Patent Application
20230304751
The present invention relates to a technical idea of cooling the surface of a material or the internal temperature under the material by emitting heat under an element to the outside while minimizing absorption of light in the solar spectrum, and more particularly to a technology for developing a material having a high transmittance or high reflectance with respect to incident sunlight and a high absorptivity selectively in a wavelength range of 8 μm to 13 μm corresponding to the sky window section of the atmosphere.
A passive radiative cooling device can be passively cooled by reflecting the wavelength (0.3 to 2.5 μm) corresponding to sunlight during the day and radiating radiative heat (8 to 13 μm) energy that can escape out of space.
Meanwhile, a passive radiative heating device can be passively heated because it absorbs the wavelength (0.3 to 2.5 μm) corresponding to sunlight during the day and does not well absorb radiative heat (8 to 3 μm) energy that can escape out of space.
The efficiency of a passive cooling device can be confirmed by measuring the optical characteristics of the device itself.
For heat dissipation, a high absorptivity or emissivity in the long-wavelength infrared region is required so that heat can be radiated well into space.
According to the Planck distribution, when the temperature is 300 K, it has a condition for maximally emitting heat in the wavelength range of 6 to 20 μm. In the case of the Earth, the sky window area of the atmosphere is about 8 to 13 μm, so the absorptivity or emissivity in the 8 to 13 μm area should be the maximum to maximize the heat dissipation capability of a passive cooling device.
Infrared radiation in the sky window wavelength range of the atmosphere plays a key role in achieving radiative cooling by substantial heat dissipation. If a wavelength range reflects 100% of the sunlight (emitted from the sun) incident on ultraviolet-visible-near-infrared rays, and 100% of long-wavelength infrared rays in the 8 μm to 13 μm region, which is the sky window section of the atmosphere, can be radiated to the outside, a cooling performance of 158 W/m2 can be realized without energy consumption at an ambient temperature of 300K.
If 95% of sunlight is reflected, 90% or more of mid-infrared radiation in the 8 μm to 13 μm area is radiated to the outside, and the ambient temperature is 300 K, a cooling performance of 100 W/m2 is achieved during the day (i.e., light absorption by the sun exists) can be realized, and a cooling performance of 120 W/m2 can be realized at night when there is no light absorption by the sun.
To be used as a passive radiative cooling material, it should have high transmittance or high reflectance to light, which is incident sunlight, in the UV-vis-NIR wavelength range so as not to absorb incident sunlight, should have high absorptivity (emissivity) for long-wavelength infrared rays in the 8 to 13 μm region which is the sky window section of the atmosphere, and should have high durability (stability, corrosion resistance) in outdoor conditions. In addition, the used material should be cheap and abundant, and it should be possible to form a large area through an inexpensive and easy process.
Polymer materials generally have high absorptivity (emissivity) for long-wavelength infrared rays, but due to the characteristics thereof, they are easily deteriorated by ultraviolet rays and moisture when left outdoors, resulting in a short lifespan.
In the case of using a multi-layer thin film made of an inorganic material (e.g., ceramic material), the lifetime and stability of the material are guaranteed, but a vacuum deposition process is required, which increases the production cost and may limit large-area production.
If there is a material with high absorptivity (emissivity) in the entire area of the sky window section of the atmosphere, and if this material has high stability outdoors, is inexpensive, and can be used for large-area molding, it will be the most ideal passive radiative cooling material. However, in reality, such a material is absent.
Therefore, the present invention has been made in view of the above problems, and it is one object of the present invention to realize a high emissivity, compared to a polymer-based radiative cooling device, by constituting an infrared radiation layer with a ceramic nanoparticle mixture mixed depending upon a section having a high emissivity partially within the wavelength range corresponding to the sky window of the atmosphere.
It is another object of the present invention to provide a radiative cooling device capable of performing cooling below ambient temperature without consuming energy during day time when sunlight is shining or even during night time when sunlight is not shining, thereby performing a cooling function without energy consumption when applied to the external surface of materials requiring cooling such as buildings and automobiles.
It is still another object of the present invention to improve the energy efficiency of an existing cooling system using energy by being simultaneously applied to the existing cooling system.
