Stanford researchers are developing rooftop panels that cool buildings by sending heat back into space, a technique that could be more efficient than running an air conditioner from solar panels. 

Electrical engineering professor Shanhui Fan has designed a device which uses materials that allow him to manipulate how heat and light affect building temperature. He envisions flat rooftop panels which could greatly cut down on daytime cooling energy or be used to cool homes that don’t have access to grid power and air conditioning.

Fan co-authored a paper on the theoretical potential of a device that both reflects sunlight and emits heat using multiple layers of photonic materials. His team at Stanford was recently awarded a one-year, $400,000 grant from the ARPA-E research agency to build a demonstration to test its performance. The group is now building that prototype and hopes to eventually commercialize the technology.