Replace pvfactors with solarfactors (#1797)

* try out solarfactors

* use solarfactosr in conda env files too

* docs and whatsnew

* More documentation

* reword for clarity; add a bit of "why"

Author: kandersolar

ci/requirements-py3.10.yml

@@ -25,4 +25,4 @@ dependencies:
     - statsmodels
     - pip:
         - nrel-pysam>=2.0
-        - pvfactors==1.5.2
+        - solarfactors

ci/requirements-py3.11.yml

@@ -25,4 +25,4 @@ dependencies:
     - statsmodels
     - pip:
         - nrel-pysam>=2.0
-        - pvfactors==1.5.2
+        - solarfactors

ci/requirements-py3.7.yml

@@ -25,4 +25,4 @@ dependencies:
     - statsmodels
     - pip:
         - nrel-pysam>=2.0
-        - pvfactors==1.5.2
+        - solarfactors

ci/requirements-py3.8.yml

@@ -25,4 +25,4 @@ dependencies:
     - statsmodels
     - pip:
         - nrel-pysam>=2.0
-        - pvfactors==1.5.2
+        - solarfactors

ci/requirements-py3.9.yml

@@ -25,4 +25,4 @@ dependencies:
     - statsmodels
     - pip:
         - nrel-pysam>=2.0
-        - pvfactors==1.5.2
+        - solarfactors

docs/examples/bifacial/plot_bifi_model_mc.py

@@ -18,6 +18,13 @@
 #
 # Future versions of pvlib may make it easier to do bifacial modeling
 # with ``ModelChain``.
+#
+# .. attention::
+#    To run this example, the ``solarfactors`` package (an implementation
+#    of the pvfactors model) must be installed.  It can be installed with
+#    either ``pip install solarfactors`` or ``pip install pvlib[optional]``,
+#    which installs all of pvlib's optional dependencies.
+
 
 import pandas as pd
 from pvlib import pvsystem

docs/examples/bifacial/plot_bifi_model_pvwatts.py

@@ -10,6 +10,12 @@
 # :py:func:`pvlib.pvsystem.pvwatts_dc` with the
 # :py:func:`pvlib.bifacial.pvfactors.pvfactors_timeseries` function to
 # transpose GHI data to both front and rear Plane of Array (POA) irradiance.
+#
+# .. attention::
+#    To run this example, the ``solarfactors`` package (an implementation
+#    of the pvfactors model) must be installed.  It can be installed with
+#    either ``pip install solarfactors`` or ``pip install pvlib[optional]``,
+#    which installs all of pvlib's optional dependencies.
 
 import pandas as pd
 from pvlib import location

docs/examples/bifacial/plot_pvfactors_fixed_tilt.py

@@ -11,6 +11,12 @@
 # fixed-tilt systems correctly.
 # This example shows how to model rear-side irradiance on a fixed-tilt
 # array using :py:func:`pvlib.bifacial.pvfactors.pvfactors_timeseries`.
+#
+# .. attention::
+#    To run this example, the ``solarfactors`` package (an implementation
+#    of the pvfactors model) must be installed.  It can be installed with
+#    either ``pip install solarfactors`` or ``pip install pvlib[optional]``,
+#    which installs all of pvlib's optional dependencies.
 
 import pandas as pd
 from pvlib import location

docs/sphinx/source/conf.py

@@ -297,7 +297,8 @@ def setup(app):
     'pull': ('https://github.com/pvlib/pvlib-python/pull/%s', 'GH'),
     'wiki': ('https://github.com/pvlib/pvlib-python/wiki/%s', 'wiki '),
     'doi': ('http://dx.doi.org/%s', 'DOI: '),
-    'ghuser': ('https://github.com/%s', '@')
+    'ghuser': ('https://github.com/%s', '@'),
+    'discuss': ('https://github.com/pvlib/pvlib-python/discussions/%s', 'GH'),
 }
 
 # -- Options for manual page output ---------------------------------------

docs/sphinx/source/user_guide/bifacial.rst

@@ -15,7 +15,7 @@ surfaces.
 pvlib-python provides two groups of functions for estimating front and back
 irradiance:
 
-1. a wrapper for convenient use of the pvfactors package:
+1. a wrapper for convenient use of the pvfactors model:
 :py:func:`~pvlib.bifacial.pvfactors.pvfactors_timeseries`
 
 2. the infinite sheds bifacial model:
@@ -26,12 +26,25 @@ irradiance:
 pvfactors
 ---------
 
-The `pvfactors <https://sunpower.github.io/pvfactors/>`_ package calculates
+The pvfactors model calculates
 incident irradiance on the front and back surfaces of an array. pvfactors uses
 a 2D geometry which assumes that the array is made up of long, regular rows.
 Irradiance is calculated in the middle of a row; end-of-row effects are not
 included. pvfactors can model arrays in fixed racking or on single-axis
-trackers.
+trackers with a user-configurable number of rows.
+
+Prior to pvlib version 0.10.1, pvlib used the original SunPower implementation
+of the model via the `pvfactors <https://github.com/sunpower/pvfactors>`_
+package.  Starting in version 0.10.1, pvlib instead uses
+`solarfactors <https://github.com/pvlib/solarfactors>`_, a drop-in
+replacement implementation maintained by the pvlib community.
+This switch was made when the original ``pvfactors`` package became
+difficult to install in modern python environments.
+``solarfactors`` implements the same model as ``pvfactors`` and is kept
+up to date and working over time.  Note that "solarfactors" is only the name
+on PyPI (meaning it is installed via ``pip install solarfactors``);
+after installation, Python code still accesses it as "pvfactors"
+(e.g. ``import pvfactors``).
 
 
 Infinite Sheds