Merge pull request #3 from MLEEFS/new_spectral

Updates from First Solar to the spectral correction function.

Author: DanRiley

pvl_FSspeccorr.m

@@ -14,15 +14,15 @@
 %   precipitable water, Pwat, using the following function:
 %
 %   M = coeff(1) + coeff(2)*AMa  + coeff(3)*Pwat  + coeff(4)*AMa.^.5  
-%           + coeff(5)*Pwat.^.5 + coeff(6)*AMa./Pwat                    (1) 
+%           + coeff(5)*Pwat.^.5 + coeff(6)*AMa./Pwat.^0.5         (1) 
 %
 %   Default coefficients are determined for several cell types with 
 %   known quantum efficiency curves, by using the Simple Model of the 
 %   Atmospheric Radiative Transfer of Sunshine (SMARTS) [1]. 
 %   Using SMARTS, spectrums are simulated with all combinations of AMa 
 %   and Pwat where:
-%       *   0.5 cm <= Pwat <= 5 cm
-%       *   0.8 <= AMa <= 4.75 (Pressure of 800 mbar and 1.01 <= AM <= 6)
+%       *   0.1 cm <= Pwat <= 5 cm
+%       *   1.0 <= AMa <= 5 
 %       *   Spectral range is limited to that of CMP11 (280 nm to 2800 nm)
 %       *   spectrum simulated on a plane normal to the sun
 %       *   All other parameters fixed at G173 standard
@@ -31,7 +31,8 @@
 %   Eq. 1 to determine the coefficients for each module.
 %
 %  Function pvl_FSspeccorr was developed by Mitchell Lee and Alex Panchula,
-%   at First Solar, 2015.
+%   at First Solar, 2015. Detailed description of spectral correction 
+%   can be found in [2] 
 %
 % Inputs:
 %   Pwat - atmospheric precipitable water (cm). Can be
@@ -47,7 +48,7 @@
 %           'multisi','polysi' - coefficients for multi-crystalline silicon 
 %               modules. The module used to calculate the spectral
 %               correction coefficients corresponds to the Mult-crystalline 
-%               silicon Manufacturer 2 Model C from [2].
+%               silicon Manufacturer 2 Model C from [3].
 %   custCoeff - allows for entry of user defined spectral correction
 %       coefficients. Coefficients must be entered as a numeric row or 
 %       column vector of length 6. Derivation of coefficients requires use 
@@ -69,12 +70,57 @@
 % [1]   Gueymard, Christian. SMARTS2: a simple model of the atmospheric 
 %           radiative transfer of sunshine: algorithms and performance 
 %           assessment. Cocoa, FL: Florida Solar Energy Center, 1995.
-% [2]   Marion, William F., et al. User's Manual for Data for Validating 
+% [2]   Lee, Mitchell, and Panchula, Alex. "Spectral Correction for
+%           Photovoltaic Module Performance Based on Air Mass and Precipitable 
+%           Water." IEEE Photovoltaic Specialists Conference, Portland, 2016 
+% [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
 
 
 
+% Correct for AMa and Pwat having transposed dimensions 
+if isrow(AMa)
+    AMa = AMa';
+end
+
+if isrow(Pwat)
+    Pwat = Pwat';
+end
+
+% --- Screen Input Data ---
+
+% *** Pwat ***
+% Replace Pwat Values below 0.1 cm with 0.1 cm to prevent model from
+% diverging
+if min(Pwat) < 0.1
+    Pwat(Pwat < 0.1) = 0.1;
+    warning(['Exceptionally low Pwat values replaced with 0.1 cm to prevent',...
+        ' model divergence']);
+end
+
+% Warn user about Pwat data that is exceptionally high
+if max(Pwat) > 8
+    warning(['Exceptionally high Pwat values. Check input data:', ...
+        ' model may diverge in this range']);
+end
+
+% *** AMa ***
+% Replace Extremely High AM with AM 10 to prevent model divergence
+% AM > 10 will only occur very close to sunset
+if max(AMa) > 10 
+  AMa(AMa > 10) = 10;
+end
+
+% Warn user about AMa data that is exceptionally low
+if min(AMa) < 0.58
+   warning(['Exceptionally low air mass: ',...
+       'model not intended for extra-terrestrial use'])
+   % pvl_absoluteairmass(1,pvl_alt2pres(4340)) = 0.58
+   % Elevation of Mina Pirquita, Argentian = 4340 m. Highest elevation city
+   % with population over 50,000.
+end
+
 % If user input is a character array, use appropriate default coefficients.
 if ischar(varargin{1})
     modType = lower(varargin{1});
@@ -84,14 +130,14 @@
             % Coefficients for First Solar Series 4-2 (and later) modules.
             % For modeling the performance of earlier CdTe module series,
             % use the coefficients that are commented out
-            %  [0.7900,	-0.0644, -0.01658,	0.1835, 0.09077, -0.002330];
-            coeff = [0.8752, -0.04588, -0.01559, 0.08751, 0.09158, -0.002295];
+            % [0.79418,-0.049883,-0.013402,0.16766,0.083377,-0.0044007];
+             coeff = [0.86273, -0.038948, -0.012506, 0.098871, 0.084658, -0.0042948];
         case {'monosi','xsi'}
             % Coefficients for First Solar TetraSun Modules
-            coeff = [0.8478, -0.03326, -0.0022953, 0.1565, 0.01566, -0.001712];
+             coeff = [0.85914, -0.020880, -0.0058853, 0.12029, 0.026814, -0.0017810];
         case {'polysi','multisi'}
             % Coefficients for Multi-Si: Manufacturer 2 Model C
-            coeff = [0.83019, -0.04063,	-0.005281,	0.1695,	0.02974, -0.001676];
+            coeff = [0.84090, -0.027539, -0.0079224, 0.13570, 0.038024, -0.0021218];
         otherwise
             error('Incorrect module type for use of default parameters')
     end
@@ -100,16 +146,7 @@
     coeff = varargin{1};
 end
 
-% Correct for AMa and Pwat having transposed dimensions 
-if isrow(AMa)
-    AMa = AMa';
-end
-
-if isrow(Pwat)
-    Pwat = Pwat';
-end
-
 % Evaluate Spectral Shift
-M = coeff(1) + coeff(2)*AMa  + coeff(3)*Pwat  + coeff(4)*AMa.^.5  + coeff(5)*Pwat.^.5 + coeff(6)*AMa./Pwat; 
+M = coeff(1) + coeff(2)*AMa  + coeff(3)*Pwat  + coeff(4)*AMa.^.5  + coeff(5)*Pwat.^.5 + coeff(6)*AMa./Pwat.^0.5; 
 end