ABSTRACT
There is no universally accepted definition of “hydrogen economy,” but it is generally viewed as the replacement of the vast majority of petroleum fuels used by transportation vehicles of all kinds (automobiles, trucks, trains, and aircraft) with hydrogen that is burned in internal-combustion engines, external-combustion (jet) engines, or preferably, used in fuel cells to more efficiently generate power for transportation. This entry reviews the hydrogen economy from a basic energy engineering viewpoint to identify potential impediments and opportunities and to quantify the tasks involved in terms of energy and materials required in bringing the hydrogen economy into existence.
