Smart Window Based on Angular-Selective Absorption of Solar Radiation with Guest–Host Liquid Crystals

In this study, we analyzed angular-selective absorption in a guest–host liquid crystal (GHLC) cell for its application in smart windows. For reducing the energy consumption, angular-selective absorption is desired because the light transmitted through windows during the daytime is predominantly incident obliquely from direct sunlight. Owing to the absorption anisotropy of guest dichroic dyes, a GHLC cell can absorb the obliquely incident light, while allowing people to see through windows in a normal view. Therefore, the cell can provide a comfortable environment for occupants, and reduce the energy required for cooling by blocking the solar heat incident from the oblique direction. The GHLC cell can be switched between the transparent and opaque states for a normal view. The rising (falling) time was 6.1 (80.5) ms when the applied voltage was 10 V.

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Reverse Mode Polymer Dispersed Liquid Crystal-based Smart Windows: A Progress Report

Recent Progress in Materials ◽

10.21926/rpm.2104044 ◽

2021 ◽

Vol 03 (04) ◽

pp. 1-1

Author(s):

Yang Zhang ◽

◽

Jiawen Chen ◽

Xiaowen Hu ◽

Wei Zhao ◽

...

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Material Design ◽

Smart Window ◽

Smart Windows ◽

Polymer Dispersed Liquid Crystal ◽

Reverse Mode ◽

Polymer Dispersed ◽

Recent Developments ◽

Polymer Stabilized

The reverse mode polymer dispersed liquid crystal (PDLC) is an emerging smart window technology. Unlike traditional PDLCs, a reverse mode PDLC can be transparent and opaque in the absence and presence of an external electric field. This report provides a brief introduction to several reverse modes PDLC smart window technologies, focusing on polymer-stabilized liquid crystals (PSLCs). The systems based on electrohydrodynamic instability (EHDI) of liquid crystals have also been discussed. The working principles, mode of material design, and recent developments are presented for each technology. The current obstacles have also been pointed out. The prospects of smart windows have also been presented.

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Nano-Sized Fine Droplets of Liquid Crystals for Optical Application

MRS Proceedings ◽

10.1557/proc-457-89 ◽

1996 ◽

Vol 457 ◽

Cited By ~ 6

Author(s):

Shiro Matsumoto ◽

Marthe Houlbert ◽

Takayoshi Hayashi ◽

Ken-ichi Kubodera

Keyword(s):

Liquid Crystal ◽

Phase Separation ◽

Liquid Crystals ◽

Electric Field ◽

Applied Voltage ◽

Applied Electric Field ◽

Uv Curing ◽

Infrared Region ◽

High Transparency ◽

Power Change

ABSTRACTNano-sized fine droplets of liquid crystal (LC) were obtained by phase separation of nematic LC in UV curing polymer. The polymer composite had a high transparency in the infrared region. The fine droplets responded to an electric field causing a change in birefringence. Output power change was brought about by the generated retardation between two polarizations, parallel and perpendicular to the applied electric field. This differs from the composite containing much larger droplets, where output depends on the degree of scattering. The birefringence changed by 0.001 at the applied voltage of 7.5 V/μm.

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Smart Electrochromic Windows to Enhance Building Energy Efficiency and Visual Comfort

Energies ◽

10.3390/en13061449 ◽

2020 ◽

Vol 13 (6) ◽

pp. 1449 ◽

Cited By ~ 11

Author(s):

Alessandro Cannavale ◽

Ubaldo Ayr ◽

Francesco Fiorito ◽

Francesco Martellotta

Keyword(s):

