Passive photovoltaic system for reducing the temperature of a photovoltaic device

Abstract

The present application relates to a kind of photovoltaic system for passively reducing photovoltaic device temperature, including photovoltaic module, the backboard of the photovoltaic module is provided with radiation refrigeration layer, the back light side of the photovoltaic module is non-contact with antireflection element, and the antireflection element is used to reflect the thermal radiation emitted by the photovoltaic module;Wherein, the solar spectrum weighted reflectivity of radiation refrigeration layer in 0.3 μm-2.5 μm wave band is 90% or more, the 300K blackbody weighted emission rate of radiation refrigeration layer in 2.5 μm-20 μm wave band is 90% or more, and the average reflectivity of antireflection element in 0.3 μm-20 μm wave band is 90% or more.The present application expands the heat dissipation path of photovoltaic system by setting radiation refrigeration layer on the backboard of photovoltaic module and non-contact setting antireflection element on the back light side of photovoltaic module, and significantly improves the heat dissipation effect of photovoltaic system.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and in particular to a photovoltaic system that passively reduces the temperature of photovoltaic devices. Background Technology

[0002] As a key renewable energy solution, photovoltaic technology's conversion efficiency and lifespan are significantly limited by operating temperature. For example, for mainstream silicon solar cells, the relative efficiency decreases by 4% to 5% for every 10-degree Celsius increase in operating temperature, and the lifespan is also significantly shortened.

[0003] To address the issue of temperature rise, passive radiation cooling technology has attracted much attention due to its potential to operate around the clock without external energy consumption. This technology utilizes the "atmospheric transparency window" (8-13μm) band to directly discharge heat into the cold outer space in the form of thermal radiation.

[0004] However, research on radiative cooling of photovoltaic systems mainly focuses on spectral engineering modifications to the top surface of the cells to improve their infrared emissivity. But this approach has significant limitations: on the one hand, the encapsulation materials of commercial photovoltaic modules (such as glass and ethylene-vinyl acetate) already have a high emissivity of over 0.8 in the infrared band, leaving very little room for further improvement; on the other hand, this also results in poor cooling performance of radiative cooling technology based on the modification of the top surface of the cells in practical applications, usually below 2°C, which is difficult to meet the needs of industrial applications.

[0005] Therefore, overcoming technical bottlenecks and designing a solution that can significantly enhance the cooling effect of photovoltaic systems is of great practical significance and application value for improving photovoltaic power generation efficiency and extending the lifespan of photovoltaic devices. Summary of the Invention

[0006] Therefore, it is necessary to provide a photovoltaic system that passively reduces the temperature of photovoltaic devices. By expanding the heat dissipation path of photovoltaic modules, the upper limit of traditional radiation cooling can be broken through, and the heat dissipation effect of the photovoltaic system can be significantly improved.

[0007] This invention provides a photovoltaic system for passively reducing the temperature of photovoltaic devices, including a photovoltaic module. The backsheet of the photovoltaic module is provided with a radiation cooling layer, and the back side of the photovoltaic module is provided with a non-contact reflector for reflecting the thermal radiation emitted by the photovoltaic module.

[0008] The radiation-cooling layer has a solar spectral weighted reflectivity of over 90% in the 0.3μm-2.5μm band, a 300K blackbody weighted emissivity of over 90% in the 2.5μm-20μm band, and an average reflectivity of over 90% in the 0.3μm-20μm band.

[0009] In one embodiment, the orthogonal projection of the reflector onto the plane of the photovoltaic module covers the photovoltaic module.

[0010] In one embodiment, the orthographic projection area of ​​the reflector on the plane of the photovoltaic module is larger than the area of ​​the photovoltaic module.

[0011] In one embodiment, the reflective surface of the reflector is a planar structure, and the angle between the reflective surface of the reflector and the backsheet of the photovoltaic module is 0° to 90°.

[0012] In one embodiment, the reflective surface of the reflector is a curved structure, and the heights of both ends of the reflector are flush with the heights of both ends of the backsheet of the photovoltaic module.

[0013] In one embodiment, the reflector is made of metal.

[0014] In one embodiment, the reflector includes a substrate having a metal reflective layer on its surface.

[0015] In one embodiment, the radiation cooling layer is coated on the backsheet surface of the photovoltaic module;

[0016] Alternatively, the radiative cooling layer can be bonded to the backsheet surface of the photovoltaic module using thermally conductive adhesive.

