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• Vibration of 6 kinds of PV module under robot cleaning were measured. • A module's size was the dominant factor in how much it vibrated. • A module's frame and glass thickness had little influence on its vibration. • Overall the amount of vibration by robot cleaning was small – less than 1 mm. • Strong wind caused more severe module vibrations than the cleaning robot. • Large-format modules and robots that run on the modules may present greater vibration risk. Automatic PV cleaning machines ("robots") are becoming widely used in desert regions. The motion of the robot and its brushing action can vibrate the PV modules being cleaned. This study measured the vibration of six different kinds of PV module, excited by a single kind of commercial cleaning robot. The robot's brushes were straight, rather than helical, which imparted a periodic excitation to the modules at approximately 7 Hz. For comparison, module vibration by strong wind was also measured. It was found that (i) among similar-sized PV modules, the amount of vibration was largely independent of the module construction (glass thickness and frame), (ii) modules tended to vibrate at their natural frequency rather than the brush (excitation) frequency, and (iii) the module deflection range by robot cleaning was approximately 0 mm upward to 1 mm downward, while in strong wind it was approximately 2 mm upward to 1 mm downward. In this study, which used modules up to 2 × 1 m, the particular cleaning robot did not cause significant vibration, however as commercial modules become larger they may also become more flexible and prone to larger deflections. [ABSTRACT FROM AUTHOR]

Arid areas account for more than 20% of Earth's surface. Many of these arid areas suffer from harsh climates where energy consumption is high and production coexists with high hydrological stresses. In such areas, the production of water is directly linked to the production of electricity, bringing the Energy–Water nexus to a higher level [Heggy et al., Sustainable Energy-Water-Environment Nexus in Deserts (Springer, 2022)]. Under the current energy transition from a fossil-based economy to a renewable energy-based system, arid areas are seen as potential reservoirs for electricity production due to their high solar potential, thereby helping to achieve global decarbonation targets. This energy production transition will strongly affect the Energy–Water nexus as it will contribute to the decoupling of electricity from water production. The International Conference on Sustainable Energy–Water–Environment Nexus 2019 (ICSEWEN19) conference was the first to address the Sustainable Energy–Water Nexus in Deserts, bridging the gap between research and industry and highlighting the research capabilities relevant to Qatar, the region, and internationally. The Invited Papers from the International Conference on Sustainability, Energy, Water, and Environment Nexus in Desert Climates Special Collection in Journal of Renewable and Sustainable Energy presents articles covering the main elements of the conference with respect to solar photovoltaic implementation in desert environments as a key element to succeed in this global energy transition. [ABSTRACT FROM AUTHOR]

As PV cleaning machines become widely adopted in desert regions, there is concern that frequent dry-brushing might abrade modules' anti-reflective coating (ARC). It is common to study ARC abrasion via accelerated lab tests, which typically differ from real-world PV cleaning regarding sample format, test conditions and characterization tools. This paper reviews research on PV ARC cleaning abrasion, focusing on differences in experimental techniques between the lab and field. The main conclusions are: (1) coupon tests should be verified with full-size modules due to dependence of coating properties on sample size, (2) lab tests should be verified outdoors with non-accelerated cleaning schedules because abrasion is largely caused by the soiling layer itself when brushing, (3) reflectivity is well suited to measuring ARC abrasion because it can be performed in the field and is reasonably consistent with module optical performance, (4) different ARCs exhibit a wide range of abrasion susceptibility whereas bare glass is essentially immune to dry brushing. [ABSTRACT FROM AUTHOR]