Abstract:Hydrogen is an especially attractive transportation fuel. It is the least populating fuel available, and can be produced anywhere there is water and a clean source of electricity. A fuel cycle in which hydrogen is produced by solar-electrolysis of water, or by gasification of renewably grown biomass, and then used in a fuel-cell powered electric-motor vehicle (FCEV), would produce little or no local, regional or global pollution. Hydrogen FCEVs would combine the best features of battery-powered electric vehicles (BPEVS)-zero emissions, high efficiency, quiet operation and long life-with the long range and fast refueling time of internal-combustion-engine vehicles (ICEVs). If fuel-cell technology develops as hoped, then hydrogen FCEVs will be a significant advance over both hydrogen ICEVs and solar BPEVs: they will be cleaner and more efficient than hydrogen ICEVs, have a much shorter refueling time than BPEVs and have a lower life-cycle cost than both. Solar-hydrogen fuel-cell vehicles would be general-purpose zero-emission vehicles, and could be an important component of a strategy for reducing dependence on imported oil, mitigating global warming and improving urban air quality, at an acceptable cost.