Originally Posted by
Null Orifice
And look how that ended!
The issue with hydrogen is not weight of the fuel, but rather volume and storage method. If it's gaseous compressed hydrogen the tanks weigh a ton and you need a lot of them. If it's liquid hydrogen there are other issues storing and using a cryogenic fluid, as well as volume. I've run the numbers several times and I just don't see how it will be a viable aircraft fuel source. Buses and trucks, yes; flying things not so much.
There is also the issue of hydrogen production. The most common method is a steam reforming reaction with natural gas (methane), stripping the carbon and producing H2. The is a high temperature energy intensive process and produces carbon monoxide as a by-product. There is of course electrolysis, breaking down water molecules to produce hydrogen and oxygen, the reverse of the reaction in the fuel cell that produces electricity. Again, this requires large amounts of electricity - at least the same amount as that produced by the fuel cell when it recombines the hydrogen with oxygen to produce water.