KR102514021B1 - Transparent radiative cooling device - Google Patents

Abstract

The present invention is based on a multilayer thin film structure having wavelength-selective optical characteristics in the visible and infrared regions, and can reflect sunlight in the near-infrared region while maintaining transparency and emit radiant heat to effectively lower the temperature compared to conventional glass. More specifically, according to an embodiment of the present invention, the transparent radiation cooling element includes a first reflective layer made of a first transparent radiative cooling material and a second reflective layer made of a second transparent radiant cooling material. Based on the repeatedly stacked multi-layer structure, it is composed of a selective reflective layer and a polymer material that transmits sunlight in the visible light region and reflects at least one of sunlight in the ultraviolet and near-infrared regions. It may include a selective emission layer that absorbs and emits infrared rays in a corresponding wavelength range.

Description

Transparent radiant cooling device {TRANSPARENT RADIATIVE COOLING DEVICE}

The present invention relates to a transparent radiant cooling element capable of adding radiative cooling characteristics while maintaining the appearance of an existing outer wall and exterior material, and provides transparency based on a multilayer thin film structure having wavelength-selective optical characteristics in the visible and infrared regions. A transparent radiation cooling device capable of effectively lowering the temperature compared to conventional glass by reflecting sunlight in the near-infrared region and emitting radiant heat while retaining heat.

Passive Radial Cooling Devices can be passively cooled by reflecting wavelengths (0.3-2.5μm) corresponding to sunlight during the day and emitting radiant heat (8-13μm) energy that can escape into space.

The efficiency of the passive cooling element can be confirmed by measuring the optical characteristics of the element itself.

In order to emit heat, it must be able to emit heat well into space as it has a high absorptivity or emissivity in the long-wavelength infrared region.

According to the Planck distribution, at a temperature of 300K, it has a condition for maximally emitting heat in the wavelength range of 6-20㎛. In the case of the earth, since the sky window region is about 8-13 μm, in order to maximize the heat dissipation capability of the passive cooling device, absorptance or emissivity must be maximized in the 8-13 μm region.

Infrared radiation in the window wavelength range of the atmosphere plays a key role in achieving radiative cooling by substantial heat dissipation. 300K At an ambient temperature of 158 W/m ^{2 ,} cooling performance can be realized without energy consumption.

When 95% of sunlight is reflected and more than 90% of mid-infrared rays in the 8㎛-13㎛ region are radiated to the outside, the cooling performance of 100W/m ² is achieved during the day when the ambient temperature is 300K (that is, the presence of light absorption by the sun). In addition, at night without light absorption by the sun, cooling performance of 120 W/m ² can be realized.

In order to be used as a passive radiation cooling material, it must have high transmittance or high reflectance for light in the wavelength range of UV-vis-NIR, which is incident sunlight, so that it does not absorb incident sunlight, and it must not absorb incident sunlight, and it must have an area of 8 to 13㎛, which is the window section of the atmosphere. It should have a high absorption (emission) rate for long-wavelength infrared rays of the sun, and in addition, it should have high durability (stability, corrosion resistance) in outdoor conditions, and the materials used should be cheap and abundant, and inexpensive and easy to use. It should be possible to form a large area with the process.

In the case of polymer materials, they generally have a high absorptivity (emissivity) for long-wavelength infrared rays, but due to the nature of the material, they are easily deteriorated by ultraviolet rays, moisture, etc. when left outdoors, and have a short lifespan.

In addition, since the thick polymer material is a broadband emitter with high emissivity for all infrared wavelength bands, it has better radiation cooling performance than a selective emitter with high emissivity in the sky window. It falls.

In the case of using a multilayer thin film of inorganic material or ceramic material, the number of layers must be large in order to increase the emissivity of the entire atmospheric window, which increases the solar absorption rate, making it difficult to achieve high efficiency radiant cooling performance.

In addition, radiation cooling elements including a lower metal reflective layer such as silver or aluminum have difficulties in applying radiation cooling in real life due to long-term stability problems (oxidation problems) and unit cost problems of silver and aluminum, and these metal materials mainly reflect specular reflection. This can cause eye strain and glare.

In order to implement daytime radiation cooling, sunlight in the visible, ultraviolet, and near-infrared regions must be maximally reflected to minimize heat inflow, and infrared rays included in the wavelength range corresponding to the atmospheric window must be absorbed and radiated.

In order to implement the radiation cooling device transparently, since only light corresponding to minimum sunlight needs to be introduced, all sunlight in the near-infrared wavelength region must be reflected and sunlight in the visible light region visible to the human eye must be transmitted.

However, there are limitations in the application of a white reflection and scattering layer using a metal or polymer and oxide semiconductor particles in a radiation cooling device according to the prior art.

That is, the radiation cooling device using the conventional white reflection and scattering layer has many limitations in its use in real life.

