Smart windows that can modulate the transmission of sunlight entering the room can significantly reduce energy consumption. Herein, we provide a simple structure for smart windows which can modulate the transmittance of visible (vis) light actively by an external electric field and modulate the transmittance of near-infrared (NIR) light passively by temperature. The dual-band control of vis and NIR light are achieved by polymer-dispersed liquid crystal, vanadium dioxide (VO2), and Al-doped ZnO. The VO2 thin film plays two roles: NIR light control and conductive layer. There are four optical modulation modes for this kind of smart window, that is, (1) vis and NIR light passing mode, (2) vis light blocking and NIR light passing mode, (3) vis light passing and NIR light blocking mode, and (4) vis and NIR light blocking mode. The transmittance in the vis range (T lum) can be reversibly and actively modulated between 0.38 and 39.93%, and the transmittance in solar irradiation (T solar) can be reversibly and passively modulated between 42.32 and 9.95%. In the meantime, the response time (t on) decreases from 114.5 to 5.2 ms when the VO2 thin film changes from monoclinic to rutile phase. The electro-optical measurement indicates smart windows with featured fast response time, long stability, and independent modulation ability. Besides, a house model testing proves an indoor temperature cooling of 7.7 °C. Smart windows with simple structure, large area preparation, and outstanding modulation ability are promising in energy saving in buildings and automobiles.
droplets wrapped in thin polymer shells allow for normal scattering. [14] However, PDLCs require a lot of power to sustain high transparency. Polymer-stabilized LCs (PSLCs) require little power when in either the normal transparent or scattering state and, thus, have recently been preferred. [15] PDLCs and PSLCs scatter sunlight as do curtains, but exclude less solar energy. Compared to nematic LCs, cholesteric LCs (CLCs) afford circularly selective reflection because of the spatially periodic variation of the dielectric tensor in the helical structure. CLCs allow smart windows to reflect solar energy regardless of environmental status, thus saving energy. [16][17][18][19] Vanadium dioxide (VO 2 ) exhibits a typical metal-insulator transition (MIT) triggered by electricity, thermal radiation, THz-frequency waves, and strain, associated with significant changes in resistivity and the optical and magnetic properties. [20,21] Thermotropic VO 2 that modulates NIR light penetration has been used to fabricate smart windows and manage the indoor thermal environment. [22][23][24][25][26][27][28][29] However, the MIT of VO 2 occurs at 68 °C, thus far in excess of a comfortable temperature, greatly hampering VO 2 utilization. Here, we develop a dualstimulus-responsive, normally transparent, WVO-PSCLCs flexible smart window using thermally stable polymer stabilized CLCs (PSCLCs) and a flexible, thermotropic, tungsten-doped VO 2 hybrid thin layer. Transparency is electrically switchable, and the window significantly modulates NIR light penetration under ambient conditions, thus weakly reflecting NIR light at room temperature and extensively scattering penetrated NIR light at 55 °C. The window is very resistant to pressing and bending, facilitating real-world use.
Oil immersed shunt reactor is one of the most important reactive power compensation equipment in Ultra high voltage (UHV) long-distance power transmission and transformation system. When the oil immersed shunt reactor has potential defects, the vibration signal during operation will be different from that under normal condition, which is shown as different defect signals such as noise and abnormal temperature. Compared with traditional vibration sensor detection, acoustic detection and infrared detection realize non-contact detection, which is safer and does not require complex vibration sensor layout. If the two are combined, the detection efficiency can be greatly improved.In this paper, the acoustic characteristics and thermal distribution characteristics of oil immersed shunt reactors under different vibration modes are studied. Based on the beam forming sound source space positioning calculation method, after the integration of voiceprint and infrared image is completed, the acoustic imaging and infrared detection technology of reactor vibration is proposed to realize the simultaneous monitoring of reactor sound temperature state information, and improve the accuracy and rationality of defect identification. In addition, the design scheme of a prototype for on-site acoustic infrared detection of reactor vibration is proposed. The related results of this paper can provide technical support for the application of UHV oil immersed shunt reactor state assessment and diagnosis, and improve the level of equipment operation and maintenance.
In this paper, we reported a highly thermal stable YP‐11 polymer stabilized cholesteric liquid crystal (YP‐11 PSCT) for smart windows that can be electrically switched from transparent to opaque. The polymerization between photo‐sensitive monomers (RM 257) has been characterized using a polarized optical microscope (POM), which has been found to become much firmer and denser by raising the doping concentration. The 3D polymer matrices remarkably affect the electro‐optical performances of YP‐11 PSCT, and the cholesteric liquid crystals (Ch LCs) within polymer matrices were found merely able to be reversibly switched until the doping concentration of RM 257 was raised up to 3%. Specifically, the threshold voltage, raising time and decaying time of a 3% YP‐11 PSCT cell were determined as 22.908 V, 85.442 ms and 18.617 ms, respectively. The critical thermal‐stable temperature of the 3% YP‐11 PSCT was further evaluated using a hot stage and was confirmed as high as up to 100 °C. These findings in this paper will significantly contribute to the development of smart windows.
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