Integration technology of self-cleaning coating, radiation refrigeration coating and photovoltaic module

Abstract

The invention provides a photovoltaic module with a self-cleaning anti-reflection coating and a radiation refrigeration coating, which comprises cover plate glass, back plate glass and a photovoltaic cell fixed between the cover plate glass and the back plate glass, a TiO2 / SiO2 anti-reflection film is arranged on the surface of the cover plate glass, and TiO2 is arranged on the top surface of the film layer and is directly contacted with air, so that on the basis of keeping the light transmittance of the film system, the radiation refrigeration coating can be directly contacted with the surface of the back plate glass; the surface of the TiO2 thin film has super-hydrophilic and oleophylic double affinity, so that a self-cleaning function is realized, and the power generation efficiency of the photovoltaic module is improved; a radiation refrigeration coating is arranged on the surface of the back plate glass, the temperature of air at the bottom of the coating can be reduced, heat in the cover plate glass and the battery piece can be conveniently conducted to the refrigeration piece and the cooling space, the temperature of the battery piece is reduced, and the power generation efficiency is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic cells, and in particular relates to an integration technology of a self-cleaning anti-reflection coating, a radiation cooling coating and a photovoltaic module. Background Art

[0002] One of the pain points facing the solar photovoltaic power generation industry is that the increase in photovoltaic panel temperature reduces power generation efficiency. Under continuous high temperature weather, the power output of photovoltaic modules shows a negative temperature coefficient relationship. The higher the temperature, the lower the output power, so the power generation will also decrease accordingly. For every 1°C increase in temperature, the output power of photovoltaic panels decreases by 0.35%, and the power generation decreases by 0.35%. The main effects of high temperature on modules are: causing the output power of photovoltaic modules to decrease; forming a thermal shift effect that affects the life of modules; affecting the open circuit voltage and causing insufficient system charging; generating a PID effect that causes module failure; and affecting the service life of the inverter core components.

[0003] Figure 8 The figure below shows the relationship between temperature and component failure rate. It can be seen that temperature has a significant impact on component failure rate. The temperature of solar panels is usually between 15°C and 35°C, during which time the solar cells will produce maximum power generation efficiency. In daily applications, the temperature of solar panels may be as high as 65°C (149°F), at which time the efficiency of solar cells will be hindered. Therefore, lowering the temperature of solar panels can increase output power, keep the system fully charged, increase the service life of core components and assemblies, prevent the PID effect, and thus increase photovoltaic power generation efficiency.

[0004] Radiative cooling is a passive cooling technology that does not consume energy and transmits the energy of an object to the depths of the universe through the atmospheric window (8~13μm) in the form of radiation. One of the main challenges facing radiative cooling technology is its integration with other related technologies, such as solar photovoltaic power generation. So far, no one in the industry has considered integrating radiative cooling coatings with photovoltaic modules to reduce the surface temperature of photovoltaic panels and improve power generation efficiency.

[0005] The second pain point of the photovoltaic power generation industry is that the surface of the photovoltaic panel is polluted, resulting in a 5%-30% reduction in power generation. The precipitation of pollutants on the surface of the photovoltaic panel will mainly affect the transmittance of the photovoltaic glass, the temperature of the glass, and the corrosion of the glass. The photovoltaic industry now suffers economic losses of more than US$5 billion per year due to dust worldwide. At present, pollutants on the surface of photovoltaic panels are mainly removed by means of engineering vehicles, mechanical dust removal, and manual dust removal, which have the disadvantages of high installation and maintenance costs, indirectly increasing the cost of power generation, being subject to large site restrictions, wasting water resources, and only being able to remove large particles of dust. Microparticles of dust are difficult to remove and are easy to scratch the glass of the components. The illuminated TiO2 film has a super-amphiphilic (hydrophilic and lipophilic at the same time) phenomenon: before ultraviolet light irradiation, the titanium atoms are mainly connected by bridging oxygen bonds, which is a hydrophobic structure at this time; when exposed to ultraviolet rays, the bridging oxygen bonds between the titanium atoms will be broken, generating new oxygen vacancies. These newly generated oxygen vacancies combine with free water in the air to form chemically adsorbed water, so that the surface of the TiO2 film will form uniformly distributed nano-hydrophilic micro-regions. At the same time, some of the unbroken bridging oxygen bonds are expressed as lipophilic micro-regions. This makes the TiO2 film surface have both hydrophilic and lipophilic properties.