[0017] In one embodiment, the thickness of the radiative cooling layer is 0.01 mm to 1 mm.

[0018] In one embodiment, the radiation cooling layer is prepared using any of the following methods;

[0019] (1) Mix polyvinylidene fluoride-hexafluoropropylene, water and acetone evenly to obtain a radiation cooling coating. Apply the radiation cooling coating evenly to the back sheet surface of the photovoltaic module and dry it to form a radiation cooling layer.

[0020] (2) Coat the backsheet surface of the photovoltaic module with thermally conductive silicone grease, and attach the silver film to the thermally conductive silicone grease; mix polydimethylsiloxane and curing agent evenly to obtain a precursor solution; coat the precursor solution evenly on the surface of the silver film and dry it to form a radiation cooling layer.

[0021] The photovoltaic system for passively reducing the temperature of photovoltaic devices provided by this invention involves setting a radiative cooling layer on the backsheet of the photovoltaic module and non-contactly setting a reflector on the back side of the photovoltaic module. The radiative cooling layer has high reflectivity and high emissivity, providing a superior radiative cooling effect. At the same time, the reflector has high reflectivity, which can directly dissipate the heat emitted by the photovoltaic module into the cold outer space in the form of thermal radiation. Through the synergistic effect of the two, the heat dissipation path of the photovoltaic system is expanded, breaking through the cooling limit of traditional radiative cooling. The radiative heat dissipation, which is traditionally limited to the top surface of the photovoltaic module, is extended to the back of the photovoltaic module, thereby significantly improving the heat dissipation effect of the photovoltaic system without changing the physical size of the photovoltaic module. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic diagram of a photovoltaic system for passively reducing the temperature of photovoltaic devices, as shown in one embodiment;

[0024] Figure 2 A schematic diagram of a photovoltaic system for passively reducing the temperature of photovoltaic devices, as an alternative embodiment;

[0025] Figure 3 A schematic diagram of a photovoltaic system for passively reducing the temperature of photovoltaic devices, as another embodiment of the invention;

[0026] Figures 4-6 These are schematic diagrams of reflectors with different curved surface structures.

[0027] In the diagram: 1. Reflector; 2. Radiation cooling layer; 3. Photovoltaic module. Detailed Implementation

[0028] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0030] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0031] Combination Figures 1-6 The present invention provides a photovoltaic system for passively reducing the temperature of photovoltaic devices, including a photovoltaic module 3. The back panel of the photovoltaic module 3 is provided with a radiation cooling layer 2, and the back side of the photovoltaic module 3 is provided with a non-contact reflector 1, which is used to reflect the thermal radiation emitted by the photovoltaic module 3.

[0032] The radiation-cooling layer 2 has a solar spectral weighted reflectivity of over 90% in the 0.3μm-2.5μm band, a 300K blackbody weighted emissivity of over 90% in the 2.5μm-20μm band, and an average reflectivity of over 90% in the 0.3μm-20μm band for the reflector 1.

[0033] The photovoltaic system for passively reducing the temperature of photovoltaic devices provided by this invention involves setting a radiative cooling layer 2 on the back panel of the photovoltaic module 3 and non-contactly setting a reflector 1 on the back side of the photovoltaic module 3. The radiative cooling layer 2 has high reflectivity and high emissivity, providing a superior radiative cooling effect. At the same time, the reflector 1 has high reflectivity, which can directly dissipate the heat emitted by the photovoltaic module 3 into the cold outer space in the form of thermal radiation. Through the synergistic cooperation of the two, the heat dissipation path of the photovoltaic system is expanded, breaking through the cooling limit of traditional radiative cooling, breaking conventional thinking, overcoming technical biases, and extending the radiative heat dissipation that is traditionally limited to the top surface of the photovoltaic module 3 to the back surface of the photovoltaic module 3. Thus, without changing the physical size of the photovoltaic module 3, the heat dissipation effect of the photovoltaic system is significantly improved.

[0034] Therefore, the present invention can significantly reduce the temperature of photovoltaic module 3 in a low-cost and high-efficiency manner, and is compatible with current mainstream silicon-based, perovskite, organic solar cells, etc., and can be flexibly adapted to photovoltaic modules 3 of different specifications and sizes.

[0035] It is worth noting that the photovoltaic system of the present invention can also be integrated with traditional cooling technologies (such as air cooling, water cooling, etc.) to form a composite cooling system, thereby further improving the photoelectric efficiency and lifespan of solar cells.

