Add a model for spectral corrections

README.md

@@ -111,11 +111,24 @@ Please see the [Contributing page](http://pvlib-python.readthedocs.io/en/stable/
 The long-term success of pvlib-python requires substantial community support.
 
 
-License
-=======
+Citing
+======
+
+If you use pvlib-python in a published work, please cite:
+
+  William F. Holmgren, Clifford W. Hansen, and Mark A. Mikofski.
+  "pvlib python: a python package for modeling solar energy systems."
+  Journal of Open Source Software, 3(29), 884, (2018).
+  https://doi.org/10.21105/joss.00884
 
-BSD 3-clause
+Please also cite the DOI corresponding to the specific version of
+pvlib-python that you used. pvlib-python DOIs are listed at
+[Zenodo.org](https://zenodo.org/search?page=1&size=20&q=conceptrecid:593284&all_versions&sort=-version)
 
+If you use pvlib-python in a commercial or publicly-available application, please
+consider displaying one of the "powered by pvlib" logos:
+
+<img src="docs/sphinx/source/_images/pvlib_powered_logo_vert.png" width="300"><img src="docs/sphinx/source/_images/pvlib_powered_logo_horiz.png" width="300">
 
 Getting support
 ===============
@@ -133,19 +146,12 @@ change something about pvlib, then please make an issue on our
 [GitHub issues page](https://github.com/pvlib/pvlib-python/issues).
 
 
-Citing
-======
 
-If you use pvlib-python in a published work, please cite:
+License
+=======
 
-  William F. Holmgren, Clifford W. Hansen, and Mark A. Mikofski.
-  "pvlib python: a python package for modeling solar energy systems."
-  Journal of Open Source Software, 3(29), 884, (2018).
-  https://doi.org/10.21105/joss.00884
+BSD 3-clause.
 
-Please also cite the DOI corresponding to the specific version of
-pvlib-python that you used. pvlib-python DOIs are listed at
-[Zenodo.org](https://zenodo.org/search?page=1&size=20&q=conceptrecid:593284&all_versions&sort=-version)
 
 NumFOCUS
 ========

azure-pipelines.yml

@@ -12,7 +12,7 @@ jobs:
     vmImage: ubuntu-16.04
 
 
-- template: ci/azure/posix.yml
+- template: ci/azure/posix_no_39.yml
   parameters:
     name: Test_bare_macOS
     vmImage: macOS-10.14

ci/azure/posix_no_39.yml

@@ -0,0 +1,39 @@
+parameters:
+  name: ''
+  vmImage: ''
+
+jobs:
+- job: ${{ parameters.name }}
+  pool:
+    vmImage: ${{ parameters.vmImage }}
+  strategy:
+    matrix:
+      Python36:
+        python.version: '3.6'
+      Python37:
+        python.version: '3.7'
+      Python38:
+        python.version: '3.8'
+
+  steps:
+  - task: UsePythonVersion@0
+    inputs:
+      versionSpec: '$(python.version)'
+
+  - script: |
+      pip install pytest pytest-cov pytest-mock requests-mock pytest-timeout pytest-azurepipelines pytest-rerunfailures pytest-remotedata
+      pip install -e .
+      pytest pvlib --junitxml=junit/test-results.xml --cov=com --cov-report=xml --cov-report=html
+    displayName: 'Test with pytest'
+
+  - task: PublishTestResults@2
+    condition: succeededOrFailed()
+    inputs:
+      testResultsFiles: '**/test-*.xml'
+      testRunTitle: 'Publish test results for Python $(python.version)'
+
+  - task: PublishCodeCoverageResults@1
+    inputs:
+      codeCoverageTool: Cobertura
+      summaryFileLocation: '$(System.DefaultWorkingDirectory)/**/coverage.xml'
+      reportDirectory: '$(System.DefaultWorkingDirectory)/**/htmlcov'

ci/requirements-py36-min.yml

@@ -5,6 +5,7 @@ dependencies:
     - coveralls
     - nose
     - pip
+    - pytables  # tables when using pip+PyPI
     - pytest
     - pytest-cov
     - pytest-mock
@@ -20,3 +21,4 @@ dependencies:
         - pytest-rerunfailures # conda version is >3.6
         - pytest-remotedata # conda package is 0.3.0, needs > 0.3.1
         - requests-mock
+        - numexpr==2.6.2 # needed for tables, but newest version is not compatible with numpy 1.12

