Privacy without using mini blinds or curtains, and indoor temperatures that can be controlled – these are some of the advantages of smart windows that turn clear on cloudy days to let more light in, and get darker to filter out the sun’s rays on bright days. This is a growing niche and scientists now report a new development – solar smart windows that can power other devices and turn opaque on demand.
Solar powered smart windows normally respond to changing conditions such as heat or light automatically. This does however mean that on cloudy or cool days, users are not able to flip a switch and tint the windows for privacy. These devices also often operate on a fraction of the light energy they are exposed to. The rest of the energy is absorbed by the windows and heats them up. This could add warmth to a room that the windows are supposed to keep cool. Jeremy Munday and colleagues actively started working on eliminating these limitations.
Munday’s team sandwiched a polymer matrix between two glass panes, thus creating a new smart window. The polymer matrix contains micro droplets of liquid crystal materials and an amorphous silicon layer of a type often used in solar cells.
The glass is opaque because the liquid crystals scatter light when the window is off. When the window is turned on by the user, the silicon layer absorbs the light. It also provides the low power required to align the crystals so light can pass through and make the window transparent. According to the researchers, the energy that is not used for operating the window is harvested. This excess energy could be redirected to power other devices such as smartphones, lights or TVs.
The study has been published in ACS Photonics.