Korean Patent Registration No. 10-2036071, "Multi-Layer Radiant Cooling Structure" Korean Patent Registration No. 10-1632646, "Inline manufacturing method of solar cell panel" US Patent Publication No. 2020/0095429, "COATING TO COOL A SURFACE BY PASSIVE RADIATIVE COOLING" Korean Patent Registration No. 10-2140669, "Passive radiation cooling structure"

The present invention transmits only sunlight in the visible light region based on a selective reflection layer using a multilayer thin film structure, reflects sunlight in the ultraviolet region and near infrared region, and based on a selective emission layer based on a polymer material, it can be applied to the wavelength range of a window in the atmosphere. It is an object to provide a transparent radiation cooling element that absorbs and emits corresponding infrared rays.

An object of the present invention is to provide a transparent radiation cooling device that cools the ambient temperature without consuming energy even during the day when sunlight shines or at night when sunlight does not shine.

An object of the present invention is to provide a cooling function without consuming energy by being applied to the outer surface of materials requiring cooling, such as building materials, glass, automobile materials, aviation equipment, energy-saving data centers and electronic devices, and solar cells.

An object of the present invention is to provide a transparent radiant cooling device that provides a cooling function without consuming energy while providing aesthetic improvement by using a commercially available paint together with a transparent radiant cooling device.

An object of the present invention is to improve radiation cooling performance by absorbing and emitting infrared rays corresponding to a wavelength range of an atmospheric window while minimizing heat inflow based on a selective reflection layer using a multilayer thin film structure.

According to an embodiment of the present invention, the transparent radiation cooling element is based on a multi-layer structure in which a first reflection layer made of a first transparent radiation cooling material and a second reflection layer made of a second transparent radiation cooling material are repeatedly stacked, and the visible light region is A selective reflective layer that transmits light and reflects at least one of sunlight in the ultraviolet and near-infrared regions and a polymer material that absorbs and emits infrared rays in a wavelength range corresponding to the sky window of the sunlight. A radiation layer may be included.

The selective reflective layer transmits sunlight in the visible region and reflects at least one of sunlight in the ultraviolet region and the near infrared region based on a difference in refractive index between the first transparent radiation-cooling material and the second transparent radiation-cooling material. can

In the selective reflection layer, as a refractive index difference between the first transparent radiation-cooling material and the second transparent radiation-cooling material increases, transmittance of sunlight in the visible region and reflectance of sunlight in the ultraviolet and near-infrared regions may increase. there is.

The selective reflective layer has a cross structure in which the second reflective layer is formed on the first reflective layer and the first reflective layer is formed on the second reflective layer, and the first reflective layer and the second reflective layer are one to five layers. can achieve

Since the selective reflective layer is formed of the first to fifth layers, when the number of layers increases, transmittance of sunlight in the visible light region decreases, reflectance of sunlight in the ultraviolet and near infrared regions increases, and when the number of layers decreases, the transmittance of sunlight in the ultraviolet region and the near infrared region increases. Transmittance of sunlight in the visible light region may increase, and reflectance of sunlight in the ultraviolet and near infrared regions may decrease.

The first reflective layer may have a thickness of 63 nm to 71 nm in relation to the number of layers of the first reflective layer and the second reflective layer, and the thickness of the second reflective layer may be 174 nm.

The first transparent radiant cooling material may include at least one of a-Si:H, TiO ₂ , ITO, SiO ₂ and ZnS.

The second transparent radiant cooling material may include at least one of SiO ₂ , Al ₂ O ₃ , MgF ₂ and Si ₃ N ₄ .

The selective emission layer may be formed of the polymer material including polydimethyl siloxane (PDMS).

The selective emission layer may have a thickness of 50 μm.

According to one embodiment of the present invention, the transparent radiation cooling element may further include a color layer for realizing colors according to the type of color paint on the other side of the transparent substrate positioned below the selective reflection layer.

The selective reflection layer may be positioned between the transparent substrate and the selective emission layer.

The present invention transmits only sunlight in the visible light region based on a selective reflection layer using a multilayer thin film structure, reflects sunlight in the ultraviolet region and near infrared region, and based on a selective emission layer based on a polymer material, it can be applied to the wavelength range of a window in the atmosphere. A transparent radiation cooling element that absorbs and emits corresponding infrared rays can be provided.

The present invention can provide a transparent radiation cooling device that cools the ambient temperature without consuming energy even during the day when sunlight shines or at night when sunlight does not shine.

The present invention can be applied to the outer surface of materials requiring cooling, such as building materials, glass, automobile materials, aviation equipment, energy-saving data centers and electronic devices, and solar cells, to provide a cooling function without consuming energy.

The present invention can provide a transparent radiant cooling device that provides a cooling function without consuming energy while providing aesthetic improvement by using a commercially available paint together with a transparent radiant cooling device.

The present invention can improve radiant cooling performance by absorbing and emitting infrared rays corresponding to a wavelength range of a window in the atmosphere while minimizing heat inflow based on a selective reflection layer using a multilayer thin film structure.

