Journal of Power Sources 160 (2006) 474–484 Techno-economic analysis of fuel cell auxiliary power units as alternative to idling Semant Jain, Hsieh-Yeh Chen, Johannes Schwank ∗ Department of Chemical Engineering, 2300 Hayward, University of Michigan, Ann Arbor, MI 48109, United States Received 3 August 2005; received in revised form 28 January 2006; accepted 31 January 2006 Available online 3 March 2006 Abstract This paper presents a techno-economic analysis of fuel-cell-based auxiliary power units (APUs), with emphasis on applications in the trucking industry and the military. The APU system is intended to reduce the need for discretionary idling of diesel engines or gas turbines. The analysis considers the options for on-board fuel processing of diesel and compares the two leading fuel cell contenders for automotive APU applications: proton exchange membrane fuel cell and solid oxide fuel cell. As options for on-board diesel reforming, partial oxidation and auto-thermal reforming are considered. Finally, using estimated and projected efficiency data, fuel consumption patterns, capital investment, and operating costs of fuel-cell APUs, an economic evaluation of diesel-based APUs is presented, with emphasis on break-even periods as a function of fuel cost, investment cost, idling time, and idling efficiency. The analysis shows that within the range of parameters studied, there are many conditions where deployment of an SOFC-based APU is economically viable. Our analysis indicates that at an APU system cost of $ 100 kW -1 , the economic break-even period is within 1 year for almost the entire range of conditions. At $ 500 kW -1 investment cost, a 2-year break-even period is possible except for the lowest end of the fuel consumption range considered. However, if the APU investment cost is $ 3000 kW -1 , break-even would only be possible at the highest fuel consumption scenarios. For Abram tanks, even at typical land delivered fuel costs, a 2-year break-even period is possible for APU investment costs as high as $ 1100 kW -1 . © 2006 Elsevier B.V. All rights reserved. Keywords: Abram tanks; Economics; Fuel cells; Heavy-duty trucks; Idling; Reforming 1. Introduction Heavy-duty trucks spend considerable amounts of time idling. Idling can be classified into two broad categories: non- discretionary and discretionary [1]. Non-discretionary idling occurs after engine start-up and intermittently in heavy traf- fic. Discretionary idling occurs during loading/unloading and Abbreviations: ACI, actual cost of idling ($ (unit time) -1 ); APU, fuel cell as APU; BEP, break-even period (years); CI, cost of idling ($(unit time) -1 ); DE, idling diesel engine; DEIC, diesel engine idling cost ($ year -1 ); DR, diesel rate ($ gal -1 ); FC, fuel consumption (gal (unit time) -1 ); FCC, fuel cell cost ($ year -1 ); FCIC, fuel cell investment cost ($); FCRC, annual fuel cell running cost ($ year -1 ); GT, gas turbine engine for M1, M1A1 tanks; IFC, idled fuel cost ($ gal -1 ); IR, investment rate ($ kW -1 ); IT, idling time (h (unit time) -1 ); MR, maintenance rate ($ h -1 ); RR, fuel-cell APU rating required (kW); TD, average number of trucking days in a given unit of time (days (unit time) -1 ) ∗ Corresponding author. Tel.: +1 734 764 3374; fax: +1 734 763 0459. E-mail addresses: semant@umich.edu (S. Jain), schwank@umich.edu (J. Schwank). during stand-by periods in rest stops where the idling engine mainly serves to maintain driver comfort levels. Idling engines operate low levels of efficiency, suffer considerable tear and wear, and cause emissions of NO x and particulate matter, along with some hydrocarbons, carbon monoxide and carbon dioxide. The US Department of Energy [2] estimates that annually $ 1 billion worth of diesel fuel is consumed during idling, with an additional $ 1 billion spent on increased engine maintenance costs. The high cost of idling has prompted many of the large fleets to put voluntary restrictions on idling [2]. Truck idling has attracted increased attention from local and federal air quality regulators, and several municipalities, such as the eight-county Houston, TX area, and New York City are considering regula- tions limiting truck idling. This has created an impetus to look for technically and economically viable alternatives to discre- tionary idling, such as, for example, truck stop electrification, batteries, or auxiliary power units. In the present work, we carry out an economic analysis of the break-even period of using fuel-cell-based APUs to replace 0378-7753/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2006.01.083