A new transparent solar cell technology can turn ordinary windows into energy-efficient “smart” windows, regulating the transmission of sunlight and heat to save energy and improve occupant comfort, but without the need for an electrical power source.
The self-powered smart window developed by Professor Yueh-Lin (Lynn) Loo, Princeton University's Theodora D. ’78 and William H. Walton III ’74 Professor in Engineering and director of the Andlinger Center for Energy and the Environment, and her team includes two components: a solar cell that harvests near-ultraviolet light to produce electricity, and the technology to use that harvested electricity to change the window’s color.
This color change with electricity, or “electrochromism,” regulates how much visible light and near-infrared heat enter the window.
Smart windows darken on hot days to keep the sun out and keep rooms cool, or they let heat in on cold days while reducing glare and protecting privacy. But current technology requires plugging the smart windows into an electrical source, adding to installation and operating costs.
Loo and her team’s near-ultraviolet solar cells not only reduce costs and save energy, but because they are self-powered, they eliminate the need for external wiring.
Beyond powering smart windows, the transparent solar cell technology can enable other wireless low-power consumer products, such as internet-of-things sensors, wearables and displays.