Composite radiative cooling material

Abstract

A composite radiative cooling material comprises a first layer, a second layer, and a third layer. The first layer comprises a reflective material, the second layer comprises a porous material, and the third layer comprises a reflective material. The optical properties of the respective materials and the arrangement of the layers result in the radiative cooling material exhibiting a total solar reflectivity greater than 85% and a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm. These layers can be arranged in a vertically stacked configuration, wherein when the composite radiative cooling material is installed to cool a load, the third layer can directly face the sky, the second layer is arranged below the third layer, and the first layer is arranged below the second layer. The composite radiative cooling material can be thermally coupled to the cooling load to provide radiative cooling to the cooling load.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 604,148, filed November 29, 2023, and U.S. Provisional Patent Application No. 63 / 631,913, filed April 9, 2024, the disclosures of which are incorporated herein by reference in their entirety. Background Technology

[0003] Radiative cooling materials can exhibit optical properties, including reflectivity of incoming solar radiation and emissivity of infrared radiation, enabling them to cool loads. Radiative cooling materials can replace more energy-intensive cooling solutions and can also be used to improve the efficiency of such energy-intensive cooling solutions. Summary of the Invention

[0004] This disclosure relates to composite radiative cooling materials. More specifically, this disclosure relates to composite radiative cooling materials exhibiting reflective (e.g., solar radiation) and emissive (e.g., infrared energy) properties, suitable for cooling loads.

[0005] Composite radiative cooling materials can be used in cooling applications. For example, composite radiative cooling materials can incorporate or integrate various materials that have suitable reflectivity in the ultraviolet (UV) and visible portions of the electromagnetic spectrum and suitable thermal emissivity in the infrared portion of the electromagnetic spectrum. In some embodiments, the composite radiative cooling material comprises three layers, with a top radiative layer, a middle porous layer, and a bottom reflective layer. Composite radiative cooling materials can provide cooling by being applied directly to a surface (e.g., to cool anything on the opposite side of a surface, such as the interior of a building or vehicle, electronic equipment, or any other heat-generating device). Composite radiative cooling materials can also provide cooling by thermal coupling with a heat exchanger, coolant fluid, heat accumulator, or any combination thereof, wherein the heat exchanger, coolant fluid, heat accumulator, or any combination thereof is thermally coupled to any suitable cooling load.

[0006] According to embodiments of this disclosure, the composite radiative cooling material comprises a first layer, a second layer, and a third layer, wherein the first layer comprises a reflective material, the second layer comprises a porous material, and the third layer comprises an emissive material. The composite radiative cooling material exhibits a total solar reflectivity greater than 85% and a thermal emissivity greater than 85% in a wavelength range of 8 to 13 μm (e.g., this may refer to exactly 8.0-13.0 μm, inclusive, or about 8.0-13.0 μm). The layers may be arranged in a vertically stacked arrangement, wherein the third layer is arranged to directly face the sky (e.g., when installed for radiative cooling), the second layer is arranged below the third layer, and the first layer is arranged below the second layer. The composite radiative cooling material may be thermally coupled to a cooling load to provide radiative cooling to the cooling load. The cooling load may be inside a building, vehicle, or enclosure, and the composite radiative cooling material may provide radiative cooling due to being arranged on an upward-facing surface of the building, vehicle, or enclosure. A method for arranging the composite radiative cooling material includes arranging the third layer above the second layer and arranging the second layer above the first layer. Methods for cooling loads using composite radiative cooling include thermally coupling a composite radiative cooling material to the load and cooling the load based on total solar reflectivity and thermal emissivity. Attached Figure Description

[0007] The above and other objects and advantages of this disclosure will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0008] Figure 1 Illustrative composite radiative cooling materials according to some embodiments of the present disclosure are shown;

[0009] Figure 2 Illustrative and wavelength-dependent reflectivity, transmittance, and absorptivity exhibited by a first illustrative porous material according to some embodiments of the present disclosure are shown.

[0010] Figure 3 Illustrative and wavelength-dependent reflectance, transmittance, and absorptivity exhibited by a second illustrative porous material according to some embodiments of the present disclosure are shown.

[0011] Figure 4 Illustrative and wavelength-dependent reflectance, transmittance, and absorptivity exhibited by a third illustrative porous material according to some embodiments of the present disclosure are shown.

[0012] Figure 5 The illustrative and wavelength-dependent transmittance of a set of illustrative transparent and emitting materials is shown for some embodiments according to this disclosure;

[0013] Figure 6Illustrative and wavelength-dependent transmittance of illustrative ultraviolet absorber (UVA) materials according to some embodiments of this disclosure is shown;

[0014] Figure 7 Illustrative and wavelength-dependent reflectivity of an illustrative 100 μm ultra-high molecular weight polyethylene (UHMWPE) layer is shown in some embodiments according to this disclosure;

[0015] Figure 8 Illustrative and wavelength-dependent reflectances of two types of UHMWPE films according to some embodiments of this disclosure are shown;

[0016] Figure 9A Illustrative and wavelength-dependent reflectances based on UHMWPE layers with smaller pore membranes stacked on larger pore membranes are shown according to some embodiments of the present disclosure;

[0017] Figure 9B Illustrative and wavelength-dependent reflectances of UHMWPE layers based on stacked sublayers within each layer are shown according to some embodiments of this disclosure;

[0018] Figure 10 Illustrative total solar reflectance of an illustrative UHMWPE layer as a function of total layer thickness is shown according to some embodiments of this disclosure;

[0019] Figure 11 An illustrative cross-sectional schematic diagram of a composite radiative cooling material according to some embodiments of the present disclosure is shown;

[0020] Figure 12 An illustrative cross-sectional schematic diagram of a composite radiative cooling material comprising a porous layer having multiple porous sublayers, according to some embodiments of the present disclosure, is shown.

[0021] Figure 13 An illustrative cross-sectional schematic diagram of a composite radiative cooling material including a mirror film according to some embodiments of the present disclosure is shown;

[0022] Figure 14 An illustrative cross-sectional schematic diagram of the arrangement of various composite radiative cooling materials according to some embodiments of the present disclosure is shown;

[0023] Figure 15 An illustrative cross-sectional schematic diagram of a composite radiative cooling material including a multi-film top layer according to some embodiments of the present disclosure is shown;

[0024] Figure 16 An illustrative cooling system comprising a composite radiative cooling material is shown according to some embodiments of the present disclosure;

[0025] Figure 17 Illustrative methods for arranging layers of composite radiative cooling material according to some embodiments of the present disclosure are shown; and

[0026] Figure 18 An illustrative method for radiation cooling using composite radiation cooling materials is shown according to some embodiments of this disclosure. Detailed Implementation

[0027] Radiative cooling can refer to any technique that uses the radiative properties of a material to provide cooling. To achieve daytime radiative cooling, a material may have high reflectivity in the UV, visible, and near-infrared regions of the solar spectrum and thermal emission in the infrared portion of the electromagnetic spectrum. While many materials will naturally provide a certain amount of radiation and thermal emission, some materials, including some of the composite radiative cooling materials provided in embodiments of this disclosure, may be configured to provide sufficient thermal emission to reduce the temperature of loads, coolant fluids, heat exchange interfaces, any other substances, or any combination thereof. For example, some composite radiative cooling materials provided in embodiments of this disclosure may provide sufficient solar radiation reflectivity and infrared energy emissivity to support cooling applications. In some embodiments, composite radiative cooling materials provide cooling below ambient temperature (i.e., composite radiative cooling materials may be configured to achieve a lower temperature than the surrounding air when exposed to the sky).

[0028] Compared to cooling technologies that rely on condensers, compressors, evaporators, heat pumps, other energy-consuming equipment, or any combination thereof, radiative cooling materials can provide thermal rejection with less (and potentially negligible) continuous energy input requirements. Furthermore, radiative cooling materials can be used in conjunction with condensers, compressors, evaporators, heat pumps, other energy-consuming equipment, or any combination thereof to improve the efficiency of such equipment. Therefore, the composite radiative cooling materials of this disclosure can be provided for environmentally friendly and energy-saving cooling applications, as well as other cooling applications.

[0029] In practice, the composite radiative cooling material disclosed herein can serve many different cooling systems and applications. For example, the composite radiative cooling material can be applied to the surface of a building, vehicle, enclosure, other enclosed space, or any combination thereof, and can then cool the interior of the building, vehicle, enclosure, other enclosed space, or any combination thereof. In another example, the composite radiative cooling material can be thermally coupled to a heat exchanger and can then cool a load also thermally coupled to the heat exchanger. Similarly, the composite radiative cooling material can be thermally coupled to a coolant fluid and can then cool a load also thermally coupled to the coolant fluid.

[0030] In some embodiments, the composite radiative cooling material of this disclosure can be used for passive cooling (i.e., without the need to apply electricity, fuel, other input energy, or any combination thereof to the radiative cooling material, although input energy may be required for other support components of the radiative cooling system, such as for pumping coolant fluid thermally coupled to the radiative cooling material). The composite radiative cooling material of this disclosure can exhibit high reflectivity (e.g., greater than 75% of total solar reflectivity) in the solar portion of the electromagnetic spectrum (“solar spectrum”) and can exhibit high thermal emissivity (e.g., greater than 85%) in the infrared portion of the electromagnetic spectrum. The thermal emissivity can be specifically configured to exhibit high performance in the “sky window” of the electromagnetic spectrum (e.g., from about 8 μm to about 13 μm).

[0031] In some embodiments, the composite radiative cooling materials of this disclosure exhibit high reflectivity in the solar spectrum and high emissivity in the sky window, based on the integration and arrangement of composite material structures comprising at least one highly reflective material and at least one highly emissive material. Such composite radiative cooling materials can be arranged to provide high cooling power, tunable mechanical properties and formation factors, long outdoor lifetime, optical properties optimized for specific radiative cooling applications, or any combination thereof.

[0032] In some embodiments of this disclosure, composite radiation cooling materials are arranged to exhibit optical properties suitable for a variety of radiation cooling applications. These composite radiation cooling materials may comprise a stack of multiple layers, wherein each layer may comprise a stack of multiple sublayers. The composite radiation cooling materials may comprise specific porous materials (e.g., nanoporous or microporous materials) as well as other materials (such as reflectors, mirrors, substrates, adhesives, protective materials, emitting materials, or any combination thereof). Each corresponding material may be configured as a layer (or sublayer) of the composite radiation cooling material. As described above, these composite radiation cooling materials are generally provided for radiation cooling applications (e.g., they may be applied to any system for cooling or as part of any suitable cooling process).

