Columbia engineers develop pigment-free coating that kept surfaces 6°C cooler under Arizona sun

Porous polymer coating reflects sunlight and releases heat, keeping surfaces cooler than the air As temperatures rise during hot weather, keeping buildings and other structures cool can require large amounts of energy. Air conditioners are a common way to deal with the heat, but they consume electricity and need access to cooling systems and, in some cases, coolants that can affect the environment.Researchers at Columbia Engineering have created a polymer coating that can be applied like paint and uses microscopic air voids instead of white pigments. According to the University's engineering department, the coating can reflect sunlight while also releasing heat towards the sky, allowing the surface to cool below the surrounding air temperature.The researchers tested the coating in different environments. Under the warm, dry conditions of the Arizona desert, the coated surface became about 6°C cooler than the ambient air. On the ther hand, in a foggy, tropical environment in Bangladesh, it achieved cooling of about 3°C below the surrounding air.The work is based on a process called passive daytime radiative cooling (PDRC). It allows a surface to cool without using an external energy...