Solar energy absorbing and radiative cooling articles and methods

Abstract

Passive cooling articles can include a first element defining a high absorbance in the atmospheric infrared wavelength range and a high average reflectivity in the solar wavelength range. The first element can define a first major surface (114, 214, 314, 414) positioned and shaped to reflect solar energy in the solar wavelength range to an energy absorber (108, 208, 308, 408, 508, 608) spaced a distance from the first major surface (114, 214, 314, 414). The energy absorber (108, 208, 308, 408, 508, 608) can be a heating panel or a photovoltaic cell. A second element can define a second major surface (116, 216, 416) of high thermal conductivity and thermally coupled to the first element to transfer thermal energy from the second element to the first element to cool the second element.

Description

Summary of the Invention

[0001] This disclosure relates to articles, processes, and techniques for solar absorption and radiative cooling. In some embodiments, this disclosure relates to articles (generally described as integrated or hybrid articles) that provide the dual functionality of absorbing energy and cooling. In some embodiments, these articles include (1) a high reflectivity element for reflecting solar energy to an energy absorber for solar energy conversion and (2) a high emissivity element for cooling. In some aspects, solar energy can be converted into thermal or electrical energy. In some aspects, this technology can be used with heating and cooling systems, such as heat exchangers attached to buildings. Certain types of heat exchangers may include, but are not limited to, absorption coolers and steam condensers. In some aspects, this technology can be used with power generators that may include photovoltaic cells. Articles may include a variety of macrostructures, microstructures, or even nanostructures to facilitate the specific properties described herein. As used herein, the term “article” may also be described as an apparatus or system, depending on the context of use.

[0002] In some embodiments, this disclosure relates to a passive cooling article comprising a first element having a first absorbance greater than or equal to 0.5 in the atmospheric infrared wavelength range of 8 to 13 micrometers and a first average reflectance at least partially defined as greater than or equal to 80% in the solar wavelength range of 0.4 to 2.5 micrometers. The first element includes a first primary surface positioned and shaped to reflect solar energy in the solar wavelength range to an energy absorber spaced apart from the first primary surface. The passive cooling article includes a second element having a thermal conductivity greater than 0.1 W / mK. The second element is thermally coupled to a second primary surface of the first element to transfer thermal energy from the second element to the first element to cool the second element.

[0003] In some embodiments, the first element may include a multilayer optical film. In some embodiments, the first element may include an ultraviolet-reflective multilayer optical film. In some embodiments, the energy absorber may include an internal volume to contain a fluid that can be heated by solar energy. In some embodiments, the energy absorber may include a photovoltaic cell. In some embodiments, the first element may be a mirrored solar mirror in the solar wavelength range. In some embodiments, the first main surface may have a curved shape. In some embodiments, the curved shape may have a parabolic curve. In some embodiments, the curved shape may have a composite parabolic curve.

[0004] In some embodiments, this disclosure relates to a passive cooling article comprising a first element having a first region of a first primary surface, the first element defining a first absorbance greater than or equal to 0.5 in the atmospheric infrared wavelength range of 8 to 13 micrometers, and at least partially defining a first average reflectance greater than or equal to 80% in the solar wavelength range. The passive cooling article includes a second element defining a thermal conductivity greater than 0.1 W / mK. The second element is thermally coupled to the first region of the second primary surface defined by the first element to transfer heat from the second element to the first element to cool the second element. The passive cooling article includes an energy absorber having a second region of the first primary surface. The energy absorber is configured to receive solar energy in the solar wavelength range of 0.35 to 2.5 micrometers. The first region of the first primary surface is positioned and shaped to guide reflected solar energy in the solar wavelength range to the second region.

[0005] In some embodiments, the energy absorber may include an internal volume to contain a fluid that can be heated using solar energy. In some embodiments, a first region of the first main surface may have a planar shape. In some embodiments, the energy absorber may include a photovoltaic cell. In some embodiments, a first vector perpendicular to at least a portion of the first region of the first main surface may define an element angle with a second vector perpendicular to at least a portion of a second region of the first main surface. The element angle may be greater than or equal to 90 degrees and less than or equal to 175 degrees. In some embodiments, the first element may include a diffuse solar mirror in the solar wavelength range. In some embodiments, the diffuse solar mirror may include a microporous polymer layer or an array of inorganic particles having an effective D90 particle size of up to 50 micrometers. In some embodiments, the article may also include a plurality of first elements and a plurality of second elements arranged in an alternating array between a first end region and a second end region. In some embodiments, the second region of the first main surface may have a curved shape.

[0006] In some embodiments, this disclosure relates to a passive cooling system including an energy absorber configured to receive solar energy in the solar wavelength range of 0.35 micrometers to 2.5 micrometers. The passive cooling system may include a solar mirror element defining a first absorbance greater than or equal to 0.6 in the atmospheric infrared wavelength range of 8 to 13 micrometers and a first average reflectance at least partially defined as greater than or equal to 80% in the solar wavelength range. The solar mirror element may include a first primary surface shaped to guide reflected solar energy in the solar wavelength range to the energy absorber. The passive cooling element may include a coolable element defining a thermal conductivity greater than 0.1 W / mK. The coolable element may be thermally coupled to a second primary surface of the solar mirror element to transfer heat from the coolable element to the solar mirror element to cool the coolable element.

[0007] In some embodiments, the energy absorber, coolable element, or both may be thermally coupled to an absorption cooler subsystem. In some embodiments, the energy absorber, coolable element, or both may be thermally coupled to a steam condenser subsystem. In some embodiments, the energy absorber may include a photovoltaic module, and the coolable element may be thermally coupled to cool the photovoltaic module. In some embodiments, the photovoltaic module may be designed to absorb solar energy in the range of 0.35 micrometers to 1.6 micrometers. In some embodiments, the photovoltaic module may be designed to absorb solar energy in the range of 0.35 micrometers to 1.1 micrometers. In some embodiments, the photovoltaic module may be designed to absorb solar energy in the range of 0.35 micrometers to 0.9 micrometers.

[0008] As used herein, the term "passive cooling" refers to passive radiative cooling that provides cooling without consuming energy from an energy source, such as a battery or other power source. Passive cooling can be defined as the opposite of "active cooling," which consumes an energy source (e.g., cooling via an air conditioning unit with an electrically driven compressor and fan).

[0009] As used herein, the term "light" refers to electromagnetic energy having any wavelength. In some embodiments, light means electromagnetic energy having a wavelength of up to 20 micrometers or up to 13 micrometers. In some embodiments, light means radiant energy in the electromagnetic spectrum region from 0.25 micrometers to 20 micrometers.

[0010] As used herein, the “solar region” or “solar wavelength range” of the electromagnetic spectrum refers to a portion of the electromagnetic spectrum that partially or completely includes sunlight or solar energy. This solar region may include at least one of visible, ultraviolet, or infrared wavelengths. The solar region can be defined as wavelengths ranging from 0.4 micrometers to 2.5 micrometers (or greater than or equal to 0.3 micrometers, 0.35 micrometers, or even 0.4 micrometers, or less than or equal to 3.5 micrometers, 3 micrometers, or even 2.5 micrometers).

[0011] As used herein, the terms “infrared,” “infrared region,” or “infrared wavelength range” refer to light wavelengths greater than or equal to 0.8 micrometers and less than 1 millimeter. “Near-infrared region” refers to wavelengths from 0.8 micrometers to 4 micrometers. “Mid-infrared region” refers to wavelengths from 4 micrometers to 20 micrometers.

[0012] As used herein, the “atmospheric infrared region” or “atmospheric infrared wavelength range” of the electromagnetic spectrum refers to the portion of the electromagnetic spectrum that partially or completely includes wavelengths that can be partially transmitted through the atmosphere. The atmospheric infrared region may include atmospheric windows, which are typically defined as wavelengths ranging from 8 to 13 micrometers, 7 to 14 micrometers, or even 6 to 14 micrometers. The atmospheric infrared region may also include the intermediate infrared region from 4 to 20 micrometers.

[0013] As used herein, the terms “visible,” “visible region,” or “visible wavelength range” refer to wavelengths from 0.4 micrometers to 0.8 micrometers.

[0014] As used in this article, the term "material" refers to a single sheet of material or a composite material.

[0015] As used herein, the terms “transmittance” and “transmittance” refer to the ratio of the total transmittance of a material layer to the total transmittance received by the material, which can account for the effects of absorption, scattering, reflection, etc. Transmittance (T) can be expressed in the range of 0 to 1 or as a percentage (T%).

[0016] The term "average transmittance" refers to the arithmetic mean of the transmittance measurements of a sample over a certain wavelength range.

[0017] Transmittance can be measured using the method described in ASTM E1348-15e1 (2015). The transmittance measurements described herein were performed using a Lambda 1050 spectrophotometer equipped with an integrating sphere. The Lambda 1050 was configured to scan light from 250 nm to 2500 nm in 5 nm intervals in transmission mode. A background scan was performed with no sample in the optical path before the integrating sphere, and a standard material was placed over the port of the integrating sphere. After the background scan, the film sample was placed in the optical path by covering the entrance port of the integrating sphere with the film sample. Transmittance spectra in the 250 nm to 2500 nm range were scanned using a standard detector and recorded by the software accompanying the Lambda 1050.

[0018] As used in this article, the term "minimum transmittance" refers to the lowest transmittance value within a certain wavelength range.

[0019] As used herein, the terms “reflectivity” and “reflectance” refer to the effect of an object’s surface on the reflection of light. The term “average reflectivity” refers to at least one of the following: a measure of reflectivity of uniformly unpolarized light (with respect to at least one angle of incidence) or the average of measures of reflectivity of light with two or more polarizations (e.g., s-polarization and p-polarization, with respect to at least one angle of incidence).

[0020] Reflectance can be measured using the method described in ASTM E1349-06 (2015). The reflectance measurements described herein are performed using a Lambda 1050 spectrophotometer equipped with an integrating sphere. The Lambda 1050 is configured to scan from 250 nm to 2500 nm in 5 nm intervals in reflectance mode. A background scan is performed with no sample in the optical path and a material standard covering the port of the integrating sphere. After the background scan, the material standard on the back of the integrating sphere is replaced with a film sample. A light reflectance spectral scan is performed in the 250 nm to 2500 nm range using a standard detector and recorded by the software accompanying the Lambda 1050. Solar reflectance can be reported as a weighted average over the solar wavelength range. In some embodiments, any of the values ​​listed above may be an average obtained by weighting the results over the wavelength range according to the weights of the AM1.5 standard solar spectrum.

[0021] As used herein, the “emissivity” of a material surface is the effect of its emission of energy as thermal radiation. Emissivity can be described as the ratio of the surface’s radiative exitance to the radiative exitance of a blackbody at the same temperature as the surface, and can be in the range of 0 to 1. Emissivity can be measured using an infrared imaging radiometer according to the method described in ASTM E1933-99a (2010).

[0022] As used herein, the term "absorbance" refers to the logarithm to base 10 of the ratio of incident radiant power to transmitted radiant power through the material. This ratio can be described as the radiant flux received by the material divided by the radiant flux transmitted through the material. Absorbance (A) can be calculated based on transmittance (T) according to Equation 1:

[0023] A = -log 10 T = 2 - log 10 T% (Formula 1)

[0024] As used herein, the term "absorbency" of a material surface refers to its effect in absorbing radiant energy. Absorbency can be described as the ratio of the radiant flux absorbed by the surface to the radiant flux received by the surface. As is known to those skilled in the art, emissivity is equal to the absorbency of a material surface. In other words, high absorbance means high emissivity, and low absorbance means low emissivity. Therefore, throughout this disclosure, emissivity and absorbance are used interchangeably to describe this property of a material.

[0025] Absorbance in solar regions can be measured using the method described in ASTM E903-12 (2012). The absorbance measurement described herein is performed by measuring transmittance as previously described, and then calculating absorbance using Equation 1.

[0026] As used in this article, the term "minimum absorbance" refers to the lowest absorbance value within a certain wavelength range.

[0027] The term "average absorbance" refers to the arithmetic mean of absorbance measurements of a sample over a specific wavelength range. For example, absorbance measurements within this range can be averaged over a range of 8 to 13 micrometers.

[0028] As used herein, the term "high absorbance" refers to an absorbance greater than or equal to 0.5 (in some embodiments, greater than or equal to 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or even 5).

[0029] As used herein, the term "high reflectivity" refers to a reflectivity greater than or equal to 60% (in some embodiments, greater than or equal to 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or even 99.5%). Therefore, the term "high average reflectivity" refers to an average reflectivity across a specific wavelength band greater than or equal to 60% (in some embodiments, greater than or equal to 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or even 99.5%).

[0030] As used herein, the term “thermal conductivity” refers to the rate at which heat passes through a material or the amount of heat flowing through a material per unit time (watts) when the temperature gradient is one degree (K) per unit distance (meter).

[0031] As used herein, the terms “polymer” and “polymer material” include, but are not limited to, organic homopolymers, copolymers, such as (e.g.) block, graft, random and syndiotactic copolymers, trimers, etc., and blends and modifications thereof. Furthermore, unless otherwise expressly limited, the term “polymer” should include all possible geometries of the material. These geometries include, but are not limited to, isotactic, syndiotactic, and atactic symmetries. Polymers also include synthetic and natural organic polymers (e.g., cellulosic polysaccharides and their derivatives).

[0032] As used herein, the term "fluoropolymer" refers to any polymer containing fluorine. In some embodiments, a fluoropolymer may be described as a fluoroplastic, or more specifically, a fluorothermoplastic (e.g., a fluorothermoplastic purchased under the trade name "3M DYNEONTHV" from 3M Company, St. Paul, MN, Minnesota).

[0033] Referring to the antifouling layer, the term or prefix "micro" refers to at least one dimension of a structure or shape defined in the range of 1 micrometer to 1 millimeter. For example, a microstructure may have a height or width in the range of 1 micrometer to 1 millimeter.

[0034] As used herein, the term or prefix “nano” refers to at least one (or all) dimension of a structure or shape that is less than 1 micrometer. For example, a nanostructure may have at least one (or both) of a height or width of less than 1 micrometer.

[0035] As used herein, the term “microporous” refers to an internal porosity (continuous or discontinuous) with an average pore size of 50 nanometers to 10,000 nanometers.

[0036] As used herein, the term “micro-void” refers to internal discrete voids having an average void diameter of 50 nanometers to 10,000 nanometers.

[0037] As used herein, the term "maximum diameter" refers to the longest dimension based on a straight line passing through an element of any shape.

[0038] As used in this article, the term "average slope" refers to the average slope over a specific portion of a line.

[0039] As used herein, the term "comprising" and its variations are not intended to be limiting when they appear in the Detailed Description and the claims. Such terms are to be understood as implying the inclusion of the stated steps or elements or groups of steps or elements, but not excluding any other steps or elements or groups of steps or elements. The phrase "consisting of" means including and limited to what follows the phrase "consisting of". Thus, the phrase "consisting of" indicates that the listed elements are required or mandatory, and that no other elements may be present. "Substantially consisting of" means including any elements listed following that phrase, and is limited to other elements that do not impede or contribute to the activity or function of the listed elements as defined in this disclosure. Thus, the phrase "substantially consisting of" indicates that the listed elements are required or mandatory, but other elements are optional and may or may not be present depending on whether they substantially affect the activity or function of the listed elements. Any element or combination of elements described in this specification in open language (e.g., including and its derivatives) is considered to be described in closed language (e.g., consisting of and its derivatives) and partially closed language (e.g., substantially consisting of and its derivatives).

[0040] In this application, terms such as “a,” “an,” and “the” are not intended to refer only to a single entity, but to encompass general categories, with specific examples provided for illustration. The terms “a,” “an,” “the,” and “the” are used interchangeably with the term “at least one.” The phrases “at least one of…” and “containing at least one of…” followed by a list refer to any item in the list and any combination of two or more items in the list.

[0041] As used herein, the term “or” is generally used in its usual sense, including “and / or”, unless the context clearly indicates otherwise. The term “and / or” means one or all of the listed elements, or any combination of two or more of the listed elements.

[0042] As used herein, all numerical values ​​are assumed to be modified by the term “about,” and in some embodiments preferably by the term “precisely.” As used herein, with respect to the quantity measured, the term “about” refers to a deviation in the quantity measured that is commensurate with the object of the measurement and the accuracy of the measuring equipment used, as a technician who would expect such a measurement to be performed with a certain degree of care. In this document, “at least,” “at most,” and “maximum” include any value (e.g., up to 50).

[0043] As used herein, a range of values ​​expressed by endpoints includes all values ​​within that range as well as endpoint values ​​(e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0044] The terms “in the range,” “within the range of,” and “within the range” (and similar expressions) include the end values ​​of the range.

[0045] The grouping of alternative elements or embodiments disclosed herein should not be construed as restrictive. Each member of a group may be individually referenced and protected by the claims, or in any combination with other members of the group or other elements found therein. It is anticipated that at least one member of a group may be included in or removed from the group for convenience and / or patentability reasons. In the event of any such inclusion or removal, the specification herein is deemed to contain the modified group, thereby satisfying the written description of all Markush groups used in the appended claims.

[0046] Throughout this specification, references to "an embodiment," "an embodiment," "certain embodiments," or "some embodiments," etc., mean that a specific feature, configuration, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, such phrases appearing throughout this specification do not necessarily refer to the same embodiment of the invention. Furthermore, specific features, configurations, compositions, or characteristics may be combined in any suitable manner in at least one embodiment.

