To solve problems of the global environment,the realization of hydrogen economy is now in strong demand among the international community.Four key technologies are necessary for hydrogen economy : hydrogen production,transportation,storage,and utilization. In this paper, the current status with respect to hydrogen storage technolo-gies, which include high−pressure storage, liquid hydrogen, metal hydrides, and other storage materials,is summarized. In addition,one of the promising hydrogen

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... e materials,metal hydride,is described in detail.Hydrogen ab/desorption reactions of metal hydride are associated with heat.Heat management,as well as compactness and lightweight,therefore,is required for metal hydride hydrogen storage.In order to optimize the balance between compactness and high performances(especially the hydrogen flow rate)of the storage system,appropriate heat management has to be implemented in the design of metal hydride storage tanks. A hydrogen refueling station,a fuel cell−powered underwater vehicle,and a fuel cell −powered cell phone are described as application examples of metal hydride storage in Japan.