A modeling framework for predicting the effect of the operating conditions and component sizing on fuel cell degradation and performance for automotive applications

Abstract

In this study, durability and performance prediction were integrated in the sizing process of the FC stack of a fuel cell range-extender (FCREx) vehicle together with the design of a dynamics-limited control strategy. For that purpose, a FCREx vehicle model integrating a FC stack, balance of plant, battery, H2 tank and vehicle body (C-class SUV) validated in previous studies was used. To predict FC stack degradation rate, a novel semi-empirical multi-layered degradation modeling framework for automotive application is proposed and developed. Degradation rates are calculated based on reference degradation rates measured at reference and known conditions (1st layer) and scaled with the electrochemical phenomena (2nd layer) and the operating conditions (3rd layer) through scaling functions based on physical tendencies. Results show how increasing the FC stack power decreases H2 consumption but increases durability, while increasing the dynamic limitations on the control strategy increases both H2 consumption and durability. The isolated effect of sizing implied a decrease in H2 consumption of ∼3% and an increase in FC stack durability of ∼53% when comparing the 40 kW and 100 kW designs. In contrast, the effect of dynamic limitations was significantly perceived in the 40 kW design which implied an increase in H2 consumption close to 8% and an increase in durability of 294% when comparing the infinite dynamics and the highest dynamically restricted cases. Nevertheless, the effect of sizing is neglected under high dynamic limitation and limiting the current density change rate to 0.001 A/cm2s may prevent the control strategy from fulfilling the charge sustaining mode in aggressive driving. Based on these results, a set of recommendations were elaborated for FC stack and FCV manufacturers aiming to apply FCREx architecture to passenger car vehicles.