Self-cleaning nano-coating for photovoltaic panels in alpine regions and method for its preparation

Abstract

This invention belongs to the field of nano-coating technology, specifically a self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions and its preparation method. The coating includes a base layer and a superhydrophobic photothermal layer covering the base layer. The base layer includes a silane coupling agent and nano-titanium dioxide sol. The superhydrophobic photothermal layer includes multi-level micro / nano-roughened silica modified with low surface energy materials and near-infrared absorbing tungsten bronze nanoparticles. The multi-level micro / nano-roughened silica includes silica microspheres with a particle size of 200-500 nm, and silica nanospheres with a particle size of 50-80 nm are attached to the surface of the silica microspheres. In this invention, the multi-level micro / nano-roughened silica has higher mechanical stability and is less prone to overall failure under stress. When subjected to ice crystal compression, each silica nanosphere undergoes slight displacement and deformation to dissipate stress, rather than completely rigidly resisting fracture. The near-infrared absorbing tungsten bronze nanoparticles generate heat, increasing the thickness of the water film between the ice and the coating, and reducing the adhesion of the ice layer.

Description

Technical Field

[0001] This invention belongs to the field of nano-coating technology, and in particular to a self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions and its preparation method. Background Technology

[0002] In the vast, sparsely populated plateau regions of western Sichuan, where solar radiation is intense, streetlights are typically powered by solar energy—by installing photovoltaic panels at the top of the streetlight poles—to save on power costs. Currently, in high-altitude, cold regions, photovoltaic panels often suffer from ice and snow covering the panels, blocking sunlight and drastically reducing or even eliminating power generation. Mechanical de-icing can damage the panels and is labor-intensive. To prevent foreign objects from accumulating on the panels, a self-cleaning nano-coating is usually applied. Two common types of nano-coatings exist: one is a superhydrophilic coating based on nano-titanium dioxide, zinc oxide, and silicon dioxide. Under ultraviolet light, nano-titanium dioxide generates hydroxyl radicals that decompose oil and organic matter. The coating has a contact angle of <5°, allowing rainwater to form a uniform water film that washes away dust. The other type is a superhydrophobic coating based on fluorine-containing nanomaterials and nano-silica. This creates a micro-nano rough surface, reducing surface energy. It has a contact angle >150° and a roll-off angle <10°. Rainwater forms droplets that carry away dust as they roll, eliminating the need for ultraviolet light. These nano-coatings are suitable for low-altitude areas. In high-altitude, icy regions, conventional superhydrophobic coatings become brittle at low temperatures, and their micro- and nano-structures are easily pierced by ice crystals or destroyed by frost, losing their superhydrophobic properties. Furthermore, existing coatings are usually single-function coatings, making it difficult for them to operate stably under extreme low-temperature, icing, and frost-forming cycling conditions. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions and a method for preparing the same, so as to solve the above-mentioned problem.

[0004] To solve the above problems, the technical solution adopted by the present invention is: a self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions, comprising a base layer and a superhydrophobic photothermal layer covering the base layer;

[0005] The base layer comprises a silane coupling agent and nano-titanium dioxide sol;

[0006] The superhydrophobic photothermal layer comprises multi-level micro / nano roughened silica modified with low surface energy material and near-infrared absorbing tungsten bronze nanoparticles. The multi-level micro / nano roughened silica comprises silica microspheres with a particle size of 200-500 nm, and silica nanospheres with a particle size of 50-80 nm are attached to the surface of the silica microspheres.

[0007] Furthermore, the near-infrared absorbing tungsten bronze nanoparticles have a particle size of 20-40 nm.

[0008] Furthermore, the low surface energy material includes fluorosilanes.

[0009] Furthermore, a tough support layer is provided between the base layer and the superhydrophobic photothermal layer. The tough support layer is a network polymer of polyurethane acrylate and silicone resin, and the network polymer is filled with sheet-like alumina and mica sheets.

[0010] Furthermore, elastic hollow microspheres are added to the tough support layer.

[0011] Furthermore, the surface of the superhydrophobic photothermal layer is anchored with high-hardness UV resin through dot-coated points to form a slip film layer. When the wind blows across the surface of the slip film layer, it generates a shear force parallel to the superhydrophobic photothermal layer, causing the slip film layer to deform and slip locally, thus breaking the bond between the ice crystals and the slip film layer.

[0012] Furthermore, the slip film layer is a methylphenyl silicone resin or fluorosilicone resin film with a thickness of 1-3 μm.

[0013] The above-mentioned method for preparing self-cleaning nano-coatings for photovoltaic panels in high-altitude and cold regions includes:

[0014] Preparation of base solution: Mix silane coupling agent, anhydrous ethanol and deionized water, adjust the pH to 4-5 with acetic acid, and stir to obtain pre-hydrolyzed solution;

[0015] Nano-titanium dioxide sol was added to the pre-hydrolyzed solution and ultrasonically dispersed to obtain a base solution;

[0016] Preparation of superhydrophobic photothermal layer suspension: Tetraethyl orthosilicate was added dropwise to an aqueous solution of ethanol at a rate of 2-2.5 mL / min in a water bath at 25±1℃. After the addition was completed, ammonia was added at once, and the reaction was carried out for 6-7 h to obtain silica nanosphere sol.

[0017] In a water bath at 35±1℃, tetraethyl orthosilicate and ethanol were mixed at a volume ratio of 1:1, and the mixture was added dropwise to silica nanosphere sol at a rate of 1-1.2 mL / min. After the addition was complete, the reaction was allowed to proceed for 12-14 h. After the reaction was completed, the reaction solution was allowed to stand and age at 40-45℃ for at least 24 h. Then, the solid product was separated, washed, and dried to obtain multi-level micro-nano rough silica powder.

[0018] Multi-level micro-nano rough silica powder and near-infrared absorbing tungsten bronze nanoparticles were mixed, and then the surface was modified with fluorosilane to obtain composite powder.

