Modeling and optimization of diesel-powered solid oxide fuel cell system for auxiliary power unit

Abstract

Heavy-duty trucks, which are mainly used for freight transport, require a significant amount of non-propulsion power due to their long-time/long-distance operation. The supply of the non-propulsion power is highly dependent on inefficient and non-eco-friendly idling technology. As interest in environmental issues rapidly increases, diesel-powered solid oxide fuel cell system is attracting much attention as an alternative technology to replace the idling of heavy-duty trucks. The system has an Auto-Thermal Reforming (ATR) reactor and a Solid Oxide Fuel Cell (SOFC) as main components. Of them, in the case of the ATR reactor which converts diesel as the main fuel of heavy-duty trucks into a reformed gas suitable for fuel cell applications, the kinetic model for the reaction is required in order to optimize the reactor dimensions or conduct a control study. However, commercial diesel has very diverse components and can have numerous reaction pathways, making it very difficult to construct the kinetic model. Therefore, in this study, in order to establish an appropriate kinetic model for the diesel ATR reaction, an experiment was performed in a microreactor and the composition data of the reactor outlet according to the change of major operating variables were collected. Then, based on the collected data, optimal kinetic models for each model were derived through parameter estimation for the kinetic models corresponding to various combinations of reaction equations that can be considered in diesel ATR reaction. Furthermore, by comparing the performance of each model, the combination of reaction equations that can best simulate the diesel ATR reaction was discussed. In addition to the ATR reactor and the SOFC, the system includes a post combustion combustor, a condenser and a heat exchanger as essential components. In addition, the system forms a closed loop by circulating electrochemically generated water for sustainable operation without external water supply. Accordingly, the components are closely connected to each other. Therefore, in order to construct system efficiently, it is necessary to view the system in its entirety including all the components. Thus, in this study, a rigorous overall system model was built by considering all major components. The system may consider anode recycling or cathode recycling for more efficient operation. In this study, based on the constructed overall system model, the effects of anode recycling and cathode recycling on the performance of SOFC was investigated by solving an optimization problem that has the efficiency of the overall system as the objective function.