Fix PV potential calculation based on tilt angle #3763
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If we keep both there are chances that one is updated and the other isn't
the comment makes it seem like the calculation is hard coded for the northern hemisphere, but it actually doesn't matter for the calculation whether it's north or south (since calc_optimal_angle returns an absolute value)
also cleaning up unnecessary code and correcting equation 5.4.2
WalkthroughThe pull request introduces significant modifications to solar technology-related modules within the City Energy Analyst (CEA) project. The changes primarily focus on updating solar calculations, including adjustments to constants, function signatures, and calculation methods. Key modifications involve renaming functions, updating import statements, integrating the Changes
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Actionable comments posted: 0
🧹 Nitpick comments (5)
cea/technologies/solar/photovoltaic_thermal.py (1)
183-185: Consider removing commented-out code for cleanliness.The lines of code commented out (lines 183-185) appear to define variables that are no longer used. To improve code readability and maintainability, consider removing these lines if they are not needed.
cea/utilities/solar_equations.py (1)
634-638: Simplify conditional assignment with ternary operator.The
if-elseblock can be simplified using a ternary operator for brevity and clarity.Apply this diff to simplify the code:
- if B != 0: - teta_z = degrees(asin(xdir / sin(B))) # surface azimuth before adjusting for sign convention - else: - # for flat panels, surface azimuth doesn't matter - teta_z = 0 + teta_z = degrees(asin(xdir / sin(B))) if B != 0 else 0 # surface azimuth before adjusting for sign convention🧰 Tools
🪛 Ruff (0.8.2)
634-638: Use ternary operator
teta_z = degrees(asin(xdir / sin(B))) if B != 0 else 0instead ofif-else-block(SIM108)
cea/technologies/solar/photovoltaic.py (3)
167-169: LGTM! Fixed azimuth angle sign convention.The adjustment correctly implements Duffie (2013)'s sign convention where south is 0°, east is negative, and west is positive.
Consider adding a reference to the specific page or equation number in Duffie (2013) in the comment for better traceability:
-# Adjust sign convention: in Duffie (2013), south is 0°, east is negative and west is positive (p. 13) +# Adjust sign convention: in Duffie and Beckman (2013), south is 0°, east is negative and west is positive (Section 1.6, p. 13)
205-208: Remove commented-out code.The old implementation is now replaced with pvlib, so these commented lines can be safely removed.
- # teta_rad = pd.Series(index=radiation_Wperm2.index, - # data=np.vectorize(calc_angle_of_incidence)(g_rad, lat, ha_rad, tilt_rad, teta_z_rad), - # name='aoi')
393-395: LGTM! Using corrected glazing extinction coefficient.The transmittance-absorptance calculation now uses the corrected glazing extinction coefficient (K=4 m^-1).
Consider adding a reference to the equation in Duffie and Beckman (2013):
-# transmittance-absorptance product at normal incidence +# transmittance-absorptance product at normal incidence (Duffie and Beckman, 2013, Eq. 5.1.1)
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cea/technologies/solar/constants.py(2 hunks)cea/technologies/solar/photovoltaic.py(12 hunks)cea/technologies/solar/photovoltaic_thermal.py(4 hunks)cea/technologies/solar/solar_collector.py(4 hunks)cea/utilities/solar_equations.py(5 hunks)
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cea/technologies/solar/photovoltaic.py
200-200: Local variable teta_z_rad is assigned to but never used
Remove assignment to unused variable teta_z_rad
(F841)
cea/utilities/solar_equations.py
634-638: Use ternary operator teta_z = degrees(asin(xdir / sin(B))) if B != 0 else 0 instead of if-else-block
(SIM108)
🪛 GitHub Actions: Ruff
cea/technologies/solar/photovoltaic.py
[error] 8-8: Unused import: math.atan is imported but never used in the code
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🔇 Additional comments (16)
cea/technologies/solar/photovoltaic_thermal.py (6)
16-16: LGTM: Import of pvlib module.The addition of the
pvlibimport is appropriate and necessary for the updated solar calculations.