ci/requirements-py36.yml

@@ -3,6 +3,7 @@ channels:
     - defaults
     - conda-forge
 dependencies:
+    - blosc=1.14.3  # newest version breaks tables (pytables) on windows
     - coveralls
     - cython
     - ephem

ci/requirements-py37.yml

@@ -3,6 +3,7 @@ channels:
     - defaults
     - conda-forge
 dependencies:
+    - blosc=1.14.3  # newest version breaks tables (pytables) on windows
     - coveralls
     - cython
     - ephem

docs/examples/plot_discontinuous_tracking.py

@@ -0,0 +1,89 @@
+"""
+Discontinuous Tracking
+======================
+
+Example of a custom Mount class.
+"""
+
+# %%
+# Many real-world tracking arrays adjust their position in discrete steps
+# rather than through continuous movement. This example shows how to model
+# this discontinuous tracking by implementing a custom Mount class.
+
+from pvlib import tracking, pvsystem, location, modelchain
+from pvlib.temperature import TEMPERATURE_MODEL_PARAMETERS
+import matplotlib.pyplot as plt
+import pandas as pd
+
+
+# %%
+# We'll define our custom Mount by extending
+# :py:class:`~pvlib.pvsystem.SingleAxisTrackerMount` for convenience.
+# Another approach would be to extend ``AbstractMount`` directly; see
+# the source code of :py:class:`~pvlib.pvsystem.SingleAxisTrackerMount`
+# and :py:class:`~pvlib.pvsystem.FixedMount` for how that is done.
+
+
+class DiscontinuousTrackerMount(pvsystem.SingleAxisTrackerMount):
+    # inherit from SingleAxisTrackerMount so that we get the
+    # constructor and tracking attributes (axis_tilt etc) automatically
+
+    def get_orientation(self, solar_zenith, solar_azimuth):
+        # Different trackers update at different rates; in this example we'll
+        # assume a relatively slow update interval of 15 minutes to make the
+        # effect more visually apparent.
+        zenith_subset = solar_zenith.resample('15min').first()
+        azimuth_subset = solar_azimuth.resample('15min').first()
+
+        tracking_data_15min = tracking.singleaxis(
+            zenith_subset, azimuth_subset,
+            self.axis_tilt, self.axis_azimuth,
+            self.max_angle, self.backtrack,
+            self.gcr, self.cross_axis_tilt
+        )
+        # propagate the 15-minute positions to 1-minute stair-stepped values:
+        tracking_data_1min = tracking_data_15min.reindex(solar_zenith.index,
+                                                         method='ffill')
+        return tracking_data_1min
+
+
+# %%
+# Let's take a look at the tracker rotation curve it produces:
+
+times = pd.date_range('2019-06-01', '2019-06-02', freq='1min', tz='US/Eastern')
+loc = location.Location(40, -80)
+solpos = loc.get_solarposition(times)
+mount = DiscontinuousTrackerMount(axis_azimuth=180, gcr=0.4)
+tracker_data = mount.get_orientation(solpos.apparent_zenith, solpos.azimuth)
+tracker_data['tracker_theta'].plot()
+plt.ylabel('Tracker Rotation [degree]')
+plt.show()
+
+# %%
+# With our custom tracking logic defined, we can create the corresponding
+# Array and PVSystem, and then run a ModelChain as usual:
+
+module_parameters = {'pdc0': 1, 'gamma_pdc': -0.004, 'b': 0.05}
+temp_params = TEMPERATURE_MODEL_PARAMETERS['sapm']['open_rack_glass_polymer']
+array = pvsystem.Array(mount=mount, module_parameters=module_parameters,
+                       temperature_model_parameters=temp_params)
+system = pvsystem.PVSystem(arrays=[array], inverter_parameters={'pdc0': 1})
+mc = modelchain.ModelChain(system, loc, spectral_model='no_loss')
+
+# simple simulated weather, just to show the effect of discrete tracking
+weather = loc.get_clearsky(times)
+weather['temp_air'] = 25
+weather['wind_speed'] = 1
+mc.run_model(weather)
+
+fig, axes = plt.subplots(2, 1, sharex=True)
+mc.results.effective_irradiance.plot(ax=axes[0])
+axes[0].set_ylabel('Effective Irradiance [W/m^2]')
+mc.results.ac.plot(ax=axes[1])
+axes[1].set_ylabel('AC Power')
+fig.show()
+
+# %%
+# The effect of discontinuous tracking creates a "jagged" effect in the
+# simulated plane-of-array irradiance, which then propagates through to
+# the AC power output.

