Self-powered system makes smart windows smarter

By Sharon Adarlo

A new solar cell technology could make it inexpensive to create and install smart windows that automatically vary their tint to augment lighting, heating and cooling systems in buildings.

The new transparent solar cells selectively absorb near- ultraviolet (UV) light and convert it to electricity that powers chemical reactions to lighten or darken the glass of the smart window as needed. Smart windows are usually bulky to install because they require an external power source. The new solar cells allow smart windows to be self-powered and occupy the same footprint as the glass.

Gloved hand holding glass

Graduate student Nicholas Davy holds a sample of glass that uses near-ultraviolet light to generate electricity, which powers chemical reactions that lighten or darken the glass.

“We wanted the smart window to dynamically control the amount of natural light and heat that can come inside, saving on energy costs and making the space more comfortable,” said Yueh-Lin (Lynn) Loo, director of the Andlinger Center for Energy and the Environment, the Theodora D. ’78 and William H. Walton III ’74 Professor in Engineering, and professor of chemical and biological engineering.

The study, published June 30, 2017, in the journal Nature Energy, received funding from the National Science Foundation.

Nicholas Davy, a doctoral student in the chemical and biological engineering department and the paper’s first author, said the new transparent near-UV solar cells are better suited to power smart windows than existing transparent solar cells, which target the infrared portion of sunlight and thus complicate the control of heat.

The Princeton team’s aim is to create a flexible version of the solar-powered smart window system that can be applied to existing windows via lamination. Davy and Loo have started a company called Andluca Technologies to bring this energy-saving solution to residential and commercial buildings.

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