Antireflective sky radiation refrigeration film and preparation method thereof

Abstract

The present application relates to the technical fields of sky radiation refrigeration and photovoltaic material, and discloses an antireflection sky radiation refrigeration film and a preparation method thereof, and a modified photovoltaic module formed by coating the antireflection sky radiation refrigeration film on the surface of a photovoltaic panel.The antireflection sky radiation refrigeration film can reduce the solar reflectivity of the photovoltaic panel, improve the radiation emissivity of the atmospheric window band, and effectively reduce the operating temperature of the photovoltaic panel, so as to significantly improve the photoelectric conversion efficiency of the photovoltaic panel.

Description

Technical Field

[0001] This invention relates to the fields of sky radiation cooling and photovoltaic materials technology, and in particular to an anti-reflection sky radiation cooling thin film and its preparation method. Background Technology

[0002] Photovoltaic technology is an important way to directly convert solar energy into electrical energy, but its efficiency is limited by solar radiation reflection losses and increased operating temperature. Surface reflection of photovoltaic cells reduces the utilization rate of incident light, while unconverted solar radiation energy is absorbed as heat, leading to increased temperature and thus reducing the cell's photoelectric conversion efficiency. Studies show that for every 1°C increase in temperature, the efficiency of crystalline silicon photovoltaic cells decreases by approximately 0.45%.

[0003] To reduce the temperature of photovoltaic cells, sky radiation cooling technology achieves passive heat dissipation by increasing the emissivity of photovoltaic modules in the atmospheric window (8-13μm) wavelength band. However, existing sky radiation cooling films suffer from limited temperature reduction effects, affect the solar absorption rate of photovoltaic panels, and have high manufacturing costs, making it difficult to meet the needs of practical applications.

[0004] Patent CN110128688A discloses a radiation-cooling thin film and its preparation method. The radiation-cooling thin film comprises, from top to bottom, a functional coating, a reflective layer, and a substrate layer. The functional coating is formed by curing a cross-linked resin, and radiation-cooling particles are dispersed in the resin. The functional coating has a transmittance greater than 80% in the 300nm–2500nm wavelength range, a thickness of 2–100μm, an emissivity of 70%–100% in the 7μm–14μm wavelength range, and a reflectivity greater than 80% in the 300nm–2500nm wavelength range. Patent CN116515219B discloses a porous radiation-cooling thin film and its preparation method. This material uses a solvent evaporation-induced phase separation method to form pores inside the film. Small microspheres can be uniformly and randomly distributed within the porous film, establishing an optical structure composed of a matrix, microspheres, and air—three media with different optical properties—for effective reflection and absorption of radiation in specific wavelength ranges. Meanwhile, as particles randomly distributed in the thin film, microspheres absorb, reflect, and scatter radiation projected onto their surface. The infrared absorption of the thin film matrix and the microspheres gives the thin film a high average emissivity in the atmospheric window band.

[0005] Compared to the two traditional multilayer films mentioned above (such as gradient refractive index films or composite coatings), the single-layer structure achieves broad-spectrum antireflection through multi-scale dispersion of nanoparticles (such as a combination of 12nm and 40nm), simplifying the coating process and reducing production costs. This invention also uses common polymer substrates such as PDMS and EVA, combined with low-cost nanoparticles such as SiO2 and Al2O3, avoiding the use of precious metals or complex semiconductor materials (such as the ZnO / Ag composite structure used in traditional radiation cooling films).

[0006] In addition, this invention allows the use of various solvents such as butyl acetate, acetone, and tetrahydrofuran to disperse nanoparticles, adapting to different production conditions. The film thickness (100-400μm) and curing conditions are compatible with photovoltaic glass encapsulation processes, eliminating the need for additional complex equipment (such as vacuum deposition or photolithography).

[0007] Therefore, the purpose of this invention is to optimize the thin film performance to achieve a balance between cooling and photoelectric conversion efficiency. Summary of the Invention

[0008] To address the aforementioned problems, this invention proposes an anti-reflection sky radiation cooling film and its preparation method, which is used in photovoltaic modules. This film significantly improves the photoelectric conversion efficiency of photovoltaic panels by reducing the solar reflectivity, increasing the radiative emissivity in the atmospheric window band, and effectively reducing the operating temperature of the photovoltaic panels. Details are as follows:

[0009] A cooling film for reducing sky radiation reflection includes a substrate material, nanoparticles, a dispersant, and a crosslinking agent;

[0010] The weight ratio of nanoparticles to dispersant is 1:2-10;

[0011] Nanoparticles account for 3wt%-9wt% of the total mass;

[0012] The weight ratio of crosslinking agent to substrate material is 1:5-10;

[0013] Nanoparticles have at least two sizes.

