A reverse differential optical path photothermal multiplexing device based on sub-bands

Abstract

The present application provides a photothermal multiplexing device based on a sub-band reverse differential optical path. The device includes, but is not limited to: a sub-band reverse differential optical path component, a mid-infrared radiation cooler, and a solar light converter. The sub-band reverse differential optical path component is placed above the mid-infrared radiation cooler and the solar light converter, and is suspended using a bracket to avoid heat conduction caused by contact with the components below; there is a cavity between the mid-infrared radiation cooler and the solar light converter below. The cavity is provided to prevent heat conduction between the two. Such a design realizes the simultaneous and efficient utilization of the solar energy heat source and the cold source of radiation cooling.

Description

Technical Field

[0001] This application belongs to the fields of optics and thermology, and relates to a photothermal multiplexing device based on a reverse different light way by wavelength band. Background Art

[0002] Radiative cooling is a cooling method that uses the intrinsic thermal radiation of an object to lower the object's temperature below the ambient temperature without any energy input. Any object with a temperature higher than absolute zero will spontaneously emit electromagnetic radiation to the outside world. Due to its environmentally friendly zero-emission characteristics, it has been a research hotspot in recent years.

[0003] The realization of radiative cooling technology requires two basic requirements:

[0004] (1) The radiative cooling film needs to have a reflectivity close to 1 for the solar energy band (300 nm - 2500 nm).

[0005] (2) The radiative cooling film needs to have an emissivity close to 1 in the atmospheric window band (8 μm - 14 μm).

[0006] In practice, it can be made into a cooling film. For example, in a Chinese utility model patent with the publication number CN209685670U and the title "A Reflective Radiative Cooling Film", a reflective radiative cooling film is disclosed, which includes a coating layer, a metal layer, a transparent polyester PET layer, an adhesive, and a release protective film arranged in sequence. The coating layer includes an organic acrylic coating and micron spheres. There are many technical solutions for radiative cooling, but they all have technical shortcomings such as complex design, difficult preparation, high cost, easy to cause light pollution, and low efficiency.

[0007] For example, in a Chinese invention patent with the publication number CN105241081B and the title "Compound Parabolic Concentrating Heat Collector with Daytime Heat Collection and Nighttime Radiative Cooling Functions", a compound parabolic concentrating heat collector with daytime heat collection and nighttime radiative cooling functions is disclosed, which includes a box body with an open top, a compound parabolic concentrator, a glass tube, and a bracket. The inner shape of the box body is a compound parabola. The bracket is arranged around the box body. The compound parabolic concentrator is arranged inside the box body. The glass tube is arranged along the bottom center of the compound parabolic concentrator. The two ends of the glass tube are respectively set as a water inlet and a water outlet. The water inlet and the water outlet both communicate with the outer surface of the box body. The outer surface of the glass tube is coated with a solar heat collection and radiative cooling composite coating. This device can only utilize solar energy and radiative cooling in different time periods and cannot be carried out simultaneously.

[0008] For another example, in a Chinese invention patent with the publication number CN110138277B and the title "A thermoelectric power generation device based on radiative cooling and efficient solar energy absorption", a device that relies on solar energy and blackbody radiative cooling to form a temperature difference and then generate electricity is disclosed. It includes a carbon nanoparticle thin film, a semiconductor thermoelectric power generation sheet assembly, a radiative cooling thin film, support columns arranged below the semiconductor thermoelectric power generation sheet assembly, and a reflective concentrator that reflects sunlight onto the lower surface of the carbon nanoparticle thin film. The semiconductor thermoelectric power generation sheet assembly includes an upper insulating heat conducting plate I, a semiconductor thermoelectric device, and a lower insulating heat conducting plate II arranged in sequence from top to bottom; a load and a data acquisition instrument are connected in sequence between both ends of the semiconductor thermoelectric device; the radiative cooling thin film is attached to the upper surface of the upper insulating heat conducting plate I, and the carbon nanoparticle thin film is attached to the lower surface of the lower insulating heat conducting plate II. The radiative cooling end of this device exchanges heat radiation with outer space, thereby reaching a lower temperature, which can be more than ten degrees lower than the ambient temperature, causing a large temperature difference and voltage at both ends of the semiconductor thermoelectric device, and solving the problem of the small heat exchange amount per unit time between the traditional heat sink and the environment. In this way, although the thermoelectric generator realizes the utilization of both solar energy and the "cold energy" of radiative cooling, however, the efficiency of the radiative cooling thin film is low, and the large-angle thermal radiation emitted by radiative cooling cannot smoothly pass through the atmosphere, so the contribution to the radiative cooling power is very small.

