WASHINGTON, Dec. 11 (Xinhua) -- American engineers developed a device with cheap optics that can soak up heat from sun to produce steam hotter than 100 degrees Celsius.
The study published on Tuesday in Nature Communications described a suspended device over the water like a sandwich: Its top layer is made from a material that efficiently absorbs the sun's heat, while its bottom layer efficiently emits heat to the water below.
On a sunny day, the structure can passively pump out steam hot enough to sterilize medical equipment, and to use in cooking and cleaning, according to the study.
The steam may also be collected and condensed to produce desalinated, distilled drinking water.
Once the water reaches the boiling point, it releases steam that rises back up into the device, where it is funneled through the middle layer, a foam-like material that further heats the steam above 120 degrees Celsius, before it's pumped out through a single tube, according to the study.
The device, about the size and thickness of a small digital tablet, is structured to absorb short-wavelength solar energy, which in turn heats up the device, causing it to reradiate this heat, in the form of longer-wavelength infrared radiation, to the water below.
The researchers have found that infrared wavelengths are more readily absorbed by water than solar wavelengths that would simply pass right through.
"You just leave it outside to absorb sunlight," said Thomas Cooper, assistant professor of mechanical engineering at York University, who led the work as a postdoc at Massachusetts Institute of Technology (MIT).
"You could scale this up to something that could be used in remote climates to generate enough drinking water for a family, or sterilize equipment for one operating room," said Cooper.
In another experiment, the team managed to produce steam from sea water, without contaminating the surface of the device with salt crystals.
"This design really solves the fouling problem and the steam collection problem," said Chen Gang, a professor of power engineering at MIT and a co-author of the study.