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Nano-Antennas for Solar, Lighting, and Climate Control

Written by Hank Green on 07/02/08

Last week EcoGeek stumbled across a little story about some little antennas that could, just maybe, revolutionize not just the solar industry, not just the energy industry, but the whole entire world.
Well, we thought there was a bigger story there than we could get from one press release, so we contacted the scientists behind the project and it turned out we were right. Dr. Steven Novack took some time to tell us about his nano-antenna (or has he calls them, nantenna) arrays, and some of their potential applications.
I was blown away.
The original article discussed how nantennas could be used as a solar panel that could beat all current efficiencies at a much lower cost. But it turns out that nanetennas have dozens of other uses, many fascinating for EcoGeeks. These include:

• Passive, energy-neutral cooling by converting infrared radiation into radiation that we don't feel as heat (like radio waves)
• Passive heating by turning radiation we don't feel as heat into infrared radiation
• Extremely efficient lighting by basically broadcasting photons from the nantennas. As it's basically the solar process in reverse (photons from electrons, instead of electrons from photons), this is just as feasible as the solar applications
• Passive heating or cooling within clothing
• Electricitiy production in clothing by harnessing our bodies' radiation.

Dr. Novack was kind enough to answer some of our questions. Keep on reading if you want to hear more about this fascinating technology, and where it's headed five, ten, and twenty years down the road.

EcoGeek: So tell me about your nano-antenna arrays.
Dr. Steven Novack: All antennas are very good at receiving and transmitting electromagnetic radiation. But the difficulty has been creating nantennas of the proper size to capture the wavelengths emitted by the sun. The ability to tune the antenna to the size of the wavelength is very important.
EG: Can you make these arrays pick up radiation throughout the sun's spectrum, or is it just one specific wavelength?
SN: We can do both; we're very good at tuning antennas to one specific frequency and very good at making them broadband.
However, INL is fairly new in this world of nanotechnology. Because of that, we're working to get a product out that would be easier for us to prototype. So we've selected a little bit longer wavelengths. As the technology progresses, we'll certainly be interested in moving that down to the visible range.

EG: Can you talk a bit about the materials that go into these new panels?
SN: Materials are fairly straightforward. We need some sort of substrate as a base, and we've chosen a plastic to keep costs low. We have a pattern that we stamp onto the plastic, and then we deposit certain kinds of metals. The metals have to have certain characteristics. For the research phase, we're focusing less on cost and more on the amount we know about them. The current prototype is being done with gold. The entire one foot by two foot sheet that we created used less than 60 cents of gold, but if we have to go to aluminum, copper, or silver, we could certainly do that.

EG: Right now there your nantenna array can't convert the energy it creates into a useful current. I've heard that you'll need another nano-electronic component to make that a possibility. Has there been progress in that area?
SN: A lot of scientists are working on nanoelectronics to support optical computing. There's been a lot of breakthroughs in the last year or so in terms of prototypes that can handle these types of currents. We have not yet attempted to integrate them into the array, but we're looking for strategic partners that can help us with that.
EG: So when you talk about mass production, how mass are we talking about?
SN: The manufacturing process is part of what we were recognized for in this year's Nano50 awards. We're pretty good at large-scale manufacturing, and we're hoping for roll-to-roll processing.
EG: Does this excite you more than just scientifically?
SN: This is probably one of the more socially significant projects that we've done. Obviously, with the world economy's need for cheap energy, we're hopefully going to make life better for everyone.That's definitely a driving force.
EG: So do you think about the environment as you work on this projects?
SN: When we think about manufacturing, we think about the materials and processes as well as the end result. The environment is a huge factor. We only look at stuff that fits our environmental criteria. There's no sense in trying to help the environment if the process creates a negative waste stream.

And then there's an overall concept of heat and entropy, and how much we waste our energy as heat.

Antennas that are good in receiving in an area are also very good at emitting in an area.
EG: So are you saying that these could be a light source as well as a light collector?
SN: There are some challenges to that concept that we're going to be working on. But with your imagination you can probably think of more applications than I can.
The first application I see is: "Here's a nice way to cool a room." The solar applications are probably more important, but we're a lot closer to that kind of passive temperature management.
EG: On that very exciting note, I'll just ask if you can think of any way to help our world stay sustainable.
SN: My personal hope is that we decrease world conflict by increasing availability of resources so that people can have a better life. There's a direct correlation there. And, of course, I'd love to see more emphasis put onto funding this type of work.