It is still another object of the present invention to provide a radiative cooling device applicable to a solution process based on the low unit cost of a ceramic nanoparticle mixture, and as the solution process is possible, applicable to various substrates, such as silicon, glass, as well as inexpensive plastic and metal substrates.
It is yet another object of the present invention to provide a radiative cooling device capable of exhibiting stable radiative cooling properties even when exposed to an external environment for a long time as nanoparticle materials have excellent chemical stability and mechanical properties (strength and hardness) due to the characteristics of the ceramic materials.
In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a radiative cooling device manufactured using a ceramic nanoparticle mixture, including: a solar reflective layer formed of a metal material to reflect sunlight; and an infrared radiation layer formed by mixing a plurality of ceramic nanoparticles based on any one of a size, thickness, and weight fraction determined in consideration of an absorptivity in a wavelength range corresponding to a sky window of atmosphere and configured to absorb and emit infrared rays in the wavelength range.
The infrared radiation layer may be formed by mixing at least two ceramic nanoparticle types of first ceramic nanoparticles having a first intrinsic emissivity in a first wavelength range, second ceramic nanoparticles having a second intrinsic emissivity in a second wavelength range, and third ceramic nanoparticles having a third intrinsic emissivity in a third wavelength range.
The first wavelength range may include 8 μm to 10 μm in the wavelength range, the second wavelength range may include 10 μm to 12.5 μm in the wavelength range, and the third wavelength range may include 11 μm to 13 μm in the wavelength range.
The first ceramic nanoparticles may include any one ceramic nanoparticle type of SiO2, cBN, and CaSO4 ceramic nanoparticles, the second ceramic nanoparticles may include Si3N4 ceramic nanoparticles, and the third ceramic nanoparticles may include Al2O3 ceramic nanoparticles.
The first intrinsic emissivity may include an emissivity higher than an emissivity of the second ceramic nanoparticles and third ceramic nanoparticles in the first wavelength range, the second intrinsic emissivity may include an emissivity higher than an emissivity of the first ceramic nanoparticles and third ceramic nanoparticles in the second wavelength range, and the third intrinsic emissivity may include an emissivity higher than an emissivity of the first ceramic nanoparticles and second ceramic nanoparticles in the third wavelength range.
In the infrared radiation layer, a particle size and composition related to a size and thickness of the plural ceramic nanoparticles may be determined such that an absorptivity of the infrared rays is increased in the wavelength range.
The plural ceramic nanoparticles may include at least two ceramic nanoparticle types of SiO2, Al2O3, Si3N4, cBN, CaSO4, TiO2, ALON, BaTiO3, BeO, Cu2O, MgAl2O4, SrTiO3, Y2O3, Bi12SiO20, CaCO3, LiTaO3, KNb03, NaNo3, ZrSiO4, and CaMg(Co3)2.
In the infrared radiation layer, each of the plural ceramic nanoparticles may be included in any one structure of a single particle structure and a multiple core shell structure.
The infrared radiation layer may be formed by single coating a mixed solution, in which the plural ceramic nanoparticles are mixed, on the solar reflective layer by any one method of spin coating, drop coating, bar coating, spray coating, doctor blading, and blade coating.
Any one polymer of polydimethyl siloxane (PDMS), polyurethane acrylate (PUA), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), and dipentaerythritol hexaacrylate (DPHA) may be added to the infrared radiation layer formed by coating with the mixed solution.
The infrared radiation layer may be formed by mixing the first ceramic nanoparticles, the second ceramic nanoparticles, and the third ceramic nanoparticles in any one weight fraction of 1:1:1, 1:4:1, and 3:6:7.
The solar reflective layer may be formed of at least one metal material selected from silver (Ag), aluminum (Al), gold (Au), copper (Cu), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), and platinum (Pt) or any one material of alloy materials in which at least two of the metal materials are combined.
The present invention can realize a high emissivity, compared to a polymer-based radiative cooling device, by constituting an infrared radiation layer with a ceramic nanoparticle mixture mixed depending upon a section having a high emissivity partially within the wavelength range corresponding to the sky window of the atmosphere.
The present invention can perform cooling below ambient temperature without consuming energy during day time when sunlight is shining or even during night time when sunlight is not shining, thereby performing a cooling function without energy consumption when applied to the external surface of materials requiring cooling such as buildings and automobiles.
