pvlib.spectrum.spectral_factor_firstsolar#
- pvlib.spectrum.spectral_factor_firstsolar(precipitable_water, airmass_absolute, module_type=None, coefficients=None, min_precipitable_water=0.1, max_precipitable_water=8, min_airmass_absolute=0.58, max_airmass_absolute=10)[source]#
Spectral mismatch modifier based on precipitable water and absolute (pressure-adjusted) air mass.
Estimates the spectral mismatch modifier, \(M\), representing the effect of variation in the spectral irradiance on the module short circuit current \(M\) is estimated from absolute (pressure-corrected) air mass, \(AM_a\), and precipitable water, \(Pw\).
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 Pw where:
\(0.5 \textrm{cm} <= Pw <= 5 \textrm{cm}\)
\(1.0 <= AM_a <= 5.0\)
Spectral range is limited to that of CMP11 (280 nm to 2800 nm)
Spectrum simulated on an equatorial facing surface with 37° tilt
All other parameters fixed at G173 standard
From these simulated spectra, \(M\) is calculated using the known quantum efficiency curves. Multiple linear regression is then applied to fit Eq. 1 to determine the coefficients for each module. More details on the model can be found in [2].
- Parameters:
precipitable_water (numeric) – atmospheric precipitable water. [cm]
airmass_absolute (numeric) – absolute (pressure-adjusted) air mass. [unitless]
module_type (str, optional) –
a string specifying a cell type. Values of ‘cdte’, ‘monosi’, ‘xsi’, ‘multisi’, and ‘polysi’ (can be lower or upper case). If provided, module_type selects default coefficients for the following modules:
'cdte'- First Solar Series 4-2 CdTe module.'monosi','xsi'- First Solar TetraSun module.'multisi','polysi'- anonymous multi-crystalline silicon module.'cigs'- anonymous copper indium gallium selenide module.'asi'- anonymous amorphous silicon module.
The module used to calculate the spectral correction coefficients corresponds to the Multi-crystalline silicon Manufacturer 2 Model C from [3]. The spectral response (SR) of CIGS and a-Si modules used to derive coefficients can be found in [4]
coefficients (array-like, optional) – Allows for entry of user-defined spectral correction coefficients. Coefficients must be of length 6. Derivation of coefficients requires use of SMARTS and PV module quantum efficiency curve. Useful for modeling PV module types which are not included as defaults, or to fine tune the spectral correction to a particular PV module. Note that the parameters for modules with very similar quantum efficiency should be similar, in most cases limiting the need for module specific coefficients.
min_precipitable_water (float, default 0.1) – minimum atmospheric precipitable water. Any
precipitable_watervalue lower thanmin_precipitable_wateris set tomin_precipitable_water. [cm]max_precipitable_water (float, default 8) – maximum atmospheric precipitable water. Any
precipitable_watervalue greater thanmax_precipitable_wateris set tonp.nan. [cm]min_airmass_absolute (float, default 0.58) – minimum absolute airmass. Any
airmass_absolutevalue lower thanmin_airmass_absoluteis set tomin_airmass_absolute. [unitless]max_airmass_absolute (float, default 10) – minimum absolute airmass. Any
airmass_absolutevalue greater thanmax_airmass_absoluteis set tomax_airmass_absolute. [unitless]
- Returns:
modifier (array-like) – spectral mismatch factor (unitless) which can be multiplied with broadband irradiance reaching a module’s cells to estimate effective irradiance, i.e., the irradiance that is converted to electrical current.
Notes
The
spectral_factor_firstsolarmodel takes the following form:\[M = c_1 + c_2 AM_a + c_3 Pw + c_4 AM_a^{0.5} + c_5 Pw^{0.5} + c_6 \frac{AM_a} {Pw^{0.5}}.\]The default values for the limits applied to \(AM_a\) and \(Pw\) via the
min_precipitable_water,max_precipitable_water,min_airmass_absolute, andmax_airmass_absoluteare set to prevent divergence of the model presented above. These default values were determined by the publication authors in the original pvlib-python implementation (GH208).References
