International News
NOVEL HYDROGEL-GLASS DESIGN FOR ENERGY SAVING IN BUILDINGS
Jia Fu , Chunzao Feng , Yutian Liao , Mingran Mao , Huidong Liu & Kang Liu .
Traditional glass windows are the least energy-efficient components in buildings . In the summer , the near-infrared sunlight transmitted through windows produces undesired heating . In turn , the high reflection of mid-infrared limits heat rejection from the building . This “ greenhouse effect ” aggravates cooling energy consumption of HVAC systems .
To counter this problem , researchers at Wuhan University in China have proposed a novel design of hydrogel-glass which consists of a layer of hydrogel and a layer of normal glass that can selectively block heat from the sun without blocking its light .
The new hydrogel-glass possesses a higher level of visible light transmission , stronger near-infrared light blocking , and higher mid-infrared thermal emittance than traditional glass . Thanks to all these properties , the researchers demonstrate that hydrogel-glass windows can enhance indoor illumination and reduce indoor temperature .
To further demonstrate the potential of the hydrogel-glass for windows in buildings , researchers set the hydrogel-glass on a small house model with a size of 20 cm × 20 cm × 20 cm and measured the illuminance and temperature at different spots .
The results showed that the indoor illuminance of the house with hydrogel-glass is slightly higher than that in the house with normal glass on a sunny day .
Structure design and working principle of the hydrogel-glass .
Wuhan University
The enhanced illuminance also helps to reduce the electricity consumption from lighting . More importantly , the indoor temperature of the house with the hydrogel-glass was always lower than that of the house with normal glass . The largest temperature reduction reaches 3.5 ° C at noon with the highest solar intensity of 58.7 mW / square centimeter .
In tests , the hydrogel-glass achieved a high thermal emittance of 96 %, which is higher than that of other transparent radiative cooling windows . The glass exhibited a reflection band at about 9 μm due to the strong refraction , and this led to a low thermal emittance of around 84 %.
The average transmittance of the new glass was 92.8 %, with a 0.15-mm-thick hydrogel layer . When further increasing the hydrogel thickness to 1.7 and 3.4 mm , it decreased to 92.6 % and 92.5 %, respectively .
The simulations suggest energy savings ranging from 2.37 to 10.45 MJ / square meter per year can be achieved for typical school buildings located in different cities around the world .
With broadband light management covering the visible and thermal infrared regions of the spectrum , hydrogel-glass shows great potential for application in energy-saving windows . RACA
Novel hydrogel-glass design for energy saving in buildings .
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