Presentation

This session completes the high-temperature solid oxide fuel cell SOFC model, presented in the session S61En.

The very simple two parameter model is progressively refined, first by taking into account the equation of polarization of the cell, then introducing a cooling of the stack.

Finally, an exercise shows how to couple the stack to a gas turbine to form a high efficiency cogeneration installation.

In the session S63En, we will see how to change the previously established models to replace the hydrogen by a fuel such as methane.

Second model

We will begin by refining the two-parameter model that has been presented in the session S61En taking into account the equation of polarization of the cell.

This exercise is explained in five steps, all other explanations being presented in the session S61En:

• The first two steps recall how the electrochemical behavior of the cell is modeled
• The following step shows the result obtained in the stack component screen
• The last two steps present the changes induced in the computer implementation of the external class

Explanations about this model are presented in Part V of the book Energy Systems, and all the work files for this example can be downloaded from the links below.

• Second model files (zip, 22 Kb)

Electric model

• Calculation of V and P knowing I and A
• J=I/A

• E, Jd, b, Δ
• parameters

New model

• τ assumed to be proportional to the current density J
• τ = 1.2 J
• New model parameters:
• number of cells N_cell, current intensity I, active surface of a cell A
• P_elec = V_cell I N_cell

SOFC cell component screen

Class code changes

Class code changes

Third model

We will now complete the model by taking into account the cooling of the stack, modeled by a thermocoupler connected to the outlet divider.

Please refer to Volume 3 of the reference manual for a detailed presentation of thermocouplers.

This exercise is explained in four steps, all other explanations being presented in the session S61En:

• The first step shows the new Thermoptim diagram of the component connected to a thermocoupler
• The second step shows the changes of the stack component screen
• The third step shows the thermocoupler screen
• The last step explains how to change the computer implementation of the external class to introduce the thermocoupler

Explanations about this model are presented in Part V of the book Energy Systems, and all the work files for this example can be downloaded from the links below.

• Third model files (zip, 23 Kb)

Cooled fuel cell

SOFC cell component screen

Thermocoupler screen

Study of the external class

• 1) declaration in the constructor

• $2) \; calculations\; made\; by\; method\; updateThermoCoupler()$

Coupling of the stack to a gas turbine

In this exercise we will discuss how the stack we have modeled can be coupled to a gas turbine to form a high efficiency cogeneration plant.

We assume you already know the operation of gas turbines and you know how to model them in Thermoptim. If this is not the case, refer to the session S20En and the following.

This exercise is explained very briefly in two steps:

• The first step shows the Thermoptim diagram of the entire plant, and explains the role of the different components
• The second shows the simulation results obtained for the settings chosen

From this example, you can conduct many activities, such as studying the influence of inlet parameters on the overall performance, or construct the diagram of a combined cycle plant valuing all available thermal power.

All the working files for this example can be downloaded from the link below.

• Exercise files (zip, 25 Kb)

Diagram of the plant

Synoptic view of the plant

Summary

In this session, we saw how could be refined the high temperature solid oxide fuel cell model presented in the session S61En.

The model we have developed allows the inclusion of the equation of polarization of the cell and the introduction of a cooling of the stack. An exercise has shown how to couple the stack to a gas turbine to form a high efficiency cogeneration plant.

In the session S63En, we will see how this model can be modified to replace the hydrogen by a fuel such as methane.

We will use this new development to give access to some of the parameters introduced in this session, such as those of the electrochemical model, so that our model can be used as broadly as possible