[0036] Optionally, the orthographic projection of the reflector 1 onto the plane of the photovoltaic module 3 preferably covers the photovoltaic module 3, which helps the reflector 1 to more fully dissipate the heat radiation emitted by the photovoltaic module 3.

[0037] Optionally, the orthographic projection area of ​​the reflector 1 on the plane where the photovoltaic module 3 is located is preferably larger than the area of ​​the photovoltaic module 3. For example, the orthographic projection area of ​​the reflector 1 on the plane where the photovoltaic module 3 is located is 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2.0 times, etc., which is beneficial to dissipate the heat radiation emitted by the photovoltaic module 3 and reduce parasitic heat radiation in the environment.

[0038] Optionally, the reflecting surface of the reflector 1 is preferably a planar structure, such as... Figure 1 , Figure 2 As shown, the reflector 1 of the planar structure can be set horizontally or at a certain angle to the horizontal plane. The angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is preferably 0° to 90°, such as 0°, 5°, 10°, 20°, 30°, 40°, 45°, 50°, 60°, 70°, 75°, 80°, 90°, etc., which is beneficial for efficiently collecting and exporting the heat radiation emitted by the photovoltaic module 3, and achieving a more significant temperature reduction effect.

[0039] Optionally, the reflecting surface of the reflector 1 is preferably a curved surface structure, such as... Figures 3-6 As shown, the curved surface structure can be an arc-shaped structure, a broken line structure, or a structure formed by multiple arcs, etc. Preferably, the heights of both ends of the reflector 1 are flush with the heights of both ends of the back panel of the photovoltaic module 3, that is, one end of the reflector 1 and one end of the back panel of the photovoltaic module 3 are at the same height from the ground, and their highest points are flush. Similarly, the other end of the reflector 1 and the other end of the back panel of the photovoltaic module 3 are also at the same height from the ground, and their highest points are also flush. This helps to suppress the entry of environmental heat radiation, promote the heat radiation dissipation of the photovoltaic module 3, and achieve a more significant temperature reduction effect.

[0040] Optionally, the reflector 1 is preferably made of metal. For example, an aluminum plate with high reflectivity can be used as the reflector 1, or other metal plates with high reflectivity can be used. This is beneficial for reflecting solar thermal radiation, ambient thermal radiation and the thermal radiation of the photovoltaic module 3 to the cold outer space, thereby enhancing the heat dissipation effect of the photovoltaic system.

[0041] Optionally, the reflector 1 includes a substrate, which may be made of materials such as plastic. Preferably, a metal reflective layer is provided on the surface of the substrate to reflect heat radiation. The material of the substrate and the material and thickness of the metal reflective layer can be selected according to specific circumstances, which helps to improve the flexibility of selection.

[0042] It is understood that the arrangement of the radiative cooling layer 2 on the backsheet of the photovoltaic module 3 is not particularly limited. It can be coated on the surface of the backsheet of the photovoltaic module 3, or it can be attached to the surface of the backsheet of the photovoltaic module 3 by means of thermally conductive adhesive, as long as the required cooling effect is achieved and the temperature of the photovoltaic module 3 is reduced. When disposed on the surface of the backsheet of the photovoltaic module 3, it can be disposed on the side closer to the photovoltaic cells or on the side away from the photovoltaic cells, preferably on the side away from the photovoltaic cells.

[0043] Optionally, the thickness of the radiative cooling layer 2 is preferably 0.01mm-1mm, such as 0.01mm, 0.03mm, 0.05mm, 0.08mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc., which is beneficial to achieving a better temperature reduction effect.

[0044] Optionally, the radiation cooling layer 2 is preferably prepared by any one of the following methods;

[0045] (1) Mix polyvinylidene fluoride-hexafluoropropylene, water and acetone in a certain proportion to obtain a radiation cooling coating. Apply the radiation cooling coating evenly to the back panel surface of the photovoltaic module 3 and dry it to form a radiation cooling layer 2.

[0046] (2) Coat the backsheet surface of the photovoltaic module 3 with thermally conductive silicone grease, and attach the silver film to the thermally conductive silicone grease; mix polydimethylsiloxane and curing agent in a certain proportion to obtain a precursor solution; coat the precursor solution evenly on the surface of the silver film and dry it to form a radiation cooling layer 2.