[0019] Additives and composite powders are added to a fluorocarbon solvent and dispersed uniformly to obtain a superhydrophobic photothermal layer suspension;

[0020] Spraying: First, the base layer solution is sprayed onto the surface of the photovoltaic glass and then heat-treated at a temperature of 120-140℃ to form the base layer;

[0021] Then, a superhydrophobic photothermal layer suspension is sprayed on and sintered and cured at a temperature of 140-160℃ to obtain the superhydrophobic photothermal layer.

[0022] Furthermore, it also includes the preparation of the toughness support layer slurry: the coupling agent KH-570 is mixed with an ethanol solution, the pH is adjusted to 4-5 with hydrochloric acid, and hydrolysis is carried out for at least 30 minutes to obtain the coupling agent solution;

[0023] Flake alumina and mica flakes were added to a coupling agent solution, ultrasonically dispersed for at least 30 minutes, then filtered and dried to obtain a mixed filler.

[0024] Add methyl ethyl ketone solvent and silicone resin to the reactor, stir evenly at 40°C, then add polyurethane acrylate prepolymer and reactive diluent, heat to 60°C, stir for at least 1 hour to obtain a transparent resin system.

[0025] Add the mixed filler to the resin system and stir for at least 30 minutes. Then add the photoinitiator, defoamer and leveling agent. Then disperse the mixture at a temperature below 50°C using a high-speed disperser for at least 30 minutes. After dispersion, grind, defoam and filter in sequence to obtain the tough support layer slurry.

[0026] During spraying, after the base layer is formed, a toughness support layer slurry is sprayed on. Ultraviolet light is used to cure the surface of the toughness support layer slurry. Then, it is heat-cured at a temperature of 90-105℃ to obtain the toughness support layer. Next, a superhydrophobic photothermal layer suspension is sprayed onto the surface of the toughness support layer.

[0027] Furthermore, after obtaining the superhydrophobic photothermal layer, a high-hardness UV resin in a dot array is coated on the surface of the superhydrophobic photothermal layer, and the high-hardness UV resin is cured by ultraviolet irradiation to obtain high-hardness UV resin anchors.

[0028] An organic solvent solution of methylphenyl silicone resin or fluorosilicone resin is spin-coated onto the surface of a superhydrophobic photothermal layer, and then cured at 80-150℃ for 1-2 hours to obtain a methylphenyl silicone resin or fluorosilicone resin film connected to high-hardness UV resin anchor points.

[0029] The beneficial effects of this invention are as follows: Traditional superhydrophobicity relies on brittle nanowires, nanocones, and other structures. When water freezes, the volume expands, and the sharp ice crystals exert significant local stress on the surface hydrophobic structure, leading to its destruction. In this invention, multi-level micro / nano roughened silica uses large-particle-size silica microspheres as the macroscopic framework. The silica nanospheres construct micro-roughness and air cushions, resulting in higher mechanical stability compared to single nanowires or nanocones, making them less prone to overall failure under stress. Furthermore, the presence of gaps and connection points between the individual silica nanospheres allows for minute displacements and deformations to dissipate stress when subjected to ice crystal compression, rather than rigid resistance leading to fracture.

[0030] Multi-level micro / nano roughened silica and near-infrared absorbing tungsten bronze nanoparticles, after modification with low surface energy materials, form a superhydrophobic coating interface with a contact angle >150° and a roll-off angle <10°. Ice's thermodynamic stability is a solid state below 0°C, but a nanometer-thick liquid water film spontaneously forms on the surface of ice (especially in areas in contact with heterogeneous interfaces). This phenomenon is called surface pre-melting; the closer the ambient temperature is to 0°C, the thicker the pre-melted layer; the lower the ambient temperature, the thinner the pre-melted layer, but it does not completely disappear. In this invention, near-infrared absorbing tungsten bronze nanoparticles are added to the superhydrophobic photothermal layer. These nanoparticles can absorb near-infrared light that photovoltaic panels cannot utilize and generate heat, making the coating surface temperature slightly higher than the ambient temperature. This increases the thickness of the water film between the ice and the coating. This water film weakens the mechanical interlocking and adhesion between ice crystals and the coating surface, greatly increasing the difficulty for ice crystals to penetrate the coating and making them more prone to overall detachment, thus protecting the hydrophobic structure of the coating.

[0031] Furthermore, in low-temperature and high-humidity environments, water vapor in the air condenses directly onto the superhydrophobic surface, forming frost. The frost crystals fill the gaps in the micro / nano structure, creating a Wenzel-like wetting effect, transforming the surface from superhydrophobic to hydrophilic. External moisture then rapidly freezes using the frost crystals as a matrix. The near-infrared absorbing tungsten bronze nanoparticles of this invention significantly delay the condensation and nucleation time of water vapor on the coating surface by increasing the coating surface temperature, thereby inhibiting frost formation.

[0032] The substrate consists of silane coupling agents and nano-titanium dioxide sol. Silane coupling agents (such as KH-560) can form strong chemical bonds with the hydroxyl groups on the surface of photovoltaic glass, providing a solid adhesion base for the superhydrophobic photothermal layer. Nano-titanium dioxide sol can fill the micropores formed after the silane coupling agent is cured, forming a dense inorganic-organic hybrid film, which improves the hardness and wear resistance of the substrate. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of Embodiment 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of Embodiment 2 of the present invention;

[0035] Figure 3 This is a schematic diagram of Embodiment 3 of the present invention;

[0036] Figure reference numerals: 1—base layer; 2—superhydrophobic photothermal layer; 3—tough support layer; 4—slip film layer; 5—high-hardness UV resin anchor point. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] Example 1

[0039] The self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions in this embodiment, such as Figure 1 As shown, it includes a base layer 1 and a superhydrophobic photothermal layer 2 covering the base layer 1.

[0040] The base layer 1 is connected to the photovoltaic glass panel and specifically includes a silane coupling agent and nano-titanium dioxide sol.

