Ohmic Losses and Temperature Distribution in a Passive PEM Fuel Cell
Application ID: 8553
In small PEM fuel cell systems (in the sub-100 W range) no active devices for cooling or air transport are normally used. This is due to the desire to minimize parasitic power losses from pumps and fans, and to reduce the system complexity, size, and cost. The reactants at the cathode are therefore transported by passive convection/diffusion. Also the heat dissipation occurs by passive transport mechanisms to the surrounding environment.
When designing the air side of a passive fuel cell the goal is to ensure an even current density and heat profile over the cell for various surrounding temperatures and current loads.
The holes in the cathode cover plate should typically be large in order to provide good reactant transport to the electrode, but the hole-to-solid material ratio may not be too large since the structural rigidity and electron conductivity of the plate also have to be maintained. Large air holes will also cause high local ohmic losses in the GDL. This example models the current density and heat profile over a passive PEM fuel cell.