[0033] In some embodiments, porous materials can be configured to exhibit a specific set of optical properties (e.g., target solar radiation reflectivity and target infrared energy emissivity) based on the configuration of average pore size, average porosity, number of porous layers, thickness of the porous material, or any combination thereof. In some embodiments, the corresponding layers of porous material in the composite radiative cooling material can be arranged in a manner that prevents pore filling. For example, the porous material can be modified (e.g., using any suitable surface treatment) to prevent adjacent layers (i.e., materials applied directly above or below the porous layer) from filling the pores of the porous material. When the porous material is one layer in a multilayer composite radiative cooling material, the other layers of the composite radiative cooling material can be configured to provide complementary optical properties (e.g., to improve the reflectivity, emissivity, or both of the composite radiative cooling material without significantly affecting the optical properties of the porous material).

[0034] In some embodiments, the composite radiative cooling material is arranged to include at least one layer for thermal emissivity, at least one layer for solar reflectivity, and at least one porous layer. In some embodiments, the composite radiative cooling material is configured such that each respective layer contributes certain optical properties without significantly affecting (and in some cases enhancing) the optical properties of other layers. For example, the layers of the composite radiative cooling material may be arranged to increase the emissivity of certain highly reflective materials (e.g., including porous materials) without diminishing the reflectivity of the highly reflective materials. Thus, some composite radiative cooling materials of this disclosure may exhibit a total solar reflectivity greater than 85% and a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm, based on specific layer materials and layer arrangements.

[0035] In some embodiments, the composite radiative cooling material of this disclosure exhibits high reflectivity by incorporating one or more reflective porous materials. In some embodiments, the porous material is a plastic material. When using a porous plastic material within the composite radiative cooling material, many limitations associated with porous materials can be addressed based on the appropriate arrangement of the composite radiative cooling material. For example, some limitations that can be addressed include, but are not limited to: porous plastic materials exhibiting insufficient emissivity; being porous to oxygen, water, other liquids, other gases, or any combination thereof; lacking durability for outdoor use (e.g., degradation due to UV); being prone to pore clogging (e.g., clogging by particles, moisture, other substances, or any combination thereof), which can reduce the reflectivity of the material; or any combination thereof.

[0036] In some embodiments, various fillers (e.g., plastic fillers) may act as suitable reflective materials arranged adjacent to or within the porous material to form at least a portion of the composite radiative cooling material. In some embodiments, the composite radiative cooling material may include a void layer (with a solar reflectivity greater than 90% but a thermal emissivity less than 50%) and a layer above the void layer (with a solar absorptivity less than 20% and a thermal emissivity greater than 80%). In some embodiments, the composite radiative cooling material includes a void layer (with a solar reflectivity greater than 90% but a thermal emissivity less than 50%), a layer above the void layer (with a solar absorptivity less than 20%), and an emissive layer below the void layer (with a thermal emissivity greater than 80%). Based on the above two- and three-layer arrangements, the illustrative composite radiative cooling material may exhibit reflective and emissive properties more suitable for radiative cooling than any single layer alone.

[0037] In some embodiments, the emitting layer of the composite radiative cooling material may be a black emitting substrate. In some embodiments, the reflective layer of the composite radiative cooling material may include a porous membrane of polyethylene (PE), high molecular weight polyethylene (HMWPE), ultra-high molecular weight polyethylene (UHMWPE), polyethersulfone (PES), other porous materials, or any combination thereof. In some embodiments, one or more layers adjacent to the porous layer (i.e., which may be referred to as adjacent layers) are arranged above or below the porous layer in a manner that reduces or eliminates the absorption / adsorption of adjacent layer material into the pores of the porous layer.

[0038] In some embodiments, the composite radiative cooling material includes a protective film (e.g., for improving durability, hydrophobicity, stain resistance, other suitable properties, or any combination thereof), which may be applied (e.g., as a top coating (such as a hard coating), a sealant, a reflective layer, or any combination thereof) as the top layer of the composite radiative cooling material (e.g., as an emissive layer, or on top of an emissive layer). For example, the protective film may be applied over a UV-reflective layer of the composite radiative cooling material, and the UV-reflective layer may be disposed over all other layers of the composite radiative cooling material. In some embodiments, the protective film may be visible light transparent, may include UVA, may be thermally emissive, or may be any combination thereof. For example, such a protective film may be a layer or sublayer of the composite radiative cooling material.

[0039] In some embodiments, the composite radiative cooling material includes at least one adhesive layer for mechanically bonding two other layers of the composite radiative cooling material to each other. In some embodiments, at least one aspect of the adhesive layer (e.g., thickness, material composition, curing conditions, or a combination thereof) may be configured such that the adhesive contributes to (or at least does not significantly impair) the optical properties of the composite radiative cooling material (e.g., a total solar reflectance greater than 85% and a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm).

[0040] The subject matter of this disclosure is illustrative. Figure 1-18 For better understanding, the subject matter of this disclosure may also be understood with reference to the following definitions, which apply to the entirety of this disclosure.

[0041] As described herein, a composite radiative cooling material may include at least one layer. As used herein, "layer" may refer to one or more corresponding materials of the composite radiative cooling material. A layer is typically composed of one or more materials, the respective length and width of which are determined by the cross-sectional area of ​​the composite radiative cooling material, and the respective thickness of which is configured to optimize the optical properties of the layer for arrangement within the composite radiative cooling material. A layer may be associated with a specific property, function, or other characteristic of the composite radiative cooling material. For example, a layer may be an emitting layer, a porous layer, a reflective layer, an adhesive layer, a mechanical coupling layer, a protective coating, or any suitable layer or combination of materials arranged and / or configured to contribute to the cooling capability of the composite radiative cooling material (e.g., by providing emissivity, porosity, reflectivity, adhesion, mechanical support, protection, any other suitable property, or any combination thereof). A layer may be associated with at least one material (e.g., a specific material, such as a class of polymers or metals, a class of materials having specific properties, such as reflective or emitting materials, porous materials, or any combination thereof), and may include multiple corresponding materials (e.g., where at least two materials can be mixed (e.g., impregnated or composite polymers), where at least two materials can be stacked on top of each other, or any combination thereof). Layers may include stacks of materials (e.g., multiple films of the same material, films of corresponding materials, or any combination thereof). When a layer comprises a stack of materials (e.g., a stack of materials contributing the desired optical properties and adjacent adhesive materials, a stack of discrete films, a stack of multiple films of a single film type, any other suitable stack of materials, or any combination thereof), each element of the stack may be referred to herein as a sublayer.

[0042] As used herein, a membrane can refer to any material that can be applied to a surface. A composite radiative cooling material itself can be a membrane, layers of a composite radiative cooling material can be corresponding membranes, and sublayers of a composite radiative cooling material can be corresponding membranes.

[0043] As used herein, geometric orientation terms (including, but not limited to, "top," "bottom," "above," "below," "above," "below," similar descriptors, or any derivatives thereof) may be used to help describe the arrangement of composite radiative cooling materials. Composite radiative cooling materials may be arranged to directly face the sky, and when facing the sky, cooling is provided based on the fact that the "top" of the material is the surface directly facing the sky. For example, the emitting layer of a composite radiative cooling material may be arranged as the top of the material. Even when the composite radiative cooling material is, for example, rolled up and placed indoors, it maintains specific "top" and "bottom" surfaces based on the aforementioned capability, which is based on the orientation when the material is installed for its intended cooling load purpose.

[0044] As used herein, “reflectivity” can refer to the reflectivity of incident solar energy. For example, reflectivity can represent the portion of incident solar energy that is not absorbed or transmitted. As used herein, total solar reflectivity can refer to the total reflectivity (i.e., diffuse reflection plus specular reflection) weighted by the AM 1.5G solar spectrum in the wavelength range of 280 nm to 2500 nm.

[0045] As used herein, optical properties may include one or more of emissivity, reflectivity, transmittance, and absorptivity (note that absorptivity may be negligible, but is not necessarily negligible). As used herein, radiation (and related terms) may be used interchangeably with emission (and related terms), and vice versa.

[0046] As used herein, layers of a composite radiative cooling material may be “arranged and / or configured” to contribute to certain optical properties. It will be understood that the layer may be arranged (e.g., relative to other layers) to contribute to certain optical properties based on optical interactions with other layers. It will be understood that the layer may also be configured (e.g., having a certain thickness, porosity, pore size, sublayer arrangement, surface treatment, or any combination thereof) to contribute to certain optical properties based on a configuration that causes the layer to exhibit certain optical properties. “Arranged and / or configured” means that the material is arranged, configured, or both, to contribute to certain optical properties as part of a composite radiative cooling material.

[0047] As used in this article, visible light transparency can refer to materials that transmit most (e.g., more than 95%) of the electromagnetic emissions in the visible spectrum.

[0048] As used in this article, porous and void can be used interchangeably, and vice versa; pore and void can be used interchangeably, and vice versa.

[0049] As used herein, a load can broadly refer to anything that can be cooled. While many exemplary loads are provided in this disclosure, embodiments of this disclosure are not limited to cooling any particular load. Rather, the composite radiative cooling material of this disclosure can be arranged and configured to serve any geothermal cooling application. A load can be used interchangeably with a cooling load, and vice versa.

[0050] Figure 1 An illustrative composite radiative cooling material 100 according to some embodiments of the present disclosure is shown. The composite radiative cooling material 100 includes a top emitting layer 110, an intermediate porous layer 120, and a bottom reflective layer 130. While the various composite radiative cooling materials of the present disclosure do not need to have the same layer sequence or arrangement, the positional description of the composite radiative cooling material 100 is based on the cooling capacity of the composite radiative cooling material 100 according to a certain installation orientation, wherein the top emitting layer faces the sky (i.e., the top emitting layer 110 is directly exposed to incident solar radiation). Although Figure 1 Not shown, but the composite radiative cooling material 100 may also include corresponding adhesive layers between the emitting layer 110 and the porous layer 120, between the porous layer 120 and the reflective layer 130, or between these two pairs of layers (e.g., bonding the porous layer 120 to the emitting layer 110, and / or bonding the porous layer 120 to the reflective layer 130, respectively). Furthermore, the composite radiative cooling material 100 may include an adhesive layer beneath the reflective layer 130 (e.g., mounting the composite radiative cooling material 100 to a substrate, a surface to be cooled, any other suitable interface, or any combination thereof).

