As solar cells, particularly silicon photovoltaic (PV) cells produce energy in the heat of the day, they actually become less efficient at turning the sun’s photons into electrons and electricity in a sort of ironic twist. But researchers at Stanford University think they may have found a way to cool the cells, helping them increase their efficiency by harnessing nothing less than cooling power of the universe.
The Stanford researchers developed and tested a new material they said can that can cool a solar cell by up to 13° Celsius (55.4° Fahrenheit) during California’s winter. They posit that their cooling layer can increase the efficiency of PV cells by 1 percent, “a big boost from a relatively simple add-on,” they said. They added that it could also increase the longevity of the solar cells by reducing degradation. The researchers published their findings in the National Academy of Sciences last September (2015) and will present their results at the Conference on Lasers and Electro-Optics (CLEO) in San Jose, CA on June 9.
There’s another paradox behind solar cells and heat. While white and light colors can help cool things by reflecting light, solar cells must be dark to absorb as much sunlight as possible and producing as much electricity as possible, which increases heat on the devices and reduces efficiency.
The Stanford researchers focussed on an alternative means of cooling. “What’s unique about our work is that we demonstrate radiative cooling while preserving the amount of solar absorption,” said Linxiao Zhu, a graduate student in the research group of electrical engineering professor Shanhui Fan.
The team etched tapered holes, about 6 micrometers across and 10 micrometers deep, into a silica wafer—essentially manufactured quartz. The holes smooth the path allowing thermal radiation to escape while maintaining the absorption qualities of the solar cell.
Thus far the has only placed the layer on a mimic of a PV cell, basically a silicon device that wasn’t wired to transmit electricity. However they found that the device absorbed the same—if not—more sunlight.
Here’s where the universe comes in: Ultimately, radiative cooling relies on the coldness of the universe, which is a mostly untapped thermodynamic resource, according to Zhu. He and the team think the approach could be used to help cool other things as well, including cars, clothing, and outdoor equipment. However, the Stanford researchers will first test the device on actual PV cells. This is the latest potential solar innovation from the university, which has helped launch solar companies and partnered with other institutions like MIT to develop tomorrow’s solar cells.Tweet