The present invention can improve the energy efficiency of an existing cooling system using energy by being simultaneously applied to the existing cooling system.
The present invention can provide a radiative cooling device applicable to a solution process based on the low unit cost of a ceramic nanoparticle mixture, and as the solution process is possible, applicable to various substrates, such as silicon, glass, as well as inexpensive plastic and metal substrates.
The present invention can exhibit stable radiative cooling properties even when exposed to an external environment for a long time as nanoparticle materials have excellent chemical stability and mechanical properties (strength and hardness) due to the characteristics of the ceramic materials.
The embodiments will be described in detail herein with reference to the drawings.
However, it should be understood that the present disclosure is not limited to the embodiments according to the concept of the present disclosure, but includes changes, equivalents, or alternatives falling within the spirit and scope of the present disclosure.
In the following description of the present disclosure, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure unclear.
The terms used in the specification are defined in consideration of functions used in the present disclosure, and can be changed according to the intent or conventionally used methods of clients, operators, and users. Accordingly, definitions of the terms should be understood on the basis of the entire description of the present specification.
In description of the drawings, like reference numerals may be used for similar elements.
The singular expressions in the present specification may encompass plural expressions unless clearly specified otherwise in context.
In this specification, expressions such as “A or B” and “at least one of A and/or B” may include all possible combinations of the items listed together.
Expressions such as “first” and “second” may be used to qualify the elements irrespective of order or importance, and are used to distinguish one element from another and do not limit the elements.
It will be understood that when an element (e.g., first) is referred to as being “connected to” or “coupled to” another element (e.g., second), it may be directly connected or coupled to the other element or an intervening element (e.g., third) may be present.
As used herein, “configured to” may be used interchangeably with, for example, “suitable for”, “ability to”, “changed to”, “made to”, “capable of”, or “designed to” in terms of hardware or software.
In some situations, the expression “device configured to” may mean that the device “may do ˜” with other devices or components.
For example, in the sentence “processor configured to perform A, B, and C”, the processor may refer to a general-purpose processor (e.g., CPU or application processor) capable of performing corresponding operation by running a dedicated processor (e.g., embedded processor) for performing the corresponding operation, or one or more software programs stored in a memory device.
In addition, the expression “or” means “inclusive or” rather than “exclusive or”. That is, unless otherwise mentioned or clearly inferred from context, the expression “x uses a or b” means any one of natural inclusive permutations.
Terms, such as “unit” or “module”, etc., should be understood as a unit that processes at least one function or operation and that may be embodied in a hardware manner, a software manner, or a combination of the hardware manner and the software manner.
Referring to
For example, the radiative cooling device 100 includes the solar reflective layer 120 and the infrared radiation layer 130.
The solar reflective layer 120 according to an embodiment of the present invention is formed of a metal material to reflect sunlight.
For example, the solar reflective layer 120 may be formed of at least one metal material selected from silver (Ag), aluminum (Al), gold (Au), copper (Cu), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), and platinum (Pt) or any one material of alloy materials in which at least two of the metal materials are combined.
That is, the solar reflective layer 120 may be formed of at least one metal material selected from silver (Ag), aluminum (Al), gold (Au), copper (Cu), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), and platinum (Pt).
In addition, the solar reflective layer 120 may be formed of an alloy material in which at least two of silver (Ag), aluminum (Al), gold (Au), copper (Cu), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), and platinum (Pt) are combined.
For example, the solar reflective layer 120 may be formed by coating at least one metal material selected from silver (Ag), aluminum (Al), gold (Au), copper (Cu), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), and platinum (Pt) or any one material of alloy materials, in which at least two of the metal materials are combined, on any one substrate of glass, a plastic film, and a metal plate which corresponds to the typical layer 110.
The infrared radiation layer 130 according to an embodiment of the present invention may be formed by mixing a plurality of ceramic nanoparticles based on any one of a size, thickness, and weight fraction determined in consideration of absorptivity in a wavelength range corresponding to the sky window of the atmosphere and may absorb and radiate infrared rays in the wavelength range.
For example, the wavelength range corresponding to the sky window of the atmosphere includes a wavelength range of 8 μm to 13 μm.
For example, in the infrared radiation layer 130, the particle size and composition related to the size and thickness of the plural ceramic nanoparticles may be determined so that the absorptivity of infrared rays is increased in the wavelength range corresponding to the sky window of the atmosphere.