[0009] A scheme of combined utilization of radiative cooling and solar energy can also be used: For example, the article "Radiative cooling of solar cells" published in Optica in 2014 introduced a solar panel prepared using a three-dimensional silica photonic crystal. The panel can enhance the emissivity of the infrared atmospheric window on the surface while ensuring the light absorption of the solar cell, thereby reducing the operating temperature of the solar cell, improving the operating efficiency of the solar cell, and extending the lifespan of the solar cell. Although the temperature of the solar cell in this scheme is lower than that without the radiative cooling thin film, however, the overall temperature is still higher than the ambient temperature, and the application scenario is limited.

[0010] Generally speaking, the above-listed schemes have the following problems:

[0011] 1) In traditional solar energy and radiative cooling multiplexing schemes, solar energy and radiative cooling can only be utilized in different time periods. For example, they can only be utilized separately during the day and at night, and cannot be carried out simultaneously, resulting in low energy conversion efficiency.

[0012] 2) There are technical shortcomings such as complex design, difficult preparation, high cost, easy to cause light pollution, and low efficiency.

[0013] 3) It is difficult to be well applied in scenarios such as solar cells.

[0014] 4) There is an issue with the emission angle of the radiative cooling film. The cooling efficiency is low at large emission angles, and the large-angle thermal radiation emitted by radiative cooling cannot pass through the atmosphere smoothly, thus contributing little to the radiative cooling power. Summary of the Invention

[0015] To overcome the above defects, the purpose of this application is to solve the problem that in traditional solar energy and radiative cooling multiplexing schemes, it is impossible to simultaneously use the solar heat source and the infrared radiative cooling cold source through a device.

[0016] To achieve the above purpose, the technical solution adopted in this application is:

[0017] A wavelength-band-based reverse differential optical path photothermal multiplexing device, characterized by comprising:

[0018] A wavelength-band reverse differential optical path element, a mid-infrared radiative cooler, and a solar light converter,

[0019] The wavelength-band reverse differential optical path element is disposed above the mid-infrared radiative cooler and the solar light converter, and is used to converge and focus the incident sunlight-band electromagnetic wave and the mid-infrared-band electromagnetic wave emitted by the mid-infrared radiative cooler.

[0020] A cavity is provided between the mid-infrared radiative cooler and the solar light converter. The cavity is provided to prevent heat conduction between the two. Such a design realizes the simultaneous and efficient utilization of the solar heat source and the cold source of radiative cooling.

[0021] Preferably, the wavelength-band-based reverse differential optical path photothermal multiplexing device is characterized by further comprising:

[0022] A bracket, which is used to fix the wavelength-band reverse differential optical path element so that it does not contact the mid-infrared radiative cooler and the solar light converter.

[0023] Preferably, the wavelength-band reverse differential optical path element is spherical, or,

[0024] The wavelength-band reverse differential optical path element has an aspherical semi-enclosed structure.

[0025] Preferably, the overall area of the solar light converter is smaller than the area of the mid-infrared radiative cooler, and the solar light converter is disposed in the central area of the mid-infrared radiative cooler. When the area of the mid-infrared radiative cooler is known, the cross-sectional area of the cavity is about 10% - 20% of the area of the mid-infrared radiative cooler.

[0026] Preferably, the wavelength-band reverse differential optical path element includes two optical surfaces, an inner side and an outer side,

[0027] When sunlight propagates from the outside to the inside, the optical path is different from that of infrared light propagating from the inside to the outside.

[0028] Preferably, the material of the wavelength-band reverse-difference optical path element is selected from at least one of zinc selenide, polyethylene, hafnium oxide, barium fluoride or a combination thereof.

[0029] Preferably, the wavelength-band reverse-difference optical path element is selected from a common lens, a Fresnel lens or a meta-lens with a micro-nano structure.

[0030] Preferably, the wavelength-band reverse-difference optical path element has a certain transmittance in the full wavelength band and has optical power in both the solar wavelength band and the mid-infrared wavelength band.

