Home hydrogen production

[briandunning]

I was reading an article that described the basic process of electrolysis, with an anode and a cathode in water - hydrogen bubbling off of one, oxygen bubbling off the other (in fact my son has a toy rocket that's hydrogen powered that works this way) - but the article concluded saying that this simple process does not practically scale up to home hydrogen production.

I'm wondering why not. I can easily envision a system with a solar panel and your home water supply, charging a battery to run a compressor, and constantly bubbling off hydrogen. A few valves and sensors and you've got what appears to me to be a complete package. What am I missing? Why wouldn't this work?

 

[CynicalSkeptic]

My (admittedly poor) understanding is that it takes more energy to extract the hydrogen from water then you'd get from recovering it.

 

[briandunning]

That's fine, and it may well be, but it doesn't prevent such a machine from being a source of useful compressed hydrogen. Maybe the complete cycle is less efficient than using the solar electricity directly, but that's not the question. Unfortunately the author of the article did not say why the method does not scale up practically.

 

[JJM]

That's fine, and it may well be, but it doesn't prevent such a machine from being a source of useful compressed hydrogen. Maybe the complete cycle is less efficient than using the solar electricity directly, but that's not the question. Unfortunately the author of the article did not say why the method does not scale up practically.

Certainly, if you store excess solar-derived electricity as hydrogen, it can be beneficial. I don't know how it compares, economically, to battery storage.

Moreover, I don't know how economic solar electricity is overall (it varies enormously- by location). People who go purely solar may lead a more spare lifestyle and/or wait a long time before their savings in electricity match their investment.

I suspect the problem doesn't scale because the demand for electricity, by itself, meets or exceeds the abilty to provide it by solar panels- in most places. Thus, there is little left to store, in any form.

 

[fuelair]

I was reading an article that described the basic process of electrolysis, with an anode and a cathode in water - hydrogen bubbling off of one, oxygen bubbling off the other (in fact my son has a toy rocket that's hydrogen powered that works this way) - but the article concluded saying that this simple process does not practically scale up to home hydrogen production.

I'm wondering why not. I can easily envision a system with a solar panel and your home water supply, charging a battery to run a compressor, and constantly bubbling off hydrogen. A few valves and sensors and you've got what appears to me to be a complete package. What am I missing? Why wouldn't this work?

A) waste B)cost per unit C)cost to get it stored and keep it stored D)Danger!!

 

[parrotslave]

I saw a prototype on This Old House where they used solar cells to produce hydrogen from water. The hydrogen powered a fuel cell at night and when the solar cells weren't enough to meet the energy demands in the home. They said they were about 20 years away from bringing it to market.

Also, on a news report where a guy was doing something similar on his own, his backyard looked like a chemical plant because of all the tanks he needed to store the hydrogen.

 

[Slimething]

Beyond the thermodynamics, I wouldn't visit anyone who kept copious amounts of hydrogen around. I just don't need that much excitement in my life.

 

[Puppycow]

That's fine, and it may well be, but it doesn't prevent such a machine from being a source of useful compressed hydrogen. Maybe the complete cycle is less efficient than using the solar electricity directly, but that's not the question. Unfortunately the author of the article did not say why the method does not scale up practically.

I think it may be "possible" but not "practical."

What sort of equipment would you need to compress the hydrogen? If you kept large amounts of it in balloons, that would be dangerous, I imagine, and also not particularly practical.

Like fuelair said, basically.

 

[Capsid]

I asked this question before in this thread. It doesn't appear to be straightforward.

 

[Cuddles]

I'm wondering why not. I can easily envision a system with a solar panel and your home water supply, charging a battery to run a compressor, and constantly bubbling off hydrogen. A few valves and sensors and you've got what appears to me to be a complete package. What am I missing? Why wouldn't this work?

It would. It's not quite that simple, but it is much easier than many people seem to think. The great thing about fuel cells is that they work just as well in both directions. When there is too much electricity you produce hydrogen, when there is not enough you send it the other way and get electricity.

The only problems at the moment are cost, since all this technology is still very much in the development stage, and risk, since hydrogen is just a little explosive. Unfortunately, the biggest factor is likely to be risk. The cost will come down as the technology matures and demand increases. However, there is something about having every home with it's own tanks of self-igniting explosive that just seems unlikely to happen. It seems quite likely that this sort of thing could happen on an industrial scale, but I can't see it happening in people's homes.

 

[cloudshipsrule]

A few valves and sensors and you've got what appears to me to be a complete package.

You've got what actually appears to be a home-made bomb! As other's have addressed, one of the biggest deterrents is the inherent danger of large amounts of hydrogen, which in and of itself isn't all that dangerous. It's when it's mixed properly with oxygen it becomes a possible problem. Sticking a fork in an electrical outlet can be dangerous. Multiply that danger by some variable larger than one and you have hydrogen. Imagining a bunch of homes around the neighborhood with hydrogen tanks in their garages scares the hell out of me.

P.S.

I work with the stuff pretty much daily, but we have strict procedures to adhere to which the average home-brewed hydrogen farmer would either throw away once they put their 'kit' together, or simply loose in the garage with that damn lawn mower manual. "Where did I put that garage door opener manual again??"

 

[Orangutan]

I used electrolysis to crack (is that the right term?) some water this weekend to demonstrate how oxygen and hydrogen can be made from water. I used two 6volt lantern batteries and it took about 1/2 an hour to fill a film can. It took about 1/10 of a second to make it go pop with a flame.

