Large-scale solar photovoltaic (PV) power plants tend to be set in desert areas, which enjoy high irradiation and large spaces. However, due to frequent sandstorms, large amounts of contaminants and dirt are suspended in the air and deposited on photovoltaic modules, which greatly decreases the power efficiency and service life. To clean PV to improve efficiency, many methods were proposed. It was found that the application of the self-cleaning coating on PV modules can effectively reduce dust deposition and improve the efficiency of PV. This paper reviews the dust deposition mechanism on photovoltaic modules, classifies the very recent dust removal methods with a critical review, especially focusing on the mechanisms of super-hydrophobic and super-hydrophilic coatings, to serve as a reference for researchers and PV designers, and presents the current state of knowledge of the aspects mentioned above to promote sustainable improvement in PV efficiency. It was found that the behaviors of dust on photovoltaic modules are mainly deposition, rebound, and resuspension. Particles with a diameter of 1–100 μm are most easily deposited on photovoltaic modules. The use of self-cleaning coatings, especially super-hydrophobic coatings, is beneficial to the rebound and resuspension of particles. The research gaps and development prospects of self-cleaning coatings are also discussed in this paper.

Dust deposition on solar photovoltaic (PV) cells will dramatically reduce the photovoltaic power output. Self-cleaning coating may be a novel method to decrease dust deposition problems. This paper compares self-cleaning performances and mechanisms of super-hydrophobic and super-hydrophilic coating on dirt deposition decrease for solar photovoltaic cells by experimental measurement. In the process of the deposition of dust on solar cells, covering glass, coated and uncoated, is conducted under natural settling conditions. Moreover, the dust removal efficiency of the glass samples with and without coatings is studied under water spraying conditions. The wettability of different surfaces, dust deposition mass, dust removal efficiency, self-cleaning mechanisms, and transmittance of glass samples are investigated and analyzed. Under natural settling conditions, the deposition mass reduction ratio by the super-hydrophilic coating is only 8.1%, while it can reach 85.8% by the super-hydrophobic coating because of surface micro-structures and low surface energy. However, after the water spraying process, the remaining dust mass ratio for the super-hydrophobic surface is only 16.5%, while it is 18.6% for the super-hydrophilic surface. The self-cleaning mechanism of super-hydrophobic coating is that most deposited particles of dust are removed from glass samples by the rolling of liquid droplets. However, the self-cleaning mechanism of super-hydrophilic coating is the breakup of the liquid film. Therefore, both coatings can effectively reduce dust deposition under water spraying conditions. The average transmittance of super-hydrophobic and super-hydrophilic coatings after the water spraying process is 91.1% and 86.4%, respectively, while it is only 61.1% for the uncoated glass sample.

The snow falling on the surface of photovoltaic modules tends to reduce the output power. In order to understand the process of snow accumulating on solar photovoltaic modules and reveal the impact of snow accumulation on photovoltaic conversion efficiency, the snow-cover process was simulated on the surface of photovoltaic modules with different tilt angles by computational fluid dynamics (CFD). On this basis, the relationship between the amount of snow and tilt angle was explored. The snow effect of photovoltaic modules on photoelectric conversion efficiency was studied by building a test platform. At the same time, a measurement platform of snow accumulation on photovoltaic modules and photoelectric conversion efficiency was constructed. Through the experiment of the relationship between snow thickness and snow sliding distance and the power generation efficiency of photovoltaic (PV) modules, the influence of snow thickness and snow area on the power generation efficiency of PV modules is discussed. The results show that the larger angle between the photovoltaic panel and the ground is adverse to the accumulation of snow on the panel. When the thickness of snow reaches 1 cm, the power generation efficiency of the entire photovoltaic module reduces to 7.1% of that as normal. At the same time, the sliding of snow on the photovoltaic panel improves the efficiency of photoelectric conversion. Through the analysis of numerical simulation and experimental results, targeted suggestions are made on how to improve the efficiency of power generation for photovoltaic power stations under snowy conditions, which may provide a reference for engineering work.

To comparatively evaluate the suitability of superhydrophobic and superhydrophilic coatings for photovoltaic (PV) module surfaces in arid and low-rainfall regions, this study investigates their dust deposition mitigation performance under anhydrous conditions and assesses the impact of dust reduction on PV power generation efficiency. An experimental platform for dust deposition and a PV output measurement system were constructed to evaluate the performance of coated PV modules. The open-circuit voltage (U_oc), short-circuit current (I_sc), maximum power (P_max), and dust deposition mass were measured before and after dust exposure. Additionally, the influence of coating properties on dust deposition behavior and the correlation between dust deposition density and PV output power were systematically examined. The experimental data reveal a linear relationship between PV output power loss and dust deposition density. Dust accumulation decreases monotonically with panel tilt angle, while displaying a non-monotonic response to wind speed, peaking at 3.9 m/s. Under optimal conditions (60° tilt angle and 5.2 m/s wind speed), minimal dust deposition densities were observed: 0.25 g/m² for superhydrophobic coated PV modules versus 1.11 g/m² for superhydrophilic coated surfaces. Both superhydrophobic and superhydrophilic coatings demonstrated effective dust deposition inhibition in anhydrous environments. However, the dust deposition mitigation efficiency of the superhydrophobic coating (88.7%) is significantly better than that of the superhydrophilic coating (46.2%) under the working conditions of a large inclination angle (60°) and high wind speed (5.2 m/s). These findings provide critical experimental evidence for optimizing self-cleaning coating selection in PV modules deployed in arid regions.

Electrical equipment is subjected to gas discharge tube (GDT) direct current (dc) breakdown voltage dispersion and breakdown voltage drop after a surge. It is noteworthy that GDT damage may even cause the failure of electrical equipment. Accordingly, the chemical vapor deposition (CVD) of graphene was proposed in this study as an electron emission material of the GDT based on the existing electron powder GDT. The GDT exhibiting a voltage class of 470 V was prepared, and its structure and surge characteristics were analyzed. The effects of gas pressure, aging time, and ambient temperature on the breakdown voltage of the graphene GDT were studied. The surge process of the graphene GDT was simulated using the 8/ $20~\mu \text{s}$ impulse current generator, and the resistance ability of the graphene GDT against the surge was examined. Moreover, it was compared with the same type of commercial electron powder GDT. As indicated by the experimental results, a positive correlation was identified between the gas pressure and the dc breakdown voltage of the graphene GDT under a certain pressure. The effect of aging time and ambient temperature on dc breakdown voltage was limited. The breakdown voltage of the graphene GDT was first increased and then decreased with the increase in the number of surges. After 100 surges, the breakdown voltage of the graphene GDT stabilized at 350 V, whose stability was better than that of the electron powder GDT. The above-described analysis confirmed that graphene GDT exhibits better surge resistance ability.