Synergistic enhancement of power density and energy efficiency in phosphoric acid fuel cells via near-field thermoradiative cell integration

Phosphoric acid fuel cells (PAFCs) suffer from significant waste heat generation during operation, diminishing energy conversion efficiency and exacerbating global warming. To address this challenge, an innovative hybrid system integrating a near-field thermoradiative cell (NFTRC) with a PAFC is proposed to effectively enhance fuel utilization and recover waste heat, thereby providing a new technical pathway for the efficient utilization of renewable energy and low-carbon transition. Through a thermodynamically rigorous framework, the hybrid system’s performance is analytically modeled by deriving its output power density and energy conversion efficiency, explicitly accounting for irreversible losses inherent to both subsystems. The results demonstrate that the PAFC–NFTRC hybrid system achieves a 17.2% enhancement in maximum power density and a 6.4% improvement in energy conversion efficiency compared to a standalone PAFC. Parametric analyses reveal that increasing the PAFC operating temperature or exchange current density significantly enhances system performance, while an enlarged NFTRC vacuum gap or higher electrolyte molar fraction negatively impacts the output performance. Comparative evaluations with existing PAFC-based hybrid systems highlight the superior efficacy of NFTRCs in waste heat recovery, outperforming conventional heat-to-electricity conversion techniques. This study establishes a theoretical framework for optimizing PAFC–NFTRC system design and operational parameters, offering valuable insights into the development of high-efficiency, low-emission energy conversion technologies.