Simultaneous daytime radiative cooling below ambient temperature and photovoltaic power generation in the same area

Abstract

Embodiments relate to apparatuses, methods, and systems configured to provide simultaneous cooling and power generation. In particular, embodiments relate to a radiative cooling device having a radiative cooler and a solar cell that provides simultaneous daytime radiative cooling below ambient temperature and photovoltaic power generation. In a first aspect, a radiative cooling device can be provided. The radiative cooling device can include a first member. The first member can be visible light transparent. The radiative cooling device can include a solar cell. The solar cell can be located below and spaced apart from the first member. The radiative cooling device can include a second member. The second member can be positioned intermediate the first member and the solar cell. The second member can be visible light transparent and infrared radiation (IR) opaque. The first member and the second member can be configured to transmit sunlight to the solar cell such that the solar cell can generate photovoltaic power.

Description

[0001] Cross-reference to related applications

[0002] This patent application relates to and claims priority to U.S. Provisional Application 63 / 564,807, filed March 13, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments relate to apparatuses, methods, and systems configured to provide simultaneous cooling and power generation. Specifically, the embodiments relate to a radiative cooling device having a radiative cooler and solar cells, which provides simultaneous daytime radiative cooling below ambient temperature and photovoltaic power generation. Background Technology

[0004] Radiative cooling has attracted considerable interest because it utilizes the cold universe as a new renewable resource for a wide range of applications, from passive cooling (e.g., in buildings, textiles, solar cells, and electronic devices) to power generation. Radiative cooling occurs through the Earth's atmosphere at temperatures between 8 and 13 degrees Celsius. The transparent window at a certain wavelength sends thermal radiation into the cold universe to operate. (8-13) At this location, the usable thermal radiation power of the 300K blackbody emitter is 148W / m. 2 Therefore, in order to passively cool to below ambient air temperature during the day when peak cooling loads occur, radiative coolers must have negligible solar radiation absorption. Existing methods for achieving daytime radiative cooling below ambient temperature require the use of structures that reflect almost all sunlight (typically >88%) through the use of multilayers, metamaterials, porous structures, and coatings. Therefore, existing daytime radiative coolers below ambient temperature are incompatible with solar energy harvesting. Summary of the Invention

[0005] The sun and the cold universe are two major scalable and renewable resources, and there is a strong desire to harvest them together to generate electricity and cool below ambient temperature from the same region at the same time. Simultaneous utilization of the cold universe and the sun points to untapped opportunities for harvesting renewable energy at levels impossible to achieve using either resource alone. Simultaneous radiative cooling and solar heating have been achieved by placing an infrared transparent solar absorber on top of a radiative cooler, or by placing a vertically oriented radiative cooler between tilted selective solar absorbers. While this heat can be used for heating applications, converting this low-level heat into electricity is challenging due to the low energy conversion efficiency associated with material limitations. Radiative cooling and solar harvesting have also been implemented asynchronously in the same device. A dual-mode radiative cooling and solar heating device for overall energy savings throughout the year has been demonstrated by actuating the radiative cooling surface in summer and the solar absorption surface in winter. Solar cells are used to achieve radiative cooling at night while generating photovoltaic power during the day. However, at any given time (summer or winter, night or day), only radiative cooling or solar harvesting is active. Therefore, simultaneous passive radiative cooling and photovoltaic power generation below ambient temperature is not believed to have been achieved.

[0006] We have developed a system for simultaneously achieving daytime radiative cooling and photovoltaic power generation below ambient temperature from the same area. The system consists of a visible-light-transparent radiative cooler above the photovoltaic cells, with a visible-light-transparent, infrared-opaque layer in the middle. The radiative cooler can be cooled by 8-13... It strongly emits thermal radiation at a certain wavelength, absorbs sunlight negligibly, and does not directly interact with the photovoltaic cell through radiative heat exchange. Sunlight irradiates the photovoltaic cell by passing through a radiative cooler.

[0007] Our system remarkably demonstrates simultaneous daytime radiative cooling below ambient temperature and substantial electrical power output. By providing separate photovoltaic power output, this system contrasts with many existing studies on simultaneous radiative cooling and solar heating below ambient temperature. We surprisingly found that the total energy savings from simultaneous radiative cooling and photovoltaic power generation can exceed those of bare solar panels by up to 30%. Therefore, our system highlights a significant opportunity to simultaneously harvest solar and cold cosmic energy for renewable energy, at levels exceeding the performance of using only one resource.

[0008] In a first aspect, a radiative cooling device may be provided. The radiative cooling device may include a first component. The first component may be visible-light transparent (e.g., transparent, translucent, clear, etc.). The radiative cooling device may include a solar cell. The solar cell may be located below and spaced apart from the first component. The radiative cooling device may include a second component. The second component may be positioned between the first component and the solar cell. The second component may be visible-light transparent and opaque to infrared radiation (IR). The first and second components may be configured to deliver sunlight to the solar cell, enabling the solar cell to generate photovoltaic power. The first component may be configured to emit IR, enabling the first component to provide a radiative cooling effect.

[0009] In some embodiments, the first component may be a material configured to absorb no more than 10% of sunlight.

[0010] In some embodiments, the first component may also be configured to be 8 to 13 micrometers ( It has an average IR emissivity of 0.83 at wavelengths within the range of 0.83.

[0011] In some embodiments, the first component may include a visible-light-transparent thermal-emitting material. The visible-light-transparent thermal-emitting material may include at least one compound from the group consisting of SiO2, Na2O, CaO, MgO, Al2O3, K2O, and Fe2O3.

[0012] In some embodiments, the visible light transparent thermally emitting material may include less than 0.1% Fe2O3.

[0013] In some embodiments, the thickness of the first component may be in the range of 0.1 to 10 millimeters (mm).

[0014] In some embodiments, the radiative cooling structure may include a radiative cooling device. The radiative cooling structure may also include a first chamber suspended within a second chamber. The first chamber may include a first component. The first chamber may also include a second component. The first chamber may include at least one insulating component. The at least one insulating component can separate the first component from the second component, such that the at least one insulating component, the first component, and the second component can define a cavity. A solar cell may be positioned below and spaced apart from the second component. The solar cell may also be positioned below the first chamber.

[0015] In some embodiments, the first chamber may further include a first support structure. The first chamber may also include a second support structure. The second support structure may extend from the second chamber. The first and second support structures may be configured to suspend the first chamber within the second chamber.

[0016] In some embodiments, the surface of the second chamber may be positioned above and spaced apart from the first member, and may include an aperture.

[0017] In some embodiments, the radiative cooling structure may include a third member. The third member may cover and extend across the aperture. The third member may be visible light transparent.

[0018] In some embodiments, the third component may be configured to prevent ambient air from entering the radiative cooling structure through the aperture.

[0019] In some embodiments, the radiative cooling device may include at least one heat exchange element. The at least one heat exchange element may include a heat transfer fluid. The heat transfer fluid may be configured to exchange heat with a first component, such that the heat transfer fluid can be cooled via a radiative cooling effect. In some embodiments, the heat transfer fluid may be water, a solution, a refrigerant, or other types of heat transfer fluid.

[0020] In some embodiments, the at least one heat exchange element may be at least one tubular conduit.

[0021] In some embodiments, the at least one tubular conduit may be visible light transparent and configured to transmit sunlight.

[0022] In some embodiments, the first member may include at least one channel defined within the first member. A heat transfer fluid may be configured to flow through said at least one channel such that the heat transfer fluid can be cooled via a radiative cooling effect.

[0023] In some embodiments, the radiative cooling device may further include at least one heat exchange element comprising a heat transfer fluid. The at least one heat exchange element may be positioned within the at least one channel of the first component.

[0024] In some embodiments, the at least one channel may further include at least one baffle.

[0025] In a second aspect, a radiative cooling device is provided. The radiative cooling device may include a first component. The first component may be configured to emit infrared radiation (IR), such that the first component can provide a radiative cooling effect. The radiative cooling device may include a solar cell. The solar cell may be located below the first component. The radiative cooling device may include at least one IR reflective component. The at least one IR reflective component may be positioned adjacent to the first component and cover the solar cell. The at least one IR reflective component may be visible light transparent. The at least one IR reflective component may be configured to transmit sunlight to the solar cell, such that the solar cell can generate photovoltaic power.

[0026] In some embodiments, the first component may include at least one heat exchange element. The at least one heat exchange element may include a heat transfer fluid. The heat transfer fluid may be configured to exchange heat with the first component such that the heat transfer fluid may be cooled via a radiative cooling effect. In some embodiments, the heat transfer fluid may include water, may be a refrigerant, or may be another type of heat transfer fluid.

[0027] In some embodiments, the at least one heat exchange element may be at least one tubular conduit.

[0028] In some embodiments, the first member may include at least one channel defined within the first member. A heat transfer fluid may be configured to flow through said at least one channel such that the heat transfer fluid can be cooled via a radiative cooling effect.

