RE: Airship Hydrogen resupply
September 5, 2016 at 9:51 pm
(This post was last modified: September 5, 2016 at 10:03 pm by JuliaL.)
Where did you find the 12m3/kWH number for electrolysis?
Grabbed from Wikipedia:
"a 100%-efficient electrolyser would consume 39.4 kilowatt-hours per kilogram (142 MJ/kg) of hydrogen,"
https://en.wikipedia.org/wiki/Electrolysis_of_water
This is ~40kWH per 11 cubic meters at STP.
http://www.engineeringtoolbox.com/gas-de...d_158.html
Your 4100kWH would then yield 4100kWH/(40kWH/11m3)=~1200m3.
But your genset is (charitably) 20% efficient, so you are only going to get 240m3.
Sorry
I'll take a different tack.
7000m3 of h2 at STP is going to mass 630kg with a MW of ~2gm/mol this is ~310000mols
You can get H2 from reacting aluminum with water using NaOH.
The following are possible reactions of aluminum with water:
2Al + 6H2O = 2Al(OH)3+ 3H2
2Al + 4H2O = 2AlO(OH) + 3H2
2Al + 3H2O = Al2O3+ 3H2
The first reaction forms the aluminum hydroxide bayerite (Al(OH)3) and hydrogen, the second
reaction forms the aluminum hydroxide boehmite (AlO(OH)) and hydrogen, and the third
reaction forms aluminum oxide and hydrogen.All these reactions are thermodynamically favorable from room temperature past the melting point of aluminum (660oC). All are also highly exothermic.
https://www1.eere.energy.gov/hydrogenand...drogen.pdf
Assume you can come up with the tools & plumbing, the reactions complete & there are no losses.
You'll have to scavenge 310000*2/3 mols of aluminum from your zeppelin (a mass of 5600kg) and make lots of NaOH from wood ash you make burning the hardwood forest you conveniently landed in.
This way you can use the ICE fuel to motor home.
You might include a 'will it make it home' sub-plot out of the fact that the crew had to rip 5.6 metric tons of structure out of "Afrika-Schiff" to generate her lifting gas.
Sacrifice an engine?
Grabbed from Wikipedia:
"a 100%-efficient electrolyser would consume 39.4 kilowatt-hours per kilogram (142 MJ/kg) of hydrogen,"
https://en.wikipedia.org/wiki/Electrolysis_of_water
This is ~40kWH per 11 cubic meters at STP.
http://www.engineeringtoolbox.com/gas-de...d_158.html
Your 4100kWH would then yield 4100kWH/(40kWH/11m3)=~1200m3.
But your genset is (charitably) 20% efficient, so you are only going to get 240m3.
Sorry
I'll take a different tack.
7000m3 of h2 at STP is going to mass 630kg with a MW of ~2gm/mol this is ~310000mols
You can get H2 from reacting aluminum with water using NaOH.
The following are possible reactions of aluminum with water:
2Al + 6H2O = 2Al(OH)3+ 3H2
2Al + 4H2O = 2AlO(OH) + 3H2
2Al + 3H2O = Al2O3+ 3H2
The first reaction forms the aluminum hydroxide bayerite (Al(OH)3) and hydrogen, the second
reaction forms the aluminum hydroxide boehmite (AlO(OH)) and hydrogen, and the third
reaction forms aluminum oxide and hydrogen.All these reactions are thermodynamically favorable from room temperature past the melting point of aluminum (660oC). All are also highly exothermic.
https://www1.eere.energy.gov/hydrogenand...drogen.pdf
Assume you can come up with the tools & plumbing, the reactions complete & there are no losses.
You'll have to scavenge 310000*2/3 mols of aluminum from your zeppelin (a mass of 5600kg) and make lots of NaOH from wood ash you make burning the hardwood forest you conveniently landed in.
This way you can use the ICE fuel to motor home.
You might include a 'will it make it home' sub-plot out of the fact that the crew had to rip 5.6 metric tons of structure out of "Afrika-Schiff" to generate her lifting gas.
Sacrifice an engine?
So how, exactly, does God know that She's NOT a brain in a vat? 
