A hydrogen vehicle
A hydrogen vehicle is an automobile which uses hydrogen as its primary source of power for locomotion. These cars generally use the hydrogen in one of two methods: combustion or fuel-cell conversion. In combustion, the hydrogen is "burned" in engines in fundamentally the same method as traditional gasoline cars. In fuel-cell conversion, the hydrogen is turned into electricity through fuel cells which then powers electric motors. With either method, the major byproduct from the spent hydrogen is water that can move also a micro-turbine.
Hydrogen can be obtained from decomposition of methane (natural gas), coal (by a process known as coal gasification), liquid petroleum products, biomass (biomass gasification), high heat sources (by a process called thermolysis), or from water using electricity (electrolysis). A primary benefit of using pure hydrogen as a power source is that it uses oxygen from the air to produce water vapor as exhaust (and very little nitrogen oxides from the nitrogen in the air when burning at high temperatures). We could move the source of atmospheric pollution from many cars, back to a single power plant, where it can be more easily dealt with. That would mean that we would accept the transmission line loses and inefficiencies of separating our own hydrogen and compressing it ourselves. We could do better now by using a Plug-in hybrid electric vehicle, that is far more feasible. There are no hydrogen cars current, or anticipated, which use the fusion of hydrogen as a power source.
The major challenges in using hydrogen in cars, are the very high costs and the low energy efficiencies, with low probabilities so far, for successful solutions for the several challenges.