January 06, 2008
Nanoantenna Photovoltaic Cells Developed

How about incredibly cheap photovoltaics with high conversion efficiency?

Researchers at Idaho National Laboratory, along with partners at Microcontinuum Inc. (Cambridge, MA) and Patrick Pinhero of the University of Missouri, are developing a novel way to collect energy from the sun with a technology that could potentially cost pennies a yard, be imprinted on flexible materials and still draw energy after the sun has set.

The new approach, which garnered two 2007 Nano50 awards, uses a special manufacturing process to stamp tiny square spirals of conducting metal onto a sheet of plastic. Each interlocking spiral "nanoantenna" is as wide as 1/25 the diameter of a human hair.

Because of their size, the nanoantennas absorb energy in the infrared part of the spectrum, just outside the range of what is visible to the eye. The sun radiates a lot of infrared energy, some of which is soaked up by the earth and later released as radiation for hours after sunset. Nanoantennas can take in energy from both sunlight and the earth's heat, with higher efficiency than conventional solar cells.

"I think these antennas really have the potential to replace traditional solar panels," says physicist Steven Novack, who spoke about the technology in November at the National Nano Engineering Conference in Boston.

Plastic is orders of magnitude cheaper than the polysilicon crystal used in the expensive photovoltaics of today.

They think they can achieve a very high efficiency of energy conversion.

Commercial solar panels usually transform less that 20 percent of the usable energy that strikes them into electricity. Each cell is made of silicon and doped with exotic elements to boost its efficiency. "The supply of processed silicon is lagging, and they only get more expensive," Novack says. He hopes solar nanoantennas will be a more efficient and sustainable alternative.

The team estimates individual nanoantennas can absorb close to 80 percent of the available energy.

An order of magnitude drop in the cost of photovoltaics would make energy storage our biggest problem. The sun does not always shine. But when it does cheap photovoltaics would make photovoltaic electricity the cheapest source of power.

Super cheap solar electric would make more industries seasonal. For example, put the cost of electricity below 1 cent per kilowatt-hour in Arizona from the first day of spring through summer and it might make sense to do a full year's Aluminum smelting in 6 months in Arizona. Or maybe do all the smelting in 4 months.

Nitrogen fertilizer production could become seasonal as well. Use cheap electric power to fix hydrogen to nitrogen during the spring before crops get planted. Keep making fertilizer during the summer for use the next year. Other chemical feedstock synthesis could similarly be done when the power is very cheap.

Share |      Randall Parker, 2008 January 06 08:49 PM  Energy Solar


Comments
odograph said at January 7, 2008 2:53 AM:

Comparing efficiencies to cells that use other wavelengths is very apples to oranges isn't it? While these may have higher efficiencies (someday) but they may also be using a less energetic slice of the spectrum. It's the energy of the photons and the range of photons you can convert AND finally the efficiency.

Of course that is for academic bragging rights. All consumers/builders care about is $/watt and lifespan. Cheap and long lasting cells, even if they have low watts per square foot, could still cover every roof. Well, they could if they generate enough power "per roof" to be worth the bother.

Brock said at January 7, 2008 8:04 AM:

Sounds like it's very far from prime-time. I mean, woo-hoo for scientific progress and all (seriously), but it seems to early to compare this with any existing technology. If this comes to market in four years, we can compare it with whatever Nanosolar or whoever has at that time.

Another thought I had was that IR is where the heat is. A solar cell that is transparent to IR (but absorbs visible light and/or higher) may be "better" because it would allow solar-electrical and solar-thermal power to use the same footprint (think of a solar cell that sits on top of a water-heater).

I'd also be very interested to see if they can still print this on plastic once they've solved they conductivity problem.

I imagine that one day (not any time soon) someone will invent the "perfect" solar cell that converts near-100% of the radiation that hits it to usable electricity. It would naturally be black in color and quite cold most of the time, but it would be a good day for mankind.

Dave said at January 7, 2008 8:23 AM:

"Of course that is for academic bragging rights."
"I imagine that one day (not any time soon) someone will invent..."

"The journey of 1,000 miles begins with the first step"... or discovery.

;-)

Julian Morrison said at January 7, 2008 8:49 AM:

The sun does too always shine. You just can't always see it from the Earth's surface.

Nowhere is it written: solar panels have to be on the ground!

Brett Bellmore said at January 7, 2008 8:52 AM:

"Nanoantennas can take in energy from both sunlight and the earth's heat, with higher efficiency than conventional solar cells.
"

I've got thermodynamics issues with any mechanism which claims to extract energy from blackbody radiation that it's at equilibrium with. Can't see getting much energy out of that IR being radiated at night.

wavelength said at January 7, 2008 9:26 AM:

This is not photovoltaic technology in the conventional sense. The current generated is AC in the terahertz frequency range not DC like photovoltaics. Completely different concept. Antennas resonate with EM radiation. There will be some rethinking of the thermodynamics of waste heat. Entropy may be shrinking a bit.