[0014] Preferably, the nanoparticles are selected from at least one of Si3N4 and Al2O3.

[0015] Preferably, the two dimensions are selected from any value of 12nm, 16nm, 20nm, 24nm, 28nm, 32nm, 36nm, 40nm, or any range between the two.

[0016] Preferably, the thickness of the film is selected from any value among 100μm, 200μm, 300μm, and 400μm, or any value between the two.

[0017] Preferably, the substrate material of the film is selected from at least one of ethylene-vinyl acetate copolymer, polydimethylsiloxane, and acrylic resin.

[0018] Preferably, the dispersant includes one or more of acetone, tetrahydrofuran, and N,N-dimethylformamide.

[0019] Preferably, the crosslinking agent includes one or more of silane coupling agents, such as methyltrichlorosilane, propane, and phenyltrichlorosilane.

[0020] Preferably, the anti-reflective sky radiation cooling film is coated onto the surface of the photovoltaic panel to form a modified photovoltaic module;

[0021] The modified photovoltaic module has an emissivity of 90-92% in the 8-13μm wavelength band.

[0022] A method for preparing the above-mentioned anti-reflection sky radiation cooling thin film includes the following steps:

[0023] S1. Place the photovoltaic encapsulation glass in anhydrous ethanol for ultrasonic dust removal.

[0024] S2. Add the nanoparticles to the dispersant and stir to obtain a nanoparticle dispersion.

[0025] S3. Add substrate material and crosslinking agent to nanoparticle dispersion and stir to obtain anti-reflection sky radiation cooling coating;

[0026] S4. Apply an anti-reflective sky radiation cooling coating to the surface of the photovoltaic glass, and after curing, form an anti-reflective sky radiation cooling film for the photovoltaic panel.

[0027] Preferably, the stirring rate in S2 is 800-1600 r / min, and the stirring time is 1-2 h;

[0028] The stirring rate in S3 is 800-1600 r / min, and the stirring time is 1-2 h;

[0029] The coating thickness in S4 is 100-400 μm.

[0030] In summary, the anti-reflective sky radiation cooling film and its preparation method of the present invention, compared with traditional technologies, provide an anti-reflective sky radiation cooling film for photovoltaic panels with high light transmittance. Coating the photovoltaic glass surface increases the surface's atmospheric window emissivity by approximately 13%, improving the radiative heat exchange capacity between the photovoltaic panel and outer space, and reducing the operating temperature of the photovoltaic panel. Furthermore, after coating, the surface's solar reflectivity is reduced by approximately 3%, increasing the ability to absorb sunlight and further enhancing photoelectric conversion efficiency.

[0031] The technical method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the anti-reflection sky radiation cooling film used in a photovoltaic panel in an embodiment of the present invention;

[0033] Figure 2 This is a comparison of the infrared emissivity spectra of different thin films at the atmospheric window in the embodiments of the present invention;

[0034] Figure 3 This is a comparison of the reflectance spectra of different thin films in the 300-1100 nm range in the embodiments of the present invention. Detailed Implementation

[0035] The technical method of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the present invention.

[0036] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0037] Techniques, systems, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the instruction manual.

[0038] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0039] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0040] Unless otherwise specified, all raw materials and reagents used in this invention are commercially available and used directly without processing. The required instruments and equipment adopt the manufacturer's recommended schemes and parameters.

[0041] Unless otherwise specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0042] To address the issues of reduced efficiency and shortened lifespan of existing photovoltaic panels due to high operating temperatures and high surface solar radiation reflectivity, this invention proposes a method of surface modification to create an anti-reflective cooling film for sky radiation. This method aims to improve the anti-reflectivity of the photovoltaic panel and enhance its heat exchange performance with 3K deep space, thereby achieving the effects of reducing operating temperature, increasing output power, and improving efficiency.

[0043] This invention optimizes the cooling process by coating photovoltaic panels with anti-reflective sky radiation cooling films of varying thicknesses and compositions. One such film, containing 12 nanometers of SiO2 composite material with a mass fraction of 3%, exhibits superior performance. Testing showed that this film reduced the photovoltaic panel's operating temperature by 1.74°C, increased the average maximum power by 3.98%, and improved the efficiency from 15.86% to 16.49%. Furthermore, the film demonstrated good stability and effectiveness even under adverse weather conditions, including cloudy and windy weather.

[0044] The anti-reflection sky radiation cooling film provided by this invention not only effectively solves the thermal management and reflection problems of photovoltaic panels, but also provides innovative ideas for the design and efficiency improvement of photovoltaic materials, and has broad application prospects and practical value.

