Hydrogen Extraction

Orianna2000 · Oct 22, 2012

If someone has a primitive hydrogen extraction setup using a fish tank and some electrodes, how quickly does it work? Is this something where she can leave overnight and return the next morning to collect the hydrogen? Or does it need to be monitored constantly? Would it automatically stop once all the hydrogen in the water is extracted and basically be on standby until she adds fresh saltwater to the tank?

I'm just trying to figure out if she can only do activate the process while she's in the lab, keeping an eye on it, or if she can set it to extract while she's away and then come back the next day to siphon the hydrogen off into tanks.

The character is a university aide who's filling canister after canister of purified hydrogen gas for her science professor, who (unbeknownst to her) is using the hydrogen to fuel his spaceship.

Torgo · Oct 22, 2012

I think the rate of electrolysis depends on the amount of current through the water. I think a fishtank setup with a lab power supply, rather than an industrial system, is going to be sloooow.

Some Google Answers page I found in a tea break suggests that converting 1 gallon of water to hydrogen takes 16.5 kilowatt-hours of energy. That's kind of a lot for anything other than an industrial setup.

I think you'd end up with Horrible Explosion Danger as well.

Your fishtank will need to be huge given that the hydrogen is going to take up about a thousand times as much volume as the water, at one atmosphere. I do not believe this is a particularly plausible scenario, basically. The best way to get hold of a bunch of hydrogen is probably to buy some through a lab supplier - I mean, it'll be easier to embezzle hydrogen than to explain the colossal electricity bills and explosions.

Orianna2000 · Oct 22, 2012

There's a reason they're extracting the hydrogen themselves. He's an alien, (an honest alien who refuses to steal anything) who's crash landed in a country that's on the brink of war with the rest of the world. He can't risk anyone finding out he's an alien, and it's taking him several years to repair his ship anyway, so it's okay if the hydrogen extraction takes a long time.

The dangers involved are addressed in the story. I just need to know how long it will take to extract a good-sized fish tank, and whether it can be left alone while it's percolating, so to speak. I don't want the lab to explode while she's at home sleeping!

Drachen Jager · Oct 22, 2012

If it was set up right, it could be left alone just fine.

You wouldn't run the fishtank dry, it would make more sense to keep adding water as the rest left.

With a decent source of electricity he could manage a whole fishtank of water in a few days or weeks. It takes time, but it's not an incredibly slow process.

An explosion would be easy enough, all you need is a leak and a spark.

blacbird · Oct 22, 2012

With salt water, you're going to be producing mainly chlorine gas, from the dissolved chlorine ions, and at the other end, producing a solution of lye (sodium hydroxide). I've done this, as a kid, with a chemistry set.

Electrolytic separation of H2 from H2O requires much much greater electrical energy, which is why it isn't done on a huge industrial scale: far too inefficient, and uneconomical.

caw

waylander · Oct 22, 2012

As Blacbird correctly says, you need pure water for this with minimal dissolved salts.

Orianna2000 · Oct 22, 2012

Huh. My research had said to use salt water. Or maybe my father told me that, now I'm not sure. Either way, I'll change it to fresh water. Thanks!

spottedgeckgo · Oct 22, 2012

Fresh water isn't going to work well either. I think what they meant to say is that you don't want table salt (NaCl) when producing a large amount because chlorine gas will dissociate. I think sodium hydroxide (NaOH) is the preferred method if you are worried about chlorine gas. A 12V power supply running at 1 amp will fill a test tube in a couple hours. Using a soda bottle and a higher amperage, you could leave the thing on there overnight, no worries, but you a still making a very small amount of hydrogen.

Cathode and anode need to be plated with a non-corrosive like gold or platinum to keep them clean, as corrosion will slow the process considerably. Electroplated wire-mesh screens work well.

Depending on the tank size, especially if you aren't compressing the gas directly from the collection tanks, the water inside the tank will refill your reservoir faster than it empties from H2 and O2 production, so in essense, you only need check the water level at the start of each cycle. If anything the fish tank runs a higher risk of overflow than depletion.

