SOFC (Solid Oxide Fuel Cell) CFD Simulation, ANSYS Fluent Training

Description

Solid Oxide Fuel Cell (SOFC), CFD Simulation, ANSYS Fluent Training

Description

This project is about a numerical simulation of a solid oxide fuel cell (SOFC) using ANSYS Fluent software.

A fuel cell is a device that converts fuel energy into electrical energy. There are many types of fuel cells in the industry, such as SOFC, PEMFC, etc. In this project, we model a solid oxide fuel cell. This fuel cell can work at very high temperatures.

The solid oxide fuel cell consists of two sections, a cathode and an anode. These sections are connected by the electrolyte layer in the central part of the fuel cell. There are two layers of electrode and collector in each cathode and anode section.

The collectors are made of solid material and perform conducting electric current. Inside these current collectors, there is a gas channel. The oxygen (or air) from the gas channel of the cathode collector and the hydrogen (or fuel) from the gas channel of the anode collector enters the fuel cell.

Electrode layers are porous and ion conductive. The oxygen is converted into positive ions by combining with free electrons in the cathode electrode. On the other hand, hydrogen combines with oxygen ions and free electrons to form water in the anode electrode.

The middle electrolytic layer is ceramic and conducts positive oxygen ions. These released electrons create an electric current through the collectors and the circuit connected to the cell.

We design the 3D geometry of the fuel cell using Design Modeler software. The computational domain of this model consists of several layers. We define Collectors as solid layers and other layers as fluid layers. Then we mesh this model using ANSYS Meshing software. The mesh type is structured, and the number of cells is 930,240.

SOFC Methodology

We use the “SOFC with unresolved electrolyte” in this project. We load this fuel cell model as an add-on module in ANSYS Fluent software.

The naming of this module has two reasons. First, positive oxygen ions pass through the solid electrolyte layer. Secondly, according to this fuel cell model, the electrolyte layer is not included in the computational domain. We define this layer as an interface (“wall” and “wall shadow”).

When we use this model, a series of source and sink terms are automatically applied, and special materials are defined for each of the layers of the fuel cell.

In this modeling, the electric current in the fuel cell is equal to 10 Amp. For the two terminals of the fuel cell, we define the anode tap as zero voltage (ground voltage) and the cathode tap as the cell’s electric current.

The electrode layers are made of porous materials with a porosity of 0.5. Also, the tortuosity (the ratio of the path between two points to the distance between those two points) of these layers is equal to 2. Also, in the collector and electrode layers, the conductivity (against resistivity) is equal to 0.1 S/m.

As mentioned, hydrogen flow from the anode side and oxygen flow from the cathode side enter the fuel cell and finally, water is formed. So there are several gas species, and several electrochemical reactions take place. Therefore, we use the species transport model to define three volumetric species: hydrogen, oxygen and water.

SOFC Conclusion

After the calculations, we obtain two-dimensional contours related to the concentration or mass fraction of oxygen, hydrogen and water. These contours correctly confirm the process of electrochemical reactions in the fuel cell.

The results show that oxygen enters from the cathode side and hydrogen enters from the anode side. Initially, there was no water inside the fuel cell, but the results show that water has formed on the anode side of the fuel cell. This means the electrochemical reaction between oxygen, hydrogen and electrons has happened in the fuel cell.

Also, we obtain the contours of electric potential and electric current inside the fuel cell. These contours correctly show the process of generating electric current. There is a potential difference between the cathode and the anode sides, and an electric current is generated inside the fuel cell. So we can say that the solid oxide fuel cell system works correctly.