Experimental and numerical analysis of spatial thermal non-uniformity and hotspot formation in an industrial-scale alkaline water electrolyzer stack

The large-scale and high-efficiency development of alkaline water electrolyzers is crucial for the widespread application of green hydrogen. However, their significant thermal inhomogeneity greatly affects the stack performance, durability, and operational safety. The spatial characteristics and underlying mechanisms of such inhomogeneity need to be explored. In this study, the surface temperature distribution of a 10 Nm3 h−1 alkaline water electrolyzer stack is investigated under different load conditions using infrared thermography. Spatially resolved temperature measurements are combined with single-cell and stack-level numerical simulations, as well as post-operation inspection, to elucidate the origins of thermal heterogeneity. The results reveal a stable thermal hotspot located in cells away from the outlet side, whose position remains unchanged with increasing load, indicating a structurally dominated hotspot formation mechanism. While the global maximum temperature occurs at this location, the highest axial average temperature appears in the upper region of the stack, and the poorest axial temperature uniformity consistently occurs in the lower region, highlighting the distinct influence of circumferential position on thermal behavior. Numerical simulations demonstrate that electrolyte flow maldistribution induced by the single-side inlet–outlet configuration leads to reduced flow velocity and heat accumulation in mid-stack cells. Furthermore, sealing ring deformation is experimentally confirmed to locally obstruct manifold flow, generating secondary thermal peaks and aggravating temperature non-uniformity. These findings show that using only the stack outlet temperature as a monitoring or control variable can underestimate internal hotspot temperatures, and underscore the importance of flow-field optimization and mechanical stability in improving the thermal management and reliability of alkaline electrolyzer stacks.