True efficient wireless power transfer, not just giant machines in a lab or tiny mats under a cell phone, are what we all dream about. Getting rid of cords that force airport travelers to huddle around power outlets like cavemen around an Arctic fire has been the goal for a hundred years.

There are real-world obstacles to overcome, such as what happens to a resonant wireless power transfer system in the presence of complex electromagnetic environments, like metal plates.

A team of researchers explored the influences at play in this type of situation and describe how efficient wireless power transfer can indeed be achieved in the presence of metal plates. They  discovered that resonance frequency matching, alignment of the magnetic field, and impedance matching are the most important factors for efficient wireless power transfer.

What could that mean? Perhaps wireless power transfer while driving, using magnetic resonance to charge electric vehicles, where corresponding coils attached to the bottom of an electric vehicle would pick up energy as the vehicle passes over the coils embedded in the highway. With this type of dynamic charging, an electric vehicle's driving range could become unlimited and the size of its batteries would be greatly reduced. 

Photos and schematics of the wireless power transfer experiment. The system consists of two high Q resonators and two coupling coils. The coupling coils are placed right next to the source and receiver resonator serving as the input and output port. Both coupling coils are connected to a vector network analyzer. Credit and link: AIP Advances

Wireless power transfer technology may find use in a wide range of applications beyond powering electric vehicles, said Xiaofang Yu, an electrical engineer and postdoctoral fellow at Stanford University, who led the research, like home appliances or medical devices implanted in the human body, and obviously freeing airport travelers from fighting over who gets to use their prongs.

Citation: Xiaofang Yu, Torbjørn Skauli, Bjørn Skauli, Sunil Sandhu, Peter B. Catrysse, and Shanhui Fan, 'Wireless power transfer in the presence of metallic plates: Experimental results', AIP Advances Volume 3 Issue 6