references, variable definition, notes section

Author: RDaxini

pvlib/irradiance.py

@@ -850,15 +850,10 @@ def haydavies(surface_tilt, surface_azimuth, dhi, dni, dni_extra,
 def reindl(surface_tilt, surface_azimuth, dhi, dni, ghi, dni_extra,
            solar_zenith, solar_azimuth):
     r'''
-    Determine diffuse irradiance from the sky on a tilted surface using
-    Reindl's 1990 model
-
-    .. math::
-
-       I_{d} = DHI \left(A R_b + (1 - A) \left(\frac{1 + \cos\beta}{2}\right)
-       \left(1 + \sqrt{\frac{I_{hb}}{I_h}} \sin^3(\beta/2)\right) \right)
+    Determine the diffuse irradiance from the sky on a tilted surface using
+    the Reindl (1990) model [1, 2]_.
 
-    Reindl's 1990 model determines the diffuse irradiance from the sky
+    The Reindl model determines the diffuse irradiance from the sky
     (ground reflected irradiance is not included in this algorithm) on a
     tilted surface using the surface tilt angle, surface azimuth angle,
     diffuse horizontal irradiance, direct normal irradiance, global
@@ -904,23 +899,41 @@ def reindl(surface_tilt, surface_azimuth, dhi, dni, ghi, dni_extra,
 
     Notes
     -----
-    The poa_sky_diffuse calculation is generated from the Loutzenhiser et al.
-    (2007) paper, equation 8. Note that I have removed the beam and ground
-    reflectance portion of the equation and this generates ONLY the diffuse
-    radiation from the sky and circumsolar, so the form of the equation
-    varies slightly from equation 8.
+    The Reindl (1990) model for the sky diffuse irradiance, :math:`I_d`, is as
+    follows:
+
+    .. math::
+
+       I_{d} = DHI \left(A \cdot R_b + (1 - A)
+                         \left(\frac{1 + \cos\theta_T}{2}\right)
+       \left(1 + \sqrt{\frac{BHI}{GHI}} \sin^3(\theta_T/2)\right) \right).
+
+    :math:`DHI`, :math:`BHI`, and :math:`GHI` are the diffuse, beam (direct)
+    and global horizontal irradiances, respectively. :math:`A` is the
+    anisotropy index, which is the ratio of the direct normal irradiance to the
+    extraterrestrial irradiation, :math:`R_b` is the projection ratio, which is
+    defined as the cosine of the ratio of angle of incidence (AOI) to the
+    cosine of the zenith angle, and :math:`\theta_T` is the tilt angle of the
+    array.
+
+    The poa_sky_diffuse calculation is generated from Loutzenhiser et al.
+    (2007) [3]_, Equation 8. The beam and ground reflectance portion of the
+    equation have been removed, therefore the model described here generates
+    ONLY the diffuse radiation from the sky and circumsolar, so the form of the
+    equation varies slightly from Equation 8 in [3]_.
 
     References
     ----------
-    .. [1] Loutzenhiser P.G. et. al. "Empirical validation of models to
-       compute solar irradiance on inclined surfaces for building energy
-       simulation" 2007, Solar Energy vol. 81. pp. 254-267
-
-    .. [2] Reindl, D.T., Beckmann, W.A., Duffie, J.A., 1990a. Diffuse
+    .. [1] Reindl, D. T., Beckmann, W. A., Duffie, J. A., 1990a. Diffuse
        fraction correlations. Solar Energy 45(1), 1-7.
-
-    .. [3] Reindl, D.T., Beckmann, W.A., Duffie, J.A., 1990b. Evaluation of
+       :doi:`10.1016/0038-092X(90)90060-P`
+    .. [2] Reindl, D. T., Beckmann, W. A., Duffie, J. A., 1990b. Evaluation of
        hourly tilted surface radiation models. Solar Energy 45(1), 9-17.
+       :doi:'10.1016/0038-092X(90)90061-G'
+    .. [3] Loutzenhiser P. G. et. al. "Empirical validation of models to
+       compute solar irradiance on inclined surfaces for building energy
+       simulation" 2007, Solar Energy vol. 81. pp. 254-267
+       :doi:'10.1016/j.solener.2006.03.009'
     '''
 
     cos_tt = aoi_projection(surface_tilt, surface_azimuth,