A new thermochromic smart window with adjustable emissivity

Abstract

The invention discloses a novel thermochromic intelligent window with adjustable emissivity, comprising a window frame, a glass component installed inside the window frame, the glass component comprising a glass substrate, a metal oxide coating for adjusting the glass substrate to have a low radiation function in the mid-infrared region is deposited on one side of the glass substrate, the metal oxide coating is a layer of transparent indium tin oxide film, a solar energy regulating high radiation part is installed on the other side of the glass substrate, the solar energy regulating high radiation part comprises a first polyethylene layer, a hydroxypropyl cellulose hydrogel layer is installed on the upper part of the first polyethylene layer, the hydroxypropyl cellulose hydrogel layer is also installed with a second polyethylene layer, and the hydroxypropyl cellulose hydrogel layer is wrapped in the middle by the first polyethylene layer and the second polyethylene layer. The invention can dynamically adjust the thermal radiation and solar transmittance of different bands according to the changes of seasons and climate, so as to reduce the indoor temperature and save energy consumption, reduce the cooling load of the building in summer and reduce the heat loss in winter.

Description

Technical Field

[0001] The invention relates to the technical field of heat energy recovery and utilization, and in particular to a novel thermochromic intelligent window with adjustable emissivity. Background Art

[0002] The signing of the Paris Agreement in 2018 emphasized the importance of setting the global warming limit at 1.5℃ to reduce carbon dioxide emissions and save energy, and called on the global community to reduce carbon emissions. Since building energy consumption accounts for 40% of global energy consumption, and heating, ventilation and air conditioning applications account for half of building energy consumption, improving the energy efficiency of air conditioning applications has become a key task to improve building sustainability.

[0003] Compared with other building components, windows are considered to be the least energy-efficient part of a building. Direct sunlight through windows is the main factor causing room temperature increase in summer, while more than 30% of energy loss in winter is also caused by windows. Three wavelengths of light, namely visible light (360-780nm), near-infrared (780-2500nm) and mid-infrared (8-13μm), are very important for window energy saving. Among them, visible light and near-infrared contribute to indoor heating, while mid-infrared is related to thermal radiation. Therefore, an ideal energy-saving smart window should have low solar transmittance and high mid-infrared emissivity in summer to prevent the window from being heated by sunlight and dissipating heat rapidly through thermal radiation; while in winter, the window must have high transparency in both visible and near-infrared bands and low mid-infrared emissivity to promote solar heating and prevent heat loss. A promising energy-saving smart window should have both high solar modulation capacity ΔTsol and good mid-infrared emissivity switching capability.

[0004] Color-displaying energy-saving windows are one of the more popular research directions at present, because they can adjust the transmittance of sunlight when receiving stimuli. According to different stimuli, color-displaying energy-saving windows can be divided into several categories, such as thermochromic, electrochromic, and photochromic. Among the different color-displaying technologies, thermochromic is considered to be the most robust, economical, and rationally motivated one due to its passive and zero energy input characteristics. Although color-displaying smart windows show good solar modulation ability ΔTsol, there is still some gap from the ideal smart window because color-displaying smart windows cannot change the infrared emissivity. On the other hand, passive daytime radiative cooling is a newly discovered technology that assists in the cooling of the room by reflecting sunlight and radiating heat to the cold outer space in the form of mid-infrared. Unlike traditional HVAC technologies such as air conditioning, radiative cooling technology does not require the use of external power and coolant. Due to their unique properties, radiative cooling materials are widely used as cooling sources, radiative cooling films, structural materials, and energy-saving coatings. However, the properties of radiative cooling materials limit their application as smart windows. First, most radiative cooling materials have low light transmittance, while high light transmittance is essential for the application of windows. Secondly, the mid-infrared emissivity of most radiative cooling materials cannot be changed, and the radiative cooling effect increases heating energy consumption in winter, which not only offsets the heating energy consumption saved in summer, but also leads to an increase in annual energy consumption. Therefore, radiative cooling materials are not advisable in winter, and their application in dynamic environments with seasonal changes is also limited. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects in the prior art and to provide a new type of thermochromic smart window with adjustable emissivity, which can dynamically adjust the thermal radiation and solar transmittance of different bands according to the changes in seasons and climate, so as to reduce the indoor temperature and save energy, which is beneficial to reduce building energy consumption, reduce the cooling load of buildings in summer and reduce heat loss in winter.

