Originally Posted by
rower
You can not use nuclear power to extract hydrogen from water or fossil fuels because all methods we know today are inefficient.
You have to generate 3 kWh of electricity in a nuclear plant to obtain hydrogen that, as fuel for a vehicle, will produce just 1 kWh of mechanical work.
Sure you can. It doesn't have to be efficient as long as it's green. More nuclear doesn't increase carbon (other than the inevitable carbon overhead associated with any industry and the people who work there).
Also your math assumes that the H2 is cooled to a cryogenic state which requires additional energy. That's correct for airplanes, but worth noting that if you wanted to replace natural gas with H2, you could get about 70% conversion efficiency out of electrolysis as long as the H2 gas produced is simply pumped directly into a pipeline, vice cooled or compressed for vehicle storage tanks. My SWAG would be that we'll just go all-electric for residential and light industry just due to the potential hassle (and increased danger) of plumbing H2 gas into everybody's homes. H2 gas might be useful as a surge accumulator though, since generating capacity could make H2 all night which would then cover the normal morning surge when people get up, turn on the heater and take hot showers. Although solar naturally tends to balance out that peak cycle if you have enough of it.
The real obstacle for H2 in planes is energy density, ie storage takes up too much volume on the plane which means more structure, which means more weight, which requires more fuel, etc, etc. might be able to mitigate with large-volume designs, ie BWB.