[0047] The above description of the invention is not intended to describe every disclosed embodiment or every implementation of the invention. The following description illustrates exemplary embodiments in more detail. Guidance is provided throughout this application by a list of examples, which may be used in various combinations. In each case, the cited list is used only as a representative group and should not be construed as an exclusive list. Therefore, the scope of this disclosure should not be limited to the specific illustrative structures described herein, but should extend at least to the structures described by the language of the claims and their equivalents. Any element positively referenced as an alternative in this specification may be expressly included in or excluded from the claims in any combination as desired. While various theories and possible mechanisms may have been discussed herein, such discussion should in no way be used to limit the subject matter protected by the claims. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of an example of a system including solar energy absorption and radiation cooling articles according to the present disclosure.

[0049] Figure 2 It uses a parabolic shape. Figure 1 A schematic cross-sectional view of an example of the configuration of the article.

[0050] Figure 3 It uses a compound parabolic shape. Figure 1 A schematic cross-sectional view of another example of the configuration of the article.

[0051] Figure 4 It uses a planar shape. Figure 1 A schematic cross-sectional view of another example of the configuration of article 102.

[0052] Figure 5 It includes the absorption cooler subsystem. Figure 1 A schematic diagram illustrating an example of system configuration.

[0053] Figure 6 It includes the steam condenser subsystem. Figure 1 A schematic diagram of another example of the system configuration.

[0054] Figure 7 It is a description of the energy spectrum of solar energy (or sunlight) as presented in ASTM G173-03 (2012), the energy transmittance % spectrum in the atmospheric window region, and other spectra that can be compared with the ground reference spectrum. Figure 1 A graph illustrating the absorption of a high-emissivity element in a passively cooled product used in a system.

[0055] Figure 8 It includes being able to Figure 1 A schematic diagram of an example of a high emissivity element using a multilayer optical film in a system.

[0056] Figure 9 It is compatible with Figure 1 A schematic top-down illustration of an example of a system using multiple structures on its surface.

[0057] Figures 10 to 13 Is it possible to... Figure 1 A schematic diagram of various examples of surface structures used in systems.

[0058] Figure 14A , Figure 14B and Figure 14C Is it possible to... Figure 1 A schematic perspective and cross-sectional illustration of an example of an antifouling surface structure used in the system.

[0059] Figure 15 Is it possible to... Figure 1 A schematic cross-sectional illustration of another example of an anti-fouling surface used in the system.

[0060] Figure 16 Is it possible to... Figure 1 A schematic cross-sectional illustration of yet another example of an anti-fouling surface used in conjunction with the system.

[0061] Figures 17A to 17B Is it possible to... Figure 1 Schematic cross-sectional illustrations of various examples of surface structures used in the system.

[0062] Figure 18 Is it possible to... Figure 1 A schematic perspective illustration of an example of another anti-fouling surface used in the system.

[0063] Figure 19 Is it possible to... Figure 1 A schematic top-down diagram of another antifouling surface used in the system.

[0064] Figure 20 and Figure 21 Is it possible to... Figure 1 A schematic perspective illustration of another stain-resistant surface used in conjunction with the system. Detailed Implementation

[0065] This disclosure relates to articles, processes, and techniques for solar energy absorption and radiative cooling. In particular, this disclosure relates to articles for solar energy absorption and radiative cooling that provide the dual functionality of absorbing energy and cooling. These articles and systems can be described as integrated or hybrid articles in which a high-reflectivity element is used to (1) reflect solar energy to an energy absorber for solar energy conversion, and (2) a high-emissivity element is used for cooling. In some aspects, solar energy can be converted into thermal or electrical energy. In some aspects, this technology can be used with heating and cooling systems, such as heat exchangers attached to buildings. Certain types of heat exchangers may include, but are not limited to, absorption coolers and steam condensers. In some aspects, this technology can be used with power generators that may include photovoltaic cells. Articles may include a variety of macrostructures, microstructures, or even nanostructures to facilitate the specific properties described herein. As used herein, the term “article” may also be described as an apparatus or system, depending on the context of use.

[0066] A significant amount of energy can be absorbed by objects exposed to sunlight, and in many cases, substantial amounts of energy are consumed to cool such objects, such as buildings, supermarket refrigeration units, data centers, generators, and transportation vehicles (such as cars, trucks, trains, buses, ships, airplanes, etc.). Using passive radiative cooling to cool these objects heated by the sun is attractive because it provides cooling without external energy sources, thus reducing costs and providing a more sustainable cooling mechanism. The use of passive cooling reduces the total energy required to maintain a suitable temperature, which can significantly reduce operating costs and greenhouse gas emissions, especially in vehicle applications where fossil fuels can be used to provide air conditioning or cooling. Additionally, passive cooling can reduce the overall demand for water, for example, in thermoelectric generation, which would otherwise use cooling towers and spray pools to evaporate water for cooling.

[0067] This disclosure provides passive cooling products capable of providing cooling day and night. For example, the passive cooling products described herein can be used to cool the walls, roofs, etc. of buildings (e.g., supermarkets, data storage centers, etc.) or the walls, roofs, etc. of transport vehicles (e.g., semi-trailers, etc.).

[0068] Generally, surface material properties used for passive radiative cooling during the day include low emissivity in the solar wavelength range of 0.3 to 2.5 micrometers and high emissivity in the infrared wavelength range of 3 to 20 micrometers. For cooling a surface below air temperature via passive radiative cooling, the surface can have high emissivity in the infrared wavelength range of 8 to 13 micrometers, but not high emissivity in the wavelength range of 3 to 8 micrometers (or 13 to 20 micrometers). According to Kirchhoff's law of thermal radiation, high emissivity is associated with high absorbance.

[0069] In some respects, the solar energy absorption and radiation cooling articles described herein can be used as heating and cooling articles and are described as such. Articles disclosed herein may comprise one or more layers of material to provide reflection in the solar region and high absorptivity / emissivity in the atmospheric infrared region. Reflection in the solar region can be particularly effective in redirecting solar energy to an energy absorber, which may also be described as a solar energy absorber or solar energy collector. By reflecting sunlight that would otherwise be absorbed by the object, reflection in the solar region can also be particularly effective in promoting cooling during daytime exposure to sunlight. In particular, the article can be positioned to reflect solar energy away from the cooling element. Absorption in the atmospheric infrared region, by radiating or emitting infrared light, can be particularly effective in promoting cooling at night. Energy can also be radiated or emitted to some extent throughout the day. Generally, high emissivity elements can be configured to absorb a minimum of 0.4 micrometers to 2.5 micrometers of solar energy and radiate a maximum of 8 micrometers to 13 micrometers of energy (e.g., by maximizing absorbance and therefore emissivity), particularly when cooling the cooling element to temperatures below air temperature. In some implementations, when the cooling element is cooled to a temperature above or equal to the air temperature, the high emissivity element can be configured to absorb a minimum solar energy of 0.4 micrometers to 2.5 micrometers and radiate a maximum energy of 4 micrometers to 20 micrometers. The energy absorber and the cooling element can be operatively coupled to each other as part of a heat exchanger, which can also be described as a heat exchange system.

[0070] In some embodiments, the heating and cooling articles described herein may include composite cooling films exhibiting relatively broad absorption (and therefore emission). Using a cooling film exhibiting broad emission can advantageously enhance the film's ability to passively cool an entity that is typically at a temperature above (in some embodiments, significantly above) the ambient temperature of its surroundings during normal operation. Such entities may include heat dissipation units (such as a portion of a heat exchanger, condenser, or compressor, and any associated items) of, for example, cooling, refrigeration, or heat pump systems. Such heat dissipation entities may be, for example, external (or outdoor) units of residential cooling or heating, ventilation, and air conditioning (HVAC) systems or commercial or large-scale cooling or HVAC systems. In some cases, such heat dissipation entities may be external units of commercial refrigeration or freezing systems. Various examples of heat dissipation entities that also benefit from the dual functionality of heating include absorption coolers and vapor condensers. In some embodiments, various heat dissipation entities include external components of cooling units for large refrigerated shipping containers (such as truck trailers, railcars, or intermodal containers). (Such large refrigerated shipping containers, etc., may be referred to in the industry as "refrigerated ships"). In some implementations, such an entity may be a high-voltage transformer or a high-power broadcast antenna (such as used in massing elements or beamforming systems for 5G wireless communication).

[0071] The described article reflects light in the solar region of the electromagnetic spectrum toward an energy absorber and radiates light in the atmospheric infrared region of the electromagnetic spectrum toward the sky to cool coolable components. The article described herein may include or be described as a high-emissivity solar mirror or a broadband solar mirror. The mirror may have specular reflectivity or diffuse reflectivity. The opposing mirror surfaces may be additionally textured, for example, to provide drag reduction or anti-fouling properties.

[0072] In some respects, hybrid solar thermal heating and cooling products can heat one fluid while simultaneously cooling another. Broadband solar mirror films can be used to concentrate solar energy onto solar absorber tubes or other solar absorber products containing the fluid to be heated. The back of the broadband solar mirror film can be thermally coupled to another fluid tube or container, which will be radiatively cooled to the relatively cooler sky. In some respects, broadband solar mirror films are also described as or include ultraviolet (UV) solar mirrors, in which the UV spectrum is reflected.

[0073] The integrated product described herein can be connected to an energy system that uses heating to generate steam and cooling to condense it. These hybrid solar thermal heating and radiative cooling systems can also be used in climates requiring heating in winter and cooling in summer.

[0074] In some respects, the articles described herein are capable of heating one fluid while simultaneously cooling another. Broadband solar mirror films are used to concentrate solar energy onto solar absorber tubes or other solar absorber articles containing the fluid to be heated, using an external composite parabolic concentrator (XCPC) configuration. When located in the Northern Hemisphere, the solar thermal collector or solar heating panel can be oriented southward, or for the Southern Hemisphere, the solar thermal collector or solar heating panel can be oriented northward. The articles can be integrated with north-facing radiative cooling panels in the Northern Hemisphere, or south-facing radiative cooling panels for the Southern Hemisphere. Both types of panels can benefit from being tilted in opposite (or relative) directions.

[0075] In some respects, solar thermal heating panels can be replaced by photovoltaic panels or batteries with heat transfer channels on their back sides that are fluidly coupled to heat transfer channels on the back sides of passive radiative cooling panels.

[0076] While certain applications, such as buildings and vehicles, are mentioned herein, heating and cooling articles can be used in any outdoor environment to provide heating and cooling to a structure or substrate, particularly when exposed to solar energy in sunlight. Non-limiting examples of applications for passive cooling articles include absorption coolers, steam condensers, commercial building air conditioning, commercial refrigeration (e.g., supermarket refrigeration units), data center cooling, heat transfer fluid systems, generator cooling, vehicle air conditioning or refrigeration (e.g., cars, trucks, trains, buses, ships, airplanes, etc.), power transformers, or communication antennas. In particular, passive cooling articles can be applied to the generally vertical sides of refrigerated semi-truck trailers or buses, which can promote cooling. Specifically, passive cooling articles cool a fluid (which can be liquid or gas) that is then used to remove heat from a cooling system (such as refrigeration or air conditioning) via a heat exchanger. Various other applications benefiting from this disclosure will become apparent to those skilled in the art.

[0077] Referring now to the accompanying drawings, at least one feature described in this disclosure is illustrated. However, it should be understood that other features not shown in the drawings fall within the scope of this disclosure. Similar reference numerals used in the drawings refer to similar components, steps, etc. However, it should be understood that using reference characters to refer to elements in a given drawing is not intended to limit elements in another drawing to those labeled with the same reference characters. Furthermore, the use of different reference numerals to refer to elements in different drawings is not intended to indicate that elements with different reference numerals cannot be the same or similar.

[0078] Figure 1This is a schematic diagram of an exemplary application of system 100, which in some cases can also be described as a solar energy absorption and passive cooling system. System 100 may include an article 102 coupled to the surface of a substrate 103, which is shown as a fixed building. Generally, article 102 may be disposed or applied to the outer surface of substrate 103, particularly the outer surface (e.g., an outer wall or side surface) exposed to solar energy 118 from the sun. In some embodiments, article 102 may be thermally coupled to substrate 103, which may allow heat transfer therebetween. Article 102 may be suitable for outdoor environments and has, for example, a suitable operating temperature range, water resistance, dirt resistance, and ultraviolet (UV) stability.

[0079] Generally, the solar mirror element 104 defines a first primary surface 114, which is positioned and shaped to reflect solar energy 118 in the solar wavelength range to an energy absorber 108 spaced apart from the first primary surface 114. The first primary surface 114 may be defined by an article 102, opposite a second primary surface 116 positioned closer to the substrate 103. In some embodiments, the second primary surface 116 of the article 102 may be coupled to the substrate 103. For example, the second primary surface 116 of the article 102 may be bonded or adhered to the substrate 103.

[0080] Article 102 may be mechanically supported by substrate 103. In some respects, article 102 is not substantially thermally coupled to substrate 103. In particular, the coupling between article 102 and substrate 103 may be configured so as not to substantially affect the thermal operation of system 100 in absorbing solar energy or providing passive cooling.

[0081] Any suitable type of solar mirror element 104 can be used. In some aspects, the solar mirror element 104 may include a mirrored solar mirror. In other aspects, the solar mirror element 104 may include a diffused solar mirror.

[0082] The solar mirror element 104 may define a first absorbance greater than or equal to 0.5. In some aspects, the first absorbance may be greater than or equal to 0.6, 0.7, 0.8, 0.9, 0.95, or even up to 1 in the atmospheric infrared wavelength range. In some aspects, the atmospheric infrared wavelength range may include the mid-infrared region from 4 micrometers to 20 micrometers, which may facilitate cooling to or above ambient air temperature. In some aspects, the atmospheric infrared wavelength range may include or be limited to 8 micrometers to 13 micrometers, which may facilitate cooling to sub-ambient air temperature. In some aspects, the atmospheric infrared wavelength range may be defined as 4 micrometers to 20 micrometers.

[0083] Among other parameters, the amount of cooling and the amount of temperature drop may depend on the reflective and absorptive properties of article 102. In some respects, high emissivity in the atmospheric window region can facilitate cooling below ambient air temperature. The cooling effect of article 102 can be described with reference to a first temperature of ambient air near or adjacent to the substrate and a second temperature of a portion of substrate 103 near or adjacent to article 102. In some embodiments, the first temperature is at least 2.7 degrees Celsius higher than the second temperature (in some embodiments, at least 5.5 degrees Celsius, 8.3 degrees Celsius, or even at least 11.1 degrees Celsius) (e.g., at least 5 degrees Fahrenheit, 10 degrees Fahrenheit, 15 degrees Fahrenheit, or even at least 20 degrees Fahrenheit).

[0084] The solar mirror element 104 may also be defined as having a first average reflectivity greater than or equal to 80%. In some aspects, the first reflectivity may be greater than or equal to 90% in the solar wavelength range of 0.4 micrometers to 2.5 micrometers. In some aspects, the solar wavelength range may be defined as 0.3 micrometers or 0.35 micrometers to 3.5 micrometers or 3 micrometers.

[0085] Article 102 may define a first end region 110 and a second end region 112. The first end region 110 and the second end region 112 may be close to or adjacent to opposite ends of article 102. In some aspects, article 102 may be oriented such that the first end region 110 is on average closer to the solar energy 118 (e.g., facing south when located in the Northern Hemisphere) and the second end region 112 is on average farther away from the solar energy 118 (e.g., facing north when located in the Northern Hemisphere).

[0086] The first primary surface 114 defined by the solar mirror element 104 may include any suitable shape or combination of shapes to reflect at least some of the solar energy 118 to the energy absorber 108. In some aspects, the first primary surface 114 may include one or more curved shapes. The curved shape may be defined at least in cross-section, for example, to include a parabola or a compound parabola. The three-dimensional curved shape may be described as a parabola or a compound parabola, respectively. The system 100 may be described as including a parabolic concentrator or a compound parabolic concentrator geometry, respectively. In addition, the first primary surface 114 may be suitably positioned such that the energy absorber 108 is close to or at the focal point of the shape formed by the first primary surface 114.

[0087] When a curved shape is used, the solar mirror element 104 can be configured to provide a specular reflector or specular reflectivity. A curved shape can also be used when the energy absorber 108 includes a solar thermal collector; for example, a curved shape can facilitate a higher concentration of solar energy 118 reaching the energy absorber 108 compared to a planar shape (e.g., more than 10 times the concentration of solar energy). A curved shape can be used when the energy absorber 108 is designed to reach high temperature ranges (e.g., above 200 degrees Celsius).

[0088] A non-limiting example of using a polymeric solar mirror film, for example, in a parabolic shape as solar mirror element 104, is described in U.S. Patent No. 9,523,516 (Hebrink et al.), published December 20, 2016, which is incorporated herein by reference. A coolable element 106, thermally coupled to a heat exchanger, can be applied to the back side of such a polymeric solar mirror film, enabling the cooling of fluids by radiative cooling of heat transfer from the polymeric solar mirror film to cooler temperatures in the sky.

[0089] A non-limiting example of using a polymeric solar mirror film, for example, as a composite parabolic shape made of solar mirror element 104, is described in U.S. Patent No. 9,383,120 (Hebrink et al.), published August 5, 2016, which is incorporated herein by reference. The coolable element 106 is thermally coupled to a heat exchanger on the back side to enable cooling of the fluid via radiative cooling of heat transfer from the polymeric solar mirror film to the cooler temperatures of the sky.

[0090] In some aspects, the first main surface 114 may include a substantially planar shape. In some aspects, the article 102 may include more than one solar mirror element 104 and more than one coolable element 106. The multiple elements may be arranged in an alternating array, alternating between a solar mirror element 104 and a coolable element 106, and between a first end region 110 and a second end region 112.

