According to the Solar Energy Industry Association, US solar power usage increased by 38 percent in 2014. The environmentally friendly technology is constantly being investigated and refined.
A major inefficiency of solar cells is the more heat they absorb, the less efficient their ability to convert solar energy into electricity. Now, scientists at Stanford University in Stanford, California, say they have solved the problem with a newly developed transparent overlay that increases conversion by cooling the cells–even in full sunlight.
The overlay is a thin, patterned silica material laid on top of a traditional solar cell. It is “transparent to the visible sunlight that powers solar cells, but captures and emits thermal radiation from infrared rays,” a statement in Stanford News said.
Fan and colleagues say they were inspired by the basic phenomenon of infrared light. Individuals emit heat in this form from the top their heads into space. This type of electromagnetic radiation falls in the electromagnetic spectrum between microwaves and visible light.
“Solar arrays must face the sun to function, even though that heat is detrimental to efficiency,” explains co-author Shanhui Fan, a professor of electrical engineering at Stanford, in the university statement. “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.”
To test their new technology, the researchers designed a custom-made solar absorber. This device mimics the properties of a solar cell without producing electricity. The absorber is covered with a micron-scale pattern, which maximizes the capacity to emit heat–as infrared light–into space. The overlay permits visible light to reach the solar cells while cooling the underlying absorber by as much as 23 degrees Fahrenheit, the statement said.
The team believes that the technology has significant potential for any outdoor device that needs to remain cool but requires preservation of the visible spectrum of sunlight for practical or aesthetic reasons.