Owners of electric vehicles tend to come home in the evenings and plug in their cars – straining the grid because they’re demanding a lot of power at peak times.

Even with plans offering off-peak discounts, most electric car owners still charge their cars at the same time to take advantage of lower prices – also straining the grid, though at different hours.

NYSEG, in collaboration with Eilyan Bitar, associate professor of electrical and computer engineering, is piloting a new approach to coordinate electric vehicle power use by encouraging owners to delay charging times in exchange for lower prices. The project, OptimizEV, will engage 35 participants in Tompkins County for a year to better understand consumer charging preferences, and how these might align with the overall power grid.

“When most people plug their vehicles in, they don’t always need them to be charged immediately, and even though they won’t need them until the following morning, they’re plugged in for the rest of the night,” said Bitar, also a fellow with the Cornell Atkinson Center for Sustainability.

Participants in the pilot will use smart chargers that can communicate to NYSEG their energy usage minute by minute. Electric vehicle owners will indicate how long they plan to leave their cars plugged in, choosing from a menu of options that offers larger discounts the longer they’re willing to delay.

Once customers make their selections, an optimization algorithm – developed by Bitar with Polina Alexeenko, a doctoral student in electrical and computer engineering – will consider their deadlines, their energy usage and the wider demand on the power grid in order to determine the optimal charging pattern for every vehicle being managed.

“That will allow us to both monitor electric-vehicle charging and to transmit control signals that let us adjust the power they’re drawing in real time,” Bitar said. “We’ll reshape the electric vehicle power load patterns to minimize strain on the grid, while still respecting customers’ charging preferences and personal deadlines.”

Power demand for electric vehicles is growing as more consumers use level two chargers, which are faster and more powerful than level one chargers, but can double a household’s peak power demand. The popularity of these chargers, combined with the increased adoption of electric cars, could jeopardize the utility’s ability to deliver power cheaply and reliably.

“Our grid infrastructure has limited capacity,” Bitar said. “Transformers can only accommodate so much demand at any given moment. Exceeding a transformer’s capacity to serve demand can severely reduce its lifetime, requiring more frequent replacements – which is not cheap.”

Experts consider plug-in electric vehicles a step in the right direction for sustainability, but most electric cars are still powered by fossil fuels, if indirectly. Understanding consumers’ willingness to delay their charging patterns, Bitar said, will help relieve pressure on the power grid; it also has long-term implications for integrating renewable energy into the grid.

Renewable sources of energy, such as wind and solar, remain impractical for widespread use in part because they are intermittent, making it difficult to ensure that power will be available when needed. Since electric vehicles are essentially batteries on wheels, they could potentially serve as storage buffers for intermittent energy sources – adding power back to the grid when they’re not being used.

“Such coordination could create a symbiotic relationship, where the flexibility of electric vehicles is used to smooth the variability of renewables, and renewables directly supply clean power to the vehicles,” Bitar said. “The OptimizEV project could help lay the groundwork for more sophisticated experiments that look at the possibility of coordinating electric vehicles not only to mitigate peak demand, but perhaps also to mitigate the intermittency effect of renewables.”

Smart chargers have been installed in the homes of the 35 participants, and preliminary monitoring will continue through the end of the year. The pilot is expected to be completed in late 2020.

OptimizEV is part of NYSEG’s Energy Smart Community Initiative in Tompkins County, and was developed in partnership with Kitu Systems of San Diego, California; Taitem Engineering in Ithaca; and supported in part by the New York State Energy Research and Development Authority.