Clear material on windows harvests solar energy

A new type of “transparent” solar concentrator can be used on windows or mobile devices to harvest solar energy without obscuring the view.

Past efforts to create similar materials have been disappointing, with inefficient energy production or highly colored materials.

“No one wants to sit behind colored glass,” says Richard Lunt, an assistant professor of chemical engineering and materials science at Michigan State University. “It makes for a very colorful environment, like working in a disco. We take an approach where we actually make the luminescent active layer itself transparent.”

The solar harvesting system uses small organic molecules developed by Lunt and his team to absorb specific nonvisible wavelengths of sunlight.

“We can tune these materials to pick up just the ultraviolet and the near infrared wavelengths that then ‘glow’ at another wavelength in the infrared,” he says.

The “glowing” infrared light is guided to the edge of the plastic, where it is converted to electricity by thin strips of photovoltaic solar cells.

“Because the materials do not absorb or emit light in the visible spectrum, they look exceptionally transparent to the human eye,” Lunt says.

Tall buildings with lots of windows

One of the benefits of this new development is its flexibility. While the technology is at an early stage, it has the potential to be scaled to commercial or industrial applications. The technology is featured in the journal Advanced Optical Materials.

“It opens a lot of area to deploy solar energy in a nonintrusive way,” Lunt says. “It can be used on tall buildings with lots of windows or any kind of mobile device that demands high aesthetic quality like a phone or e-reader. Ultimately we want to make solar harvesting surfaces that you do not even know are there.”

Lunt says more work is needed in order to improve its energy-producing efficiency. Currently it is able to produce a solar conversion efficiency close to 1 percent, but noted they aim to reach efficiencies beyond 5 percent when fully optimized. The best colored LSC has an efficiency of around 7 percent.

Source: Michigan State University