CN116394610A - A Flexible Transparent Radiation Cooling Window Material - Google Patents

Abstract

The invention relates to a flexible transparent radiation refrigeration window material, which consists of a middle infrared emission layer, a near infrared reflection layer and a visible light antireflection layer; the middle infrared emission layer is made of high polymer material and has the thickness of 50-300 mu m, so that the absorption/emission of middle infrared wave band is realized; the near infrared reflecting layer is made of silver, has the thickness of 10nm and realizes the reflection of solar spectrum with the near infrared of 0.8-2.5 mu m; the visible light anti-reflection layer is made of high polymer material and has the thickness of 50-300 mu m, and the functions of visible light transmission and near infrared high reflection are realized by constructing a polymer-metal-polymer (PMP) structure; the average transmittance of the material in the visible light wave band of solar radiation of 0.4-0.8 mu m is more than 0.6, the average reflectance in the near infrared wave band of solar radiation of 0.8-2.5 mu m is more than 0.8, and the average emissivity in the atmospheric window of 8-13 mu m is more than 0.95. The radiation refrigeration window material has simple structure and easily obtained raw materials.

Description

A Flexible Transparent Radiation Cooling Window Material

technical field

The invention belongs to the technical field of energy utilization, in particular to daytime radiation refrigeration technology, and in particular to a flexible transparent radiation refrigeration window material.

Background technique

In order to solve the problem of cooling in summer, energy-input cooling methods such as air conditioners are widely used, consuming 15% of the world's electricity and increasing greenhouse gas emissions by 10%, exacerbating problems such as global warming and the energy crisis. Passive thermoregulation may be able to provide a more energy-efficient and economical alternative to traditional infrastructure-based active cooling techniques.

Low-emissivity glass windows with high visible light transparency and high IR reflectivity have been widely used to suppress radiative thermal energy transfer and thus improve thermal insulation. However, in hot climates, they can impede radiative cooling and can lead to unwanted increases in indoor temperatures, commonly known as the greenhouse effect. When solar energy passes through the clear windows of a building or vehicle, it is then absorbed by anything in the room, causing the interior to heat up. When low-e glass windows are used, the radiant heat energy from such heating objects is confined within the building or vehicle, creating a greenhouse effect.

In order to minimize the increase in indoor temperature caused by daytime solar radiation, windows need to suppress the inward transmission of energy in the near-infrared band of the solar spectrum (0.8-2.5 μm wavelength) as much as possible, while for visible light wavelengths (0.4-0.8 μm ) should be effectively transmissive to allow daylighting. In addition, the window should also have a high emissivity (absorption rate) in the "atmospheric window" band (8-13 μm), so as to perform radiation heat exchange with low-temperature outer space to achieve cooling effect. That is, the window exhibits high visible light transparency, near-infrared reflectance, and mid-infrared emission/absorption.

In recent years, many transparent near-infrared filters have been developed to block near-infrared (NIR) solar radiation. However, some NIR filters block NIR solar radiation by absorption, for example, W ₁₈ O ₄₉ , Cu _2-x S/SiO ₂ and (NH ₄ ) _x WO ₃ , which add additional heat load. To reduce the heat load, filtering NIR solar radiation by reflection is an effective method. Such NIR reflective filters can be realized with conductive layers such as ITO and dielectric/metal/dielectric (D/M/D) structures. However, these NIR reflective filters will also exhibit high reflection (low emission) in the mid-infrared (MIR) band, which inhibits radiative cooling. To simultaneously achieve high visible light transmission, NIR reflection, and MIR emission, NIR reflective filters (such as D/M/D or ITO) and transparent MIR emitting structures (such as _SiO2 or PDMS) can be combined. As a common visible light transparent near-infrared reflective film, the D/M/D structure is usually used as a spectrally selective filter, which can transmit most of the visible light and reflect near-infrared solar radiation. Due to the destructive multi-reflection interference, the dielectric layer can enhance the visible light transmission, and the thin metal layer is responsible for the NIR reflection. Studies have shown that the spectral selectivity of the D/M/D structure is higher than that of the ITO structure. As a polymer, PDMS has better absorption/emission properties than SiO ₂ in the "atmospheric window" band (8-13 μm). At the same time, as a flexible base, PDMS has broader application prospects than media. The use of PDMS+D/M/D structure (the structure of dielectric film/metal film/dielectric film plated on the PDMS film substrate) can achieve visible light transparency, near-infrared reflection and mid-infrared emission, but the preparation process needs to be on the PDMS substrate. The D/M/D multi-layer film structure is plated on top, and it is not conducive to large-scale production, which hinders the commercial application of this type of film.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention provides a flexible and transparent radiation cooling window material, which has the required spectral selectivity, simple structure, easy to obtain raw materials, remarkable cooling effect, and is easy to produce in a large area. and application

