Glass for photovoltaic modules

Abstract

The present invention provides glass for photovoltaic power generation modules that solves the problem of temperature rise during operation of solar cells and improves power generation efficiency by lowering the cell temperature. [Solution] Glass for a solar photovoltaic module is placed on the backside of a solar cell (1), and the glass is provided with a radiative cooling coating (5). The radiative cooling coating is a composite film structure including at least one reflective layer and at least one selectively emissive layer. The at least one reflective layer is either a metal thin film or a metal oxide thin film. The at least one selectively emissive layer is provided on the reflective layer and is one or more of a SiO2 film, a SiC film, or an Al2O3 film. This invention uses the radiative cooling coating on the glass surface to form a cooling plate, which reduces the air temperature at the bottom of the solar cell. This facilitates heat transfer from inside the cell to the cooling plate and cooling space, reducing the cell temperature and further improving power generation efficiency.

Description

[Technical Field]

[0001] The present invention is in the technical field of photovoltaic cells, and in particular relates to glass for photovoltaic modules. [Background technology]

[0002] One of the challenges currently facing the solar power generation industry is the decline in power generation efficiency due to rising solar panel temperatures. In sustained high-temperature weather, the output power of solar modules exhibits a negative temperature coefficient, meaning that the higher the temperature, the lower the output power. This results in a corresponding decrease in power generation. For every 1°C rise in temperature, the output power of solar panels decreases by 0.35%, and power generation decreases by 0.35%. The main effects of high temperatures on modules are as follows: reduced solar module output, impact on module life due to the tropical effect, insufficient system charging due to effects on open-circuit voltage, module failure due to the PID effect, and impact on the lifespan of key inverter components.

[0003] Figure 7 shows the relationship between temperature and component failure rate, and shows that temperature has a significant impact on component failure rate. Solar panel temperatures are typically between 15°C and 35°C, where solar cells achieve maximum power generation efficiency. During everyday use, panel temperatures can reach 65°C (149°F), which inhibits the efficiency of solar cells. Therefore, lowering the solar panel temperature can increase output power, maintain a sufficient charge in the system, extend the life of core components and modules, and improve solar power generation efficiency by preventing the PID effect.

[0004] Radiative cooling is a passive cooling technology that does not consume energy, transferring the energy of an object in the form of radiation through the atmospheric window (8-13 μm) to deep space. Currently, one of the major challenges facing radiative cooling technology is its integration with related technologies such as solar power generation. Until now, the industry has not considered integrating radiative cooling coatings into solar modules to reduce the surface temperature of the panels and improve power generation efficiency. Summary of the Invention [Problem to be solved by the invention]

[0005] The purpose of this utility model is to provide a glass for a photovoltaic module, and to solve the technical problem of the decrease in power generation efficiency of a photovoltaic module under high temperature conditions. [Means for solving the problem]

[0006] To achieve the above object, this utility model proposes a glass for a photovoltaic module. The glass is placed on the backside of a solar cell and is provided with a radiative cooling coating. The radiative cooling coating is composed of the following film structures in a composite manner:

[0007] At least one reflective layer, which is either a metal thin film or a metal oxide thin film.

[0008] At least one selective emissive layer, the selective emissive layer being disposed on the reflective layer, the selective emissive layer being one or more of a SiO2 film, a SiC film, or an Al2O3 film.

[0009] Optionally, the metal thin film is one or more of an Al film, a Cu film, and an Ag film.

[0010] Optionally, the metal thin film is a Cu film.

[0011] Optionally, the metal oxide thin film is one or more of a TiO2 film, a HfO2 film, a ZrO2 film, a Nb2O5 film, a Ta2O5 film, and a MgF2 film.

[0012] Optionally, the metal oxide thin film is a TiO2 film.

[0013] Optionally, the selectively emissive layer is a SiO2 film.

[0014] Optionally, the selectively emissive layer is a SiO2 film.

[0015] Optionally, the radiative cooling coating is composite with the structure of 195-205nm Al film / 49-59nm SiO2 film / 29-39nm TiO2 film / 68-78nm SiO2 film / 8-18nm TiO2 film / 683-693nm SiO2 film / 480-490nm TiO2 film / 225-235nm SiO2 film.

