Modelling and Validation of Water Hydration of PEM Fuel Cell Membrane in Dynamic Operations

摘要

Fuel cells convert chemical energy of hydrogen and oxygen directly in to electricity. High efficiency and zero emission have made them a prime candidate for powering the next generation of electric vehicles. PEM fuel cells require good hydration in order to deliver high performance and ensure long life operation. Water is essential for membrane proton conductivity which increases by nearly six orders of magnitude from dry to fully hydrated. Adequate water management in PEM fuel cell is crucial in order to avoid an imbalance between water production and water removal from the fuel cell. In the present study, a novel mathematical zero-dimensional model has been formulated for the water mass balance and hydration of a polymer electrolyte membrane. This model incorporates all the essential fundamental physical and electrochemical processes occurring in the membrane electrolyte and considers the water adsorption/desorption phenomena in the membrane. The effect of diffusivity model, surface roughness and water content driving force is considered. The model is validated against experimental data. Many studies have considered fuel cell membrane in equilibrium condition disregarding non-Ficknian behavior of the cell membrane. The present model consider absorption/desorption mechanism typical of dynamic process and for this reason it becomes useful when studying PEM fuel cell system in dynamic conditions.