Control of an afterburner in a diesel fuel cell power unit under variable load Gregor Dolanc a, * , Bo  stjan Pregelj a , Janko Petrov  ci  c a , Remzi Can Samsun b a Department of Systems and Control, Jo zef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia b Electrochemical Process Engineering (IEK-3), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany highlights  A control system for an afterburner of a diesel fuel cell power unit was developed.  It is a part of complete control system of a fuel cell auxiliary power unit.  The goal is stable temperature and steam generation in all operating modes.  A feedforward and feedback control was used for disturbance rejection.  The control system was tested on the auxiliary power unit prototype. article info Article history: Received 11 July 2016 Received in revised form 20 September 2016 Accepted 23 October 2016 Available online 31 October 2016 Keywords: Afterburner Autothermal diesel reforming Fuel cells Auxiliary power unit Process control abstract In this paper, the control system for a catalytic afterburner in a diesel fuel cell auxiliary power unit is presented. The catalytic afterburner is used to burn the non-utilised hydrogen and other possible combustible components of the fuel cell anode off-gas. To increase the energy efficiency of the auxiliary power unit, the thermal energy released in the catalytic afterburner is utilised to generate the steam for the fuel processor. For optimal operation of the power unit in all modes of operation including load change, stable steam generation is required and overall energy balance must be kept within design range. To achieve this, the reaction temperature of the catalytic afterburner must be stable in all modes of operation. Therefore, we propose the afterburner temperature control based on mass and thermal bal- ances. Finally, we demonstrate the control system using the existing prototype of the diesel fuel cell auxiliary power unit. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Fuel cell power units can be used as power units for off-grid stationary or mobile applications. Basically, fuel cells operate on hydrogen, however, hydrogen infrastructure is currently not widely available and hydrogen storage faces technical difficulties. There- fore, in many cases a solution can be found in on-site hydrogen generation from logistic hydrocarbon fuel, such as methanol, nat- ural gas, gasoline, and diesel. Methanol fuel cell power units are already available on the market, e.g. Ref. [1], but methanol is not widely available as well. Fuel cell power units fuelled by liquid petroleum gas (LPG) [2,3] have been developed as auxiliary power units for, e.g., motor homes, as LPG is used in motor homes for cooking and refrigeration. Extensive research and development has been devoted to diesel fuel cell power units since they are very attractive for many stationary and mobile applications due to the wide availability of diesel fuel [4e6]. This type of power unit can replace classic internal combustion engine generators and it has many advantages: much cleaner exhaust with no odour, no soot, no pollutants, lower noise, lower vibrations, and higher energy effi- ciency. The drawback is the relatively complex system structure since the system is typically composed of a fuel processor with reforming and purification reactors, a fuel cell stack, an off-gas burner, a start-up burner, and a set of balance-of-plant- components. Several prototypes have been demonstrated by companies and research institutes; most of them are laboratory prototypes and only some of them are gradually approaching the market, e.g. Ref. [7]. The basic technology (fuel processing technology, reactor * Corresponding author. E-mail address: gregor.dolanc@ijs.si (G. Dolanc). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour http://dx.doi.org/10.1016/j.jpowsour.2016.10.082 0378-7753/© 2016 Elsevier B.V. All rights reserved. Journal of Power Sources 338 (2017) 117e128