A Boost for Wireless Power Transfer

Wednesday, March 14, 2012 @ 01:03 PM gHale

Wireless usage continues to grow and the idea of wireless energy transfer is sparking renewed interest in the ability to power up without plugging in.

There is now new technology in development that can enhance the efficiency of wireless power transfer systems by incorporating a lens made from a new class of artificial materials.

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When a changing electric current flows through a wire it generates a magnetic field, which in turn can induce a voltage across a physically separate second wire. Called inductive coupling, this electromagnetic phenomenon already sees use commercially to recharge devices such as cordless electric toothbrushes and mobile phones, as well as in more developed experimental systems that can wirelessly power a light bulb across a distance of more than two meters.

Finding a way to increase the inductive coupling in such systems could improve the power transfer efficiency. A research team from Duke University in Durham, NC, and the Mitsubishi Electric Research Laboratories in Cambridge, MA, thinks a superlens, which can only consist of artificially-structured metamaterials, might be able to do the trick.

A superlens has a property call negative permeability. This means it can refocus a magnetic field from a source on one side of the lens to a receiving device on the other side. By running numerical calculations, the team determined the addition of a superlens should increase system performance, even when you lose a fraction of the energy by passing through the lens.

When the researchers first began studying how a superlens might affect wireless energy transfer, they focused on lenses made from metamaterials that exhibited uniform properties in all directions.

In their new study, the team also considered materials with magnetic anisotropy, meaning the magnetic properties are directionally dependent. Their results suggest strong magnetic anisotropy of the superlens can offer further improvements to the system, such as reduction of the lens thickness and width.

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