This is a scientific American 60 Second Science. I'm Suzanne Bard.

Switching on the lights at night is second nature to most people in the developed world,

but electricity isn't a given in many other

parts of the globe. Something like a billion people on our planet still lack

reliable access to electricity. Think about folks in parts of the developing world that are living in off-grid

locations and for them one of the central applications of electricity is lighting and we need

lighting the most at night.

UCLA material scientist Ashwath Raman.

Solar cells can provide remote areas with electricity during the day,

but require batteries to store that energy for use at night.

Raman's team has developed a potential solution, a simple thermal electric device

that generates power when it's exposed to the cold night sky.

It's made possible by a phenomenon called radiative sky cooling.

All objects, Raman explains, radiate heat.

And so what that means from the perspective of a surface that's looking up at the night sky

is that it will all by itself send out more heat than the sky sends back to it. It escapes to the upper

atmosphere and even out to outer space. And it's something that anyone can observe at night. So if you go and

measure the roof temperature on your house in the

early morning hours say you should read a temperature that is much lower than the

immediate ambient air temperature. Raman reasoned that this temperature difference could be exploited to generate electricity.

His team built their device using an aluminum disk that acts as a radiative cooler.

Its cool side faces the night sky,

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