thanks @PierreB, that Wikipedia article is excellent. I stand corrected on « endosmose ».
Not sure how much I trust this ratio and claim, since the reference is from 1865. « endosmose », like osmosis, will of course still be influenced by pressure differences. I think it is probable that air leaking in will be completely eliminated with a small pressure difference.
Reference [14]:
I’ve split the topic.
You could also (measure oxygen or/and hydrogen concentration if that’s possible and) periodically or continually add a spark to eliminate any oxygen.
THE WILEY ENCYCLOPEDIA OF PACKAGING TECHNOLOGY THIRD EDITION
AWE operation is for a long time. So the process of endosmosis (see texts and links above) is likely crippling. As indicated in the quotes above when 3.5 volumes of hydrogen leave the balloon, 1 volume of air enters, which in the long run gives an explosive mixture.
Perhaps a kind of valve located at the bottom of the balloon would allow the air which is heavier to be evacuated. However, the instability of hydrogen makes any transfer and manipulation perilous, as for slowly filling by using an electrolyser on board as described on AWES using LTA with PV for hydrogen production on board - #16 by PierreB.
Besides it (not burned) hydrogen “acts as an indirect greenhouse gas” (Other Greenhouse gases - Hydrogen).
I remember a way to make clean hydrogen I do strongly not recommend because it is very dangerous, the process giving off a lot of heat. Put aluminum, caustic soda (unblocker), and water in a plastic bottle or a jerry can, fix the opening of the balloon and … move away. I inflated like this several hydrogen balloons up to 1 m³ with 1 kg of aluminum.
Any hydrogen balloon envelope material you would consider using would not be permeable to air, so the concept of « endosmose » would not be applicable to air entering the balloon. Because the pressure inside the balloon is greater than the pressure outside of the balloon, air would sooner leave the balloon than enter it. I’ve said this before using more words.
Because the balloon envelope is permeable to hydrogen, the concept of « endosmose » might be applicable to hydrogen leaving the balloon, but to make use of the concept, you would need to find more recent sources with equations with relevant variables – like pressure difference, permeability and thickness of material, and densities of the fluids – accounted for.
If my interest continues, I will try to find more sources on permeability of different envelope materials to hydrogen and helium, permeability of whole systems to the same, influence of UV exposure, time, and handling on the materials. If my interest continues I’ll also try to find products you could order now.
I’m also still curious about catalytic recombination of hydrogen and oxygen using palladium for example.
Yes, so be careful in designing your system. If you do that the risks are manageable. Another quote from a link I gave earlier:
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You could always say that handling H2 is not an issue and that there are ways to do it safely. In reality, there will always be risk involved, and other fuels will carry less risk than residual H2 handling risk. I’m not saying dont do H2, I’m saying just be realistic about the risks and the associated costs involved.
This accident was a wake up call to many Norwegians about this:
translated:
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Endosmosis (in French language) is not a perishable concept, but a permanent phenomenon which was discovered by Henri Dultrochet.
Your statement is contradicted by the following quote from the linked article: “La densité de l’hydrogène pur étant quatorze fois et demie moindre que celle de l’air, on comprend qu’il devra passer environ quatre fois plus d’hydrogène dans l’air que d’air dans l’hydrogène”. The translation in English language is: “The density of pure hydrogen being fourteen and a half times less than that of air, we understand that it will have to pass about four times more hydrogen in air than air in hydrogen.”
As a result endosmosis is also applicable to air entering the balloon, but in a lesser proportion due to the respective densities of air and hydrogen. It is an affair of density as I repeat.
That said variables such as “pressure difference, permeability and thickness of material” can occur. The long permanence high altitude airships: the opportunity of hydrogen paper you linked mentions the calculations of the leaks according to the altitude, but not the air entering the balloon that makes a high risk.
It is quite right. By using hydrogen we obtain also soon or late an explosive mixture after some time dependent of variables such as " pressure difference, permeability and thickness of material". So unless some means (such as a valve I evoked previously) are found, the hydrogen use for long time AWE operation seems to not be appropriate. It is not for nothing that almost all manufacturers use helium.
The comparison with devices using “pressurized hydrogen to cool generators” does not stand because endosmosis cannot occur.
Give a reference that proves that oxygen seeps into an undamaged, low permeability envelope, high quality hydrogen or helium aerostat made in this century that was inflated to higher than atmospheric pressure, and I think we have a better basis for discussion.
Give a reference that proves that air does not enter any gas balloon.
Windy Skies cannot get third-party prior reference for any true advance. By that moderation criteria, Galileo himself would not have been allowed to post here, as he first wrote of his discoveries.
The Austin Robot Group had early access (1980’s) to super-sensitive gas detectors from Motorola labs for our robotic blimps. We played with them briefly, but they did not prove operationally useful. The simple way to tell if your envelope is losing gas is just let it sit, and the pressure drop will soon be apparent in the stiffness of the membrane.
Top of an LTA envelope is always “higher than atmospheric pressure” in normal use, even for rigid airships with slack in their gas bags.
I think from prior «research» that the rate of transport of gas through a membrane is not dependent on pressure but rather the membrane properties and the concentration of a certain gas on either side.
Pressure would be more related to leakage through holes in the membrane, which is a different kind of process.
The take-away being that high pressure does not increase the rate of transport through the membrane.
If you are not certain of these processes, I would seek advice of someone knowledgeable about these things (as opposed to myself)
Even such a solution would be random given the shakes due to the wind effect on the balloon, and which would not fail to contribute to the explosive mixture of air and hydrogen.
The diffusion coefficients are 1 for air, and 3.7947 for hydrogen.
A more recent review is on the answer about https://www.quora.com/Is-it-possible-to-create-a-toy-helium-balloon-that-will-remain-aloft-for-years : “Not only does helium leak right through the skin of the balloon but regular air also leaks in.”
This matches the phenomenon of endosmosis such as linked above, and also the related experiment: