How Much Energy Can Extracted From A Kilogram Of Hydrogen?
This article on EnergyH, is entitled About Hydrogen Energy.
This is said.
Hydrogen has an energy density of 39 kWh/kg, which means that 1 kg of hydrogen contains 130 times more energy than 1kg of batteries. So lots of energy can be stored with hydrogen in only a small volume.
But as in most things in life, you can’t have it all as fuel cells are not 100 % efficient.
Wikipedia has a sub-section which gives the in-practice efficiency of a fuel cell, where this is said.
In a fuel-cell vehicle the tank-to-wheel efficiency is greater than 45% at low loads and shows average values of about 36% when a driving cycle like the NEDC (New European Driving Cycle) is used as test procedure. The comparable NEDC value for a Diesel vehicle is 22%. In 2008 Honda released a demonstration fuel cell electric vehicle (the Honda FCX Clarity) with fuel stack claiming a 60% tank-to-wheel efficiency.
For the purpose of this exercise, I’ll assume a conservative forty percent.
This means that a kilogram of hydrogen would generate 16 kWh
Raise that efficiency to fifty percent and 19 kWh would be generated.
Conclusion
Fuel cell efficiency will be key.
The Anonymous Widower 
Hydrogen is light, but at STP bulky – 1kg occupies 11,200l (over 11 cubic metres) and won’t liquify by pressure alone (unlike LPG).
Older readers may have seen vehicles using gas as fuel: –
https://www.build-a-gasifier.com/gas-bag-buses/
https://www.lowtechmagazine.com/2011/11/gas-bag-vehicles.html
or even
https://www.reddit.com/r/OldSchoolCool/comments/2mgkj3/female_taxi_driver_with_a_gas_bag_vehicle_using/
Hydrogen can also be stored in palladium (~ 200 volumes), but the metal costs ~$5 per gram
Comment by R. Mark Clayton | May 9, 2019 |
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