1.1 Introduction

The Fuel Cell and Electrolysis module (sometimes referred to as the Resolved Electrolyte module) is provided as an addon module with the standard ANSYS FLUENT licensed software. A special license is required to use this module.

A fuel cell is an energy conversion device that converts the chemical energy of fuel into electrical energy. With the Fuel Cell and Electrolysis Model, both the triple-phase boundary (TPB), also known as the catalyst layer, and the ionic conducting electrolyte (also known as the membrane in PEMFC terminology) are included in the computational domain. The Fuel Cell and Electrolysis module allows you to model PEMFC, SOFC, and high-temperature electrolysis.

To determine the physical domains that are included in the Fuel Cell and Electrolysis module, a schematic of a polymer electrolyte membrane fuel cell (PEMFC) is shown in Figure  1.1.1.

Figure 1.1.1: Schematic of a PEM Fuel Cell

Hydrogen flows into the fuel cell on the anode side. It diffuses through the porous gas diffusion layers and comes in contact with the catalyst layer. Here it forms hydrogen ions and electrons. The hydrogen ions diffuse through the polymer electrolyte membrane at the center, the electrons flow through the gas diffusion layer to the current collectors and into the electric load attached. Electrons enter the cathode side through the current collectors and the gas diffusion layer. At the catalyst layer on the cathode side, the electrons, the hydrogen ions, and the oxygen combine to form water.

In the Fuel Cell and Electrolysis Model in ANSYS FLUENT, two electric potential fields are solved. One potential is solved in the electrolyte and the TPB catalyst layer. The other is solved in the TPB catalyst layer, the porous electrode, and the current collectors. The rate of electrochemical reactions are computed in the TPB layers at both the anode and the cathode. Based on the cell voltage that you prescribe, the current density value is computed. Alternatively, a cell voltage can be computed based on a prescribed average current density.