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May 22, 2014, 09:39 AM
Go small or go home
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May 22, 2014, 04:01 PM
Potential Future Has-Been
Originally Posted by Navigaiter
Yes, that's true. That's stating the challenge without answering it ;=]
How does one mechanically separate the O and H2 gas products? The answer will require a sketch.

cheers! Allen Navi
They are already separated, you just have to keep them that way

Something like the image ruzam linked to could be made pretty easily using PVC pipe fittings. The real challenge is getting enough gas output when using the electrolysis method. You need to make your electrodes so that there is as much surface area as possible, then you need a DC power supply with some high current capability. The guys making HO generators for their cars use stacks of plates sandwiched together with insulated spacers in order to maximize surface area in a small space, then use the cars battery as the power supply. Car batteries can source a lot of current, so they work good as long as they are in a moving car that is constantly recharging them. For a garage operation you would need a comparable DC power supply.

Geez, now I want to go build one myself!
May 22, 2014, 05:15 PM
Potential Future Has-Been
I think one problem with that separate chamber design is that the long distance between the anode and cathode is going to diminish the output. The guys making the car HHO generators are keeping the anode and cathode as close together as possible. A common design involves alternating plates in a close stack, with each plate alternating between anode and cathode. Of course with that kind of design you would never be able to keep the H and O separate because they instantly mix upon bubbling off the plates.

The fastest way to generate hydrogen is going to be one of the chemical methods. Hydrochloric acid is very cheap and can be had for just over $1 a gallon at pool supply stores. It will produce hydrogen very rapidly when mixed with zinc metal. You would just need to use a cooling bath to dissipate the heat and also some kind of filter in the output line to scrub the HCL fumes. The metal would be the expensive part. Pennies dated after 1982 are actually zinc on the inside (97% zinc by weight), so you could file the edge to expose it and get zinc that way. Of course it's illegal to destroy currency, so don't let anyone see you doing it and bury the hollow copper shells when you are done
May 22, 2014, 05:37 PM
Go small or go home
ruzam's Avatar
Galvanized hardware is zinc plated (or dipped). Grab some outdoor fence bolts from the local hardware. The lumpy rough ones are hot zinc dipped (thick coating). Depending on your sources, that could be a cheap supply of zinc. I used to rip apart alkaline batteries for the case, which is just a big can of zinc. I don't know if that's as easy to do with today's batteries. The local metal recycling also has zinc for sale by weight.

I would think that hydrogen as a gas would simply float above the heavier oxygen. Even though they're mixed together, they're not joined (or you'd be back to water or something). So you should just be able tap off the top of a tall column. Of course, you'd never know where the hydrogen ends and the oxygen begins...
May 22, 2014, 08:17 PM
Potential Future Has-Been
I think pennies are going to be the cheapest source of zinc. Using pennies, your cost is $1.87/lb . While the commodity price of zinc currently sits around $1/lb, anything you buy made of zinc will have a bunch of other costs added onto it like manufacturing, marketing, shipping etc. One way to get large chunks of pure zinc is to buy some zinc anodes used for boating. has tons of them. The cheaper ones will be the very basic shapes like just a square block, which you can get for about $3.63/lb for a 10lb slab. Not as cheap as pennies, but a lot easier to use since you don't have to modify it in any way.

Now if I could just remember what I learned 25 years ago in chemistry class I'd be able to figure out just how much hydrogen could be generated per pound of zinc and how much hydrochloric acid is required to consume one pound of zinc. Then the cost of making your own hydrogen could be determined and compared with the cost of helium.
May 22, 2014, 10:11 PM
Potential Future Has-Been
So I attempted some stoichiometry using the following reaction:

2HCL + Zn => ZnCl2 + H2

This is what I calculated:

One pound of zinc (453.6g) is fully consumed by about 505.9g HCL
506g HCL and 453.6g Zn will produce 14.29g H2
H2 has a density of .08988 g/L, or 2.545g per cubic foot
Thus you get 5.6 cubic feet of hydrogen from one pound of zinc.

HCL comes in different concentrations, with 38% being about the max you can find. I don't know what concentration pool acid is, but I don't think it is that high. But if it was, the density of the HCL is 1189g/L, or 4504g per gallon. So one gallon would allow you to dissolve 8.9 pounds of zinc, giving you a total of 49.8 cubic feet of hydrogen.

So at $3.63/lb for the zinc and lets say $1.50 for the HCL, you wind up paying $37.80 to make about 50 cubic feet of hydrogen, or 75 cents per cubic foot. If you want to use pennies instead of boat anode zinc, you can get it down to 36 cents per cubic foot, but then you'd have to scrounge up about 1665 pennies for every 50 cubic feet of gas you needed!

