Two Articles
Smart window technology that can automatically adjust the amount of sunlight entering the room by changing the color of the window depending on the intensity of sunlight has been developed by a domestic research team.
The research team of Dr. Han Chi-hwan of Korea Institute of Energy Research (KIER) succeeded in developing a smart window technology which does not need power, by inserting a light absorbing layer that can generate electromotive force into an electrochromic device. This new smart window technology can lower prices by 30% to 50% or more, compared to existing products.
The light-sensitive automatic color conversion smart window technology combines solar cell technology and electrochromic technology. It can simultaneously solve the need for a separate power supply and high production costs which are disadvantages of existing electrochromic technology. In addition, it can control the intensity of sunlight and dramatically reduce the energy used for lighting by 30% to 40% or more as a future smart window technology.
Existing electrochromic smart window products were not revitalized in the market due to their expensive price and the difficult construction for connecting electric wiring to these windows. However, since the photosensitive automatic color conversion smart window technology contains a light absorbing layer in the device, there is no need for a separate power supply, and it can also reduce prices because it does not use expensive conductive glass during production.
The light-sensitive automatic color conversion smart window has better ability to block sunlight when it is stronger, so it can be applied to large buildings with high cooling costs by blocking visible light as well as IR light transmission in summer. In addition, this excellent technology does not require a separate power supply, and it can be applied to existing buildings, thus expanding the marketplace.
The research team has succeeded in developing not only the glass but also filming technology, and they are also making a product that can attach to and detach from existing window glasses. If the development of film-type products is successful, it is expected to expand not only to buildings, but also to various markets such as automobiles, ships, and aircraft.
Dr. Han Chi-hwan, researcher of the photovoltaics research department of KIER and the head of this project said, “As the government has established a road map that obligates zero-energy buildings starting in 2020, this photosensitive automatic color conversion smart window technology has the effect of blocking heat when sunlight is strong, so it can improve the energy efficiency when applied to a zero-energy building. It is also expected to contribute to the construction of a future smart city by combining solar cell technology and electrochromic technology into one.”
Caption for opening image: This technology can control the transmittance of light by automatically adjusting the intensity of sunlight. It can manufacture high-performance smart windows by applying low-cost material process can be applied and. (photochromic devices based on electrochromic device) Credit: Korea Institute of Energy Research (KIER)
Source: National Research Council of Science & Technology
Smart window technology that automatically changes color by sunlight
https://techxplore.com/news/2020-05-smart-window-technology-automatically-sunlight.html
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Smart windows that automatically change colors depending on the intensity of sunlight are gaining attention as they can reduce energy bills by blocking the sun’s visible rays during summer. But what about windows that change colors depending on the humidity outside during the monsoon season or on hot days of summer?
Credit: Pohang University of Science & Technology (POSTECH)
Recently, a Korean research team has developed the source technology for smart windows that change colors according to the amount of moisture, without needing electricity.
The joint research team comprised of Professor Junsuk Rho of the departments of mechanical and chemical engineering, Jaehyuck Jang and Aizhan Ismukhanova of the chemical engineering department at POSTECH, and Professor Inkyu Park of KAIST’s department of mechanical engineering. Together, they successfully developed a variable color filter using a metal-hydrogel-metal resonator structure using a chitosan-based hydrogel and combined it with solar cells to make a self-powering humidity sensor. These research findings were published as a cover story in the latest edition of Advanced Optical Materials, a journal specializing in nanoscience and optics.
Sensors utilizing light are already widely used in our daily lives in measuring the ECG, air quality, or distance, for example. The basic principle is to use light to detect changes in the surroundings and to convert them into digital signals.
Fabri-Pero interference is one of the resonance phenomena that can be applied in optical sensors and can be materialized in the form of multilayer thin films of metal-dielectric-metal. It is known that the resonance wavelength of transmitted light can be controlled according to the thickness and refractive index of the dielectric layer. However, the existing metal-dielectric-metal resonators have a major disadvantage in not being able to control the wavelengths of transmitted light once they are manufactured, making it difficult to use them in variable sensors.
Humidity sensor combining variable filter and solar cells. Credit: Junsuk Rho (POSTECH)
The research team found that when the chitosan hydrogel is made into the metal-hydrogel-metal structure, the resonance wavelength of light transmitted changes in real time depending on the humidity of the environment. This is because the chitosan hydrogel repeats expansion and contraction as the humidity changes around it.
Using this mechanism, the team developed a humidity sensor that can convert light’s energy into electricity by combining a solar battery with a water variable wavelength filter made of a metal-hydrogel-metal structured metamterial that changes resonance wavelength depending on the external humidity.
The design principle is to overlap the filter’s resonance wavelength with the wavelength where the absorption of the solar cells changes rapidly. This filter is designed to change the amount of light absorption of solar cells depending on the amount of moisture, and to lead to electric changes that ultimately detect the surrounding humidity.
Unlike conventional optical humidity sensors, these newly developed ones work regardless of the type of light, whether it be natural, LED or indoor. Also, not only does it function without external power, but it can also predict humidity according to the filter’s color.
Professor Junsuk Rho who led the research commented, “This technology is a sensing technology that can be used in places like nuclear power reactors where people and electricity cannot reach.” He added, “It will create even greater synergy if combined with IoT technology such as humidity sensors that activate or smart windows that change colors according to the level of external humidity.”
Publication: Advanced Optical Materials (2020)
Self‐Powered Humidity Sensor Using Chitosan‐Based Plasmonic Metal–Hydrogel–Metal Filters
https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201901932
Source: Pohang University of Science & Technology (POSTECH) via Phys.Org
Smart windows that self-illuminate on rainy days
https://phys.org/news/2020-05-smart-windows-self-illuminate-rainy-days.html
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