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Vehicle charging goes wireless


Researcher Steven Campbell demonstrates an electric vehicle being wirelessly charged using ORNL technology.

ORNL researchers are dropping the cord in battery charging for electric vehicles and plug-in hybrid models in favor of wireless power transfer (WPT) technology that has proven to be safer, more convenient, and more efficient.

Using a proprietary design created at ORNL’s National Transportation Research Center, John M. Miller, principal investigator with the lab’s Power Electronics Group, and his team have developed a hands-free, magnetized coil system that wirelessly transfers electricity to a vehicle with an onboard battery pack while it’s parked over a floor-embedded charging sensor.

The project’s multi-phase approach includes testing stationary charging of multiple vehicles in real-world situations, such as cars and buses in parking lots and garages, and a longer-term objective of further developing dynamic in-motion charging in which the vehicle’s battery pack is replenished as it is driven over sensors installed along roadways.

Researchers including Chester Coomer worked with various designs to optimize performance of the coil units for wirelessly charging electric vehicles. October 2012. Credit: ORNL
Researchers including Chester Coomer worked with various designs to optimize performance of the coil units.

“This is the ultimate in convenience. Without having to use a cord to plug in the charger to the vehicle, wireless technology takes the charging burden completely off the driver, making it autonomous and safer for people to use,” Miller said.

Test results from the lab show that using ORNL’s wireless coils as a charging source can bring an EV’s battery pack to fully charged with 90% efficiency, which is comparable to the current plug-in method and is the highest charge rate among competing wireless power transfer technologies for EVs.

The ORNL project team’s impressive gains in wireless charging research, coupled with a strong focus on user safety, led to an $8 million award from the US Department of Energy to fund further development and demonstration of the grid-connected, ground-based coil units. With DOE’s support, ORNL plans to install its latest wireless charging coil design at an existing EV charging station as part of the lab’s Sustainable Campus Initiative.  It will be tested with a Toyota Prius parked over an 18- to 20-inch square of charging coils that emits  between 7 and 10 kilowatts of electrical charge.

Miller explained that during the next 3 years, his team will continue development of the static charging functionality of the wireless charging system; take the technology into the production intent phase as it moves toward commercialization; and present the wireless charging system to DOE for further testing, data collection, and validation.

ORNL has focused on WPT for onboard vehicle battery charging since 2008. During the last year, the lab has made significant strides in modified coil technology to effectively and efficiently handle in-motion charging.

In the future, said Miller, moving from stationary to in-motion wireless charging of onboard vehicle batteries may require installation of in-ground direct current cabling along American highways. Setting up EV charging stations, which could resemble and function like toll roads, could be done in tandem with scheduled road construction and repair. EV owners could use the equivalent of an electronic “fast pass” system to pay for wireless charging as they drive over embedded sensors.

The ORNL-led team includes Evatran, General Motors, Toyota, and Clemson University.

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