[0047] The technical solution of the present invention will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0048] Example 1

[0049] like Figure 1 As shown, this embodiment provides a photovoltaic system for passively reducing the temperature of photovoltaic devices, including a photovoltaic module 3. The photovoltaic module 3 is at an angle of 30° to the horizontal plane. A radiation cooling layer 2 is provided on the back panel of the photovoltaic module 3. The thickness of the radiation cooling layer 2 is 0.2 mm. It is made by coating the back panel of the photovoltaic module 3 with a radiation cooling coating. The preparation method is as follows:

[0050] To prepare a radiation-cooling coating, polyvinylidene fluoride-hexafluoropropylene, water, and acetone were mixed in a mass ratio of 1:1:8 and stirred at a constant temperature of 60°C for 30 minutes to form a homogeneous and transparent solution.

[0051] Coating to form a film; the prepared radiation-cooling coating is uniformly applied to the backsheet surface of photovoltaic module 3.

[0052] The solvent (water and acetone) on the backsheet surface of the photovoltaic module 3 is completely evaporated under normal temperature and pressure, forming a solid radiative cooling layer 2 with a thickness of 0.2 mm on the backsheet surface of the photovoltaic module 3. The radiative cooling layer 2 has a solar spectral weighted reflectance of 93% in the 0.3 μm-2.5 μm band and a 300K blackbody weighted emissivity of 90% in the 2.5 μm-20 μm band.

[0053] The photovoltaic module 3 has a non-contact reflector 1 on its backside. The reflector 1 is used to reflect the heat radiation emitted by the photovoltaic module 3. The reflective surface of the reflector 1 is planar, and the angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is 30°, i.e., parallel to the horizontal plane. The orthographic projection of the reflector 1 on the plane of the photovoltaic module 3 completely covers the photovoltaic module 3. The orthographic projection area of ​​the reflector 1 on the plane of the photovoltaic module 3 is 1.5 times the area of ​​the photovoltaic module 3. The reflector 1 is made of aluminum, and its average reflectivity in the 0.3μm-20μm wavelength band is 94%.

[0054] Example 2

[0055] like Figure 2As shown, the difference between this embodiment and Embodiment 1 is that the angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is different. In this embodiment, the angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is 15°.

[0056] Example 3

[0057] The difference between this embodiment and Embodiment 1 is that the angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is different. In this embodiment, the angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is 45°.

[0058] Example 4

[0059] The difference between this embodiment and Embodiment 1 is that the angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is different. In this embodiment, the angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is 90°.

[0060] Example 5

[0061] The difference between this embodiment and Embodiment 1 is that the angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is different. In this embodiment, the angle between the reflective surface of the reflector 1 and the back panel of the photovoltaic module 3 is 135°.

[0062] Example 6

[0063] The difference between this embodiment and Embodiment 1 is that the orthographic projection of the reflector 1 onto the plane where the photovoltaic module 3 is located does not completely cover the photovoltaic module 3, and the orthographic projection area of ​​the reflector 1 onto the plane where the photovoltaic module 3 is located is 0.5 times the area of ​​the photovoltaic module 3.

[0064] Example 7

[0065] The difference between this embodiment and Embodiment 1 is that the thickness of the radiation cooling layer 2 is 1 mm.

[0066] Example 8

[0067] The difference between this embodiment and Embodiment 1 is that the radiative cooling layer 2 is different. In this embodiment, the radiative cooling layer 2 is a composite structure, which is bonded to the backsheet of the photovoltaic module 3 by thermally conductive adhesive, as follows:

[0068] Thermal grease is applied to the backsheet surface of photovoltaic module 3, and a commercially available silver film is tightly adhered to it, achieving good thermal conduction and mechanical fixation through the thermal grease.

[0069] A precursor solution was prepared by uniformly mixing polydimethylsiloxane (PDMS) and a curing agent at a volume ratio of 10:1.

[0070] The precursor solution was uniformly coated onto the surface of the silver film, and then heated at 60°C for 30 minutes to cure the PDMS, ultimately forming a radiative cooling layer 2 with a thickness of 0.2 mm. The radiative cooling layer 2 is a composite structure with distinct functions. The bottom silver film layer is mainly used to enhance the reflectivity of sunlight, while the top PDMS organic layer serves as an infrared emitting layer. The two work together to achieve efficient radiative cooling performance. The radiative cooling layer 2 has a solar spectral weighted reflectivity of 94% in the 0.3 μm-2.5 μm band and a 300K blackbody weighted emissivity of 93% in the 2.5 μm-20 μm band.

