6 ms·

It’s not really that advantageous for energy storage. The round trip energy efficiency is less than 50% so half of any stored energy is wasted.

ncmncm 5y ago
Perhaps surprisingly, the round-trip efficiency of an energy storage medium becomes relatively unimportant when the top-line cost of production gets low enough. Other costs come to dominate. The odds-on favorite for utility-scale battery storage is iron-air batteries. Nobody even mentions the round-trip efficiency of those, so it must be pretty awful. But they are darned cheap. We can expect solar, in particular, to be routinely massively over-provisioned, so that much of the time most of the output would otherwise be wasted if not used opportunistically to charge batteries or hydrolyze water to synthesize H2 or NH3.
- Hypx_ 5y ago
  Iron-air batteries are literally just fuel cells that involve iron instead of hydrogen. THe odds on favorite is hydrogen fuel cells and it probably can’t be anything else (short of some kind of nuclear solution).
  - ncmncm 5y ago
    You keep saying so, but what I am seeing is serious plans for iron, and synthesizing NH3 as portable fuel, but very little activity on H2. Is there actually any current work on industrial-scale H2 synthesis for storage, as opposed to for use in e.g. steel production or fuel?
    - throwaway894345 5y ago
      I Googled around for this some time ago and found quite a few grid-storage projects in the US and Europe (both public and private), but I don’t have links handy at the moment. They all seem to be pretty early-days IIRC. But yes, mostly you have to sift through a lot of results related to transportation fuel cells.
    - Hypx_ 5y ago
      It should be noted that using hydrogen for steel or fuel production lead almost directly leads to some kind of hydrogen storage. If you can make that much hydrogen, it just becomes a natural step to use it as a energy storage system. Also, the scale of hydrogen storage facilities far exceeds anything else ever proposed: https://www.pv-magazine-australia.com/2021/10/23/weekend-read-australias-massive-hydrogen-storage-potential/ https://www.pv-magazine-australia.com/2021/10/23/weekend-rea... It's clear that obsessing over the last step is unnecessary. As soon as you have the hydrogen available, there will be many obvious solutions available.
      - ncmncm 5y ago
        I don't doubt that, once hydrogen becomes heavily used as a fuel--exclusively for aviation, I expect--it will then also become useful, secondarily, as a storage medium for utility power. But the first condition is barely even in planning stages, if there. By the time hydrogen as bulk fuel does happen, other storage for utility power will be very mature, and hydrogen will need really compelling advantages to be able to compete in places where it is not already being stored as aviation fuel. The cited article points out that utility-grade storage in salt caverns is still a wholly hypothetical possibility, and speculates on problems that might yet render it impractical.
        Hypx_ 5y ago
        It's advantage is that fact that it stores multiple orders of magnitude more energy than anything else, at a cost level that is orders of magnitude cheaper too. It's a matter of when, not if, hydrogen becomes the primary energy storage mechanism. Storing hydrogen underground has existed for decades. It's already been accepted by people in the industry that this is a solved problem.
        ncmncm 5y ago
        Yet, the article you cited yourself says the opposite: that it needs study to determine its practicality. I don't doubt that whatever problems turn up will be solved, in time. Underground storage of liquified hydrogen, rather than gas under high pressure, seems like a great idea, since earth is such a good insulator, but they don't seem to be talking much about LH2. The methods used to oxidize H2 seem to produce a great amount of waste heat. If you have uses for the heat, that may be not so bad. But producing power from stored H2 at GW rates would produce more heat than is easily used on the same schedule as the power is demanded. The heat could also be banked underground, maybe, but there remains the problem of delivering it where it is actually needed.
tonyedgecombe 5y ago
If that energy would otherwise be wasted (because of an excess of supply in the market) then perhaps the efficiency doesn't matter so much.
- Leynos 5y ago
  It always struck me that 50% efficiency is better than 0%.

ncmncm 5y ago

Perhaps surprisingly, the round-trip efficiency of an energy storage medium becomes relatively unimportant when the top-line cost of production gets low enough. Other costs come to dominate. The odds-on favorite for utility-scale battery storage is iron-air batteries. Nobody even mentions the round-trip efficiency of those, so it must be pretty awful. But they are darned cheap. We can expect solar, in particular, to be routinely massively over-provisioned, so that much of the time most of the output would otherwise be wasted if not used opportunistically to charge batteries or hydrolyze water to synthesize H2 or NH3.

Hypx_ 5y ago
Iron-air batteries are literally just fuel cells that involve iron instead of hydrogen. THe odds on favorite is hydrogen fuel cells and it probably can’t be anything else (short of some kind of nuclear solution).
- ncmncm 5y ago
  You keep saying so, but what I am seeing is serious plans for iron, and synthesizing NH3 as portable fuel, but very little activity on H2. Is there actually any current work on industrial-scale H2 synthesis for storage, as opposed to for use in e.g. steel production or fuel?
  - throwaway894345 5y ago
    I Googled around for this some time ago and found quite a few grid-storage projects in the US and Europe (both public and private), but I don’t have links handy at the moment. They all seem to be pretty early-days IIRC. But yes, mostly you have to sift through a lot of results related to transportation fuel cells.
  - Hypx_ 5y ago
    It should be noted that using hydrogen for steel or fuel production lead almost directly leads to some kind of hydrogen storage. If you can make that much hydrogen, it just becomes a natural step to use it as a energy storage system. Also, the scale of hydrogen storage facilities far exceeds anything else ever proposed: https://www.pv-magazine-australia.com/2021/10/23/weekend-read-australias-massive-hydrogen-storage-potential/ https://www.pv-magazine-australia.com/2021/10/23/weekend-rea... It's clear that obsessing over the last step is unnecessary. As soon as you have the hydrogen available, there will be many obvious solutions available.
    - ncmncm 5y ago
      I don't doubt that, once hydrogen becomes heavily used as a fuel--exclusively for aviation, I expect--it will then also become useful, secondarily, as a storage medium for utility power. But the first condition is barely even in planning stages, if there. By the time hydrogen as bulk fuel does happen, other storage for utility power will be very mature, and hydrogen will need really compelling advantages to be able to compete in places where it is not already being stored as aviation fuel. The cited article points out that utility-grade storage in salt caverns is still a wholly hypothetical possibility, and speculates on problems that might yet render it impractical.
      - Hypx_ 5y ago
        It's advantage is that fact that it stores multiple orders of magnitude more energy than anything else, at a cost level that is orders of magnitude cheaper too. It's a matter of when, not if, hydrogen becomes the primary energy storage mechanism. Storing hydrogen underground has existed for decades. It's already been accepted by people in the industry that this is a solved problem.
        ncmncm 5y ago
        Yet, the article you cited yourself says the opposite: that it needs study to determine its practicality. I don't doubt that whatever problems turn up will be solved, in time. Underground storage of liquified hydrogen, rather than gas under high pressure, seems like a great idea, since earth is such a good insulator, but they don't seem to be talking much about LH2. The methods used to oxidize H2 seem to produce a great amount of waste heat. If you have uses for the heat, that may be not so bad. But producing power from stored H2 at GW rates would produce more heat than is easily used on the same schedule as the power is demanded. The heat could also be banked underground, maybe, but there remains the problem of delivering it where it is actually needed.

tonyedgecombe 5y ago

If that energy would otherwise be wasted (because of an excess of supply in the market) then perhaps the efficiency doesn't matter so much.

Leynos 5y ago
It always struck me that 50% efficiency is better than 0%.