Why is the Global incident in coll. plane in Loss Diagram different between Meteonorm and PVGIS?

[Pakamas Teerasuwannajak]

Hello,

I have a question regarding the global incident in the collector plane loss diagram, where I noticed approximately a 2% difference between Meteonorm and PVGIS (due to the different meteorological databases). The same assumptions were applied in this project.

Could you please clarify the possible causes of this difference? Additionally, I would appreciate your recommendation on which meteorological database is most commonly used in practice.

Thank you for your support.

[Linda Thoren]

Hello,

The differences in the databases will be in the global horizontal irradiance, and thus only indirectly on the global incident in collector plane. To calculate the Global incident in the collector plane, the same transposition method can be used for any source of weather data. The difference in direct and diffuse irradiance for instance can have a large impact in the incident in the collector plane. You can read mora about the transposition model in the following help page:
https://www.pvsyst.com/help/physical-models-used/irradiation-models/transposition-model.html

Indeed, there can be large differences in the weather data and it is difficult to evaluate which one is the most accurate at a specific site. We have done some comparisons that you find in the following help page:
https://www.pvsyst.com/help/meteo-database/import-meteo-data/data-source-comparison.html?h=weather+data