An issue as serious and large as climate change can make us feel overwhelmed and helpless. The Eco-Justice team will periodically highlight examples of ingenuity, de-termination and hope that can strengthen us in the effort. Here’s one example:
Long ago, people who lived in warm climates got ice from the heavens. Desert dwellers in North Africa, India, and Iran used a physics phenomenon called radiative cooling to make ice, even though the air temperature never got below freezing. At sunset, they would pour water into shallow clay trays or earthen pits lined with reeds. On a clear, starry night, the earth, giving up heat from all objects on it, would radiate that heat out of the atmosphere itself, leaving behind the absence of heat, which is coldness.
Scientists have long known about that effect, but assumed it was too difficult to capture it in the daytime, when the earth is absorbing heat from the sun. Then a materials scientist at UCLA named Aaswath Raman found a loophole in the greenhouse effect.
The visible light we see comes from electromagnetic waves in the short violet to longer red range, while the radiant heat we feel comes from the even longer, infrared part of the spectrum. There are “windows” in the atmosphere where electromagnetic waves of just the right length can slip through. Raman’s task was to find objects that would emit only those waves of the right length to slip through. With colleagues in Stanford’s engineering department, led by professor Shanhui Fan, he began developing a film made from many microscopic layers. The composition and thickness of these layers were designed to interfere with the way different wavelengths of light travel. This involved manipulating their materials, molecule by molecule.
After years of work the team had a prototype, but they still had to figure out how to make it useful in the world outside the lab. Their goal was to make it both inexpensive and able to integrate into existing air-conditioning units. They formed a company called SkyCool Systems. The company produces SkyCool panels in which water, cooled by the film, cools the refrigerant in an existing cooling system.
Last spring, Jesus Valenzuela, store manager of the Stockton, Calif., Grocery Outlet, agreed to test the panels. Over the summer they saved him $3,000. He doesn’t quite understand how the panels use outer space to help cool his grocery store, but he isn’t concerned. “All I know,” Valenzuela says, “is that it’s saving me money.”