Low-cost device generates electricity using natural cooling phenomenon

When frost forms on the ground overnight even when temperatures are well above freezing, or water droplets appear on car windshields even on a clear night, the cause is often a phenomenon called radiative sky cooling. In a paper published in the journal Joule, researchers led by a UCLA materials scientist report that they have leveraged the principles behind radiative sky cooling to develop an innovative way to produce renewable energy at night. The approach could be adapted into a low-cost technology that could eventually be a boon for the more than 1 billion people around the world who, according to the International Energy Agency, lack reliable access to electricity. The concept could be used as a standalone technology or work in combination with solar energy to produce electricity throughout the day and night. Radiative sky cooling is a natural phenomenon in which a surface that faces the sky ejects its heat into the air as thermal radiation. Some of that heat eventually rises to the upper atmosphere and then into colder reaches of space. "This effect occurs naturally all the time, especially on clear nights," said Aaswath Raman , an assistant professor of materials science and engineering at the UCLA Samueli School of Engineering who led the study.