A team of IIT researchers have created an alternative for regular air conditioners that can function without any power using the radiative cooling systems.
The IIT researches created an alternative to AC with passive radiative cooling systems. These passive radiative cooling systems emit the heat absorbed from the surrounding in the form of infrared radiations. These can pass through the atmosphere easily and get dumped into outer space. These cooling systems can be installed on the rooftops and can prevent pollution.
Challenges in Implementation:
Radiative cooling systems can work at night; however, they cannot emit the actually absorbed radiation. The material should be able to reflect the solar and atmosphere radiation for it to be more effective during the daytime. Since the absorption rate is higher during the day, the material does not serve its purpose to the fullest.
“For a radiative cooler to work during daytime, the material should reflect the solar and atmospheric radiations falling on it. Since the materials used in conventional coolers absorb more solar radiations and emit less during the day, those do not work during daytime. While daytime cooling can be achieved using polymer-based passive radiative coolers, oxidation degrades the polymers resulting in a limited lifespan,” Ashish Kumar Chowdhary, IIT Guwahati.
The researchers are working towards an alternative for the cooling material. Thin films of silicon dioxide and aluminum nitride can be a better replacement as they have high optical density to the range of solar and atmospheric transmittance wavelengths. However, the increased optical density leads to increase in absorption, in turn reducing the life of the sheets.
“To address this, we considered using thin films of silicon dioxide and aluminum nitride. These materials have low optical density corresponding to the wavelength range of solar and atmospheric radiations. But at atmospheric transmittance wavelengths, they have high optical density. When optical density is high, radiations travel slower through a medium and get absorbed more. To remain at thermal equilibrium, the material emits all the absorbed radiations like a black body,” he added.