Setting thermal parameters

[ahsadeghi]

Hello,
It is said in the examples that the heat generation is due to the three terms and I can see the three terms in base_thermal. But I cannot figure out how the Arrhenius equations are coded in this module, and how can I change the Arrhenius parameters such as activation energy and pre-exponential factor. I wonder if you could please explain about this.

Regards,
Hosein

[ben-kenney]

You can take a look through the parameter sets and you should see the dU/dT curves for the positive/negative electrodes. For example in Mohtat2020 you'll find the entropy change for graphite and NMC.

The activation energies appear to be baked into functions, like this for NMC diffusivity:

def NMC_diffusivity_PeymanMPM(sto, T):
    D_ref = 8 * 10 ** (-15)
    E_D_s = 18550
    arrhenius = pybamm.exp(E_D_s / pybamm.constants.R * (1 / 298.15 - 1 / T))
    return D_ref * arrhenius

It seems to be possible to write your own function where you should be able to specify the activation energy...something I'll also need to do but haven't gotten there yet!

[ahsadeghi]

Dear @brosaplanella
Regarding this question, I need to (for instance) modify E_r and E_D_s in ORegan2022.py. I am not sure if I can do it through the input file or do I need to compile the code with the modified values. I wonder if you could please explain this. Thank you.

Hosein

[brosaplanella]

You can just copy ORegan2022.py into a new file locally, edit the parameters, and then in your main code import the get_parameter_values function from that file.

[ben-kenney]

I'm interested in a variation of this: The answer above will create a new function that has a hard coded activation energy but what if we needed to treat the activation energy as a fitting parameter?

Any tips on how to modify the function above NMC_diffusivity_PeymanMPM(sto, T) so that the activation energy can be easily updated for a fitting process?

[brosaplanella]

Just define it as a parameter:

E_D_s = pybamm.Parameter("Activation energy of positive electrode diffusivity [J.mol-1]")

Then you can set the value by adding it to the dictionary with all the other parameter values.