Anti-reflection sky radiation refrigeration film and preparation method thereof

Abstract

The invention relates to the technical field of sky radiation refrigeration and photovoltaic materials, 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. According to the antireflection sky radiation refrigeration film provided by the invention, the sunlight reflectivity of the photovoltaic panel is reduced, the radiation emissivity of an atmospheric window wave band is improved, and the operating temperature of the photovoltaic panel is effectively reduced, so that the photoelectric conversion efficiency of the photovoltaic panel is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of sky radiation cooling and photovoltaic materials, in particular to an anti-reflection sky radiation cooling film and a preparation method thereof. Background Art

[0002] Photovoltaic technology is an important way to directly convert solar energy into electrical energy, but its efficiency is limited by the loss of sunlight reflection and the increase in operating temperature. The reflection on the surface of photovoltaic cells will reduce the utilization rate of incident light, and the unconverted solar radiation energy will be absorbed in the form of heat, causing the temperature to rise, thereby reducing the photoelectric conversion efficiency of the cell. Studies have shown that the efficiency of crystalline silicon photovoltaic cells decreases by about 0.45% for every 1°C increase in temperature.

[0003] In order 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) band. However, existing sky radiation cooling films have limited temperature reduction effects, affect the absorption rate of photovoltaic panels to sunlight, and have high manufacturing costs, making it difficult to meet practical application needs.

[0004] Patent CN110128688A discloses a radiation cooling film and a preparation method thereof. The radiation cooling film includes a functional coating, a reflective layer and a base layer arranged in sequence from top to bottom. The functional coating is formed by curing a cross-linked resin. Radiation cooling particles are dispersed in the resin of the functional coating. The transmittance of the functional coating in the 300nm to 2500nm band is greater than 80%. The thickness of the functional coating is 2 to 100μm. The emissivity of the radiation cooling film in the 7μm to 14μm band is 70% to 100%. The reflectivity of the radiation cooling film in the 300nm to 2500nm band is greater than 80%. Patent CN116515219B discloses a porous radiation cooling film and a preparation method thereof. The material forms holes inside the film by a solvent volatilization-induced phase separation method. Smaller microspheres can be evenly and randomly distributed in the porous film, establishing an optical structure composed of three media with different optical properties, namely, matrix, microspheres and air, to effectively reflect and absorb radiation in a specific band. At the same time, the microspheres, as particles randomly distributed in the film, absorb, reflect and scatter the radiation projected on their surface. The infrared absorption of the film matrix and the incorporated microspheres makes the film have a high average emissivity in the atmospheric window band.

[0005] Compared with the above two traditional multilayer films (such as gradient refractive index films or composite coatings), the single-layer structure achieves wide-spectrum anti-reflection through multi-scale dispersion of nanoparticles (such as a combination of 12nm and 40nm), simplifies the coating process, and reduces production costs. The present invention also uses common polymer substrates such as PDMS and EVA, combined with SiO 2 、Al 2 O3 Low-cost nanoparticles such as Ag can be used to cool the surface of the radiant cooling film, avoiding the use of precious metals or complex semiconductor materials (such as the ZnO / Ag composite structure used in traditional radiative cooling films).

[0006] In addition, the present invention allows the use of a variety of solvents such as butyl acetate, acetone, tetrahydrofuran, etc. to disperse nanoparticles to adapt to different production conditions. The film thickness (100-400 μm) and curing conditions are compatible with the photovoltaic glass encapsulation process, and no additional complex equipment (such as vacuum coating or photolithography) is required.

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

[0008] To solve the above problems, the present invention proposes an anti-reflective sky radiation cooling film and a preparation method thereof, and the anti-reflective sky radiation cooling film is used for photovoltaic modules. The film significantly improves the photoelectric conversion efficiency of photovoltaic panels by reducing the sunlight reflectivity of photovoltaic panels, increasing the radiation emissivity of the atmospheric window band, and effectively reducing the operating temperature of photovoltaic panels. The specific contents are as follows:

[0009] An anti-reflection sky radiation cooling film, comprising a base material, nanoparticles, a dispersant, and a cross-linking 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 the crosslinking agent to the base material is 1:5-10;

[0013] Nanoparticles come in at least two sizes.

