Accuracy Comparison of Various PV Models
“The PV Watts model and single-diode models (e.g., NREL’s SAM 5 parameter model) are popular tools for modeling PV system power generation. The performance of these models has been well studied and has been shown to be accurate, but highly sensitive to the derate assumptions used. Accurate derate estimation is therefore a significant challenge faced by PV system fleet operators attempting to use these models to understand system performance.
Statistical models, such as the one used in the ASTM-2848 performance validation standard, in contrast use a corpus of measured power generation data to calibrate their PV models to as-built system performance. This obviates the need to use information such as the inverter or array type in the modeling process, but does require the collection and evaluation of system performance data. In this study, we compare the performance of the PV Watts, a single-diode model, the ASTM-2848 model, and a derate-tuned version of PV Watts across a representative sample of sites across a multi-year period.”