[0029] In some embodiments, the radiative cooling device may further include at least one heat exchange element comprising a heat transfer fluid. The at least one heat exchange element may be positioned within the at least one channel of the first component.

[0030] In some embodiments, the at least one channel may further include at least one baffle.

[0031] In some embodiments, the at least one IR reflective member may include a low emissivity coating that is transparent to visible light.

[0032] In some embodiments, the first component may be configured to reflect at least a portion of sunlight.

[0033] In some embodiments, the solar cell may be positioned horizontally. The first member may be positioned vertically such that the first member is positioned perpendicular to the solar cell (e.g., the length or height of the first member may extend in a direction perpendicular to the direction in which the upper surface of the solar cell may extend along its width or length, etc.).

[0034] In some embodiments, at least one IR reflector may be positioned at an angle relative to the first member and the solar cell. The at least one IR reflector may be configured to reflect at least a portion of the IR emitted from the first member in a direction toward the sky (e.g., the length or height of the first member may extend at a preselected angle relative to the upper surface of the solar cell, which may extend along its width or length. The preselected angle may be approximately 45°, between 5° and 75°, or between 10° and 60°, etc.).

[0035] In a third aspect, a method for concurrently cooling a fluid and generating photovoltaic power is provided. The method may include providing a radiative cooling device. The radiative cooling device may include a first component. The first component may be visible-light transparent and thermally emitting. The radiative cooling device may also include a solar cell. The solar cell may be located below and spaced apart from the first component. The radiative cooling device may also include a second component. The second component may be positioned between the first component and the solar cell. The second component may be visible-light transparent. The second component may be IR-opaque. The method may further include flowing a fluid through at least one heat exchange element configured to exchange heat with the first component. The first component may provide a radiative cooling effect. The fluid may be configured to exchange heat with the first component such that the fluid is cooled by the radiative cooling effect. The first and second components may be configured to deliver sunlight to the solar cell such that the solar cell can generate photovoltaic power.

[0036] In some embodiments, the first component may include at least one channel defined within the first component. The at least one heat exchange element may be positioned within the at least one channel of the first component.

[0037] In some embodiments, the at least one heat exchange element may be at least one tubular conduit.

[0038] In some embodiments, the at least one tubular conduit may be visible light transparent and configured to transmit sunlight.

[0039] In a fourth aspect, a method for concurrently cooling a fluid and generating photovoltaic power is provided. The method may include providing a radiative cooling device. The radiative cooling device may include a first component. The first component may be thermally emitting. The radiative cooling device may also include a solar cell. The solar cell may be located below the first component. The radiative cooling device may also include at least one IR reflective component. The at least one IR reflective component may be positioned adjacent to the first component and cover the solar cell. The at least one IR reflective component may be visible light transparent. The method may further include allowing fluid to flow through at least one heat exchange element configured to exchange heat with the first component. The first component may provide a radiative cooling effect. The fluid may be configured to exchange heat with the first component such that the fluid is cooled by the radiative cooling effect. The at least one IR reflective component may be configured to deliver sunlight to the solar cell such that the solar cell can generate photovoltaic power.

[0040] In some embodiments, the first component may include at least one channel defined within the first component. The at least one heat exchange element may be positioned within the at least one channel of the first component.

[0041] In some embodiments, the at least one heat exchange element may be at least one tubular conduit.

[0042] In some embodiments, the first component may also be configured to reflect at least a portion of sunlight.

[0043] In some embodiments, the solar cell may be positioned horizontally. The first component may be positioned vertically, such that the first component is positioned perpendicular to the solar cell.

[0044] In some embodiments, the at least one IR reflector may be positioned at an angle relative to the first component and the solar cell. The at least one IR reflector may be configured to reflect at least a portion of the IR emitted from the first component in a direction toward the sky.

[0045] These and other embodiments will be described in more detail herein and in the accompanying drawings illustrating exemplary embodiments. Therefore, further details, objects, and advantages will become clear as the following description continues of certain currently preferred embodiments of the invention and certain currently preferred methods of practicing the invention. Attached Figure Description

[0046] The above and other objects, aspects, features, advantages, and possible applications of this invention will become clearer from the following more detailed description given in conjunction with the accompanying drawings. Similar reference numerals used in the drawings identify similar components.

[0047] Figure 1 A schematic representation of an exemplary embodiment of a radiative cooling device is shown.

[0048] Figure 2 A schematic representation of an exemplary embodiment of a radiation cooling structure including a radiation cooling device is shown.

[0049] Figure 3A A schematic representation of a cross-sectional view of an exemplary first component of a radiative cooling device is shown.

[0050] Figure 3B A schematic representation of a top perspective view of an exemplary first component of a radiative cooling device is shown.

[0051] Figure 4 A schematic representation of an exemplary embodiment of a radiative cooling device is shown.

[0052] Figure 5 This is a flowchart of an exemplary method for concurrently cooling fluids and generating photovoltaic power.

[0053] Figure 6 This is a flowchart of an exemplary method for concurrently cooling fluids and generating photovoltaic power.

[0054] Figure 7 This is a schematic illustration of an exemplary radiative cooling device.

[0055] Figure 8 This is a schematic diagram of a cross-sectional view of the experimental setup for a radiation cooling device.

[0056] Figure 9A -C shows an image of the experimental setup for the radiation cooling device. Figure 9A This is an image of the entire device, in which a transparent radiative cooler is installed inside the chamber, and solar cells are installed below the chamber. Figure 9B It is a top-view photograph of the device. Figure 9C This is a photograph of the bottom view of the device.

[0057] Figure 10 This shows the measured absorptivity of the radiative cooler at an 8° incident angle in the ultraviolet-visible-near IR wavelength range. ) and transmittance ( ) and the absorption rate of PV solar cells ( The figure shows the normalized solar spectrum of AMI.5.

[0058] Figure 11 This is a graph showing the emissivity of a transparent radiative cooler measured at near-normal angles in the mid-infrared wavelength range, averaged across two polarizations. The emissivity and atmospheric transmittance of silicon dioxide are also shown.

[0059] Figure 12A This is a graph showing the temperatures measured in the transparent radiative cooler over four hours around noon. Initially, the metal cover was removed from the chamber, and the solar cells were fully illuminated by the sun. The measured solar irradiance is also shown.

[0060] Figure 12B It is a graph showing the temperature difference between the radiant cooler and the ambient air.

[0061] Figure 13A This is a graph showing the current versus voltage curves of a solar cell at three different times.

[0062] Figure 13B This is a graph showing the performance of a solar cell when it is fully illuminated by the sun during a two-hour period around noon.

[0063] Figure 14A This is a graph showing the temperature difference over time between a cooler with stepped heating and the environment on a clear night. Each shaded area indicates the level of heating applied over 20 minutes. When 87.0 is applied... The temperature difference reaches zero during heating.

[0064] Figure 14B It is a graph showing the applied heating based on the difference between the cooler's steady-state temperature and the ambient air temperature. Linear fitting is also included.

[0065] Figure 15 This is a graph showing the power savings of the system and bare solar cells over 24 hours. Here, the power savings from the radiant cooler are the power saved from an air conditioner operating at a COP of 2.8.

[0066] Figure 16 This is a graph showing the energy savings from passive radiative cooling and photovoltaics, modeled for seventeen cities in different climate zones of the United States. The calculation is based on 3135 m 2 The roof area is assumed to be covered by a dual system of radiative cooling and photovoltaic power generation. The existing cooling system in the building is assumed to have a coefficient of performance of 2.8. Radiative cooling power is considered only if the ambient air temperature exceeds the target indoor temperature of 24°C.

[0067] Figure 17 This is a graphical representation of annual energy savings from radiative cooling across a nationwide simulation. The calculation is based on 3135 m 2 The roof area is assumed to be covered by a dual system of radiative cooling and photovoltaic power generation. The existing cooling system in the building is assumed to have a coefficient of performance of 2.8. Radiative cooling power is considered only if the ambient air temperature exceeds the target indoor temperature of 24°C.

[0068] Figure 18 This is a graphical representation of annual solar power savings simulated across the entire United States. The calculation is based on 3135 m 2 The roof area is assumed to be covered by a dual system of radiative cooling and photovoltaic power generation. The existing cooling system in the building is assumed to have a coefficient of performance of 2.8. Radiative cooling power is considered only if the ambient air temperature exceeds the target indoor temperature of 24°C.

[0069] Figures 19A-19B Images of the spectral and angular emissivity of low-iron glass measured in the mid-infrared wavelength range for P-polarization and S-polarization are shown.

[0070] Figure 20 The low-iron glass and polyimide were shown in the mid-infrared wavelength (5). -25 A graphical representation of the emissivity based on the angle, taken as the average over the angle.

[0071] Figure 21A-C shows an image of a 25cm x 25cm polyimide film insulated heater mounted on a 2mm thick, 1ft x 1ft aluminum thermal diffusion layer.