[0041] The silane coupling agent can be KH-560 type silane coupling agent (γ-glycidoxypropyltrimethoxysilane), which hydrolyzes in aqueous solution to generate silanol groups, which can undergo dehydration condensation reaction with silanol groups on the glass panel surface to form stable Si-O-Si covalent bonds, thereby firmly anchoring the base layer 1 to the glass surface. The chemical bonding strength is much higher than that of traditional physical adsorption, and it can withstand extreme temperature difference cycles of -40℃ to 60℃, avoiding coating peeling caused by excessive day and night temperature differences and large thermal expansion and contraction deformation of photovoltaic glass panels.

[0042] The nano-titanium dioxide sol has a particle size of 10-30nm, which can fill the micropores formed after the silane coupling agent is cured, forming a dense inorganic-organic hybrid film and improving the hardness and wear resistance of the base layer 1.

[0043] The superhydrophobic photothermal layer 2 is used for hydrophobicity and low-temperature anti-icing. Specifically, the superhydrophobic photothermal layer 2 includes multi-level micro-nano roughened silica modified with low surface energy material and near-infrared absorbing tungsten bronze nanoparticles. The multi-level micro-nano roughened silica includes silica microspheres with a particle size of 200-500 nm, and silica nanospheres with a particle size of 50-80 nm are attached to the surface of the silica microspheres.

[0044] The superhydrophobic photothermal layer 2 is composed of multi-level micro-nano rough silica modified with low surface energy material and near-infrared absorbing tungsten bronze nanoparticles modified with low surface energy material. It not only constructs a superhydrophobic surface, but also realizes selective near-infrared photothermal conversion. At the same time, the mechanical strength of the superhydrophobic photothermal layer 2 is enhanced through the multi-level micro-nano structure.

[0045] Specifically, multi-level micro-nano roughened silica provides the core micro-nano roughened structure substrate for the superhydrophobic photothermal layer 2. It adopts a two-level composite structure of "microsphere-nanosphere" to form a microscopic shape of "nanospheres growing on microspheres". The silica microspheres serve as a macroscopic support framework, which has high temperature resistance, strength and impact resistance, avoiding the defects of easy breakage and overall failure of single nanoscale structures. The silica nanospheres attached to the surface of the microspheres further construct a fine nanoscale roughened structure. The tiny pores between the nanospheres can trap air, forming an air cushion, reducing the actual contact area between ice and the coating surface, and weakening the ice adhesion.

[0046] In this invention, the gradient roughness structure formed by the micron-scale framework and nano-scale protrusions enables the coating surface to form a stable Cassie-Baxter superhydrophobic state, significantly reducing surface energy. On the other hand, there are connection points and pores between the individual silica nanospheres, which can undergo minute displacement and deformation when subjected to external forces such as ice crystal compression to dissipate stress, avoiding the breakage of the micro-nano structure and the destruction of the rough morphology caused by rigid resistance, thereby maintaining long-term effective superhydrophobic performance and solving the problems of poor mechanical stability and easy puncture by ice crystals in traditional single nanowire structures.

[0047] Near-infrared absorbing tungsten bronze nanoparticles achieve active photothermal de-icing functionality. Their particle size is controlled at 20-40 nm, and they are dispersed in a mass ratio of 3:1 to 5:1 with multi-level micro / nano rough silica, uniformly distributed in the gaps and surface of the silica micro / nano structure. These near-infrared absorbing tungsten bronze nanoparticles exhibit strong absorption capacity (absorption rate > 85%) in the near-infrared band (700-2500 nm), which photovoltaic cells cannot utilize in sunlight, while possessing high transmittance (transmittance > 70%) in the visible light band (400-700 nm). Without affecting the light operation of the photovoltaic module, they efficiently absorb near-infrared light and convert it into heat energy, achieving localized heating of the coating surface.

[0048] In the extreme low-temperature environment of high-altitude and cold regions, the localized micro-heat generated by near-infrared absorbing tungsten bronze nanoparticles can raise the surface temperature of the superhydrophobic photothermal layer 2 by about 5°C compared to the ambient temperature. This increases the thickness of the pre-melted water film between the ice and coating interfaces (at an ambient temperature of -20°C, the water film thickness can reach 5-10 nm during the day). This water film can significantly weaken the mechanical interlocking and adhesion between ice crystals and the coating surface, and also acts as an isolation layer, making it difficult for ice crystals to penetrate the micro-nano structure and more likely to detach as a whole. At the same time, localized micro-heat can delay the ice nucleus growth and freezing process, further improving the anti-icing and de-icing effects, achieving a synergistic effect of passive anti-icing (superhydrophobic + multi-level structure) and active anti-icing (photothermal conversion).

[0049] In summary, the superhydrophobic photothermal layer 2 achieves the synergistic unity of three major functions: superhydrophobic self-cleaning, mechanical structural stability, and active photothermal de-icing. It can effectively address the core problems faced by photovoltaic panels in high-altitude and cold regions, such as snow cover, ice crystal adhesion, pollutant accumulation, and structural damage, ensuring that the coating remains stable for a long time.

[0050] In this invention, the low surface energy material includes fluorosilanes. The low surface energy material is a fluorosilane compound (preferably perfluorooctyltriethoxysilane), which can be chemically grafted onto the surface of multi-level micro / nano roughened silica. Fluorosilane molecules have extremely low surface energy, and the hydrophobic groups (fluoroalkyl groups) in their molecular structure can form a dense low surface energy film on the silica surface. Combined with the multi-level micro / nano roughened structure, the water contact angle of the superhydrophobic photothermal layer 2 is greater than 150°, and the roll-off angle is less than 10°, thus possessing excellent hydrophobic and self-cleaning properties. It can effectively resist the adhesion of contaminants such as dust, sand, and bird droppings, while reducing the residence time of liquid water on the coating surface and lowering the probability of icing. Compared with traditional low surface energy modification materials, fluorosilanes have stronger weather resistance, UV aging resistance, and chemical stability. They can remain stable for a long time in high-altitude and cold regions under strong ultraviolet radiation and extreme temperature differences, avoiding the failure of superhydrophobic properties caused by the degradation of low surface energy materials and ensuring the service life of the coating. Meanwhile, fluorosilanes can undergo dehydration condensation reactions with hydroxyl groups on the surface of silica to form stable Si-O-Si covalent bonds, ensuring that the modified layer is firmly bonded to the silica substrate and is not easily detached.

