Rising temperatures around the world run the risk of creating a dangerous cycle where more people get air conditioning, which causes energy demand to surge and leads to higher carbon emissions, which makes temperatures rise even more. Renewable power is one option for breaking that cycle, but people have also been studying materials that enable what’s called passive cooling. Without using energy, these materials take heat from whatever they’re covering and radiate it out to space.
Most of these efforts have focused on building materials, with the goal of creating roofs that can keep buildings a few degrees cooler than the surrounding air. But now a team based in China has taken the same principles and applied them to fabric, creating a vest that keeps its users about 3º C cooler than they would be otherwise.
Built to chill
Whenever something’s out in the sunlight, it’s going to absorb some of those photons, which will get converted into heat. That heat can then be radiated back out in infrared wavelengths. The problem is that this doesn’t actually cool things down much. Lots of the gasses in the atmosphere immediately absorb the infrared light, trapping the energy as heat in the immediate vicinity of the object. If the object is a person, there’s the added issue of heat generated by their metabolism, which is also getting radiated away in the infrared at the same time.