Stanford University researchers are using unique solar panels to cool water so it can be used in an air conditioning system to reduce the costs of air conditioning and refrigeration by cooling without using electricity. Now they’re forming SkyCool Systems to test and commercialize their radiative sky cooling technology.
“If you have something that is very cold—like space—and you can dissipate heat into it, then you can do cooling without any electricity or work. The heat just flows,” said Shanhui Fan professor of electrical engineering and senior author of the research, which was published in Nature Energy today (Sept. 4). “For this reason, the amount of heat flow off the Earth that goes to the universe is enormous.”
Others have used solar power to cool buildings or to even store solar energy in ice. But the materials being developed at Stanford actually cool things directly. Fan’s research has also created a material that could eventually be woven into clothes made to cool people in hot environments, for example.
However, sunlight warms things more than radiative cooling can cool them down. Fan and his research team created a multilayer optical film that can reflect 97 percent of sunlight and emits the surface’s thermal energy through the atmosphere. The materials in the device can then cool things, like water, below air temperature even on a sunny day without using electricity.
“With this technology, we’re no longer limited by what the air temperature is, we’re limited by something much colder: the sky and space,” added Eli Goldstein, a former research associate of Fan’s and co-lead author.
The researchers formerly published research showing their device could cool surfaces. But now they’re able to show how it can actively cool water. They tested it on Stanford’s Packard Building in September 2015 with panels that are about 2 feet long, with up to four systems working at a time. They showed that even with water moving at a relatively fast rate, the panels consistently reduced water’s temperature by 3 to 5 degrees Celsius below ambient air temperature.
“This research builds on our previous work with radiative sky cooling but takes it to the next level. 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,” said Fan’s former research associate Aaswath Raman, who is co-lead author of the research.
SkyCool Systems has integrated its system into traditional air conditioning and refrigeration systems at a test facility where they are focussed on making sure the system can be integrated easily into traditional air-conditioning systems in the hopes of one-day applying it places like data centers. The researchers also theorized that if a two-story commercial office building in Las Vegas used its technology with a vapor-compression system and a condenser cooled by their panels as opposed to a conventional air-cooled chiller, it could cut electricity use by 21 percent.Tweet