A More Efficient Solar Energy Solutiuon Inspired by Sunflowers

Unlike other “active” solar sys­tems that track the sun’s posi­tion with GPS and repo­si­tion pan­els with motors, elec­tri­cal and com­puter engi­neer­ing pro­fes­sor Hongrui Jiang’s con­cept lever­ages the prop­er­ties of unique mate­ri­als in con­cert to cre­ate a pas­sive method of re-orienting solar pan­els in the direc­tion of the most direct sunlight.

His design, pub­lished Aug. 1 in Advanced Functional Materials and recently high­lighted in Nature, employs a com­bi­na­tion of liq­uid crys­talline elas­tomer (LCE), which goes through a phase change and con­tracts in the pres­ence of heat, with car­bon nan­otubes, which can absorb a wide range of light wavelengths.

“Carbon nan­otubes have a very wide range of absorp­tion, vis­i­ble light all the way to infrared,” says Jiang. “That is some­thing we can take advan­tage of, since it is pos­si­ble to use sun­light to drive it directly.”

Direct sun­light hits a mir­ror beneath the solar panel, focused onto one of mul­ti­ple actu­a­tors com­posed of LCE laced with car­bon nan­otubes. The car­bon nan­otubes heat up as they absorb light, and the heat dif­fer­en­tial between the envi­ron­ment and inside the actu­a­tor causes the LCE to shrink.

This causes the entire assem­bly to bow in the direc­tion of the strongest sun­light. As the sun moves across the sky, the actu­a­tors will cool and re-expand, and new ones will shrink, re-positioning the panel over the 180 degrees of sky that the sun cov­ers in the course of the day.

“The idea is that wher­ever the sun goes, it will fol­low,” says Jiang.

In Jiang’s tests, the sys­tem improved the effi­ciency of solar pan­els by 10 per­cent, an enor­mous increase con­sid­er­ing mate­r­ial improve­ments in the solar pan­els them­selves only net increases of a few per­cent on aver­age. And a pas­sive sys­tem means there are no motors and cir­cuits to eat into increased energy harvest.

“The whole point of solar track­ing is to increase the elec­tric­ity out­put of the sys­tem,” says Jiang.

The mate­ri­als dri­ving Jiang’s design have only been avail­able in the past few years, so for now, he and his team are research­ing ways to refine them for use dri­ving larger solar pan­els, where the net energy gain from his sys­tem will be the greatest.

But even­tu­ally, Jiang hopes to see huge indus­trial solar farms where fields of pho­to­voltaic solar pan­els shift effort­lessly along with the sun­flow­ers that inspired him.

“This is exactly what nature does,” says Jiang.

Source: University of Wisconsin-Madison release