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New Window Design Directs Sunshine, Indoor Light to Solar Cells

An engineering team at Rice University in Houston has come up with a new design for window glass that redirects incoming sunlight, or even indoor illumination, to solar cells that can turn it into electricity.

The luminescent solar collectors (LSC) measure one foot by one foot (0.3 by 0.3 metres) and consist of a strip of conjugated polymer mounted between two clear acrylic panels, PVBuzz reports. The formulations so far have been prone to degrade quickly, but the researchers behind the project say they’re getting better.

“That thin middle layer is the secret sauce,” PVBuzz writes, citing a report in the journal Polymer International by Yilin Li and Rafael Verduzco of Rice’s Brown School of Engineering. “It’s designed to absorb light in a specific wavelength and guide it to panel edges lined with solar cells.”

PVBuzz defines conjugated polymers as chemical compounds “that can be tuned with specific chemical or physical properties for a variety of applications, like conductive films or sensors for biomedical devices.”

This particular compound “accepts light from any direction but restricts how it leaves, concentrating it onto the solar cells that convert it to electricity,” the news report states.

“The motivation for this research is to solve energy issues for buildings through integrated photovoltaics,” explained Li, a post-doctoral researcher and lead author of the journal paper. “Right now, solar rooftops are the mainstream solution, but you need to orient them toward the sun to maximize their efficiency, and their appearance isn’t very pleasing.”

With that in mind, “we thought, why can’t we make colourful, transparent, or translucent solar collectors and apply them to the outside of buildings?” he added.

The Rice team’s test units produce far less sunlight than the 20% usually available from commercial solar cells, PVBuzz says. “But LSC windows never stop working. They happily recycle light from inside the building into electricity when the sun goes down. In fact, tests showed they were more efficient at converting ambient light from LEDs than they were from direct sunlight, even though the sunlight was 100 times stronger.”

“Even indoors, if you hold up a panel, you can see very strong photoluminescence on the edge,” Li said.

Verduzco, a professor of chemical and biomolecular engineering and of materials science and nanoengineering at Rice, said the research so far points toward collectors with “desired optical qualities” that are more durable than anything the team has produced so far.