[0006] To achieve the above-mentioned purpose, the present invention provides a novel thermochromic smart window with adjustable emissivity, comprising a window frame, a glass component installed inside the window frame, the glass component comprising a glass substrate, a metal oxide coating for adjusting the glass substrate to have a low-radiation function in the mid-infrared region is deposited on one side of the glass substrate, the metal oxide coating is a layer of transparent indium tin oxide film, a solar energy regulating high-radiation part is installed on the other side of the glass substrate, the solar energy regulating high-radiation part comprises a first polyethylene layer, a hydroxypropyl cellulose hydrogel layer is installed on the upper part of the first polyethylene layer, the hydroxypropyl cellulose hydrogel layer is also installed with a second polyethylene layer, and the hydroxypropyl cellulose hydrogel layer is wrapped in the middle by the first polyethylene layer and the second polyethylene layer.

[0007] Preferably, a first rotating shaft is installed at the upper portion of the window frame, and a second rotating shaft is installed at the lower portion of the window frame, and the window frame can rotate forward and backward around the first rotating shaft and the second rotating shaft.

[0008] Preferably, the first polyethylene layer and the second polyethylene layer have high transparency and good chemical stability in the visible light, near infrared and mid-infrared bands.

[0009] Preferably, the hydroxypropyl cellulose hydrogel layer has good solar modulation capability. Below its transition temperature, the hydroxypropyl cellulose hydrogel layer has a high degree of transparency; once the temperature exceeds its transition temperature, the hydroxypropyl cellulose hydrogel layer will become opaque and block sunlight.

[0010] Preferably, the hydroxypropyl cellulose hydrogel layer has a very high mid-infrared emissivity.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] The present invention is provided with a window frame, wherein a glass component is installed inside the window frame, wherein the glass component comprises a glass substrate, wherein a metal oxide coating for adjusting the glass substrate to have a low radiation function in the mid-infrared region is deposited on one side of the glass substrate, wherein the metal oxide coating is a layer of transparent indium tin oxide film, wherein a solar energy regulating high radiation part is installed on the other side of the glass substrate, wherein the solar energy regulating high radiation part comprises a first polyethylene layer, wherein a hydroxypropyl cellulose hydrogel layer is installed on the upper part of the first polyethylene layer, wherein the hydroxypropyl cellulose hydrogel layer is further installed with a second polyethylene layer, wherein the hydroxypropyl cellulose hydrogel layer is wrapped between the first polyethylene layer and the second polyethylene layer, wherein the metal oxide coating has a low radiation function in the mid-infrared region and can block the conduction of thermal radiation, wherein the first polyethylene layer and the second polyethylene layer can prevent the hydroxypropyl cellulose hydrogel layer from drying out, wherein the hydroxypropyl cellulose hydrogel layer has high transparency below its transition temperature and can be easily penetrated by sunlight, wherein once the temperature exceeds its transition temperature, the hydroxypropyl cellulose hydrogel layer will become opaque and block sunlight, and wherein the hydroxypropyl cellulose hydrogel layer has high The window frame of the present invention is designed to be flippable to meet the different needs of summer and winter. In summer, the high-radiation part of the solar energy regulation faces the outdoors and the metal oxide coating faces the indoors, so that the heat is mainly released to the outer space in the form of mid-infrared. In the morning and evening, the window will remain transparent to meet the lighting needs, and become opaque at noon to block the heating of the room by the sun. Due to the combination of radiation cooling and sunlight regulation effects, the room will maintain a lower temperature. In winter, the metal oxide coating faces the outdoors and the high-radiation part of the solar energy regulation faces the indoors. The indoor heat cannot be transferred to the outdoors through thermal radiation, preventing heat loss. At the same time, the bright transparent window can also allow the sun to heat the room and reduce heating energy consumption. The present invention can dynamically adjust the thermal radiation and solar transmittance of different bands according to the changes in seasons and climate, so as to reduce the indoor temperature and save energy consumption, which is beneficial to reducing building energy consumption, reducing the cooling load of the building in summer and reducing heat loss in winter. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 This is a schematic diagram of the overall structure of a novel thermochromic smart window with adjustable emissivity provided by the present invention;

