Automated Hydrogen Generator

in this video I'll show how I built my hydrogen generator which can make close to 20 L per hour of pure hydrogen using water electrolysis to make a mixture of hydrogen and oxygen or H seems to be a popular project on the Internet it's easy to do and the balloons make great fireworks by detonating with a supersonic flame front but as fun as H is I can't seem to find any practical use for it except maybe as a cutting torch for really small scale work or when you don't have access to an oxy acetylene flame pure hydrogen on the other hand has innumerable uses in my case I want to attempt to liquefy it in a juel Thompson cycle by using liquid nitrogen for pre-cooling another use in cryogenics would be as a refrigerant for an oscillating flow cycle like a sterling or pulse tube cryocooler these typically use helium as a working fluid but it's a non-renewable resource and very difficult to get in some countries it can also replace helium in balloons or blimps which has never gone wrong except for that one time aside from that one incident it's pretty great in fact it's even more efficient than helium as a lifting gas and in chemistry there's a seemingly endless list of reactions hydrogen takes place in I originally tried doing this the dirty Way by dissolving aluminum and sodium hydroxide and it does work but it's quite a bit more costly per unit volume of hydrogen and after getting blasted in the face with sodium hydroxide solution when my reactor tank exploded I decided look into a different method industrially the most common way of producing hydrogen is with superheated steam and methane flowing over a platinum Catalyst which then breaks up into hydrogen and CO2 considering the price of platinum I don't see myself doing that anytime soon that just leaves water electrolysis as the only reasonable approach typically the way this is done is with a stack of plates sandwiched together with a whole bunch of bolts to hold them tightly in place and some sort of membrane material to keep the two gases from mixing if you read research papers on the subject they're usually using some ridiculously expensive fancy polymer membrane but you really only need something like rip stop nylon which is porous enough to allow conduction but the holes are small enough that the little gas bubbles can't leak across it problem is every time I try to do the typical sandwich method the gas gets leaked and attempts I made with 3D printed cells also leaked and let me tell you a solution with a pH of 13 is not a pleasant thing to have leaking all over the place then I got another idea which should theoretically be leak proof and trap all the hydrogen that's produced until it's ready to be moved elsewhere after watching my dog drink from his upside down water bowl thing I realized that would be a really useful geometry for a hydrogen generator cell the cathode would be placed inside of a glass Bell and the anode would be placed on the outside so the electrodes would be concentric then the whole thing would be in a larger glass or plastic bowl full of the electrolyte the wall of the glass Bell would prevent the gas bubbles coming off the electrodes from mixing since they're always traveling upwards due to the buoyancy then a tube would be placed inside the the Bell that goes all the way up to the top which I'd suck all the air out of allowing the Bell to be completely flooded while the outside water is still just open to the atmosphere without any seals of course this tube would need a check valve on it to ensure gases could only flow out otherwise air would backflow into the bell and push the water line inside of it back down as the hydrogen accumulated the water line inside the Bell would be pushed down which would allow me to see the exact volume of gas that had been produced of course as the water line of the Bell moves down from a ulated hydrogen the water line of the bull would move up since the water is loaded with sodium hydroxide it's very conductive so I could simply use a pair of smaller electrodes to detect when the water level reaches a certain height and trigger a small pump to pull the gas out of the Bell via the tube I think it's a solid idea in theory but let's see if it actually works in reality to mount the cathode I made this ring thing which will support the glass Bell in the middle and has arms on the outside to mount the anode then the whole thing will live inside this tupperware bowl I kept the lid but it's not there to seal anything off it's just there to act as a baffle to keep the nasty salt spray from jumping out of the water which tends to happen with an open container undergoing electrolysis the electrodes are 015in thick strips of 316 stainless steel this material won't last forever like Platinum but it should last several hundred hours at the time of making this video I've put close to 100 hours of runtime on my cell with only slight discoloration of the electrodes the cathode sheet wraps around the fixture and has a narrower thicker strip of stainless steel to connect it to the outside world the strip has some heat shrink on it to prevent unwanted electrolysis from happening on its surface here you can see how it wraps around the bottom of the glass then the Rings for the anode are screwed in place these screws are also 316 stainless in retrospect I could have just welded these pieces of plastic together with a soldering iron then I screw on the anod sheet then install this little bracket thing in the middle which will serve as the base for mounting the little vacuum tube for extracting gas from the cell I use silicon C instead of Superglue to attach everything because it seems to hold up well in a high concentration of sodium hydroxide let's try pulling vacuum on the Bell the sudden bubbling is from the water line on the outside dropping below the bottom of the bell and letting a bunch of air in so the cell needs more water in it so here's the bell with all the air removed from it I didn't get very far into testing before all of my 3D printed Parts started to crumble and it was at that point I learned that pla will dissolve in sodium hydroxide so all the parts had to be reprinted with something else a friend of mine reprinted all the parts in ABS which I didn't have at the time and the cell was rebuilt after a couple of days here's the leads for the