Application research and development of the hottes

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Overview of application research and development of intelligent glass in building doors, windows and curtain walls

1. Overview

in recent years, glass curtain walls, glass roofs and glass structures, which are not only beautiful and novel, but also transparent, wind-proof and dust-proof, have become the remarkable characteristics of the era of modernist high-rise buildings. However, ordinary building glass can not automatically adjust its own performance to adapt to wind, rain, light and other environmental changes, which brings us a lot of inconvenience. In today's world, energy crisis, environmental pollution, global warming and other issues are becoming increasingly serious. When choosing architectural glass, people not only consider its aesthetic characteristics and appearance characteristics, but also pay more attention to its heat control, cooling cost and comfortable balance of internal sunlight projection. With the development of new buildings in the direction of intelligence, the "smart glass" smart window "which can dynamically adjust the light intensity and indoor temperature has quickly become a research hotspot in various countries

2。 Definition and classification of smart glass

smart glass is a glass device composed of glass materials, transparent plastics and other substrates and sensing materials, which can sense changes in the external environment and change its performance in real time. Under certain physical conditions, this device can stably and reversibly turn to spiders and moths for inspiration to change their own optical properties (color, reflectivity, transmittance, absorptivity, etc.) according to people's wishes. Therefore, it has the adjustability of light absorption and transmission, and can selectively absorb or reflect external thermal radiation and internal thermal diffusion

up to now, the preparation methods of smart glass can be roughly divided into two types: one is to make the inductive material into a film and compound it on the surface of inorganic glass or to mix it between two layers of ordinary glass; The second is to modify the glass body by using inductive materials. Relatively speaking, the smart glass obtained by glass body modification has complex process, high cost, few literature reports, and most of the publicly reported preparation methods are leading ones. The technical core of smart glass is the preparation and selection of sensing materials. Currently, the sensing materials that have been studied more are mainly divided into three categories: photochromic, electrochromic and thermotropic dimming

generally speaking, photochromic materials can be divided into organic (mainly including diarylethene, azo and related heterocyclic compounds) and inorganic (mainly silver halide system) according to the material type. Although photochromism has been discovered for more than 100 years, inorganic photochromic glass has high cost and complex processing technology, and organic photochromic glass is not resistant to high temperature, easy to fatigue and poor outdoor weather resistance. Moreover, most of these two categories of materials are not friendly to the environment, which limits its commercial application in the construction field

electrochromic materials can also be divided into inorganic materials and organic materials. Inorganic electrochromic materials are mainly transition metal oxides, such as W03, nb205, Ta2O5 and V205; Organic electrochromic materials mainly include organic heterocyclic compounds, conductive polymers, metal organic polymers and metal phthalein compounds, such as viologen, pivalin and polyaniline

these two kinds of materials have their own advantages and disadvantages, which have been introduced in many articles and will not be repeated here. With the development of nanotechnology, polymer/transition metal oxide nanocomposites with unique molecular structure and apparent synergistic effect have become a hot spot in the field of electrochromic materials. Thermotropic dimming materials can also be divided into inorganic (such as vanadium oxide) and organic (such as hydrogel, liquid crystal materials, polymer blends, polymer variable materials, etc.) according to the properties of the materials. According to the change of their optical properties with temperature, they can be divided into three types: thermoscattering, thermochromatic change and dual function. However, in order to make it widely used in building energy conservation, the phase transition temperature of thermochromic glass materials should be around room temperature (about 30 ℃), and there is no volume change during the phase transition process. Therefore, there are not many materials to choose from. At present, the research focus is mainly on phase separated thermoscattering polymers and doped V02 films

3。 New progress in smart glass application research

smart glass applied in the construction field can maximize the use of natural resources to achieve building energy conservation, reduce operating costs, and also improve the office environment and prevent peeping

electrochromic smart glass actual_ Equivalent to glass with adjustable curtains, it can be used in construction sites that need confidentiality or privacy protection. Researchers from the University of Tartu in Estonia spray the meter gel coating currently being repaired by nalega in Jiaxing, China, into the transparent glass to form a 5-10um thick coating in accordance with the verification regulations of extensometer. Under the action of electric field, the optical properties of the coating will change. This kind of smart glass can complete the transformation of "transparent glass" and "ground glass" in "an instant" under the control of power switch, The smart window made of it is as convenient as the curtain with electric control device

at present, countries all over the world attach great importance to building energy conservation. The thermal dimming film, which automatically adjusts the indoor temperature intelligently according to environmental changes, has become one of the active research fields in materials science and has been highly valued by researchers

most of the solar radiation energy is concentrated in the infrared band. When VO2 undergoes the transition between the monoclinic phase of low-temperature semiconductor and the tetragonal phase of high-temperature metal near 68 ℃, there is a sudden change in the light transmittance and reflectivity in the infrared band, and the change is reversible. In recent years, ivanp in Britain. Professor parkin et al. Doped a small amount of tungsten in V02 film to reduce the critical temperature of phase transition to near room temperature. They coated this adaptive temperature control intelligent material on the surface of door, window and curtain wall glass to form an intelligent glass that can automatically adjust the temperature, which has a good energy-saving effect

