Researchers boost wireless power transfer with magnetic field enhancement

July 23, 2015 by David Ricketts
From left to right: performance of wireless power transfer using an MRFE, a metamaterial, and through air alone.

Research from North Carolina State University and Carnegie Mellon University shows that passing wireless power transfer through a magnetic resonance field enhancer (MRFE) – which can be as simple as a copper loop – can boost the transfer efficiency by at least 100 percent as compared to transferring through air alone. MRFE use could potentially boost transfer efficiency by as much as 5,000 percent in some systems, experts say.

Wireless power transfer works by having a transmitter coil generate a ; a receiver coil then draws energy from that magnetic field. One of the major roadblocks for development of marketable technologies is achieving high efficiency.

"Our experimental results show double the efficiency using the MRFE in comparison to air alone," says David Ricketts, an associate professor of electrical and computer engineering at NC State and corresponding author of a paper describing the work.

Enhancing efficiency has been a major goal of many research groups. One of the leading candidates proposed for enhancing efficiency has been a technology called metamaterials. "We performed a comprehensive analysis using computer models of wireless power systems and found that MRFE could ultimately be five times more efficient than use of metamaterials and 50 times more efficient than transmitting through air alone," Ricketts says.

By placing the MRFE between the transmitter and the receiver (without touching either) as an intermediate material, the researchers were able to significantly enhance the magnetic field, increasing its efficiency.

"We realized that any enhancement needs to not only increase the magnetic field the receiver 'sees,' but also not siphon off any of the power being put out by the transmitter," Ricketts says. "The MRFE amplifies the magnetic field while removing very little power from the system."

The researchers conducted an experiment that transmitted power through air alone, through a metamaterial, and through an MRFE made of the same quality material as the metamaterial. The MRFE significantly outperformed both of the others. In addition, the MRFE is less than one-tenth the volume of metamaterial enhancers.

"This could help advance efforts to develop wireless power transfer technologies for use with electric vehicles, in buildings, or in any other application where enhanced efficiency or greater distances are important considerations," Ricketts says.

Explore further: Wireless power transfer enhanced by metamaterials

More information: "Magnetic field enhancement in wireless power using metamaterials magnetic resonant couplers." DOI: 10.1109/LAWP.2015.2452216

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4 / 5 (4) Jul 23, 2015
I don't get it. Isn't the whole point of transmitting power wirelessly that you do NOT have something between sender and receiver?

Sure I can boost the efficiency by putting something in between. In the extreme case I can add many coils creating something known as a "wire" (I know, I know..newfangled stuff) that will give me pretty good efficiency.
1 / 5 (2) Jul 23, 2015
It probably focuses the field.
3.7 / 5 (3) Jul 23, 2015
I guess my medication must be kicking in because I agree with AA ... 'a wire' - lol.

3 / 5 (2) Jul 23, 2015
It probably focuses the field.

It shorts the field - like any antenna. But because it isn't attached to anything it reradiates the field immediately. If I remember my antenna theory lessons then that's pretty straight forward. If you put a few of those in sequence then you have in effect created the inverse of an Helmholtz coil.
3.7 / 5 (3) Jul 23, 2015
Hey, you could put a reflector behind the transmitter element and a director (loop of copper) in front. Haven't I heard of that somewhere before?:- Sure the antenna theory maths is slightly different as its all "near field" The receiver is just an added lossy 'director' element.

Interesting they don't quote how much extra losses they generate by adding all these conductive elements to their array when the receiver is not present, and the transmitter is left in standby for sixteen hours a day. They were so keen to quote favourable statistics: That their system was 5000% better than a bowl full of boiled cabbage (which no-one would use as a transmitter).

Whydening Gyre
1 / 5 (1) Jul 23, 2015
They were so keen to quote favourable statistics: That their system was 5000% better than a bowl full of boiled cabbage (which no-one would use as a transmitter).

Well, if odor was the transmitting medium, it would prob'ly be 5000% worse...
'specially after a few hours of sitting out...

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