23-23: LGTM: Updated import statement toget_properties_PV_db.The import statement correctly reflects the renaming of
calc_properties_PV_dbtoget_properties_PV_db.
77-77: LGTM: Updated function call toget_properties_PV_db.The function call correctly uses the updated
get_properties_PV_dbfunction to retrieve panel properties.
178-179: Ensure correct adjustment of azimuth angle sign convention.The adjustment
Az = solar_properties.Az - 180modifies the azimuth angle to match the sign convention from Duffie (2013). Verify that this change is correctly integrated into all subsequent calculations that useAz, and that there are no inconsistencies in the sign conventions throughout the code.
227-227: LGTM: Updated function call tocalc_radiation_type.The function call correctly reflects the renaming from
cal_radiation_typetocalc_radiation_type.
231-232: Verify correctness of angle calculations usingpvlib.irradiance.aoi.Ensure that the parameters passed to
pvlib.irradiance.aoiare in degrees and correctly represent the surface tilt angle (tilt_angle_deg), surface azimuth angle (teta_z_deg), solar zenith angle (solar_properties.Sz), and solar azimuth angle (Az). Confirm that the units and sign conventions are consistent, especially considering the adjustment made toAz.cea/technologies/solar/constants.py (2)
4-7: LGTM: Addition of reference material to docstring.Including the reference to Duffie and Beckman (2013) enhances the documentation and helps users understand the source of the constants.
22-22: Update ofKvalue to correct constant in line with reference.The glazing extinction coefficient
Khas been updated from0.4to4, aligning with Duffie and Beckman (2013). Ensure that this change is correctly propagated through all calculations that depend onK.cea/utilities/solar_equations.py (3)
401-402: Verify assumption of surface azimuth in optimal angle calculation.The code assumes a surface azimuth of 0 degrees when calculating the optimal angle for flat roofs, implying the optimal angle will be the same for south- and north-facing panels. Confirm that this assumption is valid for your application and that it aligns with the intended behavior of the model.
529-529: LGTM: Updated tilt angle range to include zero degrees.The condition now includes tilt angles where
Bequals 0 degrees, correctly categorizing perfectly flat roofs.
783-783: LGTM: Renamed function tocalc_radiation_type.The function name correction from
cal_radiation_typetocalc_radiation_typefixes a typographical error and improves code readability.cea/technologies/solar/photovoltaic.py (2)
93-93: LGTM! Improved function naming.The rename from
calc_properties_PV_dbtoget_properties_PV_dbbetter reflects the function's purpose of retrieving properties rather than calculating them.
203-204: LGTM! Using pvlib for incident angle calculation.Using
pvlib.irradiance.aoiimproves reliability by leveraging a well-tested library implementation.cea/technologies/solar/solar_collector.py (3)
764-766: LGTM! Consistent azimuth angle sign convention.The adjustment maintains consistency with photovoltaic.py in implementing Duffie (2013)'s sign convention.
773-774: LGTM! Consistent use of pvlib for incident angle calculation.Using
pvlib.irradiance.aoimaintains consistency with photovoltaic.py and improves reliability.
