An international research team led by scientists from Nanyang Technological University, Singapore, has developed a material that can be used to create ‘smart windows’ that can self-adapt to heat or cool rooms.
Windows are among the least energy-efficient components of most buildings. According to a UN report released in 2009, buildings account for 40 per cent of global energy usage, and windows are responsible for half of that energy consumption.
The new self-adaptive glass works by exploiting the parts of the light spectrum that are responsible for heating and cooling. During summer, the glass cools the room by suppressing near infrared light, which causes solar heating, and boosting long-wave infrared light, which is responsible for radiative cooling. In winter, it does the opposite, causing the room to warm up.
The glass features layers of vanadium dioxide nanoparticles, poly(methyl methacrylate) (PMMA) and a low-emissivity coating.
‘Most energy-saving windows today tackle the part of solar heat gain caused by visible and near infrared sunlight, said the study’s principal investigator, Long Yi of the NTU School of Materials Science and Engineering. ‘However, researchers often overlook the radiative cooling in the long wavelength infrared. While innovations focusing on radiative cooling have been used on walls and roofs, this function becomes undesirable during winter. Our team has demonstrated for the first time a glass that can respond favourably to both wavelengths, meaning that it can continuously self-tune to react to a changing temperature across all seasons.’
The team found that the glass showed energy savings in both warm and cool seasons, with an overall energy-saving performance of up to 9.5 per cent less than commercially available low-emissivity glass in a simulated medium-sized office building.
‘The results prove the viability of applying our glass in all types of climates as it is able to help cut energy use regardless of hot and cold seasonal temperature fluctuations,’ said Wang Shancheng, an NTU research fellow. ‘This sets our invention apart from current energy-saving windows, which tend to find limited use in regions with less seasonal variations.’
Moreover, the glass’s heating and cooling performance can be customised to suit the needs of the market and region for which it’s intended. ‘We can do so by simply adjusting the structure and composition of special nanocomposite coating layered onto the glass panel, allowing our innovation to be potentially used across a wide range of heat regulating applications, and not limited to windows, said Long Yi.
The research team how hopes to achieve even higher energy-saving performance by tweaking the design of the nanocomposite coating.
The research has been published in Science.