[0072] Figure 22 This is a graphical representation of an experiment comparing a bare solar cell with an exemplary embodiment of a radiation-cooled device.

[0073] Figure 23 This is a graphical representation of an experiment involving a solar cell, comparing an exemplary embodiment of a bare solar cell with a radiation-cooled device.

[0074] Figure 24 This is a graphical representation of an experiment comparing a bare solar cell with an exemplary embodiment of a radiation-cooled device.

[0075] Figure 25 This is a graphical representation of an experiment involving a solar cell, comparing an exemplary embodiment of a bare solar cell with a radiation-cooled device.

[0076] Figure 26 This is a graphical representation of an experiment comparing a bare solar cell with an exemplary embodiment of a radiation-cooled device.

[0077] Figure 27 This is a graphical representation of an experiment comparing a bare solar cell with an exemplary embodiment of a radiation-cooled device.

[0078] Figure 28 The diagram illustrates the integration of a radiant cooling device with an external cooling system.

[0079] Figure 29 The diagram illustrates the integration of a radiant cooling device with an external cooling system that uses liquid fluid for cooling.

[0080] Figure 30 The illustration shows the 50°C difference between two SiO2 layers under the solar spectrum. Graphical representation of water absorption rate.

[0081] Figure 31 This is a graph showing the energy savings from passive radiative cooling and photovoltaics, modeled for seventeen cities in different climate zones of the United States. Radiative cooling power is considered regardless of ambient air pressure.

[0082] Figure 32 This is a graphical representation of annual energy savings from radiative cooling across a nationwide simulation. Radiative cooling power is considered regardless of ambient air pressure.

[0083] Figure 33 It is a graphical representation of annual electricity savings from photovoltaics across the United States. Detailed Implementation

[0084] The following description relates to exemplary embodiments currently intended for carrying out the invention. This description should not be construed as limiting, but is merely intended to describe the general principles and features of the invention. The scope of the invention is not limited by this description.

[0085] The embodiments generally relate to apparatuses, methods, and systems configured to provide simultaneous radiative cooling and photovoltaic power generation. Specifically, a radiative cooling device may be configured to provide such simultaneous cooling and power generation and may include a first visible-light-transparent component above a solar cell, with a second visible-light-transparent, infrared-opaque component positioned between the first component and the solar cell.

[0086] refer to Figure 1 The radiative cooling device 100 includes a first component 102. The first component 102 may be visible-light transparent and have low or negligible solar absorption, such that at least a portion of sunlight can pass through the first component 102. For example, the first component 102 may be configured to transmit at least a portion of sunlight so that the sunlight can be received by a solar cell 104 below. The first component 102 may also be thermally emissive and configured to emit thermal (e.g., infrared) radiation. Specifically, the first component 102 may be configured to emit thermal radiation through a specific atmospheric window where the Earth's atmosphere is transparent, such that the first component 102 can be passively cooled and provide a cooling effect without the use of electricity. For example, the first component 102 may be a radiative cooler.

[0087] As used herein, the terms infrared, IR, and mid-IR are used interchangeably. Specifically, the term mid-IR can refer to a value greater than 4. And less than 25 The infrared wavelength. Additionally, as used herein, the term sunlight can include visible sunlight, near-IR sunlight (e.g., at 0.7...). and 4 (Sunlight with IR wavelengths) and / or ultraviolet sunlight.

[0088] The first component 102 may be a material configured to be both visible-light transparent (e.g., clear, transparent, translucent, etc.) and thermally reflective. In some embodiments, the first component 102 may be configured to absorb no more than 10% of sunlight and transmit or transfer at least 80% of sunlight. In some embodiments, the first component 102 may be configured to absorb no more than 0.9% of sunlight and transmit or transfer at least 90% of sunlight. The material of the first component 102 may be configured to have a light intensity of 5 to 25 ppm. It has an average IR emissivity of 0.92 at wavelengths within the range. In some embodiments, the material can be configured to have an IR emissivity of 8 to 13. It has an average IR emissivity of at least 0.7 at IR wavelengths within the range. For example, in some embodiments, the material may be configured to have an average IR emissivity of 8 to 13. It has an average IR emissivity of 0.83 at IR wavelengths within the range.

[0089] In some embodiments, the first component 102 may be 8 to 13 The atmospheric transparent window has a material with enhanced IR emissivity. For example, the first component 102 may be a visible light transparent material, such as glass, made primarily of oxides and / or polymers, which has enhanced IR emissivity.

[0090] In some embodiments, the first component 102 may be a visible-light-transparent material. For example, the first component 102 may be a low-iron glass. In some embodiments, the first component 102 may include a material component comprising at least one or a mixture thereof of SiO2, Na2O, CaO, MgO, Al2O3, K2O, or Fe2O3. In some embodiments, the material component may include each of SiO2, Na2O, CaO, MgO, Al2O3, K2O, or Fe2O3. In some embodiments, the material component may include a weight percentage of no more than 0.1% Fe2O3 (e.g., to form a low-iron glass). It should be further understood that the above compounds are merely exemplary, and the material component may include any suitable visible-light-transparent oxides and / or polymers.

[0091] The IR emissivity of SiO2 at atmospheric transparency windows can be enhanced by using multilayers, patterning, antireflective coatings, and / or metamaterials composed of microspheres and polymers. In some embodiments, the first component 102 may include transparent polymers such as polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), and / or polypropylene (PP).

[0092] In some embodiments, the first component 102 may include an anti-reflective coating and / or film to reduce the reflection of sunlight as it passes through the first component 102. It is understood that the materials described above are merely exemplary, and the first component 102 may include components with high transmittance at photon energies above the bandgap of the solar cell 104, and at 8-13... Any suitable visible light transparent material (one or more) with high emissivity at a given wavelength and negligible absorptivity across the entire solar spectrum enables radiative cooling below ambient temperature under direct sunlight.

[0093] In some embodiments, the first component 102 may have a thickness of 2.88 mm. It should be understood that the above thickness is merely exemplary, and the thickness of the first component 102 can be any suitable thickness with low solar absorptivity and high IR emissivity, such that the first component 102 can provide a radiative cooling effect and transfer sunlight to the solar cell 104. For example, in some embodiments, the first component 102 may have a thickness in the range of 0.1 mm to 10 mm.

[0094] In some embodiments, the first component 102 may be configured to operate at 1000 W / m 2 Cooled to 5.1°C below ambient air temperature by light (e.g., sunlight).

[0095] The radiative cooling device 100 also includes a solar cell 104. The solar cell 104 can be any solar cell suitable for generating photovoltaic power. For example, the solar cell 104 can be at least one of a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, a thin-film solar cell, a perovskite solar cell, an organic photovoltaic cell, or a concentrated photovoltaic cell.

[0096] As previously described, the solar cell 104 can be positioned below the first member 102 so that light can pass through the first member 102 and illuminate the solar cell 104.

[0097] The radiative cooling device 100 also includes a second component 106 positioned between the first component 102 and the solar cell 104. The second component 106 may be visible-light transparent, allowing at least a portion of sunlight to pass through both the first component 102 and the second component 106. For example, the first component 102 and the second component 106 may each be configured to transmit at least a portion of sunlight to the downward-facing solar cell 104. The second component 106 may also be IR-opaque, allowing it to transmit no or minimal IR radiation. Accordingly, there may be little or no direct radiative heat exchange between the first component 102 and the solar cell 104.

[0098] In some embodiments, the second component 106 may be a visible-light transparent glass material (e.g., standard soda-lime glass, low-emissivity glass, etc.), polycarbonate, and / or acrylic. In some embodiments, the second component 106 may be a visible-light transparent material having an IR-opaque film and / or coating. In some embodiments, the second component 106 may be the same material as the first component 102. In other embodiments, the second component 106 may include a material different from the material of the first component 102.

[0099] In some embodiments, the second member 106 may be configured at 5 and 25 It absorbs IR at wavelengths between 5 and 25. In some embodiments, the second member 106 can be configured to absorb IR at wavelengths between 5 and 25. The material reflects IR at wavelengths between [wavelength range missing]. It should be understood that the above-described materials are merely exemplary and can be any suitable visible light transparent and IR opaque material, film, and / or coating. In some embodiments, the second component 106 may include an anti-reflective coating and / or film to reduce the reflection of sunlight as it passes through the first component 106.

[0100] refer to Figure 2 In an exemplary embodiment, the radiative cooling device 100 may be part of a radiative cooling structure 108. The radiative cooling structure 108 may include a first chamber 110 suspended within a second chamber 112.

[0101] The first chamber 110 may include a first member 102, a second member 106, and at least one insulating member 114 separating the first member 102 and the second member 106. The insulating member 114, the first member 102, and the second member 106 together may define the cavity of the first chamber 110.

