Systems, solar articles, and methods including structured protective films

Abstract

A system is described that includes a solar article (110) including a first major surface (facing the sun during daytime use) and an opposing second major surface. A protective film (150) comprising a first major surface (facing the sun during daytime use) and an opposing second major surface. A first major surface of the solar article (110) and / or an opposing second major surface of the protective film (150) includes a surface structure (153). The surface structure (153) is a microstructure and / or a nanostructure, the surface structure having at least two dimensions less than 1 mm. The structure is capable of providing / maintaining an air interface (175) between the first major surface of the solar article (110) and the second major surface of the protective film (150). Also described is a structured polyolefin film suitable for use as a protective film (150) for a solar article, as described herein, and a method of increasing the efficiency of a solar article.

Description

SUMMARY

[0001] Passive radiative cooling panels have been measured to have a soiling factor of 1 W / m 2 to 2 W / m 2 per day on rooftops in different locations, resulting in a solar reflectance decrease from 94% to 89% in 2 to 3 weeks. In certain locations, a solar reflectance below 90% results in no net radiative cooling during the midday hours due to solar absorption. Thus, passive radiative cooling panels can need to be cleaned every 2 to 3 weeks to maintain passive radiative daytime cooling to below ambient temperature during the midday hours.

[0002] In dry dusty environments, such as Arizona and Dubai, the power output of photovoltaic modules can decrease by 20% due to soiling. In dry dusty locations, photovoltaic modules are typically cleaned twice per month to maintain their power production.

[0003] The cost of cleaning such solar articles can increase their payback period. For example, the payback period of passive radiative cooling panels can be 4 years, but the cost of cleaning can increase that payback period to 6 years or more. The payback period of photovoltaic modules can increase from 8 years to 12 years, or even more, due to the cost of cleaning.

[0004] Various systems have been described for improving the efficiency of solar power generation (e.g., photovoltaic modules) with protective films. See, e.g., WO 2022 / 019735 and CN 113364410. While such systems focus on the efficiency loss caused by dust, they do not account for the solar transmission loss caused by the presence of the protective film. Thus, the industry would find advantages in systems, articles, and methods with protective films having structured surfaces (e.g., anti-reflective).

[0005] In one embodiment, a system is described that includes a solar article and a protective film. The solar article includes a first major surface (facing the sun during daytime use) and an opposing second major surface. The protective film includes a first major surface (facing the sun during daytime use) and an opposing second major surface. The first major surface of the solar article and / or the opposing second major surface of the protective film includes a surface structure. The surface structure is a microstructure and / or a nanostructure having at least two dimensions less than 1 mm. The structure can provide / maintain an air interface between the first major surface of the solar article and the second major surface of the protective film.

[0006] In one embodiment, the structured surface can improve transmission through the protective film into the underlying solar article. With reference to the transmission data reports in the subsequent examples, the protective film has a transmittance of at least 95%, 96%, 97%, 98%, or 99% for wavelengths greater than 0.75 microns (750 nm) to 2.5 microns, 2.0 microns, or 3.3 microns (3300 nm). In another embodiment, the protective film has a transmittance of at least 95%, 96%, 97%, 98%, or 99% for wavelengths greater than 3.6 microns (3600 nm) to 25.0 microns (25000 nm). In another embodiment, the protective film includes the foregoing structures and has a transmittance that is at least 1%, 2%, 3%, 4%, or 5% higher than the same protective film lacking the foregoing structures for wavelengths in the range of 0.75 microns to 2.5 microns, 3 microns, or 3.3 microns, or for wavelengths in the range of 3.6 microns to 25.0 microns. In another embodiment, the protective film (e.g., polyolefin) can facilitate the radiation of heat from the surface of a passive radiative cooling panel article to the sky.

[0007] In one embodiment, the protective film (e.g., for a cooling panel article) comprises a polyolefin material. The solar article (e.g., cooling panel) can include a multilayer film (e.g., free of fluorinated materials).

[0008] In one embodiment, the protective film is conveyed over a first major surface of a solar article by a roll-to-roll apparatus. In some embodiments, the system further includes an apparatus for cleaning at least the first major surface, and optionally the opposing major surface, of the protective film. The cleaning apparatus includes a pressure sensitive adhesive located on a roll. The system can include conveying the cleaned protective film over the major surface of the solar article.

[0009] Also described is a structured polyolefin film suitable for use as a protective film for a solar article as described herein, and a method of increasing the efficiency of a solar article. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1A is a cross-sectional view of a solar article including a protective film; Figure 1B is an enlarged view of the interface of a structured protective film with a solar article; Figure 2 is an enlarged view of the interface of a protective film with a structured surface of a solar article; Figure 3 is a cross-sectional view of an anti-reflective structured surface in the xz plane; Figure 4 is a top plan view of a protective film mechanically attached to a solar article; Figure 5 is a side view of a protective film being conveyed over a surface of a solar article; Figure 6 is a side view of a protective film being conveyed across a cleaning station and back onto the surface of a solar article. DETAILED DESCRIPTION

[0011] Described herein is a system including a solar article and a protective film. Representative solar articles include photovoltaic modules and passive cooling panels.

[0012] Figure 1A A cross-sectional view of a solar article 110 including a protective film 150 is depicted. The system 100 includes a solar article 110 having a first major surface 111 (facing the sun during daytime use of the solar article and system) and an opposing second major surface 112. The system 100 also includes a protective film 150 having a first major surface 151 (facing the sun during daytime use of the solar article and system) and a second major surface 152 adjacent to the first major surface 111 of the solar article 110.

[0013] Figure 1B is an enlarged view of the interface of the second major surface 152 of the protective film 150 with the first major surface 111 of the solar article. The second major surface 152 of the protective film 150 is a structured surface. The second major surface 152 of the protective film 150 includes structures 153, and an air interface 175 between the first major surface 111 of the solar article 110 and the second major surface 152 of the protective film 150. The structured surface of the protective film is selected so that more light passes through the protective film 150 to the first major surface 111 of the solar article 110.

[0014] Figure 2 is an enlarged view of another embodiment in which the first major surface 111 of the solar article 110 includes structures 153. In this embodiment, the protective film can be unstructured.

[0015] In another embodiment (not shown), the second major surface 152 of the protective film 150 includes structures, and the first major surface 111 of the solar article 110 includes structures 151.

[0016] An air interface 175 exists between the first main surface 111 of the solar cell 110 and the second main surface 152 of the protective film 150 because the protective film is adjacent to but not permanently bonded to the solar cell 110. Therefore, the protective film is typically not bonded to the first main surface of the solar cell 110 by chemical, thermal, or adhesive means. In another embodiment, it is envisioned that the protective film may be partially bonded to the first main surface of the solar cell 110, but 50% to 90% or more of the surface area of ​​the protective film is unbonded. An air interface exists between the unbonded portion of the second surface of the protective film and the first main surface of the solar cell 110. The air interface insulates the passively cooled surface 111 of the solar cell 110, achieving greater cooling below ambient temperature by minimizing convective heating of the air above the protective film.

[0017] The protective film can optionally be attached to the first primary surface of the solar product by any suitable method that does not eliminate the air interface between the solar product and the protective film, as will be described in more detail below.

[0018] Protective film

[0019] Generally, a protective film is placed between the outer (e.g., first primary) surface of a solar energy product and at least one solar energy source (e.g., the sun). The protective film may partially cover, but more typically it completely covers the first primary surface of the solar energy product.

[0020] Protective films are typically exposed to outdoor environmental factors, especially dust. They contain a predetermined amount of material suitable for use in outdoor environments for a specified period. For protective films that will be replaced when soiled, the predetermined usage period is usually less than one month. However, for protective films that can be reused after cleaning, the predetermined usage period can be six months, one year, or longer.