[0015] Figure 2 It is a schematic diagram of the decomposed structure of a glass component of a novel thermochromic smart window with adjustable emissivity provided by the present invention;

[0016] Figure 3 It is a schematic diagram of the working principle of a novel thermochromic smart window with adjustable emissivity provided by the present invention in summer and winter;

[0017] Figure 4 It is a schematic diagram of ultraviolet light, visible light and near infrared spectra of a novel thermochromic smart window with adjustable emissivity provided by the present invention at 20°C and 60°C;

[0018] Figure 5 It is a schematic diagram of the transmission spectra of polyethylene and hydroxypropyl cellulose hydrogels in the range of 6-16 μm;

[0019] Figure 6 It is a schematic diagram of the emissivity spectrum of the high emissivity side and the low emissivity side of a novel thermochromic smart window with adjustable emissivity provided by the present invention in different states;

[0020] Figure 7 It is a schematic diagram of infrared images of a new type of thermochromic smart window with adjustable emissivity provided by the present invention at a low emissivity side and a high emissivity side at different temperatures;

[0021] Figure 8 The air temperature curves of thermochromic smart windows, ordinary low-emissivity glass, hydroxypropyl cellulose hydrogel, ordinary glass and ambient temperature in an outdoor energy-saving effect experiment in summer in Singapore;

[0022] Fig. 9 This is the temperature difference curve between thermochromic smart windows and ordinary glass in an outdoor energy-saving effect experiment in summer in Singapore;

[0023] Fig.10 It is the air temperature curve of thermochromic smart windows, ordinary low-emissivity glass, hydroxypropyl cellulose hydrogel, ordinary glass and ambient temperature in Jinan winter outdoor energy-saving effect experiment;

[0024] Fig.11 This is the temperature difference curve between thermochromic smart windows and ordinary glass in Jinan's winter outdoor energy-saving effect experiment.

[0025] Included in the figure are:

[0026] 1-window frame, 2-glass component, 21-glass substrate, 3-metal oxide coating, 4-solar energy regulating high radiation part, 41-first polyethylene layer, 42-hydroxypropyl cellulose hydrogel layer, 43-second polyethylene layer, 11-first rotating shaft, 12-second rotating shaft. DETAILED DESCRIPTION

[0027] The technical scheme in this embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in this embodiment of the present invention. Obviously, the described embodiment is one embodiment of the present invention, not all embodiments of the present invention. Based on this embodiment of the present invention, all other embodiments of the present invention obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Please refer to Figures 1 to 3 The present invention provides a novel thermochromic smart window with adjustable emissivity, comprising a window frame 1, wherein a glass assembly 2 is arranged inside the window frame 1, wherein the glass assembly 2 comprises a glass substrate 21, wherein a metal oxide coating 3 for adjusting the glass substrate 21 to have a low radiation function in the mid-infrared region is deposited on one side of the glass substrate 21, wherein the metal oxide coating 3 is a layer of transparent indium tin oxide film, wherein a solar energy regulating high radiation part 4 is arranged on the other side of the glass substrate 21, wherein the solar energy regulating high radiation part 4 comprises a first polyethylene layer 41, wherein a hydroxypropyl cellulose hydrogel layer 42 is arranged on the upper part of the first polyethylene layer 41, wherein the hydroxypropyl cellulose hydrogel layer 42 is further provided with a second polyethylene layer 43, wherein the hydroxypropyl cellulose hydrogel layer 42 is wrapped in the middle by the first polyethylene layer 41 and the second polyethylene layer 43.