[0014] Preferably, the nanoparticles are selected from Si 3 N 4 、Al 2 O 3 At least one of .

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

[0016] Preferably, the thickness of the film is selected from any value of 100 μm, 200 μm, 300 μm, 400 μm, or any range therebetween.

[0017] Preferably, the base 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 a silane coupling agent, one or more of methyltrichlorosilane, trisilane, and phenyltrichlorosilane.

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

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

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

[0023] S1. placing the photovoltaic encapsulation glass in anhydrous ethanol and performing ultrasonic dust removal treatment;

[0024] S2, adding the nanoparticles into the dispersant, and stirring to obtain a nanoparticle dispersion;

[0025] S3, adding a base material and a cross-linking agent to the nanoparticle dispersion, and stirring to obtain an anti-reflective sky radiation cooling coating;

[0026] S4. Scrape and apply anti-reflection sky radiation cooling coating on the surface of photovoltaic glass, and after curing, form anti-reflection sky radiation cooling film for photovoltaic panels.

[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 knife coating thickness in S4 was 100-400 μm.

[0030] In summary, compared with the conventional technology, the anti-reflection sky radiation cooling film provided by the present invention for photovoltaic panels has high light transmittance, and coating the surface of photovoltaic glass increases the atmospheric window emissivity of the surface by about 13%, improves the radiation heat exchange capacity between the photovoltaic panel and the space, and reduces the working temperature of the photovoltaic panel. After coating the film, the reflectivity of the sunlight on the surface is reduced by about 3%, the ability to absorb sunlight is increased, and the photoelectric conversion efficiency is further enhanced.

[0031] The technical method of the present invention is further described in detail below through the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of an anti-reflective sky radiation cooling film for a photovoltaic panel in an embodiment of the present invention;

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

[0034] Figure 3 300-1100 nm reflectivity spectra comparison of different films in the embodiments of the present invention. DETAILED DESCRIPTION

[0035] The technical method of the present invention is further described below by means of the accompanying drawings and embodiments. It should be noted that unless otherwise specifically stated, the relative arrangement of the components and steps, the numerical expressions and the numerical values ​​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 in nature and is in no way intended to limit the invention, its application, or uses.

[0037] Technologies, systems, and devices known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, systems, and devices should be considered part of the specification.

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

[0039] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0040] Unless otherwise specified, the raw materials and reagents used in the present invention were purchased from commercial sources and used directly without treatment, and the required instruments and equipment adopted the schemes and parameters recommended by the manufacturers.

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

[0042] In view of the problem that the existing photovoltaic panels have reduced efficiency and shortened service life due to high operating temperature and high surface solar radiation reflectivity, the present invention proposes a method of surface-modified anti-reflective sky radiation cooling film to improve the anti-reflectivity of photovoltaic panels and improve the heat exchange performance with 3K deep space, thereby achieving the effect of lowering operating temperature, increasing output power and improving efficiency.

[0043] The present invention is optimized by coating the anti-reflective sky radiation cooling film with different thickness and composition on the surface of the photovoltaic panel, one of which contains 12 nanometers and 3% by mass of SiO 2 The composite film showed superior performance. After testing, the film reduced the operating temperature of photovoltaic panels by 1.74°C, increased the maximum power by an average of 3.98%, and increased the efficiency from 15.86% to 16.49%. In addition, the film also showed good stability and effectiveness under adverse weather conditions (including cloudy and windy weather).

[0044] The anti-reflective sky radiation cooling film provided by the present 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) 10 g of polydimethylsiloxane and 1 g of a cross-linking agent were weighed and stirred at a stirring speed of 800-1600 r / min for 1-2 h to obtain an anti-reflective sky radiation cooling coating.

[0047] (2) Place the photovoltaic encapsulation glass in anhydrous ethanol and ultrasonically clean it for 30 minutes.

[0048] (3) Use a coating machine to apply coating on the photovoltaic glass surface with a thickness of 200 μm.

[0049] (4) After curing, an anti-reflective sky radiation cooling film can be formed on the surface of the photovoltaic glass.

[0050] The film obtained in Example 1 is referred to as Film 1.

[0051] Example 2

[0052] (1) 12 g of polydimethylsiloxane and 1.2 g of a cross-linking agent were weighed and stirred at a stirring speed of 800-1600 r / min for 1-2 h to obtain an anti-reflective sky radiation cooling coating.