[0102] One or more insulating members 114 may be configured to suppress thermal conduction of the first member 102. One or more insulating members 114 may be formed of any insulating material. In some embodiments, the insulating material may be an insulating foam (e.g., expanded polystyrene (Styrofoam), a closed-cell extruded polystyrene foam (XPS), etc.).

[0103] The first chamber 110 may include a second support structure 118 and a first support structure 116 extending from the second chamber 112, and the first support structure 116 and the second support structure 118 may be configured to support and suspend the first chamber 110 within the second chamber 112. In some embodiments, the first and second support structures 116, 118 may extend from the top wall of the second chamber 112. In some embodiments, the first and second support structures 116, 118 may extend from one or more side walls of the second chamber 112. In some embodiments, the first and second support structures 116, 118 may be spaced apart and define an aperture 120 such that a second member 106 may cover and extend across the first aperture 120.

[0104] In some embodiments, the first and second support structures 116, 118 may be made of a visible light transparent material (e.g., acrylic, transparent plastic, transparent glass, etc.) to transmit sunlight to the solar cell 104 and / or reduce solar heating of the first chamber 110.

[0105] The solar cell 104 may be positioned within the second chamber 112 and below the first chamber 110 (e.g., below and spaced apart from the second member 106).

[0106] In some embodiments, the top wall of the second chamber 112 may include an aperture 122 positioned above and spaced apart from the first member 102. The radiative cooling structure 108 may include a third member 124 covering and extending across the aperture 122. The third member 124 may be configured to prevent ambient air from entering the radiative cooling structure 108 via the aperture 122, and / or to prevent the effects of environmental conditions such as wind.

[0107] In some embodiments, the third component 124 may be a visible light transparent material that allows sunlight and IR to pass through the component, such as polyethylene or other types of transparent materials (e.g., glass). In some embodiments, the third component 124 may include an anti-reflective coating and / or film to reduce the reflection of sunlight as it passes through the third component 124.

[0108] The radiative cooling device 100 may also include a heat transfer fluid configured to exchange heat with the first component 102. For example, the heat transfer fluid may be water or another type of fluid that can exchange heat with the first component 102, such that the heat transfer fluid can be cooled by the radiative cooling effect. The heat transfer fluid may be a gas (such as air or nitrogen) or a liquid (such as water or a refrigerant).

[0109] refer to Figure 3A and Figure 3BThe radiant cooling device 100 may further include at least one heat exchange element 126 configured to deliver a heat transfer fluid. One or more heat exchange elements 126 may be positioned within the first member 102 such that the heat transfer fluid flowing through the heat exchange elements 126 may be configured to exchange heat with the first member 102. Alternatively, or additionally, one or more heat exchange elements 126 may be deployed on a surface (such as an outer surface) of the first member 102 such that the heat transfer fluid flowing through the heat exchange elements 126 may be configured to exchange heat with the first member 102.

[0110] In some embodiments, at least one heat exchange element 126 may be at least one conduit configured to deliver a heat transfer fluid. One or more conduits may be made of a visible light transparent material (e.g., plastic, glass, etc.) and may be configured to deliver sunlight.

[0111] In some embodiments, the first component 102 may include at least one channel 127 positioned within the first component 102, such that a heat transfer fluid can flow through the channel(s) 127 and exchange heat with the first component 102. For example, the channel(s) may include an inlet at one end of the first component 102 and an outlet at the opposite end of the first component 102, and the channel(s) may extend from the inlet to the outlet. In other embodiments, one or more heat exchange elements 126 may be positioned within the channel, such that a heat transfer fluid can flow through the heat exchange elements 126 and exchange heat with the first component 102.

[0112] In some embodiments, the first component 102 may include a first layer and a second layer, and one or more channels 127 may define the space between the first layer and the second layer.

[0113] In some embodiments, one or more channels 127 may include one or more baffles. The baffles may be configured to increase turbulence in the fluid flow and / or enhance heat exchange between the fluid and the first member 102. For example, in some embodiments, one or more channels 127 may form a serrated pattern extending from an inlet at one end of the first member 102 to an outlet at the opposite end of the first member 102.

[0114] refer to Figure 17 and Figure 18A. In some embodiments, the radiant cooling device 100 may be in fluid and / or electrical communication with an external cooling system. For example, the radiant cooling device 100 may be in fluid communication with an external air conditioning system via an inlet duct and / or an outlet duct. The external air conditioning system may be configured to circulate a gaseous fluid (such as air) from a region (e.g., an indoor region) through the radiant cooling device 100 to cool the air, and the cooled air may be recirculated back to the region to cool the region. The external air conditioning system may include a fan configured to transport air from the region to the radiant cooling device 100, such as via an inlet duct in fluid communication with at least one heat exchange element 126. The air may exchange heat with the first component 102, thereby cooling the air to a temperature below ambient.

[0115] In some embodiments, the radiative cooling device 100 may be electrically connected to one or more electrical components of an external air conditioning system, for example via conduits, cables, etc., so that the one or more components can receive electrical energy from the photovoltaic power generated by the solar cell 104. For example, the photovoltaic power generated by the solar cell 104 may be converted into AC or DC power and may be used to power one or more components of the air conditioning system, such as a DC fan.

[0116] In some embodiments, the external air conditioning system may include a refrigerant heat exchanger in fluid communication with the radiant cooling device 100. The refrigerant heat exchanger may be in fluid communication with a pump configured to pump a second heat transfer fluid into the radiant cooling device 100, such as via at least one heat exchange element 126 or via a passage 127 of the first component 102. The second heat transfer fluid may exchange heat with the first component 102, such that the second heat transfer fluid can be cooled to a temperature below ambient.

[0117] The external air conditioning system may also include a refrigeration cycle having, in sequence, an expansion valve, an evaporator, a compressor, and a condenser in fluid communication with a refrigerant heat exchanger. The refrigerant heat exchanger may be configured to exchange heat between a second heat transfer fluid cooled by radiant cooling device 100 and a working fluid (e.g., a refrigerant, such as R-22, R-140A, etc.) flowing through the refrigeration cycle.

[0118] refer to Figure 4 The radiation cooling device 200 may include a first component 202, a solar cell 204 located below the first component 202, and at least one IR reflective component (e.g., component 206, 208) positioned adjacent to the first component 202 and above the solar cell 204 (e.g., covering the solar cell 204).

[0119] The radiative cooling device 200 may be similar to the radiative cooling device 100, such that features shared between similar elements may not be described in detail. For example, the first component 102 and the first component 202 are similar elements, such that features associated with both the first component 102 and the first component 202 may not be repeated for the sake of brevity; the solar cell 104 and the solar cell 204 are similar elements, such that features associated with both the solar cell 104 and the solar cell 204 may not be repeated for the sake of brevity, and so on.

[0120] In some embodiments, the first member 202 may be reflective, such that it reflects sunlight. For example, the first member 202 may be configured to reflect at least 88% of sunlight. In other embodiments, the first member 202 may be visible-light transparent, such that at least a portion of sunlight can pass through it. The first member 202 may also be thermally emissive and configured to emit thermal (e.g., infrared) radiation through a specific atmospheric window where the Earth's atmosphere is transparent, such that the first member 202 can provide a radiative cooling effect to cool to below ambient temperature.

[0121] The radiative cooling device 200 may include at least one IR reflective member. In some embodiments, the radiative cooling device 200 includes one IR reflective member. In some embodiments, the radiative cooling device 200 includes multiple IR reflective members. One or more IR reflective members may be visible light transparent and configured to transmit sunlight to the solar cell 204. One or more IR reflective members 206, 208 may be visible light transparent materials, such as glass, plastic, etc., and may include an IR reflective coating. For example, the IR reflective coating may be a low emissivity coating with an emissivity of less than 10%. In some embodiments, the IR reflective coating may be a multilayer dielectric coating, such as one or more layers of metal (e.g., silver, etc.) deployed between two or more dielectric layers (such as alumina, silicon oxide, etc.). In some embodiments, the IR reflective coating may be a doped metal oxide coating, such as indium tin oxide, gallium zinc oxide, aluminum zinc oxide, etc. It should be understood that the above materials and coatings are merely exemplary, and one or more IR reflective members may include any materials and / or coatings suitable for reflecting IR or thermal radiation and transmitting sunlight.

[0122] In some embodiments, the radiative cooling device 200 may include at least one IR reflective member 206 located on one side of and adjacent to the first member 202 and at least one IR reflective member 208 located on the opposite side of and adjacent to the first member 202.

[0123] In some embodiments, one or more IR reflective members may be positioned adjacent to and covering the solar cell 204, while also being spaced apart from the solar cell 204, and may be configured to reflect IR or thermal radiation emitted from the first member 202 in an upward (e.g., toward the sky) direction. For example, one or more IR reflective members may be positioned at an angle relative to the first member 202 and / or the solar cell 204.