[0045] Example 1

[0046] (1) Weigh 10g of polydimethylsiloxane and 1g of crosslinking agent, and stir at a stirring speed of 800-1600r / min for 1-2h to obtain anti-reflection sky radiation cooling coating.

[0047] (2) Place the photovoltaic encapsulation glass in anhydrous ethanol for ultrasonic cleaning for 30 minutes.

[0048] (3) Apply a coating to the surface of the photovoltaic glass using a coating machine to achieve a thickness of 200 μm.

[0049] (4) After curing, a cooling film that reduces the reflection of sky radiation can be formed on the surface of the photovoltaic glass.

[0050] The film obtained from Example 1 is denoted as film 1.

[0051] Example 2

[0052] (1) Weigh 12g of polydimethylsiloxane and 1.2g of crosslinking agent, and stir at a stirring speed of 800-1600r / min for 1-2h to obtain anti-reflection sky radiation cooling coating.

[0053] (2) Place the photovoltaic encapsulation glass in anhydrous ethanol for ultrasonic cleaning for 30 minutes.

[0054] (3) Apply a coating to the surface of the photovoltaic glass using a coating machine to achieve a thickness of 300 μm.

[0055] (4) After curing, a cooling film that reduces the reflection of sky radiation can be formed on the surface of the photovoltaic glass.

[0056] The film obtained from Example 2 is denoted as film 2.

[0057] Example 3

[0058] (1) Weigh 14g of polydimethylsiloxane and 1.4g of crosslinking agent, and stir at a stirring speed of 800-1600r / min for 1-2h to obtain anti-reflection sky radiation cooling coating.

[0059] (2) Place the photovoltaic encapsulation glass in anhydrous ethanol for ultrasonic cleaning for 30 minutes.

[0060] (3) Apply a coating to the surface of the photovoltaic glass using a coating machine to achieve a thickness of 400 μm.

[0061] (4) After curing, a cooling film that reduces the reflection of sky radiation can be formed on the surface of the photovoltaic glass.

[0062] The film obtained from Example 3 is denoted as film 3.

[0063] Example 4

[0064] (1) Weigh 0.3g of 12nm SiO2 particles; add 40ml of butyl acetate and stir at a stirring speed of 800-1600r / min for 1-2h to obtain a nanoparticle dispersion.

[0065] (2) 10g of polydimethylsiloxane and 1g of crosslinking agent are added to the nanoparticle dispersion and stirred at a stirring speed of 800-1600r / min for 1-2h to obtain anti-reflection sky radiation cooling coating.

[0066] (3) Place the photovoltaic encapsulation glass in anhydrous ethanol for ultrasonic cleaning for 30 minutes.

[0067] (4) Apply a coating to the surface of the photovoltaic glass using a coating machine to achieve a thickness of 300 μm.

[0068] (5) After the solvent evaporates and solidifies, a cooling film that reduces the reflection of sky radiation can be formed on the surface of the photovoltaic glass.

[0069] The film obtained from Example 4 is denoted as film 4.

[0070] Example 5

[0071] (1) Weigh 0.6g of 12nm SiO2 particles; add 40ml of butyl acetate and stir at a stirring speed of 800-1600r / min for 1-2h to obtain a nanoparticle dispersion.

[0072] (2) 10g of polydimethylsiloxane and 1g of crosslinking agent are added to the nanoparticle dispersion and stirred at a stirring speed of 800-1600r / min for 1-2h to obtain anti-reflection sky radiation cooling coating.

[0073] (3) Place the photovoltaic encapsulation glass in anhydrous ethanol for ultrasonic cleaning for 30 minutes.

[0074] (4) Apply a coating to the surface of the photovoltaic glass using a coating machine to achieve a thickness of 300 μm.

[0075] (5) After the solvent evaporates and solidifies, a cooling film that reduces the reflection of sky radiation can be formed on the surface of the photovoltaic glass.

[0076] The film obtained from Example 5 is designated as film 5.

[0077] Example 6

[0078] (1) Weigh 0.9g of 12nm SiO2 particles; add 40ml of butyl acetate and stir at a stirring speed of 800-1600r / min for 1-2h to obtain a nanoparticle dispersion.

[0079] (2) 10g of polydimethylsiloxane and 1g of crosslinking agent are added to the nanoparticle dispersion and stirred at a stirring speed of 800-1600r / min for 1-2h to obtain anti-reflection sky radiation cooling coating.

[0080] (3) Place the photovoltaic encapsulation glass in anhydrous ethanol for ultrasonic cleaning for 30 minutes.

[0081] (4) Apply a coating to the surface of the photovoltaic glass using a coating machine to achieve a thickness of 300 μm.

