Is the storage of hydrogen efficient, space wise?
Hydrogen does occupy more space than any other fuel, whether it be in gaseous or liquid state. However, new tanks are providing for more storage of compressed hydrogen gas. The U.S. government recently certified 5,000 psi hydrogen tanks for use in automobiles. The German government has certified 10,000 psi tanks; and the U.S. is soon to follow. Dynetek Industries has also developed a 12,500 psi tank that should be certified within the next two years. BMW uses liquid hydrogen, which provides more hydrogen per volume than gaseous hydrogen, but is more expensive to produce. Liquid hydrogen tanks also require venting of the gas as it warms in the tank. BMW claims that their tanks will not require any venting for up to one week.
