Solar powered smart windows offer retrofit solution to temperature control

Now, researchers at Princeton University have developed a self-powered smart window that features solar cells that selectively absorb near-ultraviolet (near-UV) light, so the new windows are completely self-powered.

"Sunlight is a mixture of electromagnetic radiation made up of near-UV rays, visible light, and infrared energy, or heat," said Yueh-Lin (Lynn) Loo, director of the Andlinger Center for Energy and the Environment. "We wanted the smart window to dynamically control the amount of natural light and heat that can come inside, saving on energy cost and making the space more comfortable."

Loo is one of the authors of a paper published in Nature Energy that describes the technology developed in her lab.

Because near-UV light is invisible to the human eye, the researchers set out to harness it for the electrical energy needed to activate the tinting technology in smart windows that augment lighting, cooling and heating systems.

"Using near-UV light to power these windows means that the solar cells can be transparent and occupy the same footprint of the window without competing for the same spectral range or imposing aesthetic and design constraints," Loo said. "Typical solar cells made of silicon are black because they absorb all visible light and some infrared heat - so those would be unsuitable for this application."