Energy Efficiency ◽

Energy Consumption ◽

Relevant Literature ◽

Management Strategies ◽

Building Energy Efficiency ◽

Visual Comfort ◽

Confined Space ◽

Smart Window ◽

Smart Windows ◽

The One

Electrochromic systems for smart windows make it possible to enhance energy efficiency in the construction sector, in both residential and tertiary buildings. The dynamic modulation of the spectral properties of a glazing, within the visible and infrared ranges of wavelengths, allows one to adapt the thermal and optical behavior of a glazing to the everchanging conditions of the environment in which the building is located. This allows appropriate control of the penetration of solar radiation within the building. The consequent advantages are manifold and are still being explored in the scientific literature. On the one hand, the reduction in energy consumption for summer air conditioning (and artificial lighting, too) becomes significant, especially in "cooling dominated" climates, reaching high percentages of saving, compared to common transparent windows; on the other hand, the continuous adaptation of the optical properties of the glass to the changing external conditions makes it possible to set suitable management strategies for the smart window, in order to offer optimal conditions to take advantage of daylight within the confined space. This review aims at a critical review of the relevant literature concerning the benefits obtainable in terms of energy consumption and visual comfort, starting from a survey of the main architectures of the devices available today.

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Effect of Smart Glazing Window on Energy Consumption inside Office Building

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1008.72 ◽

2020 ◽

Vol 1008 ◽

pp. 72-83

Author(s):

Asmaa Mohammed Nageib ◽

Abbas Mohamed El-Zafarany ◽

Fatma Osman Mohamed ◽

Mohamed Helmy El-Hefnawy

Keyword(s):

Energy Efficiency ◽

Energy Consumption ◽

Solar Radiation ◽

Climatic Conditions ◽

Office Buildings ◽

Smart Windows ◽

Upper Egypt ◽

Natural Lighting ◽

North East ◽

Office Rooms

The office buildings in Egypt, especially in Upper Egypt, reflect serious problems in achieving for energy efficiency as a result of increasing the use of mechanical refrigeration devices in office rooms, due to solar radiation and rising summer temperatures in recent years. Smart windows can play an important role in reducing significantly the energy consumption and maintaining energy inside buildings, also helps to control incoming solar radiation in order to minimize solar gain, especially in summer as well as ensuring the best natural lighting conditions without glare inside a room. This paper aims to evaluate the most efficient daylight and thermal performance of various types of the smart glazing and its impact on the energy consumption in the climatic conditions of one of the office buildings (Diwan governorate) in Sohag governorate as one of Upper Egypt governorates, with determining the best smart glass types for efficient use of energy. The paper follows the theoretical, applied, by studying types of smart glazing and their relation to achieving the energy efficiency. Then using (Energy Plus) simulation tool, which has been used in utilizing its modeling orientation (Design Builder) to study using types of smart glazing on the model of an office room in Building of Diwan governorate of Sohag in the four different orientations (North, East, South and West), when window-to-floor ratios (WFRs) (8%, 16%, 24% and 32%). The paper ends with a presentation of the most important results, recommendations and determination the best types of smart glass that provides energy, daylight without glare and providing greater comfort to users.

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Energy Consumption Verification of SPD Smart Window, Controllable According to Solar Radiation in South Korea

Energies ◽

10.3390/en13215643 ◽

2020 ◽

Vol 13 (21) ◽

pp. 5643

Author(s):

Yujin Ko ◽

Hyogeun Oh ◽

Hiki Hong ◽

Joonki Min

Keyword(s):

