While smart windows have existed for a while, they often block visible light by changing colour, while also blocking warmth when you may want it. PhD student Hitesh Khandelwal from the Dutch Technological University Eindhoven created a smart window that stops invisible, infrared sunlight, while letting visible light through. Another perk of this window is that you can switch it on and off when you please.

Heating, cooling and lighting a building consumes more than 50 per cent of the total amount of energy. Daylight plays a major role in this. In summer, the sun heats up rooms, which causes the need for air conditioning, while in winter, the sun saves on heating costs.

The Khandelwal’s smart windows can stop light with a wavelength between 700 and 1400 nanometres. This light is in the infrared spectrum and is invisible, but contains nearly 50 per cent of solar energy.

The block the infrared light, the window uses organic, liquid crystals also used in smartphones. These crystals stop light of a certain wavelength, but only if they are arranged correctly. Using an electrical current, these molecules can be arranged to reflect sunlight. The transparency of the windows is still about 90 per cent, similar to double glass.

Thanks to the on/off switch on the window, the energy consumed by heating and cooling can be reduced by up to 12 per cent.

To bring the costs down, Khandelwal developed prototypes to apply the coating to existing windows.

Photos: Khandelwal / Pexels