retrieve poa data with iotools get_pvgis_tmy

[ClemensReichel]

Is it possible to retrieve poa Data with get_pvgis_tmy or any other io tool?

[AdamRJensen]

The pvlib.iotools.get_pvgis_hourly returns poa data.

[AdamRJensen]

Otherwise, you can use any of the many transposition models (e.g. Perez or Hay Davies) to calculate possible from dni and dhi.

[ClemensReichel]

Thank you. But the TMY data doesn't come as poa, am I right? I didn't know about transposition models. How do they work?

[kandersolar]

The pvlib function pvlib.irradiance.get_total_irradiance is the primary means of estimating POA irradiance from DNI and DHI: https://pvlib-python.readthedocs.io/en/stable/reference/generated/pvlib.irradiance.get_total_irradiance.html

Here are some examples of calculating POA irradiance with pvlib: https://pvlib-python.readthedocs.io/en/stable/gallery/index.html#irradiance-transposition

For information about transposition models in general, this section of the PVPMC website may be helpful (check the sub-pages in the left sidebar as well): https://pvpmc.sandia.gov/modeling-guide/1-weather-design-inputs/plane-of-array-poa-irradiance/

[ClemensReichel]

Thank you! Is there a way to contact you? I am struggling quite hard with an apparently easy calculation, which has worked before:

aoi = pvlib.irradiance.aoi(
    surface_tilt, surface_azimuth, solarpos.apparent_zenith, solarpos.azimuth)

iam = pvlib.iam.ashrae(aoi)

effective_irradiance = poa_data["poa_direct"] * iam + poa_data["poa_diffuse"]

temp_cell = pvlib.temperature.faiman(poa_data["poa_global"], poa_data["temp_air"], poa_data["wind_speed"])

The main problem is, that the effective irradiance only returns NaN and I despair of it

[kandersolar]

This forum is appropriate to work through such issues :)

To resolve your issue, I suggest moving backwards through your code and examining each variable sequentially to identify which calculation step is introducing the NaN. For example, is the aoi NaN too?

[ClemensReichel]

Yes, I have checked that. But all the other variables contain valid data.
The only thing that I have noticed is that the return from the effective_irradiance has 17520 lines of NaN, while all other have the expected 8760 values for every hour per year.

[cwhanse]

aoi and poa_data likely have different indexes.