Metal hydride storage requirements for transportation applications

Vehicular application of hydrogen requires a lightweight, compact, safe and economic containment method. Although various hydrogen storage technologies are presently available, none completely satisfies all of the requirements. Fuel cells use oxygen and hydrogen as the fuel and produce water as the only product of combustion. Fuel cells offer the best criteria for meeting the requirement of zero emission vehicles (ZEVs). Since fuel cells produce waste heat at much lower temperature than internal combustion engines, the operating temperature of the storage system is most important. Since fuel cells require high purity H/sub 2/, the ability of the storage system to deliver high purity hydrogen is also of primary importance. This paper aims at defining the design goals for hydride storage systems to be used with future fuel cell vehicle applications. The major conclusions and recommendations of this paper are: only three systems for on-board hydrogen storage appear close to commercialization-compressed gas at high pressure (3-5 kpsi, composite cylinder), liquid hydrogen, and low temperature metal hydrides. No single storage technology satisfies all criteria for on-board storage of H/sub 2/. Metal hydrides offer high volumetric storage densities and highest crash worthy structure but suffer from excessive weight and very high cost. Off-road locomotives may be the best starting point for launching fuel cell transport.