Hydrogen is an ideal energy carrier that can be produced cleanly through water electrolysis, burned and then turned into water again. However, there are a series of problems. The energy density per unit of mass is high, but the energy density per unit of volume is rather low because of hyd...
Except that we could use coal and nuclear to create liquid fuels if, for some reason, all the oil vanished in 20 years. It would also be a lot less energy intensive to do so – there are even engine designs that allow use of a coal particulate and water slurry instead of resorting to...