For example, the infrared radiation layer 130 may be formed using a mixture, in which the plural ceramic nanoparticles are mixed, after the particle size and composition of each of the plural ceramic nanoparticles is adjusted to have a high emissivity in the wavelength range corresponding to the sky window of the atmosphere.
For example, in the infrared radiation layer 130, each of the plural ceramic nanoparticles may be included in any one of a single particle structure and a multiple core-shell structure.
Therefore, the present invention enables a solution process based on the low unit cost of the ceramic nanoparticle mixture, and as the solution process is possible, it is possible to provide a radiative cooling device applicable to various substrates, such as silicon, glass, as well as inexpensive plastic and metal substrates.
The single particle structure will be further described with reference to
In accordance with an embodiment of the present invention, the infrared radiation layer 130 may be formed by coating a mixed solution, in which the plural ceramic nanoparticles are mixed, on the solar reflective layer 120 by one single coating method of spin coating, drop coating, bar coating, spray coating, doctor blading, and blade coating.
Referring to
In accordance with an embodiment of the present invention, in the infrared radiation layer 140, each nanoparticle type of first ceramic nanoparticles 141, second ceramic nanoparticles 142, and third ceramic nanoparticles 143 among the plural ceramic nanoparticles is mixed in a single particle structure to form a nanoparticle mixture layer on a solar reflective layer.
For example, each nanoparticle type of the first ceramic nanoparticles 141, the second ceramic nanoparticles 142, and the third ceramic nanoparticles 143 may be single coated by any one method of spin coating, drop coating, bar coating, spray coating, doctor blading, and blade coating.
For example, the arrangement order of the first ceramic nanoparticles 141, the second ceramic nanoparticles 142, and the third ceramic nanoparticles 143 may be arbitrarily changed.
For example, the first ceramic nanoparticles 141 may include any one ceramic nanoparticle type of SiO2, cBN and CaSO4, the second ceramic nanoparticles 142 may include Si3N4 ceramic nanoparticles, and the third ceramic nanoparticles 143 may include Al2O3 ceramic nanoparticles.
Referring to
Each nanoparticle type of first ceramic nanoparticles 151, second ceramic nanoparticles 152, and third ceramic nanoparticles 153 of the plural ceramic nanoparticles may be mixed in a multiple core-shell structure to form a nanoparticle mixture layer on the solar reflective layer.
For example, each nanoparticle type of the first ceramic nanoparticles 151, the second ceramic nanoparticles 152, and the third ceramic nanoparticles 153 may be sequentially coated from the core thereof by any one method of spin coating, drop coating, bar coating, spray coating, doctor blading, and blade coating, and the coating order of the first ceramic nanoparticles 151, the second ceramic nanoparticles 152, and the third ceramic nanoparticles 153 may be arbitrarily changed.
For example, the first ceramic nanoparticles 151 may include any one ceramic nanoparticle type of SiO2, cBN, and CaSO4, the second ceramic nanoparticles 152 may include Si3N4 ceramic nanoparticles, and the third ceramic nanoparticles 153 may include Al2O3 ceramic nanoparticles.
Referring to a graph 200 of
Referring to a graph 210 of
Referring to a graph 220 of
Referring to a graph 230 of
In accordance with an embodiment of the present invention, the infrared radiation layer may be formed by mixing at least two ceramic nanoparticle types of first ceramic nanoparticles having a first intrinsic emissivity in a first wavelength range, second ceramic nanoparticles having a second intrinsic emissivity in a second wavelength range, and third ceramic nanoparticles having a third intrinsic emissivity in a third wavelength range.
For example, the first wavelength range may include a wavelength range of 8 μm to 10 μm, the second wavelength range may include a wavelength range of 10 μm to 12.5 μm, and the third wavelength range may include a wavelength range of 11 μm to 13 μm.
For example, the first ceramic nanoparticles may include any one ceramic nanoparticle type of SiO2, cBN, and CaSO4, the second ceramic nanoparticles may include Si3N4 ceramic nanoparticles, and the third ceramic nanoparticles may include Al2O3 ceramic nanoparticles.
The first intrinsic emissivity may include an emissivity higher than the emissivity of the second ceramic nanoparticles and the third ceramic nanoparticles in the first wavelength range.
