US researchers say they are a step closer to enabling electric cars to recharge themselves as they drive.
The technology uses magnetism to transmit electricity wirelessly and could be used to power electric cars as they move along the road, as well as robots on factory floors and drones hovering over rooftops.
Although wireless charging already exists for smartphones, it only works if the phone is sitting still on the charging pad, Stanford University said. For cars, that would be just as inconvenient as the current practice of plugging them in for an hour or two at charging stations.
Three years ago, Stanford electrical engineer Shanhui Fan and Sid Assawaworrarit, a graduate student in his lab, built the first system that could wirelessly recharge objects in motion. They did this by incorporating an amplifier and feedback resistor that allowed the system to automatically adjust its operating frequency as the distance between the charger and the moving object changed.
At first, the system was too inefficient to be useful outside the lab. The amplifier used so much electricity internally to produce the required amplification effect that the system only transmitted 10% of the power.
However, in a paper published in Nature Electronics, the two engineers have demonstrated how to boost the system’s wireless-transmission efficiency to 92%.
“This is a significant step toward a practical and efficient system for wirelessly recharging automobiles and robots, even when they are moving high speeds,” Fan said. “We would have to scale up the power to recharge a moving car, but I don’t think that’s a serious roadblock. For recharging robots, we’re already within the range of practical usefulness.”
How long will it be before wireless chargers become embedded in our roads?
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Tags: electric cars