Vaulted · Oct 22, 2012

I think if you want to launch a spaceship you will need an awful lot of hydrogen.

spottedgeckgo · Oct 22, 2012

I agree with Vaulted. I don't want to tell you how to write your story, but He3 might be a better propellent (very hard to come by on earth except in laboratories).

benbradley · Oct 22, 2012

Orianna2000 said:
If someone has a primitive hydrogen extraction setup using a fish tank and some electrodes, how quickly does it work? Is this something where she can leave overnight and return the next morning to collect the hydrogen? Or does it need to be monitored constantly? Would it automatically stop once all the hydrogen in the water is extracted and basically be on standby until she adds fresh saltwater to the tank?

I'm just trying to figure out if she can only do activate the process while she's in the lab, keeping an eye on it, or if she can set it to extract while she's away and then come back the next day to siphon the hydrogen off into tanks.

The character is a university aide who's filling canister after canister of purified hydrogen gas for her science professor, who (unbeknownst to her) is using the hydrogen to fuel his spaceship.

As others have mentioned, electrolysis works, but is energy-intensive and thus expensive compared to some other known methods. Perhaps the aide or the professor could look at the Wikipedia entry to find that a more efficient way to make industrial quantities of hydrogen. It appears steam reforming is The Way, but with the extra-high temperature and pressure it surely takes a much more expensive setup than electrolysis. If making and operating the lab apparatus is too complicated (I'm guessing it might be), maybe the professor could set up some shell company that could make a legitimate-looking purchase of the needed hydrogen.

spottedgeckgo said:
I agree with Vaulted. I don't want to tell you how to write your story, but He3 might be a better propellent (very hard to come by on earth except in laboratories).

You're assuming the hydrogen would be used as a fuel for fusion, which I wasn't even thinking of. I was thinking of hydrogen and oxygen being combined in a regular chemical rocket engine (I forget what is commonly used in liquid-fuel rockets, but I know hydrogen and oxygen will work). Orianna2000, which of these (if either) did you have in mind?

spottedgeckgo · Oct 22, 2012

actually I wasn't really thinking of either. Hydrogen fuel rockets are what is typically used here on earth. Fusion would require less to do the same amount of work, depending on the spaceship. He3 is a new futuristic fuel (don't remember the exact apparatus), but essentially, it's thought to be very clean and efficient. Only problem is finding the He3, cause it's kind of expensive here on earth, but in space you can find it pretty much everywhere and it's fairly easy to harvest. I'm thinking space aliens that know how to squeeze the max efficiency out of it would not require nearly as much. Of course, if they could use fusion efficiently all they would need is water.

OP, I'm gonna do a quick search and see if I can find you a better way of getting hydrogen, if something turns up I'll post it.

spottedgeckgo · Oct 22, 2012

You could try this:

http://en.wikipedia.org/wiki/Sulfur-iodine_cycle

I'm sure the alien will have some suitable materials on his spaceship? A small apparatus will still take a long time here on earth, but the idea of building something like this at a polar region of a hot planet like mercury would mean cheap hydrogen for an advanced species. Kinda like their version of gasoline. Makes sense and workable. Hope this helps.

blacbird · Oct 22, 2012

spottedgeckgo said:
He3 is a new futuristic fuel (don't remember the exact apparatus), but essentially, it's thought to be very clean and efficient. Only problem is finding the He3, cause it's kind of expensive here on earth, but in space you can find it pretty much everywhere and it's fairly easy to harvest.

Well, that's not quite the only problem. We haven't made even elementary technical progress on harnessing fusion reactions in any useful way other than hydrogen bombs. As far as "find it pretty much everywhere and it's fairly easy to harvest" goes, I'd like to hear your methods for doing both the finding and the harvesting. I don't know of any place where we've actually confirmed the "finding" part, let alone the "harvesting" part.

I'd go for dilithium crystals or beryllium spheres, or something similar.

caw

spottedgeckgo · Oct 22, 2012

You got me blacbird, it's in the infancy stage here as a fuel source, but I think there are working prototypes, but it's not fusion, it's something else.
As far as finding it, gas giants like neptune are theorized to have a significant amount in the atmosphere, and it can be harvested by a "weather balloon" type of module that will collect the atmosphere and sort the He3 out by weight. If space flight was a secondary issue, these little balloon extractors could work as fuel depots. Theoretically, of course, this is just from reading the PR from scientists, not their actual schematics and patents, so take it with a grain of salt. Seems logical though with the progress we've made, a more advanced race would be able to readily use it as a fuel source.

