A Study On Condensation-Induced Dust Removal Characteristics Of Surface

Solar photovoltaic power generation is one of the key technologies for low-carbon development and energy transformation in the future,which is of great significance to achieve "carbon neutrality".Therefore,China is vigorously developing photovoltaic power generation in the areas with long sunshine hours such as the northwest and desert.However,due to climate,dust accumulation and attachment are common in photovoltaic modules in northwest China(strong light,heavy dust and little rain),which seriously affects the service life and power generation efficiency of photovoltaic modules,such as corrosion effect,hot spot effect and shielding effect.Common surface cleaning methods,such as mechanical method and electrostatic dust shield method,require high operating costs,while anti-soiling coating technology(such as superhydrophobic coat,superhydrophilic coat)has the advantages of simple operation,low cost,free maintenance and so on,and has become a research hotspot in recent years.In this thesis,based on superhydrophobic modification,condensation-induced dust removal experiments were carried out on the surface to achieve self-cleaning of photovoltaic panel.Due to the large temperature difference between day and night in desert areas,dew often occurs on the surface of photovoltaic modules,which leads to "cementation,caking and capillary aging",resulting in dust firmly sticking to the surface,which greatly increases cleaning costs.Studies have shown that if dews spontaneously leaves the surface during the condensation,dust can be removed from the surface.Therefore,this thesis first modified the surface of the material,and then carried out an experimental study of condensation-induced dust removal,focusing on analyzing the effect of surface wettability and dust characteristics.The specific research contents are as follows:Firstly,the effect of dew on the contamination of dust-covered surface was studied.Four surfaces and two types of particles were used for condensation experiments.Studies have shown that in the presence of dew,surface and particle wettability can significantly affect the dynamic behavior of dust.After condensation and drying,the loose dust was flattened on superhydrophilic surface(SHLS)and hydrophilic surface(HLS).On superhydrophobic surfaces(SHBS)and hydrophobic surfaces(HBS),hydrophobic dust forms compact spheres,while hydrophobic dust forms irregular loose shapes.The distribution of dust is closely related to the light transmittance of the surface.For the combination of(super)hydrophilic surface and hydrophilic dust,the more hydrophilic the surface is,the transmittance decreases more obviously,but for the combination of(super)hydrophilic surface and hydrophobic dust,the presence of dew has little effect on transmittance.For the(super)hydrophobic surface,after condensation,the light transmittance of the surfaces are improved,and it doesn't matter the wettability of dust.In addition,the dynamic behavior of dust during condensation is mainly controlled by capillary and interfacial forces.The direction and magnitude of interfacial forces depend on the wettability of the surface and particles.Secondly,the process and mechanism of condensation-induced dust removal on SHBS are studied.According to the dynamic behavior of dust particles during condensation,the condensation-induced dust removal process was divided into four stages: dust agglomeration,sliding dedusting,rolling dedusting and deep dedusting,and the force analysis of each stage was carried out.In addition,Statistical method was used to analyze the change of surface dust coverage rate.The results show that the particle size has a great effect on the dust removal behavior,and small particles are easier to separate from the surface.The higher the relative humidity of air is,the sooner the dust removal process is completed.Surface dust coverage rate has little effect on dust removal.The wettability of SHBS did not degrade after several times of condensation-induced dust removal,indicating that the surface has a certain durability.Finally,the effect of surface wettability on condensation-induced dust removal were studied.The results show that under experimental conditions of this thesis,SHLS,HLS and HBS cannot remove dust,while condensation droplets can remove more than 76% of the dust by rolling on the SHBS and SLIPS(super slippery liquid infused porous surface).The rolling droplets are small and fast,and the dust removal occurs earlier on SHBS.while the rolling droplets are large and slow on SLIPS,but they have a large contact area with the surface and wide cleaning range.Condensation-induced dust removal mainly depends on the interfacial force between dust particles and condensation.The smaller critical diameter of droplet movement,the more conducive to dust removal.