Brian Willis in bimolecular and chemical engineering holds a rectenna device on  Jan. 29, 2013. (Sean Flynn/UConn Photo)

Efficient solar ‘antenna’ to tune in to the sun

Gerard     February 6, 2013     Featured, Sci-tech

If it’s up to Brian Willis, we will soon quite literally be tuning in to the sun. The University of Connecticut professor has patented a technique to manufacture nanosized antenna arrays that have the capability to efficiently convert sunlight into usable electric power.

In theory, these very small antenna arrays can harvest over 70 percent of the sun’s electromagnetic radiation and convert it into electric power. They are called “rectennas” due to their ability to absorb the alternating current induced by electromagnetic waves (sunlight) and directly rectify it to direct current. In contrast to existing solar silicon solar panels which mainly work within a specified band gap, rectennas can be tuned to harvest sunlight in the whole solar spectrum which makes it very efficient.

Brian Willis, a University of Connecticut engineering professor, was able to discover a way to manufacture a working rectenna device. The process is called selective area atomic layer deposition (ALD) and it can precisely coat the tip of the device with layers of individual copper atoms to achieve a gap of about 1.5 nanometers, a critical size because this creates an ultra-fast tunnel that enables the maximum transfer of electricity.

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A graphic illustration of a working nanosized optical rectifying antenna or rectenna. (Image courtesy of Brian Willis)

A graphic illustration of a working nanosized optical rectifying antenna or rectenna (image courtesy of Brian Willis)

ALD can be successfully used to create this very tiny gap, whereas existing lithographic fabrication methods have been unable to create this distance between the two interior electrodes. To put this in perspective, this extremely small distance is 30,000 times smaller than the human hair’s diameter. The appeal of ALD is its simplicity, reproducibility, and scalability for mass production. ALD can also be used in other areas including thermoelectrics, infrared sensing, and chemical sensors. It is hoped that this technology can one day help solar energy achieve cost-parity with fossil fuels.

Willis is collaborating with scientists from Penn State Altoona to build a prototype rectenna and test the efficiency in an effort to further fine tune the technology. “We’ve already made a first version of the device,” Willis said. “Now we’re looking for ways to modify the rectenna so it tunes into frequencies better. I compare it to the days when televisions relied on rabbit ear antennas for reception. Everything was a static blur until you moved the antenna around and saw the ghost of an image. Then you kept moving it around until the image was clearer. That’s what we’re looking for, that ghost of an image. Once we have that, we can work on making it more robust and repeatable.”

For more information, see this UConn blog post about Willis’ research.

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