International Journal of Hydrogen Energy 30 (2005) 425 – 435 www.elsevier.com/locate/ijhydene Fuel effects on start-up energy and efﬁciency for automotive PEM fuel cell systems Troy A. Semelsberger ∗ , Rodney L. Borup Materials Science & Technology Division, Los Alamos National Laboratory, P.O. Box 1663, Mail Stop J579, Los Alamos, NM 87545, USA Received 14 July 2004; received in revised form 8 October 2004; accepted 1 November 2004 Abstract This paper investigates the effects of various fuels on hydrogen production for automotive PEM fuel cell systems. Gasoline, methanol, ethanol, dimethyl ether and methane are compared for their effects on fuel processor size, start-up energy and overall efﬁciencies for 50 kW e fuel processors. The start-up energy is the energy required to raise the temperature of the fuel processor from ambient temperature (20 ◦ C) to that of the steady-state operating temperatures. The fuel processor modeled consisted of an equilibrium-ATR (autothermal), high-temperature water gas shift (HTS), low-temperature water gas shift (LTS) and preferential oxidation (PrOx) reactors. The individual reactor volumes with methane, dimethyl ether, methanol and ethanol were scaled relative to a gasoline-fueled fuel processor meeting the 2010 DOE technical targets. The modeled fuel processor volumes were, 25.9 L for methane, 30.8 L for dimethyl ether, 42.5 L for gasoline, 43.7 L for ethanol and 45.8 L for methane. The calculated fuel processor start-up energies for the modeled fuels were, 2712 kJ for methanol, 3423 kJ for dimethyl ether, 6632 kJ for ethanol, 7068 kJ for gasoline and 7592 kJ for methane. The modeled overall efﬁciencies, correcting for the fuel processor start-up energy using a drive cycle of 33miles driven per day, were, 38.5% for dimethyl ether, 38.3% for methanol, 37% for gasoline, 34.5% for ethanol and 33.2% for methane assuming a steady-state efﬁciency of 44% for each fuel.  2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. Keywords: Fuel cell feeds; Dimethyl ether; Gasoline; Natural gas; Ethanol; Methanol; Start-up energy; Fuel processor efﬁciency; Fuel processor volumes; Autothermal systems 1. Introduction An integrated fuel cell power system for automotive appli- cations is a topic that has generated widespread interest be- cause of its potential for increasing fuel efﬁciency. Primary issues for the development and commercialization of inte- grated fuel cell power systems for automotive applications are both political and environmental. Political issues include the need to remove or relax the US’ dependence on foreign oil which is accomplished by increasing efﬁciency, while ∗ Corresponding author. Tel.: +1 505 665 4766; fax: +1 505 665 9507. E-mail address: troy@lanl.gov (T.A. Semelsberger). 0360-3199/$30.00  2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2004.11.007 environmental issues include reduction in vehicle emissions such as pollutants; e.g., NO x , CO, hydrocarbons and SO x , and greenhouse gases (i.e., CO 2 ). Many developers have concentrated research efforts on gasoline- and diesel-reformate fuel cells since gasoline and diesel are the readily available transportation fuels. How- ever, fuel cell systems for automotive applications with gasoline as the hydrogen source are a technically challeng- ing endeavor. A gasoline-fueled fuel processor is potentially the most technically challenging issue delaying the com- mercialization of fuel cell powered passenger vehicles due to the complexities of gasoline fuel processing. Technical issues include, but are not limited to, start-up energy and time, carbon formation, high operating temperatures, sulfur poisoning and large fuel processor mass and volume [1–10].