Efficient Thermoelectric Conversion System Incorporating Thermocells for Low-Grade Heat Harvesting in Proton Exchange Membrane Fuel Cells

In proton exchange membrane fuel cells (PEMFCs), approximately 50–60% of the energy is lost as low-grade waste heat to the environment, greatly limiting the system efficiency. To address this issue, this work proposes an efficient thermoelectric conversion system (TCS) based on thermocells to effectively exploit the waste heat released from PEMFCs. Multiphysics models of the thermocell are developed to design cell configuration parameters, based on which a hybrid TCS utilizing waste heat (TCS-PEMFC) is developed, and the output characteristics of the TCS-PEMFC are analyzed. Results show that the internal natural convection is closely related to the configuration of thermocells, and with an electrode distance of 3 mm in a horizontal orientation, the negative effects of heat and mass transfer on performance can be minimized, thereby achieving an optimal power output. More remarkably, the TCS, integrating 100 thermocells with an optimized structure, can achieve a voltage of 5.07 V, thereby increasing the output power density of the PEMFCs by 12.51% and boosting the efficiency by 6.83% at a discharge current of 0.4 A/cm2. This study provides theoretical guidance for the optimal design of thermocells and presents a feasible solution for the efficient heat recovery of PEMFCs, contributing to the more effective and comprehensive utilization of hydrogen energy.