Solar power without solar cells: A hidden magnetic effect of light could make it possible

Apr 14, 2011

(PhysOrg.com) -- A dramatic and surprising magnetic effect of light discovered by University of Michigan researchers could lead to solar power without traditional semiconductor-based solar cells.

The researchers found a way to make an “optical battery,” said Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics.

In the process, they overturned a century-old tenet of physics.

“You could stare at the equations of motion all day and you will not see this possibility. We’ve all been taught that this doesn’t happen,” said Rand, an author of a paper on the work published in the Journal of Applied Physics. “It’s a very odd interaction. That’s why it’s been overlooked for more than 100 years.”

Light has electric and magnetic components. Until now, scientists thought the effects of the magnetic field were so weak that they could be ignored. What Rand and his colleagues found is that at the right intensity, when light is traveling through a material that does not conduct electricity, the light field can generate magnetic effects that are 100 million times stronger than previously expected. Under these circumstances, the magnetic effects develop strength equivalent to a strong electric effect.

“This could lead to a new kind of solar cell without semiconductors and without absorption to produce ,” Rand said. “In , the light goes into a material, gets absorbed and creates heat. Here, we expect to have a very low heat load. Instead of the light being absorbed, energy is stored in the magnetic moment. Intense magnetization can be induced by intense light and then it is ultimately capable of providing a capacitive power source.”

What makes this possible is a previously undetected brand of “optical rectification,” says William Fisher, a doctoral student in applied physics. In traditional optical rectification, light’s electric field causes a charge separation, or a pulling apart of the positive and negative charges in a material. This sets up a voltage, similar to that in a battery. This electric effect had previously been detected only in crystalline materials that possessed a certain symmetry.

Rand and Fisher found that under the right circumstances and in other types of materials, the light’s magnetic field can also create optical rectification.

“It turns out that the magnetic field starts curving the electrons into a C-shape and they move forward a little each time,” Fisher said. “That C-shape of charge motion generates both an electric dipole and a magnetic dipole. If we can set up many of these in a row in a long fiber, we can make a huge voltage and by extracting that voltage, we can use it as a power source.”

The light must be shone through a material that does not conduct electricity, such as glass. And it must be focused to an intensity of 10 million watts per square centimeter. Sunlight isn’t this intense on its own, but new materials are being sought that would work at lower intensities, Fisher said.

“In our most recent paper, we show that incoherent light like sunlight is theoretically almost as effective in producing charge separation as laser light is,” Fisher said.

This new technique could make solar power cheaper, the researchers say. They predict that with improved materials they could achieve 10 percent efficiency in converting to useable energy. That’s equivalent to today’s commercial-grade solar cells.

“To manufacture modern solar cells, you have to do extensive processing,” Fisher said. “All we would need are lenses to focus the light and a fiber to guide it. Glass works for both. It’s already made in bulk, and it doesn’t require as much processing. Transparent ceramics might be even better.”

In experiments this summer, the researchers will work on harnessing this power with laser , and then with sunlight.

The paper is titled “Optically-induced charge separation and terahertz emission in unbiased dielectrics.” The university is pursuing patent protection for the intellectual property.

Explore further: The unifying framework of symmetry reveals properties of a broad range of physical systems

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User comments : 19

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Husky
5 / 5 (1) Apr 14, 2011
what you would need is this:

http://www.grc.na...ng1.html

only you would elongate the sharp tip with a fiber tube along wich axis you explot the voltage difference, i wonder if still comes enough lightenergy out the end of the fiber to recycle it back to the front so, you get the dame efficiency as regenerative heatexchangers
Husky
5 / 5 (2) Apr 14, 2011
it should work the other way around also, if one would apply a large voltage along the axis of an optical fiber one can modulate the light
Quantum_Conundrum
1.5 / 5 (6) Apr 14, 2011
This implies a LOT of mirrors and fresnel lenses to get that amount of intensity.

Under ideal conditions for solar collecting, you need to focus around 100m by 100m of mirrors and/or lenses into a single centimeter. Additionally, your "glass" needs to be absolutely perfect and dust free, else you will "shock" the glass and destroy it instantly.

