A smart window coupled with evaporative cooling and multi-level light regulation and a method for preparing the same

Abstract

A smart window coupled with evaporative cooling and multi-level light regulation and a preparation method thereof, the smart window comprising a double-layer glass with a sealed interlayer space, at least one glass surface of the double-layer glass being coated with a thermochromic gel coating located in the sealed interlayer space, and the thickness of the sealed interlayer space being greater than the thickness of the thermochromic gel coating; the thermochromic gel coating being composed of sodium carboxymethyl cellulose, N Isopropyl acrylamide, a crosslinking agent, a photoinitiator and water are mixed and photo-crosslinked and polymerized at a reaction temperature of 0-10°C and under ultraviolet light irradiation to form. The smart window of the present invention has a closed interlayer space with low thermal conductivity, so that: the heat conduction resistance between the gel and the external environment is enhanced; a space for the evaporation of thermochromic gel water is provided; and a self-circulating system of water evaporation and absorption is established through the integration of the cavity and the gel layer.

Description

Technical Field

[0001] The present invention relates to the field of smart windows, and in particular to a smart window coupled with evaporative cooling and multi-stage light regulation and a preparation method thereof. Background Art

[0002] Due to the demand for indoor heating and cooling, the energy consumption of building thermal management accounts for about one-fifth of global energy consumption. However, windows, as an important part of the building envelope, are regarded as the basic unit with the worst energy-saving performance in building thermal management. For building energy conservation, ideal windows need to have spectral adaptive adjustment performance, maintain high transmittance when the indoor temperature is low for good indoor photothermal heating, and increase reflectivity when the indoor temperature is high to block sunlight and promote indoor cooling.

[0003] At present, a variety of smart thermal management windows with switchable optical properties have been developed to improve the energy-saving performance of windows. Among them, the thermochromic mechanism based on the photothermal effect can achieve the change of optical mode without additional energy input, making it an environmentally friendly and highly economical driving strategy. Typical thermochromic materials include hydrogels, ionic liquid gels, composite gels, liquid crystal polymers, perovskites, VO2 and their derivatives.

[0004] PNIPAM is a typical thermochromic polymer widely used for light modulation in smart thermal management windows. So far, PNIPAM-based responsive gels have mainly focused on enhancing solar modulation in smart thermal management windows, while ignoring the importance of LCST for energy saving in building thermal management. Most smart thermal management window designs fail to make the LCST consistent with the human body's comfortable temperature range (23-28°C). When the LCST is much higher or lower than the human body's comfortable temperature range, an air conditioning system is required to adjust the indoor temperature to maintain the body's thermal comfort, resulting in high energy consumption.

[0005] Due to the low viscosity of the reaction precursors and the long synthesis time of most PNIPAM-based hydrogels, the design of traditional smart windows is usually limited to a sandwich structure, where the thermochromic material is tightly wrapped between two pieces of glass. However, this structure has several significant disadvantages.

[0006] Take a building with a large temperature difference between indoor and outdoor as an example. Due to the lack of thermal insulation, traditional smart thermal management windows cannot prevent heat from being transferred from the outside to the inside when the outside temperature is high, nor can they prevent internal heat from being transferred to the outside when the outside temperature is low. In addition, when the gel undergoes a phase change in a high-temperature environment to prevent sunlight from entering the room, the thermochromic gel body will absorb part of the blocked sunlight, causing the gel temperature to rise. For traditional smart windows, due to the close-fitting sandwich structure design, the glass adjacent to the high-temperature gel will promote heat conduction into the room, resulting in unnecessary indoor heating. However, the structural design of smart windows, as one of the potential ways to improve building thermal management and energy saving, has not received much attention.

[0007] During the heating process, the conformational changes of PNIPAM molecules endow the gel with different optical properties, and the phase change process is accompanied by the discharge of free water. Since water has an extremely high latent heat of evaporation, 300Wm can be achieved by evaporative cooling at 30°C. −2 This thermal regulation strategy, which could potentially solve the problem of insufficient window cooling capacity, has been overlooked.

[0008] When smart windows with thermochromic gels adjust sunlight and temperature through phase change at high temperatures, they inevitably sacrifice the transmittance of the windows and affect indoor lighting. Therefore, balancing thermal regulation and transmittance is another major challenge facing smart windows.

