With Transparent Solar Panels, Windows Could Harvest Energy Too

One day we'll be able to plaster more surfaces with solar harvesters, if the idea of transparent solar concentrators lives up to its potential. Researchers from Michigan State University report that they've developed transparent, luminescent concentrators that can be placed on windows, your phone screen—anything with a clear surface—without blocking the view.

Richard Lunt, assistant professor of chemical engineering and materials science at MSU's College of Engineering led a team that developed small organic molecules that absorb certain wavelengths of sunlight invisible to the human eye.

"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," Lunt explained in a statement. "Because the materials do not absorb or emit light in the visible spectrum, they look exceptionally transparent to the human eye."

The infrared light is trapped and guided to the edges of the plastic solar concentrator, where photovoltaic cells convert it into electricity. That's one of the reasons solar luminescent concentrators (LSCs) are attractive alternatives to more conventional photovoltaics: They can harvest light from a larger area without having to track the Sun. The materials are also comparatively inexpensive, which could potentially make for cheaper solar power.

The idea is like that of cheap, printable plastic solar panels, but its the transparency that makes it particularly attractive. This type of research has been conducted before in see-through films, but previous work used coloured materials and produced little energy. "No one wants to sit behind coloured glass," wrote Lunt. "We take an approach where we actually make the luminescent active layer itself transparent."

To be fair, Lunt's solar concentrators only have a solar conversion efficiency of one percent at the moment, which is less than the best coloured precedents. Solar film manufacturer Heliatek reports an efficiency of seven percent with its product that is 40 percent transparent. Lunt's team aims to reach efficiencies of over five percent when the new solar harvester is fully optimised.

The applications for efficient transparent solar concentrators could be expansive. They could be put on skyscrapers with lots of windows, or integrated into e-readers or tablets to sustain their battery life for longer, or placed on car windows to energise electric cars, and so on. The ultimate aim is to make solar harvesting surfaces that you do not even know are there.