Glass for photovoltaic module

Abstract

The utility model provides glass for a photovoltaic module, which is arranged on the back surface of a photovoltaic battery piece, a radiation refrigeration coating is arranged on the glass, and the coating is formed by compounding the following film structures: at least one reflecting layer which is one of a metal film and a metal oxide film; and the selective emission layer is arranged on the reflection layer, and the selective emission layer is one or more of a SiO2 film, a SiC film and an Al2O3 film. According to the technical scheme, the radiation refrigeration coating on the surface of the glass is utilized to form the refrigeration sheet, the temperature of air at the bottom of the photovoltaic cell is reduced, heat in the cell can be conducted to the refrigeration sheet and the cooling space, the temperature of the cell is reduced, and the power generation efficiency is further improved.

Description

Technical Field

[0001] This utility model belongs to the field of photovoltaic cell technology, and specifically relates to a glass for photovoltaic modules. Background Technology

[0002] One of the pain points currently facing the solar photovoltaic (PV) power generation industry is that rising PV panel temperatures reduce power generation efficiency. Under sustained high temperatures, PV module power output exhibits a negative temperature coefficient relationship; the higher the temperature, the lower the output power, and therefore, the less power generated. For every 1°C increase in temperature, the PV panel output power decreases by 0.35%, and power generation decreases by 0.35%. The main impacts of high temperatures on modules include: reduced PV module output power; thermal oscillation affecting module lifespan; reduced open-circuit voltage leading to insufficient system charging; PID (PID effect) causing module failure; and reduced lifespan of inverter core components.

[0003] Figure 7 The graph shows the relationship between temperature and component failure rate, demonstrating the significant impact of temperature on component failure rates. Solar panel temperatures typically range between 15°C and 35°C, within which solar cells generate maximum power. In everyday applications, solar panel temperatures can reach as high as 65°C (149°F), at which point solar cell efficiency is hindered. Therefore, reducing solar panel temperature can increase output power, maintain adequate system charging, extend the lifespan of core components and modules, prevent PID effects, and ultimately increase photovoltaic power generation efficiency.

[0004] Radiative cooling is a passive cooling technology that does not consume energy; it transfers the energy of an object into deep space through an atmospheric window (8-13 μm) via radiation. One of the main challenges currently facing radiative cooling technology is its integration with other related technologies, such as solar photovoltaic power generation. To date, no one in the industry has considered integrating radiative cooling coatings with photovoltaic modules to reduce the surface temperature of the photovoltaic panels and improve power generation efficiency. Utility Model Content

[0005] The purpose of this invention is to provide a glass for photovoltaic modules, which aims to solve the technical problem of low power generation efficiency of photovoltaic modules under high temperature conditions.

[0006] To achieve the above objectives, this utility model proposes a glass for photovoltaic modules, disposed on the back of photovoltaic cells, wherein the glass is provided with a radiation-cooling coating, the coating being composed of the following film structure:

[0007] At least one reflective layer, wherein the reflective layer is one of a metal thin film and a metal oxide thin film;

[0008] At least one selective emission layer is disposed above the reflective layer, and the selective emission layer is one or more of SiO2 film, SiC or Al2O3 film.

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

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

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

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

[0013] Optionally, the selective emission layer is a SiO2 film.

[0014] Optionally, the selective emission layer is a SiO2 film.

[0015] Optionally, the coating is a composite structure consisting of an Al film of 195~205nm, a SiO2 film of 49~59nm, a TiO2 film of 29~39nm, a SiO2 film of 68~78nm, a TiO2 film of 8~18nm, a SiO2 film of 683~693nm, a TiO2 film of 480~490nm, and a SiO2 film of 225~235nm.

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

[0017] Optionally, the coating is prepared by physical vapor deposition.