[0016] Optionally, the radiative cooling coating is composite with a structure of 200nm Al film / 54nm SiO2 film / 34nm TiO2 film / 73nm SiO2 film / 13nm TiO2 film / 688nm SiO2 film / 485nm TiO2 film / 230nm SiO2 film.

[0017] Optionally, the radiative cooling coating is produced by physical vapor deposition. [Effects of the Invention]

[0018] The technical solution of this utility model is to install a radiative cooling coating on the glass surface behind the solar cell, and utilize the radiation reflection, UV blocking and heat conduction reduction effects of the metal thin film and metal oxide thin film to lower the temperature of the air (cooling space) below the radiative cooling coating, which makes it easier for the heat inside the solar cell to be conducted to the backsheet glass, its radiative cooling coating and the cooling space, thereby lowering the cell temperature and further improving power generation efficiency. [Brief explanation of the drawings]

[0019] In order to more clearly describe the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can obtain other related drawings based on these drawings without any creative efforts. [Figure 1] 1 is a structural schematic diagram of a conventional double-sided glass solar cell module. [Figure 2] 1 is an application state diagram of one embodiment of a solar cell module provided by the present invention; [Figure 3] FIG. 1 is a schematic diagram of the structure of Sample 1. [Figure 4] FIG. 1 is a schematic diagram of the structure of Sample 2. [Figure 5] FIG. 1 is a schematic diagram of the structure of Sample 3. [Figure 6] FIG. 1 is a schematic diagram of the structure of Sample 4. [Figure 7] FIG. 10 is a diagram showing the relationship between temperature and component failure rate. [Figure 8] The heat exchange process of the radiative cooling coating is shown. The achievement of the objectives, functional features and advantages of the present invention will be further explained with reference to the embodiments and based on the accompanying drawings. DETAILED DESCRIPTION OF THE INVENTION

[0020] The technical solutions in the embodiments of the present application are clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments. Based on the embodiments of the present application, all other embodiments that can be obtained by those skilled in the art without creative work are included in the protection scope of the present application.

[0021] To better explain the examples of the present application, reference may be made to one or more figures; however, the additional details or examples illustrating the figures should not be construed as limiting the scope of the novelty of the present application or any of the presently described examples or preferred embodiments.

[0022] In describing this utility model, the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inside," "outside," and the like, which indicate orientations or positional relationships, are based on the positional relationships shown in the drawings and are intended to facilitate description of this utility model, but do not indicate that the indicated device must have a particular orientation or operate in a particular orientation, and therefore should not be construed as a limitation on this utility model.

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

[0024] As the temperature of solar panels rises, their power generation efficiency decreases, so under persistently high temperatures, the output power of solar modules exhibits a negative temperature coefficient. The higher the temperature, the lower the output power, and as a result, the amount of power generated also decreases.

[0025] In light of this, this utility model proposes a glass for a solar photovoltaic module. Figure 2 is a diagram showing the use of an embodiment of the glass for a solar photovoltaic module provided by this utility model. Referring to Figure 2, this solar photovoltaic module includes a cover glass 2, a glass 3 provided with a radiative cooling coating 5 provided by the present application, and a cell fixed between the two. Here, the cover glass 2 is disposed on the front side of the cell, and a TiO2 / SiO2 composite anti-reflection coating 4 is disposed on its surface, which is a composite of a TiO2 thin film and an SiO2 thin film. The glass 3 is disposed on the back side of the cell, and a radiative cooling coating 5 is disposed on its surface. The radiative cooling coating 5 includes a reflective layer and a selectively emissive layer disposed on the reflective layer, and each of the reflective layer and the selectively emissive layer has at least one layer. The reflective layer includes a metal thin film and a metal oxide thin film, and the selectively emissive layer is one or more of a SiO2 film, a SiC film, or an Al2O3 film.

