Wireless power transfer

As part of our ongoing studies of electromagnetic systems, we developed a device that transfers electrical power wirelessly over a gap of a greater than 10 cm, without any cords or physical contact between the transmitter and receiver units. Other wireless charging devices exist, but these devices typically use high frequency electromagnetic resonators to achieve high coupling efficiency, and the safety of such radio frequency emitters is questionable since they emit considerable electromagnetic radiation. Rather than using high frequency, the device we developed uses a magnet and a coil coupled together through rotation, and operates at a frequency of about 60 Hz.

This new wireless power transfer device may be useful for charging electric vehicles. It is widely believed that electric vehicles are a necessary component of a sustainable community, specifically to reduce air pollution in urban environments. However, there are currently barriers that limit the widespread adoption of electric vehicles, primarily associated with the need to have easy access to battery charging stations and the method by which this charging process occurs. In order for such vehicles to be practical, it must be possible for them to be easily charged in a variety of locations. The traditional method of charging requires the driver to plug an electrical cord from the outlet to the vehicle, and wireless charging eliminates this requirement. In a proof-of-principle demonstration, we successfully implemented a first prototype in a plug-in hybrid Toyota Prius. The device can be efficient and affordable, and its development may significantly improve the rate of adoption of electric vehicles by making them more attractive to the average driver.