1 illustrates a conceptual diagram of a transparent radiation cooling element according to one embodiment of the present invention.
2 illustrates the structure of a transparent radiation cooling element according to one embodiment of the present invention.
3A and 3B illustrate electron microscope images of a transparent radiation cooling element according to one embodiment of the present invention.
4-5B illustrate the refractive index of a selectively reflective layer of a transparent radiation cooling element according to one embodiment of the present invention.
6 to 10 illustrate radiant cooling characteristics according to structural changes of a selective reflection layer of a transparent radiation cooling device according to an embodiment of the present invention.
11A to 11C explain radiation cooling test results using a transparent radiation cooling device according to an embodiment of the present invention.
11D illustrates an image of a transparent radiant cooling element according to one embodiment of the present invention.
12A and 12B illustrate an embodiment in which a color layer is added to a transparent radiation cooling element according to an embodiment of the present invention.
13A to 13C illustrate radiation cooling test results using a transparent radiation cooling element to which a color layer is added according to an embodiment of the present invention.

Hereinafter, various embodiments of this document will be described with reference to the accompanying drawings.

Examples and terms used therein are not intended to limit the technology described in this document to specific embodiments, and should be understood to include various modifications, equivalents, and/or substitutes of the embodiments.

In the following description of various embodiments, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the invention, the detailed description will be omitted.

In addition, terms to be described below are terms defined in consideration of functions in various embodiments, and may vary according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout this specification.

In connection with the description of the drawings, like reference numerals may be used for like elements.

Singular expressions may include plural expressions unless the context clearly dictates otherwise.

In this document, expressions such as "A or B" or "at least one of A and/or B" may include all possible combinations of the items listed together.

Expressions such as "first," "second," "first," or "second," may modify the corresponding components regardless of order or importance, and are used to distinguish one component from another. It is used only and does not limit the corresponding components.

When a (e.g., first) element is referred to as being "(functionally or communicatively) coupled to" or "connected to" another (e.g., second) element, that element refers to the other (e.g., second) element. It may be directly connected to the component or connected through another component (eg, a third component).

In this specification, "configured to (or configured to)" means "suitable for," "having the ability to," "changed to" depending on the situation, for example, hardware or software ," can be used interchangeably with "made to," "capable of," or "designed to."

In some contexts, the expression "device configured to" can mean that the device is "capable of" in conjunction with other devices or components.

For example, the phrase "a processor configured (or configured) to perform A, B, and C" may include a dedicated processor (eg, embedded processor) to perform the operation, or by executing one or more software programs stored in a memory device. , may mean a general-purpose processor (eg, CPU or application processor) capable of performing corresponding operations.

Also, the term 'or' means 'inclusive or' rather than 'exclusive or'.

That is, unless otherwise stated or clear from the context, the expression 'x employs a or b' means any one of the natural inclusive permutations.

Terms such as '..unit' and '..group' used below refer to a unit that processes at least one function or operation, and may be implemented by hardware or software, or a combination of hardware and software.

1 illustrates a conceptual diagram of a transparent radiation cooling element according to one embodiment of the present invention.

Referring to FIG. 1 , the transparent radiation cooling device 100 according to an embodiment of the present invention transmits the visible light region of incident sunlight, totally reflects at least one of the ultraviolet and near-infrared regions, and has a wavelength range of a window in the atmosphere ( 8-13 μm) absorbs and emits infrared rays.

For example, the transparent radiation cooling device 100 has a structure in which a selective reflection layer and a selective emission layer are sequentially formed on a transparent substrate, and the selective reflection layer is formed of a multilayer structure using transparent radiation cooling materials having different refractive indices.

The transparent radiation cooling device 100 according to an embodiment of the present invention has wavelength-selective optical properties in the visible and infrared regions, reflects sunlight in the near-infrared region while maintaining transparency, and emits radiant heat, so that it can be applied to conventional glass. temperature can be effectively lowered.

In addition, the transparent radiant cooling element 100 can add radiant cooling characteristics while maintaining the appearance of existing outer walls and exterior materials, so it can be easily introduced into existing buildings and vehicles, and when used with paint, a color-customized radiant cooling element can be used as

Therefore, the present invention can be applied to the outer surface of materials requiring cooling, such as building materials, glass, automobile materials, aviation equipment, energy-saving data centers and electronic devices, and solar cells, to provide a cooling function without consuming energy.

In addition, the present invention can provide a transparent radiation cooling device that cools the ambient temperature without consuming energy even during the day when sunlight shines or at night when sunlight does not shine.

2 illustrates the structure of a transparent radiation cooling element according to one embodiment of the present invention.

2 illustrates a stacked structure of a transparent radiation cooling element according to one embodiment of the present invention.

Referring to FIG. 2 , a transparent radiation cooling device 200 according to an embodiment of the present invention includes a transparent substrate 210, a selective reflection layer 220 and a selective emission layer 230, and the selective reflection layer 220 includes It includes a first reflective layer 221 and a second reflective layer 222 .

According to one embodiment of the present invention, the transparent substrate 210 is a substrate made of a transparent material and includes glass.

That is, the transparent substrate 210 may be glass applicable to windows of automobiles and buildings.