[0009] At present, smart windows still have the following three shortcomings:

[0010] (1) The existing thermal control strategies / mechanisms of smart windows are single, and the thermal regulation efficiency needs to be improved;

[0011] (2) Existing smart windows lack good thermal insulation performance, which not only causes heat exchange between indoor and outdoor, increasing the energy consumption of indoor thermal control, but also affects the phase change process of the temperature-sensitive material inside the smart window, causing phase change hysteresis;

[0012] (3) When smart windows regulate sunlight and temperature through phase change at high temperatures, they inevitably sacrifice the transmittance of the windows. Therefore, balancing thermal regulation and transmittance remains a major challenge for smart windows. Summary of the invention

[0013] At present, there is a lack of smart windows and their manufacturing technology that couple evaporative cooling and multi-level light regulation, which cannot meet the requirements of achieving adaptive thermal regulation while having good thermal management performance and balanced light-heat regulation capabilities and being suitable for large-scale production. Based on this, the present invention provides a smart window that couples evaporative cooling and multi-level light regulation.

[0014] To achieve the above object, the present invention provides a smart window coupled with evaporative cooling and multi-level light regulation, which comprises a double-layer glass with a closed interlayer space, at least one glass surface of the double-layer glass is coated with a thermochromic gel coating located in the closed interlayer space, and the thickness of the closed interlayer space is greater than the thickness of the thermochromic gel coating;

[0015] The thermochromic gel coating is formed by mixing sodium carboxymethyl cellulose, N-isopropyl acrylamide, a crosslinking agent, a photoinitiator and water and performing photocrosslinking polymerization at a reaction temperature of 0-10°C under ultraviolet light irradiation, wherein the mass ratio of sodium carboxymethyl cellulose to N-isopropyl acrylamide is (0.1-0.6):1, the amount of water used is 5-8 times the mass of N-isopropyl acrylamide, and the crosslinking agent is N,N-methylenebisacrylamide or divinylbenzene.

[0016] As a further preferred technical solution of the present invention, sealing gaskets are provided around the double-layer glass, and the sealing gaskets are used to separate and seal the two sheets of glass of the double-layer glass. The glass is one or more of silica glass, polymethyl methacrylate organic glass, polycarbonate glass, polyethylene glass, silver-plated glass, ITO glass or other functionalized derivative glass.

[0017] As a further preferred technical solution of the present invention, the thickness of the thermochromic gel coating is 0.5-5 mm, and the thickness of the enclosed interlayer space is 2-10 mm. The thickness of the enclosed interlayer space refers to the distance between the two layers of glass, and ensures that there is a cavity layer between the double layers of glass in addition to the thermochromic gel coating. Further preferably, the thickness of the thermochromic gel coating is 1-2 mm, and the thickness of the enclosed interlayer space is 3-5 mm.

[0018] As a further preferred technical solution of the present invention, the closed interlayer space is filled with nitrogen, argon or air.

[0019] As a further preferred technical solution of the present invention, the photoinitiator is 2-hydroxy-2-methylpropiophenone.

[0020] As a further preferred technical solution of the present invention, the mass ratio of the cross-linking agent to N-isopropylacrylamide is 1:(200-1000).

[0021] As a further preferred technical solution of the present invention, there are multiple thermochromic gel coatings in the closed interlayer space, different thermochromic gel coatings use different ratios of sodium carboxymethyl cellulose and N-isopropyl acrylamide, and multiple thermochromic gel coatings overlap or are staggered.

[0022] As a further preferred technical solution of the present invention, during the photo-crosslinking polymerization process, the wavelength of the ultraviolet light is 365 nm, and the ultraviolet irradiation time is 2-5 min.

