I have implemented the Perez 4 (as numbered by D. Yang, 2016) for a solar PV model. it seems to work but I have no way of knowing if it really is. My panels have a vertical tilt and the Perez model produces peaks of 1.9 and an average of 0.9114 where an isotropic model would have a constant sky view factor of 0.5. Is this reasonable or is there something wrong with my implementation?
Thank all,
I'm now reasonably happy that I have done it correctly. In case anyone else has this question in future I will add that when Direct Normal Irradiation is zero The Perez model should revert to Isotropic (thanks to Bill Marion of NREL for pointing this out to me).
Also, a quick check is to set plane tilt to zero then the Perez model should normalise, less any reflection losses.
Obviously, these don't guarantee its working but in the absence of other data to compare to they at least provide a useful sanity check.
The pvlib implementation in either python or matlab should be your reference code.
- Badges
- Science topic