Dynamic Programming for Thermal Management of Automotive Fuel Cell Systems: Investigating Hydrogen Saving Potential

Thermal management strategies implemented on-board fuel cell electrified vehicles (FCEVs) are currently based on heuristic reactive approaches. In this framework, developing predictive thermal management approaches that anticipate the travel needs of FCEV users could lead to improved hydrogen savings. However, the theoretical hydrogen saving achievable by predictive thermal management needs assessment first to quantify the technical and economical viability of the technology proposal. This paper lays the foundations in this domain by analyzing the a priori optimal thermal management of a fuel cell system in an FCEV. Initially, an electrochemical and thermal modeling technique for the fuel cell system is described. A reactive rule-based approach is then selected as the baseline controller for the coolant rate and the instantaneous radiator fan state of the FCEV. Then, the optimal control problem formulation for the thermal management of fuel cell systems in FCEVs is discussed and solved using a dynamic programming (DP) based optimization approach that makes use of a priori information about the entire driving mission. The fuel cell system is evaluated while the FCEV performs one to ten repetitions of the Worldwide Harmonized Light Vehicle Test Cycle (WLTC) at different ambient temperatures ranging from -20 degrees C to 40 degrees C. When compared to the baseline reactive control technique, the offline optimal benchmark can save up to 10.2% hydrogen. Results presented in this paper demonstrate the potential of hydrogen saving achievable by improving the thermal management of automotive fuel cell systems. Moreover, they may be used to develop and benchmark real-time capable predictive thermal management strategies for fuel cell systems in FCEVs.