Researchers devise a way to keep plug-in electric vehicles from crashing the grid

Electric utilities have been looking closely at the potential burden widespread adoption of plug-in electric vehicles would put on their aging transmission and distribution infrastructure. Approximately 96,000 plug-in electric cars were bought in the United States in 2013, and by 2020 the International Energy Agency predicts 20 million electric vehicles will be in use worldwide.

Many approaches to reducing the increased load on the grid have been proposed, including centralized systems to elaborate auctions for letting consumers respond to varying rates depending on the load at the time they want to charge their cars. Most of those proposals have drawbacks either in privacy risks or complexity, but a team of engineers from the University of Vermont says it has come up with a novel solution that uses the same principles of packet-switching used by communication and data networks.

 University of Vermont, Sally McCay, 2014
Pooya Rezaei, Paul Hines and Jeff Frolik of the University of Vermont think packets of power can revolutionize the way electric companies deal with the coming tide of plug-in cars. They've applied for a patent on their new invention.

"The key to our approach is to break up the request for power from each car into multiple small chunks — into packets," says Jeff Frolik, a UVM engineer and co-author on the new study.

The research, which they report on in the March issue of IEEE Transactions on Smart Grid, produced a system where electric vehicles would fill themselves up a sip at a time rather than in one long drink. Using smart meters, the new approach would let a car charge for, say, five or ten minutes at a time. And then the car would "get back into the line," Frolik says, and make another request for power. If demand was low, it would continue charging, but if it was high, the car would have to wait.

"The vehicle doesn't care. And, most of the time, as long as people get charged by morning, they won't care either," says UVM's Paul Hines, an expert on power systems and co-author on the study. "By charging cars in this way, it's really easy to let everybody share the capacity that is available on the grid." The team added, though, that a customer with an urgent need for power could signal to the system that it required power regardless of the rates.

The Vermont team’s invention — patent pending — would be decentralized to the level of, say, a neighborhood substation, and the charge “packets” distributed automatically by an algorithm, so overall data about who is using power when would not go back to the utility itself, a feature that could calm some concerns over privacy.

Read the full press release from the University of Vermont, “Will plug-in cars crash the electric grid?” via

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