German researchers have developed intelligent sunscreen glass with self-regulation ability by mixing a layer of polymer microcapsule resin film with structural phase change characteristics in two layers of ordinary glass. When the temperature reaches a certain value, the glass of this sandwich structure changes from transparent to fuzzy, which isolates 30-50% of the solar heat, and the scattered light is still enough to keep the room bright; When the temperature drops, the calorific value layer will return to its original state, and the window glass will become clear and transparent again

with the development of science and technology, self powered color changing smart windows and smart power generation windows that skillfully combine the advantages of photovoltaic solar energy technology and electrochromic technology or thermal dimming technology have also begun to be researched and developed. Xuchunye's research group has developed a new self powered color changing glass by organically combining dye-sensitized solar cells and electrochromic window technology. This glass can absorb the sunlight shining on other surfaces and convert it into electrical energy. When using this part of electrical energy, it will change color by itself, so as to achieve the purpose of adjusting the intensity of light and beautifying the environment. Gaoyanfeng et al. Prepared large-size V02 films with critical phase change temperature in the low temperature zone by modifying V02 materials, and designed transparent smart windows that can self adjust heat transfer according to different ambient temperatures, and then upgraded them to smart power generation windows by installing solar cells on them. Such smart power generation windows have good phase change stability, which will help reduce heating Energy costs for lighting, cooling, etc

at the same time, new glass with dual functions of air conditioning and curtain also began to be developed and applied. Anna et al. Of Lawrence Berkeley National Laboratory in the United States have made a new "smart window" which is easy to independently control visible light and heat generating near-infrared light by using oxide Gugu tin nanocrystals and nickel oxide embedded in the glass matrix. By adjusting the voltage to change the structure of the nano products to block specific wavelengths, the optical properties of this smart glass can be switched between three states: fully transparent mode Selectively block the near-infrared light (heat) mode and the dark mode of preventing visible light and heat from entering the building at the same time. By dynamically controlling the visible light and heat through the glass windows, the light and dark can be controlled and the cold and heat can be adjusted, which can improve the living comfort of the building and reduce the energy consumption. The existing intelligent window products in the market are often expensive, slow response time, complex preparation process and poor quality. It is necessary to study new intelligent window systems to overcome these problems. Recently, Korean researchers found that the combination of polymer, ionic membrane and methanol solvent can produce cheap, stable and powerful smart glass. When the light is strong and the weather is hot, the glass will automatically darken and become completely opaque; When the sun is insufficient and the weather is cold, the glass can be switched to a completely transparent state in a few seconds, so that more sunlight can shine into the house and use solar energy to heat the house. By managing how much sunlight shines on the interior of the house, this new light control system provides a new option to save heating, cooling and lighting costs

4。 Current situation and trend of industrial development in order to meet the growing demand for building energy conservation, in recent years, the United States, Japan, Europe and other developed countries have invested a lot of human and financial resources to actively develop intelligent glass technology. Products have been commercialized in many fields, and industrialization has been basically realized in the field of all solid large-area electrochromic glass. China's research on smart glass is relatively weak. In recent years, although some universities and research institutes have done a lot of research work on smart glass materials and device manufacturing, there are few reports on industrialization. It is also necessary to do a good job in stability research, commercialization issues, in-depth development of new system and new varieties of color changing materials, etc

since the development of smart glass involves many scientific knowledge such as physics, materials, chemistry and film science, the theoretical research and practice are not very mature, and its popularization and application still need further theoretical and experimental research

at present, the development trend of smart glass follows the directions of all solid state, large area, intelligence, multifunction, low cost, energy conservation and environmental protection

1)) at present, most of the thin-film materials used are heavy metals or toxic organic compounds, which are of few types, not only expensive, but also harmful to the environment. With the attention paid to environmental protection by all countries in the world and the enhancement of people's awareness of environmental protection, it is a general trend to develop new high-performance intelligent materials with long life, low cost and good environmental friendliness

2) new intelligent glasses with excellent properties and diverse colors are prepared by various methods, such as doping, intercalation composite, sol-gel and LB film, giving full play to the different advantages of organic polymers and metal oxides

3) combine solar cell technology with smart glass technology to develop new smart windows with various functional characteristics such as daylighting, dimming, photocatalysis, concentrating, light storage, photoelectric conversion, thermoelectric conversion, etc., improve the intelligent level of its temperature control process, regulate the indoor temperature while adjusting the light, save electric energy and reduce the use of equipment

4) adopt advanced production and assembly process to meet the needs of large-scale and low-cost industrial production

it can be predicted that as people can foresee the practicality and appreciation of outdoor buildings, and as people have higher and higher requirements for the practicality and appreciation of outdoor buildings, intelligent glass has n=10

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