The rapid dynamic changes of proton exchange membrane water electrolysis (PEMWE) under instantaneous power fluctuations involve the interaction of multiple physical fields

and its transient mechanism is still unclear

which hinders transient control modeling and grid-connection safety and stability analysis. A multi-physics field model considering the transient thermal non-equilibrium characteristics of porous media is proposed to study the second-level thermoelectric coupling dynamic behavior of PEMWE and reveal its transient mechanism under instantaneous power fluctuations. First

considering the risk of thermal runaway caused by local hot spots under PEMWE transient conditions

based on the analysis of its working principle and structural characteristics

a scientific conjecture and a model are proposed

which suggest that the inherent thermal non-equilibrium characteristics of porous media dominate its second-level transient process. Furthermore

considering the local thermal non-equilibrium of porous media

a three-dimensional multi-physics field model of the minimum electrolysis unit is established to simulate its thermoelectric dynamic behavior under instantaneous power fluctuations. Finally

numerical simulation is used to study the influence of battery voltage

inlet flow rate

inlet temperature

and interphase heat transfer coefficient on the transient process of the two-phase temperature distribution in porous media in PEMWE under variable power conditions. It is proved that the second-level dynamic behavior of PEMWE under instantaneous power fluctuations is a thermoelectric coupling process dominated by thermal non-equilibrium heat transfer of membrane electrode

revealing the thermoelectric transient mechanism of PEMWE.