Researchers have been investigating creating invisible or nearly invisible solar cells that could absorb light while still remaining transparent. Now a group of Princeton University engineers have developed a system that could generate electricity while varying the tint-level of glass with controllable glazing, allowing a window to provide more heating and cooling properties for a home.
The researchers said that such devices could save up to 40 percent of an average building’s energy costs by changing the amount of light entering a building and impacting the amount of energy used to heat and cool a building. In the past, such tinting required an additional power source, but the Princeton researchers used a new photovoltaic cell technology that selectively absorbs near-ultraviolet light to power the windows. They said the approach promised to be inexpensive and easy to apply to existing windows.
“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 Princeton’s Andlinger Center for Energy and the Environment. Loo led the research which was published in Nature Energy on June 30. “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.”
The new glazing for the smart window controls the transmission of multiple spectra of light, including visible light and infrared light (heat), while using Near-UV to power its changing tint. “This new technology is actually smart management of the entire spectrum of sunlight,” Loo said.
The solar cell itself is comprised of organic semiconductors. The researchers are able to tune the solar cells to absorb light only from a certain spectrum. By choosing near-UV light, they’re able to create a device that is still transparent to the human eye.
“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 added. “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.”
While the UV cells don’t generate as much energy as the other solar cells it’s enough to power the window. When sunlight strikes the device it generates an electrical charge in the solar cell, triggering the electrochromic glazing to change from clear to dark blue, according to Princeton. The darkened window can block more than 80 percent of light.
Looking ahead the researchers hope to incorporate the technology into flexible version that can be applied to existing windows via lamination. “Someone in their house or apartment could take these wireless smart window laminates—which could have a sticky backing that is peeled of—and install them on the interior of their windows,” said Nicholas Davy, a doctoral student and the paper’s lead author. “Then you could control the sunlight passing into your home using an app on your phone, thereby instantly improving energy efficiency, comfort and privacy.”
To bring the technology to market Davy and Loo have started Andluca Technologies. The company will investigate other applications for the transparent solar cells, including powering the sensors for internet-of-things products and other low-power consumer products.Tweet