I’m calculating the annual irradiance using the HB IRR tool, and also PV production using the PVWatts tool. When using the IWEC weather file, I get normal results. The amount of irradiance/PV production is somewhat similar for East and West.
However, when I use an EPW file downloaded from PVGis ( JRC Photovoltaic Geographical Information System (PVGIS) - European Commission (europa.eu), I get unexpected results. The overall amount of radiance and the overall amount of kWh matches the values I get when calculating in PVgis directly. It also matches the values of someone who’s using different software with the same weather file.
However, the irradiance and kWh differs greatly when I compare East vs West. Also, the monthly values don’t match the values I get when calculating it using different software. E.g. right is what it should look like, left is what I get when using the HB/LB tools. I get these strange results with both the HB IRR tool, as well as the PVWatts tool.
I’ve gone over the epw file in detail, tried to find anomalies, but nothing. All the values match the ones used in the other software. Other software calculates it correctly, it’s only with HB/LB that I get these strange results. There seems to be some kind of shift. Maybe it’s a time zone issue? Or is it because there are no values for the illuminance and sky cover parameters? Has anyone else had these issues?