[0091] When a planar shape is used, the solar mirror element 104 can be configured to provide a diffuse reflectance or diffuse reflectivity. A diffuse reflector that can be used with either a planar or curved shape can be used when the energy absorber 108 includes a photovoltaic cell. This diffuse reflector can promote more uniform solar flux reaching the photovoltaic cell and multiply the solar energy 118 (e.g., 2 to 3 times the solar energy concentration). A planar shape can also be used when the energy absorber 108 is designed to achieve only a lower temperature range than that achievable, for example, when using a curved shape (such as a parabola or a composite parabola).

[0092] Any suitable type of coolable element 106 can be used. In some aspects, the coolable element 106 may include a thermally conductive material, such as a metal. A non-limiting example of a metal is aluminum. The coolable element 106 may also define an internal volume, which may be part of a fluid cooling circuit. In some aspects, the coolable element 106 may be a thermally conductive material having a thermal conductivity greater than or equal to 0.1 W / mK (in some embodiments, greater than or equal to 0.5 W / mK, 1.0 W / mK, or even 5.0 W / mK).

[0093] The coolable element 106 can be thermally coupled to the second main surface 116 of the solar mirror element 104 to transfer heat energy or heat from the coolable element 106 to the solar mirror element 104 to cool the coolable element 106.

[0094] Any suitable type of energy absorber 108 can be used. In some aspects, the energy absorber 108 can be configured to generate heat in response to absorbing solar energy 118 at least within the range of solar wavelengths reflected by the solar mirror element 104. The received solar energy 118 can be used by the system 100 for a specific heating process. For example, the energy absorber 108 can define an internal volume to accommodate a fluid that can be heated using the solar energy 118. In some aspects, the energy absorber 108 can be configured to generate electrical energy in response to absorbing solar energy 118, which can be used by the system 100 to provide power for a specific process. For example, the energy absorber 108 may include one or more photovoltaic cells to convert solar energy into electrical energy.

[0095] Energy absorbers 108 absorb solar energy of specific wavelengths to heat or generate electricity. In some aspects, for example, when energy absorbers 108 are designed to generate electricity using photovoltaic cells, each energy absorber 108 can absorb solar energy with wavelengths greater than or equal to 0.35 micrometers, 0.4 micrometers, or even 0.45 micrometers. In other aspects, each energy absorber 108 can absorb solar energy with wavelengths less than or equal to 1.6 micrometers, 1.1 micrometers, 0.9 micrometers, or even 0.8 micrometers.

[0096] Article 102 reflects solar energy 118 in the solar region of the electromagnetic spectrum to cool substrate 103, which is particularly effective in daytime environments. In the absence of article 102, solar energy 118 may have already been absorbed by substrate 103 and converted into heat in other ways.

[0097] Article 102 can radiate light in the atmospheric infrared region of the electromagnetic spectrum through sky 105 into the atmosphere to cool substrate 103, which is particularly effective in nighttime environments. Article 102 allows heat to be converted into solar energy 118 (e.g., infrared light) that can partially transmit through the atmospheric infrared region through sky 105. The radiation of solar energy 118 can be a characteristic of article 102 that does not require additional energy and can be described as passive radiation, which, when thermally coupled to article 102, can cool article 102 and substrate 103. During the day, reflective properties allow article 102 to emit more energy than it absorbs. By combining radiative and reflective properties to reflect sunlight during the day, article 102 can provide more cooling than an article that only radiates energy through the atmosphere.

[0098] Figure 2 yes Figure 1 A schematic cross-sectional view of an example configuration of article 102 is shown. As shown, article 202 may include one or more of a solar mirror element 204, a coolable element 206, and an energy absorber 208, which may be used as the solar mirror element 104, the coolable element 106, and the energy absorber 108 of article 102, respectively. Article 202 may extend from a first end region 210 to a second end region 212, the first end region and the second end region corresponding to the first end region 110 and the second end region 112 of article 102, respectively. Article 202 may define a first main surface 214 and a second main surface 216, the first main surface and the second main surface corresponding to the first main surface 114 and the second main surface 116 of article 102, respectively.

[0099] The first primary surface 214 reflects solar energy 118 toward the energy absorber 208, shown as reflecting solar energy 218. The first primary surface 214 defines a parabolic shape. The article 202 may define an angle of reception. The first primary surface 214 may be positioned and shaped to guide solar energy 118 toward the energy absorber 208 within the angle of reception.

[0100] The coolable element 206 is configured to transfer heat to the solar mirror element 204. The coolable element 206 may include one or more heat diffusion elements 220 and heat transfer elements 222. The heat transfer elements 222 of the coolable element 206 may define an internal volume 224. The internal volume 224 may be configured to at least partially contain a suitable heat transfer fluid, such as water.

[0101] The energy absorber 208 may define an internal volume 226. The internal volume 226 may be configured to at least partially contain a suitable heat transfer fluid, such as water or oil.

[0102] Figure 3 yes Figure 1A schematic cross-sectional view of another example of the configuration of article 102. As shown, article 302 may include one or more of a solar mirror element 304, a coolable element 306, and an energy absorber 308, which may be used as the solar mirror element 104, the coolable element 106, and the energy absorber 108 of article 102, respectively. Article 302 may define a first main surface 314, which may correspond to a first main surface 114 of article 102. Article 302 may be combined with respect to... Figure 2 The various aspects described for article 202 are not specifically numbered or discussed with respect to article 302. In some respects, article 302 may be identical to article 202, except for the shape of the first main surface 314 defined by the solar mirror element 304. A composite parabolic shape can produce a larger solar energy reception area than a simple parabolic shape (see [link to article 202]). Figure 2 ).

[0103] The first primary surface 314 reflects solar energy 118 toward the energy absorber 308, shown as reflecting solar energy 318. The first primary surface 314 defines a composite parabolic shape. The article 302 may define an angle of reception. The first primary surface 314 may be positioned and shaped to guide solar energy 118 toward the energy absorber 308 within the angle of reception.

[0104] Figure 4 yes Figure 1 A schematic cross-sectional view of another example of the configuration of article 102 is shown. As shown, article 402 may include one or more of a solar mirror element 404, a coolable element 406, and an energy absorber 408, which may be used as the solar mirror element 104, the coolable element 106, and the energy absorber 108 of article 102, respectively. Article 402 may extend from a first end region 410 to a second end region 412, the first end region and the second end region corresponding to the first end region 110 and the second end region 112 of article 102, respectively. Article 402 may define a first main surface 414 and a second main surface 416, the first main surface and the second main surface corresponding to the first main surface 114 and the second main surface 116 of article 102.

[0105] The first main surface 414 may include various regions defined by different elements. In some aspects, the first main surface 414 may be defined by both a solar mirror element 404 and an energy absorber 408. The first main surface 414 may extend from a first end region 410 to a second end region 412. In some aspects, the solar mirror element 404 defines a first region 430 of the first main surface 414 of the article 402. In some aspects, the energy absorber 408 defines a second region 432 of the first main surface 414 of the article 402.

[0106] As shown in the figure, the first region 430 includes a planar shape visible as a linear cross-sectional profile. The second region 432 also includes a planar shape visible as a linear cross-sectional profile. In some aspects, the planar shape of one or both of the first region 430 and the second region 432 can facilitate efficient energy harvesting through the photovoltaic cells of the energy absorber 408. Additionally, as shown, more than one solar mirror element 404 and more than one energy absorber 408 are arranged in an array between the first end region 410 and the second end region 412.

[0107] The second main surface 416 may also include various regions defined by different elements. In some aspects, the solar mirror element 404 defines a first region 434 of the second main surface 416. In some aspects, the energy absorber 408 defines a second region 436 of the second main surface 416.

[0108] The solar mirror element 404 reflects solar energy 118 toward the energy absorber 408. Specifically, a first region 430 of the first main surface 414 defined by the solar mirror element 404 can reflect solar energy 118 toward a second region 432 of the first main surface 414 defined by the energy absorber 408, shown as reflected solar energy 418. The article 402 may define a receiving angle or range of receiving angles that optimizes the solar reflectivity from the first region 430 of the solar mirror element 404 to the second region 432 of the solar absorber 408 for a given latitude. The first region 430 of the first main surface 414 may be positioned and shaped to guide solar energy 118 toward the second region 432 of the energy absorber 408 within a specific receiving angle.

[0109] The first region 430 and the second region 432 may be angled toward each other to facilitate the reception of reflected solar energy 418 at the second region 432. In some aspects, a first vector 438 is conceptually defined perpendicular to at least a portion of the first region 430. A second vector 440 is conceptually defined perpendicular to at least a portion of the second region 432. An element angle 442 may be defined between the first vector 438 and the second vector 440. In some aspects, the element angle 442 may be greater than or equal to 90 degrees. In some aspects, the element angle 442 may be defined as less than or equal to 175 degrees. In some aspects, the element angle 442 may be defined as greater than or equal to 100 degrees, less than or equal to 160 degrees, or both. In some embodiments, the first vector 438 and the second vector 440 may be defined as perpendicular to the average, intermediate, or central surface orientation of the respective first region 430 or second region 432, particularly when the region is curved.

[0110] The coolable element 406 may be thermally coupled to the second main surface 416. In some aspects, the coolable element 406 is thermally coupled to a first region 434 of the second main surface 416. In some applications, the coolable element 406 may be thermally coupled only to the first region 434 to facilitate the reception of heat that may be generated by the energy absorber 408. In some aspects, the coolable element 406 is thermally coupled to a second region 436 of the second main surface 416. When the energy absorber 408 includes a photovoltaic cell, the coolable element 406 may be thermally coupled to both the first region 434 and the second region 436, which may facilitate the cooling of the photovoltaic cell.

[0111] Figure 5 yes Figure 1 A schematic diagram illustrating an example configuration of system 100. As shown, system 500 includes article 502 and absorption cooler subsystem 542. Article 502 of system 500 can use any suitable configuration of article 102 as described herein.

[0112] The coolable element 506 of article 502 may define an internal volume 524 that can be used for cooling. The internal volume 524 may be thermally coupled to the condenser of the absorption cooler subsystem 542. In particular, the internal volume 524 may be in fluid communication with a cooling fluid circuit that extends into the condenser chamber that provides cooling for the absorption cooler subsystem 542.

[0113] The energy absorber 508 of article 502 may define an internal volume 526 that can be used for heating. The internal volume 526 may be thermally coupled to a steam generator of the absorption cooler subsystem 542. Specifically, the internal volume 526 may be in fluid communication with a steam fluid circuit including a steam generation chamber that provides heating steam to the absorption cooler subsystem 542. The steam fluid circuit may extend into a condensation chamber to condense the steam in the steam fluid circuit using a cooling fluid circuit.

[0114] Any suitable type of absorption cooler subsystem 542 can be selected for use in systems 500 known to those skilled in the art that benefit from this disclosure. In one aspect, the absorption cooler subsystem 542 may use water as the refrigerant and a lithium bromide (LiBr) solution as the absorbent. The cooling process may involve stages such as evaporating the refrigerant in an evaporator, absorbing the refrigerant in an absorber by concentrating the LiBr solution, boiling the diluted LiBr solution to generate refrigerant vapor in a vapor generator, and condensing the refrigerant vapor in a condenser.

[0115] Figure 6 yes Figure 1A schematic diagram of another example configuration of system 100 is shown. As shown, system 600 includes article 602 and steam condenser subsystem 642. Article 602 of system 600 can use any suitable configuration of article 102 described herein.

[0116] The coolable element 606 of article 602 may define an internal volume 624 that can be used for cooling. The internal volume 624 may be thermally coupled to the condenser of the steam condenser subsystem 642. In particular, the internal volume 624 may be in fluid communication with a cooling fluid circuit that extends into the condensing chamber that provides cooling for the steam condenser subsystem 642.

[0117] The energy absorber 608 of article 602 may define an internal volume 626 that can be used for heating. The internal volume 626 may be thermally coupled to a steam generator of the steam condenser subsystem 642. Specifically, the internal volume 626 may be in fluid communication with a steam-power fluid loop that includes steam-powered components (such as a steam turbine) that provide steam energy to the steam condenser subsystem 642. The steam-power fluid loop may extend into a condensation chamber to condense the steam in the steam-power fluid loop using a cooling fluid loop.

[0118] Any suitable type of steam condenser subsystem 642 can be selected for use in systems 600 known to those skilled in the art that benefit from this disclosure. In one aspect, the steam condenser subsystem 642 can be a water-cooled shell and tube heat exchanger used to condense exhaust steam from a steam turbine in a thermal power station. A condenser is a heat exchanger that converts steam from its gaseous state to a liquid state at a pressure below atmospheric pressure. Creating a low back pressure or vacuum at the turbine exhaust port improves the conversion of high-pressure steam to mechanical power.

[0119] The solar mirror element 104 may contribute at least partially or entirely to a high average reflectivity over the solar wavelength range. In some aspects, the coolable element 106 may contribute at least partially or entirely to a high average reflectivity over the solar wavelength range. In some aspects, the solar mirror element 104 may contribute at least partially or entirely to high absorbance over the atmospheric wavelength range. Multiple solar mirror elements 104 may also define a high average reflectivity, particularly in the solar region.

[0120] Generally, various suitable materials and structures can be used to form at least some (or all) of the solar mirror element 104. Non-limiting examples of materials and structures that can be used to form the solar mirror element 104 include: a dense fluoropolymer layer, a microporous (or microvoid) fluoropolymer layer, a dense polyester layer at least partially (or completely) covered by a dense fluoropolymer layer, a microporous (or microvoid) polyester layer at least partially (or completely) covered by a dense fluoropolymer layer, a microporous (or microvoid) polyester layer at least partially (or completely) covered by a microporous (or microvoid) fluoropolymer layer, a multilayer optical film with high average reflectivity defined at least partially (or completely) within the solar wavelength range, and a metal layer with high average reflectivity defined at least partially (or completely) within the solar wavelength range.

[0121] In some embodiments, at least some (or all) of the plurality of solar mirror elements 104 may include inorganic particles with high average reflectivity that are at least partially (or completely) defined in a solar region. In particular, the inorganic particles may be or include white inorganic particles.

[0122] This paper further describes various types of inorganic particles, fluoropolymers, microporous (or microvoid) polymer layers, multilayer optical films (such as solar mirror films), and metallic layers. In particular, Figure 8 At least one example of a multilayer optical film is shown in the figure.

[0123] Various suitable materials and structures can be used to at least partially (or completely) define the high absorbance of multiple solar mirror elements 104 in the atmospheric infrared region. Non-limiting examples of materials and structures that can be used to at least partially (or completely) define high absorbance in the atmospheric infrared region include: a dense fluoropolymer layer, a microporous (or microvoid) fluoropolymer layer, a dense polyester layer at least partially (or completely) covered by a dense fluoropolymer layer, a microporous (or microvoid) polyester layer at least partially (or completely) covered by a dense fluoropolymer layer, a microporous (or microvoid) polyester layer at least partially (or completely) covered by a microporous (or microvoid) fluoropolymer layer, and multilayer optical films.

[0124] In some embodiments, at least some (or all) of the solar mirror elements 104 may include various structures that can contribute to high absorbance in the atmospheric infrared region. In some embodiments, inorganic particles may be provided as a surface or embedded structure on or within the material of the plurality of solar mirror elements 104, such as embedded in any polymer layer (such as a dense polymer layer, a microporous (or microvoid) polymer layer, or a multilayer optical film) to contribute to high absorbance in the atmospheric infrared region. In some embodiments, the inorganic particles may be or include white inorganic particles that can at least partially (or completely) define a high average reflectance in the solar region. Any suitable white inorganic particles known to those skilled in the art that benefit from this disclosure may be used.

[0125] Inorganic particles may include barium sulfate, calcium carbonate, silica, alumina, aluminum silicate, zirconium oxide, zinc oxide, or titanium dioxide. The inorganic particles may be in the form of nanoparticles, such as nano-titanium dioxide, nano-silica, nano-zirconia, or even nano-sized zinc oxide particles. The inorganic particles may be in the form of beads or microspheres. The inorganic particles may be formed from ceramic materials, glass (such as in the form of glass beads or glass bubbles), or various combinations thereof. In some embodiments, the inorganic particles have an effective density greater than or equal to 0.1 micrometers (in some embodiments, at least 1 micrometer, 2 micrometers, 3 micrometers, 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, or even at least 13 micrometers). 90 Particle size. In some embodiments, the inorganic particles have an effective density of less than or equal to 50 micrometers (in some embodiments, less than or equal to 45 micrometers, 40 micrometers, 35 micrometers, 30 micrometers, 25 micrometers, 20 micrometers, 15 micrometers, 14 micrometers, 13 micrometers, 12 micrometers, 11 micrometers, 10 micrometers, 9 micrometers, or even up to 8 micrometers). 90 granularity.

[0126] As defined in NIST's "Particle Size Characterization," ASTM E-2578-07 (2012) defines D... 90 This is described as 90% of the sample mass having an intercept of particles with a diameter smaller than this value. For example, a D of 10 micrometers. 90 The sample mass must include particles with a diameter of less than 10 micrometers. Particle size can be measured using a particle size analyzer (e.g., the "HORIBA PARTICLE SIZE ANALYZER" available from FlowSciences, Inc., Leland, NC, North Carolina).

[0127] Non-limiting examples of ceramic microspheres that can be used as inorganic particulate ceramic microspheres include the trade name "3M CERAMIC MICROSPHERES WHITE GRADE W-710" (alkali aluminosilicate ceramic, effective D...). 90 (Particle size of 12 micrometers), "3MCERAMIC MICROSPHERES WHITE GRADE W-1410" (alkali aluminosilicate ceramic, effective D 90 (Particle size of 21 micrometers), "3M CERAMIC MICROSPHERES WHITE GRADE W-610" (alkali aluminosilicate ceramic, effective D 90 The particles (32 micrometers in size) are purchased from 3M Company, or various combinations thereof. Generally, various combinations of inorganic particles of the same or different sizes can be used.