Line range hint
1-1: Verify the impact of the fixes.The changes address all three objectives from the PR description. Let's verify the impact:
✅ Verification successful
All fixes are properly implemented and consistent ✓
- Azimuth angle sign convention matches Duffie (2013) across all solar technology files
- Glazing extinction coefficient K is correctly set to 4
- Angle of incidence calculation is centralized and validated against Sandia pvlib
🏁 Scripts executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash # Description: Verify the changes improve PV performance at optimal tilt angles # Test 1: Check that the azimuth angle adjustment is consistent across files echo "Checking azimuth angle adjustment consistency..." rg -A 1 "Adjust sign convention.*Duffie" # Test 2: Verify K constant is set to 4 echo "Checking glazing extinction coefficient..." rg "K = " cea/technologies/solar/constants.py # Test 3: Look for any remaining references to the old equation echo "Checking for any remaining references to the old equation..." rg "calc_angle_of_incidence"Length of output: 1543
Script:
#!/bin/bash # Check the implementation of calc_angle_of_incidence echo "Checking angle of incidence implementation..." rg -A 10 "def calc_angle_of_incidence" cea/utilities/solar_equations.py # Verify no other angle calculations exist echo "Checking for other angle calculations..." ast-grep --pattern 'def calc_angle_of_incidence'Length of output: 800
Script:
#!/bin/bash # Get the full implementation including the return statement echo "Full implementation of calc_angle_of_incidence..." rg -A 20 "def calc_angle_of_incidence" cea/utilities/solar_equations.pyLength of output: 998
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🧹 Nitpick comments (1)
cea/technologies/solar/photovoltaic.py (1)
200-200: Remove unused variable.The variable
teta_z_radis assigned but never used.- teta_z_rad = radians(teta_z_deg) # surface azimuth🧰 Tools
🪛 Ruff (0.8.2)
200-200: Local variable
teta_z_radis assigned to but never usedRemove assignment to unused variable
teta_z_rad(F841)
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cea/technologies/solar/photovoltaic.py(13 hunks)
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🪛 Ruff (0.8.2)
cea/technologies/solar/photovoltaic.py
200-200: Local variable teta_z_rad is assigned to but never used
Remove assignment to unused variable teta_z_rad
(F841)
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🔇 Additional comments (6)
cea/technologies/solar/photovoltaic.py (6)
167-168: LGTM! Correct implementation of azimuth angle adjustment.The adjustment
Az = solar_properties.Az - 180properly aligns with Duffie (2013) convention where south is 0°, east is negative, and west is positive.
203-207: Good improvement using pvlib for angle calculations.Replacing the manual angle of incidence calculation with
pvlib.irradiance.aoiis a good choice as it uses a well-tested implementation.
323-324: LGTM! Correct implementation of diffuse radiation equations.The equations for
teta_edandteta_eGnow properly match equations 5.4.1 and 5.4.2 from Duffie and Beckman (2013).
425-427: LGTM! Correct implementation of absorbed radiation calculation.The absorbed radiation calculation properly accounts for beam, diffuse, and ground-reflected components with correct geometric factors.
493-499: LGTM! Clear documentation of assumptions.The documentation clearly explains the assumptions for:
- Tilt angle calculation
- Row spacing optimization
- Surface azimuth determination
157-157: Verify the impact of function signature changes across the codebase.The function renaming and parameter changes might affect other modules.
Run this script to check for any missed updates:
Also applies to: 632-632
✅ Verification successful
Function signature changes have been properly propagated
The codebase has been updated consistently:
- All references use the new
get_properties_PV_dbfunction name- No calls to
calc_pv_generationinclude the removed latitude parameter🏁 Scripts executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash # Check for any remaining references to old function name and signature rg "calc_properties_PV_db" rg "calc_pv_generation.*latitude"Length of output: 62
Script:
#!/bin/bash # Search for PV-related function definitions and calls ast-grep --pattern 'def get_properties_PV_db' ast-grep --pattern 'def calc_pv_generation' # Search for any PV-related imports and function calls with context rg -A 2 -B 2 "from cea.technologies.solar.photovoltaic import" rg -A 2 -B 2 "properties_PV_db|pv_generation" --type pythonLength of output: 1343
Script:
#!/bin/bash # Search for any remaining references to PV-related functions with context rg -A 2 -B 2 "properties_PV_db|pv_generation" # Search for any python files containing PV-related content fd -e py -x grep -l "photovoltaic"Length of output: 3281
|
Wow - this sounds great by just reading at your text @martin-mosteiro |
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Actionable comments posted: 0
🧹 Nitpick comments (4)
cea/technologies/solar/photovoltaic.py (2)
167-171: LGTM: Azimuth angle sign convention aligns with Duffie (2013).The adjustment of azimuth angle sign convention (south = 0°, east negative, west positive) correctly follows the standard convention in Duffie (2013).