[0018] In the technical solution of this utility model, a radiation cooling coating is provided on the glass surface on the back of the photovoltaic cell. By utilizing the radiation reflection effect of metal thin film and metal oxide thin film and the effect of blocking ultraviolet rays and reducing heat conduction, the temperature of the air (cooling space) at the bottom of the coating is reduced. This facilitates the conduction of heat inside the photovoltaic cell to the back glass, its coating and the cooling space, thereby reducing the temperature of the cell and further improving the power generation efficiency. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of a traditional double-glass photovoltaic module;

[0021] Figure 2 An application state diagram of an embodiment of the photovoltaic module provided by this utility model;

[0022] Figure 3 This is a schematic diagram of the structure of sample 1;

[0023] Figure 4 This is a schematic diagram of the structure of sample 2;

[0024] Figure 5 This is a schematic diagram of the structure of sample 3;

[0025] Figure 6 This is a schematic diagram of the structure of sample 4;

[0026] Figure 7 A graph showing the relationship between temperature and component failure rate;

[0027] Figure 8 This refers to the heat exchange process of the radiation-cooled coating.

[0028] In the figure, photovoltaic cell-1, cover glass-2, back glass-3, TiO2 / SiO2 composite antireflective film-4, and radiation cooling coating-5.

[0029] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] To better describe and illustrate the embodiments of this application, reference may be made to one or more accompanying drawings, but the additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the utility model creation, the embodiments or preferred embodiments of this application, or the preferred methods described herein.

[0032] In the description of this utility model, it should be noted that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and do not indicate that the device referred to must have a specific orientation or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0033] 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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0034] As the temperature of photovoltaic panels rises, their power generation efficiency decreases. Under sustained high temperatures, the power output of photovoltaic modules exhibits a negative temperature coefficient relationship; the higher the temperature, the lower the output power, and therefore the power generation will decrease accordingly.

[0035] In view of this, the present invention proposes a glass for photovoltaic modules. Figure 2 Please refer to the application state diagram of an embodiment of the photovoltaic module glass provided by this utility model. Figure 2 The photovoltaic cell module includes a cover glass 2, a glass 3 with a radiation-cooling coating 5 as provided in this application, and a cell fixed between the two. The cover glass 2 is located on the front side of the cell and has a TiO2 / SiO2 composite antireflection film 4 on its surface, which is composed of a TiO2 thin film and a SiO2 thin film. The glass 3 is located on the back side of the cell and has a radiation-cooling coating 5 on its surface. The radiation-cooling coating 5 includes a reflective layer and a selective emission layer disposed on the reflective layer. Both the reflective layer and the selective emission layer have at least one layer. The reflective layer includes a metal thin film and a metal oxide thin film, and the selective emission layer is one or more of a SiO2 film, SiC, or Al2O3 film.

[0036] It should be noted that metal films have both reflective and heat-insulating effects. Metal films have high reflectivity, reflecting most of the solar radiation back to the external environment, thus reducing heat absorption. Secondly, metal films have good heat-insulating properties, blocking heat conduction. Metal oxide films possess three effects: reflection, absorption, and blocking. They have high reflectivity in the visible and infrared regions, reflecting heat from these wavelengths of sunlight to achieve a heat-insulating effect; they can also absorb heat energy from the infrared and ultraviolet wavelengths of sunlight, thus achieving a heat-insulating effect; and they can block the infrared wavelengths of sunlight to achieve a heat-insulating effect.

[0037] In this invention, a radiation-cooling coating is applied to the surface of the backsheet glass. Utilizing the radiation reflection effect and ultraviolet blocking and heat conduction reduction properties of metal thin films and metal oxide thin films, the temperature of the air at the bottom of the coating (cooling space) is lowered. This facilitates heat transfer from the photovoltaic cells to the backsheet glass, its coating, and the cooling space, thereby reducing the cell temperature and further improving power generation efficiency. The photovoltaic module provided by this invention has a higher power generation efficiency than... Figure 1 Only then could ordinary photovoltaic modules be significantly improved.

[0038] It should be noted that, in one embodiment of this invention, the outermost layer of the TiO2 / SiO2 composite antireflective film 4 is a TiO2 thin film, which is in contact with air; the innermost layer is a SiO2 film, which is in contact with the cover glass 2. This self-cleaning antireflective coating glass, while maintaining the high light transmittance of the TiO2 / SiO2 antireflective film, utilizes the dual hydrophilic and oleophilic affinity of the TiO2 thin film surface to achieve a self-cleaning function, thereby improving the power generation efficiency of the photovoltaic module. The TiO2 / SiO2 composite antireflective film 4 is prepared by physical or chemical vapor deposition and is a thin film formed on the substrate of the cover glass 2.

