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Clip beam projections before multiplying by irradiance #2913

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7ad7cf9
Clip beam projections before multiplying by irradiance
Noumenon-ai Oct 21, 2026
7a805b4
Add what's new entry for beam clipping fix
Noumenon-ai Oct 21, 2026
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6 changes: 6 additions & 0 deletions docs/sphinx/source/whatsnew/v0.16.2.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,11 @@ Bug fixes
is scalar (:issue:`2881`, :pull:`2882`)
* :py:func:`pvlib.scaling.wvm` no longer returns all NaNs when ``positions``
contains a single site (:issue:`2895`, :pull:`2896`)
* :py:func:`pvlib.irradiance.beam_component` and
:py:func:`pvlib.irradiance.poa_components` now clip the angle of incidence
projection before multiplying by ``dni``, so negative DNI no longer yields
positive beam irradiance when the sun is behind the surface.
(:issue:`2903`, :pull:`2913`)

Enhancements
~~~~~~~~~~~~
Expand Down Expand Up @@ -69,3 +74,4 @@ Contributors
* jason-writer (:ghuser:`jason-writer`)
* :ghuser:`bfs2021`
* :ghuser:`xiajiahang`
* :ghuser:`Noumenon-ai`
8 changes: 4 additions & 4 deletions pvlib/irradiance.py
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Expand Up @@ -268,9 +268,9 @@ def beam_component(surface_tilt, surface_azimuth, solar_zenith, solar_azimuth,
beam : numeric
Beam component. [Wm⁻²]
"""
beam = dni * aoi_projection(surface_tilt, surface_azimuth,
projection = aoi_projection(surface_tilt, surface_azimuth,
solar_zenith, solar_azimuth)
beam = np.maximum(beam, 0)
beam = dni * np.maximum(projection, 0)

return beam

Expand Down Expand Up @@ -545,7 +545,7 @@ def poa_components(aoi, dni, poa_sky_diffuse, poa_ground_diffuse):

Notes
------
Negative beam irradiation due to AOI > 90° or AOI < 0° is set to zero.
Beam irradiance is set to zero when the sun is behind the surface.
'''

if isinstance(poa_sky_diffuse, dict):
Expand All @@ -558,7 +558,7 @@ def poa_components(aoi, dni, poa_sky_diffuse, poa_ground_diffuse):
sky_components = {}
total_poa_sky_diffuse = poa_sky_diffuse

poa_direct = np.maximum(dni * np.cos(np.radians(aoi)), 0)
poa_direct = dni * np.maximum(np.cos(np.radians(aoi)), 0)
poa_diffuse = total_poa_sky_diffuse + poa_ground_diffuse
poa_global = poa_direct + poa_diffuse

Expand Down
19 changes: 19 additions & 0 deletions tests/test_irradiance.py
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Expand Up @@ -693,6 +693,25 @@ def test_get_total_irradiance_missing_airmass():
'poa_ground_diffuse']


@pytest.mark.parametrize('array_type', [np.array, pd.Series])
def test_beam_component_negative_dni(array_type):
solar_zenith = array_type([120., 120., 60., 60., 90., 90., np.nan])
dni = array_type([-10., 100., -10., 100., -10., 100., 100.])
result = irradiance.beam_component(0, 180, solar_zenith, 180, dni)
assert_allclose(result, [0., 0., -5., 50., 0., 0., np.nan], atol=1e-12)


@pytest.mark.parametrize('array_type', [np.array, pd.Series])
def test_poa_components_negative_dni(array_type):
aoi = array_type([120., 120., 60., 60., 90., 90., np.nan])
dni = array_type([-10., 100., -10., 100., -10., 100., 100.])
result = irradiance.poa_components(aoi, dni, 10., 5.)
assert_allclose(result['poa_direct'],
[0., 0., -5., 50., 0., 0., np.nan], atol=1e-12)
assert_allclose(result['poa_global'],
[15., 15., 10., 65., 15., 15., np.nan])


def test_poa_components(irrad_data, ephem_data, dni_et, relative_airmass):
aoi = irradiance.aoi(40, 180, ephem_data['apparent_zenith'],
ephem_data['azimuth'])
Expand Down