According to one embodiment of the present invention, the selective reflection layer 220 has a multilayer structure in which a first reflection layer 221 made of a first transparent radiation cooling material and a second reflection layer 222 made of a second transparent radiation cooling material are repeatedly stacked. Based on this, sunlight in the visible light region may be transmitted, and at least one of sunlight in the ultraviolet region and the near infrared region may be reflected.

For example, the first transparent radiant cooling material may include at least one of a-Si:H, TiO ₂ , ITO, SiO ₂ and ZnS.

Also, the second transparent radiant cooling material may include at least one of SiO ₂ , Al ₂ O ₃ , MgF ₂ and Si ₃ N ₄ .

For example, the selective reflective layer 220 transmits sunlight in a visible light region and reflects at least one of sunlight in an ultraviolet region and a near infrared region based on a difference in refractive index between the first transparent radiation cooling material and the second transparent radiation cooling material. can do.

The selective reflection layer 220 according to an embodiment of the present invention increases the difference in refractive index between the first transparent radiation cooling material and the second transparent radiation cooling material, so that the transmittance of sunlight in the visible light region and the ultraviolet and near-infrared regions are reduced. The reflectance of sunlight may be increased.

A description of the difference in refractive index between the first transparent radiation cooling material and the second transparent radiation cooling material is described with reference to FIGS. 4 to 5B.

According to one embodiment of the present invention, the selective reflective layer 220 is a crossover in which the second reflective layer 222 is formed on the first reflective layer 221 and the first reflective layer 221 is formed on the second reflective layer 222. As a structure, the first reflective layer 221 and the second reflective layer 222 may have one to five layers.

For example, since the selective reflective layer 220 is formed of one to five layers, when the number of layers is increased, transmittance of sunlight in the visible light region may decrease, and reflectance of sunlight in the ultraviolet and near-infrared regions may increase.

In addition, when the number of layers of the selective reflective layer 220 is reduced, transmittance of sunlight in the visible light region may increase, and reflectance of sunlight in the ultraviolet and near-infrared regions may decrease.

According to one embodiment of the present invention, the thickness of the first reflective layer 221 may be determined within a range of 63 nm to 71 nm in relation to the number of layers of the first reflective layer 221 and the second reflective layer 222 .

For example, the second reflective layer 222 may have a thickness of 174 nm.

For example, the selective reflection layer 220 is positioned between the transparent substrate 210 and the selective emission layer 230 .

According to an embodiment of the present invention, the selective emission layer 230 is made of a polymer material and can absorb and emit infrared rays in a wavelength range corresponding to a sky window of incident sunlight.

That is, the selective emission layer 230 may absorb and emit infrared rays of 8 μm to 13 μm corresponding to a wavelength range of a window in the atmosphere from sunlight incident on the transparent radiation cooling device 200 .

For example, the selective emission layer 230 may be formed of a polymer material including polydimethylsiloxane (PDMS).

In addition, the selective emission layer 230 may be formed to a thickness of 50 μm in consideration of characteristics of polydimethylsiloxane (PDMS).

Therefore, the present invention transmits only sunlight in the visible light region based on a selective reflection layer using a multilayer thin film structure, reflects sunlight in the ultraviolet region and near infrared region, and based on a selective emission layer based on a polymer material, the wavelength of a window in the atmosphere It is possible to provide a transparent radiation cooling element that absorbs and emits infrared rays corresponding to a range.

3A and 3B illustrate electron microscope images of a transparent radiation cooling element according to one embodiment of the present invention.

3A illustrates an electron microscope image of a transparent radiation cooling element according to one embodiment of the present invention.

Referring to FIG. 3A , in the transparent radiation cooling device 300 according to an embodiment of the present invention, a selective reflection layer is positioned between a transparent substrate and PDMS corresponding to a selective emission layer, wherein the selective reflection layer is a first reflection layer and a second reflection layer. , the first reflective layer is formed of a-Si:H, and the second reflective layer is formed using SiO ₂ .

The thickness of the first reflective layer was formed to be 70 nm, 63 nm, and 71 nm, and the thickness of the second reflective layer was formed to be 174 nm.

Here, the thickness of the first reflection layer is designed to have high reflectance in the vicinity of 1 μm wavelength, and may be a value obtained by optimizing initial parameters for maximizing transmittance in the visible light region and reflectance of near infrared rays.

That is, the thickness of the first reflection layer may be a value determined to increase transmittance in the visible light region and increase reflectance of near infrared rays.

3B illustrates an electron microscope image of a selective emission layer in a transparent radiation cooling device according to one embodiment of the present invention.

For example, the transparent radiation cooling element 310 has a structure in which only a selective emission layer is formed on a substrate, and the selective emission layer is formed of PDMS and may have a thickness of 50 μm.

4-5B illustrate the refractive index of a selectively reflective layer of a transparent radiation cooling element according to one embodiment of the present invention.

4 illustrates the refractive index of a transparent radiant cooling material forming the selectively reflective layer of a transparent radiative cooling element according to one embodiment of the present invention.

Referring to FIG. 4 , a graph 400 may represent the refractive index of a-Si:H corresponding to amorphous silicon, and a graph 410 may represent the refractive index of SiO ₂ .

