Ever since the discovery of chlorofluorocarbons (CFCs) as a root cause for Ozone layer depletion in the 1980s, the once-lauded compound became a nuisance. It was used ubiquitously as a cheap and easy cooling agent in a variety of products – from air conditioners to refrigerators to aerosol cans. While scientists have tried to eliminate its use, the non-CFC models still cost a lot in both productions and consumption of electricity.
However, researchers at Purdue University may have come with a cost-saving alternative to using air-conditioners. As people are gradually becoming more aware of the environmental damage caused by our energy consumption (even without the CFC products), this invention might be appreciated by environmentalists. The team has created a white paint which can allegedly keep surfaces up to 18ºF (10ºC) cooler than the ambient temperature. The study was published in the journal Cell Reports Physical Science.
The newly-developed paint can help maintain a lower temperature, much like ACs, even under direct sunlight as they reflect more ultraviolet rays as compared to commercial white paint. While there are many commercial heat-rejecting paints available in the market, the researchers claim they fail to achieve temperatures below their surroundings as they reflect only 80%-90% of sunlight. Whereas they claim, their new paint can reflect 95.5% sunlight and even radiate infrared heat efficiently.
According to Coolingpost.com, the development of this paint was very difficult. The study continued for more than six years, and the first attempts of developing a radiative cooling paint as a feasible alternative to traditional air conditioners go back to the 1970s.
The original pool of options had more than 100 different material combinations. They finally dialled it down to 10 and tested about 50 different formulations for each material. The final combination that worked for them relied heavily on calcium carbonate. Chemical sign CaCO3 – the compound is abundant on earth commonly present as chalk in rocks or seashells, etc.
The CaCO3 acts as a filler in the paint. The rest of the formula has properties much like the commercial white paints but more enhanced when it comes to cooling. The calcium carbonate fillers don’t absorb any UV ray as they have a large “band-gap”; a feature of their atomic structure. Different sized particles in the structure allow the paint to scatter into various wavelengths and reflect away the heat.