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

Antennas

[LearnToSpell]

Antennae are for bugs.

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: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......