[0021] The protective film is formed from a material that provides high solar transmittance, allowing solar energy to pass through. One type of material with suitable low absorption and high solar transmittance is polyolefin. Polyolefins (such as polyethylene) are also transparent in the mid-infrared wavelength range of 8 to 13 micrometers, which facilitates the radiation of heat from the surface of a passively radiant cooling plate product beneath the polyolefin (such as polyethylene) film to the sky.

[0022] Exemplary polyolefin materials include low-density polyethylene, such as DOW 955I from Dow, and DOWLEX 2047G linear low-density polyethylene also from Dow, as DOWLEX 2047G; medium-density polyethylene (MDPE); and high-density polyethylene (HDPE). Polyolefin copolymers include polymethylpentene (PMP), poly(ethylene-co-octene) (PE-PO) (e.g., purchased under the trade name "ENGAGE 8200" from Dow Elastomers, Midland, MI, USA), and poly(propylene-co-ethylene) (e.g., purchased under the trade name "Z9470" from Atofina Petrochemicals, Inc., Houston, TX, USA); polypropylene copolymers, such as copolymers of atactic polypropylene (aPP) and isotactic polypropylene (iPP); cyclic olefin polymers (COP); and cyclic olefin copolymers (COC). In some implementations, the cyclic olefin copolymer is a copolymer of norbornene and ethylene, such as that available under the trade name Zeonor from Zeon Corporation.

[0023] In some embodiments, the density (ASTM D792) of the (e.g., polyethylene) polyolefin material is at least 0.90 g / cc, 0.91 g / cc, or 0.92 g / cc and less than 0.93 g / cc. In some embodiments, the melt index (190°C / 2.16 kg – ASTM D1238) of the (e.g., polyethylene) polyolefin material is at least 10 g / 10 min, 15 g / 10 min, 20 g / 10 min, 25 g / 10 min, or 30 g / 10 min and not greater than 40 g / 10 min, 45 g / 10 min, or 50 g / 10 min. In some embodiments, the tensile strength at break (ASTM D638) of the (e.g., polyethylene) polyolefin material is at least 5 MPa, 6 MPa, or 7 MPa and not greater than 10 MPa. In some embodiments, the elongation at break (ASTM D638) of the (e.g., polyethylene) polyolefin material is at least 50%, 75%, or 100% and not greater than 150%.

[0024] When solar energy products are photovoltaic modules, transparency at mid-infrared wavelengths is less important. Therefore, other film materials with high (e.g., visible light) solar transmittance can be utilized, such as acrylic acid (PMMA), acrylonitrile-butadiene-styrene copolymer (ABS), cellulose acetate, polystyrene (PS), polyvinyl chloride (PVC), polyesters including polyethylene terephthalate (PET), polyethylene terephthalate diol (PETg), polycyclohexanedimethyl terephthalate (PCT), polycyclohexanedimethyl terephthalate diol (PCTg), poly(1,4-cyclohexanedimethyl) terephthalate (PCTA); polycarbonate (PC), polyamides (including nylon), polyetherimide (PEI), polyphenylene sulfide (PPS), and fluoropolymers.

[0025] In some implementations, the protective film is a thermoplastic film suitable for recycling contaminated protective films or for preparing protective films from recycled materials. Melt or softening temperature is a physical property of thermoplastics. As used herein, the terms "hot melt" or "softening transition temperature" refer to the Vicat softening temperature of a (e.g., amorphous) thermoplastic polymer as measured according to ASTM D1525-17, or the melt temperature (Tm) of a crystalline thermoplastic polymer as measured by differential scanning calorimetry according to ASTM D3418.

[0026] In some embodiments, the heat-melting (DSC) or Vicat softening temperature (ASTM 1525) of the protective film is at least 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C. The heat-melting or softening temperature is typically no greater than 450°C, 425°C, 400°C, 375°C, 350°C, 325°C, 300°C, 275°C, 250°C, 200°C, or 175°C. In some embodiments, the heat-melting or softening temperature of the protective film (e.g., for polyolefins) is no greater than 180°C, 170°C, 165°C, 160°C, 155°C, 150°C, 145°C, 140°C, 135°C, 130°C, 125°C, or 120°C.

[0027] Structured surface

[0028] Reference Figure 1A and Figure 1BThe protective film includes a structure on at least the second main surface 152 adjacent to the first main surface 111 of the solar cell, and / or the first main surface of the solar cell includes the structure. At least two dimensions of the structure 151 are less than 1 mm. In some embodiments, these structures may be characterized as microstructures. As used herein, a microstructure refers to a structure with at least two dimensions (e.g., width and height) or all three dimensions (i.e., width, height, and length (maximum dimension)) being at least 1 micrometer and less than 1 mm. In some embodiments, the maximum dimension of the microstructure is no greater than 900 micrometers, 800 micrometers, 700 micrometers, 600 micrometers, 500 micrometers, 400 micrometers, 300 micrometers, 200 micrometers, or 100 micrometers. In some embodiments, the minimum dimension of the microstructure (e.g., peak width and / or peak height) is at least 2 micrometers, 3 micrometers, 4 micrometers, 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, or 10 micrometers. In some implementations, the minimum dimension of the microstructure (e.g., width and / or height) is at least 15 micrometers, 20 micrometers, 25 micrometers, 30 micrometers, 35 micrometers, 40 micrometers, 45 micrometers, or 50 micrometers.

[0029] In other embodiments, these structures may be characterized as nanostructures. As used herein, a nanostructure refers to a structure with at least one or two dimensions less than 1 micrometer. In some embodiments, the minimum dimension (e.g., peak height) of the nanostructure is at least 10 nm, 50 nm, 75 nm, 100 nm, 120 nm, 140 nm, 150 nm, 160 nm, 180 nm, 200 nm, 250 nm, or 500 nm. In some embodiments, the peak height of the nanostructure is in the range of 100 nm to 250 nm. In some embodiments, the peak height of the nanostructure is in the range of 75 nm to 160 nm.

[0030] Various structured surfaces are known in the literature. The base of each (e.g., micro)structure can have a variety of cross-sectional shapes, including but not limited to optional parallelograms with rounded corners, rectangles, squares, circles, semicircles, semi-ellipses, triangles, trapezoids, other polygons (e.g., pentagons, hexagons, octagons, etc.), and combinations thereof. In some embodiments, peak structures can be described as columnar, dome-shaped, rib-shaped, prismatic, or cubic angular elements.

[0031] In some embodiments, the structured surface of the protective film includes microstructures and nanostructures. In some embodiments, the structured surface of the protective film includes microstructures that further comprise nanostructures. The average distance between microstructure peaks is typically at least 10 times the average distance between nanostructure peaks.

[0032] Various types of structures can increase solar transmittance. In some implementations, structured surfaces can be described as matte structured surfaces, anti-glare structured surfaces, or more preferably, anti-reflective structured surfaces.

[0033] Matte and anti-glare structured surfaces can be characterized according to surface roughness standards. The average surface roughness (i.e., Ra) is typically less than 0.20 micrometers. Preferred embodiments with high transparency and sufficient haze exhibit an Ra of less than or equal to 0.18 micrometers, 0.17 micrometers, 0.16 micrometers, or 0.15 micrometers. In some embodiments, Ra is less than 0.14 micrometers, or 0.13 micrometers, or 0.12 micrometers, or 0.11 micrometers, or 0.10 micrometers. Ra is typically at least 0.04 micrometers or 0.05 micrometers.

[0034] In some embodiments, the microstructure of the matte film typically has a high degree of distribution. In some embodiments, the average height is no greater than about 5 micrometers, 4 micrometers, 3 micrometers, 2 micrometers, or 1 micrometer. The average height is typically at least 0.1 micrometers, 0.2 micrometers, 0.3 micrometers, 0.5 micrometers, or 0.5 micrometers.

