Elastocaloric cooler for waste heat recovery from proton exchange membrane fuel cells

Abstract

In addition to generate electricity, proton exchange membrane fuel cells (PEMFCs) also produce a considerable quantity of waste heat, which may affect the cell normal operation if not removed immediately. To remove and harvest the waste heat, a novel combined system that couples an elastocaloric cooler (ECC) to a PEMFC is proposed, where the ECC harnesses the waste heat from the PEMFC for cooling purposes. Including thermodynamic and electrochemical irreversible losses, mathematical expressions for efficiency and power output of the combined system are obtained. The operating current density region of the PEMFC allowing the ECC to work is determined and the optimum operation regions for power output and efficiency of the combined system are specified. Moreover, numerical calculations indicate that the equivalent maximum power density and its corresponding efficiency of the combined system can be, respectively, increased by 163.2 % and 64.2 % in comparison with that of the single PEMFC. Exhaustive parametric studies are further undertaken to reveal how the combined system performance is associated with some key design parameters and operation conditions, such as operating temperature, operating pressure, proton exchange membrane thickness, environment temperature, cross-sectional area ratio, length ratio and thermodynamic losses related parameters. The results may offer some theoretical bases for designing and running such a real combined system and open up a new avenue to harvest waste heat from PEMFCs.