Description

In this project, we perform the numerical simulation of a High-Temperature Electrolysis using ANSYS Fluent software.

This product is the second chapter of the Electrolysis Training Course.

A fuel cell is an energy conversion device that converts the chemical energy of fuel into electrical energy. Electrolysis is the reverse of a fuel cell. That is, electricity is used to produce fuel (hydrogen) and water.

Electrolyzers, like fuel cells, have two electrical poles (electrodes) called the anode and cathode. These chemical reactions take place in these electrodes. In addition, fuel cells have an electrolyte and a catalyst. The electrolyte layer is used to transport charged particles (ions) between the electrodes, while the catalyst layer increases the speed of reactions in the electrode layers. The water vapor is fed to the electrolyzer, and electrons are also required for the reaction to take place.

High Temperature Electrolysis Methodology

We simulated this project based on the CFD method by ANSYS Fluent software. First, we designed the geometry of the model in 3D using Design Modeler software. The computational domain of the model is related to the interior space of a fuel cell. Then, we meshed the model using ANYS Meshing software. The meshing is unstructured, and 2,393,706 cells are generated. Finally, we performed the simulation process in Fluent software.

For this simulation, we used the fuel cell model in Ansys Fluent software. The fuel cell model is an add-on module in Ansys Fluent software. There are three different fuel cell add-on modules available in the software. We have used the fuel cell and electrolysis model. Here, there are three sub models.

In the electrolysis model setting, we determine the different layers of the fuel cell. These layers include the cathode and anode layers, along with the electrolyte layer. Each of the anode and cathode layers consists of current collectors, gas diffusion layers (electrode layers), catalyst layers, and flow channels.

Since we used the fuel cell model, the species transport model is automatically activated. The species transport model defines the species present in the fuel cell, including H2, O2, and H2O.

Conclusion

After conclusion, we have obtained the contours related to electric potential, protonic potential, current flux density magnitude, transfer current, and mass fraction of H2, O2, and H2O.

The H2, O2, and H2O mass fraction contours show that water vapor enters from the anode side, hydrogen is produced on the anode side, and oxygen is produced on the cathode side. This behavior is exactly according to the functional mechanism of the electrolysis system.

When we use the electrolysis model, some user-defined scalars (UDS) are enabled. Here, we obtained the contours of electric potential (scalar 0), and protonic potential (scalar 1). These contours show that the potential equations of the electrolysis model are solved correctly. Hence, the effect of electrons and protons in electrolyzer layers is understandable. Also, when we use the electrolysis model, several user-defined memories (UDM) are enabled. Here, we obtained contours of current flux density magnitude (user-defined memory 3) and transfer current (user-defined memory 13). These contours show that there is an electric current in the electrolyzer.