[0029] The glass substrate 21 is an important component of the glass assembly 2 and serves as a mechanical support layer for the thermochromic smart window. The metal oxide coating 3 has a low radiation function in the mid-infrared region and can block the conduction of thermal radiation. The first polyethylene layer 41 and the second polyethylene layer 43 wrap the hydroxypropyl cellulose hydrogel layer 42 in the middle. The first polyethylene layer 41 and the second polyethylene layer 43 have high transparency and good chemical stability in the visible light, near infrared and mid-infrared bands. Therefore, the first polyethylene layer 41 and the second polyethylene layer 43 are used to prevent the hydroxypropyl cellulose hydrogel layer 42 from drying out. The hydroxypropyl cellulose hydrogel layer 42 contains a large amount of water. The hydrogel layer 42 is a core component of the solar energy regulating high radiation part 4. The hydroxypropyl cellulose hydrogel layer 42 has good solar modulation ability. The hydroxypropyl cellulose hydrogel layer 42 has high transparency below its transition temperature, and sunlight can easily penetrate. Once the temperature exceeds its transition temperature, the hydroxypropyl cellulose hydrogel layer 42 will become opaque and block sunlight. Since water has extremely high mid-infrared emissivity, the hydroxypropyl cellulose hydrogel layer 42 also has high radiation function and has a very high mid-infrared emissivity. The thermochromic smart window combines the above two functional characteristics, can automatically adjust the transmittance of sunlight, and achieve good mid-infrared emissivity switching capability.

[0030] Please refer to Figure 1 A first rotating shaft 11 is installed at the upper part of the window frame 1, and a second rotating shaft 12 is installed at the lower part of the window frame 1. The window frame 1 can rotate forward and backward around the first rotating shaft 11 and the second rotating shaft 12.

[0031] Please refer to Figure 1 and Figure 3 The window frame 1 of the present invention is designed to be flippable to meet different needs in summer and winter. In summer, the solar energy regulating high radiation part 4 faces outdoors and the metal oxide coating 3 faces indoors, so that heat is mainly released to the outer space in the form of mid-infrared. In the morning and evening, the window will remain transparent to meet the lighting needs, and become opaque at noon to block the sunlight from heating the room. Due to the combination of radiation cooling and sunlight regulation effects, the room will maintain a lower temperature. In winter, the metal oxide coating 3 faces outdoors and the solar energy regulating high radiation part 4 faces indoors. The heat in the room cannot be transferred to the outdoors through thermal radiation, preventing heat loss. At the same time, the bright transparent window can also allow sunlight to heat the room and reduce heating energy consumption.

[0032] The light transmittance Tlum of the thermochromic smart window is 71.2%, and the dimming capability ΔTsol is 62.6%. The mid-infrared emissivity on both sides of the thermochromic smart window also has significant differences, with the solar regulation high radiation part 4 side being 0.95 and the metal oxide coating 3 side being 0.4.

[0033] In indoor and outdoor experiments, the thermochromic smart windows showed excellent energy-saving performance. In indoor and outdoor experiments in summer, the thermochromic smart windows achieved a temperature drop of about 30°C compared with ordinary glass windows. The performance of the thermochromic smart windows makes it a feasible way to achieve efficient building energy conservation throughout the year.

[0034] like Figure 4 As shown, the ultraviolet light, visible light and near infrared spectra of the thermochromic smart window at 20°C and 60°C are respectively shown. At low temperature (20°C), the transmittance of the thermochromic smart window is as high as 71.2%. Due to the infrared absorption characteristics of the metal oxide coating 3, the infrared spectrum with a wavelength above 1400nm is completely blocked. In addition, the thermochromic smart window has a good transmittance adjustment ability Tlum of 62.6% and a sunlight adjustment ability ΔTsol of 40.0%.

[0035] like Figure 5The figure shows the transmission spectra of polyethylene and hydroxypropyl cellulose hydrogel in the range of 6-16 μm. It can be observed that within the radiation cooling window (8-13 μm), polyethylene exhibits a high transmission of up to 80%, and hydroxypropyl cellulose hydrogel exhibits a transmission of about 50%. Polyethylene has high infrared transparency, which enables hydroxypropyl cellulose hydrogel to effectively release heat into space.

[0036] like Figure 6 As shown, the emissivity spectra of the high emissivity side and the low emissivity side in different states are shown. In both the cold and hot states, the high emissivity side has a higher emissivity of up to 0.95, while the emissivity of the low emissivity side is 0.35, which is significantly lower than the ordinary glass of 0.88. Therefore, it can be concluded that the window has the ability to directionally control mid-infrared radiation.

