Fix cell type inference for First Solar thin-film modules (CdTe, not CIGS)

docs/sphinx/source/whatsnew/v0.16.2.rst

@@ -14,6 +14,9 @@ Deprecations
 
 Bug fixes
 ~~~~~~~~~
+* :py:class:`pvlib.pvsystem.Array` now infers First Solar modules listed
+  as "Thin Film" in the CEC database as CdTe instead of CIGS; "Thin Film"
+  is otherwise mapped to CIGS.  (:issue:`1984`)
 * Correct the Series name in ``ModelChain.results.dc_ohmic_losses`` from
   ``i_mp`` to ``p_dc_ohmic_loss`` when using ``dc_ohms_from_percent``.
   (:issue:`1959`, :pull:`2912`)
@@ -75,6 +78,7 @@ Contributors
 * Rajiv Daxini (:ghuser:`rdaxini`)
 * jason-writer (:ghuser:`jason-writer`)
 * :ghuser:`mmporong`
+* :ghuser:`DresdenGman`
 * :ghuser:`bfs2021`
 * :ghuser:`xiajiahang`
 * Jakub Krasuski (:ghuser:`Blizzeq`)

pvlib/pvsystem.py

@@ -1109,7 +1109,12 @@ def _infer_cell_type(self):
 
         if 'Technology' in self.module_parameters.keys():
             # CEC module parameter set
-            cell_type = _cell_type_dict[self.module_parameters['Technology']]
+            technology = self.module_parameters['Technology']
+            cell_type = _cell_type_dict[technology]
+            if technology == 'Thin Film' and self._is_first_solar_module():
+                # First Solar modules labeled "Thin Film" are CdTe,
+                # but that technology maps to CIGS above
+                cell_type = 'cdte'
         elif 'Material' in self.module_parameters.keys():
             # Sandia module parameter set
             cell_type = _cell_type_dict[self.module_parameters['Material']]
@@ -1118,6 +1123,33 @@ def _infer_cell_type(self):
 
         return cell_type
 
+    def _is_first_solar_module(self):
+        """
+        Whether the module is made by First Solar, based on the module
+        name.  The name is taken from the ``module`` attribute or, if
+        ``module_parameters`` is a Series, from its name (e.g. the column
+        name when selected from a database retrieved with
+        :py:func:`retrieve_sam`).  The normalized name must start with
+        the manufacturer's name, followed by a non-letter boundary, so
+        that names merely containing "First Solar" do not match.
+
+        Returns
+        -------
+        bool
+
+        """
+        names = [self.module,
+                 getattr(self.module_parameters, 'name', None)]
+        for name in names:
+            if name is None:
+                continue
+            normalized = str(name).lower().replace('_', ' ').strip()
+            if normalized.startswith('first solar'):
+                rest = normalized[len('first solar'):]
+                if not rest or not rest[0].isalpha():
+                    return True
+        return False
+
     def get_aoi(self, solar_zenith, solar_azimuth):
         """
         Get the angle of incidence on the array.

tests/test_pvsystem.py

@@ -844,6 +844,61 @@ def test_Array__infer_cell_type():
     assert array._infer_cell_type() is None
 
 
+@pytest.mark.parametrize('module, module_parameters, expected', [
+    # First Solar modules labeled "Thin Film" are CdTe, but that
+    # technology is otherwise mapped to CIGS.  GH 1984
+    (None, pd.Series({'Technology': 'Thin Film'},
+                     name='First_Solar__Inc__FS_4117_3'), 'cdte'),
+    ('First Solar, Inc. FS 4117-3', {'Technology': 'Thin Film'}, 'cdte'),
+    # the name in one channel is enough, even if the other channel
+    # holds an unrelated name
+    ('Some_Other_Brand_Module', pd.Series(
+        {'Technology': 'Thin Film'},
+        name='First_Solar__Inc__FS_4117_3'), 'cdte'),
+    # "Thin Film" modules from other manufacturers are still CIGS, as
+    # are "Thin Film" modules with no name to identify them by
+    (None, pd.Series({'Technology': 'Thin Film'},
+                     name='Auria_Solar_M115000'), 'cigs'),
+    (None, pd.Series({'Technology': 'Thin Film'}), 'cigs'),
+    (None, {'Technology': 'Thin Film'}, 'cigs'),
+    # names merely containing "First Solar" are not First Solar modules
+    (None, pd.Series({'Technology': 'Thin Film'},
+                     name='NotFirst_Solar_Model'), 'cigs'),
+    (None, pd.Series({'Technology': 'Thin Film'},
+                     name='First_Solaris_Model'), 'cigs'),
+    (None, pd.Series({'Technology': 'Thin Film'},
+                     name='OtherBrand_First_Solar_Compatible'), 'cigs'),
+    # First Solar's crystalline silicon (TetraSun) modules are not CdTe
+    (None, pd.Series({'Technology': 'Mono-c-Si'},
+                     name='First_Solar__Inc__TS_295_R11_02'), 'monosi'),
+    # the pre-existing mappings are unchanged
+    (None, {'Technology': 'CdTe'}, 'cdte'),
+    (None, {'Technology': 'Multi-c-Si'}, 'multisi'),
+    (None, {'Material': 'CdTe'}, 'cdte'),
+    (None, {'Material': 'mc-Si'}, 'multisi'),
+])
+def test_Array__infer_cell_type_mappings(module, module_parameters,
+                                         expected):
+    array = pvsystem.Array(mount=pvsystem.FixedMount(0, 180),
+                           module=module,
+                           module_parameters=module_parameters)
+    assert array._infer_cell_type() == expected
+
+
+def test_Array__infer_cell_type_first_solar_cecmod():
+    # GH 1984: First Solar modules labeled "Thin Film" in the CEC
+    # database are CdTe modules
+    cec_modules = pvsystem.retrieve_sam('cecmod')
+    module_parameters = cec_modules['First_Solar__Inc__FS_4117_3']
+    # the override only applies to the "Thin Film" rows; assert the
+    # premise so a future correction of the database entry cannot
+    # silently bypass this test's coverage
+    assert module_parameters['Technology'] == 'Thin Film'
+    array = pvsystem.Array(mount=pvsystem.FixedMount(0, 180),
+                           module_parameters=module_parameters)
+    assert array._infer_cell_type() == 'cdte'
+
+
 def _calcparams_correct_Python_type_numeric_type_cases():
     """
     An auxilary function used in the unit tests named