[0031] Preferably, the meta-lens includes: a meta-surface with a micro-nano structure, and the meta-surface includes: a substrate, one side of the substrate is configured with an upper surface, and the upper surface is used to converge and focus the incident electromagnetic wave in the solar wavelength band. The other side opposite to the upper surface is configured with a lower surface, and the lower surface is used to converge and focus the mid-infrared electromagnetic wave emitted by the mid-infrared radiation cooler.

[0032] Preferably, the sunlight converter is a solar cell or a solar thermal panel.

[0033] Beneficial effects

[0034] Compared with the prior art, the device in the embodiment of the present application realizes the simultaneous and efficient utilization of the solar heat source and the cold source of radiative cooling through optical design. It greatly simplifies the design process of radiative cooling. The requirement for the reflection performance in the solar spectrum wavelength band is reduced, and only by meeting the condition of high mid-infrared emission can the goal of radiative cooling be achieved. The divergent infrared emission angle is converged by the wavelength-band reverse-difference optical path element, and the path of the mid-infrared electromagnetic wave passing through the atmosphere is shortened, effectively improving the power of radiative cooling. Description of the drawings

[0035] Figure 1 It is a schematic diagram of the wavelength-band based reverse-difference optical path (RDLW) photothermal multiplexing device according to the embodiment of the present application;

[0036] Figure 2 Schematic diagram of the photothermal multiplexing device using an infrared lens according to the embodiment of the present application;

[0037] Figure 3 Schematic diagram of the photothermal multiplexing device using a meta-surface structure according to the embodiment of the present application;

[0038] Figure 4 Schematic diagram of the meta-surface structure according to the embodiment of the present application;

[0039] Figure 5Schematic diagram of the bottom cross-section of the photothermal multiplexing device according to the embodiment of the present application;

[0040] Among them, in the drawings: 1. Band-separated reverse differential optical path element, 2. Mid-infrared radiation cooler, 3. Solar light converter, 4. Cavity, 5. Mid-infrared electromagnetic wave emitted by the mid-infrared radiation cooler, 6. Electromagnetic wave in the solar band, 7. Infrared lens, 8. Bracket, 9. Metasurface, 10. Upper surface of the metasurface, 11. Substrate, 12. Lower surface of the metasurface. Detailed implementation manners

[0041] The above solution will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are for illustrating the present application and not for limiting the scope of the present application. The implementation conditions adopted in the embodiments can be further adjusted according to the conditions of specific manufacturers, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0042] The present application provides a band-separated reverse differential optical path photothermal multiplexing device, which includes: a band-separated reverse differential optical path element, a mid-infrared radiation cooler, and a solar light converter. The band-separated reverse differential optical path element is placed above the mid-infrared radiation cooler and the solar light converter, and is suspended by a bracket to avoid heat conduction caused by contact with the components below; there is a cavity between the lower mid-infrared radiation cooler and the solar light converter to prevent heat conduction between the two. The band-separated reverse differential optical path element can be spherical in shape or can be designed into an aspherical semi-enclosed structure according to requirements. The band-separated reverse differential optical path element is divided into two optical surfaces, an inner side and an outer side. The optical path when sunlight propagates from the outer side to the inner side is different from the optical path when infrared light propagates from the inner side to the outer side. Such an element is called a band-separated reverse differential optical path element. The material of the element can be selected from at least one of zinc selenide, polyethylene, hafnium oxide, barium fluoride or a combination thereof. The type of the element can be an ordinary lens, a Fresnel lens, or a superlens with a micro-nano structure, having a certain transmittance in the full band and having optical power in two bands (solar band and mid-infrared band).

[0043] The solar light converter is an element that converts solar energy into heat energy or electrical energy, mainly a solar cell or a solar thermal panel.

[0044] The solar light converter is arranged at the center of the mid-infrared radiation cooler. The area of the solar light converter must cover the solar focus of the band-separated reverse differential optical path element, and the overall area is relatively small. The mid-infrared radiation cooler occupies a relatively large overall area; the mid-infrared radiation cooler, as an element that converts heat energy into infrared light, radiates its own heat to outer space in the form of electromagnetic waves through the atmospheric transparent window, so that its temperature is lower than the ambient temperature.

