surface form for SPMe

[rtimms]

At the moment if you pass the option {"surface form":"differential"} or {"surface form": "algebraic"} to SPMe nothing happens. SPMe always uses pybamm.electrolyte_conductivity.Composite.

We should either raise an OptionError or add the relevant surface models for SPMe

[brosaplanella]

I tried implementing this in #884 in case it was a quick fix but I am getting errors for both models (full and leading-order). For the moment I set it to throw a NotImplementedError so if that is enough we may close this issue once #884 is merged.

Otherwise, if we want to implement the model, we need to derive the appropriate surface form for Composite. Is there any reference on this kind of formulation?

[valentinsulzer]

There is my thesis, if you are feeling brave, but I wouldn't go down that route. In theory the leading order form should work though. What was the error?

[brosaplanella]

The differential works but the algebraic doesn't. Here is the error:

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ERROR: test_surface_form_algebraic (__main__.TestSPMe)
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Traceback (most recent call last):
  File "/home/ferranbrosa/PyBaMM/tests/unit/test_models/test_full_battery_models/test_lithium_ion/test_spme.py", line 119, in test_surface_form_algebraic
    model.check_well_posedness()
  File "/home/ferranbrosa/PyBaMM/pybamm/models/base_model.py", line 377, in check_well_posedness
    self.check_well_determined(post_discretisation)
  File "/home/ferranbrosa/PyBaMM/pybamm/models/base_model.py", line 469, in check_well_determined
    raise pybamm.ModelError("model is overdetermined (repeated keys)")
pybamm.expression_tree.exceptions.ModelError: model is overdetermined (repeated keys)

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