[0035] Roughness can be determined as described in WO2010 / 141345; this document is incorporated herein by reference. Suitable microstructured matte layers can be formed using replication tools. Advantageously, this technique does not require the use of matte (e.g., inorganic) particles that typically reduce solar transmittance.

[0036] In a preferred embodiment, the structured surface of the second main surface of the protective film and / or the first main surface of the solar product can be characterized as anti-reflective.

[0037] According to the literature, antireflective films can be manufactured by other methods, such as coatings with matte particles, or by providing high-refractive-index and low-refractive-index layers on a substrate. However, such methods may introduce other materials (e.g., inorganic particles) that typically absorb or reflect wavelengths of solar radiation. Therefore, an overall improvement in the transmittance of solar wavelength light is usually not achievable.

[0038] Various structured surfaces, including microstructures and / or nanostructures (e.g., antireflective surfaces), are known, as well as methods for fabricating such structured surfaces. See, for example, WO2019 / 130198; this document is incorporated herein by reference.

[0039] Figure 3An antireflective surface 202 of a specific implementation of layer 208 is shown, having nanostructures 330, 332 (visible in two magnified overlay images) disposed on the surface of microstructures (also referred to as micropeaks). Structured surfaces include nanostructures located on microstructure peaks (e.g., linear prisms) and nanostructures located on unstructured surfaces (e.g., mesa layers, planar channels) between microstructures. At least one micropeak 220 may include at least one first microsegment 224 or at least one second microsegment 226. Microsegments 224, 226 may be disposed on opposite sides of a vertex 248 of micropeak 220. Vertex 248 may be, for example, the highest point or local maximum of line 214. Each microsegment 224, 226 may include at least one: a straight segment or a curved segment.

[0040] The line 214 defining the first micro-segment 224 and the second micro-segment 226 can have a first average slope and a second average slope, respectively. The slope can be defined relative to the baseline 250, which serves as the x-axis (horizontal displacement), and the orthogonal direction is the z-axis (vertical rise and fall).

[0041] As used herein, the term "average slope" refers to the average slope over a specific portion of the line. In some embodiments, the average slope of the first micro-segment 224 may refer to the slope between the endpoints of the first micro-segment. In some embodiments, the average slope of the first micro-segment 224 may refer to an average calculated from slopes measured at multiple points along the first micro-segment.

[0042] 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 can be equal to the absolute value of the second average slope of the micro-peak. In some embodiments, the absolute values ​​can be different. In some embodiments, the absolute value of each average slope of micro-segments 224, 226 can be greater than the absolute value of the average slope of micro-space 222.

[0043] The angle A of micro-peak 220 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 224 and the second micro-segment 226. 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 224, 226.

[0044] Angle A can be within a range that provides sufficient anti-reflective properties to surface 202. 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).

[0045] Micropeak 220 can be any suitable shape capable of providing angle A based on the average slope of microsegments 224, 226. In some embodiments, micropeak 220 is typically formed in a triangular shape. In some embodiments, micropeak 220 is not triangular. The shape can be symmetrical about the z-axis passing through vertex 248. In some embodiments, the shape can be asymmetrical.

[0046] Each microspace 222 can define a microspace width 242. The microspace width 242 can be defined as the distance between corresponding boundaries 216, which can be between adjacent micropeaks 220.

[0047] The minimum value of the microspace width 242 can be defined in micrometers. In some embodiments, the microspace width 242 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 242 is at least 50 micrometers at the lower end (in some embodiments, at least 60 micrometers). In some applications, the microspace width 242 is at most 90 micrometers at the upper end (in some embodiments, at most 80 micrometers). In some applications, the microspace width 242 is 70 micrometers.

[0048] 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.

[0049] The microspace width 242 can also be defined relative to the micropeak distance 240. Specifically, the minimum value of the microspace width 242 can be defined relative to the corresponding micropeak distance 240, which can refer to the distance between the closest pair of micropeaks 220 surrounding the microspace 222, measured at each vertex 248 of the micropeaks 220. In some embodiments, the microspace width 242 can be at least 10% of the maximum value of the micropeak distance 240 (in some embodiments, at least 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, or even at least 90%). In some embodiments, the lower limit of the minimum value of the microspace width 242 is at least 30% of the maximum value of the micropeak distance 240 (in some embodiments, at least 40%). In some embodiments, the upper limit of the minimum value of the microspace width 242 is at most 60% of the maximum value of the micropeak distance 240 (in some embodiments, at most 50%). In some embodiments, the microspace width 242 is 45% of the micropeak distance 240.

[0050] The minimum value of the micro-peak distance 240 can be defined in micrometers. In some embodiments, the micro-peak distance 240 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 micro-peak distance 240 is at least 100 micrometers.

[0051] The maximum value of the micro-peak distance 240 can be defined in micrometers. The micro-peak distance 240 can be up to 1000 micrometers (in some embodiments, up to 900 micrometers, 800 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 upper limit of the micro-peak distance 240 is at most 200 micrometers. In some embodiments, the lower limit of the micro-peak distance 240 is at least 100 micrometers. In some embodiments, the micro-peak distance 240 is 150 micrometers.

[0052] Each micropeak 220 may define a micropeak height 246. The micropeak height 246 may be defined as the distance between the baseline 350 and the apex 248 of the micropeak 220. The minimum value of the micropeak height 246 may be defined in micrometers. In some embodiments, the micropeak height 246 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 246 is at least 60 micrometers (in some embodiments, at least 70 micrometers). In some embodiments, the micropeak height 246 is 80 micrometers.

[0053] Multiple nanostructures 330, 332 may be at least partially defined by line 214. Multiple nanostructures 330 may be disposed on at least one microspace 222. Specifically, the line 314 defining the nanostructures 330 may include at least a series of nanopeaks 320 disposed on at least one microspace 222. In some embodiments, at least a series of nanopeaks 320 of the multiple nanostructures 332 may also be disposed on at least one micropeak 220.

[0054] Due to at least the difference in size, the microstructure 218 may be more durable in terms of wear resistance than the nanostructures 330 and 332. In some embodiments, the multiple nanostructures 332 are disposed only on the microspace 222, or at least not near or adjacent to the apex 248 of the micropeak 220.

[0055] Each nanopeak 320 may include at least one of a first nanosegment 324 and a second nanosegment 326. Each nanopeak 320 may include both nanosegments 324 and 326. Nanosegments 324 and 326 may be disposed on opposite sides of the apex 348 of the nanopeak 320.

[0056] The first nanosegment 324 and the second nanosegment 326 can respectively define a first average slope and a second average slope, which describe the line 314 that defines the nanosegment. For nanostructures 330 and 332, the slope of the line 314 can be defined relative to a baseline 350, which serves as the x-axis (horizontal displacement), and the orthogonal direction is the z-axis (vertical rise and fall).

[0057] 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 the nanopeak can be equal to the absolute value of the second average slope of the nanopeak (e.g., nanostructure 330). In some embodiments, these absolute values ​​may be different (e.g., nanostructure 332).

[0058] Angle B of nanopeak 320 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 324 and 326.

[0059] Angle B can be within a range that provides sufficient anti-reflective properties to surface 202. 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.

[0060] For each nanopeak 320, the angle B may be the same or different. For example, in some embodiments, the angle B of the nanopeak 320 on the micropeak 220 may be different from the angle B of the nanopeak 320 on the microspace 222.

[0061] The nanopeak 320 can be any suitable shape capable of providing an angle B based on a line defined by the average slope of nanosegments 324, 326. In some embodiments, the nanopeak 320 is typically formed in a triangular shape. In at least one embodiment, the nanopeak 320 is not triangular. The shape can be symmetrical about the vertex 348. For example, the nanopeak 320 of the nanostructure 330 disposed on the microspace 222 can be symmetrical. In at least some embodiments, the shape can be asymmetrical. For example, the nanopeak 320 of the nanostructure 332 disposed on the micropeak 220 can be asymmetrical, where one nanosegment 324 is longer than the other nanosegment 326. In some embodiments, the nanopeak 320 can be formed without a bottom cut.

