A technically feasible strategy using liquid-state thermocells to efficiently recover the waste heat released from proton exchange membrane fuel cells

Abstract

Proton exchange membrane fuel cells (PEMFCs) generate a large amount of exhaust heat during operation, leading to environmental pollution and the greenhouse effect. To recover the low-grade exhaust heat produced by PEMFCs, a technically feasible approach is proposed by integrating liquid-state thermocells (LTCs) with PEMFCs for the cogeneration of electric power and efficient waste heat recovery. Considering the three overpotential losses in the PEMFC and the irreversible heat losses in the LTC, a comprehensive mathematical model of a PEMFC-LTC hybrid system is developed to explore the energetic performance characteristics and optimal device design. The results show that the hybrid system’s maximum power density and corresponding conversion efficiency are 0.3007 W cm−2 and 24.59%, which is increased by 6.22% and 19.41% compared to a single PEMFC, respectively. Furthermore, raising the PEMFC temperature, optimizing the length of the individual LTC cell, reducing the heat sink temperature, and lowering the thermal convection coefficient can significantly improve the optimal output performance of the hybrid system. Finally, the optimal performance comparisons between the PEMFC-based cogeneration systems reveal that LTCs can more efficiently recycle the waste heat released from the PEMFC than other previously reported devices. This work offers crucial theoretical guidance for the optimal design and parametric analysis of PEMFC-LTC hybrid systems, thus paving the way for developing high-performance energy cascade utilization systems based on PEMFCs.