An unconventional approach to cooling sends heat to the cold sky. Air conditioning accounts for almost 15 percent of all energy use by buildings in the United States. One way to cut that is to send heat to outer space, according to Aaswath Raman . Raman is the cofounder of a new company called SkyCool Systems . The startup, spinning out of Stanford University, is one of several groups commercializing an energy-efficient cooling approach that takes advantage of the coldness of space. The idea is to exploit a natural phenomenon called radiative cooling. All objects emit thermal radiation. When it’s emitted toward the sky, a portion of it is absorbed and reflected by the atmosphere. Another portion, which falls within a particular range of frequencies, escapes into the upper atmosphere and outer space, where conditions are much colder. This can cause the object emitting that radiation to cool to […]