Ok, let's see here... Hydrogen has 142 MJ/kg and at 700 bar is 42 kg/m^3. "At this pressure, 5 kg of hydrogen can be stored in a 125-liter tank." (https://ener

Ok, let's see here... Hydrogen has 142 MJ/kg and at 700 bar is 42 kg/m^3. "At this pressure, 5 kg of hydrogen can be stored in a 125-liter tank." (https://energies.airliquide.com/resources-planet-hydrogen/how-hydrogen-stored https://energies.airliquide.com/resources-planet-hydrogen/ho...). That's 710 MJ in 125-liter tank. I couldn't find the stats on a 127-liter tank, but a 49-liter, 300 ft^3 tank is 139 lbs, or 63 kg. That would hold about 2kg of hydrogen. (https://www.mathesongas.com/industrialgas/pdfs/Industrial-Cylinder-Dimensions.pdf https://www.mathesongas.com/industrialgas/pdfs/Industrial-Cy...) That's 280 MJ in 65 kg, or 4.3 MJ/kg. A lithium ion battery is 0.36–0.875 MJ/kg, but jet fuel is 43 MJ/kg. (https://en.wikipedia.org/wiki/Energy_density https://en.wikipedia.org/wiki/Energy_density)