Several models of FC vehicles fuell

Several models of FC vehicles fuelled by H2 have been produced by many car’sindustries in the past two decades, characterized by interesting performance andpromising reliability (i.e., Mercedes-Benz presented at the end of 2009 the newmodel B class F-Cell equipped with new generations of fuel cells, Li-ion batteries,and advanced fuel storage tanks). Other solutions with the stack fed with liquidfuels (methanol, gasoline, and diesel) have been also proposed, but they require anon-board fuel processor to transform the liquid mixture into hydrogen. In this casethe impact of the fuel processor on the choice of the hybridization level for thewhole propulsion system (see Sect. 5.5) and on stack durability needs to becarefully considered. Dynamic response of FCS with processor unit would be tooslow mainly because of its thermal inertia, implying that the stack has to operatealmost in steady state conditions, while the unavoidable presence of some compounds in reformer outlet stream, such as CO or NH3, also in very low concentrations, are dangerous contaminants for the activity of stack electrodes. Recently it has been estimated that start-up time would be less than 4 min to lower the CO level present in the stream at acceptable values [1], but long-term durability of stacks fed by reformate stream is far to be demonstrated.