[0023] According to another aspect of the present invention, the present invention also provides a method for preparing a smart window coupled with evaporative cooling and multi-level light regulation, comprising the following steps:

[0024] S1, adding sodium carboxymethyl cellulose and N-isopropyl acrylamide into water and mixing well to obtain a viscous solution;

[0025] S2, adding a crosslinking agent and a photoinitiator into the viscous solution and mixing evenly to obtain a reaction precursor solution;

[0026] S3, applying the reaction precursor liquid to the surface of the glass substrate according to a preset plane pattern, and standing to remove bubbles or vacuum removing bubbles,

[0027] S4. Assemble the defoamed glass substrate with another glass substrate to form a double-layer glass with a closed interlayer space, and make the coated reaction precursor liquid located in the closed interlayer space, and the distance between the two glass substrates is greater than the coating thickness of the reaction precursor liquid, and then perform photo-crosslinking polymerization at a temperature of 0-10°C and under ultraviolet light irradiation.

[0028] As a further preferred technical solution of the present invention, in step S3, the reaction precursor liquid is applied to the surface of the glass substrate in a preset plane pattern by printing, scraping or 3D printing.

[0029] The thermochromic gel prepared with sodium carboxymethyl cellulose and N-isopropyl acrylamide provides good adaptive spectral regulation performance in smart windows (also known as smart thermal management windows). The thermochromic gel is patterned on the glass surface by printing, scraping and 3D printing, thereby constructing a new type of smart thermal management window with multi-level light regulation performance, which can well balance indoor visibility and thermal management requirements. In addition, in the enclosed interlayer space, the thermochromic gel also provides a water source required for evaporative cooling performance. The enclosed interlayer space with low thermal conductivity has three key functions: (1) enhancing the heat conduction resistance between the gel and the external environment; (2) providing space for the evaporation of thermochromic gel water; (3) establishing a self-circulating system of water evaporation and absorption through the integration of the cavity and the gel layer. For this new window structure, the thermochromic gel is preferably arranged on the indoor side of the double-layer glass. Due to the heat insulation effect of the enclosed interlayer space, the thermochromic gel near the inner side of the window can quickly respond to changes in indoor temperature to maintain a comfortable indoor temperature. And, more importantly, heat is what drives the water evaporation cycle.

[0030] The innovative multi-level structural design of smart windows has opened up a new way to save energy in light / heat regulation of building or car windows. In addition, the preparation process is simple and the preparation cycle is extremely short, making it suitable for large-scale production.

[0031] Compared with the prior art, the following beneficial effects can be achieved:

[0032] 1) The smart window coupled with evaporative cooling and multi-level light regulation provided by the present invention exhibits the characteristics of high efficiency, zero energy consumption, and adaptive switching of thermal management modes. The window also has the advantages of large-scale preparation and low cost.

[0033] 2) The smart window coupled with evaporative cooling and multi-level light regulation provided by the present invention can autonomously adjust the solar spectrum absorption / reflectivity without energy consumption by sensing temperature changes, and the cooling process is also coupled with the evaporative cooling mechanism.

[0034] 3) The smart window coupled with evaporative cooling and multi-level light regulation provided by the present invention improves the heat transfer resistance of the window and can avoid a large amount of heat conduction between indoor and outdoor, while alleviating the response hysteresis behavior of the gel. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0036] Figure 1 It is a diagram showing the mechanism of action of the smart window of the present invention (Example 1) and the traditional smart window (Comparative Example 1) when used in thermal insulation.

[0037] Figure 2 These are digital photos of the smart window of the present invention (Example 1) and the traditional smart window (Comparative Example 3) after being heated at 35°C for 20 minutes.

[0038] Figure 3 The thermal management temperature curves of the smart window of the present invention and other traditional glass windows under simulated environment, wherein, Air: ambient temperature; Glass: ordinary glass temperature; Low-e glass: commercial low-emissivity glass temperature; PNI-C: temperature of traditional sandwich structure smart window filled with 2mm PNIPAM gel (Comparative Example 1); PNC-N: temperature of a new smart window with 3mm cavity structure filled with 2mm PNIPAM-based gel (Example 1).

[0039] Figure 4The thermal management temperature curves of the smart window of the present invention and other traditional glass windows under a simulated environment, wherein Air: ambient temperature; Hotplate: hot plate temperature; I-glass: temperature of ordinary insulating glass containing a 3mm cavity; PNC-C: temperature of a traditional sandwich structure smart window filled with 2mm PNIPAM-based gel (Comparative Example 2); PNC-N: temperature of a new smart window with a 3mm cavity structure filled with 2mm PNIPAM-based gel (Example 1).

