Solar researchers have spent years trying to develop a solution to this problem, and Stanford is perhaps at the top of the list when it comes to new developments.
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“Solar arrays must face the Sun to function even though that heat is detrimental to efficiency”, Fan said. The coating is transparent to the visible sunlight that charges the solar cells but it is able to captures and emitthermal radiationor heatfrom infrared rays.
A transparent material that can improve the efficacy of solar cells has been invented by three Stanford engineers. Latest among its efforts is a new thin material that can be laid over traditional solar cells to reduce heat exposure.
A major inefficiency of solar cells is the more heat they absorb, the less efficient their ability to convert solar energy into electricity. This material radiates infrared heat directly into space without increasing the temperature of the surrounding air. The tests showed that the coating allowed only visible light to pass through to the solar cell, filtering out the thermal radiation, keeping the temperature as low as 23 degrees Fahrenheit.
Testing of the transparent overlay on a custom-made solar absorber that mimics a solar cell without generating electricity cooled the absorber by as much as 13 degrees Celsius. They also believe that this overlay can be upgraded to make them more compatible with commercial and industrial requirements.
The university’s website notes that the coating would work best in a dry, clear environment-but that’s also preferred for large solar sites, so it works out.
That’s not necessarily the only way. New techniques and machines for manufacturing these kinds of patterns will continue to advance.
Researchers also said that the technology could be applied to any outdoor device or system – such as a vehicle – that needs cooling. Thermal overlays can help with passive cooling, but it’s a problem if they’re not fully transparent.
“Our photonic crystal thermal overlay optimizes use of the thermal portions of the electromagnetic spectrum without affecting visible light”, said electrical engineering professor Shanhui Fan.
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The research was detailed in the journal Proceedings of the National Academy of Sciences.
