ABSTRACT
To solve the problem concerning the exhaustion of fossil fuels and global warming,sustainablesocietyusingrenewableenergyisexpected.Renewableenergy isenvironment-friendlyandisderivedfromsolarheat,windpower,geothermal, andhydropower,althoughtheirpowerdensitiesarelowand»uctuateovertime. Therefore,renewableenergycanbeconvertedintosecondaryenergysourceslike electricity and hydrogen. Electricity and hydrogen are stored in batteries and highpressurecylinders,respectively.Hydrogenisasecondaryenergythatstoresand transports renewable energy because of its high energy density.
