One potential solution for vehicular fuel storage involves the use of metal hydrides, specially formulated alloys that soak up hydrogen much like a sponge absorbs water. A fair number of metal hydrides exist, but the ideal alloy for hydrogen storage has yet to be developed. Desirable features include the ability to store huge amounts of hydrogen at low charging pressures, fast release of the gas at low operating temperatures, light weight, and reasonable cost. Existing hydrides require unfortunate tradeoffs among these parameters. Iron-titanium, for example, is inexpensive and can release hydrogen at a low 100 F. says Livesay.
Magnesium alloys are far lighter and can hold much more hydrogen.
This much heat cannot be supplied by mere engine exhaust. More research into metal hydrides is needed to exploit the potential for enormous storage density and convenient use. These tests were largely successful. Calif. This was the first hydrogen-fueled vehicle placed in regular passenger service by a transit authority. The bus performed impressively, though the iron-titanium storage tank had to be recharged every 200 miles.