PEM Electrolysis, CFD Simulation, ANSYS Fluent

Description

Description

In this project, we perform the numerical simulation of the PEM Electrolysis using ANSYS Fluent software.

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

Note that 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. It means power (electricity) is consumed to produce fuel (hydrogen).

Similar to fuel cells, electrolyzers consist of two main sides called anode and cathode, which are connected by an electrolyte membrane layer. On each side of the anode or cathode, there is a current collector, a gas diffusion layer (porous electrode), and a catalyst layer.

Electrochemical reactions take place in catalyst layers. As a result of these reactions, water is consumed and oxygen and hydrogen are produced.

There are several types of electrolysis process. In this CFD simulation, we investigated a Polymer Electrolyte Membrane (PEM) electrolyzer.

In the PEM electrolysis, water is supplied on the anode side; as a result, oxygen is produced on the anode side and hydrogen is produced on the cathode side.

We performed the simulation process in ANSYS Fluent software.

First, we modeled the geometry in 3D using Design Modeler software. The computational domain is related to the interior space of an electrolyzer.

Then, we meshed the model using ANYS Meshing software. The meshing is structured, and 428,800 cells are generated.

Electrolysis Methodology

We simulated this project based on the CFD method by ANSYS Fluent software.

In this CFD simulation, we used the potential/electrochemistry model to define the potential equation. Then, we used the electrolysis sub-model to define the electrolysis process. In the electrolysis sub-model, we selected the PEM electrolysis type.

In the electrolysis model setting, we determine the different layers of the electrolyzer. The electrolyzer consists of the cathode, anode, and electrolyte layers. Each of the anode and cathode sides consists of current collectors, gas diffusion layers (porous electrode layers), catalyst layers, and gas flow channels. Since we used the electrolysis model, the species model and Multiphase model are automatically activated.

First, we used the mixture multiphase model to define a two-phase flow including water and gaseous species. Then, we used the species transport model to define the species present in the electrochemical reactions, including H2, O2, and H2O.

Conclusion

After conclusion, we have obtained the contours related to current flux density magnitude, transfer current, volume fraction of water, and mass fraction of H2 and O2. The contours of water volume fraction and H2 and O2 mass fraction show that water enters from the anode side, oxygen is produced on the anode side, and hydrogen is produced on the cathode side. This behavior is exactly according to the operating mechanism of the PEM electrolysis system. Therefore, we conclude that we performed the electrolyzer simulation correctly.