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Can you just store the hydrogen? Or is it just so inefficient as to be useless? Seems like batteries to cover 95%+ of your use case then having hydrogen backup

by nimos 9y ago

Can you just store the hydrogen? Or is it just so inefficient as to be useless? Seems like batteries to cover 95%+ of your use case then having hydrogen backup for for covering rare weather conditions might work well for off grid setups.

philipkglass 9y ago
That's the "battolyser" concept -- store and use the hydrogen from nickel-iron unit charging instead of wasting it. But round-trip storage efficiency is lower via hydrogen (if you want electricity as the end form of energy) and it increases complexity/cost to add systems for hydrogen. So the economics may not be improved even though the energetic efficiency would be.
leggomylibro 9y ago
I think the main issue with hydrogen is just that it's crazy dangerous and sort of hard to work with safely. It's highly flammable, and becomes violently explosive when mixed with oxygen. It's easy to make - just pass current through water - but while all batteries are basically bombs, a key factor in their design is that they should go off very slowly.
- rzzzt 9y ago
  How about burning it as it is produced?
  - leggomylibro 9y ago
    Okay, but now you just have some steam and heat floating around. It's gonna dissipate pretty quickly, not a great way to store power for the medium-long term. Hydrogen separated from Oxygen is where the useful potential energy difference is. The idea behind hydrogen fuel cell batteries is that you spend your cheap clean renewable energy to split H2O slowly when energy is available, and burn the hydrogen when you need bursts of power. If you burn the hydrogen right away, you're just un-doing the water-splitting reaction and you won't have anything to use for power when the cheap clean renewable energy is not available, like during the night for solar power. I think that the usual way to get energy back out of the hydrogen is just to burn it and let the hot pressurized gas power a steam turbine, but don't quote me on that. Or try it at home; scalding and flash burns are good things to avoid.
    - Doxin 9y ago
      Could you use the steam to drive a turbine to recharge the batteries? You'd not recover nearly everything clearly but I'd imagine it's more than nothing.
crankylinuxuser 9y ago
You reallllly don't want to store H2 gas. On second thought, you realllllllllllly dont want to store H2 gas. Having worked some in welding (I considered doing it instead of programming for a while), the problems with H2 are numerous. Firstly, it seeps out of any container you put it in. And I do mean any. Hell, even glass ampules in the chemistry have a hard time sealing H2. Another major issue, is that H2 does "fucky" things with metal. Ever heard of hydrogen embrittlement? (1) You have cracks in your metal. Well, hydrogen, being as tiny as it is, also can bond with the metal. Gets in there, makes cracks bigger. Creates weird metal acids (H2FeCO4) and they attack more metal. And if you're storing H2 gas in a regular container, you just made a time detonating fuse, and.... you don't know the time. But yeah, H2 gas creation may be easy, but storage is super hard and really dangerous. And unless you can get H2 in liquid form, it's pretty low power density compared to things like octane. (1) https://en.wikipedia.org/wiki/Hydrogen_embrittlement https://en.wikipedia.org/wiki/Hydrogen_embrittlement

by nimos 9y ago

philipkglass 9y ago

That's the "battolyser" concept -- store and use the hydrogen from nickel-iron unit charging instead of wasting it. But round-trip storage efficiency is lower via hydrogen (if you want electricity as the end form of energy) and it increases complexity/cost to add systems for hydrogen. So the economics may not be improved even though the energetic efficiency would be.

leggomylibro 9y ago

I think the main issue with hydrogen is just that it's crazy dangerous and sort of hard to work with safely. It's highly flammable, and becomes violently explosive when mixed with oxygen. It's easy to make - just pass current through water - but while all batteries are basically bombs, a key factor in their design is that they should go off very slowly.

rzzzt 9y ago
How about burning it as it is produced?
- leggomylibro 9y ago
  Okay, but now you just have some steam and heat floating around. It's gonna dissipate pretty quickly, not a great way to store power for the medium-long term. Hydrogen separated from Oxygen is where the useful potential energy difference is. The idea behind hydrogen fuel cell batteries is that you spend your cheap clean renewable energy to split H2O slowly when energy is available, and burn the hydrogen when you need bursts of power. If you burn the hydrogen right away, you're just un-doing the water-splitting reaction and you won't have anything to use for power when the cheap clean renewable energy is not available, like during the night for solar power. I think that the usual way to get energy back out of the hydrogen is just to burn it and let the hot pressurized gas power a steam turbine, but don't quote me on that. Or try it at home; scalding and flash burns are good things to avoid.
  - Doxin 9y ago
    Could you use the steam to drive a turbine to recharge the batteries? You'd not recover nearly everything clearly but I'd imagine it's more than nothing.

crankylinuxuser 9y ago

You reallllly don't want to store H2 gas. On second thought, you realllllllllllly dont want to store H2 gas. Having worked some in welding (I considered doing it instead of programming for a while), the problems with H2 are numerous. Firstly, it seeps out of any container you put it in. And I do mean any. Hell, even glass ampules in the chemistry have a hard time sealing H2. Another major issue, is that H2 does "fucky" things with metal. Ever heard of hydrogen embrittlement? (1) You have cracks in your metal. Well, hydrogen, being as tiny as it is, also can bond with the metal. Gets in there, makes cracks bigger. Creates weird metal acids (H2FeCO4) and they attack more metal. And if you're storing H2 gas in a regular container, you just made a time detonating fuse, and.... you don't know the time. But yeah, H2 gas creation may be easy, but storage is super hard and really dangerous. And unless you can get H2 in liquid form, it's pretty low power density compared to things like octane. (1) https://en.wikipedia.org/wiki/Hydrogen_embrittlement https://en.wikipedia.org/wiki/Hydrogen_embrittlement