The analysis of cross-level transfer characteristic of hydrogen and heat of thermal coupling system: Framework design and case study

Considering the complementary heat demand, the thermal coupling system (TCS) of metal hydride (MH) tank and fuel cell (FC) has been proposed to decrease the system volume and increase the energy efficiency. However, the cross-level transfer characteristic of hydrogen and heat in TCS brings challenges to the system analysis, since the multi-dimensional model can hardly be used due to the heavy computational cost, while the lumped model (LM) provides rough description of TCS due to the over-simplified heat transfer assumption. In this paper, a three-step framework for TCS analysis is proposed, including thermal management optimization, reduced model establishment and system parameter analysis. A LaNi₅-based MH tank thermally coupled with 10 kW proton exchange membrane fuel cell (PEMFC) is studied herein. The results show that the hydrogen supply duration can be increased by 17.4 %, with the specific hydrogen storage capacity of 0.8625 and efficiency of hydrogen-to-power/heat of 56 % respectively after optimization. Then the reduced model of MH tank with model predict controller (MPC) are developed and verified with better dynamic performance compared with proportional-integral-derivative (PID) controller. Finally, the effect of heat transfer in MH tank on system performance is captured by the proposed framework with reasonable evaluation of system efficiency and operation duration compared with LM, providing theoretical guidance for the design of efficient system.