According to the graph 400, a-Si:H corresponding to amorphous silicon has a high refractive index with respect to sunlight in the visible light region and the near infrared region.

The solid line of the graph 400 may represent the real part of the refractive index, and the dotted line may represent the imaginary part of the refractive index. Here, the refractive index may be determined by taking the square root of the permittivity value.

According to the graph 410, SiO ₂ has a relatively low refractive index compared to a-Si:H with respect to sunlight in the visible and near infrared regions.

A-Si:H and SiO ₂ , which are materials constituting the selective reflection layer according to an embodiment of the present invention, may have a large difference in refractive index.

That is, as the difference in refractive indices of the two materials constituting the selective reflection layer increases, the transmittance of sunlight in the visible light region may be improved, and the reflectance of sunlight in the ultraviolet and near-infrared regions may be improved.

FIG. 5A shows sunlight in the ultraviolet region, near infrared region, and visible region when a-Si:H and Si ₃ N ₄ are used as two materials constituting the selective reflection layer of the transparent radiation cooling device according to an embodiment of the present invention. Transmittance (T), reflectance (R) and absorptivity (A) are exemplified in the wavelength range of

Referring to graph 500, the first reflective layer of the selective reflective layer of the transparent radiation cooling device according to an embodiment of the present invention is formed of a-Si:H, the second reflective layer is formed of Si ₃ N ₄ , and the wavelength It shows high reflectance and low absorption at 1 μm, and low transmittance.

In addition, it can be seen that it shows low reflectance and low absorption at a wavelength of 1.5 μm and high transmittance.

The left vertical axis of the graph 500 represents percentage, 1 represents 100%, and the right vertical axis represents the solar spectrum.

Referring to the graph 501, it can be confirmed that the refractive index of Si ₃ N ₄ forming the second reflective layer is similar to that of SiO ₂ , and it can be confirmed that Si ₃ N ₄ can be used as the second reflective layer.

5B is a case where a-Si:H and Al ₂ O ₃ are used as two materials constituting the selective reflection layer of the transparent radiation cooling device according to an embodiment of the present invention, corresponding to sunlight in the ultraviolet region, near infrared region, and visible region. Transmittance (T), reflectance (R) and absorptivity (A) are exemplified in the wavelength range of

Referring to graph 510, the first reflective layer of the selective reflective layer of the transparent radiation cooling device according to an embodiment of the present invention is formed of a-Si:H, the second reflective layer is formed of Al ₂ O ₃ , and the wavelength It shows high reflectance and low absorption at 1 μm, and low transmittance.

In addition, it can be seen that it shows low reflectance and low absorption at a wavelength of 1.5 μm and high transmittance.

The left vertical axis of the graph 510 represents percentage, 1 represents 100%, and the right vertical axis represents the solar spectrum.

Referring to graph 511, it can be seen that the refractive index of Al ₂ O ₃ forming the second reflective layer is similar to that of SiO ₂ , and it can be confirmed that Al ₂ O ₃ can be used as the second reflective layer.

That is, referring to FIGS. 4 to 5B , when there is a difference in refractive index between the transparent radiation cooling material forming the first reflection layer and the second reflection layer constituting the selective reflection layer included in the transparent radiation cooling element according to an embodiment of the present invention. , it can be confirmed that sunlight in the visible light region is transmitted, and sunlight in the ultraviolet region and the near infrared region is reflected without being absorbed.

6 to 10 illustrate radiant cooling characteristics according to structural changes of a selective reflection layer of a transparent radiation cooling device according to an embodiment of the present invention.

The left vertical axis of the graphs shown in FIGS. 6 to 10 represents percentage, 1 represents 100%, and the right vertical axis represents solar spectrum.

6 illustrates a case in which the number of stacked layers of the first reflective layer and the second reflective layer constituting the selective reflective layer according to an embodiment of the present invention is five.

Referring to FIG. 6 , a transparent radiation cooling device 600 according to an embodiment of the present invention includes a transparent substrate 601, a first reflective layer 602, a second reflective layer 603, and a selective emission layer 604. . Here, the transparent substrate 601 may be referred to as a glass substrate.

The first reflective layer 602 is made of a-Si:H and has a thickness of 70 nm, 63 nm and 71 nm, and the second reflective layer 603 is made of SiO ₂ and has a thickness of 174 nm.

A graph 610 illustrates transmittance (T), reflectance (R), and absorptivity (A) in a wavelength range corresponding to sunlight in the ultraviolet region, near infrared region, and visible region of the transparent radiation cooling element 600 .

In the graph 610, f represents an optimization parameter value for high transmittance in the visible light region and high reflectance in the near infrared region, and the lower the value, the better the characteristics.

Referring to the graph 610, it shows high reflectance and low absorbance at a wavelength of 1 μm, and low transmittance.

In addition, it can be seen that it shows low transmittance and low absorbance at a wavelength of 1.5 μm, and shows high transmittance.

