Coupled Electrochemical–Thermal Investigation of Passive Cooling Architectures for Space-Integrated Miniaturized PEMFC Power Systems

Thermal management in deep-space environments remains a critical bottleneck for miniaturized energy systems due to the inherent absence of convective heat transfer. This study investigates the thermo-electrochemical coupling of a miniaturized Proton Exchange Membrane Fuel Cell (PEMFC) thermally integrated with a 10 W power electronic Printed Circuit Board (PCB) under high-vacuum conditions. Beyond conventional parametric studies, this work explores the synergistic interaction within six passive thermal control architectures, utilizing paraffin-based Phase Change Materials (PCMs) and high-conductivity graphite Thermal Interface Materials (TIMs). Transient numerical simulations reveal that unmanaged configurations lead to thermal runaway (>128 °C), critically threatening membrane hydration and electrochemical stability. In contrast, the development of a hybridized PCM-TIM architecture—comprising a 5 mm PCM and 10 mm TIM layer coupled with a radiative finned sink—established a high-efficiency thermal shunt. This optimized configuration stabilized the PEMFC at 60 °C and achieved superior temperature homogeneity (<67 °C) across the PCB surface. Furthermore, polarization curve analysis demonstrates that this passive strategy significantly mitigates voltage degradation and concentration losses at high current densities. These findings establish design scaling laws for convection-independent energy subsystems, providing a robust, lightweight, and scalable framework for future microsatellite power architectures in extraterrestrial environments.