[0051] As shown, the composite radiative cooling material 100 can be provided in a vertically stacked arrangement. For example, as shown, the top emitting layer 110 can be arranged to directly face incident solar radiation (e.g., in an orientation when the material is installed for its intended cooling load purpose), the intermediate porous layer 120 is arranged below the top emitting layer 110, and the bottom reflective layer 130 is arranged below the intermediate porous layer 120.

[0052] The porous layer 120 of the composite radiative cooling material 100 can be any nanoporous or microporous layer described in this disclosure, such as PE, polyethylene terephthalate (PET), UHMWPE, PET, polyethersulfone, and polyamide layers, or any other suitable plastic layer, having any suitable thickness, porosity, sublayer stacking, and average pore size. In some embodiments, the porous material is nanoporous; for example, the nanoporous material may comprise a plurality of pores, wherein the average pore size is from 100 nm to 1,000 nm. In some embodiments, the pores of the porous layer 120 cause the porous layer material to exhibit a porosity greater than 75%.

[0053] Table 1 shows representative materials that can be used as porous layers (e.g., as porous layer 120 in radiative cooling material 100) and their corresponding geometric and performance specifications. As listed in Table 1 and referenced in other parts of this disclosure, polyethylene terephthalate diol is abbreviated as PETg. In some embodiments, the representative materials in Table 1 are configured (e.g., to achieve target pore size, porosity, thickness, or any combination thereof) to be appropriately reflective and exhibit the total solar reflectance shown. As reflected in the data in Table 1, porous layer 120 may exhibit a total solar reflectance greater than 75%, and porous layer 120 may have a thickness of at least 1 mil (i.e., 0.001 inch). In some embodiments, porous layer 120 is further arranged and / or configured to exhibit a total solar absorptivity of less than 5%.

[0054] Table 1 – Illustrative Porous Layers for Composite Radiative Cooling Materials

[0055]

[0056] As an alternative, or as a composite material having any one or more of the illustrative materials listed in Table 1, the porous layer 120 may include high molecular weight polyethylene (HMWPE), polysulfone, or fluorinated polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), any other fluorinated polymers, or any combination thereof.

[0057] In some embodiments, the emission layer 110 is any suitable topcoat (e.g., a hard coating), such as a water-based polyurethane. For example, the emission layer 110 can be any of the topcoats shown in Tables 2-3. In some embodiments, Tables 2-3 show how the emission layer 110 can be arranged as a topcoat over a porous material, thereby causing the composite radiative cooling material to exhibit improved emissivity compared to the porous material alone. Although the improvements shown in Tables 2-3 are representative of specific combinations of porous and emission layers, applying other types of emission layers (e.g., including other topcoat materials) to the same porous layer, or applying any emission layer over any porous layer, can result in similar performance improvements as shown in Tables 2-3.

[0058] Table 2-3 shows representative porous layer 120 materials that can be used with a specific emitting layer 110, as listed, along with their corresponding geometry and performance specifications. In some embodiments, each emitting layer 110 in Table 2-3 (e.g., it may be a top coating, such as a hard coating) is arranged (e.g., to achieve a target thickness, number of sublayers, or both) so that the stack of porous layers 120 and emitting layers 110 exhibits the emissivity values ​​shown. The emitting layer 110 can provide a suitable emissivity for radiative cooling applications while minimizing the impact on the total solar reflectivity of one or more underlying layers. As listed in Table 2, the water-based polyurethane may be of the thermoplastic polyurethane (TPU) type.

[0059] Table 2 – Illustrative emissivity improvement through the addition of a top coating on a porous layer

[0060]

[0061] Table 3 – Illustrative emissivity improvements achieved by adding top coatings to various porous layers

[0062]

[0063] Regarding the data in Tables 2-3, the hard coating may comprise two water-based polyurethane films (which may be considered as respective sublayers), any other suitable resin material, or any combination thereof. In some embodiments, the emitter layer 110 may be formed by depositing an aqueous film comprising at least one resin material, including PVDF, polyurethane, acrylic resin, or any combination thereof.

[0064] Table 4 shows illustrative emitting materials used in composite radiative cooling materials (e.g., as emitting layer 110 in composite radiative cooling material 100). As listed in Table 4 and as may be referenced in other parts of this disclosure, UV protection refers to a material configured (e.g., impregnated or otherwise treated) to protect against UV radiation; poly(methyl methacrylate) is abbreviated as PMMA; and polyacrylate coatings are applied using any suitable solvent. Either a fluoropolymer coating or an acrylate coating may be applied over emitting layer 110 (e.g., including any other materials listed in Table 4) or the porous layer 120 of composite radiative cooling material 100.

[0065] Table 4 – Illustrative Emitting Layers for Radiation Cooling Materials

[0066]

[0067] As shown, Figure 4Any illustrative emission layer may be arranged and / or configured to exhibit a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm. In addition to the emissivity values ​​shown in Table 4, any of these illustrative emission layer materials (e.g., the material that can form emission layer 110) may be arranged and / or configured to exhibit a total solar absorptivity of less than 5%.

[0068] In some embodiments, the reflective layer 130 is any suitable commercial reflector, such as a mirror film, as described below, or other suitable reflective material. For example, the reflective layer 130 may include any of the materials shown in Table 5.

[0069] Table 5 illustrates illustrative reflective materials (e.g., used as reflective layer 130 in radiative cooling material 100) and their corresponding geometric and performance specifications. As listed in Table 5 and referenced in other parts of this disclosure, polytetrafluoroethylene is abbreviated as PTFE; Al-plated PET refers to biaxially oriented PET with an aluminum coating (a stack of materials interchangeable with biaxially oriented PET with a silver coating); polyvinyl chloride is abbreviated as PVC; and thermoplastic olefins are abbreviated as TPO. In some embodiments, the representative materials in Table 5 are configured (e.g., to achieve a target thickness) to have suitable reflectivity for radiative cooling applications. As the data in Table 5 show, reflective layer 130 of composite radiative cooling material 100 may be arranged and / or configured to exhibit a total solar reflectivity greater than 75%.

[0070] Table 5 - Illustrative Reflective Layers of Composite Radiative Cooling Materials

[0071]

[0072] In some implementation schemes, Figure 11-15 Any cross-sectional schematic diagram shown may correspond to an arrangement of composite radiative cooling material 100, or an arrangement of composite radiative cooling material 100 having at least one additional layer.

[0073] In some implementation schemes, Figure 1 The corresponding layers shown can be arranged as illustrated and then chemically or mechanically attached to each other by applying pressure, heat, or both. In some embodiments, applying pressure, heat, or both promotes chemical bonding at the layer-to-layer interfaces.

[0074] Figure 2The illustration shows the illustrative and wavelength-dependent reflectance, transmittance, and absorptance exhibited by a first illustrative porous material according to some embodiments of the present disclosure. The material shown in Figure 200 is porous PE with an average pore size of 100 nm. Curve 210 shows the wavelength-dependent reflectance of the porous PE. Curve 220 shows the wavelength-dependent transmittance of the porous PE (plotted as 1 - transmittance for ease of interpretation); as shown, the transmittance of the porous PE in... Figure 2 The absorption rate is less than 30% across the entire 250 nm–2500 nm wavelength range shown. Curve 230 illustrates the wavelength-dependent absorptivity of porous PE (e.g., calculated as 1 - the difference between transmittance and reflectance). Curve 230 shows the absorptivity of porous PE in… Figure 2 The values ​​shown are mostly zero or close to zero in the 250nm-2500nm wavelength range.

[0075] Figure 3 The illustration shows the illustrative and wavelength-dependent reflectance, transmittance, and absorptance exhibited by a second illustrative porous material according to some embodiments of the present disclosure. The material shown in Figure 300 is a porous UHMWPE with an average pore size of 500 nm. Curve 310 shows the wavelength-dependent reflectance of the porous UHMWPE. Curve 320 shows the wavelength-dependent transmittance of the porous UHMWPE (plotted as 1 - transmittance for ease of interpretation); as shown, the transmittance of the porous UHMWPE is... Figure 3 The absorption rate is less than 30% across the entire 250 nm–2500 nm wavelength range shown. Curve 330 illustrates the wavelength-dependent absorbance of porous UHMWPE (e.g., calculated as 1 - the difference between transmittance and reflectance). Curve 330 shows the absorbance of porous UHMWPE in… Figure 3 The values ​​shown are mostly zero or close to zero in the 250 nm–2500 nm wavelength range.

[0076] Figure 4 The illustration shows the illustrative and wavelength-dependent reflectance, transmittance, and absorptance exhibited by a third illustrative porous material according to some embodiments of the present disclosure. The material shown in Figure 400 is porous PES with an average pore size of 200 nm. Curve 410 shows the wavelength-dependent reflectance of the porous PES. Curve 420 shows the wavelength-dependent transmittance of the porous PES (plotted as 1 - transmittance for ease of interpretation); as shown, the transmittance of the porous PES is... Figure 4 The absorption rate is less than 15% across the entire 250 nm–2500 nm wavelength range shown. Curve 430 illustrates the wavelength-dependent absorbance of porous PES (e.g., calculated as 1 - the difference between transmittance and reflectance). Curve 430 shows the absorbance of porous PES in… Figure 4The values ​​shown are mostly zero or close to zero in the 250 nm–2500 nm wavelength range.

[0077] In some embodiments, the composite radiative cooling material of this disclosure, or at least one layer thereof, may exhibit... Figure 2 , Figure 3 or Figure 4 The wavelength-dependent optical properties shown are illustrated. Figure 2-4 Any material exhibiting the properties shown in the porous layer 120 may be the whole or a part of it.

