Hi Anton,
No, these are different values.
The "G" with no subscript in Equation 7.8 is the total global horizontal irradiance on the surface of the module cover that SAM reports in the results as "Irradiance GHI calculated." It is reported for the user's reference: The module model uses the beam and diffuse components rather than the global horizontal irradiance as input to the module model.
The "G" with a "0" subscript in Equation 10.25 is the irradiance absorbed by the photovoltaic cell as calculated in Equation 10.20.
The "G" without the subscript in Equation 10.25 is the effective transmitted irradiance, so is different from the "G" in Equation 7.8.
Best regards,
Paul.