[0124] In an exemplary embodiment, such as Figure 4 As seen in the diagram, the first component 202 can be positioned to cover the solar cell 204. The solar cell 204 can be positioned horizontally and the first component 202 can be positioned vertically, such that the first component 202 is vertically oriented relative to the solar cell 204, and such that the first component 202 is positioned to cover a very small portion of the total surface area of ​​the surface of the solar cell 204. For example, the solar cell 204 can have a first surface 212a and a second surface 212b opposite to the first surface 212a. The first surface 212a can be the solar-absorbing surface of the solar cell 204. The solar cell 204 can be horizontally oriented such that the first surface 212a and the second surface 212b are vertically oriented relative to the solar cell 204. Figure 4 The X-axis shown extends parallel to each other. In some configurations, the X-axis extending from the first and second surfaces can be either the width direction or the length direction of the solar cell 204. The first member 202 may have a first surface 210a and a second surface 210b opposite to the first surface 210a. The first member 202 may be positioned in a vertical orientation such that the first surface 210a and the second surface 210b are relative to each other. Figure 4 The Y-axis is shown to extend parallel to the first surface 210a and the second surface 210b. The first surface 210a and the second surface 210b can be considered to extend along the Y-axis along the height or length direction of the first member 202. In other words, the first surface 212a and the second surface 212b relative to the solar cell 204 can extend along the length or width of the solar cell 204, and the first member 202 can be positioned such that the first surface 210a and the second surface 210b extend perpendicularly along the length or height of the first member 202.

[0125] The first and second IR reflective members 206, 208 can be positioned adjacent to the first member 202 and covering the solar cell 204, and can be configured to reflect IR or thermal radiation emitted from the first member 202 in a direction toward the sky. For example, the first and second IR reflective members 206, 208 can be positioned at an angle relative to the first member 202 and / or the solar cell 204. For example, IR reflective member 206 can have a first surface 214a and a second surface 214b opposite to the first surface 214a, and IR reflective member 208 can have a first surface 216a and a second surface 216b opposite to the first surface 216a. One or more IR reflective members 206 and / or 208 can be oriented such that the first and second surfaces 214a and 214b and / or 216a and 216b can be at an angle ranging from 0° to 90° relative to surfaces 210a and 210b and / or 212a and 212b. Figure 4 The middle is described as (one or more) angles. and / or (This range does not include 0°) extends. For example, one or more IR reflective members 206 and / or 208 may be positioned at an angle such that the first and second surfaces 214a, 214b and / or 216a, 216b are at an angle of 45° relative to the first and second surfaces 210a, 210b and / or relative to the first and second surfaces 212a, 212b (e.g., and / or (Example angle) and / or It may include any suitable angle or range of angles such that (one or more) IR reflectors 206 and / or 208 reflect IR in a direction toward the sky and transmit sunlight to the solar cell 204. For example, the range of angles may include angles from 15° to 75°, 30° to 60°, etc.

[0126] It should be understood that the physical arrangement and / or positioning of the first component 202, the solar cell 204, and the first and second IR reflective components 206, 208 described above are merely exemplary, and each of the first component 202, the solar cell 204, and the first and second IR reflective components 206, 208 can be arranged and / or positioned in any suitable manner such that the first component 202 provides a radiative cooling effect and transmits sunlight to the solar cell 204 to generate photovoltaic power. Furthermore, it should be understood that the radiative cooling device 200 and / or any of its individual components (e.g., the first component 202, the solar cell 204, and the first and second IR reflective components 206, 208) can be positioned in any suitable orientation and / or angle such that IR is reflected by the IR reflective components 206, 208, sunlight is transmitted to the solar cell 204 to generate photovoltaic power, and / or sunlight is reflected by the first component 202.

[0127] The radiative cooling device 200 may also include a heat transfer fluid configured to exchange heat with the first component 202. For example, the heat transfer fluid is configured to exchange heat with the first component 202 such that the heat transfer fluid is cooled by a radiative cooling effect. As described above, the heat transfer fluid may be a gas (such as air) or a liquid (such as water, refrigerant, etc.).

[0128] The radiant cooling device 200 may further include at least one heat exchange element 226 configured to deliver a heat exchange fluid. One or more heat exchange elements 226 may be positioned within the first member 202 such that the heat transfer fluid flowing through the heat exchange elements 226 may be configured to exchange heat with the first member 202. Alternatively or additionally, one or more heat exchange elements 226 may be deployed on a surface (such as an outer surface) of the first member 202 such that the heat transfer fluid flowing through the heat exchange elements 226 may be configured to exchange heat with the first member 202.

[0129] In some embodiments, at least one heat exchange element 226 may be at least one conduit configured to deliver a heat exchange fluid. One or more conduits may be made of a visible light transparent material (e.g., plastic, glass, etc.) and may be configured to transmit sunlight. In some embodiments, one or more conduits may be visible light opaque (e.g., colored plastic, metal, etc.).

[0130] In some embodiments, the first component 202 may include at least one channel located within the first component 202, such that a heat transfer fluid can flow through the channel(s) and exchange heat with the first component 202. For example, the channel(s) may include an inlet at one end of the first component 202 and an outlet at the opposite end of the first component 202, and the channel(s) may extend from the inlet to the outlet. In other embodiments, one or more heat exchange elements 226 may be located within the channel, such that a heat transfer fluid can flow through the heat exchange elements 226 and exchange heat with the first component 202.

[0131] In some embodiments, the channels(s) may include one or more baffles. The baffles may be configured to increase turbulence in the fluid flow and / or enhance heat exchange between the fluid and the first component 202.

[0132] In some embodiments, the radiant cooling device 200 may include at least one heat exchange element 226 and may be fluidly and / or electrically connected to an external cooling system, as described above with respect to the radiant cooling device 100, the details of which may also apply to the radiant cooling device 200 and will not be repeated here for the sake of brevity.

[0133] refer to Figure 5 An exemplary method 300 is provided for concurrently cooling a fluid and generating photovoltaic power. Method 300 can utilize any of the embodiments and / or elements of the radiative cooling device 100 described above for concurrently cooling a fluid and generating photovoltaic power; details are not repeated here for brevity. Method 300 may include a first step 302, providing a radiative cooling device. The radiative cooling device may include a first visible-light-transparent component, a solar cell located below and spaced apart from the first component, and a second component that is visible-light-transparent and IR-opaque, positioned between the first component and the solar cell. Method 300 may include a second step 304, allowing fluid to flow through at least one heat exchange element configured to exchange heat with the first component. The first component can provide a radiative cooling effect, and the fluid can be configured to exchange heat with the first component such that the fluid is cooled by the radiative cooling effect; the first and second components can be configured to deliver sunlight to the solar cell such that the solar cell generates photovoltaic power. The fluid may be a gaseous fluid and / or a liquid fluid.

[0134] refer to Figure 6An exemplary method 400 for concurrently cooling a fluid and generating photovoltaic power is provided. Method 400 can utilize any of the embodiments and / or elements of the radiative cooling device 200 described above for concurrently cooling a fluid and generating photovoltaic power; details are not repeated here for brevity. Method 400 may include a first step 402, providing a radiative cooling device. The radiative cooling device may include a first component, a solar cell located below the first component, and at least one IR reflective component that is visible-light transparent, positioned adjacent to the first component, and covering the solar cell. Method 400 may include a second step 404, allowing fluid to flow through at least one heat exchange element configured to exchange heat with the first component, the first component providing a radiative cooling effect, and the fluid being configured to exchange heat with the first component such that the fluid is cooled by the radiative cooling effect, and the at least one IR reflective component being configured to deliver sunlight to the solar cell such that the solar cell generates photovoltaic power. The fluid may be a gaseous fluid and / or a liquid fluid.

[0135] The embodiments can be configured to include at least one device, such as multiple devices and / or an array of devices. In embodiments including multiple devices, each device can operate independently, such that each device can independently provide cooling and power generation effects.

[0136] In the application, one or more devices may be positioned such that they can receive sunlight. In some embodiments, one or more devices may be positioned and / or angled to better receive sunlight.

[0137] One or more devices may be located on a building (e.g., on the roof of a building), in a site, or anywhere that allows the devices to receive sunlight. In embodiments where the devices are located on a building, it is contemplated that the devices may be configured to provide simultaneous cooling and power to the building.

[0138] The following disclosure discusses exemplary implementations, methods, and test data related to this.

[0139] Example

[0140] Figure 7 The diagram illustrates how our dual-harvest system works. A transparent radiative cooler emits thermal radiation towards the sky. Simultaneously, the transparent radiative cooler allows sunlight to pass through, enabling power generation from the solar cells below.

