Sources of hydrogen and oxygen for a fuel cell.

[Degenerate]

Some "friendly ways" i have hear/read/thought about:
I believe oxygen is readily obtained from air, so the main quest is a good source of hydrogen. (correct me)

1) dissasociattion of water using renewable energy (solar, wind...)
2) Methane

I understand that storing the gas is a prime consideration since it takes energy to keep it pressurized. Also, for the reation to occure, there has to be some sort of membrane to seperate molecules from each other.

Are there any other sources of O2 and H2?
Is Ammonia a good souce? since it is easily liquidfied and containes 3H/N ratio - reasonable compared to methane 4/1 especially when it takes more energy to store methane.

 

[PowerEngineer]

The real issue as far as I'm concerned about the use of hydrogen is not the source of the hydrogen itself, but the source of the energy needed to disassociate it from whatever lower energy form it's found in.

One novel approach I recently heard suggested is that we use genertic engineering to create bacteria that will produce hydrogen gas as a byproduct of their digestive processes. Maybe someday we will be able to reroute our garbage disposals to a vat full of this bacteria so that the little beasties can convert last night's dinner scrapings into hydrogen fuel for the next morning's commute!

 

[KenGr]

Ammonia would be good except it is not a readily available compound. It must be manufactured which takes a considerable energy input. Also, it is quite hazardous to humans - much more so than propane, methane, etc. - when released accidently. Methane occurs naturally and also as the byproduct of fairly simple reactions.

 

[Howard]

Storing and transporting methane is quite difficult. Why not propane?

 

[charrison]

Gas from refined oil is quite hydrogen rich.

 

[rgwalt]

Well, it all depends on how you want to transport your hyrdogen. You can carry a tank of hyrdogen gas with you, or carry a compound that yields hydrogen when burned. Carrying pressurized H2 is difficult, costly, and dangerous, though a lot of research is going into novel storage devices that use new compounds such as carbon nanotubes. In general, we don't want to carry gasses with us to power our vehicles. We would much rather carry liquids. Thus methane, propane, etc are out. In fact, the source of H2 that is easiest to deal with currently is gasoline. As consumers, we already know how to operate a gas pump. As a nation, the infrastructure and distribution system for gasoline already exists. So, it is the least costly and least prohibitive source of hydrogen at the moment. Hydrogen can be generated on board the vehicle using a series of reactions in various catalytic reactors that consist of an auto reformer and a "water-gas shift" reactor. The result is that these reactions take a mixture of air and gasoline and turn it into H2, CO2, and CO. N2 is present as it goes along for the ride. The CO is scrubbed out thoroughly in a CO scrubber in order to avoid contamination of the electrodes. The gas mixture is the introduced into the fuel cell where the H2 loses two electrons to the anode. 2 H+ ions pass through what is known as the proton exchange membrane (aka PEM), and react with 1/2O2 and the two electrons at the cathode. The potential difference between the anode and the cathode is then used to charge batteries or drive a car.

Ammonia would make a poor choice as a hydrogen source as ammonia product requires H2, which is often generated using an auto-reformer and a water-gas shift reaction.

Ryan

 

[Degenerate]

Thanks for the input guys

 

[silverpig]

Originally posted by: rgwalt
Well, it all depends on how you want to transport your hyrdogen. You can carry a tank of hyrdogen gas with you, or carry a compound that yields hydrogen when burned. Carrying pressurized H2 is difficult, costly, and dangerous, though a lot of research is going into novel storage devices that use new compounds such as carbon nanotubes. In general, we don't want to carry gasses with us to power our vehicles. We would much rather carry liquids. Thus methane, propane, etc are out. In fact, the source of H2 that is easiest to deal with currently is gasoline. As consumers, we already know how to operate a gas pump. As a nation, the infrastructure and distribution system for gasoline already exists. So, it is the least costly and least prohibitive source of hydrogen at the moment. Hydrogen can be generated on board the vehicle using a series of reactions in various catalytic reactors that consist of an auto reformer and a "water-gas shift" reactor. The result is that these reactions take a mixture of air and gasoline and turn it into H2, CO2, and CO. N2 is present as it goes along for the ride. The CO is scrubbed out thoroughly in a CO scrubber in order to avoid contamination of the electrodes. The gas mixture is the introduced into the fuel cell where the H2 loses two electrons to the anode. 2 H+ ions pass through what is known as the proton exchange membrane (aka PEM), and react with 1/2O2 and the two electrons at the cathode. The potential difference between the anode and the cathode is then used to charge batteries or drive a car.

Ammonia would make a poor choice as a hydrogen source as ammonia product requires H2, which is often generated using an auto-reformer and a water-gas shift reaction.

Ryan

I saw a recent article on fuel cell cars. They have made tanks that can be pressurized up to 10000 psi and can withstand a drop from 4 storeys onto a concrete slab. They still don't give great range though, but it's definitely progress. That carbon nanotube idea was mentioned, and it seems to be they way things are headed.

 

[Shalmanese]

Originally posted by: silverpig

Originally posted by: rgwalt


I saw a recent article on fuel cell cars. They have made tanks that can be pressurized up to 10000 psi and can withstand a drop from 4 storeys onto a concrete slab. They still don't give great range though, but it's definitely progress. That carbon nanotube idea was mentioned, and it seems to be they way things are headed.

4 stories is maybe 20m which means its only going at 20m/s of ~70km/s when it hit the ground. Just slightly above city driving speed for a stationary collision and barely more than a crawl for a head on collision with another car. I would expect at least a 3 - 400km/hr collsion to simulate worst case scenario.