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New cooling device works without power

Press Trust of India  |  Boston 

scientists, including one of Indian origin, have developed a cooling device that can preserve and medications in hot, remote locations without or fossil fuel-generated power.

The system allows emission of heat at mid-infrared range of light that can pass straight out through the atmosphere and radiate into the cold of outer space, punching right through the gases that act like a greenhouse, researchers said.

To prevent heating in the direct sunlight, a small strip of suspended above the device blocks the Sun's direct rays.

The system, described in the journal Nature Communications, could in theory provide cooling of as much as 20 degrees Celsius below the ambient temperature in a location like Boston, researchers said.

So far, in their initial proof-of-concept testing, they have achieved a cooling of six degrees Celsius.

Other groups have attempted to design that radiate heat in the form of mid-infrared wavelengths of light, but these systems have been based on complex engineered that can be expensive to make and not readily available for widespread use.

The devices are complex because they are designed to reflect all wavelengths of sunlight almost perfectly, and only to emit in the mid-infrared range, for the most part.

That combination of selective reflectivity and emissivity requires a multilayer material where the thicknesses of the layers are controlled to nanometre precision.

"We built the setup and did outdoors experiments on an rooftop. It was done using very simple materials" and clearly showed the effectiveness of the system," said Bikram Bhatia, a at (MIT) in the US.

One limiting factor for the system is humidity in the atmosphere, which can block some of the infrared emission through the air.

In a place like Boston, close to the ocean and relatively humid, this constrains the total amount of cooling that can be achieved, limiting it to about 20 degrees Celsius, researchers said.

However, in drier deserts or arid environments around the world, the maximum achievable cooling could actually be much greater, potentially as much as 40 degrees Celsius, they said.

While most research on radiative cooling has focused on that might be applied to cooling entire rooms or buildings, this approach is more localised, said Evelyn Wang, a at

"This would be useful for refrigeration applications, such as storage or vaccines," she said.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)

First Published: Thu, November 29 2018. 11:05 IST
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