RichardGarfinkle · Oct 23, 2012

He3 is desired as a fusion fuel. Here's a little bit on it from Universe Today.
http://www.universetoday.com/83830/helium-3/

Note as an isotope of Helium, which is a noble gas, He3 is only useful in atomic reactions (particularly fusion) since it does not take part in chemical reactions.

As to the OP. Hydrogen extraction from fresh water is fesable (it can be and is done in school chemistry classes as a demo of electroysis). But large scale would take time.

If it's for a fusion reactor there are actual technical difficulties since Hydrogen fusion is better done with deuterium and tritium (heavy and heavy-heavy hydrogen), but that can be glossed over with alien tech.

ClareGreen · Oct 23, 2012

Have you looked into hybrid rockets? Less volatile than pure hydrogen and easy to fuel without attracting too much attention.

jaksen · Oct 23, 2012

You don't extract H from water - you decompose it. H is part of the water molecule, so once you get all the H 'out' of the water, there is no more water. All you have is H and O.

And a tiny amount of H can make a BIG explosion. A Coke bottle full of H, lit with a match, can shatter the bottle and send glass flying everywhere, as I have done myself in front of a science class. (With a plastic barrier between me and the class and everyone in goggles. Did it once; never did it again.)

An easier way to get H gas is to use HCl* and combine it with small amounts of zinc. The gas which bubbles off, and can be collected with a plastic tube, then run into a bottle, will be pure Hydrogen. Of course, again, a small spark and BANGO, it's the Hindenberg zeppelin all over again.

*Hydrochloric acid, which is a dangerous liquid, too, and I used very small amounts in tiny bottles. Put a few drops over a small piece of zinc mossy. The gas collects in another, small test tube. Light with match and a loud POP! Loud enough for neighboring classes to look into my classroom and say wth are you guys doing in there? My students would laugh and scream and do it over and over and over. (With everyone in goggles and lab aprons; small amounts of HCl only.)

I was the only teacher at my junior high who would even dare do this with a class of 12 year olds.

Orianna2000 · Oct 23, 2012

I'm not a scientist by any stretch of the imagination, and it's been a few years since I planned out this novel, so I don't recall how I came to the conclusion that hydrogen was the way to go. Quite honestly, I don't know how the professor's spaceship works. He crashed on a planet that's close to 1930s level of technology, so he's got limited means to work with. Quite likely, someone at the NaNoWriMo message board (several years ago) suggested hydrogen as being the most likely fuel source that he could whip up in the science lab. If anyone has any alternatives, I'm willing to hear them.

I looked up the sulfur-iodine process, but the article said it involves temperatures up to 1,000 degrees Celsius and that's not really feasible in a university's remedial science lab. I need something he can do on the sly, something that's easy to set up and wouldn't raise any red flags if someone walked in and saw it.

Basically, his spaceship crashed on this planet and he's been totally rebuilding it, using limited means and resources. He's been working at it for several years when the story begins, but he's a patient fellow and in no hurry to go back home.

I did just read something about using pellets of aluminum and gallium in water to produce hydrogen, but I have no idea if that's feasible or not. I did mention in the novel that the professor is trying to produce a certain chemical reaction by combining local elements, but since he doesn't know what all the local elements are, he's been testing them one at a time, and since there are probably a few million permutations, it's taking forever. Perhaps he's trying to find a more efficient way of producing hydrogen? Like, say, with aluminum and gallium? Perhaps I could have him succeed halfway through the book, which would greatly speed up the hydrogen extracting process. But the article on extracting hydrogen using those elements said something about it only producing hydrogen "on demand." Basically it would be used in a car engine, producing fuel as the car needs it, instead of storing it in a tank. Not sure how that would work, considering we need to store the hydrogen so that he can fill his ship's fuel tanks. Is there a way around this? Or should I consider something else?

As I said, it's been so long since I researched this novel, I don't remember what options I considered and why I eventually chose hydrogen as the spaceship's fuel source. If anyone has any alternatives that can be produced easily, cheaply, and in a basic science lab, I'd be happy to consider them.