Consider using a ternary operator for more concise code:
-if latitude >= 0: - Az = solar_properties.Az - 180 # south is 0°, east is negative and west is positive (p. 13) -else: - Az = solar_properties.Az # north is 0° +Az = solar_properties.Az - 180 if latitude >= 0 else solar_properties.Az # south is 0° for northern hemisphere🧰 Tools
🪛 Ruff (0.8.2)
168-171: Use ternary operator
Az = solar_properties.Az - 180 if latitude >= 0 else solar_properties.Azinstead ofif-else-block(SIM108)
206-210: Enhancement: Improved angle of incidence calculation using pvlib.The switch to
pvlib.irradiance.aoiimproves accuracy and maintainability by using a well-tested library implementation.The commented-out code can be safely removed since it's replaced by the pvlib implementation.
cea/technologies/solar/photovoltaic_thermal.py (1)
178-182: LGTM: Consistent azimuth angle convention.The azimuth angle adjustment matches the implementation in photovoltaic.py, maintaining consistency.
Consider using a ternary operator for more concise code:
-if latitude >= 0: - Az = solar_properties.Az - 180 # south is 0°, east is negative and west is positive (p. 13) -else: - Az = solar_properties.Az # north is 0° +Az = solar_properties.Az - 180 if latitude >= 0 else solar_properties.Az # south is 0° for northern hemisphere🧰 Tools
🪛 Ruff (0.8.2)
179-182: Use ternary operator
Az = solar_properties.Az - 180 if latitude >= 0 else solar_properties.Azinstead ofif-else-block(SIM108)
cea/technologies/solar/solar_collector.py (1)
764-768: LGTM: Consistent azimuth angle convention across solar modules.The azimuth angle adjustment maintains consistency with photovoltaic.py and photovoltaic_thermal.py.
Consider using a ternary operator for more concise code:
-if latitude_deg >= 0: - Az = solar_properties.Az - 180 # south is 0°, east is negative and west is positive (p. 13) -else: - Az = solar_properties.Az # north is 0° +Az = solar_properties.Az - 180 if latitude_deg >= 0 else solar_properties.Az # south is 0° for northern hemisphere🧰 Tools
🪛 Ruff (0.8.2)
765-768: Use ternary operator
Az = solar_properties.Az - 180 if latitude_deg >= 0 else solar_properties.Azinstead ofif-else-block(SIM108)
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cea/technologies/solar/photovoltaic.py(12 hunks)cea/technologies/solar/photovoltaic_thermal.py(4 hunks)cea/technologies/solar/solar_collector.py(4 hunks)
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🪛 Ruff (0.8.2)
cea/technologies/solar/solar_collector.py
765-768: Use ternary operator Az = solar_properties.Az - 180 if latitude_deg >= 0 else solar_properties.Az instead of if-else-block
(SIM108)
cea/technologies/solar/photovoltaic_thermal.py
179-182: Use ternary operator Az = solar_properties.Az - 180 if latitude >= 0 else solar_properties.Az instead of if-else-block
(SIM108)
cea/technologies/solar/photovoltaic.py
168-171: Use ternary operator Az = solar_properties.Az - 180 if latitude >= 0 else solar_properties.Az instead of if-else-block
(SIM108)
203-203: Local variable teta_z_rad is assigned to but never used
Remove assignment to unused variable teta_z_rad
(F841)
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🔇 Additional comments (3)
cea/technologies/solar/photovoltaic.py (1)
326-326: Fixed equation 5.4.2 for diffuse radiation calculation.The correction aligns with Duffie and Beckman (2013) by using the correct coefficient in the equation.
cea/technologies/solar/photovoltaic_thermal.py (1)
233-235: Enhancement: Consistent use of pvlib for angle calculations.The switch to
pvlib.irradiance.aoimaintains consistency with photovoltaic.py.cea/technologies/solar/solar_collector.py (1)
776-777: Enhancement: Standardized angle calculations using pvlib.The switch to
pvlib.irradiance.aoicompletes the standardization of angle calculations across all solar technology modules.