[0053] (2) Place the photovoltaic encapsulation glass in anhydrous ethanol and ultrasonically clean it for 30 minutes.

[0054] (3) Use a coating machine to apply coating on the photovoltaic glass surface with a thickness of 300 μm.

[0055] (4) After curing, an anti-reflective sky radiation cooling film can be formed on the surface of the photovoltaic glass.

[0056] The film obtained in Example 2 is referred to as Film 2.

[0057] Example 3

[0058] (1) 14 g of polydimethylsiloxane and 1.4 g of a cross-linking agent were weighed and stirred at a stirring speed of 800-1600 r / min for 1-2 h to obtain an anti-reflective sky radiation cooling coating.

[0059] (2) Place the photovoltaic encapsulation glass in anhydrous ethanol and ultrasonically clean it for 30 minutes.

[0060] (3) Use a coating machine to apply coating on the surface of photovoltaic glass with a thickness of 400 μm.

[0061] (4) After curing, an anti-reflective sky radiation cooling film can be formed on the surface of the photovoltaic glass.

[0062] The film obtained in Example 3 is referred to as Film 3.

[0063] Example 4

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

[0065] (2) 10 g of polydimethylsiloxane and 1 g of a cross-linking agent were weighed and added into the nanoparticle dispersion, and stirred at a stirring speed of 800-1600 r / min for 1-2 h to obtain an anti-reflective sky radiation cooling coating.

[0066] (3) Place the photovoltaic encapsulation glass in anhydrous ethanol and ultrasonically clean it for 30 minutes.

[0067] (4) Use a coating machine to apply coating on the surface of photovoltaic glass with a thickness of 300 μm.

[0068] (5) After the solvent evaporates and solidifies, an anti-reflective sky radiation cooling film can be formed on the surface of the photovoltaic glass.

[0069] The film obtained in Example 4 is referred to as Film 4.

[0070] Example 5

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

[0072] (2) 10 g of polydimethylsiloxane and 1 g of a cross-linking agent were weighed and added into the nanoparticle dispersion, and stirred at a stirring speed of 800-1600 r / min for 1-2 h to obtain an anti-reflective sky radiation cooling coating.

[0073] (3) Place the photovoltaic encapsulation glass in anhydrous ethanol and ultrasonically clean it for 30 minutes.

[0074] (4) Use a coating machine to apply coating on the surface of photovoltaic glass with a thickness of 300 μm.

[0075] (5) After the solvent evaporates and solidifies, an anti-reflective sky radiation cooling film can be formed on the surface of the photovoltaic glass.

[0076] The film obtained in Example 5 is referred to as Film 5.

[0077] Example 6

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

[0079] (2) 10 g of polydimethylsiloxane and 1 g of a cross-linking agent were weighed and added into the nanoparticle dispersion, and stirred at a stirring speed of 800-1600 r / min for 1-2 h to obtain an anti-reflective sky radiation cooling coating.

[0080] (3) Place the photovoltaic encapsulation glass in anhydrous ethanol and ultrasonically clean it for 30 minutes.

[0081] (4) Use a coating machine to apply coating on the surface of photovoltaic glass with a thickness of 300 μm.

[0082] (5) After the solvent evaporates and solidifies, an anti-reflective sky radiation cooling film can be formed on the surface of the photovoltaic glass.

[0083] The film obtained in Example 6 is referred to as Film 6.

[0084] The schematic diagram of the anti-reflection sky radiation cooling film structure for photovoltaic panels obtained in Examples 1-6 is as follows Figure 1 shown.

[0085] Test Example 1

[0086] Ordinary photovoltaic glass is taken without any treatment and is recorded as photovoltaic glass.

[0087] The atmospheric window emissivity and 300-1100nm sunlight reflectivity of films 1-6 and photovoltaic glass were tested and compared. The results are as follows Figure 2 , 3 It can be found that after coating different films on the surface, the emissivity of the atmospheric window increases and the reflectivity of sunlight increases.

