IIT-Guwahati researchers design electricity-free radiative cooler

Researchers at IIT-Guwahati have designed an affordable and efficient ‘passive’ radiative cooling system that does not require electricity to operate.

This 'Radiative Cooler' coating material is an ‘electricity-free’ cooling system as it can be applied on the rooftops and functions both during day and night time to provide an alternate to the conventional air-conditioners, an IIT-Guwahati release said on Monday.

Passive radiative cooling systems operate by emitting the heat absorbed from the surrounding in the form of infrared radiations that can pass through the atmosphere before getting dumped into the cold outer space.

Most passive radiative coolers operate only at night and for daytime operation, these coolers need to reflect entire solar radiation as well. Till now, these cooling systems are not able to provide sufficient cooling at daytime.

A research team of IIT-Guwahati led by Ashish Kumar Chowdhary, Research Scholar at the institute, under the supervision of Prof Debabrata Sikdar, Assistant Professor, Department of Electronics and Electrical Engineering, has designed and modelled such a passive radiative cooler to resolve these issues and bring out an affordable and more efficient radiative cooling system that can operate round the clock.

Highlighting the unique aspects of this innovation, Prof Sikdar said, “Designing a passive radiative cooler for daytime operation is more challenging due to the simultaneous requirement of high reflectance in entire solar spectral regime (0.3–2.5 µm wavelengths) and high emissivity in the atmospheric transmittance window (8–13 µm wavelengths).”

“These radiative coolers requiring no external energy sources for their operation could be one of the best alternatives to replace the conventional air conditioning systems used to cool buildings and automobiles in countries experiencing hot weather, such as India,” he added.

The theoretical design of the radiative cooling system are tested and verified against rigorous computer-based simulations.

This patterning-free design of radiative cooler is large-area compatible and hence, also less prone to imperfections during fabrication process, the release said.

“The team hopes this will reach the market once the large-scale prototypes are developed and tested for operational stability and durability under different climatic conditions. They are now working towards this,” the release added.

The key advantages of this system in comparison to existing technologies include lithography-free and large-area compatible design and ensuring effective cooling during entire daytime without any need to adjust the angle or position of the cooler towards the sun.