Harvard Physicists Propose Harvesting Energy By Emitting Infrared Light Into Space

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Earth Lit Up
Earth lit up at night.

Physicists at Harvard University are proposing a new type of renewable energy technology -- a device that would power the planet with infrared light beamed into outer space.

Yes, you read that right. Rather than harnessing the sun’s light like a typical solar photovoltaic panel, this technology would generate electricity by emitting invisible electromagnetic radiation into the universe.

Federico Capasso, tenured professor of applied physics at Harvard, has led a team of researchers to analyze the thermodynamics, practical concerns and logistical requirements. Their findings will be published this week in the journal Proceedings of the National Academy of Sciences.  

“It’s not at all obvious, at first, how you would generate DC [direct current] power by emitting infrared light in free space toward the cold,” Capasso said. “To generate power by emitting, not by absorbing light, that’s weird. It makes sense physically once you think about it, but it’s highly counterintuitive. We’re talking about the use of physics at the nanoscale for a completely new application.”

Capasso’s group suggests two different kinds of energy producers that rely on the principle that differences in temperature generate work.

One would use a hot plate at the temperature of the air with a cold plate on top, facing upward and radiating heat to the sky. The researchers calculate that the heat difference between the plates could generate a few watts per square meter, day and night.

The second proposed device would leverage temperature differences between tiny electronic components rather than temperatures felt by humans.

Yet there are considerable challenges yet to iron out. The more power that flows through, the easier it is to harness, but when harvesting energy from the infrared emissions, the voltage is relatively low.

This technology would be far from Capasso’s first invention. He is known internationally for his work in semiconductor physics, photonics (which involves the emission of light waves) and solid-state electronics. In 1994, he co-invented an infrared quantum-cascade laser. Capasso also pioneered the field of bandgap engineering, and last year, he won the highest honor from SPIE, the international society for optics and photonics. 

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