[0141] At temperature T Net cooling power per unit area of ​​the transparent radiant cooler It can be written as: (1) here, It is the power of the heat radiation emitted by the cooler towards the sky. (2) in It is the angle of incidence. It's the wavelength. It is temperature T The spectral radiance of the blackbody under the given conditions, and It refers to the spectral and angular emissivity of the cooler. It is the power of downward atmospheric thermal radiation absorbed by the cooler. (3) in This refers to the atmospheric spectrum and angular emissivity. Here, Kirchhoff's law of thermal radiation is applied. It is the net radiative heat transfer power from the bottom cover to the cooler. (4) in This indicates the spectral and angular emissivity of the bottom cover. The bottom cover is assumed to be at ambient temperature, which is consistent with our experimental measurements. It is the solar power absorbed by the cooler. (5) in It is the solar irradiance spectrum of AMI.5. It is the non-radiative parasitic heat gain caused by conduction and convection. (6) in It is an effective nonradiative heat exchange coefficient that combines convective and conductive heat exchange between the cooler and its surrounding environment.

[0142] Experimental Design

[0143] According to the energy balance in equation (1), achieving net cooling requires controlling the optical properties across a broad spectrum from ultraviolet to far-infrared and suppressing conduction and convection heat exchange.

[0144] It will have a thickness of 2.8mm and A large-area radiant cooler is installed inside the chamber to suppress non-radiative heat exchange. Figure 8 The radiant cooler is supported by Styrofoam blocks at the four corners to suppress heat conduction between the cooler and the chamber. Its top is covered with a transparent polyethylene film and its bottom with a transparent glass layer to minimize the effects of wind. To reduce solar heating, the chamber walls are made of acrylic. Figure 9C Further installation of side covers to reduce solar heating of the chamber at the walls. Figure 9A Solar cells are installed below the chamber to collect sunlight. Figure 9B During the experiment, the apparatus was tilted 22.5° south to ensure that sunlight shone almost perpendicularly onto it near midday. Solar irradiance was measured using a total radiometer.

[0145] Spectral characterization of radiative coolers and solar cells

[0146] We used low-iron glass as the radiative cooler because it is highly transparent across the entire solar wavelength range and has high emissivity in the mid-infrared. We purchased the low-iron glass from Pilkington. Optiwhite S For the solar cells, we used commercially available Si photovoltaic cells (Maxeon, SunPower) with an area of ​​125mm × 125mm. Spectral measurements showed that the radiative cooler absorbed only 0.9% of sunlight while transmitting 91% of it. Figure 10 In contrast, state-of-the-art solar reflective radiation coolers absorb 1.9%, 3% to 4% of sunlight. Therefore, at 1000... W / m 2 Under solar irradiance, our transparent radiative cooler has 10 less [energy / temperature] compared to the best-achieved solar reflective radiative cooler. W / m 2 Up to 31 W / m 2 The solar cell absorbs sunlight. UV-Vis-NIR spectroscopy measurements show that it strongly absorbs light at wavelengths shorter than 1100 nm. Figure 10 .

[0147] In the mid-infrared wavelength range, spectral measurements show that the transparent radiative cooler has a high emissivity, with an average emissivity of 0.92. Figure 11 Specifically, in 8-13 At the atmospheric transparency window, the average emissivity is 0.83. SiO2 is a typical material used in radiation coolers, attributed to its high emissivity at 9... Phonon polaritons at the location can contribute to thermionic emission. However, for thick SiO2 layers, due to the SiO2 polaritons... 2与 High impedance mismatch between air and air, with an emissivity of 8-13. The area was significantly affected by the decline, and in the 20-25 period The area was affected by a slight decrease. Figure 11 Various photonic methods have been used to enhance the SiO2 content at 8-13°C. Emissivity at atmospheric transparency windows is improved through the use of multilayers, patterning, anti-reflective coatings, and metamaterials composed of microspheres and polymers. Here, we use low-iron glass ( Optiwhite S Pilkington glass is considered an effective metamaterial in the infrared field. The low-iron glass, by weight, consists of 72.7% SiO2, 13% Na2O, 8.8% CaO, 4.3% MgO, 0.6% Al2O3, 0.4% K2O, and 0.02% Fe2O3. The mixing of multiple components broadens the range of SiO2 in the 8-13% range. The frequency response of phonon polaritons at the point of refraction leads to reduced reflection and enhanced emissivity. The low solar absorptivity and high infrared emissivity make low-iron glass suitable for achieving radiative cooling below ambient temperature under direct sunlight.

[0148] Experimental results

[0149] We conducted an outdoor test of the device facing a clear sky near midday at State College, Pennsylvania. Before starting the experiment, we covered the device with an aluminized mylar film to block the path to the sky and the sun. When the experiment began at approximately 11:30 a.m. Eastern Time (ET), we removed the aluminized mylar cover and thus exposed the cooler to the sky while the solar cells were fully illuminated by sunlight. We used thermocouples to measure the temperature of the cooler and the ambient air. Due to passive radiative cooling, the cooler temperature dropped to approximately 5.1°C below the ambient air temperature within 15 minutes. Figure 12A This shows what happens when solar irradiance exceeds 900. W / m 2 The measured temperature of the cooler and the ambient air temperature exceeded three hours. Solar irradiance was approximately 923 pm between 12:00 pm and 3:00 pm ET. W / m 2 Up to 1089 W / m 2 At its peak, the radiant cooler was on average 5.1°C cooler than the ambient air temperature. Figure 12B .

[0150] We also used a source measurement unit to measure the power generation from the solar cells. Figure 13A The current versus voltage curves of the solar cell are shown at three different times. The maximum power generation rate at each time is determined by maximizing the negative value of the product of current and voltage. Figure 13BThe maximum power generation rate measured over time is shown. When characterizing solar cell performance, the solar cell needs to be fully illuminated by sunlight. In our experiment, the solar cell was fully illuminated between 11:30 AM and 1:30 PM ET. During this duration, the solar cell generated 147.2... W / m 2 Up to 159.9 W / m 2 The electrical power between Figure 13B By normalizing the measured power generation rate and measured solar irradiance, the average power conversion efficiency of the solar cells was 14.5%. Our experiment is the first to demonstrate that daytime radiative cooling below ambient temperature and photovoltaic power generation can be achieved simultaneously from the same region.

[0151] Cooling power, another important quality factor used to quantify the performance of radiative cooling, was also carefully measured. We experimentally determined the cooling power that could be extracted from the radiative cooler. The cooling power in equation (1) can be approximated as: (7) here, It is the cooling power that can be extracted from the radiant cooler when it is at the same temperature as the ambient air. It is the total heat exchange coefficient between the radiant cooler and its surrounding environment, including radiative, convective, and conductive heat exchange. Each data point of the cooler temperature represents a steady state, where... Using Equation 7, the ambient cooling power can then be calculated. Determined as .

[0152] To experimentally determine the overall heat transfer coefficient and daytime ambient cooling power, we conducted experiments at night. We mounted the radiant cooler onto a 2mm thick epoxy resin base. On the aluminum thermal diffusion layer, and The polyimide film insulated heater is assembled onto the back of the aluminum layer.

[0153] At night, when no heating is applied, the radiant cooler reaches a temperature 7°C below the ambient air temperature. Figure 14A We then supplied the heater with four levels of stepped Joule heating power, including 21.6 kilojoules each. W / m 2 44.5 W / m 2 65.1 W / m 2 and 87.0 W / m 2 After the increased heating load was applied, the temperature of the radiant cooler rose. Figure 14B The relationship between the heater's heating power and the steady-state temperature of the radiant cooler is shown. When 87.0... W / m 2 When the heating power is set to the ambient air temperature, the radiant cooler stabilizes. Since the heating power balances the ambient cooling power when the cooler stabilizes at the ambient air temperature, the nighttime ambient cooling power is determined to be 87.0. W / m 2 .

[0154] Based on the slope of the linear fit between heating power and temperature decrease ( Figure 14B The total heat exchange coefficient at night was determined to be... The total heat exchange coefficient at night The overall heat exchange coefficient differs from that during the day because the back of the radiant cooler is made of polyimide in the nighttime experiment but low-iron glass in the daytime experiment (see [link]). Figure 20 By taking into account the small difference between the emissivity of low-iron glass and that of polyimide, we determined the total daytime heat exchange coefficient to be... The overall heat transfer coefficient determined experimentally was used. In addition to the daytime temperature reduction, we determined the daytime cooling power of the radiant cooler under ambient air temperature to be: .

[0155] In addition, we compared the power savings of the dual-collection system with those of solar cells without a radiative cooler (hereinafter referred to as...). bare The energy saved by solar cells Figure 15 The energy savings of a bare solar cell are equal to its photovoltaic power generation rate, which is its measured power conversion efficiency. (See) Figure 22-27 The energy savings of the dual system include the electricity generated by the solar cells, as well as the electricity saved from the cooling system through the use of radiative cooling. The solar cells in the dual system have measured... The apparent power conversion efficiency. Figure 15 In the middle, when the solar irradiance exceeds 100 W / m 2 At that time, the radiative cooling power was set to 63.8. W / m 2 Otherwise, it is 87.0. W / m 2 We assume that if this were not the case, the air conditioner would be used as the cooling system, and that it has a coefficient of performance (COP) of 2.8. Figure 15This indicates that bare solar cells generate more power than solar cells in a dual-system. The performance degradation of solar cells in the dual-system is largely due to reflection losses at the glass layer and polyethylene cap. After accounting for the power savings from radiative cooling, when the solar irradiance is below 750... W / m 2 (Including at night) the dual system has a higher combined energy saving rate than bare solar cells.