[0040] Figure 5 It is the light shielding performance curve of the smart window of the present invention and the traditional smart window under simulated environment, wherein, PNC-C: the temperature of the traditional sandwich structure smart window filled with 2mm PNIPAM-based gel (Comparative Example 2); PNC-N: the temperature of the new smart window filled with 2mm PNIPAM-based gel and with a 3mm cavity structure (Example 1).

[0041] Figure 6 This is a physical display diagram of the multi-level light control smart window in the dimming process in Example 2. In the figure, t is the ambient temperature, t lcst1 is the response temperature of the gel coating corresponding to the reaction precursor solution No. 6, t lcst2 The response temperature of the gel coating corresponding to the reaction precursor solution No. 4.

[0042] Figure 7 This is a physical display diagram of the multi-level light-regulating smart window during the dimming process in Example 3, wherein numbers 4 and 6 refer to gel coatings formed using reaction precursor solutions with corresponding numbers in Table 1.

[0043] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0044] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0045] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0046] 1. Prepare six groups of reaction precursor samples according to Table 1

[0047] According to the corresponding sample numbers in Table 1, sodium carboxymethyl cellulose and N-isopropyl acrylamide were weighed; sodium carboxymethyl cellulose was dissolved in 2.5 mL of ultrapure water to obtain a solution with a certain viscosity; 300 mg of N-isopropyl acrylamide was added to the solution, and the solution was fully stirred and dissolved to obtain a solution; then 0.5 mg of a cross-linking agent N,N-methylenebisacrylamide and 3 mg of a photoinitiator 2-hydroxy-2-methylpropiophenone were sequentially added to the solution, and the solution was stirred evenly to obtain a reaction precursor solution.

[0048] A rotational rheometer (MCR302, Anton Paar GmbH, Austria) was used to test the viscosity and loss factor of each reaction precursor at different shear rates to evaluate the gelation characteristics of the reaction precursor. During the test, the test environment temperature was maintained at 20 °C, and a 1° cone plate with a diameter of 5 cm was selected. The test results are shown in Table 1.

[0049] The reaction precursor liquid is placed in a sealed reagent bottle, and the self-supporting property of the reaction precursor liquid is tested by observing whether the shape of the reaction precursor liquid in the reagent bottle deforms and flows randomly or remains stable at different rotation angles. The test results are shown in Table 1.

[0050] 2. Characterization of the thermochromic hydrogel samples formed by the above six groups of reaction precursor solutions

[0051] The reaction precursor liquid sample was coated on the surface of the glass substrate by screen printing technology with a thickness of 2 mm; then it was irradiated with ultraviolet light at a reaction temperature of 5 °C to achieve photocrosslinking polymerization. The ultraviolet light wavelength was 365 nm and the ultraviolet irradiation time was 3 min to obtain a thermochromic hydrogel.

[0052] The response temperature of the sample was tested by differential scanning calorimetry (Q2000, TA Instruments-Waters LLC, USA). Specifically, 5-10 mg of the sample was placed in an aluminum crucible, and the temperature measurement procedure was as follows: the equilibrium temperature was set to 20 °C, isothermal at 20 °C for 1 min, and heated from 20 °C to 40 °C at a heating rate of 2 °C / min. The response temperature of the material was determined by observing the change in thermal enthalpy of the thermochromic hydrogel sample during the heating process. The results are shown in Table 1.

[0053] In order to observe the dimensional stability and phase transition reaction rate of the gel above the phase transition temperature, the results are shown in Table 1. The prepared gel sample was placed on a hot stage at 40 °C, and the morphological changes and surface temperature changes of the gel within 20 min were recorded using a digital camera and a thermal infrared imager (the initial temperature of the gel sample was 20 °C), and finally the area shrinkage of the gel before and after heating was calculated. At the same time, during the heating process, the time required for the gel to change from the initial transparent to white was observed.

