Scientists unlock the secret to pulling energy from the air

ElectromagneticSpectrumWikipedia

The electromagnetic spectrum, from low frequency to high. Visible light is only a tiny part of the spectrum. (Wikimedia)

We’re constantly using devices that emit energy in the form of radio waves or microwaves. We don’t think of those waves the way we think of light, but they’re basically just a different wavelength of light that’s beyond our range of perception. Our wifi routers, radio stations, cell phones, and cell phone towers all emit tons of this energy nonstop. In the modern world, even in a pitch-dark room, there’s still light that you just can’t see. Microwaves and radio waves are everywhere.

VisibleRadioWaves_NikolayLamm

What if you could see wifi? Artist Nikolay Lamm gives us this rendering of what the different channels might look like.

So if we have solar panels that get energy from visible light, why don’t we have a way to capture this invisible light?

Two students at Duke University have been asking that question and coming up with new ways to recapture that energy that would otherwise be wasted.

They’ve caught microwave signals like cell phones use and turned them back into useable electricity. They used “meta materials” to do it. Metamaterials are special materials that use a really finely detailed structure like a 3-D circuit board to get waves to do things they normally wouldn’t. It’s possible to use metamaterials to capture energy from all sorts of waves, including sound waves.

178613_hawkes_katko_0013

Allen Hawkes, Alexander Katko, and Stephen Cummings of Duke University devised this array of metamaterial cells to capture useful energy from microwaves. Adding more cells captures more of the available energy. (Duke)

The efficiency of this proof-of-concept work is already about the same as current solar cells. From a strong microwave signal, they captured enough energy to recharge a cell phone battery.

A few years ago, a different group of Duke researchers demonstrated a way to get energy from radio waves.

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