The hotter solar cells become, the less efficient they are at converting sunlight to electricity, a problem that has long vexed the solar industry. Now, Stanford engineers have developed a transparent overlay that increases efficiency by cooling the cells even in full sunlight.
A transparent material that can improve the efficacy of solar cells has been invented by three Stanford engineers. The new coating has the tendency to radiate thermal energy into space which is released by solar cells, making cells cool.
Image credit: Stanford
When laid over a solar cell, the transparent material shown here can radiate heat away from solar cells, allowing them to produce electricity more efficiently.
Shanhui Fan, a professor of electrical engineering at Stanford, research associate Aaswath P. Raman, and doctoral candidate Linxiao Zhu, collectively worked to improve the theory that hotter solar cells get less efficient in converting photons into electricity. The newly developed transparent coating is made up of thin, patterned silica material. It works by capturing intense heat or thermal radiation from infrared rays and emitting them into the atmosphere.
“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”, said Fan. An ultrathin material that can radiate infrared heat directly back toward space without warming the atmosphere was also developed by the three engineers in 2014.
The trio termed their invention ‘radiative cooling’ as it can directly shunt thermal energy into a deep cold void of space. In an experiment conducted on a custom-made solar absorber, the engineers found that the thin coating of micron-scale pattern cooled solar cells temperature by approximately 23 degrees Fahrenheit. It has been reported that 23F of cooling would improve the efficiency of a typical crystalline silicon solar cell, with an efficiency of 20%, by 1%.
Engineers stated that their invention would prove beneficial in the nano print lithography technique used to develop nanometer-scale patterns. They added that the new thermal coating could prove best when used in dry, clear environments.