A temperature-adaptive surface radiator

Abstract

A temperature-adaptive surface radiator relates to the fields of radiative cooling and solar heating. The temperature-adaptive surface radiator has a layered structure, including a long-wave infrared control layer and a near-infrared control layer. The long-wave infrared control layer can temperature-adaptively adjust the long-wave infrared emissivity (8–14 μm) of the device, automatically turning radiative cooling on / off according to changes in the external temperature. The near-infrared control layer can adjust the near-infrared (0.8–1.3 μm) reflectivity of the device by the number of cycles, utilizing the near-infrared band of solar energy for target heating. This invention provides a solution for achieving the integrated utilization of radiative cooling and solar heating in a single device.

Description

Technical Field

[0001] This invention relates to the fields of infrared spectral modulation, radiative cooling and solar heating, and specifically to a temperature-adaptive surface radiator. Background Technology

[0002] Globally, approximately 30% of final energy consumption is used for heating and cooling in residential and commercial buildings, with an even higher proportion in developed countries. The extensive use of air conditioning and heating equipment is actually related to building materials. Materials with excellent thermal management performance can not only improve the comfort of the space but also help save energy and reduce carbon emissions. Radiative cooling and solar heating are common passive cooling and heating methods for buildings and spaces. Radiative cooling refers to a cooling method where surface materials release heat directly into space through atmospheric windows via infrared radiation. To achieve meaningful radiative cooling, the cooling material must have strong selective radiation in the atmospheric window range (8–14 μm) and extremely high solar reflectivity within the solar spectrum. Solar heating primarily utilizes solar radiation in the 0.15–4 μm wavelength band to provide heat to building spaces, requiring its surface materials to have high absorptivity within the solar spectrum. In summary, surface materials that achieve heating should have radiation characteristics completely opposite to those of cooling materials. Traditional materials have similar emissivity across different wavelengths, meaning they struggle to fully utilize their cooling and heating capabilities. For example, most traditional building exterior surface materials are highly reflective of sunlight, effectively preventing absorption but failing to effectively utilize the sky for infrared cooling. Furthermore, the physical properties of common materials do not change significantly with temperature, resulting in relatively fixed infrared spectra at different temperatures. Therefore, a single surface cannot simultaneously meet both cooling and heating needs under varying external environmental conditions. Summary of the Invention

[0003] To address the challenge of integrating radiative cooling and solar heating under varying environmental conditions with a single surface, this patent proposes a temperature-adaptive surface radiator. This device can passively adjust its heating / cooling mode in response to changes in ambient temperature, providing heating assistance to buildings or targets through infrared cooling and solar heating.

[0004] A temperature-adaptive surface radiator has a layered structure, specifically ABC(BD). n The structure is given by A, B, C, and D, which are the four materials that make up the temperature-adaptive radiator, and n represents (BD). n The number of periods corresponding to the structure.

[0005] Furthermore, in the materials constituting the temperature-adaptive surface radiator, A represents Al, B represents Ge, C represents VO2, and D represents TiO2.

[0006] Furthermore, a temperature-adaptive surface radiator has a specific structure of ABC(BD). n Based on function, they can be divided into ABC structural units and (BD) n Structural units, the specific functions of each structural unit are as follows:

[0007] ABC structural unit: Temperature-adaptive long-wave infrared spectral modulation

[0008] BD structural unit: Near-infrared spectral modulation

[0009] Furthermore, for the ABC structural unit, the physical thicknesses of material layers A, B, and C range from 5 to 50 μm, 0.5 to 1 μm, and 0.01 to 0.03 μm, respectively.

[0010] Furthermore, the thin films of materials A, B, and C in the ABC structural unit were prepared by magnetron sputtering.

[0011] When the ambient temperature is high (above the phase transition temperature of VO2), material B (VO2) has no band gap and is in a metallic state. An FP resonant cavity is formed through the design of ABC structural units, causing specific wavelengths of incident light to resonate and absorb within the cavity. Thickness design allows the temperature-adaptive surface radiator to have high long-wave infrared emissivity, providing radiative cooling capability. When the ambient temperature is low (below the phase transition temperature of VO2), material B transitions to a semiconductor state with a smaller band gap. At this point, materials B and C have high long-wave infrared transmittance, and most of the incident infrared waves are reflected by material A, resulting in lower long-wave infrared emissivity. This disables radiative cooling, achieving temperature adaptability.

[0012] Furthermore, regarding (BD) n The physical thicknesses of structural units, materials B and D, are determined based on their refractive index and the wavelength of any reflection center, respectively. The formula for calculating the physical thickness is as follows:

[0013]

[0014]

[0015] Where, d B n represents the physical thickness of material B. B Let d be the refractive index of material B. D n represents the physical thickness of material D. D Let λ be the refractive index of material D, and λ represent the center wavelength of the reflection spectrum.

[0016] Furthermore, regarding (BD) nThe structural unit has a period number n ranging from 1 to 5. Different number of periods correspond to different near-infrared (0.8 to 1.4 μm) reflectivities. The larger the n, the higher the near-infrared reflectivity of the temperature-adaptive surface radiator.

[0017] Furthermore, (BD) n The material thin films B and D in the structural unit are sequentially sputtered onto the ABC structural unit by magnetron sputtering.

