describe racking model choices for SAPM temperature models

Author: cwhanse

pvlib/pvsystem.py

@@ -170,9 +170,11 @@ class PVSystem:
     inverter_parameters : dict or Series, optional
         Inverter parameters as defined by the SAPM, CEC, or other.
 
-    racking_model : string, default 'open_rack'
-        Valid strings are 'open_rack', 'close_mount', and 'insulated_back'.
-        Used to identify a parameter set for the SAPM cell temperature model.
+    racking_model : string, optional
+        Valid strings are ``'open_rack'``, ``'close_mount'``, and
+        ``'insulated_back'``. Used to identify a parameter set for the SAPM
+        cell temperature model. See :py:func:`pvlib.temperature.sapm_module`
+        for definitions.
 
     losses_parameters : dict or Series, optional
         Losses parameters as defined by PVWatts or other.
@@ -1395,8 +1397,10 @@ class FixedMount(AbstractMount):
         West=270. [degrees]
 
     racking_model : str, optional
-        Valid strings are 'open_rack', 'close_mount', and 'insulated_back'.
-        Used to identify a parameter set for the SAPM cell temperature model.
+        Valid strings are ``'open_rack'``, ``'close_mount'``, and
+        ``'insulated_back'``. Used to identify a parameter set for the SAPM
+        cell temperature model. See :py:func:`pvlib.temperature.sapm_module`
+        for definitions.
 
     module_height : float, optional
        The height above ground of the center of the module [m]. Used for
@@ -1472,8 +1476,11 @@ class SingleAxisTrackerMount(AbstractMount):
         `cross_axis_tilt`. [degrees]
 
     racking_model : str, optional
-        Valid strings are 'open_rack', 'close_mount', and 'insulated_back'.
-        Used to identify a parameter set for the SAPM cell temperature model.
+        Valid strings are ``'open_rack'``, ``'close_mount'``, and
+        ``'insulated_back'`. Used to identify a parameter set for the SAPM
+        cell temperature model. ``'open_rack'`` should be used for systems
+        with single-axis trackers. See :py:func:`pvlib.temperature.sapm_module`
+        for definitions.
 
     module_height : float, optional
        The height above ground of the center of the module [m]. Used for

pvlib/temperature.py

@@ -125,6 +125,18 @@ def sapm_cell(poa_global, temp_air, wind_speed, a, b, deltaT,
     | glass/polymer | insulated back | -2.81 | -0.0455 | 0                   |
     +---------------+----------------+-------+---------+---------------------+
 
+    Mounting cases can be described in terms of air flow across and around the
+    rear-facing surface of the module:
+        
+    * "open rack" refers to mounting that allows relatively free air flow.
+      This case is typical of ground-mounted systems on fixed racking or
+      single axis trackers.
+    * "close roof" refers to limited or restricted air flow. This case is
+      typical of roof-mounted systems with some gap behind the module.
+    * "insulated back" refers to systems with no air flow contacting the rear
+      surface of the module. This case is typical of building-integrated PV
+      systems, or systems laid flat on a ground surface.
+
     References
     ----------
     .. [1] King, D. et al, 2004, "Sandia Photovoltaic Array Performance
@@ -206,6 +218,18 @@ def sapm_module(poa_global, temp_air, wind_speed, a, b):
     | glass/polymer | insulated back | -2.81 | -0.0455 | 0                   |
     +---------------+----------------+-------+---------+---------------------+
 
+    Mounting cases can be described in terms of air flow across and around the
+    rear-facing surface of the module:
+        
+    * "open rack" refers to mounting that allows relatively free air flow.
+      This case is typical of ground-mounted systems on fixed racking or
+      single axis trackers.
+    * "close roof" refers to limited or restricted air flow. This case is
+      typical of roof-mounted systems with some gap behind the module.
+    * "insulated back" refers to systems with no air flow contacting the rear
+      surface of the module. This case is typical of building-integrated PV
+      systems, or systems laid flat on a ground surface.
+
     References
     ----------
     .. [1] King, D. et al, 2004, "Sandia Photovoltaic Array Performance