4 ms·

At small scale, this is correct. At very large scale, hydrogen is incredibly easy to store. You can just fill up and old depleted gas well and store terawatt-ho

At small scale, this is correct. At very large scale, hydrogen is incredibly easy to store. You can just fill up and old depleted gas well and store terawatt-hours of energy easily. Germany has enough gas well storage to survive several months. This infrastructure is currently used for natural gas, but it can be repurposed for hydrogen. I still think that commoditized battery storage will win in the end, but storage cost is not an argument against hydrogen.

_ph_ 6y ago
Besides it is not trivial to repurpose natural gas storage for hydrogen - you need an entirely different level of tightness, you would be disappointed about the amount of energy you can store this way, as hydrogen is way less dense than natural gas, so the capacity of the storage would be poor.
- rklaehn 6y ago
  For very large scale storage we are not talking about steel pressure vessels that are subject to hydrogen embrittlement, but depleted natural gas reservoirs which are just gas-tight geological formations and have no issues whatsoever with hydrogen embrittlement. For small and medium scale storage you are right. Which is why hydrogen for cars and even trucks is a bad idea.
  - _ph_ 6y ago
    And you would get much less hydrogen stored at the same pressure than methane. To store reasonable amounts of hydrogen, you need very high pressures. Gas powered cars use like 60 bars of pressure, hydrogen 700.
    - rklaehn 6y ago
      Yes, that is correct. But the end to end efficiency of Electricity -> H2 -> Electricity is much better than Electricity -> H2 -> CH4 -> Electricity. Hydrogen at 0°C and 100 Bar (~10MPa) has a density of 8.3447 kg/m^3. It has an energy density of 120 MJ/kg. So about 33 kWh/kg. So you end up with 278 kWh/m^3. Now of course you have to multiply this by the H2->Electricity efficiency. Let's be very pessimistic and take 0.6 or 60%, which is what a gas turbine plant can achieve today. You end up with 166 kWh/m^3 of usable electricity per cubic meter. One of many german gas storage facilities https://www.nafta-speicher.de/en/company https://www.nafta-speicher.de/en/company has a volume of 1.8e9 m^3. That translates into 300 Terawatt-Hours of storage capacity for just this one facility.
      - _ph_ 6y ago
        And at what pressure do those storage facilities operate?
        rklaehn 6y ago
        Can be quite high, in the 100 bar range and above.
imtringued 6y ago
Right now the German gas infrastructure can only handle a hydrogen content of around 10% or 20% with modest infrastructure upgrades. This is why there are projects where that hydrogen is further processed into methane at which point all of it is compatible with the existing gas infrastructure.
- rklaehn 6y ago
  That is a limitation of the pipeline infrastructure, because of hydrogen embrittlement of steel pipes. It is not a limitation of the large storage facilities, which are just exhausted natural gas wells and work just fine with hydrogen. The cost of outfitting one such facility with steel pipes that are not subject to hydrogen embrittlement is trivial compared to the cost for the electrolysis units etc. Note that I am not a big fan of hydrogen at all. But large scale storage is one of its few redeeming qualities.

_ph_ 6y ago

Besides it is not trivial to repurpose natural gas storage for hydrogen - you need an entirely different level of tightness, you would be disappointed about the amount of energy you can store this way, as hydrogen is way less dense than natural gas, so the capacity of the storage would be poor.

rklaehn 6y ago
For very large scale storage we are not talking about steel pressure vessels that are subject to hydrogen embrittlement, but depleted natural gas reservoirs which are just gas-tight geological formations and have no issues whatsoever with hydrogen embrittlement. For small and medium scale storage you are right. Which is why hydrogen for cars and even trucks is a bad idea.
- _ph_ 6y ago
  And you would get much less hydrogen stored at the same pressure than methane. To store reasonable amounts of hydrogen, you need very high pressures. Gas powered cars use like 60 bars of pressure, hydrogen 700.
  - rklaehn 6y ago
    Yes, that is correct. But the end to end efficiency of Electricity -> H2 -> Electricity is much better than Electricity -> H2 -> CH4 -> Electricity. Hydrogen at 0°C and 100 Bar (~10MPa) has a density of 8.3447 kg/m^3. It has an energy density of 120 MJ/kg. So about 33 kWh/kg. So you end up with 278 kWh/m^3. Now of course you have to multiply this by the H2->Electricity efficiency. Let's be very pessimistic and take 0.6 or 60%, which is what a gas turbine plant can achieve today. You end up with 166 kWh/m^3 of usable electricity per cubic meter. One of many german gas storage facilities https://www.nafta-speicher.de/en/company https://www.nafta-speicher.de/en/company has a volume of 1.8e9 m^3. That translates into 300 Terawatt-Hours of storage capacity for just this one facility.
    - _ph_ 6y ago
      And at what pressure do those storage facilities operate?
      - rklaehn 6y ago
        Can be quite high, in the 100 bar range and above.

imtringued 6y ago

Right now the German gas infrastructure can only handle a hydrogen content of around 10% or 20% with modest infrastructure upgrades. This is why there are projects where that hydrogen is further processed into methane at which point all of it is compatible with the existing gas infrastructure.

rklaehn 6y ago
That is a limitation of the pipeline infrastructure, because of hydrogen embrittlement of steel pipes. It is not a limitation of the large storage facilities, which are just exhausted natural gas wells and work just fine with hydrogen. The cost of outfitting one such facility with steel pipes that are not subject to hydrogen embrittlement is trivial compared to the cost for the electrolysis units etc. Note that I am not a big fan of hydrogen at all. But large scale storage is one of its few redeeming qualities.