Anti-Soiling and Self-Cleaning Properties of Vertically Installed Bifacial PV Modules: Long-Term Field Observations in Arid Climates

In this work, we introduce observations in a long-term experimental study, three years (2022?2024), about the soiling of vertically installed bifacial photovoltaic(BiPV) modules. For comparison, two identical, seven-module grid-connected BiPV strings are implemented in northern Jordan. One string is mounted vertically in an east?west orientation and a 90? tilt angle. The other faces south with a 27? tilt angle. Both arrays are kept uncleaned so that any soiling or natural cleaning mechanism can be observed. Solar irradiance and surface temperature of the modules were logged continuously. Dew formation on the module surfaces and surface appearance were monitored on a regular schedule. The results from observations show that the vertical modules gathered significantly less dust and rarely showed signs of dew adhesion, while the tilted modules often developed hardened deposits after humid nights. Measurements of module temperature show that the vertical surfaces tended to run slightly warmer, by about 0.5?1?C, which plays a role in keeping them above the dew point. Despite the non-optimal tilt angle of the vertically installed modules, they still delivered more than ?90% of the optimally tilted array?s output. One advantage of the vertical configuration can be seen in the elimination of cleaning needs and water use while maintaining stable performance. Such a fact makes vertical installation a credible option for dusty, arid sites.