[0039] To achieve radiative cooling on the back side of the battery cell, in one embodiment of this invention, the metal thin film is one or more of Al, Cu, and Ag films. The metal oxide thin film is one or more of TiO2, HfO2, ZrO2, Nb2O5, Ta2O5, and MgF2 films.

[0040] To protect the coating, in one embodiment of this invention, the emissive layer is selected as one or more of SiO2 film, SiC film, or Al2O3 film. Preferably, both the reflective layer and the selective emissive layer are thin films formed on the substrate of the back glass 3 by vapor deposition.

[0041] To provide better cooling effect for photovoltaic cells, in one embodiment of this utility model, the coating is formed by vapor deposition composite of an Al film with a thickness of 195~205nm, a SiO2 film with a thickness of 49~59nm, a TiO2 film with a thickness of 29~39nm, a SiO2 film with a thickness of 68~78nm, a SiO2 film with a thickness of 8~18nm, a TiO2 film with a thickness of 683~693nm, a SiO2 film with a thickness of 480~490nm, and a SiO2 film with a thickness of 225~235nm.

[0042] As a preferred embodiment, this embodiment provides a radiation-cooling coating 5, which is a coating formed by sequentially depositing and combining 200nm Al film / 54nm SiO2 film / 34nm TiO2 film / 73nm SiO2 film / 13nm TiO2 film / 688nm SiO2 film / 485nm TiO2 film / 230nm SiO2 film structures of different thicknesses through vapor phase deposition. This radiation-cooling coating 5 is disposed on the bottom backplane glass 3 of the photovoltaic cell, forming a cooling element that replaces the traditional blank back glass of the photovoltaic module. This cooling element lowers the temperature of the air (cooling space) at the bottom of the coating, facilitating the conduction of heat from the self-cleaning glass and the cell interior to the cooling element and cooling space, thereby reducing the temperature of the photovoltaic module and improving power generation efficiency.

[0043] In the radiation-cooling coating 5: the SiO2 emitting material can be replaced by other materials containing Si (such as quartz), materials containing C (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; and the Al specular reflective material can be replaced by high-reflectivity metals such as Cu or Ag. The structure of the radiation-cooling material also includes structural materials and metamaterials (Rayling film).

[0044] Furthermore, the surface of the reflective layer in the radiation-cooling coating 5 can be in contact with either the backplane glass 3 at the bottom of the solar cell or with the air. In this embodiment, the reflective Al film is disposed on the backplane glass 3, while the emitting SiO2 film is in contact with the air. It should be noted that the above coating is prepared by physical vapor deposition, and the substrate is the backplane glass 3.

[0045] Radiation cooling relies on the optical properties of materials to dissipate heat outwards, achieving passive cooling without consuming any energy. The basic idea is that objects on Earth emit thermal radiation of 8-13 μm towards a blackbody in space with a temperature close to absolute zero (3 K), achieving cooling. For the basic technical principles, see [link to technical details]. Figure 8 (Radiative Cooling and Heat Transfer Process): Radiative heat transfer is one of the three basic modes of heat transfer (conduction, convection, and radiation). Any object with a temperature above absolute zero will emit energy outward in the form of electromagnetic radiation. Radiative heat transfer is independent of the medium and is not limited by distance. The Earth's outer space is a blackbody with a temperature of 3 K. Objects on the Earth's surface can dissipate heat to it through radiative heat transfer. The radiation wavelength is in the infrared band, ranging from 8 to 13 μm. The Earth's surface temperature is maintained within a habitable range, preventing it from dropping to the same temperature as outer space, due to both solar radiation and radiation from the surrounding atmosphere. Additionally, there is convective heat transfer from the surrounding air. When a radiative cooling device reflects most of the incident sunlight, radiative cooling can be used during the day.

[0046] The materials used in radiative cooling devices 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 top of the solar cell, otherwise it will affect the absorption of sunlight by the solar cell). The radiation characteristics of the radiative cooling surface are a key factor in whether it can achieve cooling and a good cooling effect. The radiative cooling coating is composed of layers of materials with different functions, mainly including the following three parts.