[0054] Table 1

[0055] Sample No. Sodium carboxymethyl cellulose (mg) N-isopropylacrylamide(mg) <![CDATA[Viscosity (Pa s -1 )]]> Loss Factor Response temperature(℃) Area shrinkage (%) Phase change speed (s) Self-supporting 1 0 300 0.005 - 31.5 52 >60 none 2 30 300 1.5 3.4 30.5 33 <50 Poor 3 60 300 15.7 1.6 29.5 16 <40 generally 4 90 300 94.6 0.9 28.5 5 <30 good 5 120 300 257.2 0.6 27.5 4 <30 good 6 180 300 1032.4 0.5 26.5 3 <30 good

[0056] Comparative Example 1

[0057] A conventional sandwich structure smart window without a cavity structure is provided, wherein the smart window comprises double-layer glass, and a preparation method of the double-layer glass is as follows:

[0058] Two identical pieces of glass were selected, and the reaction precursor liquid sample No. 1 in Table 1 was attached to the entire surface of one of the glasses by scraping, with a scraping thickness of 2 mm, and then naturally allowed to stand for 10 min to remove bubbles; then, the two pieces of glass were overlapped so that the attached reaction precursor liquid was clamped between the two pieces of glass, and the spacing between the two pieces of glass was 2 mm; finally, photo-cross-linking polymerization was carried out at 5 ℃ under ultraviolet light irradiation, the ultraviolet light wavelength was 365 nm, and the ultraviolet irradiation time was 3 min.

[0059] During use, the window prepared in this comparative example has the following problems. Figure 1 As shown in the figure, under conditions higher than the gel response temperature, the gel is very easy to shrink (area shrinkage rate is greater than 50%) due to the rapid dehydration during the gel phase change process, resulting in a reduction in the coverage area of ​​the gel on the glass surface. At the same time, due to the lack of evaporation space, the escaped water molecules cannot achieve a good evaporative cooling effect.

[0060] Comparative Example 2

[0061] A conventional sandwich structure smart window without a cavity structure is provided. The difference from Comparative Example 1 is that a reaction precursor solution No. 4 is used to prepare a gel coating. The preparation method is as follows:

[0062] Two identical pieces of glass were selected, and the reaction precursor liquid sample No. 4 in Table 1 was attached to the entire surface of one of the glasses by scraping, with a scraping thickness of 2 mm, and then naturally left to stand for 10 min to remove bubbles; then, the two pieces of glass were overlapped so that the attached reaction precursor liquid was clamped between the two pieces of glass, and the spacing between the two pieces of glass was 2 mm; finally, photo-cross-linking polymerization was carried out at 5 ℃ under ultraviolet light irradiation, the ultraviolet light wavelength was 365 nm, and the ultraviolet irradiation time was 3 min.

[0063] Comparative Example 3

[0064] A traditional smart window with a cavity structure is provided, which is different from Comparative Example 1 in that the spacing between the double-layer glass is greater than the coating thickness of the reaction precursor liquid, and the double-layer glass is sealed on all sides.

[0065] Two identical pieces of glass were selected, and the reaction precursor liquid sample No. 1 in Table 1 was attached to the entire surface of one of the glasses by scraping, with a scraping thickness of 2 mm, and then naturally left to degas for 10 min; then, the two pieces of glass were overlapped so that the attached reaction precursor liquid was clamped between the two pieces, and the spacing between the two pieces of glass was kept at 5 mm, and sealing strips were provided around the two pieces of glass to seal the interlayer space; finally, photo-crosslinking polymerization was carried out at 5 ℃ under ultraviolet light irradiation, the ultraviolet light wavelength was 365 nm, and the ultraviolet irradiation time was 3 min.

[0066] Since the reaction precursor liquid No. 1 lacks good self-supporting properties, the double-glazed window containing the reaction precursor liquid No. 1 can only be UV-cured when kept flat, otherwise a uniform and smooth gel coating cannot be formed on the glass surface. During use, the window prepared in this comparative example also has problems. Under high temperature conditions, the gel is easily shrunk due to the rapid dehydration of the gel phase change process, resulting in a reduction in the coverage area of ​​the gel on the glass surface or direct detachment. At the same time, a large number of escaping water molecules will gather at the bottom of the glass window and cannot play a good evaporative cooling effect (such as Figure 2 as shown).

