Study on the insulation resistance of proton exchange membrane fuel cell stacks

With the wide application of high-power proton exchange membrane fuel cell, the issue of insulation safety is becoming increasingly important. At present, fuel cell stack often suffers from a significant drop in insulation resistance or even insulation failure during operating process. In this paper, cooling water pathway resistance and gas pathway resistance were identified as the main factors affecting stack insulation resistance through theoretical analysis and experiments. A simulation model capable of predicting the stack insulation resistance was established by considering the structure of the stack. The increase in the conductivity of cooling water and the decrease in the surface resistance after the adsorption of droplet on various component surfaces are the primary reasons for the decrease in the insulation resistance of the stack. It was found that water pathway and gas pathway had a significant influence on the insulation resistance. Through introducing modified parameters representing the effect of geometric structures, a more accurate formula for calculating insulation resistance was proposed. And a reasonable method for the selection of electrical parameters was formed. For example, to meet the safety standards, when the conductivity of the cooling water reaches 5 μS/cm, tube material with a conductivity lower than 7.3 μS/cm should be selected to ensure that water pathway resistance is greater than 1 MΩ, while simultaneously ensuring that gas pathway resistance is greater than 1.526 MΩ.