Resistance in PEM electrolyzer block

Hi all,

I've been running simulations in Simulink in orden to calculate hydrogen production in different scenarios.

For that I've used the Electrolyzer block available in Simscape. My simulations all compiled and worked correctly, however, there is one parameter of the electrolyzer block that I don't quite understand. That is tha so called External Resistance "R", which is scarcely described on Mathworks page as:

where v is the voltage and RT is the total resistance. The total resistance, RT, is defined as it follows:

1/RT=1/Rel+1/R,

where:

• R is the external resistance.
• Rel=ρ(pH)xA. This value is a resistive term obtained from the cross-sectional transport area, A, the distance anode-cathode, x, and the electrical resistivity of the solution, ρ(pH).

I do understand what "Rel" is, but not "R"

what does it represent? and why is it a paralel resistance?

I would be very thankful if someone could resolve this to me.

Answer 1

[Swaraj]

The external resistance "R" in the setting of Simscape's Electrolyzer block denotes an additional resistance that can be connected in parallel with the electrolyzer to simulate the effects of an external load.

Due to the physical and chemical characteristics of the materials used, the electrolyzer within an electrolysis cell has a certain internal resistance. When an external load is attached to the electrolyzer, the combined effect of the internal and external resistances determines the current flowing through the electrolyzer. The interior resistance (Rel) and the external resistance (R) are added together to form the total resistance (RT).

The external resistance R can be adjusted in the Simscape model to simulate the effect of different loads on the electrolyzer. When R is increased, the total resistance RT decreases, which leads to an increase in the current passing through the electrolyzer. Conversely, when R is decreased, RT increases, which leads to a decrease in the current passing through the electrolyzer.

In summary, the external resistance "R" in the Electrolyzer block in Simscape represents an additional resistance that can be added in parallel with the electrolyzer to simulate the effects of an external load.

1/RT=1/Rel+1/R.

The above equation is used for the parallel addition of the Rel and R.