How to connect PEM Fuel Cell with Battery, vary hydrogen flow rate, and plot hydrogen consumption vs time in Simulink?

Hello,

I am working on a PEM Fuel Cell + Battery hybrid model in Simulink for a UAV application. I have attached two screenshots of my current model (Fuel Cell stack with inputs and the Battery block).

I have a few specific questions:

1. Connecting Fuel Cell and Battery

• I want to connect the black Fuel Cell stack (with hydrogen, air, and thermal inputs) to the blue Battery and DC system blocks (as shown in my screenshots).
• What is the correct way to connect them together? Should I use a DC-DC converter in between, or can I directly connect them?

1. Varying Hydrogen Flow Rate

• Currently, I am providing constant values for pfuel, qfuel, pair, and qair.
• How can I make qfuel (hydrogen flow rate) time-varying instead of constant? For example, decreasing with time or following a load demand profile.

1. Hydrogen Consumption vs Time Graph

• I want to plot the hydrogen consumption vs time (i.e., how much hydrogen is used and at what time it is consumed).
• Is there any built-in output port in the Fuel Cell stack block that gives hydrogen consumption directly?
• Or should I calculate hydrogen consumption from qfuel flow rate input over simulation time?

1. Parameter Values

• I am not fully sure about the typical values for hydrogen flow rate (qfuel), air flow rate (qair), and pressures (pfuel, pair) for a small PEM Fuel Cell stack (like 35 cells, area 9 cm²).
• Can you please suggest what values are normally used in Simulink models for these inputs?

Any guidance or example models would be really helpful.

Thanks in advance!

Answer 1

[Ankita]

Hi Priyanshu,

Let me address the points serially for clarity:

• Use of DC-DC Converter: Would recommend using a DC-DC converter between the Fuel Cell Stack and Battery/DC bus for safe, efficient, and controllable power transfer
• Making Hydrogen Flow Rate (qfuel) Time-Varying in Simulink: To make the hydrogen flow rate (qfuel) time-varying in Simulink, you have a couple of options: 1. Signal Builder (to draw a custom profile): One can use several Simulink blocks to make qfuel time varying, depending on the type of variation wanted such as the “Step Block” for sudden changes, the “Signal Builder Block” for custom changes, or the “Repeating Sequence Block” for periodic changes. 2. From Workspace (to import a time series from MATLAB): Use the “From Workspace” block to import a time series from MATLAB, allows to provide precise, data-driven profiles for qfuel. Here you may access the official guide: https://www.mathworks.com/help/simulink/slref/fromworkspace.html
• The Fuel Cell Stack block does not provide cumulative hydrogen consumption directly. Integrate the qfuel input with an Integrator block to get total consumption over time. For a list of block ports, features, and usage examples, refer to the official documentation: https://www.mathworks.com/help/sps/ref/fuelcell.html
• Appropriate values for qfuel, qair, pfuel, and pair depend on the specific fuel cell stack specifications and modeling objectives. Here you may access the official guide: https://www.mathworks.com/help/sps/ref/fuelcell.html

Hope this helps!