[0071] Example 9

[0072] The difference between this embodiment and Embodiment 1 is that the reflector 1 is different. In this embodiment, the reflector 1 includes a substrate, and the surface of the substrate is provided with a silver reflective layer. The silver reflective layer is prepared by electroplating, and the specific steps are as follows:

[0073] Pretreatment: The substrate (such as an acrylic sheet) is degreased, roughened, sensitized, and activated to enhance the adhesion of subsequent coatings.

[0074] Chemical silver plating: The pretreated substrate is immersed in a chemical silver plating solution, and a conductive silver layer with a thickness of about 1 μm is deposited on the substrate surface as the bottom layer for electroplating through an autocatalytic reaction.

[0075] Electroplating thickening: The substrate with the deposited conductive silver layer is used as the cathode and placed in the silver electroplating solution. A pure silver plate is used as the anode. Electroplating is carried out under controlled current density and temperature conditions until the silver layer thickness reaches 10μm.

[0076] Post-processing: The electroplated substrate is removed, cleaned, passivated, and dried to obtain a bright silver reflective layer.

[0077] The reflector 1 has an average reflectivity of 97% in the 0.3μm-20μm band.

[0078] Example 10

[0079] like Figure 3 As shown, the difference between this embodiment and Embodiment 1 is that the reflector 1 is different. In this embodiment, the reflector 1 has a curved structure, and the two ends of the reflector 1 are flush with the two ends of the back panel of the photovoltaic module 3. The reflector 1 has an average reflectivity of 94% in the 0.3μm-20μm band.

[0080] Example 11

[0081] The difference between this embodiment and embodiment 11 is that the structure of the reflector 1 is different. In this embodiment, the structure of the reflector 1 is as follows: Figure 6 As shown.

[0082] Comparative Example 1

[0083] The difference between Comparative Example 1 and Example 1 is that the thickness of the radiation cooling layer 2 is 0.05 mm, the solar spectral weighted reflectance in the 0.3 μm-2.5 μm band is 83%, and the 300 K blackbody weighted emissivity in the 2.5 μm-20 μm band is 90%.

[0084] Comparative Example 2

[0085] The difference between Comparative Example 2 and Example 1 is that a reflector 1 is not provided on the backlight side of the photovoltaic module 3.

[0086] Comparative Example 3

[0087] The difference between Comparative Example 3 and Example 1 is that no radiative cooling layer 2 is provided on the back sheet of the photovoltaic module 3. The photovoltaic module 3 is prepared by a lamination process: using an ethylene-vinyl acetate copolymer with a thickness of 0.5 mm as an encapsulating film, a polyvinyl fluoride composite film back sheet with a thickness of 0.1 mm is hot-pressed onto the back of the silicon cell at 150°C, and then cooled and cured to form the module. The measured solar spectral weighted reflectance in the 0.3 μm-2.5 μm band is 74%, and the 300K blackbody weighted emissivity in the 2.5 μm-20 μm band is 93%.

[0088] Comparative Example 4

[0089] The difference between Comparative Example 4 and Example 1 is that the reflector 1 has an average reflectivity of 10% in the 0.3μm-20μm band, and the reflector 1 is made of graphite.

[0090] Comparative Example 5

[0091] The difference between Comparative Example 5 and Example 1 is that the solar spectral weighted reflectance of the radiation-cooling layer 2 in the 0.3μm-2.5μm band is 5%, and the preparation method of the radiation-cooling layer 2 is as follows:

[0092] A black precursor solution was prepared by uniformly mixing graphite powder, polydimethylsiloxane (PDMS), and curing agent at a volume ratio of 1:10:1.

[0093] The black precursor solution is uniformly coated onto the backsheet surface of the photovoltaic module 3, and then heated in a 60°C environment for 30 minutes to cure the PDMS, ultimately forming a radiative cooling layer 2 with a thickness of 0.2 mm. The radiative cooling layer 2 is a black material that strongly absorbs sunlight, making it difficult to achieve daytime radiative cooling.

[0094] Comparative Example 6

[0095] The difference between Comparative Example 6 and Example 1 is that the radiative cooling layer 2 has a 300K blackbody weighted emissivity of 5% in the 2.5μm-20μm band, and the radiative cooling layer 2 is a 0.1mm thick commercial aluminum foil, which is attached to the backsheet surface of the photovoltaic module 3 using thermally conductive adhesive.

