Scientists at the Nanyang Technological University, Singapore (NTU Singapore) have developed a liquid window panel that can simultaneously block the sun to regulate solar transmission, while trapping thermal heat that can be released through the day and night, helping to reduce energy consumption in buildings.
The NTU researchers developed their 'smart window' by placing hydrogel-based liquid within glass panels and found that it can reduce up to 45 per cent of heating, ventilation, and air-conditioning energy consumption in buildings in simulations, compared to traditional glass windows. It is also 30 per cent more energy efficient than commercially available low-emissivity (energy-efficient) glass, while being cheaper to make.
The 'smart window' is the first reported instance in a scientific journal of energy-saving smart windows made using liquid, and supports the NTU Smart Campus vision which aims to develop technologically advanced solutions for a sustainable future.
Windows are a key component in a building's design, but they are also the least energy-efficient part. Due to the ease with which heat can transfer through glass, windows have a significant impact on heating and cooling costs of a building. According to a 2009 report by the United Nations, buildings account for 40 per cent of global energy usage, and windows are responsible for half of that energy consumption.
Conventional energy-saving low-emissivity windows are made with expensive coatings that cut down infrared light passing into or out of a building, thus helping to reduce demand for heating and cooling. However, they do not regulate visible light, which is a major component of sunlight that causes buildings to heat up.
To develop a window to overcome these limitations, the NTU researchers turned to water, which absorbs a high amount of heat before it begins to get hot – a phenomenon known as high specific heat capacity.
They created a mixture of micro-hydrogel, water and a stabiliser, and found through experiments and simulations that it can effectively reduce energy consumption in a variety of climates, due to its ability to respond to a change in temperature. Thanks to the hydrogel, the liquid mixture turns opaque when exposed to heat, thus blocking sunlight, and, when cool, returns to its original 'clear' state.
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source: www.media.ntu.edu.sg
