Technology:
Wireless power
feeding for electric vehicles and plug-in hybrid vehicles is expected to be put
into practical use around 2015. Every company and organization involved in the
development is undergoing a fierce competition, and the development of wireless
power feeding accelerates lately.
Researchers from Saitama University and Technova developed a
technology to the interactive electric transmission between coils on a vehicle
and those on a house. In the experiment, they transmitted electricity of 3 kW
at 50 kHz frequency for a distance of 16 cm between vehicle and house and
achieved about 93% efficiency in both ways. Interactive electricity
transmission allows transmitting electricity stored in a vehicle back to a
house and makes it usable as a power source in a disaster.
Yoichi Hori of the University of Tokyo is studying a technology to bury
multiple transmission coils in the ground to relay electricity for power
feeding of vehicles traveling between the transmission coils. Electromagnetic
waves are liable to change when multiple coils exist between the transmitter
and receiver, and it is hard to feed power exactly to the destination. His research
team successfully developed a method to calculate the optimal current to be
transmitted to the transmission coil using data from vehicles like voltage and
current. With this method, it is possible to distribute power as needed. Showa Aircraft and Nissan are conducting the experiment to drive a carriage on the
road in which coils are buried. They plan to achieve transmission efficiency of
more than 80% in an interval of more than 20 cm between coils. Charging your vehicle
while you are driving it naturally decreases the frequency to visit a station
for charging.
Broadband Wireless Forum participated by wireless carriers will publish a new guideline on
wireless power feeding on May 31. The guideline will discuss the influence of
wireless power feeding on human body, though equipment with an output of
several kilowatts for power feeding to EVs is not subject to the guideline at
the present stage. Influence on human body is very important in addition to
deregulation because electromagnetic wave at a frequency higher than 10 kHz is
subject to the Radio Wave Law.
A demonstration of wireless power feeding
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