Electrolysis production of H2 for Solar electric airship

turbo1889

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For starters - Yes, I am aware of the Hindenburg disaster hydrogen (H2) is flammable and if not kept separate from oxygen (including the depleted oxygen level of normal atmosphere) can burn. It does however take a very hot spark (over a 1,000 degrees F) to ignite and only when it has been mixed with oxygen or air in correct ratio. So long as you keep it separate from air and don't build your air-ship out of flammable canvas doped skin that ignites at much lower temperature and burns hot enough to then open up the H2 gas envelopes and mix it with the air and then ignite it - not a problem, especially on an unmanned vehicle.

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Okay, that stated, neutral buoyancy air-ships unlike any other aircraft do not require power even outside power such at thermals or up-drafts to stay aloft and only require power to move. This combined with their large surface are allows for potentially the perfect purely solar powered aircraft.

It is also true that there is always some very low but constant gas seepage (not enough to provide sufficient % fuel mix to be flammable) through the membrane walls of the gas cell(s) that means that buoyancy is constantly lost slowly over time and gas replenishment is necessary, this is especially true with pressurized gas envelopes on air-ships with non-rigid frames (blimps). Short term this issue is often addressed with ballast which is dropped to reduce the payload carried, among the most common and safest ballast used is water. Long term the only solution is lifting gas replenishment. For a hydrogen lifting gas airship, especially a solar powered one, this offers a unique potential of being able to replenish lifting gas in-flight from the water ballast through low voltage safe electrolysis of the water ballast splitting the H2O molecule and replenishing the lifting gas with the H2 produced and off-venting the oxygen to the atmosphere in an unmanned craft, or providing enriched oxygen to the crew of a manned craft (although care must be taken to ensure oxygen enrichment is not high enough to create a combustion hazard).

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I have a small RC blimp that I am experimenting with hydrogen lifting gas filling instead of helium fill which it was designed to use (ready made kit aircraft). At this point I have been producing the hydrogen through electrolysis of water using stainless steel electrodes in a solution of water with NaOH electrolyte. Hydrogen production has been incredibly slow with my present apparatus which is of the "Hofmann voltameter" type, homebuilt with PVC pipe and stainless steel tubing to form the electrodes (entire inner surface of the tubes are electrodes upon which the electro-chemical reaction takes place) with the PVC plastic being used as an insulating connecting joint in-between to provide the ionic bridge and it can take hours to fill the little blimp to sufficient pressure to hold its shape.

I've got to build a better apparatus capable of converting more electricity into larger amounts of hydrogen quicker and preferably in a smaller, lighter, and more compact system especially if in a larger scale home-build I am planning to do on-board lifting gas replenishment through electrolysis from the water ballast.

I've looked at HHO gas generators which are used in some internal combustion automotive applications to provide an injection of pure hydrogen and oxygen gas at the atmospheric intake for a short burst in power on demand (similar results to nitros injection systems) that run off the vehicles 12VDC electric system and store up pure hydrogen and oxygen gas at pressure until needed. Those systems use a stack of very thin stainless steel plates seperated from each other by mere millimeters to form a reasonably small cell capable of reasonably high gas production but they make no attempt to keep the hydrogen and oxygen gas produced separated but rather collect and store them as a mix under pressure something that not only will not work for my application but I consider rather dangerous to say the least. Mixing pure hydrogen gas with pure oxygen gas especially in a pressurized container where pressure reduces the necessary ignition temperature is like building a bomb. Hydrogen is safe and can't burn or explode so long as you keep it separate, its when it mixes with air that things can go wrong, mixing it with pure oxygen is really asking for it especially in a pressurized mix that lowers the ignition temperature.

I can use the same basic design though of thin plates stacked very close together and I've already sourced some nice think stainless steel rolled stock that should maximize surface area of the electrodes while minimizes size and weight.

The question is how to get the plates as close together as possible (closer together make more gas faster due to allowing higher current passage and also reduces the physical size and weight of the water/electrolyte mix the cell is filled with) while still keeping the hydrogen gas bubbles generated at the negatively charged plates separated from the oxygen gas bubbles generated at the positively charged plates.

I need some kind of non-electrically involved middle membranes between the plates that allow the free flow of ions in the liquid while preventing gas bubbles from crossing over to the other side and the gases mixing. It must also be non-degraded by the caustic water NaOH electrolyte mixture in the cell.

Anyone ever worked with water electrolysis cells before? Anyone know what I could use for that middle membrane?
 
