The system helps cool its surroundings by absorbing heat from the air inside the box and transmitting that energy through the Earth's atmosphere into outer space. Source: University at BuffaloEngineers from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, the University of Buffalo and the University of Wisconsin-Madison have devised a new passive cooling system that does not use electricity.

The new system is composed of a polymer-aluminum film installed inside a box at the bottom of a "solar shelter." The film absorbs ambient heat inside the box, according to researchers. The energy is then released as thermal radiation back into Earth's atmosphere. This keeps the polymer film and surrounding area cooler than without the solar shelter.

Generally, thermal emissions travel in all different directions, but through the design of the solar shelter — with four solar energy-absorbing, outward-slanting walls housing an inverted square cone — the team devised a way to beam the emissions in a specific upward direction, making the design appropriate for cities where tall buildings are all around.

"The polymer stays cool as it dissipates heat through thermal radiation, and can then cool down the environment," said co-first author Lyu Zhou, a Ph.D. candidate in electrical engineering in the University at Buffalo School of Engineering and Applied Sciences. "This is called radiative or passive cooling, and it's very interesting because it does not consume electricity — it won't need a battery or other electricity source to realize cooling."

The solar shelter system is roughly 18 in tall, 10 in wide and 10 in long. To cool an entire building, many shelters would need to be installed.

The research is published in the journal Nature Sustainability.