Electric vehicles (EVs) are key to decarbonizing transportation. But if everyone charges their EV when they get home from work in the evening, it will put an enormous strain on the electrical grid.
Meanwhile, solar power is key to decarbonizing the electrical grid. But while solar power generation is greatest at midday, electricity demand tends to be greatest in the early evening. Because of this mismatch, a big ramp-up of solar could contribute to all manner of inefficiencies; for example, a lot of solar electricity generation could be “wasted” without the construction of costly battery banks.
But these complex problems could have a simple, elegant solution, according to new research. Carefully strategizing about where to put EV charging stations for people to use when out and about during the day, combined with encouraging people to delay EV charging when they are home for the night, could virtually eliminate excess strain on the grid even with lots of EVs on the road.
Researchers modeled electricity supply and demand on an hour-by-hour basis for two cities—New York, New York and Dallas, Texas—in a scenario with widespread rollout of both EVs and solar power. They based their analysis of electricity demand for charging EVs on real-life data from the two cities regarding when and for how long vehicles are in use versus parked in different locations.
If people make a habit of charging their cars while parked at work during the day, this would use up midday solar generation that might otherwise go to waste, the researchers report in the journal Cell Reports Physical Sciences. In other words, excess solar energy generated during the middle of the day can be stored in car batteries rather than in purpose-built battery banks.
At-work charging will also reduce the surge in electricity demand for car charging during peak hours of the early evening. Another strategy to reduce this early-evening demand surge, the researchers propose, is for people to set at-home chargers to finish charging shortly before they plan to leave home the next morning, rather than juicing the car up right away. (At-home chargers means chargers anywhere people park when they are at home—on the street, in apartment building garages, and so on—not just dedicated chargers in the garages of single-family homes.)
The first of these strategies works because the behavior of many drivers is broadly similar: once at work, people tend to leave their cars parked for hours at a time. The second strategy works because the behavior of individual drivers varies: one person leaves for work at 6 a.m. and another at 8 a.m., for example.
Together, the two strategies can all but eliminate the extra early-evening surge in electricity demand from widespread adoption of EVs, the researchers calculated.
The findings can give policymakers hints about where to prioritize or incentivize adding EV infrastructure, the researchers say—for example, widespread availability of free or low-cost charging at workplaces would encourage people to prioritize at-work charging.
A key advantage of the strategies the researchers identified is that they don’t require people to change their driving behavior. Nor do they rely on expensive and unproven technologies such as vehicles equipped to deliver power to the grid or real-time communication and centralized control of chargers.
“These strategies may require only small design and regulatory changes, which may make them more likely to be adopted, and they can be effective even if introduced piecemeal at a local level and without full coordination,” the researchers write.
In fact, the researchers found that workplace charging with lower-cost, slower level 1 chargers is just about as good at meeting drivers’ needs as level 2 chargers would be, while placing less strain on the grid from a surge in fast charging demand when people get to work in the morning.
However, maximizing the benefits of these strategies requires a more coordinated rollout of EVs and solar power. Right now, people aren’t switching to EVs fast enough for their charging needs to make use of all the solar power that’s being installed. These findings “highlight the importance of coordinating decarbonization of electricity and transportation policies,” the researchers write. “Many transportation decarbonization policies lag behind those for electricity sectors, for example among US states.”
Source: Needell Z. et al. “Strategies for beneficial electric vehicle charging to reduce peak electricity demand and store solar energy.” Cell Reports Physical Science 2023.
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