new cell as you can probably tell I'm expecting to pull a lot of current which leads to an important question how do you predict how much current you're going to pull with electrolysis after a little bit of Googling I found this Nifty chart that gave conductivity for a bunch of different solutions based on electrolyte concentration let's look at sodium hydroxide the chart says that at 5% concentration we'll get a conductivity of 206 Ms or 206 CS per centimeter a cver is the inverse of an OHM so for example one volt at five Cs would give 5 amps one volt at 10 CS would give 10 amps 2 volts at 10 CS would give 20 amps and so on and so forth the per centimeter part is area over distance in other words two 1 cm squar plates that are 1 cm apart and a 5 % sodium hydroxide solution would give 026 cevers so in theory that's a little over 1 amp at 5 volts however when it comes to electrolysis there's one more factor in that equation which I'll talk about later but first I did my own test to verify the numbers from the chart after all you shouldn't just believe everything you read on the internet to do this I made a small test fixture that had plates of a known area and distance and tested them with my power supply and various concentrations of sodium hydroxide the results I found were pretty consistent with the chart save for one very conspicuous difference the solution didn't start conducting for any concentration of electrolyte until about 2 volts so the simple Assumption of IAL V / R isn't valid for electrolysis instead the equation would be IAL vus V threshold over R according to the Wikipedia article on water electrolysis this threshold voltage is theoretically 1.23 volts at room temperature but in practice it seems to be somewhere between 1.8 to 2.0 volts okay so that's how to estimate current but what about gas production rate a mole of water takes about 287 K of energy to separate at room temperature the hourly production rate of gas would be the threshold voltage times the current time 3600 seconds for an hour divided by 287,000 this gives moles per hour at room temperature a mole of ideal gas occupies about 24 l so multiply that number by 24 and you get lers hour of gas output this is the production rate of hyd hydrogen but the production rate of oxygen would be exactly half of that if you're building a cell you may be tempted to just crank up the voltage to increase the current and this would certainly increase the gas output problem is it's also reducing the efficiency of the cell and dramatically increasing heating if you had 12 volts and 10 amps going into a cell 10times threshold voltage or about 20 watts would be going into electrolysis and the remaining 100 watts would be going toward heat also increasing the temperature increases conductivity of the solution which would cause even more current draw and an eventual thermal runaway this is why electrolysis is typically done with a constant current power supply rather than a constant voltage Supply if it is done with a constant voltage Supply designers typically try to keep the voltage as low as possible above the threshold to maximize efficiency and minimize heat in industrial devices usually each cell is somewhere between 2.2 to 2.5 volts based on my cad design I expected to have nearly 100 cm of conduction area so at 5% sodium hydroxide that would result in 18.7 cevers or 53 milliohms however with the glass Bell blocking part of the path that number would be a little bit lower originally I planned to use a 3.3 volt supply for the cell but I wanted a little more output so I just got a 5volt supply instead I figured if the cell began to overheat I'd just dilute the electrolyte a little bit so it wasn't quite as conductive based on these numbers I should get 56 amps with a 5vt supply but again the glass wall would reduce conductivity somewhat and voltage drop across the leads would reduce the current somewhat too I figured it would realistically be more like 20 to 30 amps so I printed some extra widgets and started to mount all my equipment on a wooden board here's the 5volt power supply vacuum shut off valve vacuum pump current meter and a gatorade bottle serving as a liquid trap in case the pump pulled too much gas out of the bell and started sucking out the electrolyte I also got this 12vt wall wart to run the pump and extra dude ads which I repackaged into this 3D printed box here's a look at the the full system I originally had a 1 mohm shunt for current measurement but it was grossly inaccurate so I replaced it with this hall effect sensor instead I also added a little fridge compressor so the hydrogen could be stored in a tank Under Pressure once it was removed from the cell I did a couple of test runs but found that the hydrogen was contaminated with oxygen when I did ignition tests it's a little bit hard to tell from the audio in this video but those bubbles went off with a pretty sharp bang rather than the lazy sort of whoosh sound you get if it was pure hydrogen turn turns out some of the gas bubbles from the anode were migrating across the Gap because part of the anode sat below the bottom of the glass Bell the anode needed to be moved higher so that none of it hung below the bottom of the glass to do this I just added some extensions onto the printed arms that hold the anode rather than attempting to use glue that might react with the sodium hydroxide I just used my soldering iron to weld the ABS Parts together which actually worked pretty well fortunately I had plenty of head room in the tupperware bowl and my anod still fit inside with the lid on this this time when I did an ignition test on the gas there was no bang whatsoever just a lazy flame so it looks like the hydrogen is pretty pure now starting at room temperature the current sensor reads 25 amps so right about what I expected the output from the power supply is 5.21 volts and the voltage across the cell is 5 volts even so there's a 21 volt drop across the leads which is a little over 5 Watts at 25 amps that's not too surprising since the leads get noticeably warm here's a closer look at the salt spray I mentioned ear earlier even without any boiling or big bubbles or high temperature the microbubbles can launch themselves several inches out of the water when they hit the surface which is why the water has to be covered with some sort of baffle and