[0037] like Figure 7 As shown, infrared images of the low emissivity side and the high emissivity side at different temperatures are shown. The results show that the temperature on the high emissivity side is higher than the background temperature, and the temperature on the low emissivity side is lower than the background temperature. This temperature difference is caused by the difference in mid-infrared emissivity on both sides of the window. Since the mid-infrared emissivity of the high emissivity side is 0.95, which is higher than the mid-infrared emissivity of the background of 0.88, its infrared radiation intensity is higher than the background, so the high emissivity side looks hotter than the background. On the other hand, the mid-infrared emissivity of the low emissivity side is 0.35, which is lower than the mid-infrared emissivity of the background of 0.88, so the low emissivity side emits less infrared radiation and looks cooler than the background.

[0038] like Figure 8 and Fig. 9 The figure shows the temperature readings and temperature differences of thermochromic smart windows, ordinary low-emissivity glass, hydroxypropyl cellulose hydrogel and ordinary glass in the outdoor energy-saving effect experiment in summer in Singapore. Thermochromic smart windows have significant energy-saving performance, and the room with thermochromic smart windows has the lowest indoor temperature among the four rooms during the day. It is worth mentioning that from 12:00 to 15:00, the temperature difference between the thermochromic smart window room and the ordinary glass window room reached 27.5℃. At the same time, the temperature of the thermochromic smart window room was also 9℃ lower than the traditional hydroxypropyl cellulose hydrogel room and 20℃ lower than the ordinary low-emissivity glass room, indicating that the thermochromic smart window has a high solar modulation ability and good mid-infrared emissivity switching ability, and has good energy-saving performance.

[0039] like Fig.10 and Fig.11The figure shows the temperature readings and temperature differences of thermochromic smart windows, ordinary low-emissivity glass, hydroxypropyl cellulose hydrogel and ordinary glass in the winter outdoor energy-saving effect experiment in Jinan. At night in winter, the indoor temperature difference of ordinary low-emissivity glass rooms is the highest at 15°C throughout the day, the indoor temperature difference of thermochromic smart window rooms is the second highest at 13.5°C throughout the day, and the indoor temperature difference of ordinary glass window rooms is the lowest at 12.5°C throughout the day. This experiment or observation proves that thermochromic smart windows have better energy-saving performance than ordinary glass windows throughout the day in winter, which further proves the energy-saving performance of thermochromic smart windows.

[0040] A hydroxypropyl cellulose hydrogel layer 42 is filled between the first polyethylene layer 41 and the second polyethylene layer 43, and a metal oxide coating 3 with low radiation function is deposited on the glass substrate 21 to make a new type of thermochromic smart window with adjustable emissivity. The thermochromic smart window has achieved satisfactory performance in both solar transmittance regulation and mid-infrared emissivity switching. The thermochromic smart window shows a high transmittance Tlum of 71% at room temperature and has a good luminescence regulation ability of 62% when heated. In addition, the hydroxypropyl cellulose hydrogel layer 42 shows an extremely high mid-infrared emissivity of 0.95. Due to the good solar transmittance regulation ability and unique mid-infrared emissivity switching characteristics, the thermochromic smart window has a daytime temperature drop of about 30°C in summer compared with ordinary glass. At the same time, the thermochromic smart window also shows satisfactory energy-saving capabilities in winter. In summary, combining the advantages of the metal oxide coating 3 with low mid-infrared emission and the thermochromic hydroxypropyl cellulose hydrogel layer 42 with high and medium infrared emissivity, the thermochromic smart window plays a great role in improving the sustainability of buildings.