[0078] Figure 5 Illustrative and wavelength-dependent transmittances exhibited by a group of illustrative transparent emitting materials according to some embodiments of this disclosure are shown. For example, any material having the properties exhibited in illustrative figure 500 may be integral or part of the emitting layer 110. In some embodiments, having Figure 5 The materials exhibiting the properties shown also exhibit the corresponding emissivity values ​​listed in Table 4. In illustrative figures 500, curve 510 shows the illustrative wavelength-dependent transmittance of polycarbonate; curve 520 shows the illustrative wavelength-dependent transmittance of transparent PET; curve 530 shows the illustrative wavelength-dependent transmittance of UV-protected PET; curve 540 shows the illustrative wavelength-dependent transmittance of cyclic olefin copolymers (COC); curve 550 shows the illustrative wavelength-dependent transmittance of PVDF / PMMA composites; and curve 560 shows the illustrative wavelength-dependent transmittance of TPU with UVA.

[0079] At least considering Table 4 and Figure 5 The materials referenced herein, including emitting materials (e.g., for emitting layer 110), may have a suitably high solar transmittance and also include UVA, which may be applied to the emitting material as an additive, as an additive to other materials, or as a discrete film. The optical properties of this UVA may be configured to complement the optical properties of the emitting layer material, porous material, reflective material, or any combination thereof, to provide sufficient UV blocking to protect these materials from rapid weathering in outdoor applications and to minimize absorption of solar radiation.

[0080] In some embodiments, chemically bonded UVA may be added to the emitting layer 110, the adhesive layer, another suitable layer of the composite radiation cooling material, or any combination thereof, to reduce the amount of UV light penetrating the composite material (e.g., to provide protection against UV-induced damage to the material layers).

[0081] In some embodiments, the composite radiative cooling material of this disclosure, or at least one layer thereof, may exhibit... Figure 5 One of the wavelength-dependent transmittances shown. Having Figure 5Any material exhibiting the properties shown in the emission layer 110 may be the whole or a part of it.

[0082] Figure 6 Illustrative and wavelength-dependent transmittance of illustrative UVA materials according to some embodiments of the present disclosure are shown. While some composite radiative cooling materials of the present disclosure include typical UVA in the emitting layer (e.g., depicted by curve 610), other composite radiative cooling materials include blue-shifted (i.e., exhibiting UV absorption initiation at lower wavelengths compared to non-blue-shifted materials) UVA (e.g., depicted in curve 620) to improve the total solar reflectance of the composite film (e.g., which may be all or part of the composite radiative cooling material) while still providing sufficient UV protection for a long outdoor lifetime. Curve 610 shows an illustrative transmission spectrum of a TPU emitting layer with conventional UVA (e.g., in some embodiments, it may correspond to emitting layer 110), exhibiting transmittance greater than 90% at wavelengths greater than 405 nm and less than 5% at wavelengths less than 365 nm. Curve 620 shows an illustrative transmission spectrum of a TPU emitting layer with blue-shifted UVA (e.g., in some embodiments, it may correspond to emitting layer 110), exhibiting a transmittance of more than 90% at wavelengths greater than 380 nm and less than 5% at wavelengths less than 325 nm.

[0083] In some embodiments, the composite radiative cooling material of this disclosure, or at least one layer thereof, may exhibit... Figure 6 One of the wavelength-dependent transmittances shown. Figure 6 Any material may be integral or part of the emission layer 110.

[0084] In some embodiments, by using blue-shifted UVA as a protective material, the composite radiative cooling material 100 or other radiative cooling materials provided according to the subject matter of this disclosure exhibit improved total solar reflectivity (e.g., compared to corresponding materials without UVA or with typical UVA).

[0085] In some embodiments, the composite radiative cooling material 100 or other radiative cooling materials provided according to the subject matter of this disclosure can be assembled by hot-pressing the respective layers into a composite material. This assembly process may or may not include applying at least one adhesive material between the individual layers. Illustrative adhesive materials that may be included as part of any composite radiative cooling material include acrylic adhesives and silicone adhesives. In some embodiments, one or more layers (e.g., any one or more of the emitting layer 110, porous layer 120, or reflective layer 130) may be treated with corona treatment, plasma treatment, chemical treatment, other surface treatments, or any combination thereof to modify the surface of the layer and improve its bonding strength with the adhesive material.

[0086] The illustrative composite radiative cooling material may include various arrangements of an emitting layer 110, a porous layer 120, and a reflective layer 130. Table 6 illustrates some illustrative arrangements of the composite radiative cooling material 100 and their corresponding optical properties. In Table 6, and as available in other parts of this disclosure, pore sizes are reported in nanometers, and thicknesses in mils. For one illustrative example, “PE 450 nm / 12 mil” indicates a polyethylene film with an average pore size of 450 nm and a thickness of 12 mils.

[0087] Table 6: Illustrative Composite Radiative Cooling Materials

[0088]

[0089] Figure 7 Illustrative and wavelength-dependent reflectivity of an illustrative 100 μm UHMWPE layer according to some embodiments of the present disclosure is shown. Figure 7 Curve 710 illustrates that a single UHMWPE layer (e.g., porous layer 120) of the composite radiative cooling material can reflect more than 90% of solar energy in the UV portion of the electromagnetic spectrum, nearly 90% (e.g., more than 85%) of solar energy in the visible portion of the electromagnetic spectrum, and more than 80% of solar energy in the infrared portion of the electromagnetic spectrum. In some embodiments, curve 710 may correspond to curve 310.

[0090] In some embodiments, the composite radiative cooling material of this disclosure, or at least one layer thereof, may exhibit... Figure 7 The wavelength-dependent reflectivity is shown.

[0091] Figure 8Illustrative and wavelength-dependent reflectances of two types of UHMWPE films according to some embodiments of this disclosure are shown. Curve 810 shows the wavelength-dependent reflectance of a 4-mil thick UHMWPE film with an average pore size of 100 nm. Curve 820 shows the wavelength-dependent reflectance of a 4-mil thick UHMWPE film with an average pore size of 500 nm. In this illustrative comparison, the film with a 100 nm pore size is superior to the film with a 500 nm pore size (e.g., it has a greater reflectance).

[0092] In some embodiments, the composite radiative cooling material of this disclosure, or at least one layer thereof, may exhibit... Figure 8 One of the wavelength-dependent reflectivities shown. Having Figure 8 Any material exhibiting the properties shown in the porous layer 120 may be the whole or a part of it.

[0093] Figure 9A Illustrative and wavelength-dependent reflectance of UHMWPE layers based on stacking smaller porous membranes (e.g., having an average pore size of 100 nm or less) onto larger porous membranes (e.g., having an average pore size of 500 nm) within each layer, according to some embodiments of the present disclosure, is shown. Figure 900 illustrates illustrative performance data associated with the following porous layers: (i) Curve 910 corresponds to a layer comprising a first sublayer of a 4-mil thick UHMWPE film with an average pore size of 500 nm and a second sublayer of a 1-mil thick UHMWPE film with an average pore size of 100 nm; (ii) Curve 920 corresponds to a layer comprising a first sublayer of a 4-mil thick UHMWPE film with an average pore size of 500 nm and a second sublayer of a 0.5-mil thick UHMWPE film with a typical pore size of 50 nm; (iii) Curve 930 corresponds to a layer comprising a first sublayer of a 100 μm thick UHMWPE film with an average pore size of 500 nm and a second sublayer of a 0.5-mil thick UHMWPE film with an average pore size of 20 nm; and (iv) Curve 940 corresponds to a layer comprising a 100 μm thick UHMWPE film with an average pore size of 500 nm. In this illustrative comparison, the film with two sublayers is superior to the single film (e.g., it has greater reflectivity).

[0094] Figure 9BIllustration 945 shows illustrative wavelength-dependent reflectance of an illustrative stack of multiple 4-mil thick UHMWPE films according to some embodiments of the present disclosure. The corresponding curves in Illustration 945 correspond to varying numbers of UHMWPE films. Curve 950 shows illustrative reflectance properties of a single 4-mil thick UHMWPE film, curve 960 shows illustrative reflectance properties of a stack comprising two 4-mil thick UHMWPE sublayers, curve 970 shows illustrative reflectance properties of a stack comprising three 4-mil thick UHMWPE sublayers, curve 980 shows illustrative reflectance properties of a stack comprising four 4-mil thick UHMWPE sublayers, and curve 990 shows illustrative reflectance properties of a stack comprising five 4-mil thick UHMWPE sublayers.

[0095] Figure 945 illustrates the reflectivity of a radiation-cooled material as it can increase with the stacking of multiple UHMWPE films or sublayers. In some embodiments, each of the multiple sublayers has the same (or substantially similar) porosity or the same pore size; in other embodiments, at least two of the multiple sublayers have corresponding porosities or corresponding pore sizes (where at least one of these corresponding porosities or pore sizes may be shared among multiple, but not all, layers). Although Figure 945 shows that all the corresponding sublayers have the same thickness, the thickness of the corresponding sublayers of the porous layer 120 does not need to be the same. In some embodiments, a composite radiation-cooled material comprising five corresponding UHMWPE film sublayers has a reflectivity greater than 90% at all wavelengths less than 1500 nm (or 250 nm to 1500 nm), greater than 80% at all wavelengths less than 2250 nm (or 250 nm to 2250 nm), and greater than 60% at all wavelengths less than 2500 nm (or 250 nm to 2500 nm).

[0096] In some embodiments, the composite radiative cooling material of this disclosure may include a stacked arrangement of porous materials configured at least in part based on the stacking and reflectivity trends shown in Figures 900 or 945. For example, the composite radiative cooling material of this disclosure may include a porous layer 120 comprising a number of sublayers configured based on a target reflectivity of the composite radiative cooling material.

[0097] In some implementations, sublayers (e.g., polyacrylic adhesive sublayers or any other suitable adhesive sublayers) may exist between each porous sublayer of the stacked sublayers of the UHMWPE material or any other porous layer stacked porous material (or between selected sublayers).

[0098] In some embodiments, the composite radiative cooling material of this disclosure, or at least one layer thereof, may exhibit... Figure 9A and Figure 9B One of the wavelength-dependent reflectivities shown. Having Figures 9A-9B Any material exhibiting the properties shown in the porous layer 120 may be the whole or a part of it.