[0067] Example 1

[0068] Provided is a smart window with coupled evaporative cooling having a cavity structure, which differs from Comparative Example 2 in that the reaction precursor solution sample contains sodium carboxymethyl cellulose.

[0069] Two identical pieces of glass were selected, and the reaction precursor sample No. 4 in Table 1 was attached to the entire surface of one of the glasses by scraping, with a scraping thickness of 2 mm, and then naturally left to stand for 10 min to remove bubbles; then, the two pieces of glass were overlapped so that the attached reaction precursor was clamped between the two pieces of glass, and the spacing between the two pieces of glass was kept at 5 mm, and the interlayer space of the two pieces of glass was sealed by sealing strips around them; finally, photo-crosslinking polymerization was carried out at 5 ℃ under ultraviolet light irradiation, the ultraviolet light wavelength was 365 nm, and the ultraviolet irradiation time was 3 min.

[0070] Since the reaction precursor liquid No. 4 has good self-supporting properties, the double-glazed window containing the reaction precursor liquid No. 4 can form a uniform and smooth gel layer on the glass surface even if it is not placed flat for UV curing. In addition, during use, the window prepared in this embodiment effectively avoids the problem of free flow of the coating liquid in Comparative Example 3, and the gel does not fall off directly from the glass surface or shrink severely during the entire heating process. The control experimental results of Comparative Example 3 are as shown in FIG. Figure 2 shown.

[0071] In the gel coating of this embodiment, when the temperature is higher than the response temperature, although the gel undergoes a phase change, the water molecules inside the gel slowly move to the gel surface due to the support of the sodium carboxymethyl cellulose molecular network, and evaporate on the gel surface to remove the heat from the gel surface and play an evaporative cooling role. In addition, due to the sealed design inside the window, when water vapor encounters the upper surface glass with a lower temperature, it will condense and drip onto the gel surface, and can be absorbed again by the gel with good hygroscopicity, thereby coupling evaporative cooling and forming a self-circulating utilization of water. The mechanism of action is as follows: Figure 1 As shown. To this end, in order to address the shortcomings of the traditional sandwich structure as in Comparative Example 1, we designed a new window structure to improve the thermal management performance by adding a cavity layer to the outer surface of the thermochromic gel coating. In this new structure, the cavity layer characterized by low thermal conductivity has three key functions: (1) enhancing the heat conduction resistance between the gel and the external environment; (2) providing space for water evaporation; (3) establishing a self-circulating system of water evaporation and absorption through the integration of the cavity and gel layer. For this new window structure, due to the thermal insulation effect of the cavity layer, the thermosensitive gel near the inside of the window can respond to changes in indoor temperature to maintain a comfortable indoor temperature. More importantly, the driving factor of the water evaporation cycle is heat.

[0072] To characterize the zero-energy adaptive thermal management performance of smart windows, we covered the following different windows with a 4×4×4 cm 3 The test equipment was placed in an open cavity box (used to simulate indoor space) and the connection between the window and the box was sealed with metal tape. The assembled test equipment was then placed in an outdoor environment and the temperature changes inside the box were recorded with a thermocouple. The outdoor test results show that when the outdoor ambient temperature is 18°C ​​(lower than the comfortable ambient temperature for humans), the internal temperature of the box covering the smart window of this embodiment will gradually increase with the increase of light exposure time and maintain at around 30°C (close to the comfortable temperature zone for humans), which is lower than the internal temperature of the box covering ordinary glass windows by more than 10°C and 3-6°C lower than the internal temperature of the box covering the traditional sandwich structure window of Comparative Example 1 ( Figure 3 ). This fully demonstrates that the smart window prepared in this case can meet the adaptive regulation and thermal management mode without the intervention of additional energy.