Forget electrolysis
NaOH + aluminium generates lots of hydrogen very easially
 
generating H2 from water ballast that is going to be dumped anyways is an intriguing option. US Navy submarines have been using electrolysis for decades (of course they throw away the H2 and keep the O2)

I am reminded of the breakthrough that permitted a world record a few years ago, concerning travel by balloon. When the balloon would get cold at night, the hot air had to be replenished by burning kerosene (propane pilot light, IIRC). The breakthrough was to design a balloon with two concentric chambers. The outer "shell" chamber was filled with helium (or H2?), and the inner core chamber was heated by burning kerosene. The outer shell provided an insulating layer to dramatically slow the loss of generated heat.

I also noticed that recent working airships have a pancake shape, to reduce the influence of side-winds.

hybrid%20airship%20p791.jpg
 
you need to do do more planning. or stick with helium which the envelope you bot is designed for.

when you mentioned the 'depleted' levels of oxygen in the atmosphere it made me concerned you were working from another planet.

if i recall the term 'lighter than air' vehicle is usually how we describe blimps but if you intend to carry the gas manufacturing plant with you on the ship it is gonna be heavier than a locomotive imo. especially if you intend to manufacture the gas with silicon PV panels and stainless electrodes.
 
On-board electrolysis H2 gas generator need only be big enough to replenish leakage due to gas chamber wall seepage. Ground mounted system (possibly chemical reaction based rather then electrolysis as alluded too by Ricky_nz) for initial fill. Thin very light weight solar panels on top to provide electric motors and electronics with power with all excess juice after back-up battery is fully charged diverted to electrolysis cell.

As to depleted oxygen level in earths atmosphere, it is certainly "diluted" and not pure (may have been better word to use in context) but it is also true that since the industrial revolution it also has been depleted and is not as high as it once was. As CO2 content has gone up O2 content has gone down since the O2 that was combined with the burning of carbon fuels was almost entirely of atmospheric origin. So it is an accurate statement to talk about O2 depletion in earths atmosphere.

The current little RC model is just a test ship, I want to build considerably larger when I get the H2 production issue licked, I'm was thinking pancake shaped as well probably about 500-1,000 ft^3 volume or so for the first unmanned larger outdoor size model.
 
Should also mention the lift capabilities of the gases in question:

H2 approx =< 0.07 lb/ft^3 (depending on pressure in cells, increased pressure in gas cells with a non-rigid blimp like structure reduces lift capacity)
He2 approx =< 0.03 lb/ft^3 (depending on pressure in cells, increased pressure in gas cells with a non-rigid blimp like structure reduces lift capacity)

So with a 500-to-1,000 ft^3 H2 lifting gas capacity rigid or semi-rigid airship that does not require significant compression of the H2 to hold structure then we are talking about a 30-70 lb. craft.

As to solar cells used I'm thinking of using the same ultra thin, ultra light weight ones they put in the wings of RC solar powered soaring gliders. Li-Poly batter pack, RC brushless motors, small computer with cell phone modem link to ground control lap-top, water ballast, H2 slow but steady electrolysis replenishment, zoomable HD web-cam on turret mount on the under-belly, GPS navigation. Something that can remain air-born under solar power alone for weeks with the motors shutting down at night and the computer going into low power standby or hibernation mode and then as soon as the sun comes up and the solar cells start pumping out power everything comes alive. You get the idea.

Even had ideas about a night moisture condenser to replenish water ballast reserves.
 
It was the Hindenberg itself that caught fire when lightning struck it, not the hydrogen gas. Don't have a ready link to info on it but I've read it didn't get hot enough for the hydrogen to burn. Airships offer wonderful possibilities, especially as UAV's.
 
speedmd said:

Thank you very much for the links, the first one led me to research more information on the pulsing fundamental KHz frequency method of getting much better efficiency and production from water electrolysis.

I am by no means convinced that "you get out more energy then you put in" but that is not what I care about or am trying to do. I just want to get a lot more H2 gas out then I am currently getting from preferably a smaller unit and of course doing it more efficiently so I don't have to use as much electricity for the same amount of H2 gas generated is always nice but isn't a huge thing for me since I've got my own home solar/wind/thermal-stack power generation capabilities which exceed my own present needs quite often and I'm tied into one of the cheapest grid power sources for when what I produce myself isn't enough that is the power company/co-op owned and managed by the neighboring Native American reservation population and they ain't dumb or lazy just get drunk all the time type but are a very good strong group of people that so far as I have seen seem to manage their affairs especially the electric company and generation plants including a great big hydro-electric dam better then white man and his government seem to. I even send them back some of my power at times with my line tie inverter to make the meter run backwards and sometimes I get a check from them instead of a bill. Long story short, I just want to be able to make a bunch of H2 from electrolysis the whole "more energy out then you put in thing doesn't tip my fancy and I have some trouble believing it anyway. Not that it isn't completely impossible, I know modern electric powered heat pump heating systems can operate at 300% or more because the electric power in is used to move existing heat from an area of lower temperature to an area of higher temperature plus all the input electric power so you get more heat out of them then you put in electric power because they work by "stealing" the heat energy so to speak out of the outside ground or air.

