I think it’s safe to assume that most people out there know that plants tend to grow towards the direction that they receive the most sunlight. This phenomenon is amplified in sunflowers, which can be seen following the sun across the sky in real time. I imagine that it didn’t take long for some engineer to figure out that solar panels could be much more efficient if they were pointed at the sun at all times. That part isn’t exactly rocket science.
What is a bit tricky, however, is how to go about rotating giant solar panels throughout the day. There are systems in place today that track the sun using GPS and automatically rotate the solar panels using a system of hinges and motors. Obviously, some of the gained efficiency is lost due to having to power the motors, and the systems can be bulky and rather inconvenient.
Surely there must be a better way?
In a recent paper published August 1 in Advanced Functional Materials and recently highlighted in Nature, Hongrui Jiang has found a new solution. The professor of electrical and computer engineering at the University of Wisconsin has turned to a new type of material called liquid crystalline elastomer (LCE) to get the job done.
Liquid crystals are complex and weird materials. Though they flow like water, over long distances they have a regular, organized molecular structure like a crystal. Throw in the ability of molecules to “hook” together to enable deformation without breaking – like rubber – and you have an even weirder material. So weird, in fact, that it’s only been around in labs for a couple of years.
One of the materials properties that Jiang took advantage of is its ability to deform in response to heat. In his new system, Jiang laced LCE with carbon nanotubes, which heat up extremely well when exposed to sunlight. When heated, the nanotubes cause the LCE to contract. By placing this material in actuators across the structure of a solar panel, the entire system can move in concert with the sun. Mirrors beneath the system direct sunlight onto the actuators, with the amount of sunlight received varying throughout the course of the day due to the sun’s position.
Without any motors sucking up electricity or large, cumbersome gears, Jiang managed to increase the solar panel’s efficiency by 10 percent – a huge leap in the realm of solar energy.
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.
Big Ten Science 