 

[MortFurd]

I used electrolysis to crack (is that the right term?) some water this weekend to demonstrate how oxygen and hydrogen can be made from water. I used two 6volt lantern batteries and it took about 1/2 an hour to fill a film can. It took about 1/10 of a second to make it go pop with a flame.

How long it takes to generate a particular volume of hydrogen depends on the current flow. Current flow depends on voltage, the resistance of the water, and the surface area of the electrodes.

High voltage is not really where you want to go. Solar cells have a relatively low output voltage, so you'd either have to use them in series or use electronics to step up the voltage. Both methods cause losses - I'm not sure which would be worse.

You can lower the resistance of water by adding minerals or salts to it, but then you end up with the mineral fouling your electrodes. If you use a salt (like common table salt), you end up with the components of the salt fouling things up. NaCl (table salt) gets you sodium on your electrodes and chlorine in your gas. Nasty.

Easiest by far to have a larger surface area on your electrodes. A sheet of copper fanfolded so that it fits under your gas collector will have a far larger surface area than a simple rod that fits under you collector.

 

[Madalch]

If you use a salt (like common table salt), you end up with the components of the salt fouling things up. NaCl (table salt) gets you sodium on your electrodes and chlorine in your gas. Nasty.

Uh, you're not going to get sodium plating out from an aqueous solution. Not unless you're using a mercury electrode and some crazy current density.

The chlorine will be a problem, though, although it's sufficiently soluble that you simply won't get any gas given off.

Sodium sulphate, or sulphuric acid, will be a much better electrolyte.

A sheet of copper fanfolded so that it fits under your gas collector will have a far larger surface area than a simple rod that fits under you collector.

Don't use copper for your anode (the electrode where you expect oxygen to be given off). Copper is more easily oxidized than water, so the electrode will simply dissolve without giving you any oxygen. Once you've got copper ions in solution, they'll migrate over to the cathode, where they'll plate out as copper, thus lowering the amount of hydrogen produced. A graphite rod will work fine as an anode (assuming you can't afford platinum or gold).

 

[Orangutan]

I used magnesium sulphate as It's easy to get hold of. (Its Epsom Salts!).

Also I used the graphite from a carpenters pencil as its nice and flat and thick, As I wanted it fully submerged I wrapped the copper coils where I connected the graphite in electrical tape so only the graphite stuck out.



Edit:
Getting the graphite from the pencil without breaking it is the hardest part. careful if you use a box cutter to whittle it out!

 

[Madalch]

I used magnesium sulphate as It's easy to get hold of. (Its Epsom Salts!).

That works, too. Adding a small amount of battery acid will make sure that you don't get any magnesium plating out, regardless of what voltage you use.

Getting the graphite from the pencil without breaking it is the hardest part. careful if you use a box cutter to whittle it out!

Even if you just get most of the wood off with the knife, you can get the rest off by holding the graphite in a candle flame for a short period of time. I found my electrodes broke less often when I did that.

 

[Ranb]

I do not think hydrogen in a tank all by itself is much more dangerous than other gases. When was the last time you heard of oxy-acetylene welding units blowing up?

I was reading in the book Skunk Works about Ben Rich's attempts to build a hydrogen fueling and handling station for a hydrogen powered jet. He also had the same concerns that are voiced here. He found that rupturing and igniting a pressurized hydrogen tank did not result in much of an explosion, he had to have a mix of oxygen and hydrogen to make it really nasty.

Diverting surplus solar electricity sounds like a good way to store hydrogen and oxygen in separate tanks. The US Navy makes oxygen (using DC power from the reactor plant) for their subs this way; they let the hydrogen vent overboard.

Ranb

 

[fsol]

I do not think hydrogen in a tank all by itself is much more dangerous than other gases. When was the last time you heard of oxy-acetylene welding units blowing up?

I was reading in the book Skunk Works about Ben Rich's attempts to build a hydrogen fueling and handling station for a hydrogen powered jet. He also had the same concerns that are voiced here. He found that rupturing and igniting a pressurized hydrogen tank did not result in much of an explosion, he had to have a mix of oxygen and hydrogen to make it really nasty.

Diverting surplus solar electricity sounds like a good way to store hydrogen and oxygen in separate tanks. The US Navy makes oxygen (using DC power from the reactor plant) for their subs this way; they let the hydrogen vent overboard.

Ranb

People are quite happy to drive around in petrol powered cars, fill them up themselves and even keep them indoors. I wouldn't say hydrogen is any more dangerous than that. It may involve a different set of precautions, but my experience of working with hydrogen didn't exactly make me fear for my safety.

I have a gas cooker and central heating, I'm not particualy concerned about them springing a leak and going boom either.

 

[cloudshipsrule]

I do not think hydrogen in a tank all by itself is much more dangerous than other gases.

When it's in the tank all by itself it's fine! It's when a hose, connection or valve leaks in the system leaks and the H mixes with the O that it becomes a problem. Explosive gas meters could help a little.

 

[cloudshipsrule]

I wouldn't say hydrogen is any more dangerous than that.

You guys are underestimating the potential dangers of hydrogen. Hydrogen is the most explosive gas used in industry today. It's definitly not a gas that just any ole' civilian should have unchecked access to. Without proper precautions, working with hydrogen can be extremely dangerous. The general public is simply not trained to work with such gases.