Condensation as a predictor of PV soiling

Condensation (dew) strongly affects PV soiling: it causes dust particles to stick to PV modules, yet conversely it can also clean modules as the dew droplets run off. These mechanisms have been well studied qualitatively, but because weather stations at PV sites rarely include condensation sensors, the quantitative link between dew and PV soiling rate is not well known. The goal of this study was to investigate this relationship numerically, and especially whether condensation data improves the accuracy of PV soiling models. We performed a field study in Doha, Qatar, in which condensation on a PV module, “standard” meteorological parameters, and the daily PV soiling rate were measured for 2.5 years. We found low correlation between all variables and the soiling rate, however condensation was among the more beneficial variables to include in soiling models (depending on the statistical analysis method used). Also, it is necessary to measure condensation directly, because it was not accurately predicted from dew-point and module surface temperatures.