Discussion Forum

In the application gallery of Comsol, there is one example of a 2D model of all-vanadium redox flow battery (https://www.comsol.com/model/vanadium-redox-flow-battery-14153). In this example, in both sides (anode and cathode) we have porous electrodes and hence the porous electrode within tertiary current distribution has been used. Now, I want to change this for a system that only has a porous electrode in one side. Thus, in this model, I disabled the porous electrode module in the negative half-cell and instead use the surface electrode+electrolyte to model the negative half-cell with the electrochemical reaction occuring on the surface of the electrode. However, when I make this change, I can no longer get any results (error says Undefined value found in the equation residual vector), which probably means there is a problem in the boundary conditions. I could not find anything wrong with the bcs. Does anyone know what could cause this problem? changing the porous electrode to surface electrode should be straightforward and I cannot see the problem.