[0082] (5) After the solvent evaporates and solidifies, a cooling film that reduces the reflection of sky radiation can be formed on the surface of the photovoltaic glass.

[0083] The film obtained from Example 6 is designated as film 6.

[0084] Schematic diagrams of the anti-reflection sky radiation cooling thin film structures for photovoltaic panels obtained in Examples 1-6 are shown below. Figure 1 As shown.

[0085] Test Example 1

[0086] Ordinary photovoltaic glass without any processing is referred to as photovoltaic glass.

[0087] The atmospheric window emissivity and 300-1100nm solar reflectivity of thin films 1-6 and photovoltaic glass were compared and tested. The results are as follows: Figure 2 , 3 As shown, it can be observed that the atmospheric window emissivity increases after coating the surface with different thin films, and the solar reflectivity partially increases.

[0088] By comparing the changes in the emissivity and corresponding photoelectric conversion efficiency of the atmospheric window (8-13 μm) of different samples, the results are shown in Table 1 below. The anti-reflective sky radiation cooling film used for photovoltaic panels increases the emissivity of the atmospheric window by approximately 13%, improving the radiative heat exchange capacity between the photovoltaic panel and outer space, and reducing the operating temperature of the photovoltaic panel. Furthermore, after coating with the film, the surface solar reflectivity is reduced by approximately 3%, increasing the ability to absorb sunlight and further enhancing the photoelectric conversion efficiency.

[0089] Table 1 Comparison of photoelectric conversion efficiencies of different thin films

[0090]

[0091] The anti-reflective sky radiation cooling film selected in this invention exhibits high emissivity in the atmospheric window band (8-13 μm), which helps enhance the radiative cooling capacity of photovoltaic modules, thereby reducing the operating temperature of the photovoltaic modules. Simultaneously, the film effectively suppresses surface reflection of photovoltaic glass in the 300nm-1100nm wavelength band. The nanoparticle material used has a particle size much smaller than the visible light wavelength (400-780nm), therefore it does not block or scatter visible light in the design, thus maintaining the high transmittance of the photovoltaic glass. Furthermore, through destructive interference, the film and photovoltaic glass reduce the equivalent refractive index of the interface, making the refractive index of the glass surface closer to that of air. This optimized design significantly reduces the reflection of sunlight on the photovoltaic glass surface, further improving light absorption efficiency, enabling the photovoltaic panel to capture more solar energy more efficiently, thereby improving the photoelectric conversion efficiency of the photovoltaic module.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical methods of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical methods of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical methods to deviate from the spirit and scope of the technical methods of the present invention.

Claims

1. A cooling thin film for reducing sky radiation reflection, characterized in that, Including substrate materials, nanoparticles, dispersants, and crosslinking agents; The weight ratio of nanoparticles to dispersant is 1:2-10; Nanoparticles account for 3wt%-9wt% of the total mass; The weight ratio of crosslinking agent to substrate material is 1:5-10; The nanoparticles are selected from at least one of Si3N4 and Al2O3; the nanoparticles have at least two sizes; The substrate material is ethylene-vinyl acetate copolymer, polydimethylsiloxane, or acrylic resin; the dispersant includes one or more of acetone, tetrahydrofuran, and N,N-dimethylformamide; the crosslinking agent includes one or more of silane coupling agents, methyltrichlorosilane, and phenyltrichlorosilane. The anti-reflection sky radiation cooling film is coated on the surface of photovoltaic encapsulation glass to form a modified photovoltaic module; The modified photovoltaic module has an emissivity of 90-92% in the 8-13μm wavelength band; The two sizes are selected from 12nm, 16nm, or a range between the two; The preparation method of the above-mentioned anti-reflection sky radiation cooling film includes the following steps: S1. Place the photovoltaic encapsulation glass in anhydrous ethanol for ultrasonic dust removal. S2. Add the nanoparticles to the dispersant and stir to obtain a nanoparticle dispersion; the stirring rate in S2 is 800-1600 r / min and the stirring time is 1-2 h; S3. Add the substrate material and crosslinking agent to the nanoparticle dispersion and stir to obtain the anti-reflection sky radiation cooling coating; the stirring rate in S3 is 800-1600 r / min and the stirring time is 1-2 h; S4. Apply an anti-reflective sky radiation cooling coating to the surface of the photovoltaic encapsulation glass, and after curing, form an anti-reflective sky radiation cooling film for the photovoltaic encapsulation glass; the coating thickness in S4 is 100-400μm.

2. The anti-reflection sky radiation cooling film according to claim 1, characterized in that, The thickness of the film is selected from any value among 100μm, 200μm, 300μm, and 400μm, or any value between two of them.

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