Stanford Researchers Continue Search For Wireless EV Charging

Wireless charging for EVs has long been sought after.

A group at Stanford University is trying to finally achieve that goal.

Right now, wireless charging is a pretty limited technology. A few modern vehicles offer wireless smartphone charging, but the range is limited – the phone must be placed in a certain spot. Wireless charging systems also don’t work with every type of smartphone.

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Charging a smartphone resting in one place is vastly different from charging a moving device – and an electric vehicle is a device that will need lots of charge while moving quickly.

Stanford researchers have been able to send a one milliwatt charge to a moving LED light bulb from up to three feet away. That won’t cut it for a moving car.

“My take on the research: Very exciting, but only relevant to small consumer electronics in the near future,” Ben Lenail, director of business development at the solar energy company Alta Devices, told The Mercury News. “Yes, it could allow users of mobile devices — cell phones, connected health devices, fitness and activity trackers, various wearable gadgets — to cut the cord completely. But electric vehicles need a huge charge.”

SEE ALSO: Ford Unveils Wireless Charging Pilot Program

The Stanford research believe, however, that they can boost the technology to allow more electricity to be transferred while also extending the distance of the chargers and improving efficiency. That would lead to the oft-discussed ideal of being able to charge an EV while driving down a road that had chargers embedded in it.

Charging while driving is something not possible today, but it may be a reality in the future.

“It would address the two key challenges for electric vehicles: limited battery range and the cost of the battery,” Jon Foster of Palo Alto, a tech executive and former chairman of the Palo Alto Utilities Advisory Commission, said to the News. “If electric vehicles could charge while they drive and range became unlimited, that would open the door to much greater use. In addition, it would presumably allow use of much smaller batteries since it would no longer be necessary to have a battery big enough to store sufficient power to drive 80 or 160 or 240 miles.”

Right now, the challenge is this – when an object moves, it interrupts the flow of electricity between the object and charger – meaning that charging stops, since the magnetic coils that both send and receive the charging current need to be on a specific frequency, and that frequency would need to move each time the device moves. The Stanford team is working to replace the radio-frequency source in the transmitter with voltage amplifier that’s commercially available, along with a feedback resistor. This kind of system can figure out the correct frequency for each distance automatically, without human assistance.

“Adding the amplifier allows power to be very efficiently transferred across most of the three-foot range and despite the changing orientation of the receiving coil,” Sid Assawaworrarit, a graduate student, said to the News. “This eliminates the need for automatic and continuous tuning of any aspect of the circuits.”

Of course, there’s the issue of finding all the needed power in the first place. That means embedding chargers in roads, and that’s a process that will consume a lot of time and money, while also inconveniencing drivers as roads are rebuilt.

“‘On-the-go’ charging would make electric vehicles less costly, provide more space for luggage and eliminate ‘range anxiety,’” Foster said. “But a critical question is can it be deployed at a reasonable cost and scale?  Also, would it allow moving vehicles to draw power as fast as they are using it?”

If so, that would be a leap forward for EV use. If not, EVs will remain tethered when it’s time to charge.

Mercury News