[0128] Various suitable materials and structures can be used to at least partially (or completely) define the high average reflectivity of multiple solar mirror elements 104 in a solar region. Non-limiting examples of materials and structures that can be used to at least partially (or completely) define the high average reflectivity in a solar region include: a metallic layer that at least partially (or completely) defines the high average reflectivity over a solar wavelength range, a microporous (or microvoid) polymer layer, and a multilayer optical film. In some embodiments, one or more structures also include white inorganic particles, such as any polymer layer or multilayer optical film, which at least partially (or completely) define the high average reflectivity in a solar region.

[0129] The first primary surface 114 includes a textured surface. Some textures (e.g., depending on the dimensions of various surface structures relative to the wavelength of electromagnetic radiation) can enhance the passive cooling effect achieved by the article 102 as a whole. While one purpose of texturing the first primary surface 114 to include surface structures may be to provide radiative cooling, texturing can also provide additional benefits such as resistance or stain resistance. Various types of surface structures can include surface microstructures or surface nanostructures, which can be discrete or continuous.

[0130] In some embodiments, at least some of the solar mirror elements 104 may define various drag-resistant surface structures to provide drag reduction. In some embodiments, the article 102 may be applied to the surface of a vehicle. For example, texturing can reduce drag as the vehicle moves through the air. The presence of surface microstructures or nanostructures can lead to a reduction in the coefficient of friction between the surface and the air through which the vehicle moves, which can result in cost or fuel savings. Any suitable shape can be used to form the drag-resistant surface structure, for example, similar to Figures 3 to 13 and Figures 19 to 21 The shape shown.

[0131] In some embodiments, at least some of the solar mirror elements 104 may define various anti-fouling surface structures that may contribute to dirt and stain resistance. In some embodiments, the anti-fouling surface structures may be defined in or on at least some of the first main surfaces 114 to contribute to dirt and stain resistance. Figures 14A to 21 The image shows a non-limiting example of a stain-resistant surface structure with dirt-resistant and anti-fouling properties.

[0132] Any suitable fluoropolymer material may be used in article 102. Non-limiting examples of usable fluoropolymers include: polymers of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (e.g., available from 3M under the trade name "3MDYNEON THV"); polymers of TFE, HFP, vinylidene fluoride, and perfluoropropyl vinyl ether (PPVE) (e.g., available from 3M under the trade name "3M DYNEON THVP"); polyvinylidene fluoride (PVDF) (e.g., "3M DYNEON PVDF 6008" from 3M); ethylene-chlorotrifluoroethylene (ECTFE) polymers (e.g., available from Solvay, Brussels, Belgium under the trade name "HALAR 350LCECTFE"); and ethylene-tetrafluoroethylene (ETFE) (e.g., available from 3M DYNEON under the trade name "3M DYNEON THV"). ETFE6235 (purchased from 3M); perfluoroalkoxyalkane (PFA) polymers; fluorinated ethylene propylene (FEP) polymers; polytetrafluoroethylene (PTFE); polymers of TFE, HFP, and ethylene (e.g., purchased from 3M under the trade name "3M DYNEON HTE1705"); or various combinations thereof. Generally, various combinations of fluoropolymers may be used. In some embodiments, the fluoropolymer includes FEP. In some embodiments, the fluoropolymer includes PFA.

[0133] Examples of fluoropolymers include those purchased from companies such as 3M Company under the following trade names: “3M DYNEON THV221GZ” (39 mol% tetrafluoroethylene, 11 mol% hexafluoropropylene, and 50 mol% vinylidene fluoride), “3M DYNEON THV2030GZ” (46.5 mol% tetrafluoroethylene, 16.5 mol% hexafluoropropylene, 35.5 mol% vinylidene fluoride, and 1.5 mol% perfluoropropyl vinyl ether), “3M DYNEON THV610GZ” (61 mol% tetrafluoroethylene, 10.5 mol% hexafluoropropylene, and 28.5 mol% vinylidene fluoride), and “3M DYNEON THV815GZ” (72.5 mol% tetrafluoroethylene, 7 mol% hexafluoropropylene, 19 mol% vinylidene fluoride, and 1.5 mol% perfluoropropyl vinyl ether). Examples of fluoropolymers also include, for example, PVDF purchased from 3M Company under the trade names “3M DYNEON PVDF6008” and “3M DYNEON PVDF 11010”; FEP purchased from 3M Company under the trade name “3MDYNEON FLUOROPLASTIC FEP 6303Z”; and ECTFE purchased from Solvay Group under the trade name “HALAR 350LC ECTFE”.

[0134] Any suitable microporous (or microvoid) polymer layer (or film) can be used. Generally, a microporous layer may comprise a network of interconnected or discrete voids, which may be spherical, oval, or some other shape. A microporous layer can reflect at least a portion of the visible and infrared radiation of the solar spectrum and can emit thermal radiation in the atmospheric infrared region, and can be described as a reflective microporous layer. A reflective microporous layer may have voids of an appropriate size that diffusely reflects wavelengths in the solar region (e.g., 0.4 micrometers to 2.5 micrometers). Generally, this means that the void size should be within a specific size range (e.g., 100 nanometers to 10,000 nanometers). A range of void sizes corresponding to these dimensions facilitates effective broadband reflection.

[0135] The reflectivity of a reflective microporous layer typically depends on the number of polymer film-void interfaces, as reflection (usually diffuse reflection) occurs at those locations. The porosity and thickness of the reflective microporous layer can be selected accordingly. Generally, higher porosity and greater thickness are associated with higher reflectivity. In some applications, the film thickness can be minimal to reduce cost. The thickness of reflective microporous layers can range from 10 micrometers to 500 micrometers (or from 10 micrometers to 1200 micrometers). Similarly, the porosity of reflective microporous layers can range from 10 vol% to 90 vol% (or from 20 vol% to 85 vol%).

[0136] Microporous polymer membranes suitable for use as reflective microporous layers are described in, for example, U.S. Patent No. 8,962,214 (Smith et al.) entitled “Microporous PVDF Films”, U.S. Patent No. 10,240,013 (Mrozinski et al.) entitled “Microporous Material from Ethylene-Chlorotrifluoroethylene Copolymer and Method for Making Same”, and U.S. Patent No. 4,874,567 (Lopatin et al.) entitled “Microporous Membranes from Polypropylene”, which are incorporated herein by reference. These membranes may have an average pore size of at least 0.05 micrometers.

[0137] In some embodiments, the reflective microporous layer comprises at least one thermally induced phase separation (TIPS) material. Due to the ability to selectively stretch the layer, the pore size of the TIPS material can typically be controlled. Various materials and methods for preparing TIPS materials are described in detail in U.S. Patent Nos. 4,726,989 (Mrozinski), 5,238,623 (Mrozinski), 5,993,954 (Radovanovic et al.), and 6,632,850 (Hughes et al.).

[0138] Suitable reflective microporous layers may also include solvent-induced phase separation (SIPS) materials (such as those described in U.S. Patent No. 4,976,859 (Wechs)) and other reflective microporous layers prepared by extrusion, extrusion-stretching, and extrusion-stretch-extraction processes. Suitable reflective microporous layers that can be formed from SIPS may include polyvinylidene fluoride (PVDF), polyethersulfone (PES), polysulfone (PS), polyacrylonitrile (PAN), nylon (i.e., polyamide), cellulose acetate, cellulose nitrate, regenerated cellulose, or polyimide. Suitable reflective microporous layers that can be formed by stretching techniques (such as those described in U.S. Patent No. 6,368,742 (Fisher et al.) may include polytetrafluoroethylene (PTFE) or polypropylene.

[0139] In some embodiments, the reflective microporous layer comprises a thermoplastic polymer, such as polyethylene, polypropylene, 1-octene, styrene, polyolefin copolymer, polyamide, poly-1-butene, poly-4-methyl-1-pentene, polyethersulfone, ethylene tetrafluoroethylene, polyvinylidene fluoride, polysulfone, polyacrylonitrile, polyamide, cellulose acetate, nitrocellulose, regenerated cellulose, polyvinyl chloride, polycarbonate, polyethylene terephthalate, polyimide, polytetrafluoroethylene, ethylene trifluorochloroethylene, or combinations thereof.

[0140] In some embodiments, suitable materials for use as the reflective microporous layer may include a nonwoven fiber layer. The nonwoven fiber layer may be prepared using meltblown or melt spinning processes, and may include the use of: polyolefins such as polypropylene and polyethylene, polyesters (such as polyethylene terephthalate (PET)), polybutylene terephthalate, polyamides, polyurethanes, polybutene, polylactic acid, polyphenylene sulfide, polysulfone, liquid crystal polymers, ethylene-vinyl acetate copolymers, polyacrylonitrile, cyclic polyolefins, and copolymers and blends thereof. In some embodiments, the polymer, copolymer, or blend thereof constitutes at least 35% of the total weight of the directly formed fibers present in the nonwoven fiber layer.

[0141] Nonwoven fibers can be made from thermoplastic semi-crystalline polymers, such as semi-crystalline polyesters. Available polyesters include aliphatic polyesters. Nonwoven materials based on aliphatic polyester fibers are particularly advantageous in high-temperature applications due to their resistance to degradation or shrinkage.

[0142] Some embodiments of microporous membranes made from nonwoven fibers are high-reflectivity white paper containing polysaccharides. Microporous polysaccharide white paper with a reflectance greater than 90% for visible wavelengths from 400 nm to 700 nm is available under the trade names “IP ACCENTOPAQUE DIGITAL (100 lbs)”, “IP ACCENT OPAQUE DIGITAL (100 lbs)”, “HAMMERMILL PREMIUM COLOR COPY (80 lbs)”, and “HAMMERMILL PREMIUM COLOR COPY (100 lbs)” from International Paper, Memphis, Tennessee. Titanium dioxide, BaSO4, and other white pigments are typically added to the paper to increase its reflectivity to visible light (400 nm–700 nm).

[0143] Other nonwoven fiber layers that can be used for reflective microporous layers include those prepared using wet web-forming processes. Fibers suitable for both air-laid and wet web-forming processes include those made from natural polymers (animal or plant) and / or synthetic polymers (including thermoplastic polymers and solvent-dispersible polymers). Available polymers include wool; silk; cellulose polymers (e.g., cellulose and cellulose derivatives); fluorinated polymers (e.g., copolymers of polyvinylidene fluoride, polyvinylidene fluoride, poly(vinylidene fluoride-co-hexafluoropropylene) and trifluorochloroethylene (e.g., poly(ethylene-co-trifluorochloroethylene)); chlorinated polymers; polyolefins (e.g., copolymers of polyethylene, polypropylene, poly-1-butene, ethylene and / or propylene with 1-butene, 1-hexene, 1-octene and / or 1-decene (e.g., poly(ethylene-co-1-butene), poly(ethylene-co-1-butene-co-1-hexene)); polyisoprene; polybutadiene; polyamides (e.g., nylon 6, nylon 6, nylon...). 6, 12, poly(iminohexamethylene adipamide), poly(iminohexamethylene adipamide), or polycaprolactam; polyimide (e.g., poly(pyromellitic terephthalamide)); polyether; polyethersulfone (e.g., poly(diphenyl ether sulfone) or poly(diphenyl sulfone-co-diphenyl ether sulfone)); polysulfone; polyvinyl acetate; copolymers of vinyl acetate (e.g., poly(ethylene-co-vinyl acetate), wherein at least some of the acetate groups have been hydrolyzed to provide a variety of poly(vinyl alcohol) (including poly(ethylene-co-vinyl alcohol)); polyphosphazene; polyvinyl ester; polyvinyl ether; poly(vinyl alcohol); polyaromatic amide (e.g., poly-p-aromatic amide, such as poly(p-phenylene terephthalamide) and DuPont of Wimington, Delaware). KEVLAR fibers, marketed by Co., Wilmington, Delaware under the trade name KEVLAR, are commercially available in a variety of grades based on the fiber length from which the slurry is made, such as KEVLAR 1F306 and KEVLAR 1F694 (both containing polyaramid fibers at least 4 mm in length); polycarbonate; and combinations thereof. The nonwoven fiber layers may be calendered to adjust the pore size.

[0144] Using a reflective microporous polymer film as a reflective microporous layer can provide even greater reflectivity than a silvered mirror. In some embodiments, the reflective microporous polymer film has a high average reflectivity in solar regions. In particular, the use of fluoropolymer blends in this microporous polymer film can provide a higher average reflectivity than other types of multilayer optical films. Examples of polymers that can be used to form reflective microporous polymer films include polyesters (or polyethylene terephthalate (PET)) available from 3M. Modified PET copolyesters are also available high refractive index polymers, including PETG, such as SPECTAR 14471 and EASTAR GN071, available from Eastman Chemical Company, Kingsport, Tennessee, and PCTG, such as TIGLAZE ST and EB0062, also available from Eastman Chemical Company. Stretching can increase the molecular orientation of PET and PET-modified copolyesters, which increases the in-plane refractive index of PET and CoPET, thereby providing even higher reflectivity in multilayer optical films. Generally, prior to stretching, incompatible polymeric additives or inorganic particulate additives are blended into the PET bulk polymer during extrusion at a concentration of at least 5%, 10%, 20%, 30%, 40%, or even at least 49% by weight to nucleate voids during the stretching process. Suitable incompatible polymeric additives for PET include fluoropolymers, polypropylene, polyethylene, and other polymers that do not adhere well to PET. Crosslinked polymer beads (such as those available under the trade name "CHEMISNOW" from Soken Chemical and Engineering Co., Ltd., Japan) can be effective void nucleating agents. Glass beads (such as those available under the trade name "SPHERIGLASS" from Potters Industries LLC) can be effective nucleating agents. Similarly, if polypropylene is the main polymer, incompatible polymer additives such as PET or fluoropolymer or cross-linked polymer beads or glass beads may be added to the polypropylene main polymer during extrusion at a content of at least 10% by weight, at least 20% by weight, at least 30% by weight, at least 40% by weight, or even at least 49% by weight, prior to stretching, to nucleate voids in the stretching process.

[0145] Examples of suitable inorganic particulate additives for pore nucleation in microporous polymer films include titanium dioxide, silica, alumina, aluminum silicate, zirconium oxide, calcium carbonate, barium sulfate, and glass beads and hollow glass bulbs, but other inorganic particles and combinations thereof may also be used. Cross-linked polymer microspheres may also be used instead of inorganic particles. Before stretching, inorganic particles may be added to the host polymer during extrusion at a content of at least 10 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt%, or even at least 49 wt% to nucleate pores during stretching. If present, the inorganic particles may have a volume average particle size of 5 nanometers to 1 micrometer, but other particle sizes may also be used. Hard particles, including glass beads or glass bulbs, may be present on the surface layer of a UV reflector or antifouling layer to provide scratch resistance. In some embodiments, glass beads and / or glass bulbs may even protrude from the surface as hemispheres or even quarter-spheres.

[0146] In some embodiments, the microporous polymer membrane comprises a continuous phase of a fluoropolymer. Examples of suitable polymers include ECTFE, PVDF, and copolymers of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, such as those available, for example, from 3M under the trade name THV.

[0147] Examples of microporous PET films containing barium sulfate are available as LUMIRROR XJSA2 from Toray Plastics (America) Inc., North Kingstown, Rhode Island. LUMIRROR XJSA2 contains BaSO4 inorganic additives to increase its reflectivity in the visible light (400 nm–700 nm) range. Additional examples of reflective microporous polymer films are available as HOSTAPHAN V54B, HOSTAPHAN WDI3, and HOSTAPHAN W270 from Mitsubishi Polymer Film, Inc., Greer, South Carolina.

[0148] Some examples of microporous polyolefin membranes are described, for example, in U.S. Patent No. 6,261,994 (Bourdelais et al.).

[0149] Reflective microporous layers typically exhibit diffuse reflectivity for most wavelengths of visible light radiation in the range of, for example, 400 nm to 700 nm, including end values. In some embodiments, the reflective microporous layer may have an average reflectivity of at least 60% (in some embodiments, at least 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or even at least 99.5%) in the wavelength range of at least 400 nm to 700 nm.

[0150] The reflectivity of the microporous layer can be reflective over a wide wavelength range. In some embodiments, the reflectivity of the microporous polymer layer may have an average reflectivity of at least 60% (in some embodiments, at least 70%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or even at least 99.5%) in a wavelength range such as 0.4 micrometers to 2.5 micrometers (or even 0.3 micrometers to 3.0 micrometers) in the solar region.

[0151] Any suitable material may be used to form at least some (or all) of the coolable element 106, either partially or completely. Non-limiting examples of metals that may be used in the coolable element 106 include one or more of the following: silver (Ag), copper (Cu), aluminum (Al), gold (Au), chromium-nickel-iron alloys, stainless steel, or various combinations thereof. In some embodiments, a metal layer comprising a silver layer and a thin (20 nm thick) copper layer may be formed to protect the silver from corrosion. In some embodiments, the metal layer may at least partially (or completely) define a high average reflectivity at least within the solar wavelength range. Alternatively, any metal layer may be vapor-coated.

[0152] For example, a metal bending machine can be used to bend the metal layer (such as the heat diffuser element 220) to provide the first portion of the metal layer at an angle different from the second portion. In some embodiments, the first portion can be used to support and orient a solar mirror element 104, and the second portion can be used to support and orient the energy absorber 108 (see [link to relevant documentation]). Figure 4 ).