[0045] The semi - enclosed structure's band - separated reverse - differential optical path element completely covers the area above the photothermal combination element. It is fixed between them through brackets or other means, and there is a small gap between the two to prevent direct heat conduction. This element has an important feature that it has optical power for both mid - infrared and solar - band electromagnetic waves and has a certain transmittance, enabling electromagnetic waves in these two bands to penetrate the material. The parallel incident sunlight passes through the band - separated reverse - differential optical path element and is focused on the sunlight converter, converging the original sunlight and focusing it on a smaller area of the solar energy conversion element, and converting solar energy into other forms of energy for output. For the mid - infrared radiative cooler on the periphery, due to its relatively high mid - infrared emissivity, the infrared radiation in all directions emitted will be collimated and converged within a very small solid angle through the band - separated reverse - differential optical path element, so that all thermal radiation can smoothly pass through the atmospheric window, ultimately enhancing the radiative cooling effect.

[0046] It is particularly worth noting that since all the sunlight passing through the band - separated reverse - differential optical path element is concentrated in the area of the sunlight converter, there is basically no solar energy on the mid - infrared radiative cooler. Therefore, the design requirement of low solar - band absorptivity for the mid - infrared radiative cooler can be greatly simplified because the mid - infrared radiative cooler does not need to shield solar energy. The upper band - separated reverse - differential optical path element has already transferred the original solar energy, and only needs to achieve the goal of high emission in the infrared atmospheric window band. This greatly simplifies the preparation of the mid - infrared radiative cooler and does not reduce the radiative cooling effect.

[0047] Next, the photothermal multiplexing device proposed in the embodiments of the present application will be described with reference to the accompanying drawings.

[0048] As Figure 1 shown is a schematic diagram of a photothermal multiplexing device based on a band - separated reverse - differential optical path.

[0049] The device includes:

[0050] A band - separated reverse - differential optical path element 1, a mid - infrared radiative cooler 2, and a sunlight converter 3.

[0051] The band - separated reverse - differential optical path element 1 is placed above the mid - infrared radiative cooler 2 and the sunlight converter 3, and is suspended by a bracket 8 to avoid heat conduction in contact with the components below. There is a cavity 4 between the mid - infrared radiative cooler 2 and the sunlight converter 3 on the lower side of the band - separated reverse - differential optical path element 1, and this cavity 4 prevents heat conduction between the mid - infrared radiative cooler 2 and the sunlight converter 3. In this embodiment, the bracket 8 is based on not contacting the bottom mid - infrared radiative cooler 2 and preventing heat conduction.

[0052] As a variation of the above-described embodiment, an infrared lens 7 is used to achieve angular control of two bands.

[0053] After the multiplexing device is placed on the object to be cooled, the electromagnetic wave 6 in the solar band that is incident parallel from the outside irradiates the device. Through the focusing and beam-collecting ability of the lens 2, the light in the solar band is focused within a smaller range, that is, focused on the position of the mid-infrared radiative cooler 2 in the lower component. This part of the solar energy can be used to collect thermal energy for supply, or electrical energy can be collected through a solar panel.

[0054] After the thermal energy generated by the object to be cooled is transferred to the mid-infrared radiative cooler 2, due to the strong emission ability of the mid-infrared radiative cooler itself in the mid-infrared range, the thermal energy is converted into mid-infrared electromagnetic waves and transmitted to outer space through the atmospheric window. In this embodiment, the lens is made of infrared material and can play a certain role in beam-collecting the emission angle of the radiator with anisotropy itself. The angular beam-collection can make the mid-infrared electromagnetic waves propagate to space in the atmospheric window in a direct form as much as possible, reducing the blockage of clouds, thereby maximizing the efficiency of radiative cooling. The distance between the infrared lens 7 and the lower mid-infrared radiative cooler 2 and the cavity 4 is based on the optimal focal length of the lens. The distance between the mid-infrared radiative cooler 2 and the cavity 4 is such that they do not touch to prevent heat conduction.

[0055] As Figure 1 a variation of the embodiment, as shown in Figure 3 and Figure 4 : For the wavelength-division-based reverse differential light path (RDLW) photothermal multiplexing device, a metasurface 9 is used to replace the infrared lens 7. Since Figure 1 the infrared lens is used in the scheme to beam-collect the electromagnetic waves of two bands, but due to the relatively large wavelength range, it is difficult for the traditional infrared lens focusing form to well control these two bands. Therefore, a metalens (metasurface 9) can be used to replace the infrared lens 7. The metalens is a metasurface with micro-nano structures. The metasurface is a relatively flexible means of controlling electromagnetic waves with a high degree of design freedom to solve the difficult problem of separately beam-collecting the two bands by the traditional lens. The upper surface part of the metasurface beam-collects and focuses the incident electromagnetic waves in the solar band; the lower surface part of the metasurface beam-collects and focuses the mid-infrared electromagnetic waves emitted by the mid-infrared radiative cooler. In this way, the function of beam-focusing the light beam is realized by using the metalens, while meeting the effect of beam-collecting for the two-way and two-band light paths.

