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Solar Power without Solar Cells
A dramatic and surprising magneticeffect of light discovered by University of Michigan1researcherscould lead to solar power without traditional semiconductor-based solar cells.
The researchers found a way to make an“optical 　51　,” said Stephen Rand, a professor in thedepartments of Electrical Engineering and Computer Science, Physics and AppliedPhysics.
Light has electric and magnetic 　52　.Until now, scientists thought the effect of the magnetic field were so weakthat they could be 　 53　. What Rand and his colleagues found isthat at the right intensity, when light is traveling through a material thatdoes not 　 54　electricity, the light field cangenerate magnetic effects that are 100 million times stronger than previouslyexpected. Under these circumstances, the magnetic effects develop strength 　55　toa strong electric effect.
“This could lead to a new kind of solarcell without semiconductors and without absorption to produce charge separation,” Rand said. “In solar cells, the 　 56　goesinto a material, gets absorbed and creates heat. Here, we expect to have a verylow heat load2. Instead of the light being absorbed, energy is stored in themagnetic moment3. Intense magnetization can be induced by intense light andthen it is ultimately capable of providing a capacitive power 　 57　Whatmakes this possible is a previously undetected brand of “opticalrectification,” says William Fisher, a doctoral student in applied physics. Intraditional optical rectification, light’s electric field causes a chargeseparation, or a pulling 　58　 of the positive and negative charges ina material. This sets up a voltage, similar to 　59　 in a battery.
Rand and Fisher found that under the rightcircumstances and in right types of materials, the light’s magnetic field canalso create optical rectification. The light must be shone through  a 　 60　thatdoes not conduct electricity, such as glass. And it must be focused to anintensity of 10 million watts per square centimeter8. Sunlight isn’t this 　61　onits own, but new materials are being sought that would work at lowerintensities, Fisher said.
“In our most recent paper, we show thatincoherent light9 like sunlight is theoretically almost 　62　 effectivein producing charge separation as laser light is,” Fisher said.
This new 　63　couldmake solar power cheaper, the researchers say. They predict that with improvedmaterials they could achieve 10 percent efficiency in converting solar power touseable energy. That’s equivalent to today’s commercial-grade solar cells.
“To manufacture modem solar cells, youhave to do 　64　semiconductor processing,” Fisher said.“All we would need are lenses to focus the light and a fiber to guide it. Glassworks for 　65　.It’s already made in bulk, and itdoesn’t require as much processing. Transparent ceramics might be even better.”

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