[0006] Therefore, this special super-amphiphilicity makes TiO2 film have great development prospects in the field of self-cleaning. However, so far, no one has considered using TiO2 film as the outermost layer (i.e., the layer in contact with air) of the anti-reflection film on the glass used in the photovoltaic industry, and the self-cleaning effect of the anti-reflection film has not been considered. Instead, it is common to add a layer of self-cleaning coating of other materials on the anti-reflection film, which increases the production cost and process complexity. For example, the Blue Times Company uses an organic-inorganic hybrid system self-cleaning coating on glass, but the adhesion and durability of the coating on the glass are also problematic. Summary of the invention

[0007] The purpose of the present invention is to provide an integrated technology of a photovoltaic module and its coating, aiming to solve the technical problem that the photovoltaic module has low power generation efficiency under the conditions of high temperature and panel surface pollution.

[0008] In order to achieve the above object, the present invention proposes a photovoltaic module, including a cover glass, a back glass and a battery sheet fixed therebetween, which includes: The surface of the cover glass is provided with a TiO2 / SiO2 composite anti-reflection film; The surface of the back panel glass is provided with a radiation cooling coating, and the radiation cooling coating comprises a selective emission material, a mirror reflection material and a reflection material.

[0009] Optionally, the outermost layer of the TiO2 / SiO2 composite antireflection film is a TiO2 thin film and is in contact with air.

[0010] Optionally, the TiO2 / SiO2 composite antireflection film is prepared by vapor deposition or solution method.

[0011] Optionally, the selective emission material of the radiation cooling coating is a material with high emissivity in the atmospheric window band, mainly including materials containing Si elements (such as SiO2), materials containing C elements (such as SiC) and metal oxides such as Al2O3.

[0012] Optionally, the specular reflective material of the radiation cooling coating includes one or more of Al, Cu, and Ag, so as to enhance the reflection of the visible band of sunlight.

[0013] Optionally, the reflective material of the radiation cooling coating is a material with high reflectivity in the solar radiation band, such as one or more of TiO2, HfO2, ZrO2, Nb2O5, Ta2O5, and MgF2.

[0014] Optionally, the radiation cooling coating film system is a composite of 200±5 nm Al / 54±5 nm SiO2 / 34±5 nm TiO2 / 73±5 nm SiO2 / 13±5 nm TiO2 / 688±5 nm SiO2 / 485±5 nm TiO2 / 230±5 nm SiO2, where the numbers represent the thickness of each film layer and its error.

[0015] Optionally, the composite structure is prepared by a vapor deposition method or a solution method.

[0016] In the technical solution of the present invention, a TiO2 / SiO2 composite anti-reflection film is provided on the surface of the cover glass. In this way, while maintaining the transmittance of the TiO2 / SiO2 anti-reflection film system, the dual affinity of the TiO2 film surface, both hydrophilic and lipophilic, is utilized to achieve a self-cleaning function, thereby improving the power generation efficiency of the photovoltaic module. At the same time, the radiation cooling coating on the surface of the back glass is utilized to reduce the temperature of the air (cooling space) at the bottom of the coating, which is beneficial to the conduction of heat from the self-cleaning glass and the battery cell to the cooling plate and the cooling space, thereby reducing the temperature of the battery cell and further improving the power generation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1This is a schematic diagram of the structure of a traditional double-glass photovoltaic module, in which 1 is a cell, 2 is a cover glass, 3 is an anti-reflective coating on the cover glass, and 4 is a blank back glass; Figure 2 This is a diagram of the use state of an embodiment of the photovoltaic module provided by the present invention, in which 1 is a cell, 2 is a cover glass, 4 is a self-cleaning anti-reflection coating on the cover glass, 3 is a blank back glass, and 5 is a radiation cooling coating; Figure 3 It is a schematic diagram of the structure of sample 1; Figure 4 It is a schematic diagram of the structure of sample 2; Figure 5 It is a schematic diagram of the structure of sample 3; Figure 6 It is a schematic diagram of the structure of sample 4; Figure 7 is the transmittance curve of TiO2 / SiO2 anti-reflection film glass substrate; Figure 8 This is the relationship diagram between temperature and component failure rate; Fig. 9 This is the heat transfer process of the radiation cooling coating.

