How and when to use pybamm.ExplicitTimeIntegral()

[PaulKranefeld]

Hello,
I would like to calculate the integral of a time-dependent quantity U_terminal. It is defined as U_terminal = pybamm.boundary_value(phi_pe, "right") This is basically a post processing step and therefore should not be considered by Pybamm as a constraint during the solving process of my model. I could evaluate the solution object after solving the model like solution["U_terminal"] and calculate the integral afterwards since U_terminal is only time dependent. However, I wonder if there is a way to do the calculation inside the model and get the result directly by calling the solution object like solution["Extraced Energy"] I have found the pybamm.ExplicitTimeIntegral(children, initial_condition) function (Issue 2348) but I do not understand exactly how to use it and if it is the right choice in my case. Basically I want to perform a calculation like E_ex = pybamm.ExplicitTimeIntegral(U_terminal, ?). Thanks in advance for any kind of help.

[valentinsulzer]

In general, the way to do this is to add a variable:

int_U = pybamm.Variable("int_U")
model.rhs[int_U] = U
model.initial_conditions[int_U] = 0

In this case it looks like you're after the energy. You can calculate this by passing the option {"calculate discharge energy": "true"} and then the variable is Discharge energy [W.h].

ExplicitTimeIntegral is still experimental at this stage and for internal use only.

[PaulKranefeld]

Thank you for your reply. Unfortunately, I use a custom model i created myself and so can not access these functions. ("calculate discharge energy": "true") Then I will probably solve it for the time being via a post processing step and wait for this functionality to be implemented.