DIRINT and changing decomp. model

[Cole Noble]

I am importing GHI into PVsyst and need to rely on the decomposition model for DHI. 

From what I understand, PVsyst uses the DIRINT model (Perez-based) for decomposition and then uses a Meteonorm algorithm for creating the synthetic (hourly) data. 

This would explain why "Diffuse Perez, Meteonorm" shows up on my reports (even if I am not using any Meteonorm-related irradiation). 

1. Is my understanding correct? 

2. If my understanding is correct, if I am importing hourly GHI data, why would the Meteonorm synthetic model still be used? The GHI data is at an hourly granularity already; why not just use DIRINT? Perhaps PVsyst uses the label "Perez, Meteonorm" for DIRINT? Even if no synthetic hourly data is created? 

3. I don't see a way of changing the decomposition model in PVsyst to Erbs instead of DIRINT. Is this not possible? 

Thanks!

Cole 

[Michele Oliosi]

Hi @Cole Noble,

If you import hourly GHI data into PVsyst meteonorm or DirInt are not used for DHI. Instead, the Erbs model is used.
However, the meteonorm generation is likely used for the ambient temperature if it is not present in your data?

[Cole Noble]

Thanks, Michele, for your response. So strangely, I am importing both houlry GHI and temperature, in which case I woulnd't expect, "Perez, Meteonorm" to show up under the models used in the PVsyst report, but rather, "Erbs". Do you have any ideas on why this might be the case? Thanks!