[0019] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] In order to better describe and illustrate the embodiments of the present application, reference may be made to one or more drawings, but the additional details or examples used to describe the drawings should not be considered as limiting the scope of the invention of the present application, any of the currently described embodiments or preferred methods.

[0022] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "top", "bottom", "inside" and "outside" are based on the positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention. They do not indicate that the device referred to must have a specific direction or operate in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0024] As the temperature of photovoltaic panels increases, the power generation efficiency decreases. In continuous high temperature weather, the power output of photovoltaic modules shows a negative temperature coefficient relationship. The higher the temperature, the lower the output power, so the power generation will also decrease accordingly. In addition, if pollutants settle on the surface of photovoltaic panels, it will affect the transmittance of photovoltaic glass, glass temperature, and glass corrosion. The contamination of the photovoltaic panel surface will lead to a 5%-30% reduction in power generation.

[0025] In view of this, the present invention proposes a photovoltaic module. Figure 2 For a structural diagram of an embodiment of a photovoltaic module provided by the present invention, please refer to Figure 2 The photovoltaic cell assembly includes a cover glass 2, a back glass 3 and a cell fixed therebetween, wherein the surface of the cover glass 2 is provided with a TiO2 / SiO2 composite anti-reflection film 4, which is a composite of a TiO2 film and a SiO2 film; the surface of the back glass 3 is provided with a radiation cooling coating 5, which includes an emitting material, a reflecting material and a mirror reflecting material.

[0026] In the technical solution of the present invention, a TiO2 / SiO2 composite antireflection film 4 is provided on the surface of the cover glass 2. In this way, while maintaining the transmittance of the TiO2 / SiO2 antireflection film system, the dual affinity of the TiO2 film surface for both hydrophilicity and lipophilicity is utilized to achieve a self-cleaning function, thereby improving the power generation efficiency of the photovoltaic module. At the same time, the radiation cooling coating 5 on the surface of the back glass 3 is utilized to reduce the temperature of the air (cooling space) at the bottom of the coating, which is beneficial for the heat inside the self-cleaning glass and the battery cell to be transferred to the cooling film and the cooling space, thereby reducing the temperature of the battery cell and thus improving the power generation efficiency. The combination of the two structures has a relatively high power generation efficiency of the photovoltaic module provided by the present invention. Figure 1 The performance of ordinary photovoltaic modules in the industry has been greatly improved.

[0027] It should be noted that, in one embodiment of the present invention, the outermost layer of the TiO2 / SiO2 composite antireflection film 4 is a TiO2 film in contact with the air; the innermost layer is a SiO2 film in contact with the cover glass 2. The self-cleaning antireflection coating glass formed in this way, while maintaining the high transmittance of the TiO2 / SiO2 antireflection film, utilizes the dual affinity of hydrophilicity and lipophilicity on the surface of the TiO2 film to achieve a self-cleaning function, thereby improving the power generation efficiency of the photovoltaic module. Among them, the TiO2 / SiO2 composite antireflection film 4 is prepared by vapor deposition or solution method, and is a thin film generated on the substrate of the cover glass 2.

[0028] In order to perform radiation cooling on the back of the cell, in one embodiment of the present invention, the radiation cooling coating includes a selective emission material, a mirror reflection material and a reflective material. The selective emission material of the coating is a material with high emissivity in the atmospheric window band, mainly including materials containing Si elements (such as SiO2), materials containing C elements (such as SiC) and metal oxides such as Al2O3. The mirror reflection material of the coating includes one or more of Al, Cu, and Ag, which are used to enhance the reflection of the visible band of sunlight. The reflective material of the coating is a material with high reflectivity in the solar radiation band, such as one or more of TiO2, HfO2, ZrO2, Nb2O5, Ta2O5, and MgF2. The coating film system is a composite of 200±5 nm Al / 54±5 nm SiO2 / 34±5 nm TiO2 / 73±5 nm SiO2 / 13±5 nm TiO2 / 688±5 nm SiO2 / 485±5 nm TiO2 / 230±5 nm SiO2, where the numbers represent the thickness of each layer and its error. The coating is prepared by vapor deposition or solution method.

[0029] The radiation cooling coating 5 is arranged on the back plate glass 3 at the bottom of the photovoltaic cell to form a cooling sheet, which is used to replace the traditional blank glass on the back of the photovoltaic module. The cooling sheet can be used to reduce the temperature of the air (cooling space) at the bottom of the coating, which is beneficial for the heat inside the self-cleaning glass and the cell to be transferred to the cooling sheet and the cooling space, thereby reducing the temperature of the photovoltaic module and improving the power generation efficiency.

