developer_bh

Dear hom, thanks for reaching out to us. Does the monthly distirbution of global irradiation values look similiar to your chart for this PVGIS-location (You can see it via MeteoSyn > Details with the latest PVSOL) ? Sometimes there are missing timeperiods in the data, so I'd recommend to check your climate-data-file in MeteoSyn for missing periods, f.e. days with no global radiation at all. If yes and no missing timeperiods: As Mikio already pointed out there can be some irregularities in PVGIS data. These mainly regard temperature data on locations near the coast . In PVGIS 5.1 and older (called PVGIS-SARAH/ERA-Interim" in the source) there can be some more problems regarding the distribution of the global-irradiation data over the day. However your problem does not look like one of these factors. It might be a problem with the satellite-rawdata which is collected to generate a typical meteorological year. It is hard to reconstruct at this point why April is higher than May and June, we don't have the raw data from PVGIS. If you want to investigate yourself you may have a look at https://re.jrc.ec.europa.eu/pvg_tools/en/ . For now I'd recommend using another climate source for your area. Best regards, Ben

Hello Asger, thank you for your answer! PVGIS 5.1 has a timerange from 2005 to 2016 and is called "PVGIS-SARAH/ERA-Interim" in the source. PVGIS 5.2 has a timerange from 2005 to 2020 and is called "PVGIS-SARAH2/ERA5" in the source. So your file is PVGIS 5.2. That means that my first theory of wrong data towards the day-end does not apply here. The daily course of irradiation data for Slagelse looks plausible : It would be helpful at this point to have a deeper look into your project. You may send it to me via PN if you wish. Best regards, Ben

Hello Asger, thank you for your feedback and for taking the time to report this anomaly in the climate data to us! I agree with you that a higher value of Southwest values compared to South values lowers the confidence in the climate file. I am guessing that you are using a PVGIS file version 5.1 or earlier? Specifically, your problem is most likely an unnatural distribution of global radiation values towards the end of the day (sunset), which is why the southwest orientation has elevated values. PVGIS is aware of the problem and claims to have solved it with version 5.2. In the following graph you can see such an unnatural peak at the end of the day. If you could send me your climate file I could investigate the problem further, which would be very helpful in proving the thesis and taking preventive measures if necessary. You can send me the file via PN or upload it in this thread. Until further clarification, I would recommend that you use alternative climate data for this location, for example from Meteonorm. Best regards, Ben