[0153] Any suitable technique can be used to form article 102. In some embodiments, when the heat diffusion element 220 is formed of metal, a metal bending machine can be used to bend the metal sheet (such as aluminum). A metal bending machine, commonly referred to as a brake, can be used to form the sheet metal into the desired shape factor of article 102. Metal bending machines are commercially available from companies such as Bolton Tool, Baileigh Industrial, and RAMS Sheet Metal Equipment.

[0154] In some embodiments, the polymer solar mirror element 104 can be formed by thermoforming. In some embodiments, the article 102 can be thermoformed from a thermoformable polymer sheet using a generally available polymer sheet thermoforming machine. Thermoforming machines are typically available from companies such as Belovac Industries, Sencorpwhite, and Forech Inc. In some embodiments, a laminated strip or discrete portion can be applied to the support layer prior to thermoforming or bending any element.

[0155] Figure 7 The following graphs are shown: 700: energy spectrum 702 describing the solar energy (or sunlight) of the ground reference spectrum present in ASTM G173-03 (2012); 704 (e.g., 0% to 100%) of energy transmittance in the atmospheric infrared region; and high emissivity elements of the article (such as solar mirror element 104). Figure 1 An example of absorption 706 (e.g., absorbance or emissivity, as shown by 0 to 1 on the y-axis). Absorption 706 can also be described in terms of absorbance (e.g., the logarithm of the inverse of transmittance).

[0156] A high emissivity element may define a reflector to reflect some or all of the light in the energy spectrum 702 of the reflection band 708. The reflection band 708 at least partially (or completely) covers wavelengths in the solar region, and in some cases (such as an infrared mirror film), at least partially (or completely) covers wavelengths in the visible, near-infrared, or mid-infrared regions. The reflector may have low absorption 706 in the reflection band 708.

[0157] The high emissivity element may have high absorption 706 in the absorption band 710. The absorption band 710 may at least partially (or completely) cover wavelengths in the atmospheric infrared region, which may facilitate the transmission of at least some infrared energy through the high transmittance regions of the atmosphere (e.g., from any article of this disclosure), as shown, for example, in the energy transmittance % spectrum 704. The high emissivity element may have low reflectivity in the absorption band 710.

[0158] Figure 8 This is a schematic diagram of an example of a solar mirror element 804 comprising multiple optical films, which can be used as... Figure 1 The solar mirror element 104. The solar mirror element 804 can be applied to a coolable element 806, which can be used as a... Figure 1 Coolable element 106. Solar mirror element 804 can be used to reflect solar energy 118 in the solar wavelength range. Figure 1 And it radiates light in the atmospheric infrared wavelength range. The solar mirror element 804 may include multiple components that cooperate to provide the reflective and absorptive properties described herein to direct solar energy 118 to the energy absorber 108. Figure 1 And coolable element 806. In some embodiments, solar mirror element 804 is thermally coupled to coolable element 806 to transfer heat therebetween. In some embodiments, coolable element 806 is coupled to a fluid, liquid, or gas that can transfer heat from another article or subsystem, such as a heat exchanger, building, battery, refrigerator, freezer, air conditioner, or photovoltaic module.

[0159] In some embodiments (such as the one depicted), the solar mirror element 804 may include a reflector 822 having a high average reflectivity in the solar region to reflect light in that solar region, and may have an outer layer 824 having high transmittance in the solar region to allow light to pass through and reach the reflector. The outer layer 824 may define an outer surface 850. The outer surface 850 may at least partially define a first primary surface 114 ( Figure 1 ) or at least define the first primary surface 414 ( Figure 4 The first region 430. The outer layer 824 may also have high absorbance in the atmospheric infrared region to divert energy radiation in the wavelengths of that atmospheric infrared region away from the article. In some embodiments, the outer layer 824 is thermally coupled to the reflector 822 to transfer heat therebetween. Heat transferred from the coolable element 806 to the reflector 822 may be further transferred to the outer layer 824, which may be radiated as light in the atmospheric infrared region to cool the coolable element 806 at night and during the day.

[0160] The outer layer 824 may partially or completely cover the reflector 822. Generally, the outer layer 824 may be positioned between the reflector 822 and at least one solar energy source (e.g., the sun). The outer layer 824 may be exposed to elements of the outdoor environment and may be formed of materials particularly suitable for such environments.

[0161] The outer layer 824 may be formed of a material that provides high transmittance in the solar region or high absorbance in the atmospheric infrared region, or both. The material of the outer layer 824 may include at least one polymer (e.g., a fluoropolymer).

[0162] Reflector 822 may partially or completely cover the coolable element 806. Generally, reflector 822 may be positioned between the coolable element 806 and the outer layer 824 or at least one solar energy source. The outer layer 824 can protect reflector 822 from environmental factors.

[0163] In some embodiments, the reflector 822 may be thin to facilitate heat transfer from the coolable element 806 to the outer layer 824. Generally, a thinner reflector 822 provides better heat transfer. In some embodiments, the total thickness 826 of the reflector 822 is less than or equal to 50 micrometers (in some embodiments, less than or equal to 40 micrometers, 30 micrometers, 25 micrometers, 20 micrometers, 15 micrometers, or even up to 10 micrometers).

[0164] In the illustrated embodiment, reflector 822 includes a multilayer optical film 828 and may include a metal layer 830. The metal layer 830 (described in more detail herein) may be disposed between film 828 and a coolable element 806. Film 828 may be disposed between an outer layer 824 and the coolable element 806. Film 828 may be coupled to the coolable element 806, for example, via an adhesive layer 832 (or backing layer). The adhesive layer 832 may be disposed between the metal layer 830 and the coolable element 806. The adhesive layer may include thermally conductive particles to facilitate heat transfer. These thermally conductive particles include alumina and alumina nanoparticles. Additional thermally conductive particles for the adhesive layer include those available from 3M Company under the trade name “3M BORON DINITRIDE”. Suitable thermally conductive adhesives include those available from 3M Company under the trade names “3M Thermally Conductive Adhesive Transfer Tape 8805” and “3M Thermally Conductive Epoxy Adhesive TC-2707”. In some implementations, the thermally conductive adhesive can be replaced by thermally conductive paste (such as those available under the trade name "MSC-10" from Amec Thermasol and those available under the trade name "107408 thermally conductive compound" from Honeywell Inc.).

[0165] Film 828 may include at least a defined reflective band 708. Figure 7 The film 828 comprises a plurality of first optical layers 834 and a plurality of second optical layers 836. The layers 834 and 836 in the film 828 may alternate or interleave and have different refractive indices. Each first optical layer 834 may be adjacent to a second optical layer 836, or vice versa. Most of the first optical layers 834 may be disposed between adjacent second optical layers 836, or vice versa (e.g., all but one layer).

[0166] The reflective strip 708 may be defined by the number, thickness and refractive index of the optical layers 834, 836 in any suitable manner known to those skilled in the art of preparing a reflective multilayer optical film having the benefits of this disclosure.

[0167] In some embodiments, film 828 has up to 1000 total optical layers 834, 836 (in some embodiments, up to 700, 600, 500, 400, 300, 250, 200, 150, or even up to 100 total optical layers).

[0168] The thickness of optical layers 834 and 836 in a membrane 828 can vary. Optical layers 834 and 836 may each define a maximum thickness 838. Some of the optical layers 834 and 836 may be thinner than the maximum thickness 838. The maximum thickness 838 of the optical layers 834 and 836 may be much smaller than the minimum thickness 840 of the outer layer 824. The outer layer 824 may also be described as a surface layer. In some embodiments, the outer layer 824 may provide structural support for the membrane 828, especially when the outer layer 824 is co-extruded with the membrane 828. In some embodiments, the minimum thickness 840 of the outer layer 824 is at least 5 times (in some embodiments, at least 10 times or even at least 15 times) the maximum thickness 838 of the optical layers 834 and 836.

[0169] The refractive indices of optical layers 834 and 836 may be different. The first optical layer 834 may be described as a low-refractive-index layer and the second optical layer 836 may be described as a high-refractive-index layer, or vice versa. In some embodiments, the first refractive index (or average refractive index) of the low-refractive-index layer is greater than or equal to 4% lower than the second refractive index (or average refractive index) of the high-refractive-index layer (in some embodiments, greater than or equal to 5%, 10%, 12.5%, 15%, 20%, or even at least 25%). In some embodiments, the first refractive index of the low-refractive-index layer may be less than or equal to 1.5 (in some embodiments, less than or equal to 1.45, 1.4, or even at most 1.35). In some embodiments, the second refractive index of the high-refractive-index layer may be greater than or equal to 1.4 (in some embodiments, greater than or equal to 1.42, 1.44, 1.46, 1.48, 1.5, 1.6, or even at least 1.7).

[0170] The membrane 828 may be formed of at least one material that provides high average reflectivity in the solar region. The material of the membrane 828 may include at least one polymer. One type of polymer material is a fluoropolymer. At least one material used to form the membrane 828 may be the same as or different from at least one material used to form the outer layer 824. In some embodiments, both the membrane 828 and the outer layer 824 may comprise a fluoropolymer. The composition of the fluoropolymer in the membrane 828 may be the same as or different from that in the outer layer 824.

[0171] In some embodiments, the first optical layer 834 is formed of a different material than the second optical layer 836. One of the first optical layer 834 and the second optical layer 836 may include a fluoropolymer. The other of the first optical layer 834 and the second optical layer 836 may include a fluoropolymer or include a non-fluorinated polymer. In some embodiments, the first optical layer comprises a fluoropolymer, and the second optical layer comprises a non-fluorinated polymer.

[0172] In some embodiments, the multilayer optical films described herein can be prepared using common processing techniques, such as those described in U.S. Patent No. 6,783,349 (Neavin et al.), which is incorporated herein by reference.

[0173] Ideal techniques for providing multilayer optical films with controlled spectra may include, for example, (1) controlling the layer thickness value of the co-extruded polymer layer using a shaft heater, as described, for example, in U.S. Patent No. 6,783,349 (Neavin et al.); (2) timely feedback of the layer thickness distribution from a layer thickness measurement tool such as an atomic force microscope (AFM), a transmission electron microscope, or a scanning electron microscope during production; (3) optical modeling to generate the desired layer thickness distribution; and (4) repeating shaft adjustment based on the difference between the measured layer distribution and the desired layer distribution.

[0174] In some implementations, the basic approach to layer thickness distribution control may involve adjusting the axial power settings based on the difference between the target layer thickness distribution and the measured layer distribution. The increase in axial power required to adjust the layer thickness value in a given feedback zone is first calibrated using the heat input (watts) per nanometer of change in the resulting thickness of the generated layer in that heater zone. For example, precise spectral control can be achieved using 24 axial zones for 275 layers. Once calibrated, the required power adjustment can be calculated for a given target and measured distribution. This process is repeated until the two distributions converge.

[0175] In one embodiment, the article of manufacture disclosed herein may include a UV-reflective multilayer optical film, which may be described as a UV-reflective multilayer optical film reflecting wavelengths in the range of 300 nm to 450 nm and a visible light-reflective multilayer optical film reflecting wavelengths in the range of 450 nm to 750 nm. The UV-reflective multilayer optical film is composed of 150 high-refractive-index layers comprising CoPMMA (e.g., purchased under the trade name "PERSPEX CP63" from Lucite International, Cordova, TN, Tennessee) and 150 low-refractive-index layers comprising a fluoropolymer (e.g., purchased under the trade name "3MDYNEON THV221" from 3M Company). The visible light-reflective multilayer optical film is composed of 150 layers comprising PET (e.g., purchased under the trade name "EASTAPAK 7452" from Eastman Chemical Company, Kingsport, Tennessee). The visible light reflective multilayer optical film is made by alternating high-refractive-index layers with 150 low-refractive-index layers, including fluoropolymers (e.g., available from 3M Company under the trade name "3M DYNEON THV221"). The surface of the visible light reflective multilayer optical film opposite to the ultraviolet light reflective multilayer optical film is coated with 100 nanometers of copper (Cu). The surface of the ultraviolet light reflective multilayer optical film opposite to the visible light reflector is a layer containing a fluoropolymer (e.g., available from 3M Company under the trade name "3M DYNEON THV815").

[0176] Non-limiting examples of non-fluorinated polymers (polymers without fluorine) that may be used include at least one of the following: polyethylene terephthalate (PET), copolymer of ethyl acrylate and methyl methacrylate (co-PMMA), polypropylene (PP), polyethylene (PE), polyethylene copolymer, polymethyl methacrylate (PMMA), acrylate copolymer, polyvinyl chloride, or various combinations thereof. Generally, various combinations of non-fluorinated polymers may be used.

[0177] Examples of isotropic optical polymers (especially isotropic optical polymers for use in low refractive index optical layers) may include homopolymers of polymethyl methacrylate (PMMA), such as those available under the trade names “CP71” and “CP80” from Ineos Acrylics, Inc., Wilmington, DE; and polyethyl methacrylate (PEMA) having a lower glass transition temperature than PMMA. Other available polymers include copolymers of PMMA (CoPMMA), such as CoPMMA derived from 75% by weight of methyl methacrylate (MMA) monomer and 25% by weight of ethyl acrylate (EA) monomer (available under the trade name "PERSPEX CP63" from Ineos Acrylics, Inc. or under the trade name "ATOGLAS 510" from Arkema, Philadelphia, PA); CoPMMA formed from MMA comonomer units and n-butyl methacrylate (nBMA) comonomer units; or blends of PMMA with poly(vinylidene fluoride) (PVDF). Additional examples of optical polymers for layer A include acrylate triblock copolymers, wherein each terminal block of at least one of the first block copolymer, the second block copolymer, or at least one other block copolymer is composed of poly(methyl methacrylate), and further wherein each intermediate block of at least one of the first block copolymer or the second block copolymer is composed of poly(butyl acrylate). In some embodiments, based on the total weight of the respective block copolymers, at least one of the first block copolymer, the second block copolymer, or at least one other block copolymer is formed of 30% to 80% by weight of terminal blocks and 20% to 70% by weight of intermediate blocks. In certain specific embodiments, based on the total weight of the respective block copolymers, at least one of the first block copolymer, the second block copolymer, or at least one other block copolymer is formed of 50% to 70% by weight of terminal blocks and 30% to 50% by weight of intermediate blocks. In any of the above embodiments, the first block copolymer may be selected to be the same as the second block copolymer. Triblock acrylate copolymers, for example, were purchased under the trade name "KURARITY LA4285" from Kuraray America, Inc. (Houston, TX).

[0178] Other suitable polymers for optical layers, particularly for low-refractive-index optical layers, may include at least one of the following: polyolefin copolymers, such as poly(ethylene-co-octene) (PE-PO) (e.g., available under the trade name "ENGAGE 8200" from Dow Elastomers, Midland, MI), poly(propylene-co-ethylene) (PPPE) (e.g., available under the trade name "Z9470" from Atofina Petrochemicals, Inc., Houston, TX), and copolymers of atactic polypropylene (aPP) and isotactic polypropylene (iPP). The multilayer optical film may also include, for example, a functionalized polyolefin, such as maleic anhydride-grafted linear low-density polyethylene (LLDPE-g-MA) (e.g., available under the trade name "BYNEL 4105" from Namur DuPont, Wilmington, Delaware), in the second layer.

[0179] Materials can be selected based on the absorbance or transmittance characteristics described herein, as well as on the refractive index. Generally speaking, the higher the refractive index between the two materials in film 828, the thinner the film can be, which is ideal for efficient heat transfer.

[0180] Examples of polymers that can be used to form high-refractive-index optical layers include polyethylene terephthalate (PET), purchased from 3M and also from Nan Ya Plastics Corporation (Wharton, TX). Copolymers of PET containing PETG and PCTG (obtained under the trade names “SPECTAR 14471” and “EASTAR GN071” from Eastman Chemical Company (Kingsport, TN)) are also available as high-refractive-index layers. The molecular orientation of PET and CoPET can be increased by stretching, which increases the in-plane refractive index of PET and CoPET, thereby providing even higher reflectivity in multilayer optical films.

[0181] UV stabilization using ultraviolet absorbers (UVA) and hindered amine light stabilizers (HAL) can intervene to prevent photo-oxidative degradation of PET, PMMA, and CoPMMA. UVA used for incorporation into the optical layers of PET, PMMA, or CoPMMA includes benzophenone, benzotriazole, and benzotriazine. Examples of UVA used for incorporation into the optical layers of PET, PMMA, or CoPMMA include those available under the trade names “TINUVIN 1577” and “TINUVIN 1600” from BASF Corporation, Florham Park, NJ. Typically, UVA is incorporated into the polymer at concentrations from 1% to 10% by weight. Examples of HAL used for incorporation into the optical layers of PET, PMMA, or CoPMMA include those available under the trade names “CHIMMASORB944” and “TINUVIN 123” from BASF Corporation. Typically, HAL is incorporated into the polymer at concentrations from 0.1% to 1.0% by weight. The optimal ratio of UVA to HAL is 10:1.

[0182] UVA and HAL can also be incorporated into the fluoropolymer surface layer or the fluoropolymer layer beneath the surface layer. Examples of UVA oligomers compatible with PVDF fluoropolymers are described in U.S. Patent No. 9,670,300 (Olson et al.) and U.S. Patent Application Publication No. 2017 / 0198129 (Olson et al.) (which are incorporated herein by reference).

[0183] Other UV-blocking additives can be included in fluoropolymer surface layers. Non-pigmented microparticles of zinc oxide and titanium dioxide can also be used as UV-blocking additives in fluoropolymer surface layers. Nanoscale particles of zinc oxide and titanium dioxide reflect or scatter ultraviolet light while being transparent to visible and near-infrared light. These UV-reflective micro-zinc oxide and titanium dioxide particles are available, for example, from Kobo Products, Inc., South Plainfield, NJ, and range in size from 10 nanometers to 100 nanometers.

