Researchers from Nanyang Technological University have created an energy saving material that, when coated on a glass window panel, can effectively respond to changing temperatures by switching between heating and cooling.
How it works
Using layers of vanadium dioxide nanoparticles composited of polymethyl methacrylate (PMMA), scientists were able to create this energy saving glass, and low emissivity coating, to form a unique structure that can modulate heating and cooling simultaneously. Thus, the newly developed glass has no electrical components, and works by exploiting the spectrums of light responsible for heating and cooling.
Principal investigator of the study, Dr Long Yi of the Nanyang Technological University (NTU) School of Materials Science and Engineering said, “most energy-saving windows today tackle the part of solar heat gain caused by visible and near infrared sunlight. 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.”
To improve the performance of the windows, the NTU research team focused on assuring that the modulation of both solar transmission and radiative cooling were simultaneous. “This innovation fills the missing gap between traditional smart windows and radiative cooling by paving a new research direction to minimise energy consumption,” said Professor Gang Tan, a researcher on the study.
During summer, the glass suppresses solar heating, which is near infrared light, while boosting radiative cooling, or long-wave infrared light. This is a natural phenomenon, where in which heat emits through surfaces towards the cold universe to cool the room, whereas in the winter, it does the opposite to warm up the room.
Researchers used lab tests and an infrared camera to visualise results, the energy saving glass allowed a controlled amount of heat to emit in various conditions (room temperature – above 70°C), proving its ability to react dynamically to changing weather conditions.
Energy saving glass and different climates
Windows are one of the key components in a building’s design, but they are also the least energy-efficient and most complicated part. In the United States alone, window-associated energy consumption in buildings accounts for approximately 4% of their total primary energy usage every year, according to data from the Department of Energy in US.
Scientists have previously attempted to develop sustainable, energy saving innovations to address this demand, but none of the solutions have been able to modulate both heating and cooling at the same time, until now.
The NTU research team believes their innovation offers a convenient way to conserve energy in buildings since it does not rely on any moving components, electrical mechanisms, or blocking views, to function. This also aligns with the NTU 2025 plan, which seeks to address humanity’s grand challenges on sustainability, and accelerate the translation of research discoveries into innovations that mitigate human impact on the environment.
In order to establish how successful, the energy saving glass was in different climates during different seasons, the scientists tested the energy-saving performance of their invention using simulations of climate data covering all populated parts of the globe, which consisted of seven climate zones in total.
The team found the glass they developed showed energy saving abilities in both warm and cool seasons, with an overall energy saving performance of up to 9.5%, or ~330,000 kWh per year, which is less than commercially available low emissivity glass in a simulated medium sized office building.
First author of the study Wang Shancheng, former student of Dr Long Yi, said, “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. This sets our invention apart from current energy-saving windows which tend to find limited use in regions with less seasonal variations.”
The energy saving glass can also be customised to suit the needs of the market and region for which it is 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,” explained Dr Long Yi.
A Singapore patent has been filed for the innovation. As the next steps, the research team is aiming to achieve even higher energy-saving performance by working on the design of their nanocomposite coating.