7 illustrates a case in which the number of stacked layers of the first reflective layer and the second reflective layer constituting the selective reflective layer according to an embodiment of the present invention is four.

Referring to FIG. 7 , a transparent radiation cooling device 700 according to an embodiment of the present invention includes a transparent substrate 701, a first reflective layer 702, a second reflective layer 703, and a selective radiation layer 704. . Here, the transparent substrate 701 may be referred to as a glass substrate.

The first reflective layer 702 is formed of a-Si:H and is formed to a thickness of 63 nm and 71 nm, and the second reflective layer 703 is formed of SiO ₂ and is formed to a thickness of 174 nm.

A graph 710 illustrates transmittance (T), reflectance (R), and absorptivity (A) in a wavelength range corresponding to sunlight in the ultraviolet region, near infrared region, and visible region of the transparent radiation cooling element 700 .

In the graph 710, f may indicate an optimization parameter value for high transmittance in the visible light region and high reflectance in the near infrared region.

Referring to the graph 710, it shows high reflectance and low absorbance at a wavelength of 1 μm, and low transmittance.

In addition, it can be seen that it shows low transmittance and low absorbance at a wavelength of 1.5 μm, and shows high transmittance.

However, when compared to the graph 610, the reflectance may be low and the transmittance may be similarly high.

That is, if the number of stacked layers decreases, the reflectance may decrease.

8 illustrates a case in which the number of stacked layers of the first reflective layer and the second reflective layer constituting the selective reflective layer according to an embodiment of the present invention is three.

Referring to FIG. 8 , a transparent radiation cooling device 800 according to an embodiment of the present invention includes a transparent substrate 801, a first reflective layer 802, a second reflective layer 803, and a selective emission layer 804. . Here, the transparent substrate 801 may be referred to as a glass substrate.

The first reflective layer 802 is formed of a-Si:H and is formed to a thickness of 63 nm and 71 nm, and the second reflective layer 803 is formed of SiO ₂ and is formed to a thickness of 174 nm.

A graph 810 illustrates transmittance (T), reflectance (R), and absorptivity (A) in a wavelength range corresponding to sunlight in the ultraviolet region, near infrared region, and visible region of the transparent radiation cooling element 800 .

In the graph 810, f may indicate an optimization parameter value for high transmittance in the visible light region and high reflectance in the near infrared region.

Referring to the graph 810, it shows high reflectance and low absorbance at a wavelength of 1 μm, and low transmittance.

In addition, it can be seen that it shows low transmittance and low absorbance at a wavelength of 1.5 μm, and shows high transmittance.

However, when compared with the graph 610, the reflectance may be low and the transmittance may be low.

That is, when the number of stacked layers decreases, reflectance for sunlight in the ultraviolet and near-infrared regions may decrease, and transmittance for sunlight in the visible region may also decrease.

9 illustrates a case in which the number of stacked layers of the first reflective layer and the second reflective layer constituting the selective reflective layer according to an embodiment of the present invention is two.

Referring to FIG. 9 , a transparent radiation cooling device 900 according to an embodiment of the present invention includes a transparent substrate 901, a first reflective layer 902, a second reflective layer 903, and a selective emission layer 904. . Here, the transparent substrate 901 may be referred to as a glass substrate.

The first reflective layer 902 is formed of a-Si:H and is formed to a thickness of 71 nm, and the second reflective layer 903 is formed of SiO ₂ and is formed to a thickness of 174 nm.

A graph 910 illustrates transmittance (T), reflectance (R), and absorptivity (A) in a wavelength range corresponding to sunlight in the ultraviolet region, near infrared region, and visible region of the transparent radiation cooling element 900 .

In the graph 910, f may indicate an optimization parameter value for high transmittance in the visible light region and high reflectance in the near infrared region.

Referring to the graph 910, it shows high reflectance and low absorbance at a wavelength of 1 μm, and low transmittance.

In addition, it can be seen that it shows low transmittance and low absorbance at a wavelength of 1.5 μm, and shows high transmittance.

However, when compared with the graph 610, the reflectance may be low and the transmittance may be low.

That is, when the number of stacked layers decreases, reflectance for sunlight in the ultraviolet and near-infrared regions may decrease, and transmittance for sunlight in the visible region may also decrease.

10 illustrates a case in which the number of stacked layers of the first reflective layer and the second reflective layer constituting the selective reflective layer according to an embodiment of the present invention is one.

Referring to FIG. 10 , a transparent radiation cooling device 1000 according to an embodiment of the present invention includes a transparent substrate 1001 , a first reflection layer 1002 and a selective emission layer 1003 . Here, the transparent substrate 1001 may be referred to as a glass substrate.

The first reflective layer 1002 is formed of a-Si:H and has a thickness of 71 nm.

A graph 1010 illustrates transmittance (T), reflectance (R), and absorptivity (A) in a wavelength range corresponding to sunlight in the ultraviolet region, near infrared region, and visible region of the transparent radiation cooling element 1000 .

In the graph 1010, f may indicate an optimization parameter value for high transmittance in the visible light region and high reflectance in the near infrared region.