[0051] The method for preparing the self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions in this embodiment includes:

[0052] Preparation of base solution: Mix silane coupling agent, anhydrous ethanol and deionized water, adjust the pH to 4-5 with acetic acid, and stir to obtain pre-hydrolyzed solution.

[0053] Specifically, KH-560 coupling agent with a purity ≥98% was selected as the silane coupling agent. The silane coupling agent, anhydrous ethanol, and deionized water were weighed at a mass ratio of 1:10:1.5 and added sequentially to a container while stirring. Simultaneously, glacial acetic acid was slowly added dropwise to adjust the pH of the system to 4-5. This pH range promotes the hydrolysis of the methoxy group in the KH-560 molecule to generate silanol groups, laying the foundation for subsequent bonding with the nano-titanium dioxide sol. Stirring was continued for 30 minutes to ensure complete hydrolysis of the silane coupling agent, resulting in a transparent and homogeneous pre-hydrolyzed solution.

[0054] Nano-titanium dioxide sol (3% solid content, 10-30 nm particle size, anatase type) was added to the pre-hydrolyzed solution at a mass ratio of 1:6 to the pre-hydrolyzed solution. The solution was then transferred to an ultrasonic disperser and ultrasonically dispersed for 30 minutes at 300 W and 40 kHz. Uniform ultrasonic dispersion ensured that the nano-titanium dioxide particles were evenly dispersed in the system without significant agglomeration, resulting in a light blue, transparent base layer solution. Ultrasonic dispersion effectively breaks down the van der Waals forces between the nano-titanium dioxide particles, preventing particle agglomeration that could lead to excessively high porosity in the base layer 1, thus improving the compactness and mechanical strength of the base layer 1.

[0055] Preparation of the superhydrophobic photothermal layer suspension: A constant temperature water bath was constructed. Ethanol and deionized water were mixed at a volume ratio of 3:1 at 25±1℃ to obtain an aqueous ethanol solution. The aqueous ethanol solution was stirred while tetraethyl orthosilicate was slowly added dropwise at a rate of 2-2.5 mL / min. After the addition was complete, ammonia solution (25-28% by mass) was added all at once, with a volume ratio of ammonia solution to tetraethyl orthosilicate of 1:5. The reaction was continued with stirring for 6-7 hours to obtain a milky white, homogeneous silica nanosphere sol. Under these conditions, tetraethyl orthosilicate undergoes a sol-gel reaction catalyzed by ammonia solution, stably generating silica nanospheres with a particle size of 50-80 nm. Controlling the reaction time to 6-7 hours ensures uniform nanosphere particle size and avoids excessively wide particle size distribution.

[0056] In a water bath at 35±1℃, tetraethyl orthosilicate and anhydrous ethanol were mixed at a volume ratio of 1:1 to obtain a mixture. This mixture was then added dropwise to the silica nanosphere sol at a rate of 1-1.2 mL / min. After the addition was complete, the mixture was stirred continuously for 12-14 h. During this process, some silica nanospheres self-assembled into micron-sized clusters using the original nanospheres as a core, constructing a multi-level structure of nanospheres attached to micron-sized clusters.

[0057] The dropping speed and water bath temperature need to be precisely controlled to avoid micron clusters being too large or too small, and to ensure the integrity of the multi-level rough structure.

[0058] After the reaction, the reaction solution was transferred to a constant temperature settling chamber and aged at 40-45℃ for at least 24 hours to further stabilize the hierarchical structure. The solid product was then separated, washed, and dried to obtain hierarchical micro / nano-rough silica powder. Separation was performed by centrifugation (8000 r / min, 15 min) to collect the solid product, which was washed three times with anhydrous ethanol to remove unreacted tetraethyl orthosilicate, ammonia, and other impurities. The product was then placed in a vacuum drying oven and dried at 60℃ for 12 hours. After grinding, a white, powdery hierarchical micro / nano-rough silica powder was obtained. The silica micron clusters in this powder had a particle size of 200-500 nm, and the silica nanospheres attached to the surface had a particle size of 50-80 nm.

[0059] Multi-level micro-nano rough silica powder and near-infrared absorbing tungsten bronze nanoparticles were mixed, and then the surface was modified with fluorosilane to obtain a composite powder.

[0060] Specifically, the above-mentioned multi-level micro-nano rough silica powder and near-infrared absorbing tungsten bronze nanoparticles were weighed at a mass ratio of 4:1 and added to a high-speed mixer. The mixture was then mixed at a speed of 1000 r / min for 15 min to obtain a mixed powder.

[0061] The mixed powder was added to anhydrous ethanol, followed by fluorosilane (3-5% of the powder mass). A reflux apparatus was set up, and the mixture was refluxed at 70-80℃ for 2-3 hours. This allowed the fluorosilane molecules to be grafted onto the silica surface via Si-O-Si covalent bonds, forming a low surface energy modification layer. After the reaction, the mixture was centrifuged, washed twice with ethanol, and vacuum dried at 60℃ for 8 hours to obtain the superhydrophobic photothermal composite powder.

[0062] The additives and composite powder were added to a fluorocarbon solvent (perfluorohexyl ethane) and uniformly dispersed to obtain a superhydrophobic photothermal layer suspension. Specifically, the additives included a dispersant and a defoamer. The fluorocarbon solvent, composite powder, dispersant BYK-163, and defoamer BYK-024 were weighed in a mass ratio of 10:1:0.2:0.1 and added to a dispersion tank in sequence. First, mechanical stirring (500 r / min) was started and stirred for 20 min. Then, the mixture was transferred to a high-pressure homogenizer and homogenized at a pressure of 30 MPa for 10 min to ensure that the composite powder was uniformly dispersed in the fluorocarbon solvent without agglomerated particles, resulting in a uniform and stable superhydrophobic photothermal layer suspension with a viscosity controlled at 20-30 mPa·s.

