Flexible solar tiles to make move inside and recycle artificial light

Researcher Congcong Wu, holding up one of the flexible solar tiles that can recycle artificial light(Credit: Virginia Tech)

Roofs have long been the realm of solar panels, right up to Tesla's announcement a few weeks ago of energy-harvesting roofing tiles, but solar panels can also be hiding in windows and walls, and soon, might make their way indoors too. A Virginia Tech team is developing low-cost, flexible solar tiles that could be incorporated into curtains and wallpaper to capture natural sunlight and artificial light.

Flexible and less than half a millimeter thick, the researchers' new solar panels are each palm-sized and can generate about 75 mW of power, but can be scaled up in rolls to be used in curtains, window shades and wallpaper. They're made using a screen-printing process that adheres a layer of titanium oxide paste onto a thin, flexible base, making them fairly cheap to produce.

"There are several elements that make the technology very appealing," says Shashank Priya, the leader of the project. "First, it can be manufactured easily at low temperature, so the equipment to fabricate the panels is relatively inexpensive and easy to operate. Second, the scalability of being able to create the panels in sheet rolls means you could wallpaper your home in these panels to run everything from your alarm system, to recharging your devices, to powering your LED lights."

But perhaps the most useful characteristic of the panels is their ability to absorb diffused light. That means the range of light they can harvest extends beyond just sunlight, and into that thrown off by LED, incandescent and fluorescent lighting. Theoretically, the system could recycle the light from a building's internal fixtures to help power those same lights.

Currently, the panels operate at around 10 percent efficiency, which isn't far behind the peak efficiency of 13 to 15 percent enjoyed by established amorphous silicon panels. The team believes that efficiency can be increased to the point where flexible panels outpace their rigid brethren, eventually making them viable to be woven into clothing, like military uniforms and backpacks. There, they could be part of a suite of technologies, like piezoelectric generators, to keep soldiers charged up in the field.

"Right now we are on the cutting edge of this technology," says Priya. "Our edge is in the ability to fabricate large-area modules with high efficiency. We are actively working to integrate the product with the market and we see a wide variety of uses for the technology, from clothing to windows, to smart buildings to UAVs to mobile charging stations."

The research was published in the journals Solar Energy Materials and Solar Cells and ACS Energy Letters.

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