4 ms·

Paywall free link: https://web.archive.org/web/20210708014033/https://www.chemistryworld.com/news/sub-zero-water-splitting-marks-a-new-dawn-for-solar-hydrogen-p

by tacLog 5y ago

Paywall free link: https://web.archive.org/web/20210708014033/https://www.chemistryworld.com/news/sub-zero-water-splitting-marks-a-new-dawn-for-solar-hydrogen-production/4013887.article https://web.archive.org/web/20210708014033/https://www.chemi... First off this seems like a really important addition to solar in general. My impression is that hydrogen is easy to make, can be a closed water cycle (uses the same water it generates to when release the energy), and the only downside is the inefficacies of compressing it to store it among the other steps. Does anyone know if this would be a practical source of heat say at night, considering what I understood to be Hydrogens lower energy density? For example, I was wondering roughly how big of a tank of (I am assuming) liquid hydrogen would be required to match say 50 a gallon tank of diesel. Or am I missing something here?

vimacs2 5y ago
There isn't a paywall I can spot in the original link - perhaps it's a regional thing? What you might be missing here is that the "only downside" should be emphasized far more. Hydrogen is a bloody nightmare to store long term. It's boiling point makes the -20 C involved with this technology look like an oven and you really do want to ideally store it as a liquid since the exceptionally low molecular weight means leakage is a constant problem save for some very advanced (and expensive at scale) carbon composites. Graphene seems to be a potentially excellent storage medium but we are still a while off from being able to manufacture that at the amount that would make it economically usable for hydrogen storage at scale.
- nine_k 5y ago
  One way to store hydrogen safely long term is metal hydrides. Hydrogen readily infuses certain metals, like lithium, like water infuses a sponge. The problem is that the density us rather low. Enough to store tritium in a nuclear warhead, but possibly a bit bulky for home use. (Also, the hydride remains flammable.)
  - wrycoder 5y ago
    Titanium hydride storage has been tested for automotive use. They shot hydride tanks with a rifle, and the result was less impressive than shooting a gasoline tank. Also, hydrogen rises quickly as it burns, instead of spreading out on the ground.
- jessaustin 5y ago
  Hydrogen is readily stored as liquid anhydrous ammonia.
  - rbanffy 5y ago
    I’d rather cleanup a diesel spill than an ammonia one.
  - tacLog 5y ago
    Do you have more details on this somewhere? Maybe a nice semi-technical writeup?
    - jessaustin 5y ago
      With a bit of DDGing I found something [0] from March by the chemical society. With respect to storage density, NH3 is better: Ammonia has a higher energy density, at 12.7 MJ/L, than even liquid hydrogen, at 8.5 MJ/L. Liquid hydrogen has to be stored at cryogenic conditions of –253 °C, whereas ammonia can be stored at a much less energy-intensive –33 °C. And ammonia, though hazardous to handle, is much less flammable than hydrogen. This doesn't even mention how elemental hydrogen weakens metals over time ("embrittlement"), which makes storage even more challenging. There are lots of other issues discussed at that link, and it's clear that NH3 will be more expensive than e.g. gasoline, at least until there is better solar power. Still, if hydrogen makes sense, ammonia makes sense. [0] https://cen.acs.org/business/petrochemicals/ammonia-fuel-future/99/i8 https://cen.acs.org/business/petrochemicals/ammonia-fuel-fut...

by tacLog 5y ago

vimacs2 5y ago

There isn't a paywall I can spot in the original link - perhaps it's a regional thing? What you might be missing here is that the "only downside" should be emphasized far more. Hydrogen is a bloody nightmare to store long term. It's boiling point makes the -20 C involved with this technology look like an oven and you really do want to ideally store it as a liquid since the exceptionally low molecular weight means leakage is a constant problem save for some very advanced (and expensive at scale) carbon composites. Graphene seems to be a potentially excellent storage medium but we are still a while off from being able to manufacture that at the amount that would make it economically usable for hydrogen storage at scale.

nine_k 5y ago
One way to store hydrogen safely long term is metal hydrides. Hydrogen readily infuses certain metals, like lithium, like water infuses a sponge. The problem is that the density us rather low. Enough to store tritium in a nuclear warhead, but possibly a bit bulky for home use. (Also, the hydride remains flammable.)
- wrycoder 5y ago
  Titanium hydride storage has been tested for automotive use. They shot hydride tanks with a rifle, and the result was less impressive than shooting a gasoline tank. Also, hydrogen rises quickly as it burns, instead of spreading out on the ground.
jessaustin 5y ago
Hydrogen is readily stored as liquid anhydrous ammonia.
- rbanffy 5y ago
  I’d rather cleanup a diesel spill than an ammonia one.
- tacLog 5y ago
  Do you have more details on this somewhere? Maybe a nice semi-technical writeup?
  - jessaustin 5y ago
    With a bit of DDGing I found something [0] from March by the chemical society. With respect to storage density, NH3 is better: Ammonia has a higher energy density, at 12.7 MJ/L, than even liquid hydrogen, at 8.5 MJ/L. Liquid hydrogen has to be stored at cryogenic conditions of –253 °C, whereas ammonia can be stored at a much less energy-intensive –33 °C. And ammonia, though hazardous to handle, is much less flammable than hydrogen. This doesn't even mention how elemental hydrogen weakens metals over time ("embrittlement"), which makes storage even more challenging. There are lots of other issues discussed at that link, and it's clear that NH3 will be more expensive than e.g. gasoline, at least until there is better solar power. Still, if hydrogen makes sense, ammonia makes sense. [0] https://cen.acs.org/business/petrochemicals/ammonia-fuel-future/99/i8 https://cen.acs.org/business/petrochemicals/ammonia-fuel-fut...