Scientists Develop Energy Saving “Liquid Window” Comes From Hydrogel

Members of the NTU research team include Dr. Long Yi (left), Senior Lecturer at the School of Materials Science & Engineering, and PhD student Wang Shancheng (right). Credit: NTU Singapore

Scientists at the University of Technology Nanyang, Singapore (NTU Singapore) have developed liquid window panels that can simultaneously block the sun to regulate solar transmission, while trapping thermal heat that can be released day and night, helping to reduce energy consumption in buildings.

NTU researchers developed its ‘smart windows’ by placing hydrogen-based fluids on glass panels and finding that they can reduce up to 45 percent of the heating, ventilation, and consumption of AC energy in buildings in the simulation, compared to traditional glass windows. They are also about 30 percent more energy efficient than low-emissivity commercials, while cheaper to make.

‘Smart windows’ is the first example reported in the scientific journal of energy-efficient smart windows, and supports the vision of NTU Smart Campus which aims to develop technologically advanced solutions for a sustainable future.

Windows are a key component in building design, but they are also the most energy-efficient part. Because of the ease with which heat can be transferred to glass, windows have a significant effect on the heating and cooling costs of a building. According to a 2009 UN report, buildings account for 40 percent of global energy use, with windows responsible for half of that energy consumption.

Save Fluid Energy Window Demonstration Window

The smart window turns dim when exposed to heat, thus blocking sunlight, and, when cold, returns to its ‘clear’ original state. Credit: NTU Singapore

Conventional energy-saving windows are made of expensive coatings that reduce infrared light passing in or out of a building, thus helping to reduce the demand for heating and heating. However, they do not regulate visible light, which is a major component of sunlight that causes buildings to become hot.

To develop a window to overcome this limitation, NTU researchers turned to water, which absorbs a lot of heat before the start of heat – a phenomenon known as special heating capacity.

They create mixtures of micro-hydrogels, water, and stabilizers, and are found through experiments and simulations that they can effectively reduce energy consumption in some climates, due to their ability to respond to temperature changes. Thanks to the hydrogel, the liquid mixture becomes opaque when exposed to heat, thus blocking sunlight, and, when cold, returns to its ‘clear’ original state.

‘Liquid windows’ are best suited for office buildings

At the same time, the large heat capacity of the water allows a lot of thermal energy to be stored instead of being transferred to the glass and to the building during the hot day. The heat is then cooled and released at night.

Save Energy Liquid Window Materials

The liquid mixture used to create smart windows is made of micro-hydrogels, water, and stabilizers. Credit: NTU Singapore

Dr Long Yi, lead author of a research study published in the journal Joule, and Senior Lecturer at the School of Materials Science & Engineering said, “Our innovation combines the unique properties of both materials – hydrogel and water. By using hydrogen-based fluids we simplify the manufacturing process. to pour the mixture between the two glass panels. This gives the window a unique advantage of high uniformity, which means the window can be made in any shape and size. “

As a result of this feature, the NTU research team believes that the innovation is best suited for work in office buildings, where operating hours are usually throughout the day.

As proof of concept, scientists conducted outdoor tests in hot (Singapore, Guangzhou) and cold (Beijing) environments.

The Singapore test revealed that smart liquid windows have lower temperatures (50 ° C) during the warmest time of day (day) compared to normal glass windows (84 ° C). Beijing tests show that rooms with smart liquid windows absorb 11 percent less energy to maintain the same temperature compared to rooms with normal glass windows.

The smart window slides the peak of the electric load, the sound block

Scientists also measure when the highest value of thermal energy is stored that day.

The ‘temperature peak’ in this normal glass window is at 12 pm, and in the smart liquid window is switched to 2 pm. If this peak temperature shift translates to a shift in time that should be in the building by electric power to cool or warm the building, it should result in lower energy tariff costs for the user.

Simulations using actual building models and weather data in four cities (Shanghai, Las Vegas, Riyadh, and Singapore) show that smart liquid windows have the best energy-saving performance in all four cities compared to regular glass windows and low emissivity windows.

Soundproof tests also show that smart liquid windows reduce noise by 15 percent more effectively than double-glazed windows.

The first author of the study, Wang Shancheng, who is a Project Officer at the School of Materials Science & Engineering, said, “A two-block glass window sounds like two glasses separated by an air gap. Our windows are designed the same, but to replace the air, we fill the gap with hydrogel-based fluid, which enhances sound insulation between glass panels, thus offering additional benefits that are not commonly found in current energy-saving windows. “

The first other author, Dr. Zhou Yang is a PhD student at NTU and is currently a Associate Professor at China University of Petroleum-Beijing (CUPB).

Providing an independent view, Professor Ronggui Yang, of Huazhong University of Science and Technology, China, who received the Nukiyama 2020 Memorial Prize in Integrated Science and Engineering and experts in thermal and energy systems said, , and take us away from conventional glass design. Disruptive innovations lead to solar regulation and heat storage, which together produce incredible energy savings. “

The research team is now looking to collaborate with industry partners to commercialize smart windows.

References: “Smart Thermo-Responsive Liquid Window Comes from Hydrogel” by Yang Zhou, Shancheng Wang, Jinqing Peng, Yutong Tan, Chuanchang Li, Freddy Yin Chiang Boey and Yi Long, September 23, 2020, Joule,
DOI: 10.1016 / j.joule.2020.09.001

This research was supported by the National Research Foundation, Prime Minister’s Office, Singapore, in its Campus program for Excellence Research and Technological Enterprise (CREATE), and the Sino-Singapore International Joint Research Institute.

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