[0063] Spraying: First, the base solution is sprayed onto the surface of the photovoltaic glass and then heat-treated at 120-140℃ to form base layer 1. Before spraying, the surface of the photovoltaic glass is cleaned, and then the base solution is sprayed onto the glass surface using electrostatic spraying. The spraying pressure is controlled at 0.3-0.4MPa, the spraying distance is 20-30cm, and the dry film thickness of the coating is controlled at 50-100nm. After spraying, the glass substrate is transferred to a constant temperature oven and heat-treated at 120-140℃ for 30min to fully solidify the base solution and form a dense base layer 1. This heat treatment temperature can promote the cross-linking reaction between the silane coupling agent and the glass substrate and nano-titanium dioxide sol, improve the adhesion of base layer 1, and at the same time avoid cracking of base layer 1 due to high temperature.

[0064] A superhydrophobic photothermal layer suspension is then sprayed onto the substrate and sintered at 140-160℃ to obtain superhydrophobic photothermal layer 2. After the substrate 1 cools to room temperature, the superhydrophobic photothermal layer suspension is sprayed onto the surface of substrate 1 using the same spraying equipment. The spraying pressure is 0.4-0.5MPa, the spraying distance is 25-35cm, and the dry film thickness of the coating is controlled at 8-12μm. After spraying, the photovoltaic glass is transferred to a high-temperature sintering furnace and sintered at 140-160℃ for 60min to further stabilize the fluorosilane modification layer and improve the interfacial bonding strength between the superhydrophobic photothermal layer 2 and the substrate 1. The sintering temperature is controlled at 140-160℃ to avoid the decomposition of fluorosilane leading to failure of hydrophobic properties, while ensuring a dense coating structure. Too high a temperature will damage the photothermal properties of the near-infrared absorbing tungsten bronze nanoparticles, while too low a temperature will result in insufficient curing of the coating and a decrease in wear resistance.

[0065] After sintering and curing, the material is allowed to cool naturally to room temperature, resulting in a self-cleaning nano-coating for photovoltaic panels in cold regions.

[0066] The performance of the self-cleaning nanocoating prepared in this embodiment was tested, and the results are as follows:

[0067] Substrate adhesion (cross-cut test) ≥ 5B;

[0068] The superhydrophobic photothermal layer has a water contact angle ≥152° and a roll-off angle ≤8°; under -20°C conditions, after 10 minutes of near-infrared light irradiation, the surface temperature rises to -14°C and the ice adhesion strength is ≤8kPa.

[0069] After 500 freeze-thaw cycles (-40℃ to 25℃), the coating showed no cracking or delamination, and the hydrophobicity retention rate was ≥90%.

[0070] After UV aging (2000h), the surface does not yellow and the adhesion retention rate is ≥92%, which can meet the long-term operation requirements of photovoltaic panels in high-altitude and cold regions.

[0071] Example 2

[0072] The self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions in this embodiment, such as Figure 2 As shown, it includes a base layer 1, a tough support layer 3, and a superhydrophobic photothermal layer 2 arranged sequentially. The base layer 1 and the superhydrophobic photothermal layer 2 are exactly the same as in Example 1. The tough support layer 3 has a thickness of 3-5 μm and is composed of a network polymer of polyurethane acrylate and silicone resin. The network polymer is filled with sheet-like alumina and mica sheets.

[0073] Polyurethane segments provide strong toughness and adhesion, while silicone segments provide extremely low glass transition temperature and weather resistance. The two interpenetrate to form a rigid network matrix that remains elastic at low temperatures, which can improve the overall low-temperature toughness and impact resistance of the coating and prevent low-temperature brittleness.

[0074] Flake alumina has high hardness and high thermal conductivity, which can improve the wear resistance, hardness and transverse tensile strength of the coating; mica flakes have a high aspect ratio and are stacked in layers in the coating to effectively block ultraviolet penetration and stress crack propagation, effectively buffer and dissipate thermal stress caused by diurnal temperature differences, and prevent the coating from cracking or peeling off.

[0075] Due to the large diurnal temperature range on the surface of photovoltaic panels in high-altitude and cold regions, the photovoltaic glass undergoes significant thermal expansion and contraction, which can easily lead to coating cracking and peeling. In this invention, elastic hollow microspheres are added to the tough support layer 3. When subjected to external forces (such as thermal stress or impact), the elastic hollow microspheres can undergo elastic deformation, absorb and disperse energy, and prevent crack initiation and propagation.

[0076] The preparation method of the self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions in this embodiment includes the preparation of a base solution, the preparation of a superhydrophobic photothermal layer suspension, the preparation of a tough support layer slurry, and spraying. The processes for preparing the base solution and the superhydrophobic photothermal layer suspension are the same as in Example 1. The preparation process of the tough support layer slurry is as follows:

[0077] Coupling agent KH-570 was mixed with ethanol at a volume ratio of 1:10 and stirred. Hydrochloric acid solution (36-38% by mass) was slowly added dropwise to adjust the pH to 4-5. The mixture was stirred continuously for at least 30 minutes to hydrolyze the mixture, resulting in a transparent and homogeneous coupling agent solution. This pH value and hydrolysis time ensure that the methoxy groups in the KH-570 molecules are fully hydrolyzed to generate silanol groups, laying the foundation for subsequent bonding with the hydroxyl groups on the surface of the sheet filler and improving the compatibility between the filler and the resin matrix.

[0078] Weigh flake alumina and mica flakes at a mass ratio of 2:1. The flake alumina has a particle size of 1-5 μm and a thickness of 100-300 nm; the mica flakes have a particle size of 2-8 μm and a thickness of 200-500 nm. Add the flake alumina and mica flakes to the coupling agent solution and transfer to an ultrasonic disperser (300 W power, 40 kHz frequency). Disperse the mixture ultrasonically for at least 30 min to ensure that the flake filler is uniformly dispersed in the coupling agent solution and that the coupling agent molecules are fully grafted onto the filler surface. After dispersion, separate the solid filler by vacuum filtration and place it in a vacuum drying oven at 60 °C for 2 h to remove residual solvent and moisture, obtaining a surface-modified mixed filler. Modification with coupling agent KH-570 can reduce the surface energy of the flake filler, prevent its agglomeration in the resin matrix, and improve the interfacial bonding strength between the filler and the matrix.

