> As I understand it, the production of complex hydrocarbons that can be used as a replacement for jet fuel is even more inefficient when compared to the production of hydrogen, as many of the known processes that start from CO2 actually use hydrogen in the process.
Sure.
Here's the thing though: we can efficiently store those complex hydrocarbons. We can't efficiently store hydrogen. It destroys containers, and can escape any container we have devised(unless in liquid form?)
Many of the proponents of electrolysis claim that renewables will make energy a non-factor(or they'll propose nuclear power, etc). If that's the case, then add another step to capture CO2 as well.
The idea here is to do basically a cryoplane. Hydrogen can be generated on demand for the planes to refuel and can be stored highly compressed for that particular use case. We're not talking about using it for GA or cars.
As for volume - there's a reason why they call them cryoplanes ;)
From Airbus - Liquid hydrogen is used as fuel for combustion with oxygen.
Cryogenic fuels also give possible efficiency boost by precooling inlet air, but that's bigger gain for Sabre-style engines (HOTOL, Skylon, etc. SSTOs) or for efficient supersonic airliners (proposed derivation of Tu-144 used liquid H2 to gain low operating costs for it's typical Ma 2 cruise speed.)
Sure.
Here's the thing though: we can efficiently store those complex hydrocarbons. We can't efficiently store hydrogen. It destroys containers, and can escape any container we have devised(unless in liquid form?)
Many of the proponents of electrolysis claim that renewables will make energy a non-factor(or they'll propose nuclear power, etc). If that's the case, then add another step to capture CO2 as well.
> Finally, hydrogen has a great energy / kg ratio
Yes but energy per unit of volume is terrible.