In order to achieve the purpose of the invention, the present invention adopts the following technical solution: a flexible and transparent radiation cooling window material, which is composed of a mid-infrared emission layer, a near-infrared reflection layer and a visible light anti-reflection layer arranged in sequence.

In a preferred embodiment of the present invention, the mid-infrared emitting layer is a high molecular polymer material with a thickness of 50-300 μm to achieve mid-infrared band absorption/emission; the material of the near-infrared reflective layer is silver, The thickness is 10nm, which realizes the reflection of the near-infrared 0.8-2.5 μm solar spectrum; the visible light anti-reflection layer is a high molecular polymer material, and the thickness is 50-300 μm.

In a preferred embodiment of the present invention, the material of the mid-infrared emitting layer is polydimethylsiloxane (PDMS,) with a thickness of 50-300 μm; the material of the near-infrared reflecting layer is silver, with a thickness of Is 10nm; The material of described visible light anti-reflection layer is polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), polycarbonate (PC), polyvinyl chloride (PVC) Any one of them, with a thickness of 50-300 μm.

In a preferred embodiment of the present invention, the average transmittance of the flexible transparent radiation cooling window material in the 0.4-0.8 μm solar radiation visible light band is greater than 0.6, and the average reflectance in the 0.8-2.5 μm solar radiation near-infrared band is greater than 0.7 , the average emissivity in the "atmospheric window" of 8-13 μm is greater than 0.93.

The flexible transparent radiative cooling window material proposed in this invention can be prepared using physical vapor deposition. For example, the magnetron sputtering coating method uses PDMS film as the substrate, and the target material is silver target. The substrate is placed in a vacuum chamber, filled with argon gas, and then the chamber is energized, and the electrons in the chamber will be in the electromagnetic field. The argon ions collide with the argon atoms under the action of the electromagnetic field, and the argon ions produced are accelerated to hit the silver target under the action of the electromagnetic field, and the silver atoms sputtered by the impact are deposited on the PDMS substrate. Another layer of PDMS is adsorbed on the silver surface to obtain the polymer-metal-polymer (PMP) structure of the present invention.

Compared with the prior art, the beneficial technical effect of the present invention is:

1. The present invention realizes the functions of visible light transmission and near-infrared high reflection by constructing a polymer-metal-polymer (PMP) structure; The transmittance is greater than 0.6, the average reflectance in the 0.8-2.5 μm solar radiation near-infrared band is greater than 0.7, and the average emissivity in the 8-13 μm "atmospheric window" is greater than 0.93.

2. The material of the present invention has a simple symmetrical structure. The outer layer material is a commercial polymer material, especially PDMS. The raw material is easy to obtain, and the thickness range is wide, easy to prepare, and suitable for large-scale production and application.

3. The material of the present invention has a simple symmetrical structure, there is no use direction problem, and the use method is simple.

Description of drawings

Further description will be made below in conjunction with the accompanying drawings.

Fig. 1 is a schematic structural diagram of a flexible transparent radiation cooling window material;

Among them, 1 is a mid-infrared emission layer, 2 is a near-infrared reflection layer, and 3 is a visible light anti-reflection layer.

FIG. 2 is a graph of spectral transmission, reflection and absorption (emission) rate of the coating material of Example 1. FIG.

Fig. 3 is a graph of spectral transmission, reflection and absorption (emission) rate of the coating material of Example 2.

Fig. 4 is a comparison graph of the temperature dependence of the cooling power of the coating material of Example 1 and the common glass material.

Detailed ways

The present invention will be further described through the embodiments below in conjunction with the accompanying drawings.

