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> Ammonia is a great not-on-demand consumer of electricty. This does not follow. The cost efficiency of ammonia production is highly dependent on the process b

> Ammonia is a great not-on-demand consumer of electricty. This does not follow. The cost efficiency of ammonia production is highly dependent on the process being continuous and steady state. Every analysis that says ammonia is cost effective as a fuel is based on an efficient continuous process as a cost assumption. If you are constantly starting and stopping based on electricity availability then your ammonia just became much more expensive. In which case, it is probably no longer cost effective as a fuel. Mixing "best possible price" and "worst possible process" and pretending these represent the same instance of reality is misleading to say the least.

pfdietz 2y ago
> The cost efficiency of ammonia production is highly dependent on the process being continuous and steady state. Hydrogen is the overwhelming energy input to ammonia production. Hydrogen is readily storable -- this is done even today, when the hydrogen comes from natural gas, to smooth things out to keep the ammonia plant running -- so intermittency of renewables will be almost entirely countered by doing the same thing and storing the green hydrogen. What matters is cost of electrolysers, but they have been getting very cheap in China.
- jandrewrogers 2y ago
  It is not just the cost of inputs. Ammonia synthesis is a high-pressure high-temperature process. One of the reasons to use a continuous steady-state process is that cycling it up and down causes thermal and pressure fatigue in the reactor. The safe operating life of a reactor can be surprisingly short if it is not operated at a steady state. If you want this to scale, it needs to be low maintenance and have a long operating life. You could in principle centralize ammonia production with sufficient reactant reserves to ensure continuous production from variable low-density energy sources like solar or wind. However, this would require hydrogen pipelines that largely don't exist and would take a long time to build. We can't repurpose existing natural gas infrastructure and similar because they weren't built with alloys resistant to hydrogen embrittlement. One of the big economic advantages of using methane for ammonia is that it takes advantage of the millions of kilometers of natural gas distribution pipeline that already exists. I'm not averse to the idea but the enthusiastic proponents are pretending like the practical realities of industrial chemistry don't apply to them. We aren't going to get to a green future with rainbows and unicorns, we need to brutally realistic about the true requirements.
  - pfdietz 2y ago
    I wasn't talking about the cost of inputs, I was talking about their putative intermittency. The argument that was being made seemed to be "renewables are intermittent, therefore ammonia synthesis based on renewable energy must be intermittent, or else use expensive storage". The counterargument is that hydrogen is the overwhelmingly most important input, and it is highly storable, so the intermittency of the inputs can be largely avoided at modest cost, allowing the ammonia plant to run 24/7. You may not be aware, but we already have hydrogen pipelines coupled to ammonia plants. The US has ~1000 miles of hydrogen pipelines for this purpose. It's also not obvious to me why pipelines would necessarily be needed. After all, the ammonia plant could be built where the hydrogen is stored.
  - deleted 2y ago
    [deleted]
  - 0cf8612b2e1e 2y ago
    Can factories install local battery banks to cover a day’s utilization? Charge up the batteries on the cheap electricity during noon and run the plant off of those reserves. I assume other industries are already running these cost optimization analyses as the renewable electricity market continues to develop. There is a balancing point between the capex and opex, but unless it is insanely energy hungry (like aluminum), that seems possible.
    - jandrewrogers 2y ago
      > but unless it is insanely energy hungry (like aluminum) Producing a ton of hydrogen by electrolysis requires ~3x the energy to produce a ton of aluminum. It is, in fact, "insanely energy hungry". This isn't necessarily a problem but it does create logistical challenges.
      - marcosdumay 2y ago
        What comes back to the fact that you only need batteries for the ammonia production. Hydrogen production is a low-pressure process, and optionally even low-temperature.
- joshuanapoli 2y ago
  Liquid ammonia takes less energy and volume than liquifying hydrogen.
  - pfdietz 2y ago
    This has nothing to do with hydrogen as an input to the ammonia production process. This hydrogen is not liquefied, even if it is temporarily stored (as a compressed gas, for example underground in solution mined salt caverns.)

pfdietz 2y ago

> The cost efficiency of ammonia production is highly dependent on the process being continuous and steady state. Hydrogen is the overwhelming energy input to ammonia production. Hydrogen is readily storable -- this is done even today, when the hydrogen comes from natural gas, to smooth things out to keep the ammonia plant running -- so intermittency of renewables will be almost entirely countered by doing the same thing and storing the green hydrogen. What matters is cost of electrolysers, but they have been getting very cheap in China.

jandrewrogers 2y ago
It is not just the cost of inputs. Ammonia synthesis is a high-pressure high-temperature process. One of the reasons to use a continuous steady-state process is that cycling it up and down causes thermal and pressure fatigue in the reactor. The safe operating life of a reactor can be surprisingly short if it is not operated at a steady state. If you want this to scale, it needs to be low maintenance and have a long operating life. You could in principle centralize ammonia production with sufficient reactant reserves to ensure continuous production from variable low-density energy sources like solar or wind. However, this would require hydrogen pipelines that largely don't exist and would take a long time to build. We can't repurpose existing natural gas infrastructure and similar because they weren't built with alloys resistant to hydrogen embrittlement. One of the big economic advantages of using methane for ammonia is that it takes advantage of the millions of kilometers of natural gas distribution pipeline that already exists. I'm not averse to the idea but the enthusiastic proponents are pretending like the practical realities of industrial chemistry don't apply to them. We aren't going to get to a green future with rainbows and unicorns, we need to brutally realistic about the true requirements.
- pfdietz 2y ago
  I wasn't talking about the cost of inputs, I was talking about their putative intermittency. The argument that was being made seemed to be "renewables are intermittent, therefore ammonia synthesis based on renewable energy must be intermittent, or else use expensive storage". The counterargument is that hydrogen is the overwhelmingly most important input, and it is highly storable, so the intermittency of the inputs can be largely avoided at modest cost, allowing the ammonia plant to run 24/7. You may not be aware, but we already have hydrogen pipelines coupled to ammonia plants. The US has ~1000 miles of hydrogen pipelines for this purpose. It's also not obvious to me why pipelines would necessarily be needed. After all, the ammonia plant could be built where the hydrogen is stored.
- deleted 2y ago
  [deleted]
- 0cf8612b2e1e 2y ago
  Can factories install local battery banks to cover a day’s utilization? Charge up the batteries on the cheap electricity during noon and run the plant off of those reserves. I assume other industries are already running these cost optimization analyses as the renewable electricity market continues to develop. There is a balancing point between the capex and opex, but unless it is insanely energy hungry (like aluminum), that seems possible.
  - jandrewrogers 2y ago
    > but unless it is insanely energy hungry (like aluminum) Producing a ton of hydrogen by electrolysis requires ~3x the energy to produce a ton of aluminum. It is, in fact, "insanely energy hungry". This isn't necessarily a problem but it does create logistical challenges.
    - marcosdumay 2y ago
      What comes back to the fact that you only need batteries for the ammonia production. Hydrogen production is a low-pressure process, and optionally even low-temperature.
joshuanapoli 2y ago
Liquid ammonia takes less energy and volume than liquifying hydrogen.
- pfdietz 2y ago
  This has nothing to do with hydrogen as an input to the ammonia production process. This hydrogen is not liquefied, even if it is temporarily stored (as a compressed gas, for example underground in solution mined salt caverns.)