Smart window blocks the sun’s heat without blocking views

As a part of the building envelope, windows can have a significant impact on energy demand and heating and cooling demands of buildings. Window films can help block against solar heat gain and protect against glare and ultraviolet exposure. But to block heat from the sun means blocking views of the outside.

Now, a team of researchers from Nanyang Technological University, Singapore (NTU Singapore) has invented a “smart” window material that blocks rays and controls heat transmission without blocking views. The new material could help cut the energy required to cool and heat buildings.

The new energy-saving material for electrochromic windows that operate at the flick of a switch is designed to block infrared radiation – which is the major component of sunlight that emits heat. It comprises of an inexpensive mixture of advanced materials like titanium dioxide (TiO2), tungsten trioxide (WO3), neodymium-Niobium (Nd-Nb), and tin (IV) oxide (SnO2). The composite material is intended to be coated onto window panels, and when activated by electricity, users would be able to ‘switch on and off’ the infrared radiation transmitted through the window.

The invention could block up to 70% of infrared radiation without compromising views through the window since it allows up to 90% of visible light to pass through. It is also about 30% more effective in regulating heat than commercially available electrochromic windows and is cheaper to make due to its durability.

The performance of the existing electrochromic component tends to degrade in three to five years. During the lab tests, NTU’s electrochromic technology was put through rigorous on-off cycles to evaluate its durability, and the result showed the properties of the window retained excellent stability (blocked more than 65% of infrared radiation), demonstrating its superior performance, feasibility, and costs saving potential for long-term use in sustainable buildings.

According to the research team, the new electrochromic technology may help conserve energy that would be used for the heating and cooling of buildings and could contribute to the future design of sustainable green buildings.

The NTU team created a switch system to improve the performance of their smart window technology. The switch comprises carbon-based magnetic particles and thin films that are good conductors of heat. When the switch is turned off, conducted heat cannot transfer through the window, and when it is on, the heat will be allowed to pass through the glass window.

“By integrating both the new electrochromic material we invented and the patented switch in a window, we can create a smart window with unique capabilities,” said Dr. Ronn Goei, the first author of the study. “With the ability to control both infrared radiated heat from the sun and conducted heat passing through the window, we expect this technology to be particularly useful in temperate climates, as building occupants can use it to regulate heat loss or gain according to the needs of the changing seasons, while still enjoying much of the view.”

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