[0099] Figure 10 The illustration shows the illustrative total solar reflectance of an illustrative UHMWPE layer as a function of total layer thickness according to some embodiments of this disclosure. The four data points (indicated by dots) in Figure 1000 correspond to the average of the reflectance data for the entire total solar energy spectrum of the four curves in Figure 900. As shown, the total solar reflectivity of the layer can be increased by increasing the thickness of the layer, which can be achieved by adding any of the following on top of a single 4-mil thick sublayer with a typical pore size of 500 nm (e.g., which may be referred to as the first sublayer): (i) a single 0.5-mil thick sublayer (specifically, e.g., a 10 μm thick film) with a typical pore size of 20 nm, (ii) a single 0.5-mil thick sublayer (specifically, e.g., a 12 μm thick film) with a typical pore size of 50 nm, or (iii) a single 1-mil thick sublayer (specifically, e.g., a 20 μm thick film) with a typical pore size of 100 nm (e.g., any of which may be referred to as the second sublayer), thereby forming a layer of composite radiative cooling material with a total thickness greater than 4 mils. In some embodiments, other first and second sublayers are arranged within the composite radiative cooling material to (at least partially) cause the composite radiative cooling material to exhibit a target solar reflectivity, a target thermal emissivity, or a target combination thereof.

[0100] In some embodiments, the composite radiative cooling material of this disclosure, or at least one layer thereof, may at least exhibit... Figure 10 The total solar reflectance shown at any data point. With Figure 10 Any material exhibiting the properties shown in the porous layer 120 may be the whole or a part of it.

[0101] In some embodiments, the porous layer 120 of the composite radiative cooling material 100 can be... Figure 2-4 , Figure 7-10 Or any of the materials identified in Table 1. In some embodiments, the porous layer 120 may exhibit... Figure 2-4 , Figure 7-10 Or any of the optical properties shown in Table 1. In some embodiments, the emitting layer 110 of the composite radiation cooling material 100 may be... Figure 5-6 Or any of the materials identified in Table 4. In some embodiments, the emitting layer 110 of the composite radiation cooling material 100 may exhibit Figure 5-6Or any of the optical properties shown in Table 4. In some embodiments, the reflective layer 130 of the composite radiation cooling material 100 may be any of the materials identified in Table 5. In some embodiments, the reflective layer 130 of the composite radiation cooling material 100 may exhibit any of the optical properties shown in Table 5.

[0102] In some embodiments, methods are provided for sealing or blocking the top, bottom, or side surfaces, or any combination thereof, of a porous layer of a composite radiative cooling material. The corresponding composite radiative cooling material may include a porous layer (e.g., porous layer 120) having unfilled pores (i.e., the corresponding pores maintaining voids), even if the porous material is in direct contact with different layers of the composite radiative cooling material. The porous layer may be arranged and / or configured such that any different material or layer in contact with the porous layer does not permeate (or permeates to a minimum such that the optical properties of the porous material are not substantially affected) the voids of the porous material. For example, as provided to improve bonding strength with adhesives, corona treatment, plasma treatment, chemical treatment, other surface treatments, or any combination thereof may be provided to treat the porous layer material and prevent adjacent layer material (i.e., material disposed directly above or below the porous layer) from filling the pores of the porous layer. In some embodiments, the adjacent layer material may be configured to have a refractive index similar to that of the porous material.

[0103] As mentioned, heat treatment, plasma treatment, or both can be applied to prevent (e.g., by sealing, blocking, or both) the pores of the porous layer from being filled by material from any other layer of the radiatively cooled material. For example, treating the composite radiatively cooled material by exposure to corona plasma (described further below) can prevent the filling of the pores in the porous layer. In another instance, treating the composite radiatively cooled material by heating (e.g., with or without a top coating (such as a sealant) as a top layer) can prevent the filling of the pores in the porous material. In yet another instance, treating the composite radiatively cooled material by exposure to ultraviolet light (e.g., with or without a top coating (such as a sealant) as a top layer) can prevent the filling of the pores in the porous material.

[0104] In some embodiments, a non-porous membrane (e.g., arranged as a membrane with a thickness of 100 μm or less, or 20 μm or less) of PE, PET, polycarbonate, or any other substrate material may be arranged as a layer of the composite radiative cooling material and may be thermally or chemically bonded to at least one other layer of the composite radiative cooling material. In some embodiments, an adhesive material (e.g., pressure-sensitive adhesive (PSA)) may be arranged as a layer of the composite radiative cooling material. In some embodiments, a hydrophobic material may be arranged as a layer of the composite radiative cooling material, and this hydrophobic material layer may be formed by applying heat, applying UV radiation, or waiting for a predetermined amount of time (e.g., in the case of a self-curing hydrophobic material) to cure the hydrophobic material. As a result of curing, the hydrophobic material may form a hard coating of the radiative cooling material. In some embodiments, the hard coating may be the top layer of the radiative cooling material, and the hard coating may be configured to be transparent in visible light and thermally reflective. Therefore, in some embodiments, the reflective layer 110 may be a hard coating.

[0105] In some embodiments, in addition to exhibiting high solar reflectivity, the porous layer 120 (e.g., a porous layer comprising hydrophobic and / or nonpolar porous plastics such as PE, UHMWPE, any aliphatic hydrocarbon, any other suitable plastic, or any combination thereof) may exhibit independent thermal emissivity that can be improved by integration into the composite radiative cooling material to further serve radiative cooling applications. In some embodiments, microporous (i.e., having an average pore size of at least 1 μm and less than 1 mm) plastics such as PE, UHMWPE, any aliphatic hydrocarbon, or any combination thereof are used as the porous layer 120. In some embodiments, to increase the emissivity of the composite radiative cooling material including the porous layer without reducing the reflectivity of the porous layer, a highly emissive film (e.g., transparent in the visible, UV, or both portions of the electromagnetic spectrum) may be arranged as an additional layer of the composite radiative cooling material. For example, materials exhibiting suitable transparency (i.e., suitable transmittance based on at least visible light) and emissivity for use as a top coating may include polycarbonate, PET, acrylic or acrylate hard coatings, PVDF, silicone, silica, and microscale glass spheres. Table 2-4 and Figure 5 Some non-limiting and illustrative examples of emissive materials that can serve as top coatings are shown.

[0106] In some embodiments, the porous layer 120 may not be UV-stable. Therefore, the top, bottom, or side surfaces of the porous material, or any combination thereof, may be coated with a protective film (which itself can be considered a layer or sublayer, e.g., if applied to the top or bottom surface of the porous material). In some embodiments, the protective film may be a non-permeable (e.g., relative to the pores of the porous material) UV-stable hard coating (e.g., the emissive layer 110 may also be used additionally as a protective film for the porous layer 120). In some embodiments, the protective film may be a non-permeable UV absorber (e.g., such as...). Figure 6 (as shown) or a UV-reflective coating, the use of which will also provide UV protection to adjacent porous materials. As used throughout this disclosure, non-permeable can be used to describe any first material that can be applied to a second material (e.g., a nanoporous or microporous material) without filling voids, pores or other openings in the material.

[0107] In some embodiments, the aforementioned techniques for arranging layers of composite radiative cooling material (including, but not limited to, arranging the emitting layer 110 over the porous layer 120 and arranging the porous layer 120 over the reflective layer 130, treating the material of the porous layer 120 to prevent pore filling, treating any layer to improve the bonding strength of an adhesive applied to the surface of the layer, or any combination thereof) can be used to manufacture materials having Figure 11-15 The composite radiation cooling material shown in any of the cross-sectional schematic diagrams.

[0108] Figure 11An illustrative cross-sectional schematic diagram of composite radiative cooling materials 1110, 1120, and 1130 according to some embodiments of the present disclosure is shown. As shown, from top to bottom of the cross section, composite radiative cooling material 1110 includes: an emitting layer 1112, which is a hard coating (e.g., visible light transparent, thermally emitting, or both), an adhesive layer 1114 (e.g., a UV-absorbing adhesive or a transparent adhesive), a porous layer 1116 (e.g., a void layer with a thickness greater than 200 μm), and a reflective layer 1118 (e.g., a substrate PET layer, which may also serve as a substrate). As shown, from top to bottom of the cross-section, the composite radiative cooling material 1120 includes: an emitting layer 1122, which is a hard coating (e.g., transparent in visible light, thermally emitting, or both), an adhesive layer 1124 (e.g., a UV-absorbing adhesive or a transparent adhesive), a second reflective layer 1125 (e.g., including PET, any other illustrative materials listed in Table 5, or any combination thereof), a porous layer 1126 (e.g., a void layer with a thickness greater than 200 μm), and a first reflective layer 1128 (e.g., a base PET layer, which may also serve as a substrate). As shown, from top to bottom of the cross-section, the composite radiative cooling material 1130 includes: an emitting layer 1132, which is a hard coating (e.g., visible light transparent, thermally emitting, or both), a third reflective layer 1133 (e.g., any suitable UV reflector), an adhesive layer 1134 (e.g., a UV-absorbing adhesive or a transparent adhesive), a second reflective layer 1135 (e.g., including PET, any other illustrative materials listed in Table 5, or any combination thereof), a porous layer 1136 (e.g., a void layer with a thickness greater than 200 μm), and a first reflective layer 1138 (e.g., a base PET layer, which may also serve as a substrate).

[0109] like Figure 11 As shown, any first reflective layer (e.g., below the corresponding porous layer, as shown) can be arranged to prevent moisture from entering the porous layer. Figure 11 Each radiation cooling material comprises a porous layer that may be a microporous layer, a nanoporous layer, or a combination thereof (e.g., a layer comprising corresponding microporous and nanoporous sublayers).

[0110] Composite radiative cooling materials 1110, 1120, and 1130 can each be considered as embodiments of composite radiative cooling material 100. For example, Figure 11 The corresponding hard coating shown may correspond to the emission layer 110. Figure 11 The corresponding porous layer shown can correspond to porous layer 120, and Figure 11 The corresponding bottom reflective layer shown may correspond to reflective layer 130. Figure 11The adhesive layer shown can be considered as an additional layer or as a sublayer (e.g., a sublayer of the emitting layer 110). Similarly, the corresponding second reflective layer (e.g., as shown in composite radiative cooling materials 1120 and 1130) and third reflective layer (e.g., as shown in composite radiative cooling material 1130) can be considered as additional layers or as sublayers (e.g., a sublayer of the emitting layer 110).

