Added coefficients for CIGS and a-Si modules types. (#308)

* Added coefficients for CIGS and a-Si modules types. Provided references to document with Spectral Reponses (SRs) of CIGS and a-Si modules. Reference also includes additional testing and field validation of the model.

* Added CIGS and aSi to unit testing.Cleaned up spacing on first_solar_spectral_correction.

* Replaced tab with spaces in the First Solar Spectral Correction Function.

* Added new test results for Cdte, monosi, and polysi, for the function test_first_solar_spectral_correction.

Author: MLEEFS

pvlib/atmosphere.py

@@ -374,10 +374,13 @@ def first_solar_spectral_correction(pw, airmass_absolute, module_type=None,
             * 'cdte' - First Solar Series 4-2 CdTe modules.
             * 'monosi', 'xsi' - First Solar TetraSun modules.
             * 'multisi', 'polysi' - multi-crystalline silicon modules.
+            * 'cigs' - anonymous copper indium gallium selenide PV module
+            * 'asi' - anonymous amorphous silicon PV module
 
         The module used to calculate the spectral correction
         coefficients corresponds to the Mult-crystalline silicon
-        Manufacturer 2 Model C from [3]_.
+        Manufacturer 2 Model C from [3]_. Spectral Response (SR) of CIGS
+        and a-Si modules used to derive coefficients can be found in [4]_ 
 
     coefficients : array-like
         allows for entry of user defined spectral correction
@@ -409,6 +412,10 @@ def first_solar_spectral_correction(pw, airmass_absolute, module_type=None,
     .. [3] Marion, William F., et al. User's Manual for Data for Validating
        Models for PV Module Performance. National Renewable Energy
        Laboratory, 2014. http://www.nrel.gov/docs/fy14osti/61610.pdf
+    .. [4] Schweiger, M. and Hermann, W, Influence of Spectral Effects
+        on Energy Yield of Different PV Modules: Comparison of Pwat and
+        MMF Approach, TUV Rheinland Energy GmbH report 21237296.003,
+        January 2017
     """
 
     # --- Screen Input Data ---
@@ -443,13 +450,17 @@ def first_solar_spectral_correction(pw, airmass_absolute, module_type=None,
 
     _coefficients = {}
     _coefficients['cdte'] = (
-       0.86273, -0.038948, -0.012506, 0.098871, 0.084658, -0.0042948)
+        0.86273, -0.038948, -0.012506, 0.098871, 0.084658, -0.0042948)
     _coefficients['monosi'] = (
         0.85914, -0.020880, -0.0058853, 0.12029, 0.026814, -0.0017810)
     _coefficients['xsi'] = _coefficients['monosi']
     _coefficients['polysi'] = (
         0.84090, -0.027539, -0.0079224, 0.13570, 0.038024, -0.0021218)
     _coefficients['multisi'] = _coefficients['polysi']
+    _coefficients['cigs'] = (
+        0.85252, -0.022314, -0.0047216, 0.13666, 0.013342, -0.0008945)
+    _coefficients['asi'] = (
+        1.12094, -0.047620, -0.0083627, -0.10443, 0.098382,-0.0033818)
 
     if module_type is not None and coefficients is None:
         coefficients = _coefficients[module_type.lower()]

pvlib/test/test_atmosphere.py

@@ -79,17 +79,25 @@ def test_gueymard94_pw():
 
 @pytest.mark.parametrize("module_type,expect", [
     ('cdte', np.array(
-        [[ 0.99134828,  0.97701063,  0.93975103],
-         [ 1.02852847,  1.01874908,  0.98604776],
-         [ 1.04722476,  1.03835703,  1.00656735]])),
+        [[ 0.9905102 ,  0.9764032 ,  0.93975028],
+         [ 1.02928735,  1.01881074,  0.98578821],
+         [ 1.04750335,  1.03814456,  1.00623986]])),
     ('monosi', np.array(
-        [[ 0.9782842 ,  1.02092726,  1.03602157],
-         [ 0.9859024 ,  1.0302268 ,  1.04700244],
-         [ 0.98885429,  1.03351495,  1.05062687]])),
+        [[ 0.9776977 ,  1.02043409,  1.03574032],
+         [ 0.98630905,  1.03055092,  1.04736262],
+         [ 0.98828494,  1.03299036,  1.05026561]])),
     ('polysi', np.array(
-        [[ 0.9774921 ,  1.01757872,  1.02649543],
-         [ 0.98947361,  1.0314545 ,  1.04226547],
-         [ 0.99403107,  1.03639082,  1.04758064]]))
+        [[ 0.9770408 ,  1.01705849,  1.02613202],
+         [ 0.98992828,  1.03173953,  1.04260662],
+         [ 0.99352435,  1.03588785,  1.04730718]])),
+    ('cigs', np.array(
+        [[ 0.9745919 ,  1.02821696,  1.05067895],
+         [ 0.97529378,  1.02967497,  1.05289307],
+         [ 0.97269159,  1.02730558,  1.05075651]])),   
+    ('asi', np.array(
+        [[ 1.0555275 ,  0.87707583,  0.72243772],
+         [ 1.11225204,  0.93665901,  0.78487953],
+         [ 1.14555295,  0.97084011,  0.81994083]]))     
 ])
 def test_first_solar_spectral_correction(module_type, expect):
     ams = np.array([1, 3, 5])