Sunflowers naturally follow the sun across the sky during the day.
“I was thinking about how to increase the overall energy output from the solar cell,” said professor Hangrui Jiang. “And heliotropism is an elegant way from nature.”
But Jiang wanted to come up with a natural way to do it. “I had the artificial heliotropism (an application) in mind first,” Jiang writes in an email. “And then tried to develop materials to realize the actuators.”
The material Jiang and his team designed combines a rubbery material called liquid crystalline elastomer with tiny carbon fibers, according to a release from the university. The fibers absorb a wide range of light, including light waves in the visible and infrared spectrums.
When sunlight falls on the carbon fibers, they heat up. The difference in temperature between the hot carbon fibers and the cooler outside air causes the liquid crystalline elastomer to shrink. When the sun moves on, the material cools and expands again to its original size.
The expansion and contraction causes the system to rotate with the sun. “It would be a new solar tracking method,” Jiang writes. “It doesn't affect the solar panel per se.”
That means the tracking system could be used to enhance the performance of any solar panel. Jiang estimates that the tracking system increases solar panel productivity by 10 percent. Since Jiang and his team are just in the early phases of their research, he said he’s not certain what its competitiveness with mechanical tracking systems will be.
“Hopefully this would ultimately need less maintenance,” he said. “This is fresh from research lab, so there is much work needed to push it towards commercialization, such as developing more sensitive (to sunlight) actuators, larger tracking range, robustness, longevity, etc.”