[0156] The total power savings of the dual-data acquisition system over 24 hours can be evaluated using the following formula: (8) in It is the radiative cooling power. COP =2.8, and This is the solar irradiance measured over a 24-hour period on March 20, 2023. The total power savings of the dual-data acquisition system over 24 hours were assessed at 1.80. kWh / m 2 The energy savings of bare solar cells can be evaluated using the following formula: (9) Its total is 1.38 kWh / m 2 Therefore, for the same area using a day-night cycle, the dual-harvest system saves up to 30% more electricity than bare solar cells.

[0157] Energy-saving potential of the equipment in different geographical and climatic regions

[0158] We estimated the potential energy savings from radiative cooling and photovoltaic power generation simultaneously below ambient temperature for different geographical and climatic regions. In the simulation, we considered a temperature of 3135... m 2 A four-story mid-rise apartment building with a roof area. We assume the roof is covered by a dual system of radiative cooling and photovoltaic cells. When the ambient air temperature exceeds the target indoor temperature of 24°C, we assume the cooling generated by radiative cooling is transferred through physical mechanisms to reduce the electricity consumption of the air conditioning system. The air conditioning system is assumed to have a coefficient of performance (COP) of 2.8. For the solar cells, we consider a power conversion efficiency of 14.5%. According to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHR.AE) and American National Standards Institute (ANSI) Standard 169-2020, there are seventeen different climate zones throughout the United States, based on eight temperature zones (1 (warmest) to 8 (coldest)) and three climate types based on humidity (A (humid), B (dry), and C (oceanic)).

[0159] We used a representative city from each of the seventeen climate zones, including Albuquerque (NM), Atlanta (GA), Baltimore (AID), Bremerton (WA), Chicago (IL), Denver (CO), Duluth (MN), Fairbanks (AK), Helena (MT), Houston (TX), Las Cruces (NM), Las Vegas (NV), Los Angeles (CA), Miami (FL), Minneapolis (MN), Phoenix (AZ), and San Francisco (CA). For each city, we used typical meteorological data (TMY3) to determine ambient temperature, dew point, and solar irradiance. By analyzing the energy savings of these cities, we made estimates for the entire United States. We modeled the ambient cooling power using Equation (1), which uses measured polarization-dependent, angle-dependent, spectral emissivity of the radiative cooler (see [reference]). Figure 19A -B), atmospheric transmittance dependent on dew point from MODTRAN, ambient temperature, and solar irradiance.

[0160] Figure 12A The annual electricity savings of the dual system, achieved through both radiative cooling and solar cells, are shown. This applies to cities with hot and dry climates, such as Phoenix (3.61 × 10⁻⁶). 5 kWh ), Las Vegas (3.14×10 5 kWh ), Las Cruces (2.06×10 5 kWh ) and Albuquerque (0.97×10 5 kWh This demonstrates the high energy saving achieved through radiation cooling. Figure 12B The map shows the same characteristics. Lower humidity in arid climates leads to higher atmospheric transparency, which in turn enhances radiative cooling performance. Moreover, cities with hot and humid climates, such as Miami (2.21 × 10⁻⁶), exhibit similar characteristics. 5 kWh ) and Houston (1.21×10 5 kWh The study demonstrated significant energy savings through radiative cooling. In cities with hot and humid climates, although high humidity reduces the performance of radiative cooling, the energy savings from radiative cooling are significant due to the high ambient temperature and the resulting high cooling demand.

[0161] Finally, in cold climates, the cooling demand for space cooling in buildings decreases, and therefore the potential benefits of radiative cooling are small. Figure 16-18In this study, we only consider the benefits of radiative cooling when the ambient air temperature exceeds the target indoor temperature by 24°C. Since TMY3 data shows that some cities (such as Los Angeles and San Francisco) do not have an average hourly temperature exceeding 24°C throughout the year, we consider this benefit in... Figure 16-8 The energy savings from radiative cooling in these cities were assessed as zero. However, radiative cooling can be useful in scenarios such as data centers, manufacturing, and refrigeration systems, even in cold climates. By taking into account the radiative cooling power at all ambient temperatures, the energy savings from radiative cooling can be orders of magnitude comparable to the energy generated from photovoltaic power generation (see [link to relevant documentation]). Figure 19A -C).

[0162] Photovoltaic power generation primarily relies on solar irradiance. Figure 12C shows that in lower altitude areas, such as Phoenix (9.37 × 10⁻⁶), solar irradiance is significantly higher. 5 kWh ), Las Cruces (9.26×10 5 kWh ), Las Vegas (9.10×10 5 kWh ), Albuquerque (8.87×10 5 kWh ), Los Angeles (8.17×10 5 kWh ) and Miami (7.85×10 5 kWh Solar power can generate more electricity than at higher altitudes. Therefore, dry and hot places, such as Phoenix and Las Vegas, can benefit the most from simultaneous radiative cooling and solar power generation. The enormous potential energy savings from radiative cooling and solar power highlight the great opportunity to simultaneously harness the coldness of the universe and the sun for renewable energy.

[0163] discuss

[0164] We demonstrated that simultaneously at approximately 1000 W / m 2 Under solar irradiance, there is a 5.1°C temperature drop below ambient temperature due to daytime radiative cooling and a temperature drop of up to 159.9°C from the same region. W / m 2 Solar power generation. We experimentally achieved 63.8 [units of energy] under peak sunlight. W / m 2 The ambient cooling power was 87.0 at night. W / m 2The environmental cooling power. Below, we briefly compare the overall performance of the dual system to existing daytime radiative coolers operating below ambient temperature. Assuming the generated photovoltaic power will be used to drive a cooling system with a performance coefficient of 2.8, the total cooling power from our system due to radiative cooling and photovoltaic power under peak sunlight will be 511.5. W / m 2 Its efficiency surpasses that of daytime cooling power achieved in solar reflective radiation coolers (40-100). W / m 2 It is more than 5 times larger than the daytime cooling power achieved in a bifacial radiant cooler (273.3). W / m 2 The energy savings are greater than 1.8 times. Furthermore, during the diurnal cycle, the dual system achieves energy savings exceeding those of bare solar cells by up to 30%. Our results highlight new opportunities for utilizing both the cold universe and the sun for renewable energy.

[0165] One potential application of dual-harvest systems is their integration with buildings to reduce overall energy consumption. The photovoltaic power generated in the dual system can be used for energy storage or converted to AC current using an inverter. The cooling achieved on the transparent radiant cooler can be used to cool air or liquids, which can be driven by fans or pumps respectively, to interface with the thermal system for energy savings (see [link to thermal system]). Figure 28 and Figure 29 In our proof-of-concept demonstration, the achieved photovoltaic conversion efficiency was affected by reflections occurring at multiple interfaces. Photovoltaic conversion efficiency can be improved by adding anti-reflective coatings to the radiative cooler, polyethylene, and chamber bottom cover. Figure 30 This shows the 50°C difference between two SiO2 layers. A graph showing the absorptivity of liquid water modeled under the solar spectrum.

[0166] There is room for further improvement of transparent radiative coolers, including reducing visible light reflection and enhancing infrared emissivity. Materials for transparent radiative coolers need to meet stringent requirements, including high transmittance at photon energies above the bandgap of solar cells and emissivity in the range of 8-13. High emissivity at the specified wavelength and negligible absorptivity across the entire solar spectrum. Transparent radiative coolers can involve transparent polymers such as polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), and polypropylene (PP).

[0167] Furthermore, the performance of a dual-harvest system can depend on several environmental parameters, such as ambient temperature, solar irradiance, and atmospheric transmittance affected by dew point and cloud cover. At a fixed solar irradiance and atmospheric transmittance, ambient cooling power increases with increasing ambient temperature because radiative heat exchange becomes more significant at higher temperatures. Photovoltaic power output decreases with ambient temperature because solar cells typically have a negative temperature coefficient for conversion efficiency. Since both ambient cooling power and photovoltaic power output have inverse coefficients relative to ambient temperature, the sign of the temperature coefficient for the total power savings of the dual-harvest system will depend on the details of the environmental parameters, including solar irradiance, atmospheric transmittance, and ambient temperature. Finally, the duration of time the solar cells are illuminated by the sun is limited by the aspect ratio of the device in the concept demonstration, which can be addressed by increasing the lateral dimensions of the device.