[0026] It is important to explain that metal thin films have reflective and heat-blocking effects, and their high reflectivity allows them to reflect most of the solar radiation into the external environment, reducing heat absorption. Furthermore, their excellent heat-blocking performance blocks heat conduction. Metal oxide thin films have three effects: reflection, absorption, and blocking. They exhibit high reflectivity in the visible and infrared light ranges, and achieve heat insulation by reflecting the heat of these wavelengths in sunlight. Furthermore, they achieve heat insulation by absorbing the heat energy of infrared and ultraviolet wavelengths in sunlight, and can also achieve heat insulation by blocking the infrared wavelengths in sunlight.

[0027] In the technical solution of this utility model, a radiative cooling coating is applied to the surface of the backsheet glass, and the temperature of the air (cooling space) below the coating is reduced by utilizing the radiation reflection, UV blocking, and heat conduction reduction effects of the metal thin film and metal oxide thin film. This makes it easier for heat inside the solar cell to be conducted to the backsheet glass, its coating, and the cooling space, reducing the cell temperature and further improving power generation efficiency. The power generation efficiency of the solar module provided by this utility model is significantly improved compared to the conventional solar module shown in Figure 1.

[0028] In one embodiment of this utility model, the outermost layer of the TiO2 / SiO2 composite reflection coating 4 is a TiO2 thin film that is in contact with air. The innermost layer is an SiO2 film that is in contact with the cover glass 2. The self-cleaning reflection-coated glass formed in this manner maintains the high transmittance of the TiO2 / SiO2 reflection coating while utilizing the dual hydrophilic and oleophilic properties of the TiO2 thin film surface to achieve self-cleaning functionality, thereby improving the power generation efficiency of the solar module. Here, the TiO2 / SiO2 composite reflection coating 4 is a thin film fabricated by physical or chemical vapor deposition and formed on the substrate of the cover glass 2.

[0029] In order to perform radiative cooling on the rear surface of the battery cell, in an embodiment of the present invention, the metal thin film is one or more of an Al film, a Cu film, and an Ag film, and the metal oxide thin film is one or more of a TiO2 film, a HfO2 film, a ZrO2 film, a Nb2O5 film, a Ta2O5 film, and an MgF2 film.

[0030] In order to protect the coating, in one embodiment of the present invention, the selectively emissive layer is selected from one or more of SiO2 film, SiC film, and Al2O3 film. Preferably, both the reflective layer and the selectively emissive layer are thin films formed on the substrate of the back-plate glass 3 by vapor deposition.

[0031] In order to provide a good cooling effect to the solar cell, in one embodiment of the present invention, the coating is formed by vapor deposition of a composite structure of 195-205 nm thick Al film / 49-59 nm thick SiO2 film / 29-39 nm thick TiO2 film / 68-78 nm thick SiO2 film / 8-18 nm thick TiO2 film / 683-693 nm thick SiO2 film / 480-490 nm thick TiO2 film / 225-235 nm thick SiO2 film.

[0032] As a preferred embodiment, this example provides a radiative cooling coating 5. This coating is formed by sequentially vapor-depositing layers of different thicknesses: 200 nm Al film, 54 nm SiO2 film, 34 nm TiO2 film, 73 nm SiO2 film, 13 nm TiO2 film, 688 nm SiO2 film, 485 nm TiO2 film, and 230 nm SiO2 film. This radiative cooling coating 5 is placed on the bottom backsheet glass 3 of the solar cell to form a cooling plate. This replaces the conventional backsheet glass of the solar module. The use of this cooling plate reduces the temperature of the air (cooling space) below the coating, facilitating heat transfer from the self-cleaning glass and inside the cell to the cooling plate and cooling space. This reduces the temperature of the solar module and improves power generation efficiency.

[0033] In the radiative cooling coating 5: the SiO2 radiative material can be replaced by other materials containing Si element (such as quartz), materials containing C element (such as SiC), and metal oxide materials such as Al2O3. The TiO2 reflective material can be replaced by materials such as HfO2, ZrO2, Nb2O5, Ta2O5, and MgF2. The Al specular reflective material can be replaced by high-reflectivity metals such as Cu and Ag. The radiative cooling material structure also includes structural materials, metamaterials (relilling films), etc.