[0041] In summary, the beneficial effects of the present invention are:

[0042] The metal oxide coating 3 has a low radiation function in the mid-infrared region and can block the conduction of thermal radiation. The first polyethylene layer 41 and the second polyethylene layer 43 can prevent the hydroxypropyl cellulose hydrogel layer 42 from drying out. The hydroxypropyl cellulose hydrogel layer 42 has high transparency below its transition temperature and can easily penetrate sunlight. Once the temperature exceeds its transition temperature, the hydroxypropyl cellulose hydrogel layer 42 will become opaque and block sunlight. The hydroxypropyl cellulose hydrogel layer 42 has a high radiation function and a high mid-infrared emissivity. Combining the above two functional characteristics, the transmittance of sunlight can be automatically adjusted and a good mid-infrared emissivity switching capability can be achieved. The window frame 1 of the present invention is designed to be flippable to meet the different needs of summer and winter. In summer, the solar energy adjusts the high radiation part. The metal oxide coating 4 faces the outdoors and the metal oxide coating 3 faces the indoors, so that heat is mainly released to the outer space in the form of mid-infrared. In the morning and evening, the window will remain transparent to meet the lighting needs, and become opaque at noon to block the heating of the room by the sunlight. Due to the combination of radiation cooling and sunlight regulation effects, the room will maintain a lower temperature; in winter, the metal oxide coating 3 faces the outdoors and the solar energy regulation high radiation part 4 faces the indoors, the indoor heat cannot be transferred to the outdoors through thermal radiation, thereby preventing heat loss. At the same time, the bright transparent window can also allow the sunlight to heat the room and reduce heating energy consumption. The present invention can dynamically adjust the thermal radiation and solar transmittance of different bands according to the changes in seasons and climate, so as to reduce the indoor temperature and save energy consumption, which is beneficial to reducing building energy consumption, reducing the cooling load of the building in summer and reducing heat loss in winter.

Claims

1. A novel thermochromic smart window with adjustable emissivity, comprising a window frame (1), characterized in that: A glass component (2) is installed inside the window frame (1), and the glass component (2) includes a glass substrate (21), and a metal oxide coating (3) for adjusting the glass substrate (21) to have a low radiation function in the mid-infrared region is deposited on one side of the glass substrate (21), and the metal oxide coating (3) is a layer of transparent indium tin oxide film; a solar energy regulating high radiation part (4) is installed on the other side of the glass substrate (21), and the solar energy regulating high radiation part (4) includes a first polyethylene layer (41), and a hydroxypropyl cellulose hydrogel layer (42) is installed on the upper part of the first polyethylene layer (41), and the hydroxypropyl cellulose hydrogel layer (42) is also installed with a second polyethylene layer (43), and the hydroxypropyl cellulose hydrogel layer (42) is wrapped in the middle by the first polyethylene layer (41) and the second polyethylene layer (43); The upper part of the window frame (1) is provided with a first rotating shaft (11), and the lower part of the window frame (1) is provided with a second rotating shaft (12); the window frame (1) can rotate forward and reverse around the first rotating shaft (11) and the second rotating shaft (12); The first polyethylene layer (41) and the second polyethylene layer (43) have high transparency and good chemical stability in the visible light, near infrared and mid-infrared bands; The hydroxypropyl cellulose hydrogel layer (42) has good solar modulation ability. Below its transition temperature, the hydroxypropyl cellulose hydrogel layer (42) has a high degree of transparency; once the temperature exceeds its transition temperature, the hydroxypropyl cellulose hydrogel layer (42) will become opaque and block sunlight; The metal oxide coating (3) has a low radiation function in the mid-infrared region and can block the conduction of thermal radiation; the hydroxypropyl cellulose hydrogel layer (42) has a high radiation function and a very high mid-infrared emissivity, combining the low radiation function with the high radiation function, and can automatically adjust the transmittance of sunlight and achieve a good mid-infrared emissivity switching capability; The light transmittance Tlum of the thermochromic smart window is 71.2%, and the dimming capability ΔTsol is 62.6%; the mid-infrared emissivity of the metal oxide coating (3) is 0.4, and the mid-infrared emissivity of the solar energy regulating high radiation part (4) is 0.95; The window frame (1) can be flipped to meet different needs in summer and winter. In summer, the solar energy regulating high radiation part (4) faces the outdoors and the metal oxide coating (3) faces the indoors, so that heat is mainly released to outer space in the form of mid-infrared. In winter, the metal oxide coating (3) faces the outdoors and the solar energy regulating high radiation part (4) faces the indoors, so that indoor heat cannot be transferred to the outdoors through thermal radiation, thereby preventing heat loss.

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