Hi Roberto,
For SAM's Detailed PV model, the
POA from reference cell and
POA from pyranometer options are at the bottom of the Location and Resource page under "Albedo - Sky Diffuse Model - Irradiance Data (Advanced)." When you choose one of these options, SAM assumes that the column of weather data in the weather file with the label "POA" contains irradiance data measured in the plane of the array. This means that the orientation of the pyranometer or reference cell used to make the measurements is the same as the array orientation.
I'm not sure what you mean by "SAM also requires air mass as an input." When you choose the
POA from reference cell option, SAM assumes that the reference cell has the same optical characteristics as cells in the modules of the array, so it removes internal calculations of angle-of-incidence effects. For the
POA from pyranometer option, SAM calculates angle-of-incidence effects by decomposing the POA data into its direct and diffuse components. This is automatically handled by the model, so you do not need to provide any additional inputs.
SAM requires a weather file with one full year's worth of data. You can use the NREL PySAM package for Python to run the Detailed Photovoltaic (Pvsamv1) model with less than one year's worth of data, but this requires writing code in Python and learning how to use the PySAM package. For more about PySAM and coding with SAM in other programming languages, see
sam.nrel.gov/software-development-kit-sdk.html.
Best regards,
Paul.
