Condensation Characterization for PV Soiling

Condensation (dew) on PV modules greatly affects their soiling. In this study, we compared several techniques for measuring and characterization of condensation on soiled glass samples in the desert environment of Doha, Qatar. The techniques were: two types of moisture sensor; optical microscopy; scanning electron microscopy image analysis; and dew-point/surface temperatures. It was found that moisture sensors are practical and useful for measuring condensation on PV modules. As condensation increased, dust particles in the soiling layer became more tightly clustered together by the droplets, and more cementation crystal needles were generally observed. Importantly, it was found that condensation commenced when the surface temperature was several °C above the dew point, indicating it is necessary to directly measure condensation on soiled surfaces rather than estimate it from environmental conditions.