[0079] Butyl ketone (MEK) solvent and silicone resin (methylphenyl silicone resin, 50% solids content) were added to the reactor at a mass ratio of 3:1. The mixture was stirred at 40°C (300 rpm) for 20 minutes to ensure the silicone resin was fully dissolved in the MEK. After thorough stirring, polyurethane acrylate prepolymer (PUA prepolymer, 60% solids content, functionality 3) and reactive diluent TMPTA (trimethylolpropane triacrylate) were added sequentially at a mass ratio of 1:5. The amount of TMPTA was 10% of the mass of the polyurethane acrylate prepolymer. The reactor temperature was raised to 60°C and stirred for at least 1 hour to ensure thorough mixing and initial cross-linking of the resin components, resulting in a transparent and homogeneous interpenetrating network resin system. Stirring at 60°C promoted the interweaving of polyurethane acrylate prepolymer and silicone resin segments, forming a network skeleton with both toughness and weather resistance.

[0080] Add the mixed filler and elastic hollow microspheres (acrylic, particle size 50-200 nm, hollowness 30-50%, industrial grade) to the above resin system. The amount of mixed filler is 15% of the resin system mass, and the amount of elastic hollow microspheres is 2% of the resin system mass. Stir (500 rpm) for at least 30 min to initially disperse the filler and elastic microspheres. Then add the photoinitiator (2% of the resin system mass), defoamer BYK-024 (0.3% of the resin system mass), and leveling agent BYK-333 (0.2% of the resin system mass), and continue stirring for 10 min. Then transfer the system to a high-speed disperser and disperse at a temperature below 50°C using a high-speed disperser (3000 rpm) for at least 30 min to ensure uniform dispersion of all components and no obvious agglomeration. After dispersion, the material is successively ground by a three-roll mill (grinding gap 50μm), vacuum degassing (vacuum degree -0.09MPa, time 20min), and filtered through a 100-mesh filter to remove large particulate impurities and air bubbles, resulting in a uniform and stable tough support layer slurry with a viscosity controlled at 50-80mPa·s.

[0081] During spraying, the preparation of the base solution and the spraying method of the superhydrophobic photothermal layer suspension are the same as in Example 1. After forming base layer 1 and cooling to room temperature, the toughness support layer slurry is sprayed using electrostatic spraying. The spraying pressure is 0.35-0.45 MPa, the spraying distance is 25-30 cm, and the dry film thickness is controlled at 3-5 μm. After spraying, ultraviolet irradiation is applied first, with an ultraviolet light intensity of 80 mW / cm² and an irradiation time of 30 s, to quickly cure the slurry surface and avoid defects such as sagging and pinholes during subsequent thermal curing. After surface curing, the photovoltaic glass is transferred to a constant temperature oven and then thermally cured at 90-105℃ for 60 min to fully cross-link the resin system and form a dense and highly tough toughness support layer 3. The thermal curing temperature is controlled at 90-105℃ to avoid resin degradation caused by high temperature, while ensuring the stability of the hollow structure of the elastic hollow microspheres and their elastic buffering effect.

[0082] After the tough support layer 3 cools to room temperature, the superhydrophobic photothermal layer suspension is sprayed onto the surface of the tough support layer 3.

[0083] The performance of the self-cleaning nanocoating prepared in this embodiment was tested, and the results are as follows:

[0084] The interfacial adhesion between the base layer 1 and the tough support layer 3, and between the tough support layer 3 and the superhydrophobic photothermal layer 2, is ≥5B, with no interlayer delamination.

[0085] Overall impact resistance of the coating ≥ 60 kg·cm;

[0086] Abrasion resistance (steel wool friction) ≥30,000 times with no obvious scratches;

[0087] No brittleness at extreme low temperatures of -40℃; after 500 freeze-thaw cycles (-40℃ to 25℃), the hydrophobicity retention rate is ≥92%; after UV aging (2000h), the adhesion retention rate is ≥93%.

[0088] The photothermal conversion efficiency and anti-icing performance of the superhydrophobic photothermal layer 2 are consistent with those of Example 1, which can meet the stringent requirements for long-term service of photovoltaic panels in high-altitude and cold regions.

[0089] Example 3

[0090] The self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions in this embodiment, such as Figure 3 As shown, the structure includes a base layer 1, a tough support layer 3, a superhydrophobic photothermal layer 2, and a sliding film layer 4, arranged sequentially. The superhydrophobic photothermal layer 2 is connected to the sliding film layer 4 via dot-coated high-hardness UV resin anchor points 5. The base layer 1, tough support layer 3, and superhydrophobic photothermal layer 2 are the same as in Example 2, and the sliding film layer 4 is a methylphenyl silicone resin or fluorosilicone resin film with a thickness of 1-3 μm.

[0091] At night, with no light and lower temperatures, near-infrared absorbing tungsten bronze nanoparticles cannot generate heat, weakening their anti-icing and de-icing effects. To ensure effective anti-icing and de-icing at night, this embodiment incorporates a sliding film layer 4 connected to the surface of the superhydrophobic photothermal layer 2 via dot-coated high-hardness UV resin anchor points 5. The spacing between the high-hardness UV resin anchor points 5 can be 200 μm, and each anchor point 5 has a diameter of 10-50 μm and a thickness of 3-5 μm. A gap exists between the sliding film layer 4 and the superhydrophobic photothermal layer 2, containing air. When wind blows across the surface of the sliding film layer 4, it generates a shear force parallel to the superhydrophobic photothermal layer 2, causing local deformation and slippage of the sliding film layer 4, thus disrupting the bond between the ice crystals and the sliding film layer 4.

[0092] In the absence of wind or with a light breeze, the slip film layer 4 is connected to the high-hardness UV resin anchor point 5 to maintain stability.