[0111] Figure 12 An illustrative cross-sectional schematic diagram of a composite radiative cooling material 1200 comprising a porous layer having multiple porous sublayers according to some embodiments of the present disclosure is shown. As shown, from top to bottom of the cross-section, the composite radiative cooling material 1200 includes: an emitting layer 1202, which is a hard coating (e.g., visible light transparent, thermally emitting, or both); an adhesive layer 1204 (e.g., a UV-absorbing adhesive or a transparent adhesive); a porous layer 1206 (e.g., a sublayer comprising N void films, as shown by dashed lines, where N can be determined based on the results of Figures 9-10, can be configured to achieve target optical properties, can be based on any other suitable criteria, or can be based on any combination thereof); and a reflective layer 1208 (e.g., a substrate PET layer, which may also serve as a substrate). For example, the emitting layer 1202 plus the adhesive layer 1204 may correspond to the emitting layer 110; the porous layer 1206 may correspond to the porous layer 120; and the reflective layer 1208 may correspond to the reflective layer 130.

[0112] In some embodiments, each of the plurality of void sublayers of the porous layer 1206 may comprise one or more nonwoven materials. These plurality of void layers can be used (e.g., in the integration of nonwoven materials) to generate pores with configurable sizes from 10 nm to 1000 nm. In some embodiments, the porous layer 1206 comprises a plurality of void sublayers to exhibit a porosity greater than 50%.

[0113] In some implementation schemes, Figure 11-12 Each of the various adhesive layers shown (and optionally any other intermediate material between the respective hard coating layer and the respective porous layer) can be considered a sublayer of the annotated porous layer (e.g., the corresponding porous layer includes, as a sublayer, the porous material, the adhesive, and any other material optionally disposed below the emitter layer material and above the porous layer material). In some embodiments, Figure 11-12 Each of the respective adhesive layers shown (and any intermediate membranes between the respective adhesive layers and porous layers) can be considered a sublayer of the emission layer (e.g., the corresponding emission layer includes a hard coating material, an adhesive, and any other materials optionally disposed below the emission layer material and above the porous layer material as sublayers). In some embodiments, Figure 11-12Any emitting layer (e.g., each of which may be emitting layer 110) may be arranged and / or configured together with an underlying adhesive layer (e.g., which may itself be considered a sublayer of the emitting layer) such that the emitting layer and the adhesive together contribute suitable optical properties for radiation cooling applications that depend on the corresponding composite radiation cooling material.

[0114] Figure 13 An illustrative cross-sectional schematic diagram of a composite radiative cooling material 1300 with a mirror film according to some embodiments of the present disclosure is shown. As shown, from top to bottom of the cross-section, the composite radiative cooling material 1300 includes: an emitting layer 1302, which is a hard coating (e.g., visible light transparent, thermally emitting, or both), a third reflective layer 1304 (e.g., any suitable UV reflector), and a porous layer 1306 (e.g., which may correspond to...). Figure 11-12 The reflective film consists of a porous layer (e.g., a mirror layer 1308, or a second reflective layer) and a first reflective layer 1310 (e.g., a substrate PET layer, which may also serve as a substrate). For example, the reflective film can be any film that reflects at least a large portion of the visible spectrum, such as any suitable metallic film. In some embodiments, the reflective film may include at least two sublayers, wherein the bottom sublayer comprises a polymer or any other suitable substrate material, and the top sublayer comprises a metallic film (e.g., aluminum, silver, or gold), wherein the metallic film causes the reflective film to exhibit high solar reflectivity.

[0115] Figure 14 An illustrative cross-section of various composite radiative cooling material arrangements according to some embodiments of this disclosure is shown. For example... Figure 14 As shown, each corresponding porous layer can correspond to Table 1 or Figure 2-4 Any of the illustrative porous layers, and may be porous layer 120; each corresponding product reflector may correspond to any of the illustrative reflective layers in Table 5, and may be reflective layer 130; and each corresponding top layer (e.g., including top layer 1412, top layer 1442, multilayer optical film 1422 (which is an illustrative type of top layer) and top skin 1432 (which is another illustrative type of top layer)) may correspond to Tables 2-4 or Figure 5 Any of the descriptive emission layers, and may be emission layer 110.

[0116] In some implementation schemes, such as Figure 14The product reflector shown serves as a base layer for the composite radiative cooling material, and this layer may be disposed over an optional adhesive layer. The optional adhesive layer may, for example, bond the composite radiative cooling material to a substrate, panel, or any surface requiring cooling, such as the surface of a building, vehicle, or enclosure, or a heat exchanger. As mentioned, the composite radiative cooling material itself may be a radiative cooling film, wherein the adhesive mechanically and thermally bonds the radiative cooling film to the substrate, panel, surface requiring cooling, or any other suitable load.

[0117] Commercial reflectors typically exhibit a total solar reflectivity of 80-90%, and can be positioned between multiple layers of composite radiative cooling material to provide a more optimized structure for cooling applications. In addition to those mentioned above, other examples of commercial reflectors include PET (or any other polymer film) with an aluminum reflective coating; a silver layer (e.g., which may be applied to PET or any other polymer layer); white PET or any other polymer material loaded with BaSO4, TiO2, or both; white PET or any other polymer material with voids; and reflectors using UVA (e.g., including...). Figure 6 The above-described materials, impregnated with blue-shifted UVA and typical UVA (e.g., as particles impregnated in the layers or sublayers), are used to improve the UV resistance of the composite radiative cooling material in outdoor applications; or reflective metal (e.g., silver or aluminum) coatings. In some embodiments, as mentioned when attaching the commercial reflector to the materials in Table 5, the commercial reflector may be a white roofing material, such as TPO, PVC, any other white roofing material, or any combination thereof.

[0118] like Figure 14 As shown, a porous layer can be disposed on top of a commodity reflector (e.g., on the side facing the sun or sky in an installation orientation for radiative cooling of a load). When configured with a specific combination of porosity, pore size, and thickness, the porous layer can, by itself, exhibit sufficient reflectivity to serve the cooling application. For example, the porous layer can exhibit optical properties of high reflectivity and high transmittance (or non-absorption). In some embodiments, the porous layer can highly transmit selected wavelengths that are not strongly reflected by the porous layer (e.g., such that all wavelengths of interest are strongly reflected or transmitted but not absorbed).

[0119] Figure 14The composite radiative cooling material 1410, as shown, comprises, from top to bottom: a top layer 1412 (e.g., an emitting layer 110), a porous layer 1414, a merchandise reflector 1416 (e.g., a reflective layer 130), and an optional adhesive layer 1418. The porous layer 1414, the merchandise reflector 1416, and the optional adhesive layer 1418 may be the same as or similar to the porous layer, merchandise reflector, and optional adhesive layer disposed in some or all of the composite radiative cooling materials 1420, 1430, and 1440, respectively.

[0120] Figure 14 The composite radiative cooling material 1420, as shown, comprises, from top to bottom: a multilayer optical film 1422 (e.g., an emitting layer 110), a porous layer 1424, a commodity reflector 1426 (e.g., a reflective layer 130), and an optional adhesive layer 1428. The multilayer optical film 1422 can act as a layer that is both reflective and emissive, for example, based on being configured to provide high reflectivity in the UV portion of the solar spectrum, high transmittance in the non-UV portion of the electromagnetic spectrum, and high emissivity in the far-infrared portion of the electromagnetic spectrum. Additional properties that the multilayer optical film 1422 may provide to the composite radiative cooling material 1420 include a hard coating and anti-fouling properties. In some embodiments, the composite radiative cooling material 1420 further includes a fourth layer of emitting film (e.g., the emitting film comprising any emitting layer material listed in Table 4) coated on the top surface of the multilayer optical film 1422. For example, applying an emitting film as a top coating of the multilayer optical film 1422 can enable the emitting film and the multilayer optical film 1422 together to contribute suitable optical properties to the use of the composite radiation cooling material 1420 in radiation cooling applications.

[0121] Figure 14 The composite radiative cooling material 1430, as shown, comprises, from top to bottom: a top skin 1432 (e.g., radiating layer 110), a porous layer 1434, a commodity reflector 1436 (e.g., reflective layer 130), and an optional adhesive layer 1438. The top skin 1432 can mechanically seal the pores of the porous layer 1434 to prevent filling of these pores, as mentioned above and further described below.

[0122] As mentioned above, and can be combined with Figure 14 Radiative cooling materials and Figure 1 , Figure 11-13 and Figure 15Those related to this exhibit partial radiative cooling performance due to the porosity of the porous layer 120 (including the porosity extending to the top and bottom surfaces of the membrane). For example, the top and bottom surfaces of the porous layer 120 may comprise solid materials (e.g., any plastics listed in Table 1 or described in relation to Table 1) and voids within the solid materials. To improve the optical properties of the composite radiative cooling material, the top layer of the composite radiative cooling material (e.g., comprising a multilayer optical film, a top skin, or any other sky-facing layer) may comprise, or may be itself, a coating that provides UV protection to the underlying layer and has high emissivity in the far-infrared (e.g., 8.0–13.0 μm) spectrum, compared to a single porous layer.

[0123] When applied over a porous layer, the top layer cannot be significantly permeated through the pores. In some embodiments, minimal or negligible permeation of the porous material's pores can be achieved by using a water-based top layer combined with a hydrophobic porous material. In other embodiments, the top layer can be made impermeable to the porous layer by having a sufficiently large colloid (e.g., micron-sized) that blocks the uppermost pores of the porous membrane (e.g., nanon-sized), thereby preventing further permeation of the top layer material into the porous membrane. In other embodiments, the pores can be sealed mechanically, such as by melting the uppermost volume of the nanoporous membrane (e.g., to reduce the size of the top pores, but not to zero), or by bonding a top skin layer (e.g., such as top skin 1432) over the pores. Sealing the pores on the bottom side of the nanoporous membrane can also be desirable to prevent moisture from entering the membrane (e.g., where...). Figure 11-13 The bottom reflective layer shown and Figure 14 (The reflector in the product can prevent moisture from entering the bottom side of the nanoporous membrane). All the methods described above for applying a membrane or layer above the top of a porous layer can also be used to apply a membrane or layer below the bottom side of a porous layer. The top skin layer, bottom skin layer, or both may also have properties of high transparency and high emissivity in the UV absorption, visible spectrum, and near-infrared spectrum.

