Staying cool during hot or humid weather without racking up a hefty electricity bill could be a reality in the near future. A team of researchers from Stanford University have developed a passive cooling system that sends excess heat towards outer space. Since almost no energy is required to keep them functional, these high-tech optical surfaces could one day help reduce the amount of electricity being consumed by air conditioners and refrigerators.

"This research builds on our previous work with radiative sky cooling but takes it to the next level," explained Shanhui Fan, lead researcher and professor of electrical engineering. "It provides for the first time a high-fidelity technology demonstration of how you can use radiative sky cooling to passively cool a fluid and, in doing so, connect it with cooling systems to save electricity."