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Actionable comments posted: 1
🧹 Nitpick comments (2)
cea/utilities/solar_equations.py (1)
634-639: Good addition of special case for flat panels!The code correctly handles flat panels by setting azimuth to 0° since orientation doesn't matter when tilt is 0°.
Consider using a ternary operator for more concise code:
- if B != 0: - teta_z = degrees(asin(xdir / sin(B))) # surface azimuth before adjusting for sign convention - else: - # for flat panels, surface azimuth doesn't matter - teta_z = 0 + # surface azimuth before adjusting for sign convention (0° for flat panels as azimuth doesn't matter) + teta_z = degrees(asin(xdir / sin(B))) if B != 0 else 0🧰 Tools
🪛 Ruff (0.8.2)
634-638: Use ternary operator
teta_z = degrees(asin(xdir / sin(B))) if B != 0 else 0instead ofif-else-block(SIM108)
cea/technologies/solar/photovoltaic.py (1)
167-172: Excellent fix for azimuth sign convention!The code now correctly implements the Duffie (2013) convention:
- Northern hemisphere: south is 0°, east is negative, west is positive
- Southern hemisphere: north is 0°
This resolves the core issue where tilted panels were yielding less electricity than flat panels.
Consider using a ternary operator for more concise code:
- if latitude >= 0: - Az = solar_properties.Az - 180 # south is 0°, east is negative and west is positive (p. 13) - else: - Az = solar_properties.Az # north is 0° + # Adjust azimuth: In northern hemisphere, south is 0° (east negative, west positive) + # In southern hemisphere, north is 0° + Az = solar_properties.Az - 180 if latitude >= 0 else solar_properties.Az🧰 Tools
🪛 Ruff (0.8.2)
168-171: Use ternary operator
Az = solar_properties.Az - 180 if latitude >= 0 else solar_properties.Azinstead ofif-else-block(SIM108)
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🪛 Ruff (0.8.2)
cea/technologies/solar/photovoltaic.py
168-171: Use ternary operator Az = solar_properties.Az - 180 if latitude >= 0 else solar_properties.Az instead of if-else-block
(SIM108)
203-203: Local variable teta_z_rad is assigned to but never used
Remove assignment to unused variable teta_z_rad
(F841)
cea/utilities/solar_equations.py
634-638: Use ternary operator teta_z = degrees(asin(xdir / sin(B))) if B != 0 else 0 instead of if-else-block
(SIM108)
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🔇 Additional comments (5)
cea/utilities/solar_equations.py (3)
239-244: Documentation improvements look good!The added comments clearly explain the filtering conditions for sensor points and hours with low radiation potential.
399-402: Documentation improvement enhances understanding!The added comment correctly explains that panels facing the equator (surface azimuth = 0° or 180°) yield identical results, which is physically accurate.
529-529: Good fix to include 0° tilt angle!The condition now correctly includes perfectly flat panels (0°) in the first category, which aligns with the PR objectives.
cea/technologies/solar/photovoltaic.py (2)
326-326: Good fix for equation 5.4.2!The implementation now correctly matches Duffie and Beckman (2013), and the variable naming is more consistent.
496-502: Documentation improvements enhance code understanding!The assumptions about tilt angles are now clearly documented:
- Tilted roof: panel tilt matches roof tilt
- Wall: 90° tilt
- Flat roof: tilt determined by Quinn et al. method
| # teta_z_deg = radians(teta_z_deg) # surface azimuth | ||
| teta_z_rad = radians(teta_z_deg) # surface azimuth | ||
|
|
||
| # calculate effective incident angles necessary | ||
| teta_deg = pvlib.irradiance.aoi(tilt_angle_deg, teta_z_deg, solar_properties.Sz, solar_properties.Az) | ||
| teta_rad = teta_rad = [radians(x) for x in teta_deg] | ||
| teta_deg = pvlib.irradiance.aoi(tilt_angle_deg, teta_z_deg, solar_properties.Sz, Az) | ||
| teta_rad = [radians(x) for x in teta_deg] | ||
| # teta_rad = pd.Series(index=radiation_Wperm2.index, | ||
| # data=np.vectorize(calc_angle_of_incidence)(g_rad, lat, ha_rad, tilt_rad, teta_z_rad), | ||
| # name='aoi') | ||
|
|
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🛠️ Refactor suggestion
Good switch to pvlib for angle of incidence calculation!
