Scientists create energy-saving ‘liquid window’

Scientists at the Nanyang Technological University, Singapore (NTU Singapore) have developed a liquid window panel that can block the sun to regulate solar transmission while reducing energy consumption in buildings.

The NTU researchers found that by placing hydrogel-based liquid within glass panels, the window is able to trap thermal heat that can be released through the day and night. This helps to reduce up to 45 per cent of energy consumption in buildings in simulations, compared to traditional glass windows. The “smart window” is also cheaper to manufacture than commercially available low-emissivity (energy-efficient) glass, yet is around 30 per cent more energy efficient.

While conventional low-emissivity windows also help to reduce demand for heating and cooling, they do not regulate visible light, which is a major component of sunlight that causes buildings to heat up.

Through experiments and simulations, the NTU team discovered their mixture of micro-hydrogel, water and a stabiliser 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.

The NTU research team believes that these features make their innovation suitable for use in office buildings, where operating hours are mostly in the day.

Successful trials

Based on outdoor trials in hot (Singapore, Guangzhou) and cold (Beijing) environments, it was revealed that the smart liquid window had a lower temperature (50°C) during the hottest time of the day (noon) compared to a normal glass window (84°C).

The Beijing tests showed that the room using the smart liquid window consumed 11 per cent less energy to maintain the same temperature compared to the room with a normal glass window.

The “smart window” is the first reported instance in a scientific journal (Joule) 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.

The research is supported by the National Research Foundation, Prime Minister’s Office, Singapore, under its Campus for Research Excellence and Technological Enterprise (CREATE) programme, and the Sino-Singapore International Joint Research Institute.

Featured image: A composite photo showing the window in the before (cool) and after (hot) state, courtesy of NTU Singapore.

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