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Double walled high vacuum tanks that vent hydrogen gas if left unused for less than day and empty themselves after 10 days. Liquid hydrogen at -253c that is mo

Double walled high vacuum tanks that vent hydrogen gas if left unused for less than day and empty themselves after 10 days. Liquid hydrogen at -253c that is more energy intensive to make than high pressure. Not sure I see that being practical.

semi-extrinsic 5y ago
This information is just wrong. Air Liquide built automotive size LH2 tanks using multilayer insulation in the early 2000s that had 3 days of autonomy (time before first venting) and 3% per day boil-off after that. For trucks where you need bigger tanks, both autonomy and boil-off rate improve by themselves due to the square-cube-law. And you can use the boil-off to charge the batteries in your hybrid electric powertrain, run auxiliary systems etc. The LH2 trucks currently under planning have sophisticated fuel management systems where the driver inputs where she will stop and for how long, and the truck will optimize LH2 consumption and battery SoC before arriving at the stop point. As for LH2 versus compressed: do you actually know how energy demanding a hydrogen compression train is? Compressing a low molecular weight gas to 700 bar is just fundamentally inefficient. At the scale required for mass adoption of hydrogen fuels, both compression and liquefaction are talking 6-8 kWh/kg. For comparison the energy content in hydrogen itself is 33 kWh/kg. So naturally there is great interest in recovering as much as possible of that work before consumption.
- SigmundA 5y ago
  This is the BMW tank I got those figures from which looks to be manufactured by Air Liquide [1]: "To stay a liquid, hydrogen must be cooled and maintained at cryogenic temperatures of, at warmest, −253 °C (20.1 K; −423.4 °F). When not using fuel, the Hydrogen 7’s hydrogen tank starts to warm and the hydrogen starts to vaporize. Once the tank’s internal pressure reaches 87 psi, at roughly 17 hours of non-use, the tank will safely vent the building pressure. Over 10–12 days, it will completely lose the contents of the tank because of this" At that temperature even sloshing around adds enough energy to heat and cause venting much sooner another reason its not great for mobile use. Looks like Air Liquide made a different one that you are quoting perhaps an improvement, still high vacuum double walled, so you lose all your fuel in a month instead, thats progress. This shows liquefaction to be about twice as energy intensive as compression (1.3 vs 3.4 kWh/kg theoretical 6 vs 13 kWh/kg actual) [2] So please point me to better info. 1. https://en.wikipedia.org/wiki/BMW_Hydrogen_7 https://en.wikipedia.org/wiki/BMW_Hydrogen_7 2. https://www.hydrogen.energy.gov/pdfs/9013_energy_requirements_for_hydrogen_gas_compression.pdf https://www.hydrogen.energy.gov/pdfs/9013_energy_requirement...

semi-extrinsic 5y ago

This information is just wrong. Air Liquide built automotive size LH2 tanks using multilayer insulation in the early 2000s that had 3 days of autonomy (time before first venting) and 3% per day boil-off after that. For trucks where you need bigger tanks, both autonomy and boil-off rate improve by themselves due to the square-cube-law. And you can use the boil-off to charge the batteries in your hybrid electric powertrain, run auxiliary systems etc. The LH2 trucks currently under planning have sophisticated fuel management systems where the driver inputs where she will stop and for how long, and the truck will optimize LH2 consumption and battery SoC before arriving at the stop point. As for LH2 versus compressed: do you actually know how energy demanding a hydrogen compression train is? Compressing a low molecular weight gas to 700 bar is just fundamentally inefficient. At the scale required for mass adoption of hydrogen fuels, both compression and liquefaction are talking 6-8 kWh/kg. For comparison the energy content in hydrogen itself is 33 kWh/kg. So naturally there is great interest in recovering as much as possible of that work before consumption.

SigmundA 5y ago
This is the BMW tank I got those figures from which looks to be manufactured by Air Liquide [1]: "To stay a liquid, hydrogen must be cooled and maintained at cryogenic temperatures of, at warmest, −253 °C (20.1 K; −423.4 °F). When not using fuel, the Hydrogen 7’s hydrogen tank starts to warm and the hydrogen starts to vaporize. Once the tank’s internal pressure reaches 87 psi, at roughly 17 hours of non-use, the tank will safely vent the building pressure. Over 10–12 days, it will completely lose the contents of the tank because of this" At that temperature even sloshing around adds enough energy to heat and cause venting much sooner another reason its not great for mobile use. Looks like Air Liquide made a different one that you are quoting perhaps an improvement, still high vacuum double walled, so you lose all your fuel in a month instead, thats progress. This shows liquefaction to be about twice as energy intensive as compression (1.3 vs 3.4 kWh/kg theoretical 6 vs 13 kWh/kg actual) [2] So please point me to better info. 1. https://en.wikipedia.org/wiki/BMW_Hydrogen_7 https://en.wikipedia.org/wiki/BMW_Hydrogen_7 2. https://www.hydrogen.energy.gov/pdfs/9013_energy_requirements_for_hydrogen_gas_compression.pdf https://www.hydrogen.energy.gov/pdfs/9013_energy_requirement...