Soaking up the sun with laser treated metal

The University of Rochester research lab that recently used lasers to create unsinkable metallic structures has now demonstrated how the same technology could be used to create highly efficient solar power generators.

In a paper in Light: Science & Applications, the lab of Chunlei Guo, a professor of optics also affiliated with Physics and the Materials Science Program, describes using powerful femtosecond laser pulses to etch metal surfaces with nanoscale structures that selectively absorb light only at the solar wavelengths but not elsewhere.

A regular metal surface is shiny and highly reflective. Years ago, the Guo lab developed a black metal technology that turned shiny metals pitch black. “But to make a perfect solar absorber,” Guo says, “we need more than a black metal, and the result is this selective absorber.”

This surface not only enhances the energy absorption from sunlight but also reduces heat dissipation at other wavelengths, in effect, “making a perfect metallic solar absorber for the first time,” Guo says. “We also demonstrate solar energy harnessing with a thermal electric generating device.”

“This will be useful for any thermal solar energy absorber or harvesting device,” particularly in places with abundant sunlight, he adds.

The work is funded by awards from the Bill and Melinda Gates Foundation, the Army Research Office, and the National Science Foundation.

The researchers experimented with aluminum, copper, steel, and tungsten, and found that tungsten, commonly used as a thermal solar absorber, had the highest solar absorption efficiency when treated with the new nanoscale structures. This improved the efficiency of thermal electrical generation by 130 percent compared to untreated tungsten.

Co-authors include Sohail Jalil, Bo Lai, Mohamed Elkabbash, Jihua Zhang, Erik M. Garcell, and Subhash Singh of the Guo lab.

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