tubing extracting the gas has to have a filter on it the gas still seems to be pretty pure so now it's time to add a little bit of automation to the cell so I don't need to babysit it constantly to do this I used an Arduino with a little breadboard Shield I built a circuit on top of the board connects to relays that control the 5vt power supply and compressor and a m fet that controls the 12vt vacuum pump a pair of stainless steel screws are mounted to the lid of the cell when enough gas accumulates in the glass Bell the water line inside the outer portion of the cell Rises high enough that it contacts the screws this has the effect of closing a switch that causes a transistor to pull down one of the digital pins on the Arduino when the Arduino has read a low State on that PIN for one second it kicks on the vacuum pump for 3 seconds which transfers gas into a beach ball or balloon if the electrodes are triggered for more than 10 seconds the program assumes something has gone wrong and it goes into a so-called panic mode and shuts everything off the only way to clear the panic mode is to power cycle the entire device there's also functionality and wiring meant for a switch to detect when the beach ball or balloon is full and turn on the compressor but I never got around to actually setting up a physical fixture for that here's a time lapse of the cell filling up a latex balloon you may notice that over time the current is going up that's no error as I mentioned earlier higher temperature will result in higher conductivity of the electrolyte here's a graph of the temperature versus time after 3 hours of running the electrolyte reaches nearly 60c and here's a graph of amperage versus temperature at room temperature we start off just a hair above 25 amps but at 60c were over 40 amps fortunately I didn't get any thermal runaway because the cell lost enough heat naturally and never really got above 60c but it's not a great idea to run this cell at 60c for a long time because the ABS parts are going to be fairly soft at that temperature anyway after 1 hour my balloon started to float a little bit and after 2 hours it had no problem holding up the fill adapter and tubing when I zero my scale with slack on the tether and then release the tether I get minus 22 G which is the lift it's producing all right so far I've got a cheap and dangerous replacement for helium to fill party balloons but to fill something bigger I'm going to need a way to store a lot of hydrogen I originally got a 10g steel tank for this purpose but then I read that a phenomenon known as hydrogen Emitt can cause the steel to crack and fail this seems to be the result of those pesky little hydrogen atoms being small enough to Tunnel their way through the lattice of iron atoms I read that aluminum is far less affected by this issue but my aluminum tank was currently being used to hold the ethylene for my cryocooler project so I evacuated my steel tank then set up a hose to equalize the pressure between the steel tank and the aluminum tank once the tanks were equalized I used my trusty compressor module to force the remaining ethylene to the steel tank afterward I removed any Trace Amounts of ethylene left over with a vacuum pump supposedly another thing that exacerbates the hydrogen embrittlement problem is the presence of moisture that's a problem because the gas coming out of the cell is extremely humid because you know it's literally coming out of water so I'm going to add this bottle full of silica gel in line with my pump output to dry the hydrogen just to show that it works I have a little humidity meter inside this inverted tupperware box the humidity starts off a little over 40% and when I blow into it the container fogs up and goes close to 80% now I'm going to blow through the drier bottle and we should see the humidity inside the container drop and there you go I think the humidity actually went close to 0% but the meter is probably pegged at around 10% so hopefully this will help mitigate the embrittlement problem so after spending a weekend running the cell I had enough hydrogen to fill this 10g tank to 125 psi which translates roughly to about 320 L of hydrogen the cell puts out about 15 to 20 lph depending on the temperature of the electrolyte to fill a much larger balloon I've made this adapter with a chunk of PVC pipe and some 3D printed bits 320 L of hydrogen is enough to generate about 340 G of lift which is close to a pound so let's strap this GoPro to the balloon and try to catch the sunset with it not a bad view but I definitely need some stabilizer fins if I ever want to do aerial photography from a balloon a drone might be easier my string was also way too thick which limited my altitude I think I made my point though when the flight was over I removed the clip from the Balloon Nozzle and recovered the hydrogen back into my tank for later use so I think that's a pretty good demonstration of what's possible with a little tabletop electrolysis cell I think there's a lot of ways I can make this device even more Compact and energy efficient but for now I'm pretty happy with it I didn't originally intend to do anything with balloons but after flying one with hydrogen I made I kind of want to try launching one of those high altitude weather balloons or even have my own RC Zeppelin like that guy who made an RC model of the USS Min that actually floats I used to build and fly RC planes and drones but something about lighter than airflight seems so much more interesting even if it's less practical anyway there's one more thing I need to mention about electrolysis if you're using stainless steel electrodes they'll last for a reasonably long time but not forever over time they'll release various chromate salts into the water which are bad for your health some of these could even have hexavalent chromium which is particularly nasty so if you have to get rid of your electrolyte after hundreds of hours of use don't dump it down the drain put it in a bucket let the water evaporate then collect the precipitate in a plastic bag and drop it off to a toxic waste disposal site or stash it away in a government Warehouse anyway thanks for watching

Channel: Hyperspace Pirate

Views: 807,621

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Id: oIWgzVaGn4Y

Length: 17min 20sec (1040 seconds)

Published: Wed Oct 04 2023