[0018] (BD) n The structural unit is composed of stacked B and D materials with different refractive indices to form a one-dimensional photonic crystal structure, which can achieve the reflection of incident light of a specific wavelength. (BD) n Materials B and D in the structural unit are long-wave infrared transparent materials (BD). n The presence of structural units and the number of their periods have little impact on the long-wave infrared emission performance of the temperature-adaptive surface radiator. (BD) n The control of near-infrared radiation by the structural unit depends on the number of its periods. When the number of periods is large (≥3), it has a high near-infrared reflectivity, which can largely avoid the absorption of sunlight and make full use of the radiative cooling capability of the FP resonant cavity. When the number of periods is small (<2), it has a low near-infrared reflectivity, absorbs solar energy, and, in conjunction with low-temperature shut-off infrared cooling, achieves solar heating.

[0019] In summary, the temperature-adaptive surface radiator combines a FP resonant cavity structure with selective emission capabilities and a one-dimensional photonic crystal structure with selective reflection capabilities, forming ABC(BD). n The structure consists of a substrate of material A, on which layers B and C are sequentially sputtered. These layers, together with material A, form a photonic resonant cavity (FP cavity). This fully utilizes the thermochromic capability of material C, achieving a positive correlation between its atmospheric window infrared emissivity and the substrate's properties. This enables temperature-adaptive infrared cooling on / off capabilities. The outer thin film is a periodic one-dimensional photonic crystal material formed by sequential sputtering of layers B and D. This allows for the adjustment of the intrinsic absorption of VO2 in the near-infrared band without affecting the radiation characteristics of the lower atmospheric window. Near-infrared reflectivity is controlled by selecting the number of periods, and combined with the FP cavity, effective near / far-infrared dual-band control is achieved under both high and low temperature conditions.

[0020] The beneficial effects of this invention are: it achieves control over near-infrared reflection and long-wave infrared emissivity on a single surface, wherein the long-wave infrared emissivity can be adaptively adjusted by ambient temperature, while the near-infrared reflectivity is modulated on demand through structural adjustments. This invention enables the comprehensive utilization of sky radiation cooling and solar thermal energy, exhibiting superior cooling / heating capabilities compared to conventional materials. Attached Figure Description

[0021] Figure 1 The answer is ABC (BD). n Structural diagram

[0022] Figure 2 Simulation results of long-wavelength emissivity of temperature-adaptive surface radiator in high-temperature and low-temperature states.

[0023] Figure 3 Simulation results of near-infrared emissivity of temperature-adaptive surface radiators when the number of periods n is 1 to 5.

[0024] Figure 4 Schematic diagram of the magnetron sputtering process Detailed Implementation

[0025] To clearly illustrate the device design structure and outstanding advantages described in this invention, the invention will be specifically described below with reference to the accompanying drawings and examples. The embodiments described below are only a part of the embodiments of this invention, not all of them.

[0026] The ABC(BD) of this implementation example n Actual structure as follows Figure 1 As shown, a temperature-adaptive surface radiator structure is involved, where materials A, B, C, and D are Al, Ge, VO2, and TiO2, respectively.

[0027] In this implementation example, for the ABC structural unit, the physical thicknesses of the Al, Ge, and VO2 layers are 10 μm, 0.7 μm, and 0.02 μm, respectively. The infrared emissivity curves of the temperature-adaptive surface radiator at high and low temperatures (8–4 μm) through the atmospheric window are simulated using the finite element method, as shown below. Figure 2 As shown, the average emissivity is 0.87 at high temperature (350K) and 0.02 at low temperature (290K).

[0028] In this implementation example, for (BD) n The structural unit corresponds to a center wavelength of 1100 nm in the reflection spectrum. The refractive index of material B (Ge) is 4.0, and the thickness of material D (TiO2) is 2.35 mm. B =0.0625μm,d D =0.1064μm. The number of periods n ranges from 1 to 5. Figure 3 The near-infrared reflectance is shown for different number of periods n. The near-infrared reflectance for n=1 is 0.159, for n=2 it is 0.222, for n=3 it is 0.406, for n=4 it is 0.726, and for n=5 it is 0.866.

[0029] Furthermore, Figure 4A method for fabricating a magnetron sputtering temperature-adaptive surface radiator developed according to the present invention is demonstrated.

[0030] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A temperature-adaptive surface radiator, characterized in that: The structure of the surface radiator is a multilayer film structure, specifically ABC(BD) n , wherein A, B, C, and D are respectively four materials constituting the surface radiator, and the four materials are respectively Al, Ge, VO2, and TiO2, which are prepared by a magnetron sputtering method; the surface radiator structure is divided into ABC structure units and (BD) n structure units, and n represents the period number corresponding to the (BD) n structure. The components of this structure (BD) n The structural unit is the outer layer; the ABC structural unit is the inner layer, wherein the physical thicknesses of the magnetron sputtered thin films of materials A, B, and C range from 5 to 50 μm, 0.5 to 1 μm, and 0.01 to 0.03 μm, respectively.

2. The temperature-adaptive surface radiator as described in claim 1, characterized in that: Composed of Ge and TiO2 (BD) n The physical thicknesses of the structural unit, thin film Ge, and TiO2 are determined based on the refractive index of the materials and the wavelength of any reflection center, respectively. The formula for calculating the physical thickness is as follows: ； ； in, This represents the physical thickness of material B. Let B be the refractive index. Represents the physical thickness of material D. Let D be the refractive index of material D. This represents the center wavelength of the reflection spectrum.

3. A temperature-adaptive surface radiator as described in claim 2, characterized in that: The range is 0.8~2.5μm, n B =4.0, n D =2.

35.

4. A temperature-adaptive surface radiator as described in claim 1, characterized in that: The number of cycles n ranges from 1 to 5.

Images