In addition, the second intrinsic emissivity may include an emissivity higher than the emissivity of the first ceramic nanoparticles and the third ceramic nanoparticles in the second wavelength range.
In addition, the third intrinsic emissivity may include an emissivity higher than the emissivity of the first ceramic nanoparticles and the second ceramic nanoparticles in the third wavelength range.
Therefore, when a plurality of ceramic nanoparticles among SiO2, Al2O3, Si3N4, cBN, and CaSO4 are mixed and formed on the solar reflective layer to form the infrared radiation layer in accordance with an embodiment of the present invention, any one ceramic nanoparticle type of SiO2, cBN, and CaSO4 having an emissivity higher than the emissivity of Al2O3 and Si3N4 in 8 μm to 10 μm in a wavelength range corresponding to the sky window of the atmosphere, Si3N4 nanoparticles having an emissivity higher than the emissivity of SiO2, Al2O3, cBN, and CaSO4 in a wavelength range of 10 μm to 12.5 μm, and Al2O3 nanoparticles having an emissivity higher than the emissivity of SiO2, cBN, CaSO4, and Si3N4 in a wavelength range of 11 μm to 13 μm are mixed and formed.
In addition, the infrared radiation layer may be formed such that the emissivity of any one ceramic nanoparticle type of SiO2, cBN, and CaSO4, the emissivity of Si3N4 nanoparticles, and the emissivity of Al2O3 nanoparticles overlap within the wavelength range corresponding to the sky window of the atmosphere.
Therefore, since the infrared radiation layer of the present invention is constituted using a ceramic nanoparticle mixture mixed depending upon a section having a high emissivity partially within the wavelength range corresponding to the sky window of the atmosphere, the present invention can realize a high emissivity compared to a polymer-based radiative cooling device.
Referring to a graph 300 of
Comparing the first absorptivity 301 to the fourth absorptivity 304, the second absorptivity 302 shows a high absorption between 11 μm to 13 μm, the third absorptivity 303 shows a high absorption between 9 μm to 12 μm, the first absorptivity 301 shows a high absorption between 9 μm to 10 μm, and the fourth absorptivity 304 shows a high absorption between 8 μm to 13 μm that correspond to the sky window of the atmosphere due to the overlap of the optical characteristics of respective materials. Average absorption and average emissivity related to the graph 300 are summarized in Table 1 below.
For example, the ceramic nanoparticle mixture may include SiO2, Al2O3, and Si3N4 mixed in a weight fraction of 1:1:1.
As the first absorptivity 301 to the fourth absorptivity 304 exhibit a relatively low average absorptivity in an incident sunlight wavelength range corresponding to 0.3 μm to 2.5 μm, it can be confirmed that less energy of incident sunlight is absorbed and radiative cooling is possible at day time.
When the first absorptivity 301 to the fourth absorptivity 304 are compared with each other, the average emissivity (absorptivity) of the mixture corresponding to the fourth absorptivity 304 is relatively high compared to other materials.
However, the mixture has an average emissivity (absorptivity) of only about 74% in the sky window section of the atmosphere, which may mean that radiative cooling does not occur sufficiently through the sky window region of the atmosphere. By adjusting the particle size, mixture ratio, and film thickness of each of the nanoparticle types, it is possible to increase an average emissivity (absorptivity) in the sky window section of the atmosphere while maintaining a relatively low average absorptivity in the incident sunlight wavelength range.
For example, the ceramic nanoparticle mixture may include a mixture of SiO2, Al2O3, and Si3N4 mixed in a weight fraction of 1:1:1.
Referring to
Referring to
Referring to a laminated structure. As shown in the image 421, the Si3N4 film may be laminated to a thickness of about 1.8 μm.
As shown in each of the image 400, the image 410, and the image 420, each nanoparticle type may be formed in a film shape by spin coating with ethanol as a solvent at a concentration of 20 wt %.
For example, the solvent includes any one of ethanol, water, hexane, propylene glycol methyl ether acetate (PGMEA), propylene glycol methyl ether (PGME), and methyl isobutyl ketone (MIBK).
For example, as the solvent is highly volatile, a film may be formed by performing spin coating, after respective ceramic nanoparticles are dispersed, by using the solvent that evaporates in a short time.
