The Impact of Condensation on Solar Collector Soiling: An Experimental Study

The accumulation of dust particles on solar collectors can gradually degrade optical performance in solar systems - a phenomenon known as soiling. Additionally, the formation of dew on collectors during early mornings introduces new mechanisms that can impact the soiling process. This study investigates the influence of dew on soiling for uncoated solar mirrors using an artificial soiling station. Several experiments were performed changing testing parameters (e.g. sample tilt, dust amount, dew quantity) and monitoring the outcomes with a range of devices including reflectometers, microscopy, scales, and a luminance camera. The outcomes indicated that condensation becomes relevant for condensation loads above 60 g m-2 and its impact is significantly affected by the tilt angle of the samples. When samples are flat or with low tilt, condensation cycles cause particle dispersion, reducing cleanliness by up to 2 %. On the contrary, for high tilt angles, a honeycomb-like soiling patterns with highly reflective regions appear, enhancing cleanliness restoration by 2.3 %. These findings suggest tilting dewy collectors as a passive self-cleaning strategy.