ABSTRACT
One of the critical challenges of the ongoing intensive effort toward the acceptanceandgenericuseofH2 as energy carrier concerns the ef„cient storageofhydrogen(Felderhoffetal.2007).Twokindsofstoragefunctions withverydifferentrequirementsareconsidered.Systemsusedforstationary applicationscanoccupyalargearea,employmultistepchemicalcharging/ rechargingcycles,operateathightemperatureandpressure,andbalance slow kinetics with capacity. On the other hand, H2 storage for transportationmustoperatewithinminimumvolumeandweightspeci„cations,supplyenoughH2 to enable an approximately 500 km driving range, charge/ rechargenearambienttemperature,andprovideH2 at rates fast enough for fuelcelllocomotionofvehicles.Intermsofenergycontent,1kgofH2 can replaceabout3kgofgasoline.However,hydrogenisagasatstandardpressureandtemperature(SPT)andthereforeithasalowvolumetricdensityso thatmorethan1.3×104 L of H2 gas (volume of a midsize car) are necessary toreplacejust3.79LofgasolineatSPT(Graetz2009).TheH2 storage requirementsfortransportationapplicationsarethusfarmorestringentanddif„- culttoachievethanthoseforstationaryapplications.Existingtechnologyfor hydrogenstorageislimitedtotankscarryingcompressedgasorcryogenic liquid,bothofwhichareusedatthemomentindemonstrationvehicles. Although gas and liquid storage are useful as temporary options in a provisionalhydrogeneconomy,theyfallfarshortoftheaggressiveECandU.S. DepartmentofEnergy(DOE)targets(6.0wt%and45g/Lbytheyear2010, and9.0wt%and81g/Lby2015)foron-boardH2 storage systems due to the required tank volume and energy intensity, as well as safety reasons.
