Dynamic electro-thermal-gas multi-physics attribution and optimization of PEMFC–LaNi5 coupled system for ship auxiliary power units

For typical ship auxiliary power unit (APU) operating conditions, this paper develops an integrated dynamic model of a PEMFC–LaNi5 metal hydride (MH) hydrogen storage bed, buffer tank, and cooling seawater circulation loop. The model is used to reveal multi-physics coupling (electric-heat-gas) under step-load transients. Three performance indicators are defined—electrical efficiency (ηel), heat matching degree (HMD), and hydrogen inventory support rate (S)—and a multi-physics channel response contribution (RC) method is proposed to quantitatively attribute the performance of individual components and the overall system to the electric, heat, and gas channels. Simulation results show good load-following capability and stable hydrogen supply under multi-step load changes. ηel is primarily governed by the electric channel, HMD is dominated by the heat and gas channels, and S is most sensitive to the electric and gas channels. The MH bed temperature remains within a suitable medium-temperature dehydrogenation range. The buffer tank and pore-gas inventory mainly provide peak shaving and valley filling near load transitions, mitigating hydrogen starvation and excessive pressure drop. Based on parameter sensitivity analysis and multi-objective optimization, a compromise operating condition within the studied range is obtained: anode stoichiometry πH2 = 1.15, cooling water flow rate mcw = 0.27 kg/s, MH coil heat transfer coefficient UAMH = 1000 W/K, buffer tank volume VBT = 0.2 m3, and cooling water inlet temperature Tcw,in = 300.65 K. This solution maintains ηel,int at 53.3 %, increases HMDint to 38.8 %, and reduces Sint to 5.5 %, providing a quantitative basis for collaborative design optimization and parameter tuning of PEMFC–LaNi5 coupled systems for ship APU applications.