[0124] Optionally, the top layer (e.g., such as...) Figure 14 As shown elsewhere in this disclosure, and which may correspond to the emitting layer 110, the top layer may also provide mechanical protection for the underlying film (i.e., “hard coating” properties, such as scratch resistance, abrasion resistance, etc.). Optionally, the top layer may additionally or extraneously provide antifouling properties, which improves the film’s ability to remain clean and free from debris, dust, or other substances or any combination thereof that could damage the optical properties of the composite radiative cooling material.

[0125] Figure 14 It also includes a composite radiative cooling material 1440, as shown, which, from top to bottom, comprises: a top layer 1442 (e.g., an emitting layer 110), a porous layer 1444, and an aluminum or silver plating 1446 (e.g., which may be a mirror film, such as...). Figure 13As shown, and which may correspond to reflective layer 130), and optional adhesive layer 1448. As expressed by relative thickness (not to scale), aluminum or silver plating 1446 may be comparable to... Figure 14 Any of the reflectors shown are thin, and thus the overall size of the composite radiative cooling material 1440 can be reduced (e.g., compared to the composite radiative cooling material 1410).

[0126] Figure 15 An illustrative cross-section of a composite radiative cooling material 1500 including a multi-layer top layer 1502 according to some embodiments of the present disclosure is shown. As shown, from top to bottom, the composite radiative cooling material 1500 includes: a multi-layer top layer 1502 (e.g., the entirety or a portion of the emitting layer 110, which may be further configured to reflect more than 50% of incident ultraviolet radiation), an adhesive layer 1504, and a reflective layer 1506 (e.g., reflective layer 130). In some embodiments, the multi-layer top layer 1502 comprises a stack of alternating sublayers, each alternating sublayer comprising a corresponding sublayer of a first material (e.g., indicated by short dashed lines) and a corresponding sublayer of a second material (e.g., indicated by dotted dashed lines). These alternating sublayers (which may have any suitable number) may be configured to increase the solar reflectivity of the composite radiative cooling material 1500, provide suitable emissivity, protect the reflective layer 1506, or any combination thereof. In some embodiments, the multi-layer top layer 1502 may correspond to a multilayer optical film 1422. Therefore, the multilayer optical film 1422 may be an emissive material (e.g., the emissive material of the emissive layer 110), and the emissive material of the multilayer optical film 1422 may include alternating sublayers associated with the respective first and second materials (e.g., by selecting, arranging, configuring the respective first and second materials or any combination thereof to provide suitable emissivity and reflectivity).

[0127] The following describes how composite radiative cooling material 1500 can be composite radiative cooling material 100 (or other composite radiative cooling materials described in this disclosure, including at least...) Figure 11-14 Implementations of the reflective layer 1506 (and those in Table 6). In some implementations, the reflective layer 1506 may comprise a porous polymer or be a porous polymer itself (e.g., any porous polymer described in this disclosure, including at least those in Table 1 and...). Figure 2-4(as shown in the illustrations). Therefore, a portion of the reflective layer 1506 may correspond to the porous layer 120. For example, the reflective layer 1506 may include a porous sublayer (e.g., which may constitute the porous layer 120), and the pores of this porous sublayer may be configured to extend to the top surface of the reflective layer 1506 but not to the bottom of the reflective layer 1506, such that the reflective layer 1506 may include a reflective sublayer (e.g., which may constitute the reflective layer 130 and may be impregnated with light-scattering particles) disposed below the porous sublayer of the reflective layer 1506. In some embodiments, the reflective layer 1506 (e.g., as a porous polymer, or others) may be at least partially impregnated with light-scattering particles (such as TiO2, BaSO4, CaCO3, or any other suitable colloid).

[0128] It should be noted that Figure 11-15 The cross-section shown is not drawn to scale. In some implementations, Figure 11-15 The relative layer thicknesses (including sublayer thicknesses) of the cross-sections shown may correspond to the relative thicknesses of the respective composite radiative cooling materials manufactured. However, the composite radiative cooling materials provided according to embodiments of this disclosure need not follow this principle. Figure 11-15 Any relative thickness shown in the illustrative cross-section.

[0129] Figure 16 An illustrative cooling system 1600 including a composite radiative cooling material 1610 is shown according to some embodiments of the present disclosure. The composite radiative cooling material 1610 may be any composite radiative cooling material described in this disclosure, including at least Figure 1 , Figure 11-15 And those in Table 6; therefore, the composite radiative cooling material 1610 can be configured to include at least three layers (e.g., a reflective layer 130 with a reflective material, a porous layer 120 with a porous material, and an emitting layer 110 with an emitting material), wherein the arrangement of the three layers causes the composite radiative cooling material 1610 to exhibit a total solar reflectivity greater than 85% and a thermal emissivity greater than 85% in the wavelength range of 8.0 to 13.0 μm.

[0130] The composite radiative cooling material 1610 is arranged to cool any cooling load 1620 based on thermal coupling with the cooling load and based on the optical properties exhibited by the composite radiative cooling material 1610. In some embodiments, the composite radiative cooling material is thermally coupled to the cooling load 1620 via a heat exchange interface 1630. The heat exchange interface 1630 can be any suitable thermal conductor that allows heat radiated from the composite radiative cooling material 1610 to be drawn from the cooling load 1620 (i.e., the temperature of the cooling load 1620 is reduced based on conduction through the heat exchange interface 1630 and thermal emission from the composite radiative cooling material 1610). For example, the cooling load 1620 may be inside a building, vehicle, or enclosure (e.g., any electronic enclosure), the heat exchange interface 1630 may be the roof / roof or other upward-facing surface of the building, vehicle, or enclosure, and the composite radiative cooling material 1610 may be arranged to provide cooling to the cooling load 1620 based on being applied to the roof / roof or other upward-facing surface. As used herein, cooling load 1620 inside a building, vehicle, or enclosure may mean that cooling load 1620 is an internal volume of the building, vehicle, or enclosure, that cooling load 1620 is any heat-generating object within the internal volume of the building, vehicle, or enclosure, or that cooling load 1620 is any combination thereof.

[0131] In some embodiments, instead of or in addition to the heat exchange interface 1630, the composite radiative cooling material 1610 may also be thermally coupled to the cooling load 1620 via one or more of the heat exchanger 1640, coolant fluid 1650, or heat accumulator 1660. For example, the composite radiative cooling material 1610 may be arranged to cool the heat exchanger 1640, coolant fluid 1650, heat accumulator 1660, or any combination thereof, wherein the heat exchanger 1640, coolant fluid 1650, heat accumulator 1660, or any combination thereof is further arranged to cool the cooling load 1620.

[0132] In some implementations, the cooling load 1620 may be at least one of a refrigerant, a cooling jacket of an equipment, a heat storage tank, a heat source, an air conditioning system, or a refrigerant regulating system.

[0133] In some embodiments, the composite radiative cooling material 1610 may be thermally coupled to the cooling load 1620 by applying the composite radiative cooling material 1610 to the panel and thermally coupling the panel to the load. For example, the panel may be a heat exchange interface 1630 or a heat exchanger 1640. In other instances, the panel may be thermally coupled to any one or more of the heat exchange interface 1630, the heat exchanger 1640, the coolant fluid 1650, or the heat accumulator 1660.

[0134] In some embodiments, the composite radiative cooling material 1610 can cool an outdoor space, and the cooling load 1620 can be a specific portion of the outdoor air (e.g., above or around the area covered by the composite radiative cooling material 1610). For example, the cooling load 1620 can be a heat island in the wider outdoor environment (i.e., a portion of the outdoor space that is hotter than the surrounding ambient air under certain solar radiation conditions), and the composite radiative cooling material 1610 can be arranged to reduce the temperature of the heat island to approach (if not lower than) the average temperature associated with the ambient air and the wider outdoor environment.

[0135] Figure 17 A method 1700 for arranging layers of a composite radiative cooling material according to some embodiments of the present disclosure is shown. Method 1700 includes arranging a third layer (e.g., an emitting layer 110) over a second layer (e.g., a porous layer 120) and arranging the second layer over the first layer (e.g., a reflective layer 130), wherein the first layer comprises a reflective material, the second layer comprises a porous material, and the third layer comprises an emitting material, such that the composite material comprising the first, second, and third layers (e.g., a composite radiative cooling material 100) exhibits a total solar reflectivity greater than 85% and a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm. For example, method 1700 can be used to arrange... Figure 1 , Figure 11-16 Or any composite radiative cooling material shown in Table 6, or any other composite radiative cooling material consistent with the subject matter of this disclosure.

[0136] In some embodiments, method 1700 further includes applying an adhesive (e.g., any adhesive layer described in this disclosure, including at least...) Figure 11 and 12 Those shown) are connected to the corresponding sides of the second layer, wherein the adhesive bonds the second layer to the first layer or the third layer respectively.

[0137] In some embodiments, method 1700 further includes applying an adhesive (e.g., any adhesive layer described in this disclosure, including at least...) Figure 14 Those shown) are bonded to a third layer, wherein the third layer and the adhesive together exhibit a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm.

[0138] In some embodiments, regarding the surface treatments described above (e.g., including corona treatment, plasma treatment, chemical treatment, or any combination thereof) to prevent material permeation through the pores of the porous material, method 1700 further includes disposing a third layer over the second layer and the second layer over the first layer. This includes disposing the third, second, and first layers such that neither the first nor the third layer permeates the porous material of the second layer. In some embodiments, method 1700 further includes arranging the pores of the porous material along the thickness direction of the porous material between the top and bottom surfaces (including the top and bottom surfaces). Therefore, method 1700 may include the porous material being arranged and / or configured such that the pores of the porous material extend to the top and bottom surfaces of the material.

[0139] In some implementations, method 1700 further includes configuring the thickness of the porous material (e.g., based on the results listed in Table 1 or the results shown in Figures 9-10) to exhibit a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm.

[0140] In some embodiments, method 1700 further includes distributing a UV absorber, such as a blue-shifting UV absorber (e.g., as shown in the image), within the third layer. Figure 6 (As shown). For example, UV absorbers can exhibit solar transmittance greater than 90% at wavelengths greater than 405 nm and less than 5% at wavelengths less than 365 nm. As another example, blue-shift UV absorbers can exhibit solar transmittance greater than 90% at wavelengths greater than 380 nm and less than 5% at wavelengths less than 325 nm.

