Correct infinite_sheds view factor from row to sky and ground; expose vf functions in bifacial.utils (#1666)

* correct view factor from row to sky and ground

* update latex math in vf_row_gnd

* revise vf_row_sky and test

* remake tests for vf_row_ground

* fix my mistakes

* fix row_ground_integ

* new vf functions in utils

* stickler

* use functions from utils

* documents

* revise whatsnew

* add technical document

* doc edits

* move fns to utils

* more fcn shuffling

* update docs

* reorder arguments

* docstring edits

* add defaults to _integ functions

* fix whatsnew formatting issues

---------

Co-authored-by: Hansen <cwhanse>
Co-authored-by: Cliff Hansen <cwhanse@sandia.gov>
Co-authored-by: Kevin Anderson <kevin.anderso@gmail.com>

Author: 3 people

docs/notes/Determining the average view factor from a module.pdf

@@ -11,3 +11,15 @@ Functions for calculating front and back surface irradiance
    bifacial.pvfactors.pvfactors_timeseries
    bifacial.infinite_sheds.get_irradiance
    bifacial.infinite_sheds.get_irradiance_poa
+
+Utility functions for bifacial modeling
+
+.. autosummary::
+   :toctree: generated/
+	
+   bifacial.utils.vf_row_sky_2d
+   bifacial.utils.vf_row_sky_2d_integ
+   bifacial.utils.vf_row_ground_2d
+   bifacial.utils.vf_row_ground_2d_integ
+   bifacial.utils.vf_ground_sky_2d
+   bifacial.utils.vf_ground_sky_2d_integ

docs/sphinx/source/reference/bifacial.rst

@@ -6,6 +6,7 @@ Shading
 .. autosummary::
    :toctree: ../generated/
 
+   shading.ground_angle
    shading.masking_angle
    shading.masking_angle_passias
    shading.sky_diffuse_passias

docs/sphinx/source/reference/effects_on_pv_system_output/shading.rst

@@ -52,6 +52,16 @@ Deprecations
 
 Enhancements
 ~~~~~~~~~~~~
+* Exposes several functions useful for bifacial and shading calculations (:pull:`1666`):
+
+  * :py:func:`pvlib.bifacial.utils.vf_row_sky_2d`
+  * :py:func:`pvlib.bifacial.utils.vf_row_sky_2d_integ`
+  * :py:func:`pvlib.bifacial.utils.vf_row_ground_2d`
+  * :py:func:`pvlib.bifacial.utils.vf_row_ground_2d_integ`
+  * :py:func:`pvlib.bifacial.utils.vf_ground_sky_2d`
+  * :py:func:`pvlib.bifacial.utils.vf_ground_sky_2d_integ`
+  * :py:func:`pvlib.shading.ground_angle`
+
 * Added a function :py:func:`pvlib.spectrum.spectral_factor_caballero`
   to estimate spectral mismatch modifiers from atmospheric conditions. (:pull:`1296`)
 * Added a new irradiance decomposition model :py:func:`pvlib.irradiance.louche`. (:pull:`1705`)
@@ -72,6 +82,11 @@ Enhancements
 
 Bug fixes
 ~~~~~~~~~
+* Corrects an error in view factor calculations which are part of
+  :py:func:`pvlib.bifacial.infinite_sheds.get_irradiance`. The error
+  affects rear surface irradiance by a few W/m2. As part of the correction,
+  average view factors are now computed by exact formulas rather than by
+  numerical integration. (:issue:`1665`, :pull:`1666`)
 * `data` can no longer be left unspecified in
   :py:meth:`pvlib.modelchain.ModelChain.run_model_from_effective_irradiance`. (:issue:`1713`, :pull:`1720`)
 * ``d2mutau`` and ``NsVbi`` were hardcoded in :py:func:`pvlib.pvsystem.max_power_point` instead of
@@ -103,6 +118,8 @@ Requirements
 
 Contributors
 ~~~~~~~~~~~~
+* Mark Mikofski (:ghuser:`mikofski`)
+* Cliff Hansen (:ghuser:`cwhanse`)
 * Lakshya Garg (:ghuser:`Lakshyadevelops`)
 * Adam R. Jensen (:ghuser:`adamrjensen`)
 * Ben Pierce (:ghuser:`bgpierc`)