Custom Imported Meteo File

[yildizipekci]

Hello, I wanted to create a custom imported meteo file for a location in Germany for 2025. The real data is available from Jan, 2025 until today. As I import the weather data I get an error due to clearness index of best days is way too low with respect to celar day model. Is it because PVsyst’s clear-sky model expects the year to include summer months (June–August), when irradiance and clearness index are highest. If my dataset ends in May, PVsyst looks for the “best” days in spring or winter — which naturally have lower solar angles and less irradiance, even on clear days. So even the  “best” days don't look clear enough compared to what they should be. Or can it be due to a different issue? For the same location I could create custom imported files from 1993-2024 so only 2025 gives the error. Thanks a lot in advance! 

[Linda Thoren]

Hello,

The clearness index will be evaluated and compared with the clear day model for the same time period. Thus having only a few months of data will not be an issue. If you compare the data for 2025 with data for 2024, are they similar or are indeed the values for 2025 much lower?