get_total_irradiance vs single_axis_tracker.get_irradiance

[cpullium]

Hey all,
Just started using pvlib for the first time the last couple of months. Very cool!

I'm trying to generate some time series POA. For fixed tilt, I've been using get_total_irradiance(). That works well.
However, when I tried to use tracking.singleaxis() to get tracker angles, and input the tracker_theta return into get_total_irradiance(), I'm getting some funny looking results.

Is tracking.singleaxis() the recommended method? Should I be using SingleAxisTracker.get_irradiance()?? What's the difference?
I could share code, and get in the weeds, but I'm just looking for a general understanding here.

Thanks everyone!

[kandersolar]

Howdy @cpullium, it's always important make sure that the values you're passing in match the required parameters. For example, the docs page for get_total_irradiance lists surface_tilt and surface_azimuth (not tracker_theta) as parameters. Conceptually, get_total_irradiance is agnostic to any mounting strategy -- what matters for transposition is the collector surface's tilt & azimuth, and it doesn't make any difference whether that orientation came from a fixed rack or a SAT. Note that the dataframe returned from tracking.singleaxis() contains surface_tilt and surface_azimuth in addition to tracker_theta.

As for whether to use tracking.singleaxis or SingleAxisTracker -- pvlib's foundation is a set of stand-alone functions like tracking.singleaxis that you can string together to do whatever you want, and built atop that foundation is a collection of classes that might be more convenient for typical use cases. I usually stick to just using the functions myself, but either way is fine and I suggest you use whichever approach you find easier to use. The intro tutorial page goes into more detail about the two approaches. However, in the specific case of SingleAxisTracker, that class is actually deprecated and should not be used in new code. If you do want to go the OO route, the new way is to use a SingleAxisTrackerMount with PVSystem like is done in the PVSystem user guide page.

[cpullium]

Thanks @kanderso-nrel, I was indeed using the wrong input.