add get_aoi, dni/am calcs

wholmgren · wholmgren · commit c541abd4957f · 2016-01-30T12:14:30.000-07:00
diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
@@ -19,7 +19,7 @@
 
 from pvlib import tools
 from pvlib.location import Location
-from pvlib import irradiance
+from pvlib import irradiance, atmosphere
 
 
 # not sure if this belongs in the pvsystem module.
@@ -99,7 +99,7 @@ def __init__(self,
                  module=None, module_parameters=None,
                  series_modules=None, parallel_modules=None,
                  inverter=None, inverter_parameters=None,
-                 racking_model=None,
+                 racking_model='open_rack_cell_glassback',
                  **kwargs):
         
         self.surface_tilt = surface_tilt
@@ -128,6 +128,27 @@ def __init__(self,
         super(PVSystem, self).__init__(**kwargs)
 
 
+    def get_aoi(self, solar_zenith, solar_azimuth):
+        """Get the angle of incidence on the system.
+        
+        Parameters
+        ----------
+        solar_zenith : float or Series.
+            Solar zenith angle.
+        solar_azimuth : float or Series.
+            Solar azimuth angle.
+            
+        Returns
+        -------
+        aoi : Series
+            The angle of incidence
+        """
+        
+        aoi = irradiance.aoi(self.surface_tilt, self.surface_azimuth,
+                             solar_zenith, solar_azimuth)
+        return aoi
+    
+    
     def get_irradiance(self, solar_zenith, solar_azimuth, dni, ghi, dhi,
                        dni_extra=None, airmass=None, model='isotropic',
                        **kwargs):
@@ -166,6 +187,14 @@ def get_irradiance(self, solar_zenith, solar_azimuth, dni, ghi, dhi,
             Column names are: ``total, beam, sky, ground``.
         """
 
+        # not needed for all models, but this is easier
+        if dni_extra is None:
+            dni_extra = irradiance.extraradiation(solar_zenith.index)
+            dni_extra = pd.Series(dni_extra, index=solar_zenith.index)
+
+        if airmass is None:
+            airmass = atmosphere.relativeairmass(solar_zenith)
+
         return irradiance.total_irrad(self.surface_tilt,
                                       self.surface_azimuth,
                                       solar_zenith, solar_azimuth,