[0062] Each nanopeak 320 can define a nanopeak height 346. The nanopeak height 346 can be defined as the distance between the baseline 350 and the apex 348 of the nanopeak 320. The minimum value of the nanopeak height 346 can be defined in nanometers. In some embodiments, the nanopeak height 346 can 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).

[0063] In some embodiments, the nanopeak height 346 is at most 250 nanometers (in some embodiments, at most 200 nanometers), particularly for the nanostructure 330 on the microspace 222. In some embodiments, the nanopeak height 346 is in the range of 100 nanometers to 250 nanometers (in some embodiments, 160 nanometers to 200 nanometers). In some embodiments, the nanopeak height 346 is 180 nanometers.

[0064] In some embodiments, the nanopeak height 346 is at most 160 nanometers (in some embodiments, at most 140 nanometers), particularly for the nanostructure 332 on the micropeak 220. In some embodiments, the nanopeak height 346 is in the range of 75 nanometers to 160 nanometers (in some embodiments, 100 nanometers to 140 nanometers). In some embodiments, the nanopeak height 346 is 120 nanometers.

[0065] As used herein, the term "corresponding micropeak" refers to a micropeak 220 on which nanopeak 320 is disposed, or, if the nanopeak is disposed on a corresponding microspace 222, to one or both of the nearest micropeaks surrounding that microspace. In other words, micropeak 220 corresponding to microspace 222 refers to the micropeak located before and after that microspace in the series of micropeaks.

[0066] The nanopeak height 346 can also be defined relative to the micropeak height 246 of the corresponding micropeak 220. In some embodiments, the corresponding micropeak height 246 can be at least 10 times the nanopeak height 346 (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 246 at the lower end is at least 300 times the nanopeak height 346 (in some embodiments, at least 400, 500, or even at least 600 times). In some embodiments, the corresponding micropeak height 246 at the upper end is at most 900 times the nanopeak height 346 (in some embodiments, at most 800 or even at most 700 times).

[0067] The nano-peak distance 340 can be defined between nano-peaks 320. A maximum value for the nano-peak distance 340 can be defined. In some embodiments, the nano-peak distance 340 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 340 is up to 400 nanometers (in some embodiments, up to 300 nanometers).

[0068] A minimum value for the nanometer peak distance of 340 can be defined. In some embodiments, the nanometer peak distance of 340 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 nanometer peak distance of 340 is at least 150 nanometers (in some embodiments, at least 200 nanometers).

[0069] In some embodiments, the nanopeak distance 340 is in the range of 150 nm to 400 nm (in some embodiments, 200 nm to 300 nm). In some embodiments, the nanopeak distance 340 is 250 nm.

[0070] The nanopeak distance 340 can be defined relative to the micropeak distance 240 between the corresponding micropeaks 220. In some embodiments, the corresponding micropeak distance 240 is at least 10 times the nanopeak distance 340 (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 240 at the lower end is at least 200 times the nanopeak distance 340 (in some embodiments, at least 300 times). In some embodiments, the corresponding micropeak distance 240 at the upper end is at most 500 times the nanopeak distance 340 (in some embodiments, at most 400 times).

[0071] In some embodiments of the antireflective surface 202 forming layer 208, a method may include extruding a thermoplastic (e.g., polyolefin) material. The extruded material may be shaped using a microreplication tool. The microreplication tool may include a series of microstructures mirrored together, which may form a series of microstructures on the surface of layer 208. 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.

[0072] 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.

[0073] 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 cutting width (p2) and .

[0074] These nanostructures can be characterized as embedded within the microstructured surface of layer 208. Except for the portion of the nanostructure exposed to air, the shape of the nanostructure can generally be defined by the adjacent microstructured material.

[0075] In some implementations, multiple nanostructures can be formed by shaping extruded material or layer 208 using a micro-replicating tool, which also has a nanostructured particle coating for embossing. 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 fabricated 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 fabricated in the master surface of an optical film to provide light-diffusing properties. An example of an electrochemical deposition technique is described in the following U.S. patent application, which has U.S. Serial No. 62 / 446821, PCT Publication No. WO 2018 / 130926, published on July 19, 2018 (Derks et al.), filed on January 16, 2017, entitled “Faceted Micro-structured Surface”, the disclosure of which is incorporated herein by reference in its entirety.

[0076] The protective film 150 may optionally include a structure on a first main surface 151 that faces the sun during daytime use of the solar product. The optional structure of the first main surface 151 of the protective film 150 may be described as an anti-reflective, anti-glare, or matte surface.

[0077] In some embodiments, an optional structured surface of the first primary surface of the protective membrane can prevent the presence of microorganisms (e.g., bacteria such as Streptococcus mutans, Staphylococcus aureus, or Pseudomonas aeruginosa) on the structured surface, or in other words, reduce or prevent biofilm formation. Various structured surfaces have been described in the literature, including US2017 / 0100332, WO2013 / 003373, and WO 2012 / 058605; these documents are incorporated herein by reference.

[0078] In some embodiments, the structured surface of the membrane may be selected to provide one or more of the following properties: i) a reduction in microbial contact transfer of at least 25%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, 90%, 95%, or 99%; ii) a logarithmic reduction in microorganisms (e.g., bacteria) to base 10 of at least 2, 3, 4, 5, 6, 7, or 8 after cleaning; iii) at least 50%, 60%, 70%, 80%, or 90% of the structured surface containing the cleaning solution after applying the cleaning solution to the (e.g., micro)structured surface for 1 to 3 minutes. Such structured surfaces are described in WO2022 / 162528, which is incorporated herein by reference.

[0079] In this implementation, the microstructure typically has a sidewall angle greater than 10, 15, 20, 25, 30, 35, 40, or 45 degrees.

[0080] In some implementations, the structured surface includes microstructures, wherein the maximum width or average width of the valleys (e.g., Figure 3The valley width (240) is at least 1 micrometer, 2 micrometers, 3 micrometers, or 4 micrometers, more typically greater than 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, or 10 micrometers, and can range up to 250 micrometers. In some embodiments, the valley width is at least 11 micrometers, 12 micrometers, 13 micrometers, 14 micrometers, 15 micrometers, 16 micrometers, 17 micrometers, 18 micrometers, 19 micrometers, 20 micrometers, 21 micrometers, 22 micrometers, 23 micrometers, 24 micrometers, or 25 micrometers. In some embodiments, the valley width is at least 30 micrometers, 35 micrometers, 40 micrometers, 45 micrometers, or 50 micrometers. In some embodiments, the valley width is at least 50 micrometers, 55 micrometers, 60 micrometers, 65 micrometers, 70 micrometers, 75 micrometers, 85 micrometers, 85 micrometers, 90 micrometers, 95 micrometers, or 100 micrometers. In some embodiments, the valley width is at least 125 micrometers, 150 micrometers, 175 micrometers, 200 micrometers, 225 micrometers, or 250 micrometers. In some implementations, the width of the valley is no greater than 1000 micrometers, 950 micrometers, 900 micrometers, 850 micrometers, 800 micrometers, 750 micrometers, 700 micrometers, 650 micrometers, 600 micrometers, 550 micrometers, 500 micrometers, 450 micrometers, 400 micrometers, 350 micrometers, 300 micrometers, 250 micrometers, 225 micrometers, 200 micrometers, 175 micrometers, 150 micrometers, 125 micrometers, 100 micrometers, 75 micrometers, or 50 micrometers.

[0081] In some implementations, the maximum width or average width of the peak (i.e. Figure 3 (244) is roughly the same as the valley. In other embodiments, the peak width differs from the valley width, but may fall within the same range as the valleys mentioned above.

