Issue #2245 Infinite sheds beam fraction on ground zenith guardrail syntax bug

docs/sphinx/source/whatsnew/v0.11.3.rst

@@ -10,7 +10,8 @@ Deprecations
 
 Enhancements
 ~~~~~~~~~~~~
-
+Fix bug in :py:func:`pvlib.bifacial.get_irradiance_poa` which may had yielded non-zero ground
+irradiance with sun below horizon (:issue:`2245`, :pull:`2359`)
 
 Documentation
 ~~~~~~~~~~~~~
@@ -37,4 +38,5 @@ Contributors
 ~~~~~~~~~~~~
 * Rajiv Daxini (:ghuser:`RDaxini`)
 * Mark Campanelli (:ghuser:`markcampanelli`)
+* Jason Lun Leung (:ghuser:`jason-rpkt`)
 * Manoj K S (:ghuser:`manojks1999`)

pvlib/bifacial/infinite_sheds.py

@@ -260,8 +260,9 @@ def get_irradiance_poa(surface_tilt, surface_azimuth, solar_zenith,
     Returns
     -------
     output : dict or DataFrame
-        Output is a DataFrame when input ghi is a Series. See Notes for
-        descriptions of content.
+        Output is a ``pandas.DataFrame`` when ``ghi`` is a Series.
+        Otherwise it is a dict of ``numpy.ndarray``
+        See Notes for descriptions of content.
 
     Notes
     -----
@@ -372,7 +373,7 @@ def get_irradiance_poa(surface_tilt, surface_azimuth, solar_zenith,
         'poa_global': poa_global, 'poa_direct': poa_direct,
         'poa_diffuse': poa_diffuse, 'poa_ground_diffuse': poa_gnd_pv,
         'poa_sky_diffuse': poa_sky_pv, 'shaded_fraction': f_x}
-    if isinstance(poa_global, pd.Series):
+    if isinstance(ghi, pd.Series):
         output = pd.DataFrame(output)
     return output
 

pvlib/bifacial/utils.py

@@ -87,7 +87,8 @@ def _unshaded_ground_fraction(surface_tilt, surface_azimuth, solar_zenith,
                                         surface_azimuth)
     f_gnd_beam = 1.0 - np.minimum(
         1.0, gcr * np.abs(cosd(surface_tilt) + sind(surface_tilt) * tan_phi))
-    np.where(solar_zenith > max_zenith, 0., f_gnd_beam)  # [1], Eq. 4
+    # [1], Eq. 4
+    f_gnd_beam = np.where(solar_zenith > max_zenith, 0., f_gnd_beam)
     return f_gnd_beam  # 1 - min(1, abs()) < 1 always
 
 

pvlib/tests/bifacial/test_infinite_sheds.py

@@ -130,6 +130,7 @@ def test_get_irradiance_poa():
     # series inputs
     surface_tilt = pd.Series(surface_tilt)
     surface_azimuth = pd.Series(data=surface_azimuth, index=surface_tilt.index)
+    ghi = pd.Series(data=ghi, index=surface_tilt.index)
     solar_zenith = pd.Series(solar_zenith, index=surface_tilt.index)
     solar_azimuth = pd.Series(data=solar_azimuth, index=surface_tilt.index)
     expected_diffuse = pd.Series(