Since I've also researched the "high temperature electrolysis of water" methodology and technology where the water is heated to very high temperature under pressure and very little electric energy is need to cause the reaction since most of the energy required is provided by the heat and the resulting gases produced are much cooler then the original water and the reaction has a cooling effect on the water as well so heat must be continuously added demonstrating the absorption of the heat energy to drive the reaction primarily with only just enough electrical power added to keep the reaction going. I do consider it as possible that using this fundamental pulse technology is allowing the same thing to happen at a much lower temperature. Namely, room temperature, and most of the energy to drive the reaction is being "stolen" from the heat energy in the water at room temperature and the surrounding area. Whether this is what is happening or not can be easily determined with some simple insulating of the electrolysis cell and temperature sensors for the water and gas out lines which I may ultimately do "just for kicks". My suspicions that this at least in some small part may be what is happening is increased by the reports that electrolysis cells using this technique are "cool to the touch" although if it was happening to any significant degree and at high enough of a reaction rate I would expect more then just "cool" and more like down right "cold" and in starting to generate some ice and or frost. Still if this is what is happening I would find it hard to believe that it is drastic enough and at high enough super 100 percentiles to actually drive an internal combustion reciprocating piston engine as the output and still "get out more then you are putting in" which usually operate at inefficiencies of less then 20% so you would have to be getting over 500% in hydrogen production with the electrical energy input being less then a fifth of the power input and the vast majority of power driving the reaction being "stolen" heat energy just to break even and considerably more then that to "get out more then you put in" so that you could run a car engine off the hydrogen produced just using a low current from the alternator to drive the reaction. Not even the best heat pumps get anywhere close to the super 100 percentile efficiency that kind of situation would require. I haven't yet been able to get any numbers on the percentage of heat energy vs. electric energy in conventional "high temperature electrolysis of water" and those would be the numbers to compare too that would be better then heat pump numbers. If this "stolen thermal energy like a heat pump" theory of mine is what is going on then you might be able to get "more out then your putting in" using a hydrogen fuel cell and electric motor because the efficiency of that is so much better then an internal combustion reciprocating piston engine but even then that is still probably pushing it.

So either the whole "get more out then your putting in" thing is a "big hoax" or there is some other kind of energy source that is primarily driving the reaction besides electrical or latent thermal. If it is true and my initual "latent thermal energy" hypothesis turned out to be false the next thing I would do is check the off gases for trace amounts of helium, which if found I'd convince a team of hackers like "anonymous" or similar to anonymously flood the web with the results as the first practical demonstration of cold fusion and then hide out in a hole somewhere for a year or two fearing for my life.

A lot of this "free energy stuff" is either hoax or stuff that can get you on the top of a hit list that is pretty much a sure thing. I just want to turn electricity into hydrogen gas and do a lot of it efficiently and quickly without a "locomotive size and weight" apparatus. A couple hundred pound apparatus would be okay for the ground system for the initial fill but even on it I don't want to get into the ridiculous.

The you-tube video links clearly show that regardless of the status of the supposed "get more out then you put in" factor this method of high frequency pulses can clearly make a whole lot more gas faster with a smaller apparatus then what I'm currently using and possibly with less power (more efficient even if efficiency isn't higher then 100%) then what I'm currently using so that's the direction I'm headed right now. I especially like that no electrolyte is needed and you can just use straight water which makes it much easier and safer.

Dauntless said:
It was the Hindenberg itself that caught fire when lightning struck it, not the hydrogen gas. Don't have a ready link to info on it but I've read it didn't get hot enough for the hydrogen to burn. Airships offer wonderful possibilities, especially as UAV's.

