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While electric-vehicle sales in the United States are up significantly, and while the U.S. government recently pledged $5 billion in EV infrastructure investment, plus over $1 billion to spur domestic EV battery production, various issues with public charging present significant challenges to widespread adoption.
Challenges around raw materials, range anxiety, the proliferation of EV charging infrastructure, and potential power grid strain have been thoroughly aired, but the nuance around those and other issues begs for a deeper dive.
“As long as there’s low EV penetration and low utilization, we’re okay,” said Dave Mullaney, principal for carbon-free mobility at sustainability nonprofit RMI. “But eventually, when EVs are all over the place and people are charging constantly, we’ll need infrastructure. The question is: How do we deploy solutions in the right sequence that enable people to use EVs at an acceptable cost while also building toward longer-term needs?”
Batteries limit charging speeds
One of those needs is faster charging away from home.
Currently, Levels 1 and 2 chargers—both common for at-home charging, with the latter available at some public charging stations—can take anywhere from all day to eight hours, respectively, to charge an EV enough to achieve a 200-mile range.
So-called Level 3 fast chargers, which deliver DC power directly to EV batteries, can achieve 200 miles of charge in, at best, about 25 minutes.
That is a vast improvement. But experts say 25 minutes presents a hurdle to many consumers, especially those who like to hit the highway for longer journeys.
“The ideal scenario is that [charge times] have to be the same as putting gas in my vehicle,” Mullaney said. “But is that physically possible? With today’s batteries, not really.”
The challenge is the lithium-ion batteries themselves. The faster they charge, the more damage that is done to them. An EV’s battery system knows to throttle down the charging process the closer it gets to a full charge.
Various U.S. Department of Energy labs are researching ways to get around this limitation and drive fast-charge times down to 10 minutes or less.
In a press briefing before a meeting of the American Chemical Society, Eric Dufek, manager of the Idaho National Laboratory’s Energy Storage and Electric Vehicle Department, said that what makes fast charging so hard is regulating how quickly the actual lithium ions move across a battery. When they move too fast, it can cause plating, or the formation of metallic lithium, which can damage batteries.
“We’ve developed different types of charge protocols, as well as advanced electrolytes, that allow us to move those lithium ions back and forth much faster and minimize the degradation that’s associated with fast charging,” Dufek said.
The solution has shown positive results.
“[We] were able to achieve over 90% charge acceptance without plating lithium metal,” Dufek said. “And we were able to actually extend that through at least 600 cycles.”
Grid operators planning upgrades
Concerns over whether the power grid itself, as it currently exists, can handle EV charging are modest.
“If you look at previous evolutions of the grid and the rate at which we expect to see generation growth to support EVs, the new load that would come up is actually fine,” said Andrew Meintz, chief engineer at the National Renewable Energy Laboratory’s (NREL’s) Center for Integrated Mobility Sciences.
NREL studied the power grids in Atlanta and Minneapolis to understand how well they could handle the expected load from EV charging, and while upgrades may be needed eventually, akin to the time period when air conditioners became more prevalent, that’s not the biggest challenge the EV charging infrastructure faces.
“When you get above 20% or 30% adoption, we start to see that transformers need to be replaced at residential locations [and] lines need to be upgraded, but these are typical processes that utilities go through all the time,” Meintz said. “It really comes down to the question of: How quick is the ramp-up, and are we looking far enough ahead to make sure we respond appropriately?”
Chargers have reliability issues
For now, more important than ensuring the grid can handle the demand of EV charging is ensuring that EV chargers work. A Plug In America survey showed that 34% of fast-charger users say broken chargers are a concern.
“The technical challenges are more around integrating payment systems and creating a good user experience,” said Akshay Singh, partner in PwC’s U.S. automotive advisory practice. “And reliability. These days, something like a third of EV chargers are usually down or nonfunctional.”
Not all fast charging is equal. Users of Tesla’s proprietary Supercharger network typically report very high reliability. But non-Tesla fast charging, based largely on the Combined Charging System (CCS) standard, doesn’t fare as well.
Researchers in the San Francisco Bay Area, a hotbed of EV usage, visited 181 public charging stations with 657 CCS chargers and found that only 72.5% were functional. Problems included broken connectors, blank screens, error messages, and payment system failures.
And if the reliability of EV chargers continues to be an issue, it could impact how charging networks develop. “When you’re talking about a much more dispersed network, you’re talking about more assets, many more maintenance problems, and a larger workforce needed,” RMI’s Mullaney said.
Concentrated charging creates higher localized demand on the grid, but that may not be a bad thing.
“Concentration creates lower demand for maintenance,” Mullaney said. “Maybe it’s 20 chargers in a single parking lot, which are easier to handle than 20 chargers that are miles apart. It’s just easier to service the concentrated network.”
Fleet power ‘an issue for the grid’
All that said, the current charging infrastructure likely isn’t yet prepared to power EV fleets—buses and trucks that are often centrally owned, operated, and charged, requiring multiple-megawatt charging capabilities (high-end EV fast chargers are rated up to 120 kW). But charging fleets requires transitionary solutions until demand and grid capacity expand.
“You don’t want to go to your utility and say, ‘I need a 5-MW site here, but I’m not going to use it for the next five or 10 years,’” Meintz said.
NREL and others are researching microgrid solutions, which effectively establish self-sustaining grids where large-scale EV charging is needed but not currently viable. Often, these microgrids are powered by distributed energy sources, such as solar panels of battery energy storage systems. An analogy might be the early World Wide Web, when caching companies would store content closer to users so that their browsing experience would be faster until broadband infrastructure caught up.
Last year, international energy company National Grid and Hitachi Energy published a study of the charging needs for EV fleets.
“Fleet power is an issue for the grid,” said Daniel Simounet, vice president of Hitachi Energy’s transportation sector in the Americas. “For 100 EV buses to charge overnight at 100 kWh each, you need multiple megawatts at the site. And then there are all the trucks that will need to recharge along highways. Megawatt charging standards are coming, but right now, there’s a bottleneck.”
For its part, Hitachi Energy has developed a solution that allows for small-footprint, efficient fleet charging until grid upgrades can be made to support a more robust charging infrastructure.
The U.S. government’s recent pledge of $5 billion in EV infrastructure investment is “a good down payment,” NREL’s Meintz said, “but more needs to be done.”
