Capturing Solar Power With Antennae

necro81 writes "Researchers at the University of Missouri and the Idaho National Laboratory have demonstrated a new method of capturing solar power. Rather than using semiconductors to capture photons of sunlight, they fabricated small coiled antennae (several um square) that resonate with the wave nature of light. The antennae are tuned towards midrange infrared light (5-10 um), which is abundant on our cozy-warm Earth — even at night. They also demonstrated a way to imprint these coils on a substrate, like how CDs or vinyl records are produced, but could be scaled to roll-to-roll mass production. The usual caveat applies: it may be 5-10 years until this could hit the market."

Comments

And 5-10 years from now...

[elrous0]

It will still be 5-10 years away.

Antennas

[LearnToSpell]

Antennae are for bugs.

Most important point not in summary

[GameboyRMH]

The summary fails to mention the most important advancement here: 90%+ efficiency. That's a game-changer for solar power.

Re:Most important point not in summary

[joe_frisch]

What are they using to rectify the signal to convert to DC? The antenna is neat - but not at all surprising, its size should just scale with wavelength. You could make a 125nm long antenna that would resonate with visible light (well withing the resolution of existing lithography). The problem is how to convert the 100THz signal you get to a DC signal. You need a fantastically fast diode.

If they have managed this, that would be an impressive achievement. The fastest diodes I am aware of are around 1THz, but its well outside my field and there might be something faster out there

BTW: the efficiency isn't all the impressive. For single frequency light, conventional solar cells can be quite efficient (~80%???), but they don't do will with broad thermal light (like sunlight). The photons that are less than a band-gap don't do anything, and the ones above a bandgap waste any excess energy.

Re:Most important point not in summary

[Brett Buck]

I think you see the problem - I *am* in a related field and I certainly don't know of any practical or efficient way to rectify it. I can think of absurdly inefficient ways, but we already have a bunch of those.

Re:Most important point not in summary

[lupine]

From TFA:
The individual nantennas can absorb close to 90 percent of the available in-band energy.

So the total system efficiency depends on how wide that band is in relation to total solar energy available and whether nantennas can be stacked and designed to capture energy over a range of bands.

Re:Most important point not in summary

[skids]

Such a system would be yet another layer in the panel to deal with a specific frequency range. Perhaps several layers with different wavelengths in each. It's journalists that make the mistake of promoting this as a whole solar panel.

That said, the rectification issue is a deal killer. Not only are we talking THz, but IIRC from the last media go-round with this technology, voltages way below practical diode thresholds.

subluxations LOL

[fyngyrz]

Phrenologically speaking, your entire post is really lumpy. From a cooking standpoint, your pot is cracked. And scientifically speaking... well, why bring science into it now?

Re:How hard can it be ...

[chemicaldave]

The newsworthiness is that instead of only 250 million nantennas on one small square like in that INL page, these guys replicated a design onto an "8 inch round silicon wafer" with 10 billion antenna elements. And they did it with high detail and little loss between the "master print" and the copy.

Unobtainum diodes

[Animats]

What are they using to rectify the signal to convert to DC?

Unobtainum diodes. They don't actually know how to do that.

Terahertz diodes do exist. Low-cost, high-efficiency, integrated terahertz diodes, no. But as work proceeds on terahertz electronics, someone may solve that problem. Each nanoantenna needs its own nanodiode, so the diodes have to be fabricated on the substrate with the antenna, which complicates the fab problem. The enthusiasm about roll-to-roll low cost fabrication in the article is premature. We'll probably see this working first on a wafer, and it may not be cheap.

Even if it's expensive, there's an initial market for satellite power panels. The performance improvement would be worth it.

Re:Unobtainum diodes

[joe_frisch]

I've bought some 300Ghz diodes from Virginia Diodes. Worked great, but $7K each as I remember......

Here they need more like 100 THz. Might be possible with some sort of nonlinear optical material, but the fields are probably much too low.

Even if this whole scheme does work, its not clear it is any better than a conventional solar cell - they are quite efficient for narrow-band radiation right above their bandgap. You can stack different band-gap solar cells to get a quite efficient stack, but it doesn't make economic sense - sunlight is free, its the solar cells that cost money......

Re:Ressonance good for communication not power

[demonbug]

MASERs and rectenna already operate using this same principle, and similarly operate at 85% or better efficiency. Since they operate in the tens of GHz range, there are readily available electronics available to handle them.

Cartman had one of those, right?

Bug antennae

[Ungrounded Lightning]

Antennae are for bugs.

Funny you should mention that.

Apparently insects have similar antenna systems in their antennae to detect pheromones by their infrared signature. Also electret excitation structures attached other antenna structures to emit tuned infrared when pumped by grooming.

Here's one reference.