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Is PVsyst using the DNI data present for example in the TMY3 files ?

André Mermoud

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The global irradiance is always a sum of the Beam, Diffuse, and Albedo components.

With meteo data (on horizontal plane) there is no albedo of course, as the horizontal plane doesn't "see" the surrounding ground; therefore GlobH = BeamH + DiffH.

If the global and DNI are available in the data, but not the diffuse, PVsyst calculates the corresponding Diffuse component from these data, and at execution the specified DNI will be restituted.

Now if Diffuse and Beam (horizontal or DNI) are both specified in a dataset, there is a redundancy.

The DNI can be deduced from the GlobH and DiffH (it is a definition, using the solar geometry, and doesn't imply any physical model).

If there is a discrepancy with the DNI given in the file, it is an inconsitancy in the data, and PVsyst has no mean for managing this of course.

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