Example 1

Referring to FIG. 1 , a flexible transparent radiation cooling window material is composed of a mid-infrared emission layer 1 , a near-infrared reflection layer 2 , and a visible light anti-reflection layer 3 arranged in sequence. The material of the mid-infrared emission layer 1 is polydimethylsiloxane film (PDMS) with a thickness of 100 μm; the material of the near-infrared reflection layer 2 is silver with a thickness of 10 nm, and the reflectivity of silver in the 0.3-2.5 μm band is greater than 0.96; The anti-reflection layer 3 is made of polydimethylsiloxane film (PDMS) with a thickness of 100 μm.

The average transmittance of the coating material in the solar radiation near-infrared band (0.8-2.5 μm) is 0.61, the average reflectance in the 8-13 μm "atmospheric window" is 0.72, and the average emissivity is 0.94. The spectral absorption (emission) rate of the coating material is shown in Figure 2.

Example 2

Referring to FIG. 1 , a flexible transparent radiation cooling window material is composed of a mid-infrared emission layer 1 , a near-infrared reflection layer 2 , and a visible light anti-reflection layer 3 arranged in sequence. The material of the mid-infrared emission layer 1 is polydimethylsiloxane film (PDMS) with a thickness of 80 μm;) The material of the near-infrared reflection layer 2 is silver with a thickness of 10 nm, and the reflectivity of silver in the 0.3-25 μm band is greater than 0.96. The visible light anti-reflection layer 3 is made of polyethylene terephthalate (PET) with a thickness of 300 μm.

The coating material has an average transmittance of 0.65 in the solar radiation near-infrared band (0.8-2.5 μm), an average reflectance of 0.71 in the 8-13 μm "atmospheric window", and an average emissivity of 0.94. The spectral absorption (emission) rate of the coating material is shown in Figure 3.

Example 3

Referring to FIG. 4 , the transparent radiation cooling window material with the structure of 100 μm PDMS/10nm Ag/100 μm PDMS in Example 1 is compared with a common glass material window of the same thickness. When the net cooling power is 0, there is a difference of about 20 degrees Celsius in the steady-state temperature between the radiation cooling window material in Example 1 and ordinary glass of the same thickness. The coating material obtained by the present invention has higher cooling efficiency than ordinary glass at all temperatures, thereby effectively achieving lower temperatures. It can be seen that the present invention has significantly better cooling efficiency than the prior art.

The above content is a further description of the present invention in conjunction with specific/preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. On the premise of not departing from the concept of the present invention, several substitutions or modifications made to these described embodiments should be considered as belonging to the protection scope of the present invention.

Claims (4)

1. A flexible transparent radiation refrigeration window material is characterized by comprising a middle infrared emission layer, a near infrared reflection layer and a visible light reflection-increasing layer which are sequentially arranged.

2. The flexible transparent radiation refrigeration window material according to claim 1, wherein the middle infrared emission layer is made of high molecular polymer material, and has a thickness of 50-300 μm, so as to realize middle infrared band absorption/emission; the near infrared reflecting layer is made of silver, has the thickness of 10nm and realizes the reflection of solar spectrum with the near infrared of 0.8-2.5 mu m; the visible light anti-reflection layer is made of high polymer material and has a thickness of 50-300 mu m.

3. The flexible transparent radiation refrigeration window material as claimed in claim 1, wherein the material of the middle infrared emission layer is Polydimethylsiloxane (PDMS) with a thickness of 50-300 μm; the near infrared reflecting layer is made of silver, and the thickness of the near infrared reflecting layer is 10nm; the visible light antireflection layer is made of any one of Polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), polycarbonate (PC) and polyvinyl chloride (PVC), and has a thickness of 50-300 mu m.

4. A flexible transparent radiation transparent refrigeration window material as claimed in any one of claims 1 to 3 wherein said flexible transparent radiation refrigeration window material has an average transmittance of greater than 0.6 in the 0.4 to 0.8 μm solar radiation visible light band, an average reflectance of greater than 0.7 in the 0.8 to 2.5 μm solar radiation near infrared band and an average emissivity of greater than 0.93 in the 8 to 13 μm "atmospheric window".

Images