Hello Paul,
I´m having some issues with the calculations in PVwattsv1, which I believe stem from the thermal model calculations.
I´m using my own poa values (user_poa), which, as you can see in Fig.1 (output values from a simulation run of pvwattsv1 into an excel sheet) are being read correctly and fed into the algorithm.
However, for what seem to be random hours of the day, the calculated Operating Cell Temperature (tcell), seems to not be correctly calculated, and returns a value barely different from the dry bulb temperature for that hour (as you can see in Fig 2., a print screen of the Weather file being used, with the dry bulb temperatures for the problematic hours highlighted)
I would like to know your take on this, I´ve looked over the Fuentes model calculations on the pdf available on your website (Fuentes M.K., A simplified Thermal Model for Flat-Plate Photovoltaic Arrays, 1987) but can´t seem to find a reason for this error.
Any help would be greatly appreciated,
Kindest regards,
Miguel D.