[0184] Antistatic additives can also be incorporated into fluoropolymer surface layers or optical layers to reduce the unwanted attraction of dust, dirt, and debris. Ionic salt antistatic agents, available from 3M Company, can be incorporated into PVDF fluoropolymer layers to provide static dissipation. Antistatic additives for PMMA and CoPMMA are available, for example, under the trade name "STAT-RITE" from Lubrizol Engineered Polymers, Brecksville, OH, or under the trade name "PELESTAT" from Sanyo Chemical Industries, Tokyo, Japan.

[0185] In some embodiments, the outer layer 824 comprises a polymer of TFE, HFP, and vinylidene fluoride. In some embodiments, the outer layer 824 comprises at least one of the following: PE, polyethylene copolymer, PMMA, acrylate copolymer, or polyvinyl chloride.

[0186] In some embodiments, the first optical layer 834 comprises a polymer of TFE, HFP, and vinylidene fluoride, and the second optical layer 836 comprises a polyester (such as polyethylene terephthalate (PET)) or vice versa.

[0187] The solar mirror element 804 may comprise at least two different materials. The absorbance spectrum of each material alone may not provide high absorbance across the entire absorption band. However, two materials with complementary absorbance spectra (described in more detail herein) can synergistically provide high absorbance for the solar mirror element 804 across the entire absorption band. For example, the first material may have a transmission peak centered at a certain wavelength in the absorption band, which may not radiate sufficient energy in the atmospheric infrared region, but the second material may have complementary absorption peaks around the same wavelength center in that absorption band.

[0188] Transmission peaks can be described as transmittance greater than 10% or absorbance less than 1. Absorption peaks can be described as absorption of at least 1 or transmittance of at most 10%. However, other transmittance or absorbance values ​​that may be described herein can be used to define thresholds for transmission and absorption peaks. Transmission or absorption peaks may exceed the selected thresholds within a bandwidth of at least 10 nanometers (in some embodiments, at least 20, 30, 40, 50, 75, or even at least 100 nanometers).

[0189] In one example, one layer in the solar mirror element 804 (such as one layer in the outer layer 824 or the reflector 822) may include a first material having a minimum absorbance of less than 1 (transmission peak) within a third wavelength range encompassed in the second wavelength range. Different layers in the solar mirror element 804 may include a second material having a minimum absorbance of at least 1 (absorption peak) within the third wavelength range. The absorption peak of the second material absorbs light that would otherwise pass through the transmission peak of the first material. Thus, two or more materials can complementaryly absorb most of the light in the 8-13 micrometer absorption band.

[0190] Metal layer 830 may be disposed on the coolable element 806 or on the bottom of film 828. In some embodiments, metal layer 830 is coated on the coolable element 806 or below film 828. Metal layer 830 may be disposed between coolable element 806 and film 828. Metal layer 830 may be for at least a portion of reflected light from the reflective band. In some embodiments, metal layer 830 has a high average reflectivity in the solar region.

[0191] In some embodiments, the optical film 828 or the metal layer 830 may not individually provide high reflectivity across the entire reflection band. The metal layer 830 and the film 828 may have complementary reflectivity spectra and together provide high reflectivity for the solar mirror element 804 across the entire reflection band. For example, the film 828 may be highly reflective in one range of the reflection band, and the metal layer 830 may be highly reflective in another range of the reflection band where the film is not highly reflective.

[0192] In some embodiments, film 828 is highly reflective in a lower wavelength range, and metal layer 830 is highly reflective in a higher wavelength range adjacent to the lower wavelength range. In one example, film 828 is highly reflective in the range of 0.3 micrometers to 0.8 micrometers, and metal layer 830 is highly reflective in a complementary range of 0.8 micrometers to 2.5 micrometers. In other words, the high reflectivity range of metal layer 830 begins near the end of the high reflectivity range of film 828. Together, film 828 and metal layer 830 can provide high reflectivity in the range of 0.4 micrometers to 2.5 micrometers.

[0193] Alternatively, or in addition to selecting a high-absorbency material, the outer layer 824 or film 828 may include a structure, such as inorganic particles, that provides high absorbency in the atmospheric infrared region. Specifically, the dimensions of this structure may be appropriately set to increase the absorbency of the solar mirror element 804.

[0194] Figure 9 This is a schematic top-down view of an example of surface 900 of outer layer 924, which can be used as... Figure 8The outer surface 850 of the outer layer 824. Surface 900 may also define the first main surface 114. Figure 1 At least a portion of or the first main surface 414 Figure 4 At least a portion of the first region 430. The outer layer 924 defines a plurality of structures 902, which can be configured to improve absorbance or reflectivity. As shown, the plurality of structures 902 are disposed in or on the surface of at least one of these layers (such as the outer layer 924). The structures 902 may be uniformly dispersed in at least one of these layers (such as the outer layer 924). In some embodiments, the structures 902 may be disposed in or on a surface and uniformly dispersed in at least one of these layers. The arrangement of the structures 902 may be described as an array, which may be two-dimensional or three-dimensional. In some embodiments, the structures 902 may be described as microstructures or nanostructures, depending on the size of at least one dimension (such as maximum width or diameter).

[0195] Structure 902 may include inorganic particles. For example, each depicted structure 902 may correspond to one inorganic particle. The inorganic particle may be dispersed in at least one layer or disposed on at least one layer.

[0196] Structure 902 may include a surface structure. The surface structure may be disposed on a surface (such as the surface 900 of the outer layer 924 or the surface of a film (such as optical film 828)). In some embodiments, structure 902 may be integrated into or on surface 900. For example, structure 902 may be formed as a surface structure by extrusion replication or microreplication on at least one layer, as described in U.S. Provisional Application Serial No. 62 / 611,639, which is incorporated herein by reference. The surface structure may or may not be formed of the same material as the at least one layer.

[0197] Figures 10 to 13 The diagram illustrates various examples of surface structures, including surface structures 1000, 1010, 1020, and 1030 that define first widths 1002, 1012, 1022, and 1032, and second widths 1004, 1014, 1024, and 1034, respectively. These surface structures can be selected to improve absorbance or reflectance, which may define a first primary surface 114. Figure 1 At least a portion of or the first main surface 414 Figure 4At least a portion of the first region 430. First widths 1002, 1012, 1022, and 1032 can be described as outer widths, and second widths 1004, 1014, 1024, and 1034 can be described as base widths. In some embodiments, surface structures 1000, 1010, 1020, and 1030 may have an average width in the range of 0.1 micrometers to 50 micrometers (e.g., between the first and second widths), which may be advantageous for emissivity or absorptivity in the atmospheric infrared region. Surface structures 1010, 1020, 1030, and 1040 may include sidewalls 1006, 1016, 1026, and 1036, respectively, which define the corresponding first widths 1002, 1012, 1022, and 1032 and second widths 1004, 1014, 1024, and 1034.

[0198] Sidewalls 1006, 1016, 1026, and 1036 can be formed in various geometries. Some geometries are particularly suitable for certain manufacturing processes. The geometry can be defined by a cross-section extending between each first width 1002, 1012, 1022, and 1032 and each second width 1004, 1014, 1024, and 1034. Surface structures 1000, 1010, and 1020 can be described as conical or having a tapered shape. As used herein, the term "width" can refer to, for example, the diameter of each structure when the cross-section of structure 1000, 1020, and 1020 is circular, elliptical, or tapered. Figure 10 In the middle, the cross-section of the sidewall 1006 may include at least one straight line between widths 1002 and 1004. The first width 1002 may be smaller than the second width 1004 to define the slope. Figures 11 to 12 In this configuration, the cross-sections of the sidewalls 1016 and 1026 may include at least one curve or arc between corresponding first widths 1012 and 1022 and second widths 1014 and 1024. Figure 11 In the first width 1012, which is not zero, a tapered cylindrical shape is given to the surface structure 1010. Figure 12 In this configuration, the first width 1022 is equal to zero to give the surface structure 1020 a hemispherical or semi-dome shape. In some embodiments, the surface structure 1020 may be a sphere, or even an ellipsoid. For example, in... Figure 13 As can be seen, surface structure 1030 can be described as a square or rectangular column. The cross-section of the sidewall 1036 of surface structure 1030 can include a straight line between a first width 1032 and a second width 1034, as shown in the figure. In other aspects, sidewall 1036 can include at least one curve or arc between the widths. Sidewall 1036 can define a slope, wherein the first width 1032 is less than the second width 1034 (as shown in the figure), or the sidewall can even be vertical, wherein the first width and the second width are equal.

[0199] Each surface structure 1010, 1020, 1030, and 1040 may project from the surface orthogonally to the height of the surface extension. The width of each surface structure 1010, 1020, 1030, and 1040 may be defined to be orthogonal to the height and parallel to the surface. In some embodiments, each surface structure 1010, 1020, 1030, and 1040 has an average width greater than or equal to 0.1 micrometers (in some embodiments, greater than or equal to 1 micrometer, 3 micrometers, 5 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, or even at least 10 micrometers). In some embodiments, each surface structure 1010, 1020, 1030, and 1040 has an average width less than or equal to 50 micrometers (in some embodiments, less than or equal to 45 micrometers, 40 micrometers, 35 micrometers, 30 micrometers, 25 micrometers, 20 micrometers, 15 micrometers, 14 micrometers, 13 micrometers, 12 micrometers, 11 micrometers, 10 micrometers, 9 micrometers, or even up to 8 micrometers). In some embodiments, each surface structure 1010, 1020, 1030, and 1040 has an average height of at least 0.5 micrometers (in some embodiments, at least 1 micrometer, 3 micrometers, 5 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, or even at least 10 micrometers). In some embodiments, each surface structure 1010, 1020, 1030, and 1040 has an average height of up to 50 micrometers (in some embodiments, up to 20 micrometers, 15 micrometers, 14 micrometers, 13 micrometers, 12 micrometers, 11 micrometers, 10 micrometers, 9 micrometers, or even up to 8 micrometers).

[0200] Figures 14A to 21 Various embodiments related to dirt-resistant and stain-resistant surfaces are shown, which may define a first main surface 114 ( Figure 1 At least a portion of or the first main surface 414 Figure 4 At least a portion of the first region 430 of the element. In some embodiments, the outward-facing surface of the element (particularly a high-emissivity element) may define an anti-fouling layer. The anti-fouling layer may be defined, for example, by the entirety of the element or by a separate outer layer. The anti-fouling surface of the anti-fouling layer may be positioned opposite the reflector. The anti-fouling layer may be textured to be microstructured or nanostructured on some or all of its surface; for example, as described in U.S. Provisional Patent Application No. 62 / 611,636 and the resulting PCT International Application Publication No. WO 2019 / 130198, which are incorporated herein by reference. The use of such microstructured or nanostructured materials for the specific purpose of enhancing the anti-fouling properties of a cooling film is discussed in U.S. Provisional Patent Application No. 62 / 855,392, the entire contents of which are incorporated herein by reference.

[0201] In some embodiments, nanostructures can be superimposed on microstructures on the surface of the antifouling layer. In some such embodiments, the antifouling layer has an outer host surface (which may be described as an antifouling surface) comprising microstructures or nanostructures. The microstructures can be arranged as a series of alternating micropeaks and microspaces. The size and shape of the microspaces between the micropeaks can mitigate the adhesion of dirt particles to the micropeaks. The nanostructures can be arranged as at least a series of nanopeaks disposed on at least the microspaces. Micropeaks may be more resistant to environmental effects than nanopeaks. Since the micropeaks are separated only by microspaces, and the microspaces are significantly higher than the nanopeaks, the micropeaks can be used to protect the nanopeaks on the surface of the microspaces from abrasion.

[0202] Figure 14A , Figure 14B and Figure 14C These are schematic perspective and cross-sectional views illustrating an example of an antifouling surface structure. In the illustrated embodiment, an antifouling layer 1108 defining an antifouling surface 1104 may be coupled to a solar mirror element 1140, which can be used as... Figure 1 The solar mirror element 104. The solar mirror element 1140 can be coupled to a coolable element 1142, which can be used as a... Figure 1 The coolable element 106. In some respects, the anti-fouling layer 1108 may be described as part of the solar mirror element 104.

[0203] As shown in the figure, the cross sections 1100 and 1102 of the antifouling surface structure are shown as an antifouling layer 1108 having an antifouling surface 1104 defined by a series of microstructures 1118. In particular, Figure 14A A perspective view of cross section 1100 relative to the xyz axis is shown. Figure 14B The cross section 1102 is shown in the yz plane, which is orthogonal to the cross section 1102 and the axis 1110. Figure 14C The cross section 1100 in the xz plane parallel to the axis 1110 is shown. Figures 14A to 14C The image depicts an antifouling surface 1104, as if the antifouling layer 1108 were located on a flat, horizontal surface. However, the antifouling layer 1108 can be flexible and conformable to uneven substrates.

[0204] In some embodiments, microstructure 1118 is formed within the antifouling layer 1108. The microstructure 1118 and the remainder of the antifouling layer 1108 beneath it may be formed of the same material. The antifouling layer 1108 may be formed of any suitable material capable of defining the microstructure 1118, which may at least partially define the antifouling surface 1104. The antifouling layer 1108 may be transparent to light of various frequencies. In at least one embodiment, the antifouling layer 1108 may be opaque or even non-transparent to light of various frequencies. In some embodiments, the antifouling layer 1108 may comprise or be made of a UV-stabilizing material, and / or may comprise UV-blocking additives. In some embodiments, the antifouling layer 1108 may comprise a polymeric material, such as a fluoropolymer or a polyolefin polymer.

[0205] The antifouling surface 1104 may extend along axis 1110, for example, parallel to or substantially parallel to the axis. Plane 1112 may include axis 1110, for example, parallel to or intersecting it, such that axis 1110 lies within plane 1112. Both axis 1110 and plane 1112 may be hypothetical configurations used herein to illustrate various features associated with the antifouling surface 1104. For example, the intersection of plane 1112 and antifouling surface 1104 may define features described as follows: Figure 14C The line 1114 shows a cross-sectional profile of the surface, which includes micro-peaks 1120 and micro-spaces 1122 as described in more detail herein. The line 1114 may include at least one straight or curved segment.

[0206] Line 1114 may at least partially define a series of microstructures 1118, which may be three-dimensional (3D) structures disposed on the antifouling layer 1108, and line 1114 may describe only two dimensions of the 3D structure (e.g., height and width). Figure 14B As can be seen, the microstructure 1118 may have a length extending along the antifouling surface 1104 from one side 1130 to the other side 1132.

[0207] Microstructure 1118 may include a series of alternating micropeaks 1120 and microspaces 1122 along or in the direction of an axis 1110, which may be defined by or included in a line 1114. The direction of axis 1110 may coincide with the width dimension. Microspaces 1122 may each be disposed between a pair of micropeaks 1120. In other words, multiple micropeaks 1120 may be separated from each other by at least one microspace 1122. In at least one embodiment, at least one pair of micropeaks 1120 may not include the microspace 1122 therebetween. The pattern of alternating micropeaks 1120 and microspaces 1122 may be described as a “skipped serration” (STR). Each of the micropeaks 1120 and microspaces 1122 may include at least one straight segment or a curved segment.

[0208] The slope of line 1114 (e.g., increasing with extension) can be defined as the x-coordinate (extension) relative to the direction of axis 1110 and as the y-axis (ascent) relative to the direction of plane 1112.

[0209] The maximum absolute slope can be defined for at least a portion of line 1114. As used herein, the term "maximum absolute slope" refers to the maximum value selected from the absolute values ​​of the slopes throughout a specific portion of line 1114. For example, the maximum absolute slope of a microspace 1122 could refer to the maximum value selected from the absolute values ​​of the slopes calculated at each point along line 1114 that defines the microspace.

[0210] A line defining the maximum absolute slope of each microspace 1122 can be used to define an angle relative to axis 1110. In some embodiments, the angle corresponding to the maximum absolute slope may be up to 30 degrees (in some embodiments, up to 25 degrees, 20 degrees, 15 degrees, 10 degrees, 5 degrees, or even up to 1 degree). In some embodiments, the maximum absolute slope of at least some (in some embodiments, all) of the micropeaks 1120 may be greater than the maximum absolute slope of at least some (in some embodiments, all) of the microspaces 1122.

[0211] In some embodiments, line 1114 may define a boundary between each adjacent micro-peak 1120 and micro-space 1122. The boundary may include at least one of a straight segment or a curved segment. The boundary may be a point along line 1114. In some embodiments, the boundary may include a bend. A bend may include the intersection of two segments of line 1114. A bend may include a point where line 1114 changes direction in position (e.g., a change in slope between two different straight lines). A bend may also include a point where line 1114 has the most abrupt change in direction in position (e.g., a sharper turn compared to an adjacent curved segment). In some embodiments, the boundary may include an inflection point. An inflection point may be a point on a line where the direction of curvature changes.

[0212] Figure 15This is a schematic cross-sectional view of an example of an antifouling surface 1202. The antifouling surface 1202 may be similar to the antifouling surface 1104; for example, the microstructures 1118, 1218 of the antifouling layers 1108, 1208 may have the same or similar dimensions and may also form a skipped, toothed ribbed pattern of alternating micropeaks 1120, 1220 and microspaces 1122, 1222. In the illustrated embodiment, the antifouling surface 1202 differs from the antifouling surface 1104; for example, the antifouling surface 1202 includes nanostructures 1330, 1332 visible in both magnified covers. At least one micropeak 1220 may include at least one first microsegment 1224 or at least one second microsegment 1226. Microsegments 1224, 1226 may be disposed on opposite sides of the apex 1248 of the micropeak 1220. The apex 1248 may be, for example, the highest point or local maximum of line 1214. Each micro-segment 1224, 1226 may include at least one: a straight segment or a curved segment.