Yes, it is my understanding from what I've read and educational shows I've watched that the hydrogen in the Hindenburg disaster did burn it just wasn't the first thing to burn and especially wasn't where the fire started. The fire started in the cloth coating where actual tests on some of the actual remaining salvaged un-burned nose section outer coating (yes, actual remaining un-burned scraps of the actual wreckage primarily from an un-burned section of the nose which it is theorized the only reason it didn't burn it because the fire ate up so much oxygen that bubbles of air without oxygen were created around some of the remaining wreckage which kept it from burning all up) were demonstrated on film where long thin strips several feet long of it were so flammable because of the coatings used that when touched with an ordinary match instantly burst into flame and burned so fast that you couldn't let go of the other end fast enough for the fire to not reach your hand !!! How the fire actually started is disputed to this day with reasonable evidence being demonstrated for, static electric charge, lightening strike, antennae wire malfunction (there was an antennae wire stretched to the rear upper section where the fire started), engine exhaust spark arrester malfunction, and even sabotage but almost everyone except the most uninformed and uneducated "knee jerk" anti-hydrogen as lifting gas people blame the hydrogen and most all agree that the hydrogen did burn but only burned once the main fire got hot enough to ignite it (over a 1,000 degrees F). There has been some debate as to whether the hydrogen that was off-vented during the landing procedure started to burn before the main lifting gas bladder walls were burned through or not.

This is very unfortunate since to this day the prominent misconceptions about the disaster being "the fault" of the hydrogen lifting gas along with the rarity and expense of helium gas has severely hampered airship development and use to this day when they are among the most efficient of all aircraft especially for caring heavy loads. Lets not forget the great airships of WWI and the tons and tons and tons of bombs they carried into combat (tons of bombs were carried in each load which far exceeded anything winged aircraft of the day could even think about accomplishing and were only just barely matched even by the most heavy bombers of WWII) and dropped on their targets under punishing heavy fire from guns, rockets, and even grenades dropped on them from above by the open cockpit bi-plane fighter aircraft of the day and the hydrogen lifting gas was rarely ignited under all but the most punishing retaliation until the implementation of very high temperature incendiary bullets which had an ignition temperature of thousands of degrees. Some thoughts to the tremendous bomb load weights these warships of the sky carried in WWI should also bring pause to some comments about "heavy as a locomotive" although I have no intentions of building an airship that large it should not be ignored that airship technology that is over 8 decades old was fully capable of not only hauling the weight of a locomotive but possibly more then one at once !!! Me, the biggest I would want to go would be "big hot air balloon size" which would have a weight lifting capacity of about a ton or more considering that hydrogen lifting gas is the most buoyant of all possibilities and far exceeds the lifting capacity of simple hot air. But even then that would be in the distant future for anything manned, UAV aerial HD web-cam video and still photography drone capable of remaining air-born for weeks under solar power alone is my main goal, right now just using an ultra-light indoor RC pre-made blimp intended for helium that doesn't even weight a full pound, possibly a bigger outdoor RC "toy" model before going to the full solar UAV airship that is my goal.

In my design I do not intend to do any off-venting but instead use a double chamber system with a collapsible inner chamber inside the hydrogen lift chamber(s) that when pumped full of regular air reduce the lift capacity by compressing the hydrogen slightly (up to about 150% normal pressure which I hope to keep barely above atmospheric pressure) within a smaller volume to decrease buoyancy when necessary without any off venting both for safety and lifting gas conservation reasons. That system is very often used in modern helium lift gas airships primarily for the reason of conserving the very valuable, rare, and expensive helium gas.
 
And oh yah, should mention, I'm not talking about NSA type "big brother" drone spying missions. Just want a high altitude stable platform so beautiful aerial photography "fun" not unlike mounting a camera on an Estates model rocket only a lot longer duration then the short up and then right back down action that set-up is capable of. Also consider it "proof of concept" for distant future manned craft. Theoretically such a solar powered hydrogen lifting gas air-ship could be one of cheapest, quietest, most calm, and beautiful ways to travel the world riding the winds above the clouds while still having power to maneuver in and out of different airflow patterns and even travel against the wind when necessary. Would be especially impressive if could get the altitude capabilities to get into and ride the jet-streams. That would allow traveling at speeds in the 100-miles an hour range without any output of power to the motors except to just stay in the stream and a calm smooth ride in those giant "rivers in the sky" just like riding the "rivers of the sea" such as the Gulf Stream Current in a sailing ship only a lot faster and a lot more beautiful way up there in the sun above the clouds.
 
Hi Turbo,

Sounds like a great project!

Have you got any further in the last months??
 
The first thing I would do is take a look at the lightweight hydrogen storage systems that have been developed for automotive fuel-cells and compare it to the weight of water/electrolyser/solar panels required to produce the same amount of hydrogen.

Regarding the Hindenburg disaster, of 97 passengers and crew on board 62 survived, many unscathed. Of those who did perish some were as a result of jumping from height, smoke inhalation or falling debris rather than fire.
 
before you go to far with hydrogen, fill a party balloon with hydrogen and put flame to it, just to get a sense of what your dealing with ( I would not be too close to the balloon if you try this)
 
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