[0093] When the wind speed is ≥3m / s and the wind blows parallel to the surface of the slip film layer 4, or at an angle of 0°-60° to the surface of the slip film layer 4, a shear force parallel to the slip film layer 4 is generated on the slip film layer 4. Since the slip film layer 4 is only fixed by sparse micro anchors, the film will undergo overall micro-slip under the shear force (the displacement is about 1-10μm, determined by the spacing between the high-hardness UV resin anchors 5). If there is already an ice layer on the slip film layer 4, when the slip film layer 4 undergoes micro-slip, a shear force is applied to the bottom of the ice layer. This shear force can effectively break the mechanical interlocking and intermolecular adhesion between the ice crystals and the surface of the slip film layer 4. With the assistance of the wind, the ice layer on the surface of the slip film layer 4 can detach naturally, achieving de-icing. If an ice layer has not yet formed, the continuous micro-movement of the slip film layer 4 can also disrupt the stable adhesion state of supercooled water droplets on the film surface, preventing the supercooled water droplets from accumulating and freezing, thus achieving active anti-icing from the source. After the wind stops, the elasticity of the sliding film layer 4 and the constraint of the high-hardness UV resin anchor point 5 restore it to its original position.

[0094] High-altitude, cold regions frequently experience strong winds. This invention can make full use of wind power for active de-icing and active prevention of icing, enhancing the anti-icing and de-icing performance in low-temperature environments at night, and helping to ensure the coating's anti-icing and de-icing effect throughout the day.

[0095] The methylphenyl silicone resin or fluorosilicone resin film itself is superhydrophobic, forming a double-layer superhydrophobic structure with the superhydrophobic photothermal layer 2. Furthermore, due to the presence of air gaps below the slip film layer 4, the actual contact area between liquid water and the coating surface is further reduced, thereby further reducing the overall roll angle of the coating. The hydrophobic performance is superior to that of Example 2.

[0096] Methylphenyl silicone resin or fluorosilicone resin has excellent light transmittance, with a transmittance of ≥90% in the 400-2500nm wavelength band. Simultaneously, the dry film thickness is strictly controlled at 1-3μm, far less than the near-infrared light penetration threshold, ensuring that it does not block near-infrared (700-2500nm) sunlight from reaching the surface of the superhydrophobic photothermal layer 2. The photothermal conversion efficiency of the near-infrared absorbing tungsten bronze nanoparticles is almost unaffected. Although an air gap exists between the slip film layer 4 and the superhydrophobic photothermal layer 2, and air is a poor conductor of heat, this gap is extremely thin. The heat generated by the superhydrophobic photothermal layer 2 can be effectively transferred to the surface of the slip film layer 4, effectively increasing the thickness of the water film in the ice pre-melting layer.

[0097] In addition, the slip film layer 4 plays a physical isolation role, preventing ice crystals from intruding into the multi-level micro-nano rough structure of the superhydrophobic photothermal layer 2 and avoiding the risk of damage to the hydrophobic structure of the superhydrophobic photothermal layer 2.

[0098] The preparation method of the self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions in this embodiment is as follows: First, the method of Example 2 is followed to obtain a base layer 1, a tough support layer 3, and a superhydrophobic photothermal layer 2. Then, a high-hardness UV resin in a dot array is coated on the surface of the superhydrophobic photothermal layer 2, and the high-hardness UV resin is cured by ultraviolet irradiation to obtain high-hardness UV resin anchors 5. Specifically, a UV resin adhesive (a mixture of high-hardness UV resin and UV photoinitiator 184 at a mass ratio of 100:3) is dot-applied to the surface of the superhydrophobic photothermal layer 2 using a dispensing machine. The anchors formed by the coating are spaced 200 μm apart, have a diameter of 10-50 μm, and a thickness of 3-5 μm. After coating, ultraviolet light irradiation (intensity 100 mW / cm², time 60 s) is used for curing to form high-hardness UV resin anchors 5, ensuring a firm bond with the superhydrophobic photothermal layer 2, while ensuring the hardness and uniform distribution of the anchors, providing stable support for the sliding thin film layer 4.

[0099] Methylphenyl silicone resin or fluorosilicone resin was diluted with methyl ethyl ketone (MEK) at a mass ratio of 1:2. After adding 0.2% leveling agent BYK-333, the organic solvent solution of methylphenyl silicone resin or fluorosilicone resin was spin-coated onto the surface of the superhydrophobic photothermal layer 2 and the high-hardness UV resin anchor points 5 using electrostatic spraying. The spraying pressure was 0.2-0.3 MPa, the spraying distance was 30-40 cm, and the dry film thickness was controlled at 1-3 μm. After spraying, the photovoltaic glass was transferred to a constant temperature oven and cured at 80℃ for 30 min, then at 150℃ for 60 min, to obtain a methylphenyl silicone resin or fluorosilicone resin film bonded to the high-hardness UV resin anchor points 5.

[0100] In the superhydrophobic photothermal layer 2, the surface of silica particles naturally contains a large number of silanol groups. Even after modification with low surface energy materials, these silanol groups cannot be completely covered (especially in the gaps and defects of the particles). The molecular chains of high-hardness UV resins (commonly acrylates and epoxy acrylates) contain a large number of unsaturated double bonds, epoxy groups, hydroxyl groups, and other active functional groups. Under ultraviolet irradiation, the photoinitiator in the UV resin decomposes to generate free radicals, which initiate double bond polymerization and cross-linking. At the same time, they undergo free radical grafting reactions or hydrogen bonding with the silanol groups on the surface of the superhydrophobic photothermal layer, forming molecular-level chemical connections. Simultaneously, the high-hardness UV resin penetrates the gaps and pores of multi-level micro-nano rough silica, forming physical interlocking. After curing, the high-hardness UV resin has a high surface energy (usually 30-50 mN / m) and contains active groups such as hydroxyl and ester groups in its molecular chains. It can form hydrogen bonding or weak covalent bonds with the silicon-oxygen bonds in methylphenyl silicone resin or fluorosilicone resin, significantly improving interfacial adhesion. Therefore, the high-hardness UV resin anchor point 5 can stably connect the superhydrophobic photothermal layer 2 and the slip film layer 4.

