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The problem with any fuel containing H2 in any existing engine is hydrogen embrittlement. Hydrogen is a reactive gas that attacks steel. Ammonia fuel cells hav

by scythe 4y ago

The problem with any fuel containing H2 in any existing engine is hydrogen embrittlement. Hydrogen is a reactive gas that attacks steel. Ammonia fuel cells have a comparable weight proposition to hydrogen at small sizes because the tank is so much lighter. I think that has legs (or wheels?). For stationary storage, the ammonia-CO2 adduct is a solid, which is nice.

ncmncm 4y ago
Hydrogen embrittlement is always hyped to the sky. It is not a serious problem unless you are trying to keep warm, gaseous hydrogen under high pressure. So, don't. Furthermore, aluminum is quite resistant to embrittlement. Of possibly greater moment is that it leaks, and has ~200x GHG over CO2 (including secondary effects). Leaks are not dangerous in the open, or in confined places with positive airflow, but punishment for neglect is visited on all bystanders. LN2 storage is better, where you can afford the insulation and refrigeration.
- katmannthree 4y ago
  > trying to keep warm, gaseous hydrogen under high pressure Which of course nobody would do? Unfortunately, those are the circumstances in which H2 is made from fossil fuels and likewise the circumstances under which it is combusted in turbines. You can't just handwave materials compatibility away.
  - ncmncm 4y ago
    Keyword is "keep". Hydrogen will not be penetrating and weakening turbine blades.
    - katmannthree 4y ago
      The turbine blades are downstream of the combustion chamber so they handle combustion products not hydrogen-rich gas. The turbine combustion chambers, fuel handling system, and high pressure H2 compressors[0] _do_ have to function in a high pressure high temperature H2-rich environment. 0: Take a guess as to what those look like inside.
- shawndrost 4y ago
  I think this is incorrect; I have seen GWP20 numbers like 38, eg here[1], or lower numbers for GWP100. Do you have a citation? [1] https://www.greenbiz.com/article/inside-misconception-hydrogen-significant-warming-risk https://www.greenbiz.com/article/inside-misconception-hydrog...
- tuatoru 4y ago
  > Of possibly greater moment is that it leaks It leaks very readily, it ignites very readily, it burns with a wide range of air:fuel proportions, it burns with a high flame speed, and it burns hot. Hydrogen is ... not a good choice for something to reticulate widely around the world. Edit: That's leaving aside its low energy density. You need three times the volume of hydrogen as natural gas for the same quantity of heat, so existing pipe networks are unlikely to be useful. Global warming potential is off to the side of all this.
  - ncmncm 4y ago
    Yet, millions of tons of hydrogen are today produced, transported and used. There is nothing special about the volumetric energy density of NG. H2 has to move faster, if carried in the same pipe for the same use. Its lower viscosity means it can. Municipal gas networks used to carry "lamp gas", a mix of CO and H2, in cast-iron pipes.

by scythe 4y ago

ncmncm 4y ago

Hydrogen embrittlement is always hyped to the sky. It is not a serious problem unless you are trying to keep warm, gaseous hydrogen under high pressure. So, don't. Furthermore, aluminum is quite resistant to embrittlement. Of possibly greater moment is that it leaks, and has ~200x GHG over CO2 (including secondary effects). Leaks are not dangerous in the open, or in confined places with positive airflow, but punishment for neglect is visited on all bystanders. LN2 storage is better, where you can afford the insulation and refrigeration.

katmannthree 4y ago
> trying to keep warm, gaseous hydrogen under high pressure Which of course nobody would do? Unfortunately, those are the circumstances in which H2 is made from fossil fuels and likewise the circumstances under which it is combusted in turbines. You can't just handwave materials compatibility away.
- ncmncm 4y ago
  Keyword is "keep". Hydrogen will not be penetrating and weakening turbine blades.
  - katmannthree 4y ago
    The turbine blades are downstream of the combustion chamber so they handle combustion products not hydrogen-rich gas. The turbine combustion chambers, fuel handling system, and high pressure H2 compressors[0] _do_ have to function in a high pressure high temperature H2-rich environment. 0: Take a guess as to what those look like inside.
shawndrost 4y ago
I think this is incorrect; I have seen GWP20 numbers like 38, eg here[1], or lower numbers for GWP100. Do you have a citation? [1] https://www.greenbiz.com/article/inside-misconception-hydrogen-significant-warming-risk https://www.greenbiz.com/article/inside-misconception-hydrog...
tuatoru 4y ago
> Of possibly greater moment is that it leaks It leaks very readily, it ignites very readily, it burns with a wide range of air:fuel proportions, it burns with a high flame speed, and it burns hot. Hydrogen is ... not a good choice for something to reticulate widely around the world. Edit: That's leaving aside its low energy density. You need three times the volume of hydrogen as natural gas for the same quantity of heat, so existing pipe networks are unlikely to be useful. Global warming potential is off to the side of all this.
- ncmncm 4y ago
  Yet, millions of tons of hydrogen are today produced, transported and used. There is nothing special about the volumetric energy density of NG. H2 has to move faster, if carried in the same pipe for the same use. Its lower viscosity means it can. Municipal gas networks used to carry "lamp gas", a mix of CO and H2, in cast-iron pipes.