Using pvlib.irradiance.aoi is a better choice as it's a well-tested implementation. However, some cleanup is needed:
- Remove the commented-out code (lines 208-210) as it's replaced by pvlib
- Remove the unused variable
teta_z_rad(line 203)
- teta_z_rad = radians(teta_z_deg) # surface azimuth
teta_deg = pvlib.irradiance.aoi(tilt_angle_deg, teta_z_deg, solar_properties.Sz, Az)
teta_rad = [radians(x) for x in teta_deg]
- # teta_rad = pd.Series(index=radiation_Wperm2.index,
- # data=np.vectorize(calc_angle_of_incidence)(g_rad, lat, ha_rad, tilt_rad, teta_z_rad),
- # name='aoi')📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| # teta_z_deg = radians(teta_z_deg) # surface azimuth | |
| teta_z_rad = radians(teta_z_deg) # surface azimuth | |
| # calculate effective incident angles necessary | |
| teta_deg = pvlib.irradiance.aoi(tilt_angle_deg, teta_z_deg, solar_properties.Sz, solar_properties.Az) | |
| teta_rad = teta_rad = [radians(x) for x in teta_deg] | |
| teta_deg = pvlib.irradiance.aoi(tilt_angle_deg, teta_z_deg, solar_properties.Sz, Az) | |
| teta_rad = [radians(x) for x in teta_deg] | |
| # teta_rad = pd.Series(index=radiation_Wperm2.index, | |
| # data=np.vectorize(calc_angle_of_incidence)(g_rad, lat, ha_rad, tilt_rad, teta_z_rad), | |
| # name='aoi') | |
| # teta_z_deg = radians(teta_z_deg) # surface azimuth | |
| # calculate effective incident angles necessary | |
| teta_deg = pvlib.irradiance.aoi(tilt_angle_deg, teta_z_deg, solar_properties.Sz, Az) | |
| teta_rad = [radians(x) for x in teta_deg] |
🧰 Tools
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203-203: Local variable teta_z_rad is assigned to but never used
Remove assignment to unused variable teta_z_rad
(F841)
This PR fixes issue #3282. As discussed there (and in #3281), tilted PV panels were producing less electricity than flat ones, even at the optimal tilt angle. After investigating, I realized there was an inconsistent sign convention in the azimuth angle between the geographic coordinates and the ones used by the PV model (from Duffie and Beckman, 2013). After fixing this issue, you indeed get the expected improvement in PV performance as a function of tilt angle. In the process of fixing this issue, I have also found an incorrect constant (K=4 m^-1 from Duffie and Beckman was incorrectly coded as
K=0.4 #m^-1) and one equation that inexplicably didn't match Duffie and Beckman (2013) (eq. 5.4.2 had a factor of59.68instead of 59.7), with marginal effect on the results. This PR fixes those as well. Finally, I have also changed the solar equations so an angle of 0° (flat placement) is possible.Before fixing the issue, here are the results for different PV tilt angles for one case study building:
After fixing the issue, here are the results for the same PV tilt angles for the same case study building:
I have also fixed the azimuth issue on the PVT calculation. I am not sure why the calculation for PVT used a legacy function for angle of incidence (previously used for PV until @shanshanhsieh changed it in 2021), so I've changed it to
pvlib.irradiance.aoito match the PV calculation. After doing so, the PVT potential goes from 134.4 kWh/m2 at 10° and 101.22 kWh/m2 at 30° to 158.27 kWh/m2 at 10° and 171.2 kWh/m2 at 30°.I have done the same for the angle of incidence for the SC calculation.
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Release Notes
New Features
pvliblibrary for improved solar panel performance modeling.Bug Fixes
Documentation
Refactor