[0088] Comparing the atmospheric window (8-13μm) emissivity and the corresponding photoelectric conversion rate of different samples, the results shown in Table 1 are obtained. The anti-reflection sky radiation cooling film used for photovoltaic panels increases the atmospheric window emissivity on the surface by about 13%, improves the radiation heat exchange capacity between photovoltaic panels and space, and reduces the operating temperature of photovoltaic panels. After coating the film, the reflectivity of sunlight on the surface is reduced by about 3%, the ability to absorb sunlight is increased, and the photoelectric conversion efficiency is further enhanced.

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

[0090]

[0091] The anti-reflection sky radiation cooling film selected by the present invention shows a high emissivity in the atmospheric window band (8-13μm), which helps to enhance the radiation cooling capacity of the photovoltaic module, thereby reducing the operating temperature of the photovoltaic module. At the same time, the film effectively suppresses the surface reflection of the photovoltaic glass in the 300nm-1100nm band. The nanoparticle material used has the characteristic that the particle size is much smaller than the wavelength of visible light (400-780nm), so it will not block or scatter visible light in the design, thereby maintaining the high transmittance of the photovoltaic glass. In addition, the film and the photovoltaic glass reduce the equivalent refractive index of the interface through the interference destructive phenomenon, making the refractive index of the glass surface closer to the refractive index of the air. This optimized design can significantly reduce the reflection of sunlight on the surface of the photovoltaic glass, further improve the light absorption efficiency, and enable 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 method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical method of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical method to deviate from the spirit and scope of the technical method of the present invention.

Claims

1. An anti-reflection sky radiation cooling film, characterized in that: Including base material, nanoparticles, dispersant, cross-linking agent; The weight ratio of nanoparticles to dispersant is 1:2-10; Nanoparticles account for 3wt%-9wt% of the total mass; The weight ratio of the crosslinking agent to the base material is 1:5-10; Nanoparticles come in at least two sizes.

2. The anti-reflection sky radiation cooling film according to claim 1, characterized in that: The nanoparticles are selected from at least one of Si3N4 and Al2O3.

3. The anti-reflection sky radiation cooling film according to claim 1, characterized in that: The two sizes are selected from any value of 12 nm, 16 nm, 20 nm, 24 nm, 28 nm, 32 nm, 36 nm, 40 nm, or any range therebetween.

4. The anti-reflection sky radiation cooling film according to claim 1, characterized in that: The thickness of the film is selected from any value of 100 μm, 200 μm, 300 μm, 400 μm, or any range therebetween.

5. The anti-reflection sky radiation cooling film according to claim 1, characterized in that: The base material of the film is selected from at least one of ethylene-vinyl acetate copolymer, polydimethylsiloxane and acrylic resin.

6. The anti-reflection sky radiation cooling film according to claim 1, characterized in that: The dispersant includes one or more of acetone, tetrahydrofuran, and N,N-dimethylformamide.

7. The anti-reflection sky radiation cooling film according to claim 1, characterized in that: The cross-linking agent includes a silane coupling agent, one or more of methyltrichlorosilane, trichlorosilane, and phenyltrichlorosilane.

8. The anti-reflection sky radiation cooling film according to claim 1, characterized in that: The anti-reflection sky radiation cooling film is coated on the surface of the photovoltaic panel to form a modified photovoltaic module; The emissivity of the modified photovoltaic module in the 8-13 μm band is 90-92%.

9. A method for preparing the above-mentioned anti-reflection sky radiation cooling film, characterized in that The steps include: S1. placing the photovoltaic encapsulation glass in anhydrous ethanol and performing ultrasonic dust removal treatment; S2, adding the nanoparticles into the dispersant, and stirring to obtain a nanoparticle dispersion; S3, adding a base material and a cross-linking agent to the nanoparticle dispersion, stirring to obtain an anti-reflective sky radiation cooling coating; S4. Scrape and apply anti-reflection sky radiation cooling coating on the surface of photovoltaic glass, and after curing, form anti-reflection sky radiation cooling film for photovoltaic panels.

10. The anti-reflection sky radiation cooling film and the preparation method thereof according to claim 9, characterized in that: The stirring rate in S2 is 800-1600 r / min, and the stirring time is 1-2 h; The stirring rate in S3 is 800-1600 r / min, and the stirring time is 1-2 h; The knife coating thickness in S4 was 100-400 μm.

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