[0030] Among them, in the radiation cooling coating 5: SiO2 emission material can be replaced by other materials containing Si element (quartz, etc.), materials containing C element (SiC, etc.) and metal oxide materials such as Al2O3; TiO2 reflection material can be replaced by HfO2, ZrO2, Nb2O5, Ta2O5, MgF2 and other materials; Al mirror reflection material can be replaced by high reflectivity metals such as Cu or Ag. The radiation cooling material structure also includes structural materials, meta-structure materials (Raylink film), etc.

[0031] In addition, the surface of the reflective heat-insulating layer in the radiation cooling coating 5 can be in contact with the back glass 3 at the bottom of the cell, or it can be in contact with the air. In this embodiment, the reflective heat-insulating layer Al film is provided on the back glass 3, and the SiO2 film is in contact with the air. It should be noted that the above-mentioned coating is prepared by vapor deposition or solution method, and the substrate is the back glass 3.

[0032] Radiative cooling relies on the optical properties of the material itself to dissipate heat outward, which can achieve passive cooling without consuming any energy. The basic idea is that objects on the earth emit 8~13 μm thermal radiation to the cosmic black body with a temperature close to absolute zero (3K) to achieve the purpose of cooling. The basic principle of the technology can be found in Fig. 9(Radiative cooling heat transfer process): Radiative heat transfer is one of the three basic heat transfer methods (conduction, convection, and radiation). Any object with a temperature greater than absolute zero will emit energy outward in the form of electromagnetic radiation. Radiative heat transfer does not depend on the medium and is not limited by distance. The outer space of the earth is a black body with a temperature of 3 K. Objects on the surface of the earth can dissipate heat to it through radiative heat transfer. The radiation wavelength is in the infrared band, with a wavelength range of 8~13 μm. The temperature of the earth's surface is kept within the habitable range and does not drop to the same temperature as outer space. On the one hand, it is because of the heat radiated by the sun, and on the other hand, it is because of the radiation of the surrounding atmospheric environment. In addition, there is convective heat transfer of the surrounding air. When the radiative cooling device reflects most of the incident sunlight, radiative cooling can be used during the day.

[0033] The materials used in the radiative cooling device should have high emissivity in the long-wave thermal radiation band (8~13 μm) and high reflectivity in the solar radiation band (0.3~2.5 μm) (therefore, the radiative cooling coating cannot be placed on the top of the cell, otherwise it will affect the cell's absorption of sunlight). The radiation characteristics of the radiative cooling surface are the key factors in whether it can achieve refrigeration and achieve a good cooling effect. Radiative cooling materials are composed of materials with different functions, mainly including the following three parts.

[0034] ①Select the launch material Selective emission materials are materials with high emissivity in the atmospheric window band, mainly including materials containing Si elements (such as SiO2), materials containing C elements, and metal oxides such as Al2O3. This is the core difference from ordinary metal reflectors and dielectric reflectors. These two conventional reflectors do not contain selective emission materials, so they do not have high emissivity and radiation cooling effects in the long-wave thermal radiation band (8~13 μm).

[0035] ②Reflective materials Reflective materials are materials with high reflectivity in the solar radiation band, mainly including TiO2, HfO2, ZrO2, Nb2O5, Ta2O5, MgF2, etc.

[0036] ③Mirror reflective material Specular reflective materials mainly include Al, Ag, Cu, etc., which are used to enhance the reflection of the visible band of sunlight. Although ordinary metal reflectors or dielectric reflectors also have these specular reflective materials or reflective materials, they do not combine the two. Therefore, the reflectivity of ordinary metal reflectors or dielectric reflectors to the solar radiation band (0.3~2.5 μm) is not as high as that of the radiation cooling coating. The settings of ② and ③ are mainly to reflect sunlight, and the radiation cooling coating can be used to cool photovoltaic panels during the day.

[0037] The present invention also proposes a coating for photovoltaic modules, that is, the above-mentioned radiation cooling coating 5, which is arranged on the back plate glass 3 of the photovoltaic cell. The coating is an Al film with a thickness of 195~205 nm / 49~59 nm SiO2 film / 29~39 nmTiO2 film / 68~78 nm SiO2 film / 8~18 nm TiO2 film / 683~693 nm SiO2 film / 480~490 nm TiO2 film / 225~235 nm SiO2 film, and the coating structure is prepared by vapor deposition or solution method.

