Wireless system could allow EVs to recharge while on the move
Stanford University researchers have designed a charging system that could allow electric vehicles to recharge while they're on the road.
The novel system utilises magnetic fields to wirelessly transmit large electric currents between metal coils placed several feet apart. The researchers believe the technology has the potential to dramatically increase the driving range of electric vehicles and eventually transform motorway travel.
"Our vision is that you'll be able to drive onto any highway and charge your car," said Shanhui Fan, an associate professor of electrical engineering. "Large scale deployment would involve revamping the entire highway system and could even have applications beyond transportation. What makes this concept exciting is that you could potentially drive for an unlimited amount of time without having to recharge."
The wireless power transfer is based on a technology called magnetic resonance coupling, whereby two copper coils are tuned to resonate at the same natural frequency.
The coils are placed a few feet apart and one is connected to an electric current, which generates a magnetic field that causes the second coil to resonate. This magnetic resonance results in the invisible transfer of electric energy through the air from the first coil to the receiving coil.
"Wireless power transfer will only occur if the two resonators are in tune," Fan noted. "Objects tuned at different frequencies will not be affected."
To determine the most efficient way to transmit power, the Stanford researchers created computer models of systems with metal plates added to the basic coil design.
Using mathematical simulations, they found that a coil bent at a 90° angle and attached to a metal plate could transfer 10kilowatts of electrical energy to an identical coil 6.5ft away.
"That's fast enough to maintain a constant speed," Fan explained. "To actually charge the car battery would require arrays of coils embedded in the road. This wireless transfer scheme has an efficiency of 97%."
Fan and his colleagues recently filed a patent application for their wireless system. The next step is to test it in the laboratory and eventually try it out in real driving conditions.
The researchers also want to make sure that the system won't affect drivers, passengers or the dozens of microcomputers that control steering, navigation, air conditioning and other vehicle operations.
"We have the opportunity to rethink how electric power is delivered to our cars, homes and work," Fan concluded. "We're used to thinking about power delivery in terms of wires and plugging things into the wall. Imagine that instead of wires and plugs, you could transfer power through a vacuum. Our work is a step in that direction."