[0073] In order to evaluate the effect of increasing thermal resistance of smart windows with cavity structures in a thermal environment, we fixed the following three types of windows on a hot plate, namely, a hollow window with a 3 mm cavity (I-glass), the window in Comparative Example 2 (PNC-C), and the smart window of this embodiment (PNC-N), and recorded the bottom temperature of each window. After heating for 60 minutes, the bottom temperature of the window in Comparative Example 2 was the lowest, which was 0.6 °C and 2.4 °C lower than that of the smart window and I-glass in this embodiment 1, respectively ( Figure 4 ). During the heating process, the heat conduction from the bottom of the I-glass to the external environment is hindered by the heat insulation cavity layer, causing heat accumulation at the bottom of the window, so that the temperature at the bottom is the highest. In contrast, the gel introduced into the smart window of this embodiment not only has the same air insulation effect as the I-glass, but also promotes heat dissipation to the environment through evaporative cooling, thereby reducing the temperature at the bottom of the window within a certain range.

[0074] Subsequently, we tested the effects of the smart windows of Comparative Example 2 and this embodiment on the simulated indoor environment (ambient temperature of 19 °C, simulated indoor temperature of 30 °C, light intensity of 25 mW cm -2 ) to prove that the cavity layer can alleviate the phase transition hysteresis behavior of the gel. Figure 5 The low thermal conductivity of the cavity layer prevents heat exchange between the room and the outside environment, which enables the smart window of this embodiment to be the first to achieve phase change shading, and the transition from transparent to opaque is completed within 360 seconds. For the conventional sandwich structure window of Comparative Example 2 without an insulation cavity, the phase change reaction time is relatively long (>540 s).

[0075] Example 2

[0076] A smart window with coupled evaporative cooling and multi-level light regulation having a cavity structure is provided to achieve adaptive multi-level spectral regulation intelligent thermal management of a Venetian blinds structure.

[0077] Two identical pieces of glass were selected, and the reaction precursor samples No. 4 and 6 in Table 1 were alternately printed on one of the pieces of glass in a stripe pattern. Each stripe pattern was staggered at equal intervals to form a Venetian blind structure. The pattern printing thickness was 2 mm, and then it was naturally left to degas for 10 min. Then, the two pieces of glass were overlapped so that the attached reaction precursor liquid was clamped between the two pieces, and the spacing between the two pieces of glass was kept at 5 mm. The interlayer space of the two pieces of glass was sealed by sealing strips around them. Finally, photo-crosslinking polymerization was carried out at 5 °C under ultraviolet light irradiation. The ultraviolet light wavelength was 365 nm and the ultraviolet irradiation time was 3 min.

[0078] Smart windows with thermochromic gels regulate sunlight and temperature through phase change at high temperatures, but this inevitably affects the transmittance of the windows. Therefore, balancing thermal regulation and transmittance is a major challenge for smart windows. Inspired by the structure of blinds, in this example, we prepared a smart window with multi-level light regulation based on PNC gel reaction precursors with self-supporting and adjustable LCST (numbers 4 and 6 in Table 1), such as Figure 6 As shown. The smart window in this embodiment exhibits high transmittance at low temperatures. When the ambient temperature reaches 26 °C, the area covered by the low LCST gel coating undergoes a phase change, effectively blocking a portion of the sunlight. Although the sunlight transmittance decreases during the first stage transition, the visibility of the smart window can still be maintained, when the ambient temperature is between the response temperatures of the two gel coatings. As the temperature increases, it is necessary to reduce the amount of sunlight entering the room, and the high LCST gel coating undergoes a phase change and blocks some light channels, further reducing the amount of sunlight entering the room, when the ambient temperature is higher than the response temperature of the two gel coatings. It can be seen that the multi-level light regulation generated by the patterning strategy broadens the application scenarios of smart windows with different thermal and light regulation requirements.

[0079] Example 3

[0080] A smart window with coupled evaporative cooling and multi-level light regulation having a cavity structure is provided to achieve adaptive multi-level spectral regulation intelligent thermal management of a Venetian blinds structure.

[0081] Two identical pieces of glass were selected, and the reaction precursor samples No. 6 and 4 in Table 1 were printed on the upper and lower halves of one of the glasses, respectively, with a printing thickness of 2 mm, and then left to stand naturally to remove bubbles for 10 min; then, the two pieces of glass were overlapped so that the attached reaction precursor liquid was clamped between the two pieces, and the spacing between the two pieces of glass was kept at 5 mm, and the interlayer space of the two pieces of glass was sealed by sealing strips around them; finally, photo-crosslinking polymerization was carried out at 5 ℃ under ultraviolet light irradiation, the ultraviolet light wavelength was 365 nm, and the ultraviolet irradiation time was 3 min.