FOTSGreg · Oct 23, 2012

You might take a look at methane. Mother Earth had articles on home methane production and storage several decades ago. It's a bit more stable than hydrogen, liquefies or freezes at higher (though still extremely low) temperatures, takes up less volume, is much more easily produced, and can be easily converted to a high energy fuel source by mixing it with an oxidizer (maybe something like hydrogen peroxide - one of the chemists here can check my imagination I'm sure - liquid methane plus hydrogen peroxide=highly energetic event, right?).

WriteKnight · Oct 24, 2012

Hydrogen gas was generated in the field to fill observation balloons during the civil war. This link will help you understand what can be done.

http://www.thaddeuslowe.name/CWgenerators.htm

"On the top of the tank there was a hinged metal plate that allowed the metal filings to be deposited inside. Also on the top, located near the middle, was a funnel-shaped copper pipe where the undiluted sulfuric acid was poured. On the end opposite the filler plate there was a copper "escape" pipe that allowed the hydrogen to flow into a large rubber hose. The rubber parts for the generators were supplied by Goodyear's Rubber, Belting, and Packing Company of Philadelphia."

" Barring accidents, and when handled by competent men, the whole process from the time of preparations to the completed inflation of one of the larger balloons was approximately three hours. Normal inflation of a balloon in the field, Lowe wrote to General Hooker's adjutant general in March, 1863, "never required over three hours and fifteen minutes, and since adding my last improvements ... the gas makes in two hours and thirty minutes."

NOTE: Generating enough Hydrogen gas to lift a balloon can be done quickly - but it's a VAST AMOUNT of Hydrogen - highly explosive - and needs someplace to be stored. It's not near enough to power a spacecraft - at least not a chemical reaction engine.

The resultant residue is toxic and must be disposed of. So separating hydrogen from water is cleaner, and slower - you're still left with finding some place to store what is basically a water tower sized volume of Hydrogen. UNLESS you are liquifying it - which is another problem, and requires more equipment. In short - you've pretty much painted yourself into a corner in terms of doing this on the sly - and hiding the storage volume in a safe manner.

Orianna2000 · Oct 24, 2012

No, I had plans for how he would get away with all this. His spaceship repairs are being done deep in the woods outside of the city, where no one ever goes. He found a cave where he's storing the hydrogen in canisters. He just has to worry about the occasional hiker, and he's got a setup to keep them from wandering into his camp: subliminal fields that nudge you away, so without even realizing why, you're walking away. Keeps them from entering the woods where his stuff is being stored.

WriteKnight · Oct 24, 2012

Right. My point being - there is a simple way to generate LOTS of hydrogen quickly. But storing ENOUGH to pilot a ship - in gaseous form - is going to take the entire cave and then some. Think of the size of a dirigible or blimp. A chemical reaction engine, is going to need the volume of SEVERAL, perhaps DOZENS of blimps.

You need to LIQUIFY the gas. That's another tech problem. Compression, liquification, storage. Maintaining the liquified hydrogen.

Unless you use the very special alien 'hydrogen compression flux capacitor' that somehow magically compresses and liquifies the hydrogen - you know, it survived the crash and all.

Orianna2000 · Oct 24, 2012

It shouldn't be too difficult to have him jury-rig something that can liquify the hydrogen, if that's a necessity. Or I can say that the hydrogen is only part of what the ship needs, that it actually runs on a combination engine and the other half of the fuel is something easy to procure, like salt water, or oxygen, or something. That way he doesn't require nearly as much hydrogen. Would that work?

blacbird · Oct 24, 2012

Orianna2000 said:
It shouldn't be too difficult to have him jury-rig something that can liquify the hydrogen, if that's a necessity. Or I can say that the hydrogen is only part of what the ship needs, that it actually runs on a combination engine and the other half of the fuel is something easy to procure, like salt water, or oxygen, or something. That way he doesn't require nearly as much hydrogen. Would that work?

The energy to be obtained is directly dependent on the amount of material used in the chemical reaction. Hydrogen by itself is useless (except in a fusion reactor). It requires being combined with something else, most probably oxygen, to release the chemical energy.

As for "jury-rig something" to liquefy hydrogen: Hydrogen liquefies only at very cold cryogenic temperatures, and would require storage under great pressure at these low temperatures. How you "jury-rig" a device that could do that is maybe a bigger obstacle than just inventing a magical rocket fuel.

There's a reason nobody has ever tried to do what you propose be done here.

caw

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