World's First Optical Rectenna Turns Light Into Electricity

In the world's quest for renewable energy sometimes the most abundant resources are overlooked. It can be right there all along staring you in the face. Maybe you just don't see it or maybe you haven't figured out a way to harness it yet, but it's there nonetheless. That appears to be the case with light, one of the most prevalent resources available to us on the planet. Researchers at Georgia Tech have recently discovered how to create electricity from light with the very first optical rectenna.

What's an optical rectenna, you ask? Well, it has nothing to do with Cartman on South Park, if that's where your mind was going. The Reader's Digest version or, perhaps even better, the Jeopardy clue to the answer is: a small device composed of tiny multiwall carbon nanotubes and rectifiers that capture light and turn it into a direct DC current.


Optical Rectenna Turns Light Into Electricity: Device key to unlocking unlimited renewable energy sourceOptical Rectenna Turns Light Into Electricity: Device key to unlocking unlimited renewable energy source


Unlimited Renewable Energy

Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure that act as antennas attracting light. It's important to note here that this is virtually any light. It doesn't have to be direct sunlight in order for the process to work. This produces an oscillating charge. Those charges move through a rectifier built into the walls of the nanotubes and switch on and off at extremely high rates of speed. Ultimately, those pulses create a small electrical current.

There's a possibility it might also be used to create electricity from waste heat. Regardless of whether it can or not, the outcome with light is clean, renewable energy that, when banded together with billions of other rectennas, can generate a much more substantial current. You see where we're going with this; right?

Limited Technology

Right now the only fly in the ointment is that as the devices stand now they are less than 1 percent efficient in their functionality. This means that negligible increments of light are actually being converted directly into electrical current. But this doesn't have researchers worried. The process still has immense promise. So much so that the team is already looking into developing ways of increasing that number exponentially. Presently, they are investigating techniques to reduce the electrical resistance within the devices in order to provide up to 40 percent efficiency or higher.

Rectennas are not actually new. The concept was originally investigated in the 1960s. Due to their obvious potential and low cost, scientists fortunately did not abandon the research. It just took them decades to make the components small enough for their intended purposes.

Future Applications for Green Technology

Once an increase has been accomplished, the application that seems the most obvious for advancement of the technology would be harvesting solar energy. Team member Baratunde Cola, an associate professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech, was noted as saying, “We could ultimately make solar cells that are twice as efficient at a cost that is ten times lower, and that is to me an opportunity to change the world in a very big way."

The inexpensive carbon nanotubes are lightweight with a unique tensile strength, making them especially well suited for this project. While there are still a number of "ifs" involved, when this technology is improved and a higher capacity is eventually reached there is the distinct possibility the device will be the key to unlocking unlimited renewable energy resources.