A research group at the University of Tokyo prototyped a "multi-hop" wireless power transmission system and demonstrated it at Techno-Frontier 2014.
A multi-hop wireless power transmission system supplies electricity from the resonator connected to a power source to a device far away from the power source by using multiple resonators to relay electricity. It is not necessary to provide power to the relaying resonators.
The multi-hop system enables to extend the range of power transmission from a power source to a target. The group aims to embed relaying resonators in floors and walls to supply electricity to anywhere.
"Thus far, we have submitted papers on the methods to realize efficient multi-hop wireless power transmission systems," said Yoshihiro Kawahara, associate professor at the Department of Information and Communication Engineering, the University of Tokyo. "But this is the first time that we have made a functional prototype. It was completed right before the opening of the exhibition."
At the exhibition, nine resonators were deployed, and one of them was connected to a power source. Electricity was transmitted from the power source to an LED lamp, electric fan, etc via multiple resonators. It is possible to choose which relaying resonators will be used and which one will be the final destination of electricity with software.
With multi-hop wireless power transmission systems, the frequency that realizes the highest efficiency is dispersed depending on the number of resonators. Also, the frequency changes depending on the distance between resonators.
To solve this problem, the research group developed a method to calculate a distance (between resonators) that enables to efficiently supply electricity with a single frequency regardless of the number of hops. In the demonstration, a peak frequency of 13.56MHz was used.