Added support for time series temperature in an experiment step

src/pybamm/experiment/experiment.py

@@ -63,6 +63,8 @@ def __init__(
 
         steps_unprocessed = [cond for cycle in cycles for cond in cycle]
 
+        self.temperature_interpolant = None
+
         # Convert strings to pybamm.step.BaseStep objects
         # We only do this once per unique step, to avoid unnecessary conversions
         # Assign experiment period and temperature if not specified in step
@@ -75,6 +77,10 @@ def __init__(
 
         self.steps = [processed_steps[repr(step)] for step in steps_unprocessed]
         self.steps = self._set_next_start_time(self.steps)
+        for step in self.steps:
+            if getattr(step, "has_time_series_temperature", False):
+                self.temperature_interpolant = step.temperature
+                break
 
         # Save the processed unique steps and the processed operating conditions
         # for every step

src/pybamm/experiment/step/base_step.py

@@ -79,7 +79,6 @@
                 f"Invalid direction: {direction}. Must be one of {potential_directions}"
             )
         self.input_duration = duration
-        self.input_duration = duration
         self.input_value = value
         self.skip_ok = skip_ok
         # Check if drive cycle
@@ -158,7 +157,6 @@
         ):
             direction = self.value_based_charge_or_discharge()
         self.direction = direction
-
         self.repr_args, self.hash_args = self.record_tags(
             value,
             duration,
@@ -184,8 +182,12 @@
             term = _read_termination(term)
             self.termination.append(term)
 
-        self.temperature = _convert_temperature_to_kelvin(temperature)
-
+        self.temperature = _convert_temperature_to_kelvin(
+            temperature
+        )  # change name of the function
+        self.has_time_series_temperature = isinstance(
+            self.temperature, pybamm.Interpolant
+        )
         if tags is None:
             tags = []
         elif isinstance(tags, str):
@@ -424,9 +426,13 @@
             hash_args += f", termination={termination}"
         if period:
             repr_args += f", period={period}"
-        if temperature:
-            repr_args += f", temperature={temperature}"
-            hash_args += f", temperature={temperature}"
+        if temperature is not None:
+            if isinstance(temperature, np.ndarray):
+                repr_args += ", temperature=<time-series>"
+                hash_args += ", temperature=<time-series>"
+            else:
+                repr_args += f", temperature={temperature}"
+                hash_args += f", temperature={temperature}"
         if tags:
             repr_args += f", tags={tags}"
         if start_time:
@@ -535,7 +541,28 @@
 
 
 def _convert_temperature_to_kelvin(temperature_and_units):
-    """Convert a temperature in Celsius or Kelvin to a temperature in Kelvin"""
+    """
+    If the input is a 2D numpy array (time series), return an Interpolant.
+    Otherwise Convert a temperature in Celsius or Kelvin to a temperature in Kelvin
+    """
+
+    # Check if the temperature input is a time-series array
+    if isinstance(temperature_and_units, np.ndarray):
+        if temperature_and_units.ndim == 2 and temperature_and_units.shape[1] == 2:
+            # Assume first column is time (s) and second column is temperature (K)
+            times = temperature_and_units[:, 0]
+            temps = temperature_and_units[:, 1]
+            # Create an interpolant function parameter that depends on time
+            return pybamm.Interpolant(times, temps, pybamm.t, interpolator="linear")
+        else:
+            raise ValueError(
+                "Temperature time-series must be a 2D array with two columns (time, temperature)."
+            )
+
+    # If it's already an Interpolant, do nothing further.
+    if isinstance(temperature_and_units, pybamm.Interpolant):
+        return temperature_and_units
+
     # If the temperature is a number, assume it is in Kelvin
     if isinstance(temperature_and_units, (int, float)) or temperature_and_units is None:
         return temperature_and_units

src/pybamm/experiment/step/steps.py

@@ -176,7 +176,10 @@ class Voltage(BaseStepImplicit):
     """
 
     def get_parameter_values(self, variables):
-        return {"Voltage function [V]": self.value}
+        params = {"Voltage function [V]": self.value}
+        if self.temperature is not None:
+            params["Ambient temperature [K]"] = self.temperature
+        return params
 
     def get_submodel(self, model):
         return pybamm.external_circuit.VoltageFunctionControl(

src/pybamm/simulation.py

@@ -318,6 +318,15 @@
         if initial_soc is not None:
             self.set_initial_soc(initial_soc, inputs=inputs)
 
+        if (
+            getattr(self, "experiment", None)
+            and hasattr(self.experiment, "temperature_interpolant")
+            and self.experiment.temperature_interpolant is not None
+        ):
+            self.parameter_values.update(
+                {"Ambient temperature [K]": self.experiment.temperature_interpolant}
+            )
+
         if self._built_model:
             return
         elif self._model.is_discretised:
@@ -444,6 +453,14 @@
             See :meth:`pybamm.BaseSolver.solve`.
         """
         pybamm.telemetry.capture("simulation-solved")
+        if (
+            getattr(self, "experiment", None)
+            and hasattr(self.experiment, "temperature_interpolant")
+            and self.experiment.temperature_interpolant is not None
+        ):
+            self.parameter_values.update(
+                {"Ambient temperature [K]": self.experiment.temperature_interpolant}
+            )
 
         # Setup
         if solver is None:

tests/unit/test_experiments/test_experiment.py

@@ -5,6 +5,7 @@
 from datetime import datetime
 import pybamm
 import pytest
+import numpy as np
 
 
 class TestExperiment:
@@ -214,3 +215,37 @@ def test_set_next_start_time(self):
 
         # TODO: once #3176 is completed, the test should pass for
         # operating_conditions_steps (or equivalent) as well
+
+
+def test_temperature_time_series_simulation():
+    time_data = np.array([0, 600, 1200, 1800])
+    voltage_data = np.array([4.2, 4.0, 3.8, 3.6])
+    temperature_data = np.array([298.15, 310.15, 305.15, 300.00])
+
+    voltage_profile = np.column_stack((time_data, voltage_data))
+    temperature_profile = np.column_stack((time_data, temperature_data))
+
+    experiment = pybamm.Experiment(
+        [pybamm.step.voltage(voltage_profile, temperature=temperature_profile)]
+    )
+
+    model = pybamm.lithium_ion.DFN()
+
+    param_values = pybamm.ParameterValues("Marquis2019")
+    param_values.update({"Ambient temperature [K]": 298.15})
+
+    sim = pybamm.Simulation(model, experiment=experiment, parameter_values=param_values)
+    sim.build()
+
+    ambient_temp = sim.parameter_values["Ambient temperature [K]"]
+    assert hasattr(ambient_temp, "evaluate"), (
+        "Ambient temperature parameter is not time-dependent as expected."
+    )
+
+    t_eval = 600
+    interpolated_temp = ambient_temp.evaluate(t=t_eval)
+    np.testing.assert_allclose(interpolated_temp, 310.15, atol=1e-3)
+
+    t_eval2 = 1200
+    interpolated_temp2 = ambient_temp.evaluate(t=t_eval2)
+    np.testing.assert_allclose(interpolated_temp2, 305.15, atol=1e-3)