[0082] The height of the peak is typically within the same range as the maximum width of the valley. In some embodiments, the peak structure typically has a height (H) ranging from 1 micrometer to 125 micrometers. In some embodiments, the height of the microstructure is at least 2 micrometers, 3 micrometers, 4 micrometers, or 5 micrometers. In some embodiments, the height of the microstructure is at least 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, or 10 micrometers. In some embodiments, the height of the microstructure is not greater than 100 micrometers, 90 micrometers, 80 micrometers, 70 micrometers, 60 micrometers, or 50 micrometers. In some embodiments, the height of the microstructure is not greater than 45 micrometers, 40 micrometers, 35 micrometers, 30 micrometers, or 25 micrometers. In some embodiments, the height of the microstructure is not greater than 24 micrometers, 23 micrometers, 22 micrometers, 21 micrometers, 20 micrometers, 19 micrometers, 18 micrometers, 17 micrometers, 16 micrometers, 15 micrometers, 14 micrometers, 13 micrometers, 12 micrometers, 11 micrometers, or 10 micrometers. In typical embodiments, the height of the valley or channel is within the same range just described for the peak structure. In some embodiments, the peak structure and the valley have the same height. In other implementations, the peak structure can vary in height.

[0083] The aspect ratio of a valley is its height (which may be the same as the peak height of the structure) divided by its maximum width. In some embodiments, the valley aspect ratio is at least 0.1, 0.15, 0.2, or 0.25. In some embodiments, the valley aspect ratio is not greater than 1, 0.9, 0.8, 0.7, 0.6, or 0.5. Therefore, in some embodiments, the valley height is typically not greater than the valley's maximum width, and more typically less than the valley's maximum width.

[0084] In some embodiments, the peak structure comprises two or more facets. The peak structure has sharp, rounded, or truncated apexes. The peak structure may have apex angles ranging from 20 to 120 degrees or from 80 to 100 degrees. In some embodiments, the (e.g., micro)structured surface comprises less than 50%, 40%, 30%, 20%, or 10% of a flat surface area parallel to the planar substrate. In some embodiments, these facets may form continuous or semi-continuous surfaces in the same direction. In some embodiments, the valleys lack intersecting walls.

[0085] Solar article

[0086] This system can be used in a variety of solar energy products. The term "solar energy product" refers to a product whose primary purpose is to convert solar energy (e.g., on Earth) or to reflect solar energy to minimize solar energy absorption and thus achieve passive cooling.

[0087] In some implementations, solar energy products convert solar energy into electrical energy, such as photovoltaic modules.

[0088] In other embodiments, the solar panel may be part of a cooling plate that may be installed on the exterior of at least a portion of a building. The cooling plate reflects sunlight to prevent it from heating up during the day. In some embodiments, the cooling plate also emits infrared heat into the cold sky (e.g., at night), thereby cooling the plate and any fluids flowing therein.

[0089] Cooling articles can be applied to substrates or objects to reflect light from the solar region of the electromagnetic spectrum and radiate light from the atmospheric window region of the electromagnetic spectrum, both of which can cool the substrate. While some applications are mentioned herein, passive cooling articles can be used in any outdoor environment to cool structures, especially those exposed to sunlight. Non-limiting examples of applications for passive cooling articles include commercial building air conditioning, commercial refrigeration (e.g., supermarket refrigerated display cases), heat transfer plates for cooling fluids that can be coupled to air conditioning and refrigeration systems, cooling of data center heat transfer fluid systems, generator cooling, or vehicle air conditioning or refrigeration (e.g., automobiles, trucks, trains, buses, ships, aircraft, etc.), outdoor power transformers, outdoor electrical switch boxes, or electric vehicle battery cooling. Passive cooling articles can be integrated with air conditioning and refrigeration systems and can be used to replace air conditioning units, depending on climatic conditions. In some embodiments, passive cooling articles can replace refrigerant condensers in air conditioning and refrigeration systems.

[0090] Cooling products can utilize selected material layers to provide specific reflectivity and emission characteristics. The amount of cooling and the degree of temperature reduction may depend on the product's reflection and absorption properties.

[0091] In some implementations, (e.g., passively) cooled solar products reflect at least 90% of light with wavelengths from 300 nm to 2500 nm.

[0092] In some embodiments, (e.g., passively cooled articles include a surface coating comprising solar reflective pigments and microspheres, as described in U.S. Patent 7,503,971. In some embodiments, the surface of (e.g., passively radiatively cooled articles) may comprise at least one of ZnO, Si, HfD2, or ZnO2, as described in U.S. Patent 11,359,841. Such (e.g., passively cooled articles) are commercially available from SkyCool Systems, Inc.

[0093] In some embodiments, (e.g., passively) cooled articles include multilayer optical films as solar reflectors. The multilayer optical films can be very thin to facilitate heat transfer. In some embodiments, the total thickness of the multilayer films is no greater than 50 micrometers, 40 micrometers, 30 micrometers, 25 micrometers, 20 micrometers, 15 micrometers, or 10 micrometers. The number of layers in the multilayer film can reach 1000, 1500, or 2000 layers (in some embodiments, up to 700, 600, 500, 400, 300, 250, 200, 150 layers, or even up to 100 layers).

[0094] Adjacent optical layers can have different refractive indices. The first optical layer can be described as a low-refractive-index layer, and the second optical layer can be described as a high-refractive-index layer, and vice versa.

[0095] Exemplary polymers that can be used to form high-refractive-index optical layers include polyethylene terephthalate (PET), purchased from 3M Company and also from Nan Ya Plastics Corporation, Wharton, TX. Copolymers of PET comprising PETG and PCTG (obtained under the trade names “SPECTAR 14471” and “EASTARGN071” 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.

[0096] Exemplary 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 exemplary optical polymers include acrylate triblock copolymers, wherein each end block of at least one of the first block copolymer, the second block copolymer, or at least one additional block copolymer is composed of polymethyl methacrylate, and further wherein each middle block of at least one of the first block copolymer or the second block copolymer is composed of polybutyl acrylate. In some exemplary 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 comprises 30% to 80% by weight of terminal blocks and 20% to 70% by weight of intermediate blocks. In some specific exemplary 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 comprises 50% to 70% by weight of terminal blocks and 30% to 50% by weight of intermediate blocks. In any of the above exemplary embodiments, the first block copolymer may be selected to be the same as the second block copolymer. Triblock acrylate copolymers are, for example, available under the trade name “KURARITY LA4285” from Kuraray America, Inc., Houston, TX.

[0097] Additional suitable polymers used in low-refractive-index optical layers may include polyolefin copolymers, as described above for protective films. Multilayer optical films may also contain functionalized polyolefins, such as linear low-density polyethylene grafted with maleic anhydride (LLDPE-g-MA) (e.g., available under the trade name “BYNEL 4105” from DuPont du Pont de Nemours & Co., Inc., Wilmington, Delaware, USA).

[0098] The multilayer optical films described herein can be manufactured 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 in its entirety.

[0099] In one embodiment, the multilayer optical film may include a first optical layer and a second optical layer, wherein the first optical layer comprises a fluoropolymer and the second optical layer comprises a polyester, such as polyethylene terephthalate (PET), as described in WO2019 / 130199, which is incorporated herein by reference. In other embodiments, the multilayer optical film includes a first optical layer comprising a non-fluorinated low-refractive-index optical layer, such as CoPMMA, as described herein.

[0100] In some embodiments, the multilayer optical film may include a metal layer. Non-limiting examples of metals used in the metal layer include at least one of the following: silver (Ag), copper (Cu), aluminum (Al), gold (Au), Inconel, stainless steel, or various combinations thereof. In some embodiments, the metal layer comprises a 100-nanometer-thick silver layer and a 20-nanometer-thick copper layer to protect the silver from corrosion.