[0034] The reflective layer surface of the radiative cooling coating 5 may be in contact with the back plate glass 3 at the bottom of the cell or with the air. In this example, an Al film, which is the reflective layer, is formed on the back plate glass 3, and an SiO2 film, which is the radiative layer, is selected to be in contact with the air. The above coating is formed by physical vapor deposition, and the substrate is the back plate glass 3.

[0035] Radiative cooling utilizes the optical properties of materials to dissipate heat to the outside, achieving passive cooling without consuming any energy. The basic principle is that objects on Earth emit thermal radiation at 8–13 μm wavelengths toward a blackbody in space, which is close to absolute zero (3 K), achieving a cooling effect. The basic principle of the technology is shown in Figure 8 (Radiative Cooling Heat Exchange Process): Radiative heat transfer is one of the three basic heat transfer methods (thermal conduction, convection, and radiation). All objects at temperatures above absolute zero emit energy to the outside in the form of electromagnetic radiation. Radiative heat transfer is medium-independent and not subject to distance limitations. Extraterrestrial space is a blackbody with a temperature of 3 K, and objects on the Earth's surface can dissipate heat to this blackbody through radiative heat transfer. The radiation wavelength is in the infrared range (wavelengths 8–13 μm). The reason the Earth's surface temperature remains in the habitable range and does not drop to the same temperature as outer space is due to heating by solar radiation and radiation from the surrounding atmospheric environment. Convective heat exchange with the surrounding air also plays a role. If the radiative cooling device reflects most of the incident sunlight, radiative cooling can also be used during the daytime.

[0036] The materials used in radiative cooling devices must have high emissivity in the long-wavelength thermal radiation band (8-13 μm) and high reflectivity in the solar radiation band (0.3-2.5 μm) (therefore, radiative cooling coatings cannot be placed on the surface of solar cells, as this would affect the absorption of sunlight). The radiative properties of the radiative cooling surface are the key factor in whether cooling can be achieved and whether a good cooling effect can be achieved. Radiative cooling coatings are made up of a combination of layered films made of materials with different functions, and mainly consist of the following three parts: 1) Selective radiation material Selective radiation materials are materials with high emissivity in the atmospheric window band, and mainly include materials containing Si element (such as SiO2), materials containing C element, and metal oxides such as Al2O3. This is the key difference from conventional metal reflectors and dielectric reflectors; these two types of conventional reflectors do not contain selective radiation materials and therefore do not have high emissivity and radiative cooling effect in the long-wavelength thermal radiation band (8-13μm). 2) Reflective material Reflective materials are materials that exhibit high reflectivity in the solar radiation wavelength range, and mainly include TiO2, HfO2, ZrO2, Nb2O5, Ta2O5, MgF2, etc. 3)Specular reflective material Specular reflective materials are mainly composed of Al, Ag, Cu, etc., and are used to enhance reflection in the visible wavelength range of sunlight. Ordinary metal reflectors and dielectric reflectors also contain these specular and reflective materials, but because they do not combine the two, their reflectivity in the solar radiation wavelength range (0.3 to 2.5 μm) is not as high as that of radiative cooling coatings. The installation of 2) and 3) is primarily to reflect sunlight, which allows radiative cooling coatings to be used to cool solar panels during the day.

[0037] The technical solution of the present invention will be described in more detail with reference to the following specific examples, which should be understood to be for illustrative purposes only and not to limit the present invention. Example 1 A practical cooling effect test was conducted on a cooling coating manufactured by physical vapor deposition. The solar cell used was a Yike 10W monocrystalline panel, and the samples were the four combinations shown in Figure 3-6 (the cooling plate was a back glass with a radiative cooling coating). The table below shows the sample combinations and the temperatures of the top and bottom surfaces of the samples measured in the field. JPEG0003254160000002.jpg46170

[0038] When a cooling plate is added, it was confirmed that the temperature at the bottom of the cooling plate is up to 12°C lower than the surface temperature of the sample, even for similar sample surface temperatures. This results in a 4.2% increase in the battery's output power and power generation. On the other hand, since the temperatures of the top and bottom surfaces of a normal battery cell are roughly the same, it was shown that the cooling plate significantly reduces the bottom air temperature. This allows the sample's surface temperature to be quickly conducted to the bottom surface during long-term use, which is expected to reduce the battery cell temperature and improve power generation efficiency.

