One of the biggest challenges facing solar technology is that solar panels lose efficiency when they heat up — a problem since these devices also need to be faced toward the sun to best generate electricity. A number of cooling systems have been developed to help mediate this problem, but so far all of these systems focus on cooling down the panels.
A team of Stanford researchers had a different idea: What if you could cool down the sunlight itself? It sounds anti-intuitive, but they have invented a system that does exactly that, by separating the heat in sunlight from the light, reports Stanford News.
The key principle in the system works in a way analogous to how your own body radiates heat. As you walk around on a daily basis, heat from the top of your head radiates into space as infrared light. So the Stanford researchers devised a transparent coating comprised of patterned silica that lets visible sunlight through, but which captures and emits the thermal radiation from the infrared rays.
"Solar arrays must face the sun to function, even though that heat is detrimental to efficiency," explained Shanhui Fan, a professor of electrical engineering at Stanford. "Our thermal overlay allows sunlight to pass through, preserving or even enhancing sunlight absorption, but it also cools the cell by radiating the heat out and improving the cell efficiency."
The team tested their sunlight-cooling system on a custom-made solar absorber — a device that mimics a solar cell without actually producing electricity — positioned on a Stanford rooftop. They found that the absorber was cooled by as much as 23 degrees Fahrenheit thanks to the coating. That essentially translates into a 1 percent increase in solar efficiency. That might not sound like a lot, but it is actually quite significant in terms of overall energy production.
The technology could also have applications beyond improving solar cell efficiency. For instance, it could help keep darker-colored cars cool as they sit in the sunlight. Windows coated in the silica material could also let in light without letting in the heat.
Researchers hope that further developments in the technology will also improve its effectiveness, which will make solar energy more feasible than ever before.