OK, this little exercise helped me figure out a huge mystery. I understand my “butterfly wing” much better now. The shape had me thinking that there might be a mismatch between the parameters I fed the NREL simulator and my actuals. I had been inputting a pitch of 23 and azimuth of 123 based on some written documentation I had, but when I went back and consulted my plans, I really have 4 different arrays, of which only one, had those parameters (6 panels out of 21). the other 3 have the same pitch of 23 but an azimuth of 123 (15 panels out of 21). Guess I’ll have to do as two separate arrays in the NREL simulator, then sum them and see what happens.
The “butterfly wing” becomes a narrower “dragonfly wing” if I use an azimuth of 213 for my entire solar system.
Here’s what it looks like if I create a dual array result in NREL PVWatts using the two different capacities and azimuths. That seems to worsen things. The “eye” in the middle seems to get larger.
If I offset my real solar production 1 hour earlier, still using the dual array NREL comparison data, the “eye” closes and I nearly get a line.
If I offset my real solar production by 2 hours instead, the “dragonfly wing” inverts. Afternoon production looks too large vs. NREL, and morning is too big.
So now I’m finally going to circle back to my original Sense solar data vs. NREL. Here’s the chart once I move to the more correct NREL model that uses two arrays with different (correct) azimuths. Once again I get a similar “dragonfly wing” to what I saw against my historic inverter data.
And if I offset the solar production 1 hour earlier, I get essentially a linear relationship, with lots of well-distributed randomness, as I would expect from the weather modeling.
The bottom line @brettabailey, is that this is the the best you can expect for hour-by-hour modeling from PVWatts.
sense_process_edits4.R (3.3 KB)