What is helium selling for these days? I saw 73 cents per cubic foot quoted online for a 240 cf tank fill, so unless you can get zinc really cheap there does not seem to be much cost savings in going through all this trouble. The electrolysis method would probably cost you even more in electricity costs and you'd have to wait a month for a 200 cf envelope to fill due to how slow the gas output is. Commercial hydrogen production uses very different methods than what you can do in the garage.

Last edited by pyronaught; May 22, 2014 at 10:35 PM.
May 26, 2014, 11:14 PM
coriolan's Avatar
Wonder if Jak_o_Shadows is still experimenting with hydrogen
Jun 09, 2014, 10:06 AM
Registered User
I'm here to say my sincere congratulations! You're committed to making an electrolyzer which is a most important part of any affordable and operating personal blimp because helium is simply too expensive for personal flight usage.

The Zepelins had a million passenger miles flying from Europe to South America and also around the entire world WITHOUT HAVING ONE FIRE BEFORE THE HINDENBURG ACCIDENT. H2 is a fuel and needs a specific range of oxygen mixing before it can burn. A plastic bottle full of pure H2 cannot, not, spontaneously combust.

I think that maybe TUNGSTEN would make a fairly durable electrode since it lasts so long in white hot temperatures of an incandescent light bulb. Those bulbs are still available, why dont u try one? Just break the glass envelope off and hook to the tungsten filament inside.

Old style carbon batteries, D cells, have pure carbon rods as the positive, center electrode. Don't l;et the acid get on anything when you take one apart.

Oh, also try stainless steel electrodes. The nickel in it makes it more inert than steel. All stainless steel isnt the same, learn which 'type' has the most nickel in it.

I want to build one of these electrolyzers myself when i get back from vacation in a month. Keep us posted and don't give up. aND DONT LET ANY AIR TOUCH UR HYDROGEN!!! ISOLATE IT AT ALL TIMES.
Jun 09, 2014, 10:27 AM
Registered User
Regarding the costs to make H2 at home:
Thanks for doing the math on the chemical method and showing its out of the question since a personal ultralight airship will require 250 cubic METERS of H2 to lift itself and its payload, a combined weight of 250 kilograms. [ultralight regs say the ship alone cannot weigh more than 254 pounds. with a 250 pound payload of pilot and miscellaneous equipment, thats 500 pounds total weight, about 250 Kg]
I've lost my figures but they showed that an electrolyzer at 50% efficiency would require $350 to $500 in household retail electricity at the national average of 12 cents a kilowatt to make 250 cubic meters of gas. Would anyone else like to try that calculation.?? Home made electrolyzers will vary WIDELY in output efficiency.

Solar panels are getting cheep! They're now under a dollar a watt. This might prove the way to go for electrolyzer power.
Jun 09, 2014, 12:09 PM
Potential Future Has-Been
The main drawback with the electrolysis method is the slow speed of production. You would have to have a very large operation to get your gas produced in a reasonable amount of time.

The Japanese used on-site chemical production to fill their 10.5K cubic feet hydrogen balloon bombs during WWII. This required caustic soda and ferrosilicon in the formula listed here:

2NaOH + Si + H2O -->Na2SiO3 + 2H2
Last edited by pyronaught; Jun 11, 2014 at 09:44 PM.
Jun 11, 2014, 05:40 PM
Registered User
Slow is ok as long as its clean, like electrolysis is.
I tried the simple chemical process of putting aluminum foil into a jar of hydrochloric acid and yuch!
It was slow and didn't produce much gas but got boiling hot. It left a black sludge in the jar. Hot slow and dirty.
If i make an electrolyzer it'll be from pvc 50-gallon drums which i can b uy used for $20.!! Then i'll figger out how to make stainless steel electrodes that also separate the two produced gasses, H2 and O.
I mite try running 5 or 6 at the same time for faster output. cheep and clean make slow real keen.
Jun 11, 2014, 06:28 PM
Go small or go home
ruzam's Avatar
Aluminum foil is not zinc. That is why you got hot, slow and dirty.
Jun 11, 2014, 09:40 PM
Potential Future Has-Been
Yes, you got the aluminum + sodium hydroxide method confused with the zinc + hydrochloric acid method. You need sodium hydroxide for the aluminum method:

2Al + 2NaOH + 6H2O → 2NaAl(OH)4 + 3H2
Jun 12, 2014, 10:57 AM
Registered User
I'll try it again soons i find enough beer and soda cans. :+}

I'd still rather use the electrolysis method if someone had a neat idea on how to separate the outgassing from the two electrodes. The problem is they have to have large surfaces and be very near each other!
Water is a resister , even with added electrolytes, and when you're pushing amps thru resistance, your efficiency goes down while you heat the medium.,

Jun 13, 2014, 12:02 AM
Potential Future Has-Been
I think soda cans might be problematic since they have some kind of coating on the inside and paint on the outside that is going to block contact with the acid. Which is a shame, since they are such a convenient source of free aluminum.

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