[0101] In some embodiments, the multilayer film exhibits high reflectivity in a lower wavelength range, while the metal layer exhibits high reflectivity in a higher wavelength range. In one embodiment, the multilayer film exhibits high reflectivity in the range of 0.35 micrometers to 0.8 micrometers. In another embodiment, the metal layer exhibits high reflectivity in the range of 0.8 micrometers to 2.5 micrometers. Together, the multilayer film and the metal layer provide high reflectivity in the range of 0.35 micrometers to 2.5 micrometers.

[0102] In some embodiments, the multilayer film may include inorganic particles. These structures may include inorganic particles when (e.g., passively) cooled articles include structured surfaces. For example, each depicted structure may correspond to one inorganic particle. The inorganic particle may be dispersed in at least one layer or disposed on at least one layer. The inorganic particle may comprise titanium dioxide, silicon dioxide, zirconium oxide, or zinc oxide. The inorganic particle may be in the form of nanoparticles, including nano-titanium dioxide, nano-silica, nano-zirconia, or even nanoscale zinc oxide particles. The inorganic particle may be in the form of beads or microspheres. The inorganic particles may be formed from ceramic materials, glass, or various combinations thereof. In some embodiments, the effective density of the inorganic particles is... 90 The particle size is at least 1 micrometer (in some embodiments, at least 3, 5, 6, 7, 8, 9, 10, or even at least 13 micrometers). In some embodiments, the inorganic particles have an effective density of up to 40 micrometers (in some embodiments, up to 25, 20, 15, 14, 13, 12, 11, 10, 9, or even up to 8 micrometers). 90 granularity.

[0103] In some embodiments, the cooling film can be characterized as a composite cooling film. An exemplary composite cooling film including a microporous layer is described in US11634613l, which is incorporated herein by reference. Such a microporous layer may include a micropore membrane.

[0104] The reflective microporous layer may comprise a network of interconnected and / or discrete voids, which may be spherical, oval, or some other shape. The primary functions of the reflective microporous layer include reflecting at least a portion of the visible and infrared radiation of the solar spectrum and emitting thermal radiation in atmospheric windows (i.e., wavelengths of 8 to 14 micrometers).

[0105] Therefore, the reflective microporous layer has voids with appropriate sizes that allow it to diffusely reflect wavelengths in the range of 400 nm to 2500 nm. Generally, this means that the void sizes should be within a certain range (e.g., 100 nm to 3000 nm). Preferably, there exists a range of void sizes corresponding to those sizes to achieve effective broadband reflection. As used herein, the term "polymer" includes both synthetic and natural organic polymers (e.g., cellulose and its derivatives).

[0106] 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. Therefore, the porosity and thickness of the reflective microporous layer are important variables. Generally, higher porosity and greater thickness are associated with higher reflectivity. However, for cost reasons, film thickness is preferably minimized, but this is not mandatory. Therefore, the thickness of the reflective microporous layer is typically in the range of 10 micrometers to 500 micrometers, preferably in the range of 10 micrometers to 200 micrometers, but this is not mandatory. Similarly, the porosity of the reflective microporous layer is typically in the range of 10 vol% to 90 vol%, preferably in the range of 20 vol% to 85 vol%, but this is not mandatory.

[0107] 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 reflects the maximum amount of solar energy in the range of 400 nanometers (nm) to 2500 nanometers. Specifically, the use of fluoropolymer blends in this microporous polymer film can provide greater reflectivity than other conventional multilayer optical films. Furthermore, inorganic particles comprising barium sulfate, calcium carbonate, silica, alumina, aluminum silicate, zirconium oxide, and titanium dioxide can be blended into the microporous polymer film to provide high solar reflectivity in the 0.4-micrometer to 2.5-micrometer solar radiation spectrum and high absorptivity in the 8-micrometer to 13-micrometer atmospheric window.

[0108] In other embodiments, the composite (e.g., passive) cooling film may comprise an organic polymer layer filled with reflective, non-porous inorganic particles. An exemplary composite (e.g., passive) cooling film comprising an organic polymer layer filled with reflective, non-porous inorganic particles is described in US11,654,664, which is incorporated herein by reference.

[0109] In some embodiments, such a layer may take the form of a pre-formed inorganic particle-filled membrane. "Pre-formed" means that the layer already exists in a stable and operable form before being bonded to the protective layer described herein. This pre-formed inorganic particle-filled membrane may be, for example, a polymethyl methacrylate (PMMA) membrane or a copolymethyl methacrylate (CMA) membrane filled with an appropriate amount of reflective inorganic particles. In some embodiments, the reflective layer may be a paint layer derived from a suitable paint containing an appropriate amount of reflective inorganic particles. Any such paint may be applied, for example, by brushing or otherwise coated onto a suitable substrate and then allowed to cure. The painted substrate may be bonded to other layers to form a passive radiative cooling film. Further detailing the reflective organic polymer layer, the porosity of the reflective non-porous inorganic particle-filled organic polymer layer may be less than 10%.

[0110] Exemplary inorganic particles for use in an organic polymer layer filled with inorganic particles may be selected from, for example, titanium dioxide, magnesium oxide, zinc oxide, calcium carbonate, hydroxyapatite, barium sulfate, silica, zirconium dioxide, cerium oxide, aluminum silicate, kaolin clay, and combinations and blends thereof. The inorganic particles may be present in any loading (weight percentage, based on the total weight of the layer). By definition, an organic polymer layer filled with inorganic particles will contain at least 5% by weight of reflective inorganic particles. In various embodiments, reflective inorganic particles may constitute at least 10%, 15%, 20%, 30%, 40%, 50%, 60%, or 70% by weight of the organic polymer layer filled with inorganic particles. The reflective inorganic particles may include any suitable average particle size and particle size distribution. In some embodiments, at least 20%, 40%, 60%, 80%, or 90% (by number average) of the reflective inorganic particles may exhibit a diameter of less than 5.0 micrometers, 2.0 micrometers, or 1.0 micrometers (or equivalent diameter if irregularly shaped). In some implementations, at least 90%, 95%, or 98% of the inorganic particles may be nanoparticles with a diameter or equivalent diameter of less than 1000 nanometers. If desired, the particles may be surface-treated to enhance their ability to disperse in organic polymer materials.

[0111] In some implementations, the inorganic particle-filled organic polymer layer can take the form of a pre-fabricated inorganic particle-filled organic polymer film, which means that the reflective layer already exists in a stable and operable form before it is combined with other layers to form a cooling film.

[0112] Such pre-formed inorganic particle-filled organic polymer films can be, for example, polymethyl methacrylate (PMMA) films, copolymethyl methacrylate (CoPMMA) films, or even block copolymer CoPMMA (such as those available from Kuraray) blended with sufficient amounts of barium sulfate, titanium dioxide, and / or calcium carbonate. However, any suitable organic polymer material can be used, provided it exhibits sufficient mechanical properties and can be filled with an acceptable amount of reflective inorganic particles. Any such layer can be bonded to any other layer mentioned herein, for example, by laminating such layers together using one or more layers of pressure-sensitive adhesive.

[0113] In some embodiments, the curing of the organic polymer binder in the paint may not involve a chemical reaction (formation of chemical bonds). In other embodiments, such as if the paint contains one or more thermosetting components, such as drying oils like linseed oil, curing may involve at least some bond formation. Generally, the organic polymer binder of such paint can be selected from or include materials such as alkyd resins, acrylic resins, vinyl acrylic resins, styrene-acrylic resins, vinyl acetate / ethylene resins, polyurethanes, polyesters, melamine resins, epoxy resins, polysiloxanes, polylactic acid, cellulose, polysaccharides, etc. In specific embodiments, such binders may be acrylic materials containing, for example, polymethyl methacrylate and / or copolymers thereof. The binder will provide the cured paint layer with properties such as mechanical durability, toughness, abrasion resistance, etc. The paint may contain any other materials required for any other purpose, such as leveling agents, viscosity modifiers, dyes, biocides, emulsifiers, etc. Suitable paints that can be used to form a reflective layer suitable for the purposes described herein may include, for example, those described in U.S. Patent No. 10,323,151, which is incorporated herein by reference for this purpose. Examples of potentially suitable paints include products available from a variety of sources, such as Solarkote, SunTech Coatings, Tropi-Cool, Thermocool Systems, Sherwin-Williams, and Exterior Performance Coatings. It should be understood that many of these paints contain one or more UV-blocking additives, etc.