[0168] It should be understood that the disclosure of a value range is a disclosure of every value within that range, including the endpoints. It should also be recognized that some components, features, and / or configurations may be described in conjunction with only one particular embodiment, but these same components, features, and / or configurations may be applied to or used in many other embodiments and should be considered applicable to other embodiments unless otherwise stated or unless such components, features, and / or configurations are technically impossible to use with other embodiments. Therefore, components, features, and / or configurations of various embodiments can be combined in any way, and such combinations are expressly contemplated and disclosed in this statement.

[0169] In light of the foregoing teachings of this disclosure, it will be apparent to those skilled in the art that many modifications and variations are possible to the described examples and embodiments. The disclosed examples and embodiments are presented merely for illustrative purposes. Other alternative embodiments may include some or all of the features disclosed herein. Therefore, it is intended to cover all such modifications and alternative embodiments that may fall within the true scope of the invention, which will be given full breadth.

[0170] It should be understood that modifications can be made to the embodiments disclosed herein to satisfy a particular set of design criteria. Therefore, while certain exemplary embodiments of compositions, materials, devices, and methods of using and manufacturing thereof have been discussed and illustrated herein, it must be clearly understood that the invention is not limited thereto, but can be practiced and implemented in various other ways within the scope of the following claims.

Claims

1. A radiative cooling device, comprising: A first component, wherein the first component is visible light transparent and thermally emitting; A solar cell, which is located below and spaced apart from the first component; A second component, positioned between the first component and the solar cell, is visible-light transparent but opaque to infrared (IR) radiation. The first and second components are configured to transmit sunlight to the solar cell, thereby enabling the solar cell to generate photovoltaic power, and the first component is configured to emit IR, thereby providing a radiative cooling effect.

2. The radiative cooling device of claim 1, wherein the first component comprises a material configured to absorb no more than 10% of sunlight.

3. The radiation cooling device of claim 2, wherein the material is configured to have an average IR emissivity of 0.83 at an IR wavelength in the range of 8 to 13 micrometers.

4. The radiation cooling device of claim 1, wherein the first component comprises a visible light transparent thermal emitting material, said material comprising at least one compound from: SiO2, Na2O, CaO, MgO, Al2O3, K2O and Fe2O3.

5. The radiation cooling device of claim 4, wherein the material that is visible light transparent and thermally emitting comprises less than 0.1% Fe2O3.

6. The radiative cooling device of claim 1, wherein the first component has a thickness in the range of 0.1 to 10 millimeters.

7. A radiation cooling structure comprising the radiation cooling device as described in claim 1, wherein the radiation cooling structure further comprises: A first chamber, suspended within a second chamber, wherein the first chamber comprises: First component; The second component; and At least one insulating member that separates a first member from a second member, such that the at least one insulating member, the first member, and the second member define a cavity; wherein the solar cell is positioned below and spaced apart from the second member.

8. The radiation cooling structure as claimed in claim 7, wherein the first chamber further comprises: A first support structure and a second support structure extending from the second chamber, wherein the first support structure and the second support structure are configured to suspend the first chamber within the second chamber.

9. The radiation cooling structure of claim 7, wherein the surface of the second chamber positioned above and spaced apart from the first member includes apertures.

10. The radiation cooling structure of claim 9, wherein the third member covers and extends across the aperture, and wherein the third member is visible light transparent.

11. The radiative cooling structure of claim 10, wherein the third member is configured to prevent ambient air from entering the radiative cooling structure through the aperture.

12. The radiative cooling device of claim 1, further comprising at least one heat exchange element, the at least one heat exchange element comprising a heat transfer fluid configured to exchange heat with the first component such that the heat transfer fluid is cooled by a radiative cooling effect.

13. The radiative cooling device of claim 12, wherein the at least one heat exchange element comprises at least one tubular conduit.

14. The radiative cooling device of claim 13, wherein the at least one tubular conduit is visible light transparent and configured to transmit sunlight.

15. The radiative cooling apparatus of claim 1, wherein the first component includes at least one channel defined within the first component, and wherein a heat transfer fluid is configured to flow through the at least one channel such that the heat transfer fluid is cooled by a radiative cooling effect.

16. The radiative cooling device of claim 15, further comprising at least one heat exchange element, the at least one heat exchange element comprising a heat transfer fluid, wherein the at least one heat exchange element is positioned within the at least one channel of the first component.

17. The radiation cooling device of claim 15, wherein the at least one channel further comprises at least one baffle.

18. A radiative cooling device, comprising: A first component, wherein the first component is configured to emit infrared radiation (IR) such that the first component provides a radiative cooling effect; A solar cell, located below the first component; At least one IR reflective element is positioned adjacent to and covering the solar cell, wherein the at least one IR reflective element is visible light transparent. The at least one IR reflective element is configured to deliver sunlight to the solar cell, thereby enabling the solar cell to generate photovoltaic power.

19. The radiative cooling apparatus of claim 18, further comprising at least one heat exchange element, the at least one heat exchange element comprising a heat transfer fluid configured to exchange heat with the first component such that the heat transfer fluid is cooled by a radiative cooling effect.

20. The radiative cooling device of claim 19, wherein the at least one heat exchange element comprises at least one tubular conduit.

21. The radiative cooling apparatus of claim 18, wherein the first component includes at least one channel defined within the first component, and wherein a heat transfer fluid is configured to flow through the at least one channel such that the heat transfer fluid is cooled by a radiative cooling effect.

22. The radiative cooling device of claim 21, further comprising at least one heat exchange element, the at least one heat exchange element comprising a heat transfer fluid, wherein the at least one heat exchange element is positioned within the at least one channel of the first component.

23. The radiative cooling device of claim 21, wherein the at least one channel further comprises at least one baffle.

24. The radiation cooling device of claim 18, wherein the at least one IR reflective member comprises a low emissivity coating that is transparent to visible light.

25. The radiative cooling device of claim 18, wherein the first component is further configured to reflect at least a portion of sunlight.

26. The radiative cooling apparatus of claim 18, wherein the solar cell is positioned in a horizontal orientation and wherein the first component is positioned in a vertical orientation such that the first component is positioned vertically relative to the solar cell.

27. The radiation cooling device of claim 26, wherein the at least one IR reflector is positioned at an angle relative to the first member and the solar cell, such that the at least one IR reflector is configured to reflect at least a portion of the IR emitted from the first member in a direction toward the sky.

28. A method for concurrently cooling fluid and generating photovoltaic power, comprising: Provide a radiant cooling device, the radiant cooling device comprising: A first component, wherein the first component is visible light transparent and thermally emitting; Solar cells, the solar cells being below and spaced apart from the first member; and The second component is positioned between the first component and the solar cell. The second component is transparent to visible light but opaque to infrared radiation (IR); and Fluid is passed through at least one heat exchange element configured to exchange heat with a first component, wherein the first component provides a radiative cooling effect, and the fluid is configured to exchange heat with the first component such that the fluid is cooled by the radiative cooling effect. The first and second components are configured to transmit sunlight to the solar cell, enabling the solar cell to generate photovoltaic power.

29. The method of claim 28, wherein the first member includes at least one channel defined within the first member, and wherein the at least one heat exchange element is positioned within the at least one channel of the first member.

30. The method of claim 28, wherein the at least one heat exchange element comprises at least one tubular conduit.

31. The method of claim 30, wherein the at least one tubular conduit is transparent and configured to transmit sunlight.

32. A method for concurrently cooling a fluid and generating photovoltaic power, comprising: Provide radiant cooling equipment, including: A first component, wherein the first component is thermally emitting; Solar cell, the solar cell being located below the first component; and At least one infrared radiation (IR) reflective element, positioned adjacent to and covering the solar cell, wherein the at least one IR reflective element is visible light transparent; and Fluid is passed through at least one heat exchange element configured to exchange heat with a first component, wherein the first component provides a radiative cooling effect, and the fluid is configured to exchange heat with the first component such that the fluid is cooled by the radiative cooling effect. The at least one IR reflective element is configured to deliver sunlight to the solar cell, thereby enabling the solar cell to generate photovoltaic power.

33. The method of claim 32, wherein the first component includes at least one channel defined within the first component, and wherein the at least one heat exchange element is positioned within the at least one channel of the first component.

34. The method of claim 33, wherein the at least one heat exchange element comprises at least one tubular conduit.

35. The method of claim 32, wherein the at least one IR reflective member comprises a low emissivity coating that is transparent to visible light.

36. The method of claim 32, wherein the first component is further configured to reflect at least a portion of sunlight.

37. The method of claim 32, wherein the solar cell is positioned in a horizontal orientation and wherein the first member is positioned in a vertical orientation such that the first member is positioned vertically relative to the solar cell.

38. The method of claim 37, wherein the at least one IR reflector is positioned at an angle relative to the first member and the solar cell, such that the at least one IR reflector is configured to reflect at least a portion of the IR emitted from the first member in a direction toward the sky.

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