Referring to
In the case of the ceramic nanoparticle mixtures shown in the image 430 and the image 431, respective nanoparticles may be formed in a film shape by spin coating with ethanol as a solvent at a concentration of 6.67 wt %.
Referring to
When the first absorptivity 501 to the third absorptivity 503 of the graph 500 are compared with each other, the third absorptivity 503 of the infrared radiation layer formed using a mixture of SiO2, Al2O3, and Si3N4 ceramic nanoparticles mixed in a weight fraction of 3:6:7 exhibits a relatively high infrared emissivity.
Table 2 below shows numerical data of average absorptivity and average emissivity in relation to the first absorptivity 501 to the third absorptivity 503 of the graph 500.
According to the graph 500 and Table 2, it can be optimized to have low absorptivity in the solar spectrum and high emissivity in the sky window of the atmosphere by controlling parameters such as the size of nanoparticles of each of SiO2, Al2O3, and Si3N4, the weight fraction thereof, a final nanoparticles layer thickness, and material selection.
In accordance with an embodiment of the present invention, the infrared radiation layer may be formed by mixing the first ceramic nanoparticles, the second ceramic nanoparticles, and the third ceramic nanoparticles in a weight fraction of any one of 1:1:1, 1:4:1, and 3:6:7.
For example, the emissivity of the infrared radiation layer may be changed by the weight fraction and thickness (variable) of the materials.
Referring to a graph 600 of
The numerical data of the graph 600 is summarized in Table 3 below.
Referring to the graph 600 and Table 3, since there is no significant effect on the optical characteristics due to the addition of the polymer, and all samples show a low average absorptivity of 5% or less in the incident sunlight wavelength range, and an average emissivity (absorptivity) in the sky window wavelength range of the atmosphere is 74% or more, the radiative cooling device may be used for radiative cooling during day time and radiative cooling at night.
For example, the polymer may include at least one of polydimethyl siloxane (PDMS), polyurethane acrylate (PUA), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), and dipentaerythritol hexaacrylate (DPHA).
In accordance with an embodiment of the present invention, the infrared radiation layer of the radiative cooling device may be formed by adding any one polymer of polydimethyl siloxane (PDMS), polyurethane acrylate (PUA), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), and dipentaerythritol hexaacrylate (DPHA) to the infrared radiation layer formed by coating with the mixed solution.
Referring to
When a small amount of a polymer such as DPHA is added to a nanoparticle mixture for forming an infrared radiation layer, adhesion between the ceramic nanoparticles and a substrate may be improved.
Here, since the polymer is added in a small amount so as not to affect the absorption in the solar region, the absorption in the solar region is not affected as can be seen from Table 3.
Referring to a graph 700 of
Here, the first temperature 702 illustrates a case in which a solar reflective layer is only formed on a substrate, the second temperature 703 illustrates a case in which an infrared radiation layer manufactured using a mixture of SiO2, Al2O3, and Si3N4 mixed in a ratio of 1:1:1 is formed on a substrate and a solar reflective layer, the third temperature 704 illustrates a case in which an infrared radiation layer manufactured using a mixture of SiO2, Al2O3, and Si3N4 mixed in a ratio of 1:4:1 is formed on a substrate and a solar reflective layer, the fourth temperature 705 illustrates a case in which an infrared radiation layer manufactured using a mixture of SiO2, Al2O3, and Si3N4 mixed in a ratio of 3:6:7 is formed on a substrate and a solar reflective layer, and the fifth temperature 705 corresponds to the atmospheric layer.
That is, the graph 700 illustrates external temperature measurement data of a radiative cooling device manufactured with only a solar reflective layer without thermal radiation and of a nanoparticle mixture-based radiative cooling device manufactured using a mixture of SiO2, Al2O3, and Si3N4 nanoparticles mixed in a weight fraction of 1:1:1, 1:4:1, or 3:6:7.
Comparing the second temperature 703 to the fourth temperature 705 with the fifth temperature 706, the nanoparticle mixture-based radiative cooling devices were cooled by about 8 to 13 degrees for 12 to 16 hours.
In addition, comparing the second temperature 703 to the fourth temperature 705 with the first temperature 702, the second temperature 703 to the fourth temperature 705 were cooled by about 5 to 10 degrees than the first temperature 702 without emissivity.
