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An absorption chiller model for tri-generation (combined cooling, heating, and power) is developed and incorporated with the high temperature- (HT-) proton exchange membrane fuel cell (PEMFC) system model that was developed in our previous study. We employ a commercially available flow simulator, Aspen HYSYS, for solving the energy and mass balances of various system components, including an HT-PEMFC stack that is based on a phosphoric acid-doped PBI membrane, natural gas-fueled reformer, LiBr-H2O absorption chiller, balance of plant (BOP) components, and heat exchangers. Since the system’s operating strategy for tri-generation must be changed, depending on cooling or heating loads, a major focus of this study is to analyze system performance and efficiency under different requirements of electricity generation, cooling, and heating conditions. The system simulation results revealed that high-current fuel-cell operation is essential in raising the cooling capacity, but the overall system efficiency is slightly reduced as a result. Using a lower fuel-air ratio for the burner in the reforming module is one alternative that can minimize the reduction in the overall system efficiency under high-current fuel-cell operation and large cooling-capacity modes.

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This paper reports novel cathode flow-field designs for passive typed air-cooled polymer electrolyte membrane fuel cells (PEMFCs) to help alleviate electrolyte dehydration and performance degradation issues under excess dry air supply conditions. The proposed flow-field designs include 7 three-dimensional (3-D) patterned designs in addition to a parallel channel configuration equipped with rectangular baffles to control the airflow for more efficient heat removal. The designs were evaluated numerically using 3-D, two-phase PEMFC simulations. Compared to a typical parallel flow channel configuration, the proposed flow-field designs show better heat removal and water retention capability. The single-cell voltage was improved around 13–75 mV at the operating current density of 0.5 A/cm2, an increase in pressure from 0.9–47-fold increase was required because of the more complex flow-field configurations. This work presents a comprehensive understanding of air-cooled PEMFC operating characteristics under excessive dry air supply conditions and a new design strategy for cathode flow fields.