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Τρίτη, 20 Μαρτίου 2012

New magnetic effect of light an alternative source of solar energy

  

http://www.electronicsnews.com.au

UNIVERSITY of Michigan researchers have found a previously hidden magnetic effect of light which could lead to an alternative form of solar power.

The researchers at the university say it could be possible to generate solar power without using traditional semiconductor-based solar cells.

Light has electric and magnetic components. Until now, scientists thought the effects of the magnetic field were so weak that they could be ignored. 

The team led by Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics, found that at the right intensity, when light is travelling 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.

A new kind of solar cell utilising this effect would not require absorption of light to produce energy. Instead, energy can be derived from the intensive magnetisation induced by the light.

To manufacture modern solar cells, extensive semiconductor processing is required. With this new type of generation, all that is required would be lenses to focus the light and a fibre to guide it, both of which can be made efficiently out of glass.

According to the researchers, the core of the discovery is a new type of  “optical rectification”. 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 greats a voltage.

This electric effect had previously been detected only in crystalline materials that possessed a certain symmetry, but the researchers found that under the right circumstances and in other types of materials, the light’s magnetic field can also create optical rectification.

Of course, hurdles remain. While the effect works by shining light through a non-conductor like glass, it must be focused to an intensity of 10 million watts per square cm. Sunlight does not have this intensity, so researchers are working with lasers for now.

However, they are looking for new materials that would work at lower intensities, allowing non-directional sunlight to work in a similar manner. 

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