Energy Consumption ◽

Suspended Particle ◽

Electricity Consumption ◽

Energy Requirements ◽

Weather Data ◽

Smart Window ◽

Smart Windows ◽

Reduce Energy Consumption ◽

The City ◽

Made In

Between 60% and 70% of the total energy load of a house or office occurs through the exteriors of the building, and in the case of offices, heat loss from windows and doors can approach 40%. A need for glass that can artificially control the transmittance of visible light has therefore emerged. Smart windows with suspended particle device (SPD) film can reduce energy consumption by responding to environmental conditions. To measure the effect of SPD windows on the energy requirements for cooling and heating in Korea, we installed a testbed with SPD windows. With TRNSYS18, the comparison between measurements and simulation has been made in order to validate the simulation model with respect to the modeling of an SPD window. Furthermore, the energy requirements of conventional and SPD-applied windows were compared and analyzed for a standard building that represented an actual office building. When weather for the city of Anseong and a two-speed heat pump were used to verify the simulation, the simulated electricity consumption error compared with the testbed was −1.0% for cooling and −0.9% for heating. The annual electricity consumption error was −0.9%. When TMY2 Seoul weather data were applied to the reference building, the decrease in electricity consumption for cooling in the SPD model compared with the non-SPD model was 29.1% and the increase for heating was 15.8%. Annual electricity consumption decreased by 4.1%.

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Smart Window with Active-Passive Hybrid Control

Materials ◽

10.3390/ma13184137 ◽

2020 ◽

Vol 13 (18) ◽

pp. 4137

Author(s):

Heng-Yi Tseng ◽

Li-Min Chang ◽

Kuan-Wu Lin ◽

Cheng-Chang Li ◽

Wan-Hsuan Lin ◽

...

Keyword(s):

Liquid Crystal ◽

Voltage Pulse ◽

Hybrid Control ◽

Cholesteric Liquid Crystal ◽

Low Frequency ◽

Operating Mode ◽

Smart Window ◽

Smart Windows ◽

Dichroic Dye ◽

Scattering State

Dimming and scattering control are two of the major features of smart windows, which provide adjustable sunlight intensity and protect the privacy of people in a building. A hybrid photo- and electrical-controllable smart window that exploits salt and photochromic dichroic dye-doped cholesteric liquid crystal was developed. The photochromic dichroic dye causes a change in transmittance from high to low upon exposure to sunlight. When the light source is removed, the smart window returns from colored to colorless. The salt-doped cholesteric liquid crystal can be bi-stably switched from transparent into the scattering state by a low-frequency voltage pulse and switched back to its transparent state by a high-frequency voltage pulse. In its operating mode, an LC smart window can be passively dimmed by sunlight and the haze can be actively controlled by applying an electrical field to it; it therefore exhibits four optical states—transparent, scattering, dark clear, and dark opaque. Each state is stable in the absence of an applied voltage. This smart window can automatically dim when the sunlight gets stronger, and according to user needs, actively adjust the haze to achieve privacy protection.

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A Smart Window for Angular Selective Filtering of Direct Solar Radiation

Journal of Solar Energy Engineering ◽

10.1115/1.4044059 ◽

2019 ◽

Vol 142 (1) ◽

Cited By ~ 5

Author(s):

Rustam S. Zakirullin

Keyword(s):

Solar Radiation ◽

Light Transmission ◽

Slope Angle ◽

Optical Filter ◽

Time Of Day ◽

Direct Solar Radiation ◽

Smart Window ◽

Smart Windows ◽

Solar Radiation Intensity ◽

Parallel Strips

Thin-film grating coatings are proposed for smart windows to angular selective filtering of solar radiation. The gratings are formed by absorptive, reflective, or scattering parallel strips (made of chromogenic or other materials) alternating with directionally transmissive strips (untreated surface of pure glass) on two surfaces of the window pane(s). The smart window with grating optical filter has angular selective light transmission and partially or completely blocks the direct solar radiation in a preset angular range and transmits the scattered and reflected radiation without using the daylight redistribution devices. The results of numerical simulation and experimental confirmation of optimum slope angle of the strips on the pane(s), their widths, and relative position on two surfaces to minimize the directional light transmission of the window at the preset date and time of day taking into account orientation of the window to the cardinal, the latitude of the building, and the seasonal and daily distribution of the solar radiation intensity are demonstrated.

