2.9 Solution Guidelines for the Fuel Cell and Electrolysis Model

For potentiostatic boundary conditions, after initialization, steady state solutions are calculated easily for cell voltages close to the open-circuit voltage. The same can be said for galvanostatic boundary conditions and low electric current. By lowering the cell voltage or by raising the average electric current, you can calculate subsequent stationary solutions.

In the event of convergence problems, it is recommended to change the multigrid cycle to F-cycle with BCGSTAB (bi-conjugate gradient stabilized method) selected as the stabilization method for the species and the two potential equations. For the species and the user-defined scalar equations, it may be necessary to reduce the termination (criteria) of the multigrid-cycles to $1 \times 10^{-3}$. For stack simulations, the termination criterion may be reduced to $\times 10^{-7}$ for the two potential equations.

Also, it may be useful to turn off Joule Heating and Reaction Heating in the Fuel Cell and Electrolysis Models dialog (in the Model tab) for the first few (approximately 5-10) iterations after initializations. This allows the two electric potentials to adjust from their initial values to more physical values, avoiding the possibility of extreme electrochemical reactions and electric currents that would in turn adversely impact the solution.