Author Topic: Nano-rectenna solar arrays  (Read 4689 times)

Offline docmordrid

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Nano-rectenna solar arrays
« on: 02/27/2013 07:34 pm »
Still early in the game, but with a theoretical efficiency of up to 70% it could be significant for SEP spacecraft.

http://www.nanowerk.com/news2/newsid=29256.php#ixzz2M8JERF8k

Quote
New fabrication technique could provide breakthrough for solar energy systems

(Nanowerk News) A novel fabrication technique developed by a University of Connecticut engineering professor could provide the breakthrough technology scientists have been looking for to vastly improve the efficiency of today's solar energy systems.

For years, scientists have studied the potential benefits of a new branch of solar energy technology that relies on nanosized antenna arrays theoretically capable of harvesting more than 70 percent of the sun's electromagnetic radiation and simultaneously converting it into usable electric power.

But while nanosized antennas that also serve as rectifiers have shown promise in theory, scientists have lacked the technology required to construct and test them.
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The potential breakthrough lies in a novel fabrication process called selective area atomic layer deposition (ALD) that was developed by Brian Willis, an associate professor of chemical and biomolecular engineering at the University of Connecticut and the former director of UConn's Chemical Engineering Program.
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It is through atomic layer deposition that scientists believe they can finally fabricate a working rectenna device. In a rectenna device, one of the two interior electrodes must have a sharp tip, similar to the point of a triangle. The secret is getting the tip of that electrode within one or two nanometers of the opposite electrode, something similar to holding the point of a needle to the plane of a wall. Before the advent of ALD, existing lithographic fabrication techniques had been unable to create such a small space within a working electrical diode. Using sophisticated electronic equipment such as electron guns, the closest scientists could get was about 10 times the required separation. Through atomic layer deposition, Willis has shown he is able to precisely coat the tip of the rectenna with layers of individual copper atoms until a gap of about 1.5 nanometers is achieved. The process is self-limiting and stops at 1.5 nanometer separation.
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Impressively, the rectennas, because of their extremely small and fast tunnel diodes, are capable of converting solar radiation in the infrared region through the extremely fast and short wavelengths of visible light something that has never been accomplished before. Silicon solar panels, by comparison, have a single band gap which, loosely speaking, allows the panel to convert electromagnetic radiation efficiently at only one small portion of the solar spectrum. The rectenna devices don't rely on a band gap and may be tuned to harvest light over the whole solar spectrum, creating maximum efficiency.
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« Last Edit: 02/27/2013 09:43 pm by docmordrid »
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Offline Lar

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Re: Nano-rectenna solar arrays
« Reply #1 on: 02/27/2013 09:19 pm »
In layman's terms it's saying what? That you can turn solar power directly into microwaves that go somewhere[1]?

Or just that there is a cheap way of building the rectenna to do the beaming and you still need solar cells to generate electricity first?

Or that this is a way to get broad spectrum input into cells that then put out electricity.

The term "rectenna" is confusing me here.

Thanks for the ref!

1 -where do they go? do you have to steer them somewhere? And if not, do you need mirrors to bring the sunlight in at the right angle?
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Offline Tass

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Re: Nano-rectenna solar arrays
« Reply #2 on: 02/27/2013 09:23 pm »
In layman's terms it's saying what? That you can turn solar power directly into microwaves that go somewhere[1]?

Or just that there is a cheap way of building the rectenna to do the beaming and you still need solar cells to generate electricity first?

Or that this is a way to get broad spectrum input into cells that then put out electricity.

The term "rectenna" is confusing me here.

Thanks for the ref!

1 -where do they go? do you have to steer them somewhere? And if not, do you need mirrors to bring the sunlight in at the right angle?

No it says that they can build a nano-sized rectenna that does the same with visible light as regular rectennas does with microwaves.

In other words it will turn sunlight into electricity at very high efficiency. It has nothing directly to do with microwaves.

Offline kch

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Re: Nano-rectenna solar arrays
« Reply #3 on: 02/27/2013 09:26 pm »

Offline Lar

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Re: Nano-rectenna solar arrays
« Reply #4 on: 02/27/2013 09:38 pm »
Thanks guys. Should have read it twice first. The WP article says 1% was all that was achieved in the initial studies (no info on what the MU project got) so 70% is pretty significant, it's 2-3x better than conventional solar cells...
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
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Offline Solman

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Re: Nano-rectenna solar arrays
« Reply #5 on: 02/28/2013 01:22 am »
 Thanks for posting this. I saw mention of it on sciencedaily and in their article the PI mentions its potential use for thermoelectric conversion as well.
 Might be great for a pebble bed nuclear reactor that would have no moving parts, high efficiency, and could be completely sealed.
 A rectenna array built onto, or better yet of, graphene - perhaps on an insulating diamond substrate (unless graphene can be made to be conductive or insulating by doping or some other technique in which case it could be all graphene) would be quite a thin thin film PV array and a very low mass per unit area one.
 

Offline A_M_Swallow

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Re: Nano-rectenna solar arrays
« Reply #6 on: 02/28/2013 07:32 pm »
Thanks for posting this. I saw mention of it on sciencedaily and in their article the PI mentions its potential use for thermoelectric conversion as well.
 Might be great for a pebble bed nuclear reactor that would have no moving parts, high efficiency, and could be completely sealed.
 A rectenna array built onto, or better yet of, graphene - perhaps on an insulating diamond substrate (unless graphene can be made to be conductive or insulating by doping or some other technique in which case it could be all graphene) would be quite a thin thin film PV array and a very low mass per unit area one.
 

Graphene is a good conductor but can be converted to a semi-conductor.  If it is in the hot then the propellant would have to be something that does not react with carbon.

Offline simonbp

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Re: Nano-rectenna solar arrays
« Reply #7 on: 02/28/2013 07:50 pm »
I imagine the first application might be in infrared sensors, as the current designs are typically very low quantum efficiency, and only need to be produced at very low volumes. Also IR rectenna wouldn't need to be as small, and thus might easier to commercialize.

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