(457f) High-Fidelity Modelling and Detailed Design of PEM Fuel Cell Stacks

The optimal design of PEM fuel cell stacks is a particularly challenging task. On one hand, it is important to model in detail the numerous complex coupled phenomena that take place within each layer, including both the fluid mechanics in the fuel and air channels, and the electrochemical reactions and the multicomponent mass and heat diffusion within the electrolyte membrane. On the other hand, it is necessary to represent with reasonable accuracy stacks which involve tens or even hundreds of such layers. Moreover, determining optimal designs requires the examination of a large number of alternatives. Overall, the combination of these three factors leads to a formidable computational problem.

We present a hybrid modelling technique that combines Computational Fluid Dynamic (CFD) models of flow channel hydrodynamics with first-principles physical and chemistry models that have been validated against laboratory data. This fully-coupled approach has numerous advantages over either ?pure? CFD or ?pure? first-principles models; examples include the ability to predict very accurately the temperature profiles and current density across the anode-electrolyte?cathode assembly.

In principle, the above hybrid approach is applicable both to individual cell assemblies and to entire stacks. However, the computational load becomes extremely high for stacks involving large numbers of layers. This is a problem that also occurs with ?pure? CFD models of the stack. The problem is, to some extent, alleviated by the availability of highly parallelised CFD codes. However, the simulation of stacks involving more than a few tens of layers remains problematic, and this is even more so when these simulations need to be repeated many times for the purposes of stack optimisation.

In view of the above, this paper presents novel and powerful hybrid modelling technology that enables multiple parallel processing of CFD and first-principles models in the context of large-scale fuel cells stacks involving many individual cell assemblies. The approach implements sophisticated model aggregation techniques that allow rapid computation of multi-layered stacks in short timescales without significant compromise on predictive accuracy.

The approach has been employed for the final design of PEM fuel cell stacks in order to optimise the detailed design of channels and manifolds while ensuring uniform temperature and pressure distribution over the stack.