[0141] In some embodiments, method 1700 further includes arranging a UV reflector, such as any colloidal particles mentioned above, within the third layer. For example, arranging the UV reflector may include impregnating the third layer with a material made of TiO2, BaSO4, CaCO3, or any other suitable colloid, wherein the colloid size may be configured based on the target reflectivity, based on the ability to block the pores of the porous material (i.e., due to being larger than the pores), or based on both factors.

[0142] Figure 18 A method 1800 for radiative cooling using a composite radiative cooling material according to some embodiments of the present disclosure is shown. Method 1800 includes step 1802, whereby the radiative cooling material (e.g., composite radiative cooling material 100, composite radiative cooling material 1610, ...) is applied to the surface of the material. Figure 11-15The method 1800 includes a composite radiative cooling material (or any other composite radiative cooling material consistent with the subject matter of this disclosure) thermally coupled to a load (e.g., cooling load 1620), wherein the radiative cooling material comprises a first layer, a second layer, and a third layer having a total solar reflectivity greater than 85% and a thermal emissivity greater than 85% in the wavelength range of 8.0 to 13.0 μm, wherein the first layer comprises a reflective material, the second layer comprises a porous material, and the third layer comprises an emissive material. Method 1800 further includes step 1804, which causes the radiative cooling material to cool the load based on the total solar reflectivity and the thermal emissivity.

[0143] In some embodiments, method 1800 includes thermally coupling the composite radiative cooling material to the cooling load using any one or more of a heat exchange interface 1630, a heat exchanger 1640, a coolant fluid 1650, or a heat accumulator 1660.

[0144] In some embodiments, composite radiative cooling materials (e.g., composite radiative cooling material 100, composite radiative cooling material 1610, etc.) are used. Figure 11-15 Any composite radiation cooling material shown or any other composite radiation cooling material consistent with the subject matter of this disclosure) is applied to a substrate thereon (e.g., via an underlayer adhesive (such as...) Figure 14 The substrate (as shown) or via any other suitable attachment mechanism may be, or may additionally include, a highly emissive (e.g., black) substrate having an emissivity greater than 80% in the wavelength range of 8 to 13 μm, for example. For example, the substrate may be any black material that provides suitable mechanical properties for supporting the composite radiative cooling material. The substrate may also optionally protect the composite radiative cooling material by preventing water from penetrating or entering the bottom of the composite radiative cooling material.

[0145] The above process is intended to illustrate rather than limit. Those skilled in the art will recognize that the steps of the methods described herein can be omitted, modified, combined, rearranged, or any combination thereof, and any additional steps can be performed without departing from the scope of the invention.

[0146] The above is merely an explanation of the principles of this disclosure, and those skilled in the art can make various modifications thereto without departing from the scope of this disclosure. The above embodiments are presented for illustrative purposes and not for limitation. This disclosure may also take many forms other than those expressly described herein. Therefore, it is emphasized that this disclosure is not limited to the methods, systems, and apparatus expressly disclosed, but is intended to include variations and modifications thereof, all of which are within the spirit of the following numbered paragraphs.

Claims

1. Composite radiative cooling material, comprising: The first layer contains reflective material; The second layer contains porous material; and The third layer contains the emission material, in which: The composite radiative cooling material exhibits a total solar reflectivity greater than 85% and a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm.

2. The composite radiative cooling material according to claim 1, wherein: The first layer, the second layer, and the third layer are arranged in a vertically stacked configuration; and The third layer is arranged to face the sky directly, the second layer is arranged below the third layer, and the first layer is arranged below the second layer.

3. The composite radiation cooling material according to claim 1, wherein the reflective material exhibits a total solar reflectivity of greater than 75%.

4. The composite radiative cooling material according to claim 1, wherein the first layer comprises at least one of the following: white polyethylene terephthalate (PET), white thermoplastic polyurethane, aluminum-plated PET, silver-plated PET, polytetrafluoroethylene, thermoplastic olefin, or polyvinyl chloride.

5. The composite radiation cooling material according to claim 1, wherein the porous material comprises a plurality of pores with an average pore size of 100 nm to 1000 nm.

6. The composite radiation cooling material according to claim 1, wherein the porous material comprises a plurality of pores, the plurality of pores causing the porosity of the porous material to be greater than 75%.

7. The composite radiative cooling material of claim 1, wherein the thickness of the porous material is at least 0.001 inches.

8. The composite radiative cooling material according to claim 1, wherein the porous material comprises at least one of the following: polyethylene, high molecular weight polyethylene, ultra-high molecular weight polyethylene, polysulfone, polyethersulfone, polyamide, polyethylene terephthalate, or fluorinated polymer.

9. The composite radiative cooling according to claim 1, wherein the porous material exhibits a total solar reflectivity of greater than 75% and a total solar absorptivity of less than 5%.

10. The composite radiation cooling according to claim 1, wherein the pores of the porous material are arranged between the top surface and the bottom surface along the thickness direction of the porous material, including the top surface and the bottom surface.

11. The composite cooling material of claim 1, wherein the second layer further comprises an adhesive layer bonded to a corresponding side of the second layer.

12. The composite cooling material according to claim 11, wherein the adhesive bonds the second layer to the first layer or the third layer respectively.

13. The composite radiation cooling material according to claim 1, wherein the emitting material exhibits a total solar absorptivity of less than 5%.

14. The composite radiation cooling material of claim 13, wherein the third layer further comprises a UV absorber (UVA), wherein the UVA exhibits: Solar transmittance greater than 90% at wavelengths greater than 405 nm; and Solar radiation transmittance of less than 5% at wavelengths less than 365 nm.

15. The composite radiation cooling material of claim 13, wherein the third layer further comprises a blue-shifted UV absorber (UVA), wherein the blue-shifted UVA exhibits: Solar transmittance greater than 90% at wavelengths greater than 380 nm; and Solar radiation transmittance of less than 5% at wavelengths less than 325 nm.

16. The composite radiation cooling material according to claim 1, wherein the emitting material comprises at least one of the following: thermoplastic polyurethane (TPU), polyethylene terephthalate (PET), polycarbonate, polyvinylidene fluoride (PVDF), poly(methyl methacrylate) (PMMA), or cyclic olefin copolymer (COC).

17. The composite radiation cooling material of claim 1, wherein the emitting material comprises a film exhibiting a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm.

18. The composite radiation cooling material of claim 1, wherein the emitting material comprises a film, and the third layer further comprises an adhesive bonded to the film, wherein the film and the adhesive together exhibit a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm.

19. The composite radiative cooling material according to claim 1, wherein no layer adjacent to the second layer penetrates the porous material.

20. The composite radiative cooling material according to claim 1, wherein the third layer is formed based on a deposited aqueous film, the aqueous film comprising at least one of the following resins: PVDF, polyurethane, or acrylic resin.

21. The composite radiation cooling material according to claim 1, wherein the third layer comprises a multilayer optical film, wherein the multilayer optical film comprises the emitting material and further comprises an additional reflective material.

22. The composite radiative cooling material of claim 21, further comprising a fourth layer containing an additional radiating material, wherein the fourth layer is disposed above the third layer.

23. A method for manufacturing a composite radiative cooling material, the composite radiative cooling material comprising: The first layer contains reflective material; The second layer contains porous material; and The third layer contains the emission material, in which: The composite radiative cooling material has a total solar reflectivity of greater than 85% and a thermal emissivity of greater than 85% in the wavelength range of 8.0 to 13.0 μm. The method includes: The third layer is arranged above the second layer, and the second layer is arranged above the first layer.

24. The method of claim 23, further comprising attaching an adhesive to a respective side of the second layer, wherein the adhesive bonds the second layer to the first layer or the third layer, respectively.

25. The method of claim 23, further comprising attaching the adhesive to the third layer, wherein the third layer and the adhesive together exhibit a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm.

26. The method of claim 23, wherein disposing the third layer over the second layer and disposing the second layer over the first layer comprises: The third layer, the second layer, and the first layer are arranged such that neither the first layer nor the third layer penetrates the porous material of the second layer.

27. The method of claim 23, further comprising configuring the thickness of the porous material, wherein the thickness at least partially causes the composite radiative cooling material to exhibit thermal emissivity.

28. The method of claim 23, further comprising arranging the pores of the porous material between a top surface and a bottom surface along the thickness direction of the porous material, including the top surface and the bottom surface.

29. The method of claim 23, further comprising distributing a UV absorber (UVA) within the third layer, wherein the UVA exhibits: Solar transmittance greater than 90% at wavelengths greater than 405 nm; and Solar radiation transmittance of less than 5% at wavelengths less than 365 nm.

30. The method of claim 23, further comprising distributing a blue-shifting UV absorber (UVA) within the third layer, wherein the blue-shifting UVA exhibits: Solar transmittance greater than 90% at wavelengths greater than 380 nm; and Solar radiation transmittance of less than 5% at wavelengths less than 325 nm.

31. A method for cooling a load using a composite radiative cooling material, said composite radiative cooling material comprising: The first layer contains reflective material; The second layer contains porous material; and The third layer contains the emission material, in which: The composite radiative cooling material has a total solar reflectivity greater than 85% and a thermal emissivity greater than 85% in the wavelength range of 8 to 13 μm; the method includes: Thermally couple the radiation cooling material to the load; and The radiation-cooling material cools the load based on total solar reflectivity and thermal emissivity.

32. The method of claim 31, wherein the load is located inside a building or vehicle, and thermally coupling the radiative cooling material to the load comprises applying the radiative cooling material to a surface of the building or vehicle exposed to the sky.

33. The method of claim 31, wherein thermally coupling the radiative cooling material to the load comprises: The radiation cooling material is thermally coupled to the heat exchanger; and The heat exchanger is thermally coupled to the load.

34. The method of claim 31, wherein thermally coupling the radiative cooling material to the load comprises: The radiation cooling material is used to cool the coolant fluid; and The load is cooled using the coolant fluid.

35. The method of claim 31, wherein the load is at least one of the following: refrigerant; The equipment's cooling jacket; Thermal storage tank; Heat source; Air conditioning system; or Coolant regulation system.

36. The method of claim 31, wherein thermally coupling the radiative cooling material to the load comprises: The radiation cooling material is applied to the panel; and The panel is thermally coupled to the load.

37. The method of claim 31, wherein the load is a heat island in an outdoor environment, and cooling the load comprises reducing the temperature of the heat island to bring it closer to the average temperature of the outdoor environment.

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