[0082] In this embodiment, the smart window integrated with thermochromic gels with different response temperatures is placed in an outdoor environment in summer. It can be clearly observed that the smart window has extremely high transparency before phase change. As the temperature and light exposure time increase, the smart window exhibits obvious two-level shading performance, that is, the thermochromic gel with low response temperature at the bottom undergoes phase change first, and as the temperature rises, the gel with high phase change temperature at the top undergoes phase change ( Figure 7 ).

[0083] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A smart window that couples evaporative cooling and multi-level light regulation, characterized in that: A double-layer glass having a sealed interlayer space, wherein at least one glass surface of the double-layer glass is coated with a thermochromic gel coating located in the sealed interlayer space, and the thickness of the sealed interlayer space is greater than the thickness of the thermochromic gel coating; The thermochromic gel coating is formed by mixing sodium carboxymethyl cellulose, N-isopropyl acrylamide, a crosslinking agent, a photoinitiator and water and performing photocrosslinking polymerization at a reaction temperature of 0-10°C under ultraviolet light irradiation, wherein the mass ratio of sodium carboxymethyl cellulose to N-isopropyl acrylamide is (0.1-0.6):1, the amount of water used is 5-8 times the total mass of sodium carboxymethyl cellulose and N-isopropyl acrylamide, and the crosslinking agent is N,N-methylenebisacrylamide or divinylbenzene.

2. The smart window coupled with evaporative cooling and multi-level light regulation according to claim 1, characterized in that: Sealing gaskets are arranged around the double-layer glass, and the sealing gaskets are used to separate and seal the two sheets of glass of the double-layer glass.

3. The smart window coupled with evaporative cooling and multi-level light regulation according to claim 1, characterized in that: The thickness of the thermochromic gel coating is 0.5-5 mm, and the thickness of the closed interlayer space is 2-10 mm.

4. The smart window coupled with evaporative cooling and multi-level light regulation according to claim 1, characterized in that: The closed interlayer space is filled with nitrogen, argon or air.

5. The smart window coupled with evaporative cooling and multi-level light regulation according to claim 1, characterized in that: The photoinitiator is 2-hydroxy-2-methylpropiophenone.

6. The smart window coupled with evaporative cooling and multi-level light regulation according to claim 1, characterized in that: The mass ratio of the cross-linking agent to N-isopropylacrylamide is 1:(200-1000).

7. The smart window coupled with evaporative cooling and multi-level light regulation according to claim 1, characterized in that: There are multiple thermochromic gel coatings in the closed interlayer space, different thermochromic gel coatings use different ratios of sodium carboxymethyl cellulose and N-isopropyl acrylamide, and the multiple thermochromic gel coatings are overlapped or staggered.

8. The smart window coupled with evaporative cooling and multi-level light regulation according to any one of claims 1 to 7, characterized in that: During the photo-cross-linking polymerization process, the wavelength of the ultraviolet light is 365 nm and the ultraviolet irradiation time is 2-5 min.

9. A method for preparing a smart window coupled with evaporative cooling and multi-level light regulation according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, adding sodium carboxymethyl cellulose and N-isopropyl acrylamide into water and mixing well to obtain a viscous solution; S2, adding a crosslinking agent and a photoinitiator into the viscous solution and mixing evenly to obtain a reaction precursor solution; S3, applying the reaction precursor liquid to the surface of the glass substrate according to a preset plane pattern, and standing to remove bubbles or vacuum removing bubbles, S4. Assemble the defoamed glass substrate with another glass substrate to form a double-layer glass with a closed interlayer space, and make the coated reaction precursor liquid located in the closed interlayer space, and the distance between the two glass substrates is greater than the coating thickness of the reaction precursor liquid, and then perform photo-crosslinking polymerization at a temperature of 0-10°C and under ultraviolet light irradiation.

10. The method for preparing a smart window coupled with evaporative cooling and multi-level light regulation according to claim 9, characterized in that: In step S3, the reaction precursor liquid is applied to the surface of the glass substrate in a preset plane pattern by printing, scraping or 3D printing.

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