Researchers at the University of Vermont have created a new method to handle the strain new electric vehicles will place on the nation’s electric grid.
Plug-in electric vehicles, while still a small portion of the automotive market, continue to grow rapidly in popularity in part due to decreasing manufacturing costs and wider availability. In 2013, sales of full electric and plug-in vehicles such as the as the Chevrolet Volt, Tesla Model S or Nissan Leaf increased 84 percent from 2012; by 2020, 20 million electric vehicles are predicted to be on roads around the world.
This growing fleet of vehicles that must be charged in order to function, however, is expected to place a large amount of new strain on the nation’s aging electric distribution systems. In particular, the new generation of car chargers, so-called “Level 2 PEV chargers,” are likely to be the biggest power load in a home, effectively doubling the demand for electricity.
“The load provided by an electric vehicle and the load provided by a house are basically equivalent,” Jeff Frolik, a UVM engineer and co-author on the new study, said. “If someone gets an electric vehicle it’s like adding another house to that neighborhood.”
The strain will be particularly heavy at times of peak demand, such as in the early evening following the nine-to-five work shift.
Now, researchers from the University of Vermont have created a method to manage these simultaneous demands for power they say will prevent the grid from crashing or utilities from needing to raise electric rates. The research is published in the journal IEEE Transactions on Smart Grid.
“The key to our approach is to break up the request for power from each car into multiple small chunks—into packets [similar to how radio and internet communications are distributed],” Frolik said.
The patent-pending technique employs smart meters— household electric meters that transmit information between a house and the utility—to manage a vehicle’s charging time, says Frolik, allowing it to charge for several minutes at a time before getting “back in line” and making another request for power. If demand was low, the vehicle could continue charging; if it was high, the vehicle would have to wait. Collectively, the information received from smart meters would help prevent the grid from being overloaded.
“The vehicle doesn’t care. And, most of the time, as long as people get charged by morning, they won’t care either,” Paul Hines, an expert on power systems and co-author on the study, said. “By charging cars in this way, it’s really easy to let everybody share the capacity that is available on the grid.”
The new technology also includes a provision to protect a vehicle owners’ privacy, the researchers say.
“Our solution is decentralized,” Pooya Rezaei, a doctoral student working with Hines and the lead author on the new paper, explains. “The utility doesn’t know who is charging.”
Instead, the power would be distributed randomly by a computer algorithm known as an “automaton.” According to the Vermont team, “the automaton is driven by rising and falling probabilities, which means everyone would eventually get a turn — but the utility wouldn’t know, or need to know, a person’s driving patterns or what house was receiving power when.”
Drivers will be also able to choose between non-urgent and urgent charging modes when required. In the urgent mode, the vehicle requests power regardless of the price of electricity, and the system in return gives the vehicle the best odds of getting to the front of the line.
Hines believes the new technique is a step above other suggested methods
to manage power demand.
“Some of the other systems are way too complicated,” he said. “In a big city, a utility doesn’t want to be managing millions of tiny [online] auctions. Ours is a much simpler system that gets the job done without overloading the grid and gets people what they want the vast majority of the time.”
