Latest research claims that ultra-white BaSO4 reduces urban heat island effect by reflecting the sunlight.
So, what’s urban heat island effect? Due to urbanization, i.e., building industries, roads, pavements, towers, cars, etc., more heat is being trapped onto the surface which is the key factor for higher temperature compared to the surrounding, depicted below.
Many approaches were made to combat this, using heat-reflective paints but that had few limitations viz. large thickness, cost, complicated structures, involvement of metallic layer, etc. which precluded them from its applications.
Recent research led by Xiulin Ruan and team, from Purdue University published in the journal ACS Applied Materials & Interfaces, developed ultra-white paint using BaSO4 (Barium sulphate) which showed excellent complete-daytime effective cooling by reflecting the sun’s heat to outer space- called radiative cooling.
Previously these scientists examined CaCO3 as a filler material to make a paint which showed consistent cooling effect of 1.70C less than the surrounding temperature whereas newly developed BaSO4 paint showed 4.50C less than the surrounding temperature.
Because of its low solar absorptance (fraction of sunlight that is absorbed), most of the light falling on surface is reflected which was the key factor for choosing BaSO4. Initially, BaSO4 nanoparticle film was made, later for reliability BaSO4 acrylic paint was created using 60% volume concentration of BaSO4 with white paint. Along with this, varying particle size of BaSO4 are added to enhance photon scattering, thus increasing solar reflectance (fraction of sunlight reflected) to 98.1%
So, what’s new about this innovation?
Well, due to its cooling effect, it can reduce global warming, carbon emissions from air conditioners during summer and saves energy for cooling (coolers, fans, etc) over 80 Wh/m2/day converting into a monthly cost, it can save $36 for a 150 m2 house. In addition to that, it will also alleviate urban heat island effect!
Finally, the authors concluded that BaSO4-acrylic paint is the most effective in radiative cooling solutions while giving great reliability, ease of use, convenient paint form, and compatibility with the commercial paint fabrication process.
Reference:
Li X, Peoples J, Yao P, Ruan X. Ultrawhite BaSO4 Paints and Films for Remarkable Daytime Subambient Radiative Cooling. ACS Appl Mater Interfaces. 2021 May 12;13(18):21733-21739. doi: 10.1021/acsami.1c02368. Epub 2021 Apr 15. PMID: 33856776.
Content by: Vindhya Regonda
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