[0114] The reflective layer may have an average reflectivity of at least 85% (in some embodiments, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or even at least 99.5%) in a wavelength range of at least 400 nm to 700 nm. Therefore, in some embodiments, the reflective layer may have an average reflectivity of at least 85% (in some embodiments, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or even at least 99.5%) in a wavelength range of at least 300 nm to 2500 nm.

[0115] Additives for multilayer optical films and / or protective films

[0116] The multilayer film of passively cooled articles may also contain ultraviolet absorber (UVA) and hindered amine light stabilizer (HAL). Exemplary UVA includes those available from BASF Corporation of Florham Park, NJ, under the trade names “TINUVIN 1577” and “TINUVIN 1600”. Typically, UVA is incorporated into the polymer at a concentration of 1% to 10% by weight. Exemplary HAL includes those available from BASF under the trade names “CHIMMASORB 944” and “TINUVIN 123”. Typically, HAL is incorporated into the polymer at a concentration of 0.1% to 1.0% by weight. An optimal UVA to HAL ratio is 10:1.

[0117] Multilayer films in passively cooled products can also contain UV-blocking additives, such as small-particle, non-pigmented zinc oxide and titanium dioxide, which can be used, particularly in the skin layer. The nanoscale particles of zinc oxide and titanium dioxide reflect or scatter ultraviolet light while remaining transparent to visible and near-infrared light. These ultraviolet-reflective micro-zinc oxide and titanium dioxide particles are available, for example, from Kobo Products, Inc., SouthPlainfield, NJ, and range in size from 10 nanometers to 100 nanometers.

[0118] The protective film may also contain additives, provided that these additives do not reduce the high transmittance of solar wavelength light.

[0119] In some implementations, the protective film may also contain antistatic agents, particularly in the skin layer, to reduce undesirable adsorption of dust, dirt, and debris. Ionic salt antistatic agents were purchased from 3M. Other antistatic additives were purchased under the trade name “STAT-RITE” from Lubrizol Engineered Polymers, Brecksville, OH, USA, or under the trade name “PELESTAT” from Sanyo Chemical Industries, Tokyo, Japan.

[0120] In some embodiments, the protective film may also contain low surface energy additives, such as additives containing fluorinated groups, silane groups, siloxane groups, or combinations thereof.

[0121] System and method for replacing / replenishing protective film

[0122] The protective film may optionally be attached to the first main surface of the solar cell by any suitable means that does not eliminate the air interface between the solar cell and the protective film. For example, the protective film may optionally be attached to the first main surface of the solar cell by electrostatic energy, (e.g., low-pressure) vacuum, mechanical components, or a combination thereof.

[0123] In one embodiment, the protective film may be (temporarily) adhesively bonded or mechanically attached to the solar product at its peripheral edges to prevent dust, rainwater, and other contaminants from entering between the protective film and the solar product.

[0124] Reference Figure 4 In one embodiment, the solar product includes a frame member 420 attached via a hinge 421. During use, the frame member 420 contacts a protective film 450 at the periphery of the underlying solar product (not shown). To replace the protective film, it can be disengaged from the frame member 420 by rotating each member about the axis of the hinge 421 (e.g., up to 180 degrees or more). The contaminated protective film can then be replaced with a clean one.

[0125] In other embodiments, a protective film is applied to the first primary surface of the solar product using a roll-to-roll system and method.

[0126] Reference Figure 5 In one embodiment, the roll-to-roll system 500 and method include a first (e.g., unwinding) roller 531 comprising a roll of uncontaminated (e.g., polyolefin) protective film; and a second (e.g., winding) roller 532 comprising a contaminated (e.g., polyolefin) protective film. The uncontaminated protective film of roller 531 is conveyed across the surface 511 of the solar product 510 by the winding action of roller 532. The winding action of the second roller 532 can be continuous or intermittent. In one embodiment, the winding action is responsive to data regarding the performance of the solar product (e.g., power output) or a sensor monitoring the transparency of the protective film. When the power output or transparency drops below a predetermined threshold, the second (e.g., winding) roller 532 opens for a predetermined time period based on the size of the solar product, thereby conveying the uncontaminated protective film across the surface of the solar product and winding the contaminated film onto the second roller 532. When the second roller 532 encounters resistance as roller 531 reaches the end of the roll, the roller 532 with the contaminated protective film is removed and discarded or recycled. A new roll of uncontaminated protective film is placed on the first roller 531. The leading edge of the protective film is attached to the second (e.g., take-up) roller 532, with the protective film between the rollers adjacent to the first main surface of the underlying solar product.

[0127] Reference Figure 6In another embodiment, the roll-to-roll system 600 and method include a first (e.g., unwinding) roller 631 and a second (e.g., winding) roller 632. A continuous loop of protective film 650 is conveyed around the solar product 610. Uncontaminated protective film is conveyed from roller 631 across a first primary surface 611 of the solar product 610 by the winding action of roller 632. The winding action of the second roller 632 can be continuous or intermittent. Upon reaching roller 632, contaminated protective film is conveyed beneath the opposite second primary surface 612 of the solar product 610.

[0128] In this embodiment, the contaminated protective film is typically conveyed through a cleaning device 480. Various cleaning devices can be used, including (e.g., spraying) water, brushes, etc. In one embodiment, the cleaning device 680 includes a first roller 681 containing (e.g., a low-tack) pressure-sensitive adhesive for cleaning a first main surface 651 of the protective film 650. The cleaning device 680 optionally includes a second roller 682 containing (e.g., a low-tack) pressure-sensitive adhesive for cleaning a second main surface 652 of the protective film 650. Rollers 681 and optionally 682 can be part of a roll-to-roll system in which the protective film is cleaned using a pressure-sensitive adhesive-coated film, and then... Figure 5 The protective film is replaced in the same manner as described above with a new sheet coated with pressure-sensitive adhesive. Alternatively, rollers 681 and optionally 682 may comprise a roll of pressure-sensitive adhesive-coated film with notches (similar to lint rollers) that facilitate the easy peeling of individual sheets from the roll. The same sheet of pressure-sensitive adhesive-coated film can be reused to clean the protective film until it is no longer effective at cleaning it. The pressure-sensitive adhesive-coated film may also include a tab to facilitate the removal of individual sheets by a person or robot.

[0129] As mentioned earlier, the cleaning effect can be monitored in response to data on the performance of solar products (such as power output) or by sensors that monitor the transparency of the protective film.

[0130] Although the roll-to-roll systems 500, 600 and the method are depicted in a horizontal arrangement, in typical applications, the solar panel and the protective film system are at an angle relative to the sun. For example, the solar panel can be positioned at an angle ranging from 5 to 90 degrees relative to a Cartesian coordinate system with a horizontal x-axis and a vertical y-axis. When the solar panel and the protective film system are at an angle, the system can also be used for snow removal. Furthermore, the first (e.g., unwinding) roller 431 and the second (e.g., rewinding) roller 432 can be equipped with mechanisms that allow adjustment of the roller positions. For example, it may be advantageous to raise the rollers above the solar panel when conveying the protective film to avoid dragging the protective film across the surface of the solar panel. Alternatively, it may be advantageous to position the rollers (531, 532, 631, 632) slightly below the first main surface (511, 611) of the solar panel to bring the protective film close and in tight contact with the first main surface (510, 610) of the solar panel.

