pvpltools.iec61853.calc_spectral_factor

pvpltools.iec61853.calc_spectral_factor(banded_irradiance, banded_responsivity, integration_limit=None)

Calculate the spectral correction/mismatch factor(s) for the given spectral irradiance and device responsivity.

Parameters:

• banded_irradiance (1-D or 2-D array_like) – Spectral irradiance integrated in 29 bands [W/m²].

• banded_responsivity (1-D array_like) – Spectral responsivity averaged in 29 bands [unitless].

• integration_limit (integer or None, default None) –

  Last spectral band to use for the integrals in the spectral mismatch calculation. When None is specified, the banded_irradiance is integrated over the full available range (29 bands) and the value 1000 W/m² is used for the integrated reference spectrum.

  See Notes section below for further information.

Raises:

ValueError – If the number of bands in the arguments is incorrect.

Returns:

The calculated spectral correction factors [unitless].

Return type:

scalar or 1-D array

See also

SPECTRAL_BAND_EDGES, BANDED_AM15G, convert_to_banded

Notes

The calculation method used here does not correspond precisely to the description in IEC 61853-3 [1] because the latter has inconsistencies. In particular:

• The standard specifies the limits of 300 and 4000 nm for integration.

• But the outer edges of the spectral bands in the standard climate profile data are 306.8 and 4605.65 nm, and there is no band edge at 4000 nm; therefore, it is not possible to integrate using the specified limits.

• The broadband reference irradiance in eq. 6 of [1] is 1000 W/m².

• This implies integration limits of 280 nm and infinity for AM15G.

• The broadband irradiance in the climate profiles (also used in eq. 6) is equal to the sum of the all 29 spectral irradiance bands.

• This implies an integration from 306.8 to 4605.65 nm.

In this function the lower integration limit is fixed at the band edge 306.8 nm. The integral of AM15G over the range 280-306.8 nm is 0.066 W/m², therefore this choice does not significantly affect the spectral factor.

The upper integration limit is more relevant since the integral of AM15G from 4000 nm to infinity is 2.53 W/m².

Using the default option, integration_limit=None, eq. 6 is taken at face value and the implied integration limits are used. This is equivalent to the recommendation in [2].

It is also possible to set the integration_limit to a specific band number, which is then used as upper limit for all four integrals in the mismatch calculation.

References

[1] (1,2)

“IEC 61853-3 Photovoltaic (PV) module performance testing and energy rating - Part 3: Energy rating of PV modules”. IEC, Geneva, 2018.

[2]

M.Vogt et al “PV module energy rating standard IEC 61853‐3 intercomparison and best practice guidelines for implementation and validation”, submitted for publication, 2021.

Author: Anton Driesse, PV Performance Labs