Skip to content

Horizon coefficient should be allowed to go negative in the Perez transposition model #1239

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 4 commits into from
May 26, 2021
Merged

Horizon coefficient should be allowed to go negative in the Perez transposition model #1239

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
0967fe1
Merged PR 13463: Horizon coefficient should be allowed to go negative…
cpr-chas May 21, 2021
fbda954
Merged PR 13472: Fix reported Stickler issues
cpr-chas May 21, 2021
19b3f98
Merged PR 13479: Final changes to meet formatting requirements
cpr-chas May 22, 2021
2626263
Add appropriate details of the bug fix to the 'what's new' content.
cpr-chas May 24, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 7 additions & 0 deletions docs/sphinx/source/whatsnew/v0.9.0.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,12 @@ Enhancements

Bug fixes
~~~~~~~~~
* Corrected an error in :py:func:`~pvlib.irradiance.perez` where the horizon
irradiance component was prevented from taking negative values. Negative
values are intentional according to the original publication. Changes in
output are expected to be small and primarily occur at low irradiance
conditions.
(:issue:`1238`, :pull:`1239`)
* Pass weather data to solar position calculations in
:py:meth:`~pvlib.modelchain.ModelChain.prepare_inputs_from_poa`.
(:issue:`1065`, :pull:`1140`)
Expand Down Expand Up @@ -176,3 +182,4 @@ Contributors
* Tony Lorenzo (:ghuser:`alorenzo175`)
* Damjan Postolovski (:ghuser:`dpostolovski`)
* Joe Ranalli (:ghuser:`jranalli`)
* Chas Schweizer (:ghuser:`cpr-chas`)
1 change: 0 additions & 1 deletion pvlib/irradiance.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1126,7 +1126,6 @@ def perez(surface_tilt, surface_azimuth, dhi, dni, dni_extra,
F1 = np.maximum(F1, 0)

F2 = (F2c[ebin, 0] + F2c[ebin, 1] * delta + F2c[ebin, 2] * z)
F2 = np.maximum(F2, 0)

A = aoi_projection(surface_tilt, surface_azimuth,
solar_zenith, solar_azimuth)
Expand Down
58 changes: 52 additions & 6 deletions pvlib/tests/test_irradiance.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -248,6 +248,52 @@ def test_perez_components(irrad_data, ephem_data, dni_et, relative_airmass):
assert_series_equal(sum_components, expected_for_sum, check_less_precise=2)


def test_perez_negative_horizon():
times = pd.date_range(start='20190101 11:30:00', freq='1H',
periods=5, tz='US/Central')

# Avoid test dependencies on functionality not being tested by hard-coding
# the inputs. This data corresponds to Goodwin Creek in the afternoon on
# 1/1/2019.
# dni_e is slightly rounded from irradiance.get_extra_radiation
# airmass from atmosphere.get_relative_airmas
inputs = pd.DataFrame(np.array(
[[ 158, 19, 1, 0, 0],
[ 249, 165, 136, 93, 50],
[ 57.746951, 57.564205, 60.813841, 66.989435, 75.353368],
[ 171.003315, 187.346924, 202.974357, 216.725599, 228.317233],
[1414, 1414, 1414, 1414, 1414],
[ 1.869315, 1.859981, 2.044429, 2.544943, 3.900136]]).T,
columns=['dni', 'dhi', 'solar_zenith',
'solar_azimuth', 'dni_extra', 'airmass'],
index=times
)

out = irradiance.perez(34, 180, inputs['dhi'], inputs['dni'],
inputs['dni_extra'], inputs['solar_zenith'],
inputs['solar_azimuth'], inputs['airmass'],
model='allsitescomposite1990',
return_components=True)

# sky_diffuse can be less than isotropic under certain conditions as
# horizon goes negative
expected = pd.DataFrame(np.array(
[[281.410185, 152.20879, 123.867898, 82.836412, 43.517015],
[166.785419, 142.24475, 119.173875, 83.525150, 45.725931],
[113.548755, 16.09757, 9.956174, 3.142467, 0],
[ 1.076010, -6.13353, -5.262151, -3.831230, -2.208923]]).T,
columns=['sky_diffuse', 'isotropic', 'circumsolar', 'horizon'],
index=times
)

expected_for_sum = expected['sky_diffuse'].copy()
sum_components = out.iloc[:, 1:].sum(axis=1)
sum_components.name = 'sky_diffuse'

assert_frame_equal(out, expected, check_less_precise=2)
assert_series_equal(sum_components, expected_for_sum, check_less_precise=2)


def test_perez_arrays(irrad_data, ephem_data, dni_et, relative_airmass):
dni = irrad_data['dni'].copy()
dni.iloc[2] = np.nan
Expand Down Expand Up @@ -608,7 +654,7 @@ def test_gti_dirint():
expected_col_order = ['ghi', 'dni', 'dhi']
expected = pd.DataFrame(array(
[[ 21.05796198, 0. , 21.05796198],
[ 288.22574368, 60.59964218, 245.37532576],
[ 291.40037163, 63.41290679, 246.56067523],
[ 931.04078010, 695.94965324, 277.06172442]]),
columns=expected_col_order, index=times)

Expand All @@ -632,7 +678,7 @@ def test_gti_dirint():

expected = pd.DataFrame(array(
[[ 21.05796198, 0. , 21.05796198],
[ 289.81109139, 60.52460392, 247.01373353],
[ 293.21310935, 63.27500913, 248.47092131],
[ 932.46756378, 648.05001357, 323.49974813]]),
columns=expected_col_order, index=times)

Expand All @@ -646,8 +692,8 @@ def test_gti_dirint():

expected = pd.DataFrame(array(
[[ 21.3592591, 0. , 21.3592591 ],
[ 292.5162373, 64.42628826, 246.95997198],
[ 941.6753031, 727.16311901, 258.36548605]]),
[ 294.4985420, 66.25848451, 247.64671830],
[ 941.7943404, 727.50552952, 258.16276278]]),
columns=expected_col_order, index=times)

assert_frame_equal(output, expected)
Expand All @@ -659,8 +705,8 @@ def test_gti_dirint():
temp_dew=temp_dew)

expected = pd.DataFrame(array(
[[ 21.05796198, 0. , 21.05796198],
[ 292.40468994, 36.79559287, 266.3862767 ],
[[ 21.05796198, 0., 21.05796198],
[ 295.06070190, 38.20346345, 268.0467738],
[ 931.79627208, 689.81549269, 283.5817439]]),
columns=expected_col_order, index=times)

Expand Down