New Window Coating: Let The Light In – Leave The Heat Out

smart window

A team from A*STAR Singapore Institute of Manufacturing and Technology, led by Hui Huang, is working on refining the chemical arrangement of nanoparticles to block the infrared heat, while at the same time still allowing the visible light in. The new technology will be manufactured as a coating that can be applied to existing windows.

We use windows and glass doors to let in as much natural light as possible, but that also lets in near infrared radiation, which generates heat. In colder climates this is more than welcomed, but in tropical climates, the greenhouse effect has us using air conditioning to keep the temperature at comfortable levels.

In tropical countries like Singapore, the largest component of a building’s energy consumption is air conditioning. Smart windows that block near-infrared radiation but still allows most of the light in will save on energy costs and thereby reduce carbon emissions. Significant savings can be achieved even if the heat intake is reduced by a small percentage.

smart window
A*STAR researchers have developed a special window coating that lets the visible light in, but at the same time blocks near-infrared radiation. (Credit image: A*STAR Singapore Institute of Manufacturing and Technology)

Currently, window coatings using antimony doped tin oxide nanopowders are commercially available. Although Huang and his team use the same chemicals, they are focusing on varying the nanoparticles‘ antimony concentration to achieve the optimum absorption of near infrared radiation. The initial results far exceed the current solutions with the infrared shielding achieved being twice that of existing products. Using a coating with 10-nanometer antimony-doped tin oxide nanoparticles, more than 80 percent of visible light is let through, while more than 90 percent of the infrared radiation is blocked.

A synthesis procedure known as the solvothermal method was used to produce the tiny nanoparticles. Using a special vessel, called an autoclave, precursors are heated under pressure. The method allows the nanoparticle size to be tightly controlled and requires relatively low temperatures. The key to allowing some wavelengths through while blocking others lies in the nanoparticle size. Huang’s work has already attracted the interest of a local glass company in Singapore. They are interested in licensing this smart window technology with infrared shielding.

The research has been published in the Materials & Design journal.