Wireless Charging of Moving Electric Vehicles Overcomes Major Speed-bump

Stanford University

June, 2017

A team at Stanford University has developed a method to wirelessly deliver electricity to moving objects based on magnetic resonance, a technology that may one day be able to power cars and personal devices.

“In addition to advancing the wireless charging of vehicles and personal devices like cellphones, our new technology may untether robotics in manufacturing, which also are on the move,” said Shanhui Fan, a professor of electrical engineering and senior author of the study. “We still need to significantly increase the amount of electricity being transferred to charge electric cars, but we may not need to push the distance too much more.”

Building on existing technology developed in 2007 at MIT, the team transmitted electricity wirelessly to a moving lightbulb in a small-scale demonstration involving a 1-milliwatt charge.

A major drawback of plug-in electric cars is their limited range and the amount of time required to fully recharge before one can continue driving.

“In theory, one could drive for an unlimited amount of time without having to stop to recharge,” Fan explained. “The hope is that you’ll be able to charge your electric car while you’re driving down the highway. A coil in the bottom of the vehicle could receive electricity from a series of coils connected to an electric current embedded in the road.”

In conventional magnetic resonance coupling, the continuous flow of electricity can only be maintained if the frequency is manually tuned as the object moves. To address that challenge, the team removed the radio-frequency source in the transmitter, and instead replaced it with a voltage amplifier and feedback resistor – a system that automatically determines the correct frequency for different distances without human interaction.

To learn more about this Stanford team’s project, click here.

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