Referring to the graph 1010, the reflectance may be relatively low and the transmittance may be low.

That is, when the number of stacked layers decreases, reflectance for sunlight in the ultraviolet and near-infrared regions may decrease, and transmittance for sunlight in the visible region may also decrease.

Referring to FIGS. 6 to 10 , when the number of layers of the first and second reflective layers forming the selective reflective layer is reduced, the reflectance in the near-infrared light is reduced and the cooling effect may be reduced. Conversely, when the number of layers is increased, a-Si:H As the loss increases based on , the transmittance of sunlight in the visible light region may decrease.

Accordingly, the present invention can improve radiant cooling performance by absorbing and emitting infrared rays corresponding to a wavelength range of a window in the atmosphere while minimizing heat inflow based on a selective reflection layer using a multilayer thin film structure.

Preferably, the selective reflection layer of the transparent radiation cooling element according to an embodiment of the present invention may be formed in a five-layer structure.

11A to 11C explain radiation cooling test results using a transparent radiation cooling device according to an embodiment of the present invention.

11A illustrates a radiant cooling experimental environment using a transparent radiant cooling device according to one embodiment of the present invention.

Referring to FIG. 11A , in a radiation cooling experiment environment 1100 using a transparent radiation cooling element, an acrylic box 1102 is located between wooden frames 1101, an absorption chamber 1103 is located in the acrylic box 1102, and an absorption chamber 1103 is located. A sample 1104 of a transparent radiation cooling element is placed on the chamber 1103, and a PE (polyethylene) film 1105 is placed.

The radiation cooling experiment environment 1100 using the transparent radiation cooling element may measure the ambient temperature (T _amb ), the temperature in the chamber (T _chamber ), and the temperature (Tc _ooler ) in the absorption chamber 1103 .

11B illustrates an infrared image of an experimental result based on a radiation cooling experimental environment using a transparent radiation cooling device according to an embodiment of the present invention.

Referring to FIG. 11B , infrared images of a transparent radiation cooling device 1110 , a comparison object 1111 , and a room temperature 1112 according to an embodiment of the present invention are shown.

The transparent radiation cooling element 1110 represents 40.5°C, the comparison object 1111 represents 47.3°C, and room temperature may represent 50.9°C.

Here, the comparison object 1111 may correspond to a case in which only a selective emission layer is formed on a transparent substrate.

That is, it can be confirmed that the cooling temperature of the transparent radiation cooling element 1110 is greater than that of other comparison objects.

FIG. 11C illustrates a radiation cooling capacity change according to a time change in a radiation cooling experimental environment using a transparent radiation cooling device.

Referring to FIG. 11C , a graph 1120 illustrates that the transparent radiation cooling element T _cooler has excellent cooling performance compared to the comparison target T _ref during daytime.

11D illustrates an image of a transparent radiant cooling element according to one embodiment of the present invention.

Referring to FIG. 11D , it can be confirmed that the transparent radiation cooling element 1130 according to an embodiment of the present invention is transparent and has transparency enough to clearly identify an image located on the opposite side.

12A and 12B illustrate an embodiment in which a color layer is added to a transparent radiation cooling element according to an embodiment of the present invention.

Referring to FIG. 12A , a transparent radiation cooling element 1200 to which a color layer is added includes a transparent substrate 1201, a color layer 1202, and a transparent radiation cooling element 1203.

That is, the transparent radiation cooling element 1200 may further include a color layer 1202 that implements colors according to the type of color paint on the other side of the transparent substrate 1201 positioned below the selective reflection layer.

The transparent radiation cooling device 1200 according to an embodiment of the present invention transmits sunlight in the visible light region, reflects sunlight in the near infrared region, and absorbs and emits infrared rays corresponding to the wavelength range of the atmospheric window.

Accordingly, the transparent radiation cooling device 1200 can have aesthetic improvement by using existing commercially available paint together, and can absorb and emit infrared rays corresponding to the wavelength range of a window in the atmosphere while reflecting sunlight in the near-infrared region. .

12B illustrates colors 1210 implemented based on a color layer in a transparent radiation cooling device according to an embodiment of the present invention.

Referring to FIG. 12B , the transparent radiation cooling device according to an embodiment of the present invention may display a color corresponding to a color of a color layer positioned below a transparent substrate. For example, the color layer may be referred to as a paint layer.

13A to 13C illustrate radiation cooling test results using a transparent radiation cooling element to which a color layer is added according to an embodiment of the present invention.

13A illustrates a radiant cooling experiment environment using a transparent radiant cooling device to which a color layer is added according to an embodiment of the present invention.

Referring to FIG. 13A, in a radiation cooling experiment environment 1300 using a transparent radiation cooling element to which a color layer is added, an acrylic box 1302 is placed between wooden frames 1301, and a transparent radiation cooling element within the acrylic box 1302. A sample 1303 of is positioned, and a polyethylene (PE) film 1304 is positioned. Here, a measuring point 1305 for measuring the surface temperature is additionally included in the sample 1303 of the transparent radiation cooling element.