[0096] Indoor performance tests were conducted on photovoltaic module 3 in the examples and comparative examples. The tests were conducted at a temperature of 30°C and a simulated solar irradiance of 1000 W / m². 2 Under the test conditions, the measured steady-state performance parameters are shown in Table 1.

[0097] Table 1

[0098]

[0099] Table 1 shows that, based on Examples 1-5, the angle between the reflective surface of reflector 1 and the backsheet of photovoltaic module 3 is too large, which is not conducive to achieving a cooling effect; based on Example 6, the area of ​​reflector 1 is too small, resulting in a poor cooling effect; based on Example 7, increasing the thickness of the radiative cooling layer 2 is beneficial to improving the cooling effect; based on Example 8, using different methods to prepare the radiative cooling layer 2, as long as the obtained radiative cooling layer 2 has a solar spectral weighted reflection in the 0.3μm-2.5μm band... Good cooling effect can be achieved if the emissivity and its 300K blackbody-weighted emissivity in the 2.5μm-20μm band meet the requirements. As shown in Example 9, good cooling effect can be achieved by using different reflectors 1 as long as the average emissivity of reflector 1 in the 0.3μm-20μm band meets the requirements. As shown in Examples 10 and 11, the curved surface structure of reflector 1 has a better cooling effect. As shown in Comparative Examples 1-6, the synergistic cooperation between the radiation cooling layer 2 and reflector 1 is the key.

[0100] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0101] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A photovoltaic system for passively reducing the temperature of photovoltaic devices, comprising photovoltaic modules, characterized in that, The backsheet of the photovoltaic module is provided with a radiation cooling layer, and the back side of the photovoltaic module is provided with a non-contact reflector, which is used to reflect the heat radiation emitted by the photovoltaic module. The radiation-cooling layer has a solar spectral weighted reflectivity of over 90% in the 0.3μm-2.5μm band, a 300K blackbody weighted emissivity of over 90% in the 2.5μm-20μm band, and an average reflectivity of over 90% in the 0.3μm-20μm band.

2. The photovoltaic system for passively reducing the temperature of photovoltaic devices according to claim 1, characterized in that, The orthogonal projection of the reflector onto the plane of the photovoltaic module covers the photovoltaic module.

3. The photovoltaic system for passively reducing the temperature of photovoltaic devices according to claim 1, characterized in that, The area of ​​the reflector projected onto the plane of the photovoltaic module is larger than the area of ​​the photovoltaic module.

4. The photovoltaic system for passively reducing the temperature of photovoltaic devices according to claim 1, characterized in that, The reflective surface of the reflector is a planar structure, and the angle between the reflective surface of the reflector and the back panel of the photovoltaic module is 0° to 90°.

5. The photovoltaic system for passively reducing the temperature of photovoltaic devices according to claim 1, characterized in that, The reflective surface of the reflector is a curved structure, and the heights of both ends of the reflector are flush with the heights of both ends of the backsheet of the photovoltaic module.

6. The photovoltaic system for passively reducing the temperature of photovoltaic devices according to claim 1, characterized in that, The reflector is made of metal.

7. The photovoltaic system for passively reducing the temperature of photovoltaic devices according to claim 1, characterized in that, The reflector includes a substrate, and the surface of the substrate is provided with a metal reflective layer.

8. The photovoltaic system for passively reducing the temperature of photovoltaic devices according to claim 1, characterized in that, The radiation cooling layer is coated on the backsheet surface of the photovoltaic module; Alternatively, the radiative cooling layer can be bonded to the backsheet surface of the photovoltaic module using thermally conductive adhesive.

9. The photovoltaic system for passively reducing the temperature of photovoltaic devices according to claim 1, characterized in that, The thickness of the radiation cooling layer is 0.01mm-1mm.

10. The photovoltaic system for passively reducing the temperature of photovoltaic devices according to claim 1, characterized in that, The radiation cooling layer is prepared by any of the following methods; (1) Mix polyvinylidene fluoride-hexafluoropropylene, water and acetone evenly to obtain a radiation cooling coating. Apply the radiation cooling coating evenly to the back sheet surface of the photovoltaic module and dry it to form a radiation cooling layer. (2) Coat the backsheet surface of the photovoltaic module with thermally conductive silicone grease, and attach the silver film to the thermally conductive silicone grease; mix polydimethylsiloxane and curing agent evenly to obtain a precursor solution; coat the precursor solution evenly on the surface of the silver film and dry it to form a radiation cooling layer.

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