[0038] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention. Example 1

[0039] Figure 7 The transmittance curve of the glass substrate with TiO2 / SiO2 anti-reflection film prepared by physical vapor deposition of the present invention (the horizontal axis is the wavelength of light, in nm, and the vertical axis is the transmittance T%). The transmittance with the anti-reflection film is 5% higher than that of the pure glass substrate on average, meeting the requirements for the use of photovoltaic cells. At the same time, the contact layer between the anti-reflection film and the air is a TiO2 film, which is an anatase nanocrystalline structure and has super hydrophilicity and self-cleaning effects.

[0040] Figure 3-6 They are photovoltaic cell samples 1-4 of photovoltaic modules. The above samples 2-4 were placed in an outdoor environment for 2 months and then the on-site cleaning effects were tested and recorded. It was found that the module samples 2 and 4 of the present invention have good self-cleaning effects and very little dust adheres to the surface. Example 2

[0041] The actual cooling effect of the cooling coating prepared by physical vapor deposition was tested. The photovoltaic cell used was Yike 10 W single crystal panel. Figure 3-6 There are 4 combinations shown in the figure (the cooling plate is the back glass with a radiation cooling coating). The following table shows the field temperature measurement sample combinations and the sample surface and bottom temperatures.

[0042] .

[0043] It can be seen that after adding the cooling sheet, at a similar sample front temperature, the temperature of the bottom surface of the cooling sheet is up to 12°C lower than the sample front temperature. This can increase the battery output power and power generation by 4.2%. The surface and back temperatures of ordinary battery cells are almost the same, which shows that the cooling sheet can significantly reduce the bottom air temperature. In this way, during long-term use, it can help the temperature of the sample front to be quickly transferred to the bottom, thereby reducing the battery cell temperature and improving power generation efficiency.

[0044] The power generation voltage test of samples 2-4 found that the sample voltages all had higher output voltages (18.6V) than sample 1. The higher the output voltage, the greater the power generation efficiency of the component, indicating that the power generation efficiency of component samples 2-4 has been greatly improved. Example 3

[0045] The samples were tested at the second ambient temperature and compared with the Canadian Solar bifacial TOPCon battery module. The table below shows the surface and back temperatures of each sample tested on site. It can be seen that at similar surface temperatures, the back temperature of the photovoltaic module with the addition of cooling film is lower than the surface temperature by up to nearly 9°C, which can increase the output power and power generation of the battery by 3.15%, while the surface and back temperatures of the remaining samples are almost equal.

[0046] .

[0047] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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.

[0048] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A photovoltaic module, comprising a cover glass, a back glass and a cell sheet fixed therebetween, characterized in that: include: The surface of the cover glass is provided with a TiO2 / SiO2 anti-reflection film; The surface of the back panel glass is provided with a radiation cooling coating, and the radiation cooling coating comprises a selective emission material, a reflection material and a mirror reflection material.

2. The photovoltaic module according to claim 1, characterized in that: The outermost layer of the TiO2 / SiO2 antireflection film is a TiO2 thin film and is in contact with the air.

3. The photovoltaic module according to claim 1, characterized in that: The TiO2 / SiO2 antireflection film is prepared by a vapor deposition method or a solution method.

4. The photovoltaic module according to claim 1, characterized in that: The selective emission material of the radiation cooling coating includes one or more of a material containing Si element, a material containing C element and a metal oxide.

5. The photovoltaic module according to claim 1, characterized in that: The specular reflective material of the radiation cooling coating includes one or more of Al, Cu, and Ag.

6. The photovoltaic module according to claim 1, characterized in that: The reflective material of the radiation cooling coating includes one or more of TiO2, HfO2, ZrO2, Nb2O5, Ta2O5, and MgF2.

7. The photovoltaic module according to claim 1, characterized in that: The radiation cooling coating film system is composed of 200±5 nmAl / 54±5 nm SiO2 / 34±5 nm TiO2 / 73±5 nm SiO2 / 13±5 nm TiO2 / 688±5 nm SiO2 / 485±5 nm TiO2 / 230±5 nm SiO2, where the numbers represent the thickness of each film layer and its error.

8. The photovoltaic module according to claim 7, characterized in that: The radiation cooling coating is prepared by vapor deposition or solution method.

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