[0056] Next, the structure of the (double-sided) metasurface will be described in combination with Figure 4 .

[0057] The metasurface includes: a substrate 11, with an upper surface 10 disposed on one side of the substrate 11 and a lower surface 12 disposed on the opposite side. In this structure, sunlight can first pass through the upper surface 10 of the metasurface from above to the structure below, and by regulating the phase in the solar band, the sunlight can be focused on the solar light converter below; the mid-infrared electromagnetic waves emitted by the mid-infrared radiative cooler below first pass through the lower surface of the metasurface, and the effect of beam convergence of the emission angle is achieved through phase regulation.

[0058] As Figure 5 shown, the bracket 8 supports the wavelength-division reverse-difference optical path element to make it suspended; a cavity 4 is provided between the mid-infrared radiative cooler 2 and the solar light converter 3 to prevent heat conduction between the two.

[0059] The above embodiments are only for illustrating the technical concept and features of the present application, and the purpose is to enable those who are familiar with this technology to understand the content of the present application and implement it accordingly, and it cannot be used to limit the protection scope of the present application. Any equivalent transformation or modification made in accordance with the spirit of the present application should be covered within the protection scope of the present application.

Claims

1. A reverse differential optical path optical thermal multiplexing device based on band division, It is characterized in that include: A sub-band reverse differential optical path element, a mid-infrared radiation refrigerator and a solar light converter, wherein the sub-band reverse differential optical path element is in a spherical shape, or the sub-band reverse differential optical path element is in a non-spherical semi-enclosed structure, The sub-band reverse differential optical path element is arranged on the upper side of the mid-infrared radiation refrigerator and the solar light converter, and is used to converge and focus the incident solar light band electromagnetic waves and the mid-infrared band electromagnetic waves emitted by the mid-infrared radiation refrigerator. The sub-band reverse differential optical path element comprises: two optical surfaces, an inner side and an outer side. The optical path of the sunlight propagating from the outer side to the inner side is different from the optical path of the infrared light propagating from the inner side to the outer side. A cavity is provided between the mid-infrared radiation refrigerator and the solar light converter.

2. The reverse differential optical path optical thermal multiplexing device based on wavelength division as claimed in claim 1, It is characterized in that Also includes: A bracket is used to fix the sub-band reverse differential optical path element and prevent it from contacting the mid-infrared radiation refrigerator and the solar light converter.

3. The reverse differential optical path optical thermal multiplexing device based on wavelength division as claimed in claim 1, It is characterized in that The overall area of ​​the solar light converter is smaller than that of the mid-infrared radiation refrigerator, and the solar light converter is arranged in the central area of ​​the mid-infrared radiation refrigerator.

4. The reverse differential optical path optical thermal multiplexing device based on wavelength division as claimed in claim 1, It is characterized in that The material of the sub-band reverse differential optical path element is selected from at least one of zinc selenide, polyethylene, hafnium oxide, and barium fluoride, or a combination thereof.

5. The reverse differential optical path optical thermal multiplexing device based on wavelength division as claimed in claim 1, It is characterized in that The sub-band reverse differential optical path element is selected from a common lens, a Fresnel lens or a super lens with a micro-nano structure.

6. The reverse differential optical path optical thermal multiplexing device based on wavelength division as claimed in claim 5, It is characterized in that The sub-band reverse differential optical path element has a certain transmittance in the entire band and has optical focal length in both the solar band and the mid-infrared band.

7. The reverse differential optical path optical thermal multiplexing device based on wavelength division as claimed in claim 5, It is characterized in that The superlens comprises: a supersurface having a micro-nano structure, and the supersurface comprises: Base, One side of the base is provided with an upper surface, and the upper surface is used to converge and focus the incident electromagnetic waves in the sunlight band. A lower surface is arranged on the other side of the upper surface, and the lower surface is used to converge and focus the electromagnetic waves in the mid-infrared band emitted by the mid-infrared radiation refrigerator.

8. The reverse differential optical path optical thermal multiplexing device based on wavelength division as claimed in claim 1, It is characterized in that The solar light converter is a solar cell or a solar thermal panel.

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