Cooling and refrigeration account for roughly 10% of the total electricity consumption in the world. This is because mainstream cooling and refrigeration technologies rely on equipment that consumes a lot of energy. Yuan Yang, an assistant professor at Columbia University, turned to daytime radiative cooling, a new refrigeration technology that produces cold energy without electricity. For buildings, successful radiative cooling means reducing the heat input by reflecting the incident solar radiation to the maximum and increasing heat dissipation by emitting infrared light to the sky as much as possible. If an object can reflect more than 95% of the solar energy and has an infrared light emissivity of 0.95, it can be cooler than the ambient even when exposed to direct sunlight. To achieve that, Yuan found a perfect coating material: porous media. He developed a simple, low-cost, paint-like polymeric coating that has ultrahigh solar reflectance (96-99.6%) and ultrahigh thermal emittance (0.97), which can achieve sub-ambient cooling of 5-10 °C even under strong solar irradiation of 1000W per square meter.
In the field of advanced battery technology, he has developed a method to improve the interfacial stability between the solid electrolyte and the lithium metal anode, which can significantly enhance the cycle life of solid batteries. He also invented a variety of flexible batteries, whose energy density can reach 80-90% of lithium-ion batteries with the same size. His flexible batteries can ensure sufficient thickness and capacity, as well as enough flexibility at the same time. In the future, this kind of battery can be used to make the strap of a smartwatch, to significantly reduce the thickness of the dial, increase the battery life, and enable high-energy consuming functions like 5G connection and video calls.