That beam would be something like 100 times stronger than the strongest existing experimental military lasers...
Kingsix
not rated yet Apr 14, 2011
Interesting stuff.
Twin
1.7 / 5 (3) Apr 14, 2011
Could these properties be operative in a cosmic arena?
Perhaps one of the recent "Dark" entities?

An aside:
Not selling myths here, but, wasn't Atlantis supposed to be powered by a crystal? just another facet of interesting stuff.
Kingsix
4.5 / 5 (2) Apr 14, 2011
And some people still think that placing crystals around your home will change the "energy" of it.

I would think that if proved possible to harness it would be viable where ever light reached. However the farther away from a star you would go, the larger the collection would need to be. Although, it may make sense that using the technology and sling-shotting around the sun would make the power gained from a large collector at such close proximity great. Imagine the speed that could be gained!
BeFre
3 / 5 (1) Apr 14, 2011
They are just reversing the electro-optic effect. It is a materials problem.
PinkElephant
4.6 / 5 (8) Apr 14, 2011
you need to focus around 100m by 100m of mirrors and/or lenses into a single centimeter
This is what happens when QC customarily bloviates without having paid sufficient attention to the article in question. Here's the clue this time around:

"new materials are being sought that would work at lower intensities, Fisher said."
hevans1944
not rated yet Apr 15, 2011

So, if the fiber developing the "huge voltage" along its length is non-conductive... how do you complete a circuit to obtain useful current, and therefore power, from this potential?
ibsteve2u
5 / 5 (3) Apr 15, 2011

So, if the fiber developing the "huge voltage" along its length is non-conductive... how do you complete a circuit to obtain useful current, and therefore power, from this potential?
Pretty much the same as usual: You rub a cat on it.
geoffrey_landis
3.3 / 5 (7) Apr 15, 2011
[sunlight] "must be focused to an intensity of 10 million watts per square centimeter" [to make this work as a solar energy converter].

Solar energy at the surface of the Earth is about a 100 MILLIWATTS per square centimeter, so they need concentration ratio of a hundred million to reach that level. The theoretical maximum is 140,000 (due to the sun's solid angle in the sky), and the record for highest solar concentration ever achieved is 84,000. They're suggesting they could convert sunlight into electricity if they could "only" achieve a concentration ratio seven hundred times more than the theoretical maximum?

(reference: _Solar Electricity_ by T. Markvart, page 237. )
Beard
5 / 5 (3) Apr 16, 2011
They're suggesting they could convert sunlight into electricity if they could "only" achieve a concentration ratio seven hundred times more than the theoretical maximum?


They're suggesting that this discovery might enable a new kind of solar power if better materials can be found.
Whodwho
4 / 5 (1) Apr 16, 2011
The answer is simple. They just need to invent the Mr. Fusion w/connected flux capacitor. -Problem solved. Next!

Personally, I'm still waiting to hear about how they are going to utilize the (fairly) recently discovered scotch tape/x-ray producion phenomenon. I'm thinking experiments could involve extra large windows and millions of rolls of scotch tape? Perhaps this could be one for the ISS in their down time...
Whodwho
not rated yet Apr 16, 2011
*production
neiorah
1 / 5 (1) Apr 18, 2011
Hey, anything is possible just give it time. Quit being so negative. It only points out how closed minded you are and that you have no imagination.
wildfire
not rated yet Apr 18, 2011
04/18/11
Well I think a type of manmade {Diamond} can be created and used as a Lens for your solar cell.

Inventor Mr Todd J Tocco
dream-theories.com
jjoensuu
not rated yet Apr 20, 2011
at the right intensity, when light is traveling through a material that does not conduct electricity, the light field can generate magnetic effects that are 100 million times stronger than previously expected


So I guess in space (which does not conduct electricity) some of the light leaving the sun is creating strong magnetic effects as it travels toward us.
MrThermal
not rated yet Apr 22, 2011
Solar thermal production that captures high frequency light down converted into IR and used to run turbines operate at about 25% efficiencies as measured by the reflective surface of the collector, and not by land area. The resulting IR light can be collected and stored for years with little loss. It would seem traditional methods go well beyond the projections made for magnetic production. The downside is the need to focus light which therefore requires a clear sky.
Hugh7
not rated yet May 01, 2011
"wasn't Atlantis supposed to be powered by a crystal?"
I doubt very much you'll be able to trace that claim to any earlier than 1969.