As it is currently written, the calc_spectral_mismatch_field() function takes only the module spectral response (sr), the measured spectral solar irradiance (e_sun), and the reference spectrum (e_ref) as inputs. It then truncates the reference spectrum to the wavelength range of the measured spectrum to perform the SMM calculation, like so:
$$\frac{\int^{\lambda_2}_{\lambda_1} E_{sun}(\lambda) SR(\lambda)}{\int^{\lambda_2}_{\lambda_1} E_{ref}(\lambda) SR(\lambda)} \times
\frac{\int^{\lambda_2}_{\lambda_1} E_{ref}(\lambda) }{\int^{\lambda_2}_{\lambda_1} E_{sun}(\lambda)}$$
where $\lambda_1$ and $\lambda_2$ are the wavelength range of the spectral irradiance measurement
I see that there was a discussion here concerning the addition of two more optional inputs, the total irradiance of the measured spectrum (e_sun_tot) and the reference spectrum (e_ref_tot), which would change this calculation to:
$$\frac{\int^{\lambda_2}_{\lambda_1} E_{sun}(\lambda) SR(\lambda)}{\int^{\lambda_2}_{\lambda_1} E_{ref}(\lambda) SR(\lambda)} \times
\frac{ E_{ref,total} }{E_{sun,total}}$$
I'm curious, why wasn't this option included in the end?
As a follow-up question, in a case where we have co-located pyranometer GHI measurements with global spectral irradiance measurements, could the GHI measured by the pyranometer be used to replace $E_{sun,total}$? Is there a strong reason why not to do this if the sensors are time-synchronized and very near each other?
I'm interested because I've found that the long-wavelength absorption of clouds is actually significant for SMM values, and truncating the spectrum in the way that calc_spectral_mismatch_field() currently does would underestimate the SMM for silicon modules under cloudy conditions. I was hoping to use measured pyranometer data to capture this effect instead.
@adriesse, @RDaxini, do you have any comments?
As it is currently written, the
calc_spectral_mismatch_field()function takes only the module spectral response (sr), the measured spectral solar irradiance (e_sun), and the reference spectrum (e_ref) as inputs. It then truncates the reference spectrum to the wavelength range of the measured spectrum to perform the SMM calculation, like so:where$\lambda_1$ and $\lambda_2$ are the wavelength range of the spectral irradiance measurement
I see that there was a discussion here concerning the addition of two more optional inputs, the total irradiance of the measured spectrum (
e_sun_tot) and the reference spectrum (e_ref_tot), which would change this calculation to:I'm curious, why wasn't this option included in the end?
As a follow-up question, in a case where we have co-located pyranometer GHI measurements with global spectral irradiance measurements, could the GHI measured by the pyranometer be used to replace$E_{sun,total}$ ? Is there a strong reason why not to do this if the sensors are time-synchronized and very near each other?
I'm interested because I've found that the long-wavelength absorption of clouds is actually significant for SMM values, and truncating the spectrum in the way that
calc_spectral_mismatch_field()currently does would underestimate the SMM for silicon modules under cloudy conditions. I was hoping to use measured pyranometer data to capture this effect instead.@adriesse, @RDaxini, do you have any comments?