Referring to a graph 710 of
Here, the first temperature 711 illustrates a case in which a solar reflective layer is only formed on a substrate, the second temperature 712 illustrates a case in which an infrared radiation layer manufactured using a mixture of SiO2, Al2O3, and Si3N4 mixed in a ratio of 1:1:1 is formed on a substrate and a solar reflective layer, the third temperature 713 illustrates a case in which an infrared radiation layer manufactured using a mixture of SiO2, Al2O3, and Si3N4 mixed in a ratio of 1:4:1 is formed on a substrate and a solar reflective layer, and the fourth temperature 714 illustrates a case in which an infrared radiation layer manufactured using a mixture of SiO2, Al2O3, and Si3N4 mixed in a ratio of 3:6:7 is formed on a substrate and a solar reflective layer.
Comparing the first temperature 711 with the second temperature 712 to the fourth temperature 714, the second temperature 712 to the fourth temperature 714 corresponding to nanoparticle mixture-based radiative cooling devices were further cooled by about 6 to 10 degrees than the first temperature 711 having no emissivity and only a small absorption of sunlight.
Therefore, the present invention can perform cooling below ambient temperature without consuming energy during day time when sunlight is shining or even during night time when sunlight is not shining, thereby performing a cooling function without energy consumption when applied to the external surface of materials requiring cooling such as buildings and automobiles.
In addition, the present invention can be simultaneously applied to an existing cooling system using energy, thereby improving the energy efficiency of the cooling system.
Further, the present invention can exhibit stable radiative cooling properties even when exposed to an external environment for a long time as nanoparticle materials have excellent chemical stability and mechanical properties (strength and hardness) due to the characteristics of the ceramic materials.
Referring to
Comparing a change in a first absorptivity 801 of the graph 800 with a change in a second absorptivity 811 of the graph 810, the radiative cooling device manufactured using the ceramic nanoparticle mixture formed of mixed nanoparticles selected from materials having intrinsic emissivity in the sky window of the atmosphere exhibits a selectively high emissivity in a wavelength range of 8 μm to 13 μm corresponding to the sky window of the atmosphere, compared to a polymer-based radiative cooling device.
In
Referring to the graph 900 of
Referring to the graph 910 of
Referring to the graph 920 of
In the graphs 900 to 920, the first size may be 50 nm, the second size may be 300 nm, the third size may be 600 nm, and the fourth size may be 2400 nm.
The graphs 900 and 910 represent the same data and exhibit different absorptivity.
That is, since the absorptivity of the graph 900 is 0 to 1.0 and the absorptivity of the graph 910 is 0 to 0.3, the enlarged absorptivity of the graph 900 may correspond to that of the graph 910.
From the graph 910, it can be confirmed that an absorptivity in a wavelength of 400 nm to 700 nm increases as the size of particles increases.
From the graph 920 showing the first size 921 to the fourth size 924 in a wavelength range of 2.5 μm to 15 μm, it can be confirmed that the size of SiO2 particles is 50 nm to 2400 nm in a wavelength range of 8 μm to 10 μm showing a relatively high emissivity.
That is, the particle size of SiO2 nanoparticles among the plural ceramic nanoparticles of the infrared radiation layer may be determined to be 50 nm to 2400 nm such that the absorptivity of infrared rays is increased.
Therefore, the granularity and composition related to the size and thickness of the plural ceramic nanoparticles of the infrared radiation layer may be determined such that the absorptivity of infrared rays is increased in the wavelength range corresponding to the sky window of the atmosphere.
In the above-described specific embodiments, elements included in the invention are expressed singular or plural in accordance with the specific embodiments shown.
It should be understood, however, that the singular or plural representations are to be chosen as appropriate to the situation presented for the purpose of description and that the above-described embodiments are not limited to the singular or plural constituent elements. The constituent elements expressed in plural may be composed of a single number, and constituent elements expressed in singular form may be composed of a plurality of elements.
In addition, the present invention has been described with reference to exemplary embodiments, but it should be understood that various modifications may be made without departing from the scope of the present disclosure.
Therefore, the scope of the present invention should not be limited by the embodiments, but should be determined by the following claims and equivalents to the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2020-0044215 | Apr 2020 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2021/004422 | 4/8/2021 | WO |