[0213] The line 1214 defining the first micro-segment 1224 and the second micro-segment 1226 may have a first average slope and a second average slope, respectively. The slope may be defined relative to the baseline 1250 as the x-axis (extension), with the orthogonal direction being the z-axis (ascent).

[0214] In some embodiments, the average slope of the first micro-segment 1224 may refer to the slope between the endpoints of the first micro-segment. In some embodiments, the average slope of the first micro-segment 1224 may refer to the average value calculated based on the slopes measured at multiple points along the first micro-segment.

[0215] Generally, the first average slope of a micro-peak can be defined as positive, and the second average slope of a micro-peak can be defined as negative. In other words, the first and second average slopes have opposite signs. In some embodiments, the absolute value of the first average slope of a micro-peak may be equal to the absolute value of the second average slope of the micro-peak. In some embodiments, the absolute values ​​may be different. In some embodiments, the absolute value of each average slope of micro-segments 1224 and 1226 may be greater than the absolute value of the average slope of micro-space 1222.

[0216] The angle A of micro-peak 1220 can be defined between the first average slope and the second average slope of the micro-peak. In other words, the first average slope and the second average slope can be calculated, and then the angle between these calculated lines can be determined. For illustrative purposes, angle A is shown in relation to the first micro-segment 1224 and the second micro-segment 1226. However, in some embodiments, when the first micro-segment and the second micro-segment are not straight lines, angle A may not necessarily be equal to the angle between the two micro-segments 1224, 1226.

[0217] Angle A can be within a range that provides sufficient antifouling properties for surface 1202. In some embodiments, angle A can be up to 120 degrees (in some embodiments, up to 110 degrees, 100 degrees, 95 degrees, 90 degrees, 85 degrees, 80 degrees, 75 degrees, 70 degrees, 65 degrees, 60 degrees, 55 degrees, 50 degrees, 45 degrees, 40 degrees, 35 degrees, 30 degrees, 25 degrees, 20 degrees, or even up to 10 degrees). In some embodiments, angle A is up to 85 degrees (in some embodiments, up to 75 degrees). In some embodiments, angle A is at least 30 degrees at the lower end (in some embodiments, at least 25 degrees, 40 degrees, 45 degrees, or even at least 50 degrees). In some embodiments, angle A is up to 75 degrees at the upper end (in some embodiments, up to 60 degrees, or even up to 55 degrees).

[0218] Micropeak 1220 can be any suitable shape that provides angle A based on the average slope of microsegments 1224, 1226. In some embodiments, micropeak 1220 is typically formed in a triangular shape. In some embodiments, micropeak 1220 is not triangular. The shape may be symmetrical across the z-axis intersecting vertex 1248. In some embodiments, the shape may be asymmetrical.

[0219] Each micropeak 1220 can be defined with a micropeak width 1244. The micropeak width 1244 can be defined by the distance between the boundaries 1216 of the corresponding micropeak 1220.

[0220] Each microspace 1222 can define a microspace width 1242. The microspace width 1242 can be defined as the distance between corresponding boundaries 1216, which can be between adjacent micropeaks 1220.

[0221] The minimum value of the microspace width 1242 can be defined in micrometers. In some embodiments, the microspace width 1242 may be at least 10 micrometers (in some embodiments, at least 20 micrometers, 25 micrometers, 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 75 micrometers, 80 micrometers, 90 micrometers, 100 micrometers, 150 micrometers, 200 micrometers, or even at least 250 micrometers). In some applications, the microspace width 1242 is at least 50 micrometers at the lower end (in some embodiments, at least 60 micrometers or 70 micrometers). In some applications, the microspace width 1242 is at most 90 micrometers at the upper end (in some embodiments, at most 80 micrometers or 70 micrometers). In some applications, the microspace width 1242 is 70 micrometers.

[0222] As used in this article, the term "peak distance" refers to the distance between consecutive peaks or between the nearest peak pairs, measured at each apex or highest point of a peak.

[0223] The microspace width 1242 may also be defined relative to the micropeak distance 1240. Specifically, the minimum value of the microspace width 1242 may be defined relative to the corresponding micropeak distance 1240, which may refer to the distance between the nearest pair of micropeaks 1220 surrounding the microspace 1222, measured at each vertex 1248 of the micropeaks. In some embodiments, the microspace width 1242 may be at least 10% of the maximum value of the micropeak distance 1240 (in some embodiments, at least 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, or even at least 90%). In some embodiments, the minimum value of the microspace width 1242 at the lower end is at least 30% of the maximum value of the micropeak distance 1240 (in some embodiments, at least 40%). In some embodiments, the minimum value of the microspace width 1242 at the upper end is at most 60% of the maximum value of the micropeak distance 1240 (in some embodiments, at most 50%). In some implementations, the microspace width 1242 is 45% of the micropeak distance 1240.

[0224] The minimum value of the micropeak distance 1240 can be defined in micrometers. In some embodiments, the micropeak distance 1240 can be at least 1 micrometer (in some embodiments, at least 2 micrometers, 3 micrometers, 4 micrometers, 5 micrometers, 10 micrometers, 25 micrometers, 50 micrometers, 75 micrometers, 100 micrometers, 150 micrometers, 200 micrometers, 250 micrometers, or even at least 500 micrometers). In some embodiments, the micropeak distance 1240 is at least 100 micrometers.

[0225] The maximum value of the micro-peak distance 1240 can be defined in micrometers. The micro-peak distance 1240 can be up to 1000 micrometers (in some embodiments, up to 900 micrometers, 100 micrometers, 700 micrometers, 600 micrometers, 500 micrometers, 400 micrometers, 300 micrometers, 250 micrometers, 200 micrometers, 150 micrometers, 100 micrometers, or even up to 50 micrometers). In some embodiments, the micro-peak distance 1240 is up to 200 micrometers at the upper end. In some embodiments, the micro-peak distance 1240 is at least 100 micrometers at the lower end. In some embodiments, the micro-peak distance 1240 is 150 micrometers.

[0226] Each micropeak 1220 may define a micropeak height 1246. The micropeak height 1246 may be defined as the distance between the baseline 1350 and the apex 1248 of the micropeak 1220. The minimum value of the micropeak height 1246 may be defined in micrometers. In some embodiments, the micropeak height 1246 may be at least 10 micrometers (in some embodiments, at least 20 micrometers, 25 micrometers, 30 micrometers, 40 micrometers, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, 90 micrometers, 100 micrometers, 150 micrometers, 200 micrometers, or even at least 250 micrometers). In some embodiments, the micropeak height 1246 is at least 60 micrometers (in some embodiments, at least 70 micrometers). In some embodiments, the micropeak height 1246 is 80 micrometers.

[0227] Multiple nanostructures 1330, 1332 may be defined at least partially by line 1214. Multiple nanostructures 1330 may be disposed on at least one microspace 1222. Specifically, the line 1314 defining the nanostructures 1330 may include at least a series of nanopeaks 1320 disposed on at least one microspace 1222. In some embodiments, at least one series of nanopeaks 1320 of the multiple nanostructures 1332 may also be disposed on at least one micropeak 1220.

[0228] At least due to their size difference, the microstructure 1218 is more durable than the nanostructures 1330 and 1332 in terms of wear resistance. In some embodiments, the multiple nanostructures 1332 are disposed only on the microspace 1222, or at least not disposed near or adjacent to the vertex 1248 of the micropeak 1220.

[0229] Each nanopeak 1320 may include at least one of a first nanosegment 1324 and a second nanosegment 1326. Each nanopeak 1320 may include both nanosegments 1324 and 1326. Nanosegments 1324 and 1326 may be disposed on opposite sides of the apex 1348 of the nanopeak 1320.

[0230] The first nanosegment 1324 and the second nanosegment 1326 may define a first average slope and a second average slope, respectively, which describe the line 1314 defining the nanosegments. For nanostructures 1330 and 1332, the slope of the line 1314 may be defined relative to the baseline 1350 as the x-axis (extension), where the orthogonal direction is the z-axis (ascent).

[0231] Generally, the first average slope of a nanopeak can be defined as positive, and the second average slope of a nanopeak can be defined as negative, or vice versa. In other words, the first and second average slopes have at least opposite signs. In some embodiments, the absolute value of the first average slope of a nanopeak may be equal to the absolute value of the second average slope of the nanopeak (e.g., nanostructure 1330). In some embodiments, the absolute values ​​may be different (e.g., nanostructure 1332).

[0232] Angle B of nanopeak 1320 can be defined between the lines defined by the first average slope and the second average slope of the nanopeak. Similar to angle A, angle B shown in the figure is for illustrative purposes and may not necessarily be equal to any directly measured angle between nanosegments 1324 and 1326.

[0233] Angle B can be within a range that provides sufficient antifouling properties for surface 1202. In some embodiments, angle B can be up to 120 degrees (in some embodiments, up to 110 degrees, 100 degrees, 90 degrees, 85 degrees, 80 degrees, 75 degrees, 70 degrees, 65 degrees, 60 degrees, 55 degrees, 50 degrees, 45 degrees, 40 degrees, 35 degrees, 30 degrees, 25 degrees, 20 degrees, or even up to 10 degrees). In some embodiments, angle B is up to 85 degrees at the upper end (in some embodiments, up to 80 degrees, or even up to 75 degrees). In some embodiments, angle B is at least 55 degrees at the lower end (in some embodiments, at least 60 degrees, or even at least 65 degrees). In some embodiments, angle B is 70 degrees.

[0234] For each nanopeak 1320, the angle B may be the same or different. For example, in some embodiments, the angle B of the nanopeak 1320 on the micropeak 1220 may be different from the angle B of the nanopeak 1320 on the microspace 1222.

[0235] Nanopeak 1320 can be any suitable shape capable of providing angle B based on a line defined by the average slope of nanosegments 1324, 1326. In some embodiments, nanopeak 1320 is typically formed in a triangular shape. In at least one embodiment, nanopeak 1320 is not triangular. The shape can be symmetrical across vertex 1348. For example, nanopeak 1320 of nanostructure 1330 disposed on microspace 1222 can be symmetrical. In at least some embodiments, the shape can be asymmetrical. For example, nanopeak 1320 of nanostructure 1332 disposed on micropeak 1220 can be asymmetrical, where one nanosegment 1324 is longer than the other nanosegment 1326. In some embodiments, nanopeak 1320 can be formed without undercutting.

[0236] Each nanopeak 1320 may define a nanopeak height 1346. The nanopeak height 1346 may be defined as the distance between the baseline 1350 and the apex 1348 of the nanopeak 1320. The minimum value of the nanopeak height 1346 may be defined in nanometers. In some embodiments, the nanopeak height 1346 may be at least 10 nanometers (in some embodiments, at least 50 nanometers, 75 nanometers, 100 nanometers, 120 nanometers, 140 nanometers, 150 nanometers, 160 nanometers, 180 nanometers, 200 nanometers, 250 nanometers, or even at least 500 nanometers).

[0237] In some embodiments, the nanopeak height 1346 is at most 250 nanometers (in some embodiments, at most 200 nanometers), particularly for the nanostructure 1330 on the microspace 1222. In some embodiments, the nanopeak height 1346 is in the range of 100 nanometers to 250 nanometers (in some embodiments, 160 nanometers to 200 nanometers). In some embodiments, the nanopeak height 1346 is 180 nanometers.

[0238] In some embodiments, the nanopeak height 1346 is at most 160 nanometers (in some embodiments, at most 140 nanometers), particularly for the nanostructure 1332 on the micropeak 1220. In some embodiments, the nanopeak height 1346 is in the range of 75 nanometers to 160 nanometers (in some embodiments, 100 nanometers to 140 nanometers). In some embodiments, the nanopeak height 1346 is 120 nanometers.

[0239] As used herein, the term "corresponding micropeak" refers to a micropeak 1220 on which nanopeak 1320 is disposed, or, if the nanopeak is disposed on a corresponding microspace 1222, to one or both of the nearest micropeaks surrounding that microspace. In other words, micropeak 1220 corresponding to microspace 1222 refers to a micropeak among a series of micropeaks preceding and following the microspace.

[0240] The height of the nanopeak 1346 may also be defined relative to the height of the corresponding micropeak 1220. In some embodiments, the corresponding micropeak height 1246 may be at least 10 times the height of the nanopeak 1346 (in some embodiments, at least 50, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, or even at least 1000 times). In some embodiments, the corresponding micropeak height 1246 at the lower end is at least 300 times the height of the nanopeak 1346 (in some embodiments, at least 400, 500, or even at least 600 times). In some embodiments, the corresponding micropeak height 1246 at the upper end is at most 900 times the height of the nanopeak 1346 (in some embodiments, at most 800 or even at most 700 times).

[0241] The nano-peak distance 1340 can be limited to between the nano-peak distances 1320 and 1320. A maximum value for the nano-peak distance 1340 can be defined. In some embodiments, the nano-peak distance 1340 can be up to 1000 nanometers (in some embodiments, up to 750 nanometers, 700 nanometers, 600 nanometers, 500 nanometers, 400 nanometers, 300 nanometers, 250 nanometers, 200 nanometers, 150 nanometers, or even up to 100 nanometers). In some embodiments, the nano-peak distance 1340 is up to 400 nanometers (in some embodiments, up to 300 nanometers).

[0242] In some implementations, the nanopeak distance 1340 may alternatively or additionally be defined as the distance between corresponding nanopeak boundaries 1316, which may be between adjacent nanopeaks 1320.

[0243] The minimum value of the nanoparticle peak distance of 1340 can be defined. In some embodiments, the nanoparticle peak distance of 1340 can be at least 1 nanometer (in some embodiments, at least 5 nanometers, 10 nanometers, 25 nanometers, 50 nanometers, 75 nanometers, 100 nanometers, 150 nanometers, 200 nanometers, 250 nanometers, 300 nanometers, 350 nanometers, 400 nanometers, 450 nanometers, or even at least 500 nanometers). In some embodiments, the nanoparticle peak distance of 1340 is at least 150 nanometers (in some embodiments, at least 200 nanometers).

[0244] In some embodiments, the nanopeak distance 1340 is in the range of 150 nm to 400 nm (in some embodiments, 200 nm to 300 nm). In some embodiments, the nanopeak distance 1340 is 250 nm.

[0245] The nanopeak distance 1340 may be defined relative to the micropeak distance 1240 between the corresponding micropeaks 1220. In some embodiments, the corresponding micropeak distance 1240 is at least 10 times the nanopeak distance 1340 (in some embodiments, at least 50 times, 100 times, 200 times, 300 times, 400 times, 500 times, 600 times, 700 times, 800 times, 900 times, or even at least 1000 times). In some embodiments, the corresponding micropeak distance 1240 at the lower end is at least 200 times the nanopeak distance 1340 (in some embodiments, at least 300 times). In some embodiments, the corresponding micropeak distance 1240 at the upper end is at most 500 times the nanopeak distance 1340 (in some embodiments, at most 400 times).

[0246] In some embodiments of forming an antifouling surface, the method may include extruding a hot-melt material (e.g., a suitable fluoropolymer). The extruded material may be shaped using a microreplication tool. The microreplication tool may include a series of mirror images of microstructures that can form a series of microstructures on the surface of the antifouling layer. The series of microstructures may include a series of alternating micropeaks and microspaces along an axis. Multiple nanostructures may be formed on the surface of the layer, at least in the microspaces. The multiple nanopeaks may include at least one series of nanopeaks along an axis.

[0247] In some implementations, multiple nanostructures can be formed by exposing the surface to reactive ion etching. For example, masking elements can be used to define nanopeaks.

[0248] In some implementations, multiple nanostructures can be formed by shaping extruded material using a micro-replication tool that also incorporates ion-etched diamond. This method may involve providing a diamond tool, wherein at least a portion of the tool comprises a plurality of cutting tips, wherein the spacing between the cutting tips may be less than 1 micrometer; and cutting a substrate with the diamond tool, wherein the diamond tool can enter and exit along a certain direction at a spacing (p1). The diamond tool may have a maximum cutter width (p2), and

[0249] Nanostructures can be characterized as microstructured surfaces embedded within an antifouling layer. Except for the portion of the nanostructure exposed to air, its shape is typically defined by the adjacent microstructured material.

[0250] Microstructured surface layers, including nanostructures, can be formed using multi-head diamond tools. Diamond turning (DTM) machines can be used to generate micro-replicating tools that produce anti-fouling surface structures including nanostructures, as described in U.S. Patent Application Publication No. 2013 / 0236697 (Walker et al.), which is incorporated herein by reference. Microstructured surfaces, including nanostructures, can also be formed using multi-head diamond tools, which may have a single radius, wherein the multiple heads are spaced less than 1 micrometer apart. Such multi-head diamond tools may also be referred to as “nanostructured diamond tools.” Therefore, microstructured surfaces, where the microstructure also includes nanostructures, can be formed simultaneously during the fabrication of microstructured tools using diamond tools. Focused ion beam milling processes can be used to form the heads, and also to form the valleys of the diamond tool. For example, focused ion beam milling can be used to ensure that the inner surfaces of the heads converge along a common axis to form the bottom of the valley. Focused ion beam milling can be used to form features in valleys, such as recessed or raised arcuate ellipses, parabolas, mathematically defined surface patterns, or random or pseudo-random patterns. Valleys of a variety of other shapes can also be formed. Examples of diamond turning machines and methods for producing discontinuous or inconsistent surface structures may include and utilize rapid tool servo mechanisms (FTS) as described in the following patents: for example, PCT Publication No. WO 00 / 48037, published August 17, 2000; U.S. Patent Nos. 7,350,442 (Ehnes et al.) and 7,328,638 (Gardiner et al.); and U.S. Patent Publication No. 2009 / 0147361 (Gardiner et al.), which are incorporated herein by reference.