[0039] In the power generation voltage test for Samples 2 to 4, all of them showed a higher output voltage (18.6 V) than Sample 1. Since the higher the output voltage, the better the power generation efficiency of the module, it was confirmed that the power generation efficiency of Samples 2 to 4 was significantly improved.

[0040] <Example 2> The samples were measured at a second ambient temperature and compared with Atos' bifacial TOPCon solar module. The table below shows the front and back temperatures of each sample measured in the field. At roughly the same front temperature, it was confirmed that when a cooling plate was added to the solar module, the back temperature was reduced by up to approximately 9°C compared to the front temperature. This resulted in a 3.15% increase in the cell's output power and power generation. Meanwhile, the front and back temperatures of the other samples were roughly the same. JPEG0003254160000003.jpg59170

[0041] The technical features of the above embodiments can be combined in any combination, and 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, it should be considered to be within the scope described in this specification.

[0042] The above examples are specific and detailed descriptions of some embodiments of the present application, and do not limit the scope of the utility model claims. Those skilled in the art may make modifications and improvements without departing from the concept of the present application, and these modifications and improvements are also within the scope of protection of the present application. Therefore, the scope of protection of the present invention is determined by the scope of the attached utility model claims. [Explanation of symbols]

[0043] 1 solar cell 2 Coverslips 3 Backsheet Glass 4 TiO2 / SiO2 composite permeability membrane 5. Radiative cooling coating

Claims

1. A glass for a photovoltaic module, the glass being provided on a back surface of a photovoltaic cell, the glass having a radiative cooling coating provided thereon; The radiation cooling coating is composed of the following film structure in a composite manner: at least one reflective layer, said reflective layer being either a metal thin film or a metal oxide thin film; at least one selectively emissive layer, said selectively emissive layer being disposed on said reflective layer, said selectively emissive layer being made of SiO 2 membrane, SiC membrane or Al 2 O 3 any one or more of the membranes; A glass for a photovoltaic module comprising:

2. 2. The glass for a photovoltaic module according to claim 1, wherein the metal thin film is one or more of an Al film, a Cu film, and an Ag film.

3. 3. The glass for a photovoltaic module according to claim 2, wherein the metal thin film is a Cu film.

4. The metal oxide thin film is TiO 2 membrane, HfO 2 Membrane, ZrO 2 membrane, Nb 2 O 5 Membrane, Ta 2 O 5 Membrane, MgF 2 2. The glass for a photovoltaic module according to claim 1, wherein the glass is one or more of a film.

5. The metal oxide thin film is TiO 2 5. The glass for a photovoltaic module according to claim 4, which is a film.

6. The selective emissive layer is made of SiO 2 2. The glass for a photovoltaic module according to claim 1, wherein the glass is a film.

7. The selective emissive layer is made of SiO 2 7. The glass for a photovoltaic module according to claim 6, which is a film.

8. The radiative cooling coating is a 195-205 nm Al film, a 49-59 nm SiO2 film, and a 29-39 nm TiO 2 Film: 68-78nm SiO 2 Film: 8-18nm TiO 2 Film / SiO 683-693nm 2 Film / 480-490nm TiO 2 Film: 225-235nm SiO 2 2. The glass for a photovoltaic module according to claim 1, characterized in that it is composited into a film structure.

9. The radiative cooling coating is 200nm Al film / 54nm SiO 2 Film / 34nmTiO 2 Film / 73nmSiO 2 Film / 13nmTiO 2 Film / 688nmSiO 2 Film / 485nmTiO 2 Film / 230nmSiO 2 9. The glass for a photovoltaic module according to claim 8, which is composited with a film structure.

10. The glass for a photovoltaic module according to claim 8, characterized in that the radiative cooling coating is produced by physical vapor deposition.

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