智能窗(smart window)是一种由基材(玻璃或其他透明材料等)和调光物质所组成的光学器件,它能在一定的物理化学因素(如光照、电磁辐照、电场、气体、温度)激发下,在太阳光谱的某些区段发生着色或褪色反应,引起调光物质光学特性改变,从而光谱选择性地吸收或反射太阳辐射,达到屏蔽紫外线、调节进入室内阳光强度和室内外的热交换、降低制冷制热能耗和减少碳排放等目的.根据其激励方式的不同,智能窗可分为热致色变、气致色变和电致色变三大类.二氧化钒(M/R相VO_2,简写为VO_2)热致色变型智能窗能够吸收90%以上的紫外线(如果添加紫外吸收剂,吸收率可达99%),在基本不影响可视光透过率的情况下,可以根据外界温度的变化,调节太阳光红外部分透过率.VO_2智能窗结构简单,近年来相关的应用基础和产业化开发均获得重要突破.本文从单层、多层、纳米复合等几种典型结构与其光学性能关系入手,综述了近年来VO_2智能窗和节能发电一体窗研究的主要进展和面临的问题.
Approximately 60% of all energy consumed in building sector is used for space heating, cooling, lighting and ventilation; therefore, energy-conserving measures should be implemented to decrease energy losses. Compared with other elements of the building envelope that separate the indoors from the outdoors (such as walls, roofs and fenestrations), windows are often considered less energy-efficient building components with high maintenance requirements. A large amount of energy is lost through windows, which are the weak links in buildings from an energy perspective, but these features must nevertheless be retained for indoor comfort, permeability and harmony between humans and nature. Smart window is an assembly of a substrate (glass or other transparent materials) and a light- adjusting material, which can change its transmittance via absorption or reflection of solar light with specific wavelength ranges under some physical or chemical stimuli such as light, irradiation, electricity, gas, temperature, etc. The smart window aims to reduce the heating/cooling energy consumption of buildings and CO2 emissions. According to stimulation mode, the smart window can be divided into electrochromic window (ECW), gasochromic window and thermochromic window (TCW). Vanadium dioxide (VO2) smart window is the main kind of TCW, which can absorb over 90% ultraviolet radiation (up to 99% by combination with other absorbents), and can adjust solar heat transmittance by response to environment temperature changes with almost constant visible light transmittance. In recent years, important breakthroughs in both fundamental studies and mass manufacture were reported successively on VO2 TCW. From historic viewpoint, the development of VO2 for the practical use was hindered seriously by several shortcomings, including unpopular color, high phase-transition temperature, weak thermal shield performance, low luminous transmittance and solar energy modulation ability. Among these issues, the low optical performanc