Integration of phosphoric acid fuel cells and humidification-dehumidification units for simultaneously electricity and freshwater production

Despite extensive studies on phosphoric acid fuel cells (PAFCs) and humidification-dehumidification (HDH) units individually, their integrated operation remains unexplored. This study proposes and evaluates a novel hybrid system integrating a PAFC with a HDH desalination unit to simultaneously generate electricity and produce freshwater. A steady-state model, incorporating electrochemical, thermodynamic, and mass-transfer principles, is established and validated against independent experimental data for each subsystem. At the optimal operating temperature of 457 K, the hybrid system achieves a peak power density of 5532.35 W·m⁻², energy efficiency of 48.20 %, and exergy efficiency of 51.21 %, representing respective gains of 9.81 %, 9.89 %, and 14.08 % over a standalone PAFC. The HDH unit attains a maximum gain output ratio of 11.13 at 446 K, demonstrating substantial freshwater production capability from PAFC waste heat. Parametric and local sensitivity analyses reveal that electrolyte membrane thickness and operating current density are the most influential variables, followed by humidifier area and exchange current density. These findings underscore the potential of PAFC/HDH integration as a sustainable solution for decentralized power and water supply, particularly in energy- and water-scarce regions, and provide guidance for performance-oriented design and operational optimization.