PV panels track the sun, passively

Thanks to a new carbon nanotube-based system, these PV panels can follow the sun's movement without drawing on the energy they harvest.

“Om Suryaya Namah”: the Vedic mantra which places the energy of the sun at the core of spiritual awakening. Also bowing to the source of all life – or rather raising its face – is the sunflower, which rotates from east to west through the day to absorb maximum light.

Now, an electrical and computer engineer from the University of Wisconsin-Madison, Hongrui Jiang, has developed solar panels that mimic the sunflower’s motion, increasing their efficiency by 10%.Jiang isn’t the first to develop sun-seeking panels, but his are the first to track the sun passively – without using energy. Current systems rely on GPS and motors to realign the panels with the sun’s position, but use 2-3% of the energy collected by the panels, whereas the new system responds to the heat generated by the sun. These energy savings give the new system a competitive edge, Jiang believes.

The system comprises a solar panel with mirrors underneath, each focusing on an actuator comprised of carbon nanotubes, which absorb a wide range of light wavelengths from visible to infrared, and a liquid crystalline elastomer (LCE), which shrinks upon heating. When the sun directly hits a mirror, the carbon nanotubes absorb the light and heat up, increasing the temperature difference between the actuator and outside environment. The LCE shrinks, forcing the entire system to bow towards the strongest sunlight. As the sun moves, different actuators shrink whilst others cool and re-expand, letting the panels follow the sun.

With a prototype in place, Jiang and his team are exploring ways to refine their materials for use in larger solar panels, with a view that, in 5-10 years’ time, it will be ready for large-scale use in industrial solar farms. The team is now seeking funding for further work.
Professor Philip Jennings, an expert in photovoltaic efficiency at Murdoch University, Australia, is impressed by the advancement: “The idea is clearly feasible and the materials required are relatively inexpensive and widely available. The efficiency improvement is impressive ... [and] the invention has clearly passed the first test of ‘proof of concept’. The challenge now is to show that it is cost effective.” – Eleanor Devenish

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