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Tunable Optical Filter with Variable Bandwidth Based on Cholesteric Liquid Crystal

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.181-182.273 ◽

2011 ◽

Vol 181-182 ◽

pp. 273-276

Author(s):

Shi Chao Zhang ◽

Yu Hua Huang

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Incident Light ◽

Cholesteric Liquid Crystal ◽

Optical Filter ◽

Tunable Filter ◽

Cholesteric Liquid Crystals ◽

Central Wavelength ◽

Variable Bandwidth ◽

Tunable Optical Filter

An optical tunable filter with variable bandwidth has been demonstrated using two cholesteric liquid crystals. The incident light was first reflected by the first cholesteric liquid crystal and then by the second one. By rotating the two cholesteric liquid crystals simultaneously, the central wavelength can be tuned. By fixing one of the cholesteric liquid crystals and rotating the other one, the bandwidth of the tunable filter can be varied. The central wavelength of the tunable optical filter can be tuned from 513.4 nm to 576.8 nm and the bandwidth is varied from 10 nm to 80 nm. This property will allow it to be widely used in many fields, including optical communications and multispectral and hyperspectral imaging systems.

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Holographic Characteristics of Photopolymers Containing Different Mixtures of Nematic Liquid Crystals

Polymers ◽

10.3390/polym11020325 ◽

2019 ◽

Vol 11 (2) ◽

pp. 325 ◽

Cited By ~ 1

Author(s):

Sandra Fenoll ◽

Francisco Brocal ◽

José David Segura ◽

Manuel Ortuño ◽

Augusto Beléndez ◽

...

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Light Intensity ◽

Electric Field ◽

Diffraction Efficiency ◽

Applied Voltage ◽

Nematic Liquid Crystals ◽

Variable Electric Field ◽

Polymer Dispersed Liquid Crystal ◽

Polymer Dispersed

A holographic polymer dispersed liquid crystal (HPDLC) is used to record holographic diffraction gratings. Several mixtures of nematic liquid crystals (LC) are used as components of the HPDLC to evaluate their influence in static and dynamic basic properties. The diffraction efficiency obtained in the reconstruction of the holograms is evaluated to compare the influence of the different LC. Additionally, the samples are exposed to a variable electric field and the diffracted light intensity as a function of the applied voltage is measured to evaluate the influence of the LC. The results obtained show significant differences depending on the LC incorporated to the photopolymer.

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Enhanced Bandwidth Broadening of Infrared Reflector Based on Polymer Stabilized Cholesteric Liquid Crystals with Poly(N-vinylcarbazole) Used as Alignment Layer

Polymers ◽

10.3390/polym13142238 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2238

Author(s):

Limin Zhang ◽

Qiumei Nie ◽

Xiao-Fang Jiang ◽

Wei Zhao ◽

Xiaowen Hu ◽

...

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Electric Field ◽

Cholesteric Liquid Crystal ◽

Critical Role ◽

Cholesteric Liquid Crystals ◽

Smart Window ◽

Alignment Layer ◽

Thermal And Electrical Properties ◽

Polymer Stabilized

Alignment layer plays a critical role on liquid crystal (LC) conformation for most LC devices. Normally, polyimide (PI) or polyvinyl alcohol (PVA), characterized by their outstanding thermal and electrical properties, have been widely applied as the alignment layer to align LC molecules. Here, we used a semi-conductive material poly(N-vinylcarbazole) (PVK) as the alignment layer to fabricate the cholesteric liquid crystal (CLC) device and the polymer-stabilized cholesteric liquid crystals (PSCLC)-based infrared (IR) reflectors. In the presence of ultraviolet (UV) irradiation, there are hole–electron pairs generated in the PVK layer, which neutralizes the impurity electrons in the LC–PVK junction, resulting in the reduction in the built-in electric field in the LC device. Therefore, the operational voltage of the CLC device switching from cholesteric texture to focal conic texture decreases from 45 V to 30 V. For the PSCLC-based IR reflectors with the PVK alignment layer, at the same applied electric field, the reflection bandwidth is enhanced from 647 to 821 nm, ranging from 685 to 1506 nm in the IR region, which makes it attractive for saving energy as a smart window.

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