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Case

Energy storage

Green hydrogen

Hydrogen infrastructure

+2

Multiphysics Simulation of Alkaline Electrolysis (AEL)

30. January 2025

Solution provider

resolvent

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Challenge

The green energy transition requires efficient storage solutions for surplus renewable energy. Alkaline electrolyzers (AEL) convert electricity into hydrogen, which can be stored and used later as fuel or to generate electricity. AEL systems are complex, with interactions between physical processes such as liquid flow, gas generation, and temperature changes. Gas bubbles formed during operation affect local resistance and current distribution, making it difficult to predict cell performance under varying conditions.

 

Solution

A simulation model was created using COMSOL Multiphysics® to account for the main physical processes in AEL systems. The following main modelling assumptions were made:

  • The electrodes, located on each side of the diaphragm (zero-gap cell), are modelled as thin electrodes
  • Fluid properties are evaluated at operating pressure and local temperature, except for density, which is evaluated at operating pressure and temperature (constant)
  • Electrode kinetics and half-cell reaction equilibrium potentials are temperature dependent
  • The diameter of the gas bubbles is constant
  • Only hydrogen and oxygen are present in the gas bubbles (dry gas)
  • Stack level losses are not considered (e.g., shunt currents through the stack manifolds)

The model simulated liquid and gas flow, electrochemical reactions, and temperature-related effects. Time-dependent studies were used to address the changes in electrolyte flow and gas generation over time. Detailed outputs included velocity, pressure, gas volume fractions, reaction rates, and current distributions across the cell.

Result

The simulation provided:

  • Liquid electrolyte velocity, pressure, and volume fraction
  • H2 and O2 gas velocity, pressure, and volume fraction
  • H2 and O2 reaction rates
  • Electric current and potential
  • Electrolyte current and potential

 

These results enabled calculations of flow distribution, gas bubbles behavior and residence time, and prediction of cell voltages. The findings form a foundation for optimizing cell geometry and operating conditions, reducing reliance on physical prototypes and speeding up development.

This simulation approach offers a practical method to improve AEL design and operation, supporting hydrogen production for renewable energy storage.