Paul D. said at January 7, 2008 1:27 PM:

There will be some rethinking of the thermodynamics of waste heat. Entropy may be shrinking a bit.

The second law is safe and secure. Getting useful energy out requires rectification, and the rectifier has to be kept cooler than the temperature of the radiation or else it doesn't rectify.

Feynman had a bit on the thermodynamics of diodes in his lecture notes, if I recall correctly.

Rob McMillin said at January 7, 2008 8:18 PM:

I'm always interested in new solar technologies, and right now there seem to be a spate of them using some variation of the "cheap-because-it's-printable" theme. This one also fell into that category; most of the ones I've read about in this area use CIGS (copper-indium-gallium-selenide), but the article itself makes no mention of what the product's base is... until you read the caption for the micrograph, which says that the antennae are gold. I don't care how thin you bang it out, that's just never going to be cheap.

wavelength said at January 7, 2008 9:14 PM:

Rob, the antennas don't have to be gold. They can be made of other metals that are cheaper.

Paul, radiation has frequency and wavelength, but not temperature. If the radiation is absorbed by a material, that material will obviously have a temperature.

BP said at January 8, 2008 2:47 AM:

If the antennas don't have to be gold, why did they use gold from the start? Makes for a bit of a shocker when reading the press literature with "gold" listed as an ingredient for something purporting to be inexpensive in the near future.

Brett Bellmore said at January 8, 2008 8:58 AM:

It's easy to work with, and spares you the need to coat the assembly to prevent your thin film antenna from turning itself into an insulating oxide over time. I expect that's why they used it. Gold in the thicknesses we're talking is no great expense in the context of an experimental device.

Engineer-Poet said at January 9, 2008 8:10 PM:

Quoth wavelength:

radiation has frequency and wavelength, but not temperature.
Says somebody who's obviously not familiar with blackbody spectra.

Rob McMillin said at January 9, 2008 8:37 PM:

wavelength:

Rob, the antennas don't have to be gold. They can be made of other metals that are cheaper.

Then why didn't they?

Engineer-Poet said at January 9, 2008 10:35 PM:

I'm sure that aluminum would do; if it can make sub-micrometer traces on chips, it can serve as microantennas.

Why use gold?  Easy to work with for proof of concept.

Ralph Naidoo said at May 2, 2008 2:41 AM:

How much will it cost to bring this technology to South Africa?

Sara Prentice said at June 11, 2008 8:52 AM:

At Idaho National Laboratory we have produced a short video featuring the nanoantenna technology. You can find it at our INL YouTube site or at the link below.

http://www.youtube.com/watch?v=9fuofnZM5eE

Ramsey Frist said at August 19, 2008 5:06 AM:

As described the proposed device would defy the 2nd Law of thermodynamics. Everything above near absolute zero gives off some IR. They claim to someday be able to extract energy from one body and transfer it to another without without performing any work. Maxwell's demons don't function and never will.

Stanley said at January 24, 2010 7:34 PM:

Maxwell's demon is something that is working without difference of temperature.
But here we have difference of temperature: 6000K on the Sun and +20 on the Earth.
I think there should be difference between amount of energy which nanoantenna
is able to absorb and amount which it will radiate itself at constant temparature.
So why should it be different from any other heat engine?

Stanley said at January 24, 2010 7:35 PM:

Maxwell's demon is something that is working without difference of temperature.
But here we have difference of temperature: 6000K on the Sun and +20 on the Earth.
I think there should be difference between amount of energy which nanoantenna
is able to absorb and amount which it will radiate itself at constant temparature.
So why should it be different from any other heat engine?

Bob said at April 1, 2010 5:30 PM:

Paul,

Your argument assumes it is impossible to build a circuit that does something useful at THZ frequencies
which this radiation is at. If I can build that circuit then I have useful energy from the antenna.

Also, let's not confuse thermodynamic heat engines that work with statistical ensembles of particles to
antenna's where each electron is activated by a photon bringing energy to it. The photons are not in
equilibrium with electrons, they give up their energy to the electrons which is why antenna's work. If
I pointed 100 W/m^2 of microwaves at a microwave antenna you would not worry about the temperature of the
antenna or the rectifier. The same with even longer radio waves. Even optical antenna's have been shown to
work ( on a small scale). But make the EM waves in the IR region and every one suddenly worries about
thermodynamics.


Paul D. said at January 7, 2008 1:27 PM:
There will be some rethinking of the thermodynamics of waste heat. Entropy may be shrinking a bit.

The second law is safe and secure. Getting useful energy out requires rectification, and the rectifier has to be kept cooler than the temperature of the radiation or else it doesn't rectify.

Feynman had a bit on the thermodynamics of diodes in his lecture notes, if I recall correctly.


Stanley said at November 9, 2010 5:43 PM:

``Getting useful energy out requires rectification, and the rectifier has to be kept cooler than the temperature of the radiation or else it doesn't rectify.``

Another posibility to convert heat to electricity is to have constant changes of temperature.This is how pyroelectrics work.
I`m wondering if the same principle would be possible with diodes.


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