Numerical Modeling of Electrostatics in Alkalyne Electrolyzers with Contact Type Boundary Conditions

Abstract

Alkaline electrolyzers (AEL), splits water molecules into hydrogen and oxygen using an alkaline solution like potassium hydroxide (KOH) as an electrolyte. It has two electrodes, an anode and a cathode, separated by a diaphragm or membrane. Numerical simulation of the physics inside the AEL includes multiphase flow in the electrolyte, and electrostatics in the eletrolyte, the electrodes, and the membrane. The electrostatics involves the well known Poisson equation, but the boundary condition on the electrode surface is rather complex since involves a kind of unilateral restriction. The interface behaves like a unilateral restriction (as a contact-type boundary condiction in mechanics), where the interface does not conduct eleectricity until a certain threshold potential difference is reached. This condition can be solved numerically as a unilateral restriction, with penalization or Augmented Lagrangians.