[0047] ①Selection of launch materials

[0048] Selective emissive materials are materials with high emissivity in the atmospheric window band, mainly including materials containing Si (such as SiO2), materials containing C, and metal oxides such as Al2O3. This is the core difference between them and ordinary metal mirrors and dielectric mirrors, which do not contain selective emissive materials and therefore do not have the high emissivity and radiative cooling effect in the long-wave thermal radiation band (8~13 μm).

[0049] ②Reflective materials

[0050] Reflective materials are materials with high reflectivity in the solar radiation band, mainly including TiO2, HfO2, ZrO2, Nb2O5, Ta2O5, MgF2, etc.

[0051] ③ Specular reflective materials

[0052] Specular reflective materials mainly include Al, Ag, and Cu, used to enhance the reflection of visible light. While ordinary metal or dielectric mirrors also possess these specular or reflective materials, they do not combine the two; therefore, their reflectivity for the solar radiation band (0.3~2.5 μm) is lower than that of radiation-cooling coatings. The features ② and ③ primarily reflect sunlight, allowing the radiation-cooling coating to be used for cooling photovoltaic panels during the day.

[0053] The technical solution of this utility model will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain this utility model and are not intended to limit this utility model. Example 1

[0054] The cooling effect of the cooling coating prepared by physical vapor deposition was tested in practice. The photovoltaic cell used was an EKO 10W monocrystalline panel. The sample adopted... Figure 3-6 The table below shows the four combinations (the cooling element is the back glass with a radiation cooling coating), and the sample combinations and the surface and bottom temperatures of the samples measured on site.

[0055] .

[0056] It is evident that with the addition of the cooling chip, at similar sample front temperatures, the temperature of the bottom surface of the cooling chip is reduced by up to 12°C compared to the sample front temperature. This can increase the battery's output power and power generation by 4.2%. In contrast, the surface and back temperatures of ordinary battery cells are almost the same. This indicates that the cooling chip can significantly reduce the bottom air temperature. In the long-term use, this facilitates the rapid conduction of sample front temperature to the bottom, thereby reducing the battery cell temperature and improving power generation efficiency.

[0057] The power generation voltage tests conducted on samples 2-4 revealed that all samples had higher output voltages (18.6V) than sample 1. The higher the output voltage, the greater the power generation efficiency of the module, indicating that the power generation efficiency of module samples 2-4 has been greatly improved. Example 2

[0058] The samples were tested at a second ambient temperature and compared with Canadian Solar's bifacial TOPCon solar cell module. The table below shows the surface and back temperatures of each sample detected on-site. It can be seen that at similar surface temperatures, the back temperature of the photovoltaic module with added cooling chip is nearly 9°C lower than the surface temperature. This can increase the output power and power generation of the cell by 3.15%, while the surface and back temperatures of the other samples are almost equal.

[0059] .

[0060] 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.

[0061] The above embodiments merely illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A type of glass for photovoltaic modules, disposed on the back side of photovoltaic cells, characterized in that, The glass is provided with a radiation cooling coating, which is composed of the following film structures: At least one reflective layer, wherein the reflective layer is one of a metal thin film and a metal oxide thin film; At least one selective emission layer is provided on top of the reflective layer, and the selective emission layer is one or more of SiO2 film, SiC or Al2O3 film; The coating is a composite structure consisting of an Al film of 195~205nm, a SiO2 film of 49~59nm, a TiO2 film of 29~39nm, a SiO2 film of 68~78nm, a TiO2 film of 8~18nm, a SiO2 film of 683~693nm, a TiO2 film of 480~490nm, and a SiO2 film of 225~235nm.

2. The glass for photovoltaic modules as described in claim 1, characterized in that, The coating is a composite structure consisting of a 200nm Al film, a 54nm SiO2 film, a 34nm TiO2 film, a 73nm SiO2 film, a 13nm TiO2 film, a 688nm SiO2 film, a 485nm TiO2 film, and a 230nm SiO2 film.

3. The glass for photovoltaic modules as described in claim 1, characterized in that, The coating was prepared by physical vapor deposition.

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