[0131] Examples

[0132] Test methods

[0133] 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.

[0134] FTIR testing method from 3300 nm to 25000 nm. Transmission data from 3300 nm to 25000 nm were measured using a Nicolett iS50 FTIR spectrophotometer purchased from Thermo Fisher Scientific, according to the method described in ASTM E1421.

[0135] A polyolefin membrane with a structured surface was prepared, which has the properties according to... Figure 3 The structured surface was used. LDPE 955I, purchased from Dow Chemical, was extruded onto a replica casting roll manufactured using a diamond turning (DTM) method. LDPE 955I reportedly has a density of 0.923 g / cc and a melt flow index of 35 g / 10 min. The casting roll has...Figure 3 A negative replica of the depicted structured surface. LDPE 955I was extruded at a rate of 40.8 kg / h onto an extrusion replica casting roll with a surface temperature of 82.2 °C and a speed of 12.2 m / min. A pressure of 4136.9 kPa was applied to the extrusion replica casting roll tool when the LDPE polymer melt curtain contacted it with a matte rubber pressure roller. (Relative to...) Figure 3 The dimensions of the icons in the attached image are as follows: Nanostructured microspaces 340 = 250nm 346 = 178.6nm B = 70 degrees

[0136] Nanostructured micropeaks

[0137] 340 = 250nm

[0138] 346 = 118.5nm

[0139] B = 70 degrees

[0140] Micropeaks

[0141] 242 = 150 micrometers

[0142] 244 = 80 micrometers

[0143] 246 = 80 micrometers

[0144] A = 53.13 degrees

[0145] Transmittance results

[0146] The transmittance of structured LDPE films and unstructured LDPE films was compared using the above test methods.

[0147] The transmittance results are as follows: For wavelengths in the range of 0.25 micrometers to 0.26 micrometers, the transmittance of both structured and unstructured films is at least 94%, 95%, 96%, 97%, 98%, or 99%, and for this wavelength range, the percentage transmittance of the structured LDPE film is 1% to 2% higher than that of the unstructured film.

[0148] For wavelengths ranging from 0.26 micrometers to 2.40 micrometers, the transmittance of both structured and unstructured films is at least 95%, 96%, 97%, or 98%, and for this wavelength range, the percentage transmittance of the structured LDPE film is 3% to 4.5% higher than that of the unstructured film.

[0149] For wavelengths in the range of 2.40 micrometers to 3.31 micrometers, the transmittance of both structured and unstructured films is at least 95%, 96%, 97%, or 98%, and the percentage transmittance of structured LDPE films is 1% to 2% higher than that of unstructured films.

[0150] For wavelengths in the range of 3.31 μm to 3.44 μm, unstructured LDPE films have a transmittance of at least 95%, 96%, or 97%. Structured LDPE films have a lower percentage transmittance than unstructured films. For a wavelength of 3.36 μm, the minimum value is 9%. Unstructured LDPE has a transmittance of approximately 96% for a wavelength of 3.36 μm.

[0151] For wavelengths in the range of 3.44 micrometers to 3.54 micrometers, the transmittance of both structured and unstructured LDPE films is at least 95%, 96%, 97%, or 98%, and the difference in percentage transmittance between the two films is less than 1%.

[0152] For wavelengths ranging from 3.54 μm to 25.00 μm, the transmittance of both structured and unstructured films is at least 95%, 96%, 97%, or 98%. Within this wavelength range, the percentage transmittance of structured LDPE films is 1% to 2% higher than that of unstructured films.

[0153] Overall, structured films have higher transmittance because the solar radiation intensity in the 3.31-micron to 3.44-micron band is lower compared to the other bands.

[0154] Due to their higher transmittance, structured protective films will improve the efficiency of solar energy products compared to unstructured protective films.

Claims

1. A system comprising: A solar energy product having a first main surface facing the sun and an opposing second main surface during daytime use; A protective film having a first main surface facing the sun and an opposing second main surface during daytime use; The first main surface of the solar cell and / or the opposing second main surface of the protective film include a structure having at least two dimensions less than 1 mm, and the structure provides an air interface between the first main surface of the solar cell and the second main surface of the protective film.

2. The system of claim 1, wherein the second main surface of the protective film is not bonded to the first main surface of the solar cell by chemical, thermal or adhesive means.

3. The system according to claims 1 to 2, wherein the protective film is attached to the solar cell by electrostatic energy, vacuum, mechanical components or a combination thereof.

4. The system according to claims 1 to 3, wherein the first main surface of the solar cell includes the structure.

5. The system according to claims 1 to 4, wherein the second main surface of the protective film includes the structure.

6. The system according to claims 1 to 5, wherein the first main surface of the protective film further includes a structure.

7. The system according to claims 1 to 6, wherein the structure comprises a microstructure, a nanostructure, or a combination thereof.

8. The system according to claims 1 to 7, wherein the structure comprises a peak structure having an apex angle in the range of 20 degrees to 120 degrees.

9. The system according to claims 1 to 8, wherein the structure comprises a nanostructure.

10. The system according to claims 1 to 9, wherein the protective film has one or more of the following properties: i) For wavelengths greater than 0.75 micrometers (750 nm) to 3.3 micrometers (3300 nm), the transmittance is at least 95%, 96%, 97%, 98% or 99%; ii) The transmittance is at least 95%, 96%, 97%, 98% or 99% at wavelengths ranging from greater than 3.6 micrometers (3600 nm) to 25.0 micrometers (25000 nm); iii) wherein the protective film includes the structure, and for wavelengths in the range of 0.75 micrometers to 3.3 micrometers, or for wavelengths in the range of 3.6 micrometers to 25.0 micrometers, the transmittance of the protective film is at least 1%, 2%, 3%, 4%, or 5% higher than that of the same protective film lacking the structure.

11. The system according to claims 1 to 10, wherein the solar energy product is a photovoltaic module.

12. The system according to claims 1 to 11, wherein the protective film comprises a polyolefin material.

13. The system according to claims 1 to 12, wherein the solar energy product is a passive radiative cooling heat transfer plate.

14. The system according to claims 1 to 12, wherein the solar energy product is a cooling film.

15. The system according to claims 1 to 14, wherein the solar cell comprises a multilayer film.

16. The system according to claims 14 to 15, wherein the cooling film is a microporous composite cooling film, or a non-porous cooling film comprising an organic polymer film and inorganic reflective particles.

17. The system according to claims 1 to 16, wherein the multilayer film is free of fluorinated materials.

18. The system according to claims 1 to 17, wherein the protective film is conveyed on the first main surface of the solar product via a roll-to-roll device.

19. The system of claims 1 to 18, wherein the system further comprises means for cleaning at least a first primary surface and optionally a relative primary surface of the protective film.

20. The system of claim 19, wherein the cleaning device comprises a pressure-sensitive adhesive located on the roll.

21. The system according to claims 19 to 20, the system further comprising delivering a cleaned protective film onto the main surface of the solar cell.

22. A structured polyolefin film, said structured polyolefin film being suitable for use as a protective film for solar products according to claims 6 to 10.

23. A method for improving the efficiency of a solar energy product, the method comprising: A solar energy product is provided, the solar energy product having a first main surface facing the sun and an opposing second main surface during daytime use; A protective film is provided, the protective film having a first main surface facing the sun and an opposing second main surface during daytime use; in The protective film is adjacent to the first main surface of the solar cell product; and The first main surface of the solar cell and / or the opposing second main surface of the protective film include a structure having at least two dimensions less than 1 mm, and the structure provides an air interface between the first main surface of the solar cell and the second main surface of the protective film.

24. The method of claim 23, wherein the method is further characterized by claims 2 to 22.

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