The radiation cooling experiment environment 1300 using the transparent radiation cooling element may measure the temperature in the chamber (T _chamber ) and the ambient temperature (Tamb).

13B illustrates an infrared image of an experimental result based on a radiation cooling experimental environment using a transparent radiation cooling device according to an embodiment of the present invention.

Referring to FIG. 13B , an infrared image of a transparent radiation cooling element 1310 and a comparison object 1311 according to an embodiment of the present invention is shown.

Transparent radiation cooling element 1310 exhibits 37.9°C and comparison object 1311 exhibits 43.6°C.

Here, the comparison target 1311 may correspond to a case in which only a selective emission layer is formed on a transparent substrate.

That is, it can be confirmed that the cooling temperature of the transparent radiation cooling element 1310 is higher than that of the comparison object 1311 .

FIG. 13C illustrates a change in radiation cooling capacity with time in a radiation cooling experimental environment using a transparent radiation cooling device.

Referring to FIG. 13C , a graph 1320 illustrates that the transparent radiation cooling element T _cooler has excellent cooling performance compared to the comparison target T _ref , during daytime.

Therefore, the present invention can provide a transparent radiation cooling element that provides a cooling function without consuming energy while providing aesthetic improvement by using a commercially available paint together with a transparent radiation cooling element.

In the above-described specific embodiments, components included in the invention are expressed in singular or plural numbers according to the specific embodiments presented.

However, singular or plural expressions are selected appropriately for the presented situation for convenience of explanation, and the above-described embodiments are not limited to singular or plural components, and even components expressed in plural are composed of a singular number or , Even components expressed in the singular can be composed of plural.

Meanwhile, in the description of the invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the technical idea contained in the various embodiments.

Therefore, the scope of the present invention should not be limited to the described embodiments and should not be defined, but should be defined by not only the claims to be described later, but also those equivalent to these claims.

200: transparent radiation cooling element
210: transparent substrate 220: selective reflection layer
221: first reflective layer 222: second reflective layer
230: selective radiation layer

Claims (12)

Based on a multilayer structure in which a first reflective layer made of a first transparent radiant cooling material and a second reflective layer made of a second transparent radiant cooling material are repeatedly stacked, sunlight in the visible light region is transmitted, and sunlight in the ultraviolet and near-infrared region is transmitted. a selective reflective layer that reflects at least one of; and
A selective emission layer made of a polymer material that absorbs and emits infrared rays in a wavelength range corresponding to the sky window of the sunlight,
the first transparent radiant cooling material comprises a-Si:H;
the second transparent radiant cooling material comprises at least one of SiO ₂ , Al ₂ O ₃ , MgF ₂ and Si ₃ N ₄ ;
The refractive index of the selective reflective layer is different between the first reflective layer and the second reflective layer when the refractive index of the first transparent radiation-cooling material is higher than the refractive index of the second transparent radiation-cooling material with respect to sunlight in the ultraviolet and near-infrared regions. Characterized in that based on the refractive index difference, sunlight in the visible light region is transmitted and at least one of sunlight in the ultraviolet region and the near infrared region is reflected according to the presence of
Transparent radiant cooling element. delete According to claim 1,
In the selective reflection layer, as the refractive index difference between the first transparent radiation-cooling material and the second transparent radiation-cooling material increases, the transmittance of sunlight in the visible region and the reflectance of sunlight in the ultraviolet and near-infrared regions increase. characterized
Transparent radiant cooling element. According to claim 1,
The selective reflective layer has a cross structure in which the second reflective layer is formed on the first reflective layer and the first reflective layer is formed on the second reflective layer, and the first reflective layer and the second reflective layer are one to five layers. characterized in that
Transparent radiant cooling element. According to claim 4,
Since the selective reflective layer is formed of the first to fifth layers, when the number of layers increases, transmittance of sunlight in the visible light region decreases, reflectance of sunlight in the ultraviolet and near infrared regions increases, and when the number of layers decreases, the transmittance of sunlight in the ultraviolet region and the near infrared region increases. Characterized in that the transmittance of sunlight in the visible light region increases and the reflectance of sunlight in the ultraviolet and near infrared regions decreases.
Transparent radiant cooling element. According to claim 1,
The thickness of the first reflective layer is formed to be 63 nm to 71 nm in relation to the number of layers of the first reflective layer and the second reflective layer,
Characterized in that the thickness of the second reflective layer is formed to 174 nm
Transparent radiant cooling element. delete delete According to claim 1,
Characterized in that the selective emission layer is formed of the polymer material including polydimethyl siloxane (PDMS)
Transparent radiant cooling element. According to claim 9,
Characterized in that the thickness of the selective emission layer is formed to 50㎛
Transparent radiant cooling element. According to claim 1,
Characterized in that it further comprises a color layer for implementing colors according to the type of color paint on the other side of the transparent substrate located at the bottom of the selective reflection layer.
Transparent radiant cooling element. According to claim 11,
The selective reflection layer is characterized in that located between the transparent substrate and the selective emission layer
Transparent radiant cooling element.

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