An international team led by scientists from Singapore’s Nanyang Technological University has developed an electrochromic window material that can control heat transfer without blocking the line of sight.
This new material can help reduce the energy required to cool and heat buildings. It has specially designed nanostructures including titanium dioxide (TiO2), tungsten trioxide (WO3), neodymium-niobium (Nd-Nb) and tin (IV) Oxide (SnO2). This composite material is intended to be coated on glass window panels, and when electrically activated, users will be able to control the transmission of infrared radiation through the window.
According to experimental simulations, this advancement detailed in ACS Omega can block up to 70% of infrared radiation without affecting the field of view because it allows up to 90% of visible light to pass through.
The NTU team in Singapore added that this material is also about 30% more efficient in regulating heat than commercially available electrochromic windows.
Electrochromic windows change color when in use, thereby reducing light entering the room. Commercially available electrochromic windows are usually coated with a layer of tungsten trioxide (WO3) on one side of the glass panel. When the window is opened, the current moves the lithium ions to the side containing WO3, and the window becomes dark or opaque. Once closed, the ions will move away from the coated glass and the window becomes clear again.
However, current electrochromic windows can only effectively block visible light, so heat will continue to pass through the windows.
Another obvious disadvantage of current technology is its durability, because the performance of electrochromic components tends to decline within three to five years. In laboratory tests, NTU's electrochromic technology evaluated its durability through switching cycles, and the results showed that the characteristics of the window maintained "excellent stability", blocking more than 65% of infrared radiation.
The lead author, Associate Professor Alfred Tok of the School of Materials Science and Engineering at NTU said: "By combining specially designed nanostructures, we enable materials to react in a'selective' way, blocking near-infrared radiation, while still allowing most visible light It can pass when our electrochromic window is open. The choice of advanced materials also helps to improve the performance, stability and durability of smart windows."
In a related study, the NTU team created a switching system to help control the conduction heat from the external environment.
It is said that the patented NTU switch is composed of magnetic carbon-based particles and a film with good thermal conductivity. When the switch is closed, the conducted heat cannot pass through the window, but the heat can pass through when it is open.
When integrated with newly developed electrochromic materials, the team said in a statement that its smart windows can control infrared radiation and conduct heat.
Dr. Ronn Goei, the first author of the study and a senior researcher at the School of Materials Science and Engineering, Nanyang Technological University, said: “Because of the ability to control the infrared radiant heat from the sun and the conduction heat through windows, we hope that this technology can be particularly effective in temperate climates. Useful because building occupants can use it to adjust heat loss or increase according to seasonal changes, while still enjoying most of the scenery."
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