[0251] In some implementations, multiple nanostructures can be formed by shaping extruded material or antifouling layers using a micro-replicating tool that also has a nanostructured granular electroplated layer for imprinting. Electrodeposition, or more specifically electrochemical deposition, can also be used to generate various surface structures, including nanostructures, to form the micro-replicating tool. The tool can be made using a two-part electroplating process, wherein a first electroplating process forms a first metal layer having a first master surface, and a second electroplating process forms a second metal layer on the first metal layer. The second metal layer may have a second master surface with an average roughness less than that of the first master surface. The second master surface can serve as the structured surface of the tool. A replica of this surface can then be prepared in the master surface of an optical film to provide light-diffusing properties. An example of an electrochemical deposition technique is described in PCT Publication No. WO 2018 / 130926 (Derks et al.), which is incorporated herein by reference.

[0252] Figure 16 It is compatible with system 100 ( Figure 1A schematic cross-sectional view of another example of an antifouling surface used together. As shown, cross-section 1400 of the antifouling layer 1408 defines an antifouling surface 1402. The antifouling surface 1402 may be similar to the antifouling surface 1202; for example, the microstructures 1218, 1418 of the antifouling layers 1208, 1408 may have the same or similar dimensions, and may also form a skipped toothed ridge pattern of alternating micropeaks 1220, 1420 and microspaces 1222, 1422. The antifouling surface 1402 may differ from the surface 1202; for example, the nanostructure 1520 may include nanoscale masking elements 1522.

[0253] Nanostructure 1520 can be formed using masking element 1522. For example, masking element 1522 can be used in subtractive manufacturing processes, such as reactive ion etching (RIE), to form nanostructure 1520 with a surface 1402 having microstructure 1418. Methods for preparing nanostructures and nanostructured articles can involve depositing layers (such as an antifouling layer 1208) onto a host surface of a substrate by plasma chemical vapor deposition from a gaseous mixture while simultaneously etching the surface with a reactive material substantially simultaneously. This method may include providing a substrate; mixing a first gaseous material capable of depositing layers onto the substrate when a plasma is formed with a second gaseous material capable of etching the substrate when a plasma is formed, thereby forming a gaseous mixture. This method may include causing the gaseous mixture to form a plasma and exposing the surface of the substrate to the plasma, wherein the surface can be etched and layers can be deposited substantially simultaneously on at least a portion of the etched surface, thereby forming a nanostructure.

[0254] The substrate can be a (co)polymer material, inorganic material, alloy, solid solution, or a combination thereof. The deposited layer can include reaction products deposited using a plasma chemical vapor deposition process with a reactive gas, comprising compounds selected from the group consisting of organosilicon compounds, metal alkyl compounds, metal isopropoxy compounds, acetylacetone metal compounds, metal halides, and combinations thereof. High aspect ratio nanostructures can be fabricated, optionally exhibiting random dimensions in at least one dimension, or even in three orthogonal dimensions.

[0255] In some embodiments of the method for the antifouling layer 1408, an antifouling layer may be provided having a series of microstructures 1418 disposed on the antifouling surface 1402 of the layer. The series of microstructures 1418 may include a series of alternating micropeaks 1420 and microspaces 1422.

[0256] A series of nanoscale masking elements 1522 may be disposed on at least the microspace 1422. The antifouling surface 1402 of the antifouling layer 1408 may be exposed to reactive ion etching to form a plurality of nanostructures 1518 on the surface of a layer comprising a series of nanopeaks or nanostructures 1520. Each nanopeak or nanostructure 1520 may include a masking element 1522 and a pillar 1560 of the layer material between the masking element 1522 and the layer 1408.

[0257] The masking element 1522 may be formed of any suitable material that is more resistant to the RIE effect than the material of the antifouling layer 1408. In some embodiments, the masking element 1522 comprises an inorganic material. Non-limiting examples of inorganic materials include silica and silicon dioxide. In some embodiments, the masking element 1522 is hydrophilic. Non-limiting examples of hydrophilic materials include silica and silicon dioxide.

[0258] The masking element 1522 may be nanometer-sized. Each masking element 1522 may have a maximum diameter of 1542. In some embodiments, the maximum diameter of the masking element 1522 may be up to 1000 nanometers (in some embodiments, up to 750 nanometers, 500 nanometers, 400 nanometers, 300 nanometers, 250 nanometers, 200 nanometers, 150 nanometers or even up to 100 nanometers).

[0259] The maximum diameter 1542 of each masking element 1522 can be described relative to the peak height 1440 of the corresponding peak 1420. In some embodiments, the corresponding peak height 1440 is at least 10 times the maximum diameter 1542 of the masking element 1522 (in some embodiments, at least 25 times, 50 times, 100 times, 200 times, 250 times, 300 times, 400 times, 500 times, 750 times or even at least 1000 times).

[0260] Each nanopeak or nanostructure 1520 may have a defined height of 1546. The height 1546 may be defined between the baseline 1550 and the vertex 1548 of the masking element 1522.

[0261] Figures 17A to 17B These are schematic cross-sectional illustrations of various examples of surface structures. As shown, conceptual lines 1600 and 1620 represent the cross-sectional profiles of different forms of peaks 1602 and 1622 for any antifouling surface (such as antifouling surfaces 1104, 1202, 1402), which can be micro-peaks of microstructures or nano-peaks of nanostructures. As mentioned, the structure does not need to be strictly triangular in shape.

[0262] Line 1600 shows that the first portion 1604 (top portion) of peak 1602, including vertex 1612, may have a generally triangular shape, while the adjacent side portions 1606 may be curved. In some embodiments, as shown, the side portions 1606 of peak 1602 may not have a more abrupt turn when transitioning into space 1608. The boundary 1610 between the side portions 1606 of peak 1602 and space 1608 may be defined by a threshold slope of line 1600, as described herein, for example, relative to... Figures 14A to 14C and Figure 15 The subject of discussion.

[0263] Space 1608 may also be defined by its height relative to the height 1614 of peak 1602. The height 1614 of peak 1602 may be defined between one boundary of boundary 1610 and vertex 1612. The height of space 1608 may be defined between the bottom 1616 or the lowest point of space 1608 and one boundary of boundary 1610. In some embodiments, the height of space 1608 may be up to 40% of the height 1614 of peak 1602 (in some embodiments, up to 30%, 25%, 20%, 15%, 10%, 5%, 4%, 3%, or even up to 2%). In some embodiments, the height of space 1608 is up to 10% of the height 1614 of peak 1602 (in some embodiments, up to 5%, 4%, 3%, or even up to 2%).

[0264] Line 1620 shows that the first portion 1624 (top portion) of peak 1622, including the vertex, may have a generally circular shape, while there are no sharp turns between adjacent side portions 1626. Vertex 1632 can be defined as the highest point of the structure of peak 1622, for example, where the slope changes from positive to negative. Although the first portion 1624 (top portion) may be circular at vertex 1632, peak 1622 may still define an angle between a first average slope and a second average slope, such as angle A (see...). Figure 15 ).

[0265] The boundary 1630 between the side portion 1626 of peak 1622 and space 1628 may be defined, for example, by a more abrupt turn. As discussed herein, the boundary 1630 may also be defined by slope or relative height.

[0266] like Figures 18 to 21 As shown, the antifouling surface can be discontinuous, intermittent, or inconsistent. For example, the antifouling surface can also be described as comprising micropyramids having microspaces surrounding the micropyramids (see [reference]). Figure 18 and Figure 21 ).

[0267] Figure 18This is a schematic perspective view of another example of an antifouling surface. As shown, the first antifouling surface 1701 is at least partially defined by inconsistent microstructures 1710. For example, if the antifouling surface 1701 is observed in the yz plane (similar to...), Figure 14B If at least one micro-peak 1712 has an inconsistent height from left to right in the view, this can be compared with micro-peak 1120, which shows a consistent height from left to right in the view. Figure 14B This creates a contrast. Specifically, at least one of the height or shape of the micropeaks 1712 defined by the inconsistent microstructure 1710 may be inconsistent. The micropeaks 1712 are spaced apart by microspaces (not shown in this perspective view), similar to the microspaces 1122 of other surfaces described herein, such as the antifouling surface 1104. Figure 14A and Figure 14C ).

[0268] Figure 19 This is a schematic top-down view of yet another antifouling surface. As shown, the second antifouling surface 1702 has a discontinuous microstructure 1720. For example, if the second antifouling surface 1702 is observed in the yz plane (similar to...), Figure 14B Then, more than one micropeak 1722 separated by microstructure 1720 can be shown, which can be compared with the micropeak 1120 shown extending continuously from the left to the right side of the view. Figure 14B In contrast, the micropeaks 1722 of the microstructure 1720 may be surrounded by microspaces 1724. Each micropeak 1722 may have a semi-dome shape. For example, the semi-dome shape may be hemispherical, semi-oval, semi-oblong, or semi-flattened spherical. The edge 1726 of the base of each micropeak 1722 extending around each micropeak may be circular (e.g., circular, elliptical, or rounded rectangle). The shape of the micropeaks 1722 may be uniform, as depicted in the illustrated embodiment, or it may be inconsistent.

[0269] Figure 20 and Figure 21 This is a schematic perspective illustration of yet another antifouling surface. The first part 1704 of the third antifouling surface 1703 ( Figure 20 Part 2 and Part 1705 Figure 21 It has a discontinuous microstructure 1730. Figure 20 The view shows more of the "front" side of the microstructure 1730 at an angle close to 45 degrees, while Figure 21 The view shows some of the microstructures on the "back" side closer to the apex.

[0270] The micropeaks 1732 of the microstructure 1730, surrounded by microspaces 1734, may have a pyramidal shape (e.g., a micropyramid). For example, the pyramidal shape may be a rectangular pyramid or a triangular pyramid. The sides 1736 of the pyramidal shape may be inconsistent in shape or area (as depicted in the illustrated embodiment) or may be consistent in shape or area. The edges 1738 of the pyramidal shape may be non-linear (as shown in the illustrated embodiment) or may be linear. The total volume of each micropeak 1732 may be inconsistent (as depicted in the illustrated embodiment) or may be consistent.

[0271] The detailed discussion above clearly demonstrates that, if desired, the antifouling surface of the antifouling layer can be textured, for example, microstructured or nanostructured, to enhance its antifouling properties. Generally, texturing can be achieved in any suitable manner, whether by molding or imprinting the surface against a suitable tool surface, or by removing material from an existing surface, for example, through reactive ion etching, laser ablation, etc. In some methods, the antifouling layer may include inorganic particles of appropriate size and / or shape to provide the desired surface texture. In some embodiments, any such particles may, for example, be deposited onto and adhered to the surface. In other embodiments, any such particles may be incorporated (e.g., mixed) into the material to which the antifouling layer is to be formed, and then the layer is formed in a manner that allows the particles to be present in the layer, such that the antifouling surface exhibits a corresponding texture. In some embodiments, the presence of such particles may cause the surface of the antifouling layer to exhibit texture within the resulting layer. In other embodiments, such particles may cause texture formation, as previously described, for example, when organic polymer material is removed from the surface of the antifouling layer (e.g., by reactive ion etching) while the inorganic particles remain in place. In variations of this method, inorganic materials can be deposited simultaneously onto the main surface of the antifouling layer, for example, via plasma deposition and organic material removal (e.g., reactive ion etching) processes to achieve a similar effect. Such arrangements are discussed in U.S. Patent 10,134,566, which is incorporated herein by reference.

[0272] Therefore, various solar energy absorption and radiative cooling technologies are disclosed. While reference is made to a set of drawings that form part of this disclosure, it will be apparent to those skilled in the art that various adaptations and modifications of the embodiments described herein are within or do not depart from the scope of this disclosure. For example, aspects of the embodiments described herein can be combined with each other in a variety of ways. Therefore, it should be understood that the claimed invention may be practiced in ways other than those expressly described herein within the scope of the appended claims.

[0273] All patents, patent documents, and publications cited herein are incorporated herein by reference in their entirety as if each document were cited individually. In the event of any conflict or contradiction between the disclosures in this written specification and any documents incorporated herein by reference, the written specification shall prevail. Various modifications and alterations to this disclosure will become apparent to those skilled in the art without departing from its scope and spirit. It should be understood that this disclosure is not intended to be unduly limited to the exemplary embodiments and examples shown herein, and such embodiments and examples are presented by way of example only. The scope of this disclosure is intended to be limited only by the claims shown herein.

Claims

1. A passive cooling product, the passive cooling product comprising: A first element, the first element being defined as having a first absorbance greater than or equal to 0.5 in the atmospheric infrared wavelength range of 8 micrometers to 13 micrometers, and at least partially defined as having a first average reflectance greater than or equal to 80% in the solar wavelength range of 0.4 micrometers to 2.5 micrometers, the first element comprising a first primary surface, the first primary surface being positioned and shaped to reflect solar energy in the solar wavelength range to an energy absorber spaced apart from the first primary surface. and The second element, having a thermal conductivity greater than 0.1 W / mK, is thermally coupled to a second primary surface of the first element to transfer thermal energy from the second element to the first element to cool the second element. The first main surface includes a first region and the second main surface defines a second region, the first region and the second region being oriented at an angle to each other in order to facilitate the reception of reflected solar energy at the second region; as well as The energy absorber may include an internal volume to contain a fluid that can be heated by the solar energy, or the energy absorber may include a photovoltaic cell.

2. The article of claim 1, wherein the first element comprises a multilayer optical film.

3. The article of claim 2, wherein the first element comprises an ultraviolet-reflective multilayer optical film.

4. The article of claim 1, wherein the first element is a mirrored solar mirror within the solar wavelength range.

5. The article of claim 1, wherein the first main surface has a curved shape.

6. The article of claim 5, wherein the curved shape comprises a parabolic curve.

7. The article of claim 5, wherein the bending shape comprises a compound parabolic curve.

8. A passive cooling product, the passive cooling product comprising: A first element, the first element comprising a first region of a first primary surface, the first element being defined with a first absorbance greater than or equal to 0.5 in the atmospheric infrared wavelength range of 8 micrometers to 13 micrometers, and at least partially defined with a first average reflectance greater than or equal to 80% in the solar wavelength range; The second element, which has a thermal conductivity greater than 0.1 W / mK, is thermally coupled to a first region of a second main surface defined by the first element to transfer heat from the second element to the first element to cool the second element. and An energy absorber, comprising a second region of a first primary surface, configured to receive solar energy in the solar wavelength range of 0.35 micrometers to 2.5 micrometers, the energy absorber including an internal volume to accommodate a fluid capable of being heated by the solar energy, or the energy absorber comprising a photovoltaic cell. The first region of the first main surface is positioned and shaped to guide reflected solar energy within the solar wavelength range to the second region.

9. The article of claim 8, wherein the energy absorber includes an internal volume to contain a fluid capable of being heated using the solar energy.

10. The article of manufacture according to any one of claims 8 or 9, wherein the first region of the first main surface comprises a planar shape.

11. The article of claim 8, wherein the energy absorber comprises a photovoltaic cell.

12. The article of claim 8, wherein a first vector perpendicular to at least a portion of the first region of the first main surface and a second vector perpendicular to at least a portion of the second region of the first main surface define an element angle, the element angle being greater than or equal to 90 degrees and less than or equal to 175 degrees.

13. The article of manufacture according to claim 8, wherein the first element comprises a diffuse solar mirror in the solar wavelength range.

14. The article of claim 13, wherein the diffuse solar mirror comprises a microporous polymer layer or has an effective D-coating of up to 50 micrometers. 90 An array of inorganic particles of varying sizes.

15. The article of claim 8, further comprising a plurality of the first elements and a plurality of the second elements arranged in an alternating array between the first end region and the second end region.

16. The article of claim 8, wherein the second region of the first main surface comprises a curved shape.

17. A passive cooling system, the passive cooling system comprising: An energy absorber configured to receive solar energy in the solar wavelength range of 0.35 micrometers to 2.5 micrometers, the energy absorber including an internal volume to contain a fluid capable of being heated by the solar energy, or the energy absorber including a photovoltaic cell; A solar mirror element, wherein the solar mirror element is defined as having a first absorbance greater than or equal to 0.6 in the atmospheric infrared wavelength range of 8 to 13 micrometers, and at least partially defined as having a first average reflectance greater than or equal to 80% in the solar wavelength range, the solar mirror element comprising a first main surface shaped to guide reflected solar energy in the solar wavelength range to the energy absorber, and A coolable element, wherein the coolable element has a thermal conductivity greater than 0.1 W / mK, is thermally coupled to a second main surface of the solar mirror element to transfer heat from the coolable element to the solar mirror element to cool the coolable element.

18. The system of claim 17, wherein the energy absorber, the coolable element, or both are thermally coupled to the absorption cooler subsystem.

19. The system of claim 17, wherein the energy absorber, the coolable element, or both are thermally coupled to the steam condenser subsystem.

20. The system of claim 17, wherein the energy absorber is a photovoltaic module, and the coolable element is thermally coupled to cool the photovoltaic module.

21. The system of claim 20, wherein the photovoltaic module is designed to absorb solar energy in the range of 0.35 micrometers to 1.6 micrometers.

22. The system of claim 20, wherein the photovoltaic module is designed to absorb solar energy in the range of 0.35 micrometers to 1.1 micrometers.

23. The system of claim 20, wherein the photovoltaic module is designed to absorb solar energy in the range of 0.35 micrometers to 0.9 micrometers.

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