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USA: EV Bus Offers a New Take on Wireless Charging Read more: EV Bus Offers a New Take on Wireless Charging – Popular Mechanics

No matter how efficient electric vehicles get, they still rely on bulky batteries that require extended charging times. Gasoline, which allows drivers to refuel in a matter of minutes and be on their way, has maintained its advantage.

One solution that’s often floated is the wireless power transfer. A recent study at Stanford University proposed an electrified highway that would allow a vehicle to recharge on the run , a nice idea in theory but one that would require an enormous infrastructure upgrade that may not be feasible yet. But researchers at Utah State University say they may have an even better answer: A prototype charging system transfers more power with greater range and efficiency than other systems and would lessen the expense dramatically by placing charging pads at select locations rather than all along a road.

A prototype electric coach called the Aggie Bus, developed by Utah State engineers, will soon shuttle students from one end of the Logan, Utah, campus to the other. Rather than lining the bus’s route with charging pads, the engineers will place a single pad at one of the stops along the 1.6-mile loop to top off the bus batteries. Hunter Wu, the electrical and computer engineering professor at Utah State University who heads the project, says that this setup not only limits the infrastructure cost, but also allows the bus to use an 80 percent smaller battery. The same idea could be applied to common stopping points for passenger vehicles such as intersections and parking spots, he says, to enable quick top-offs for any type of electric vehicle.

“What our solution supplies is this continuous energy buffer,” Wu says. “It can basically maintain the bus to go and go and go and last the whole day.”

Wu made wireless power transfer the subject of his Ph.D. thesis while studying at the University of Auckland in New Zealand. He moved to Utah State in 2010 to put his ideas into practice. After two-and-a-half years of effort, his team unveiled the bus in November, demonstrating what they call the best-ever combination of efficiency, amount of power transferred, and distance transmitted for wireless charging.

The technology that makes it possible to charge a car wirelessly relies on the same induction principle that electric toothbrushes and other consumer devices use. A primary coil wired into the power grid generates a magnetic field. That field interacts across a gap with a secondary coil in the device, which then converts the energy in the magnetic field back into electricity.

To increase the power, efficiency, and distance between charger and battery, Wu and his Utah State team used ferrimagnetic material—manganese zinc—to shape the magnetic field generated by the charging pad into a kind of fountain that can be pointed at the device to be charged. They also tuned the two coils to resonate at the same frequency to drive efficiency of power transfer and generated magnetic fields that oscillate at 20,000 times a second to transfer high levels of power.

Read more: EV Bus Offers a New Take on Wireless Charging – Popular Mechanics



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