[0101] The surface energy of the superhydrophobic photothermal layer 2 is extremely low (usually <20 mN / m), while the organic solvent solutions of methylphenyl silicone resin or fluorosilicone resin are low surface energy systems. The interfacial compatibility between the two is poor, making it difficult to form molecular-level adsorption or chemical bonding. Therefore, after the methylphenyl silicone resin or fluorosilicone resin is cured, it is easy to separate from the superhydrophobic photothermal layer 2, resulting in an air-filled gap between the sliding film layer 4 and the superhydrophobic photothermal layer 2.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions, characterized in that: Includes a base layer (1) and a superhydrophobic photothermal layer (2) covering the base layer (1); The base layer (1) includes a silane coupling agent and nano-titanium dioxide sol; The superhydrophobic photothermal layer (2) includes multi-level micro-nano rough silica modified with low surface energy material and near-infrared absorbing tungsten bronze nanoparticles. The low surface energy material includes fluorosilane. The multi-level micro-nano rough silica includes silica microspheres with a particle size of 200-500 nm and silica nanospheres with a particle size of 50-80 nm are attached to the surface of the silica microspheres. A tough support layer (3) is provided between the base layer (1) and the superhydrophobic photothermal layer (2). The tough support layer (3) is a network polymer of polyurethane acrylate and silicone resin, and the network polymer is filled with sheet-like alumina and mica sheets.

2. The self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions as described in claim 1, characterized in that: The near-infrared absorbing tungsten bronze nanoparticles have a particle size of 20-40 nm.

3. The self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions as described in claim 1, characterized in that: Elastic hollow microspheres are added to the tough support layer (3).

4. The self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions as described in claim 1, characterized in that: The surface of the superhydrophobic photothermal layer (2) is connected to the slip film layer (4) by dot-coated high-hardness UV resin anchor points (5); when the wind blows across the surface of the slip film layer (4), it generates a shear force parallel to the superhydrophobic photothermal layer (2) on the slip film layer (4), causing the slip film layer (4) to deform and slip locally, thus breaking the bond between the ice crystal and the slip film layer (4).

5. The self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions as described in claim 4, characterized in that: The slip film layer (4) is a methylphenyl silicone resin or fluorosilicone resin film with a thickness of 1-3 μm.

6. The method for preparing the self-cleaning nano-coating for photovoltaic panels in high-altitude and cold regions as described in claim 1, characterized in that: include Preparation of base solution: Mix silane coupling agent, anhydrous ethanol and deionized water, adjust the pH to 4-5 with acetic acid, and stir to obtain pre-hydrolyzed solution; Nano-titanium dioxide sol was added to the pre-hydrolyzed solution and ultrasonically dispersed to obtain a base solution; Preparation of superhydrophobic photothermal layer suspension: Tetraethyl orthosilicate was added dropwise to an aqueous solution of ethanol at a rate of 2-2.5 mL / min in a water bath at 25±1℃. After the addition was completed, ammonia was added at once, and the reaction was carried out for 6-7 h to obtain silica nanosphere sol. In a water bath at 35±1℃, tetraethyl orthosilicate and ethanol were mixed at a volume ratio of 1:1, and the mixture was added dropwise to silica nanosphere sol at a rate of 1-1.2 mL / min. After the addition was complete, the reaction was allowed to proceed for 12-14 h. After the reaction was completed, the reaction solution was allowed to stand and age at 40-45℃ for at least 24 h. Then, the solid product was separated, washed, and dried to obtain multi-level micro-nano rough silica powder. Multi-level micro-nano rough silica powder and near-infrared absorbing tungsten bronze nanoparticles were mixed, and then the surface was modified with fluorosilane to obtain composite powder. Additives and composite powders are added to a fluorocarbon solvent and dispersed uniformly to obtain a superhydrophobic photothermal layer suspension; Spraying: First, the base solution is sprayed onto the surface of the photovoltaic glass and then heat-treated at a temperature of 120-140℃ to form the base layer (1). Then, a superhydrophobic photothermal layer suspension is sprayed on and sintered and solidified at a temperature of 140-160℃ to obtain a superhydrophobic photothermal layer (2).

7. The preparation method according to claim 6, characterized in that: It also includes the preparation of the toughness support layer slurry: the coupling agent KH-570 is mixed with an ethanol solution, the pH is adjusted to 4-5 with hydrochloric acid, and hydrolysis is carried out for at least 30 min to obtain the coupling agent solution; Flake alumina and mica flakes were added to a coupling agent solution, ultrasonically dispersed for at least 30 minutes, then filtered and dried to obtain a mixed filler. Add methyl ethyl ketone solvent and silicone resin to the reactor, stir evenly at 40°C, then add polyurethane acrylate prepolymer and reactive diluent, heat to 60°C, stir for at least 1 hour to obtain a transparent resin system. Add the mixed filler to the resin system and stir for at least 30 minutes. Then add the photoinitiator, defoamer and leveling agent. Then disperse the mixture at a temperature below 50°C using a high-speed disperser for at least 30 minutes. After dispersion, grind, defoam and filter in sequence to obtain the tough support layer slurry. During spraying, after the base layer (1) is formed, the toughness support layer slurry is sprayed and ultraviolet light is used to cure the surface of the toughness support layer slurry. Then, heat curing is carried out at a temperature of 90-105℃ to obtain the toughness support layer (3). Then, the superhydrophobic photothermal layer suspension is sprayed onto the surface of the toughness support layer (3).

8. The preparation method according to claim 6, characterized in that: After obtaining the superhydrophobic photothermal layer (2), a high-hardness UV resin in a dot array is coated on the surface of the superhydrophobic photothermal layer (2), and the high-hardness UV resin is cured by ultraviolet irradiation to obtain high-hardness UV resin anchors (5). An organic solvent solution of methylphenyl silicone resin or fluorosilicone resin is spin-coated onto the surface of the superhydrophobic photothermal layer (2), and then cured at 80-150℃ for 1-2 hours to obtain a methylphenyl silicone resin or fluorosilicone resin film connected to the high-hardness UV resin anchor point (5).

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