docs/examples/plot_dual_axis_tracking.py

@@ -0,0 +1,44 @@
+"""
+Dual-Axis Tracking
+==================
+
+Example of a custom Mount class.
+"""
+
+# %%
+# Dual-axis trackers can track the sun in two dimensions across the sky dome
+# instead of just one like single-axis trackers.  This example shows how to
+# model a simple dual-axis tracking system using ModelChain with a custom
+# Mount class.
+
+from pvlib import pvsystem, location, modelchain
+import pandas as pd
+import matplotlib.pyplot as plt
+
+# %%
+# New Mount classes should extend ``pvlib.pvsystem.AbstractMount``
+# and must implement a ``get_orientation(solar_zenith, solar_azimuth)`` method:
+
+
+class DualAxisTrackerMount(pvsystem.AbstractMount):
+    def get_orientation(self, solar_zenith, solar_azimuth):
+        # no rotation limits, no backtracking
+        return {'surface_tilt': solar_zenith, 'surface_azimuth': solar_azimuth}
+
+
+loc = location.Location(40, -80)
+array = pvsystem.Array(
+    mount=DualAxisTrackerMount(),
+    module_parameters=dict(pdc0=1, gamma_pdc=-0.004, b=0.05),
+    temperature_model_parameters=dict(a=-3.56, b=-0.075, deltaT=3))
+system = pvsystem.PVSystem(arrays=[array], inverter_parameters=dict(pdc0=3))
+mc = modelchain.ModelChain(system, loc, spectral_model='no_loss')
+
+times = pd.date_range('2019-01-01 06:00', '2019-01-01 18:00', freq='5min',
+                      tz='Etc/GMT+5')
+weather = loc.get_clearsky(times)
+mc.run_model(weather)
+
+mc.results.ac.plot()
+plt.ylabel('Output Power')
+plt.show()

docs/examples/plot_mixed_orientation.py

@@ -0,0 +1,49 @@
+"""
+Mixed Orientation
+=================
+
+Using multiple Arrays in a single PVSystem.
+"""
+
+# %%
+# Residential and Commercial systems often have fixed-tilt arrays
+# installed at different azimuths.  This can be modeled by using
+# multiple :py:class:`~pvlib.pvsystem.Array` objects (one for each
+# orientation) with a single :py:class:`~pvlib.pvsystem.PVSystem` object.
+#
+# This particular example has one east-facing array (azimuth=90) and one
+# west-facing array (azimuth=270), which aside from orientation are identical.
+
+
+from pvlib import pvsystem, modelchain, location
+import pandas as pd
+import matplotlib.pyplot as plt
+
+array_kwargs = dict(
+    module_parameters=dict(pdc0=1, gamma_pdc=-0.004),
+    temperature_model_parameters=dict(a=-3.56, b=-0.075, deltaT=3)
+)
+
+arrays = [
+    pvsystem.Array(pvsystem.FixedMount(30, 270), name='West-Facing Array',
+                   **array_kwargs),
+    pvsystem.Array(pvsystem.FixedMount(30, 90), name='East-Facing Array',
+                   **array_kwargs),
+]
+loc = location.Location(40, -80)
+system = pvsystem.PVSystem(arrays=arrays, inverter_parameters=dict(pdc0=3))
+mc = modelchain.ModelChain(system, loc, aoi_model='physical',
+                           spectral_model='no_loss')
+
+times = pd.date_range('2019-01-01 06:00', '2019-01-01 18:00', freq='5min',
+                      tz='Etc/GMT+5')
+weather = loc.get_clearsky(times)
+mc.run_model(weather)
+
+fig, ax = plt.subplots()
+for array, pdc in zip(system.arrays, mc.results.dc):
+    pdc.plot(label=f'{array.name}')
+mc.results.ac.plot(label='Inverter')
+plt.ylabel('System Output')
+plt.legend()
+plt.show()