‘Batteries on wheels’: EV buses could help decarbonize more than just transit

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Municipalities looking to decarbonize both their transportation fleets and their grid have a secret weapon: school buses.

EV buses can help municipalities reduce emissions from transportation—the biggest source of CO2 emissions in the US—but they also present an opportunity to bolster the electrical grid through bidirectional charging programs that can turn buses into batteries. As a result, efforts to make use of electric buses as both transportation and battery storage are underway across the US—particularly in California, a leader in vehicle-to-grid (V2G) experiments.

“If it’s a diesel bus, the time that it’s sitting there between routes, it’s just rotting, and leaking fluids and getting tired. Whereas, the electric bus can do other things in all of that time,” Sean Leach, director of technology and platform management at Highland Electric Fleets, which supplies and manages electric buses for schools, told us. “We have a very large battery sitting down there basically, because these are just batteries on wheels,” he added.

Magic school bus

Some of the first V2G applications for electric buses are happening in the schoolyard. That’s because the schedule of school-bus trips throughout the year makes them well-suited to double as distributed energy resources, experts told us.

“School buses are particularly high-value. They’re very important for communities and for students to cut pollution and tailpipe emissions. And they’re just a really good opportunity for V2G,” Zach Woogen, policy manager at the nonprofit Vehicle-Grid Integration Council (VGIC), told us.

Demand for electric school buses is currently so “overwhelming” that the EPA nearly doubled state funding for the vehicles this year.

The Antelope Valley Transit Authority in northern Los Angeles County became the first zero-emissions transit agency in North America earlier this year, and the increasing federal support for electric buses could help other school districts and cities follow suit.

As these fleets electrify, some utilities are thinking ahead to vehicle-to-grid capabilities, Andrew Blejde, co-founder of fleet management company Synop, told Emerging Tech Brew.

“Even if a school bus has 100 kilowatt hours of battery capacity, I mean, 100 school buses will make 10 megawatts of power,” Vic Shao, president at bp pulse fleet (formerly Amply Power), told us. “It doesn’t take a lot of school buses to all of a sudden have a pretty significant storage mechanism in place to support the grid in times of need.”

In Beverly, Massachusetts, electric school buses provided 10 MWh of power back to the grid on 30 different occasions last summer, according to Highland Electric. For context, 10 MWh is more than enough energy to power a home in Massachusetts for an entire year, per SEIA data.

The usefulness of these buses in a city setting depends largely on location, Woogen said.

“A lot of the value behind distributed energy resources comes down to where they are sited, and a lot of urban areas tend to be congested areas of the grid,” he said. “Having an understanding of where those congested areas are, and also ensuring that the pricing or the program reflects the value that’s provided, is going to be critical to, for example, parking a bidirectional bus in a congested area and discharging it.”

Montgomery County, Maryland, located outside of Washington, DC, is the most populous county in the state. Highland Electric has worked on five bus-charging depots there, some of which could support dense areas in the future, Leach said, although they are not yet connected for V2G.

“We really have to be smart about how the vehicles are filled up. But on the flip side of the token, if we’re able to do V2G there as well, we can help that grid relieve some of that constraint. So in those peak times, the buses might not need to be charging. Discharge them to help alleviate that constrained grid,” Leach said.

Con Edison and National Express ran a three-year V2G pilot project in White Plains, New York, and found that the electric school buses could provide benefits to their service area. This could eventually mean more grid support from buses across the state and in New York City, which passed a law last October requiring all school buses to be electric by 2035.

Earlier this year, New York State committed to replacing 100% of the state’s nearly 50,000 diesel school buses with electric ones by 2035.

Beyond the schoolyard

Municipal transit buses are also electrifying, but working around public transportation schedules could make V2G opportunities more challenging, experts told us.

“The duty cycle of transit buses is pretty intense most of the time. And I think in most of the utilities that we have experience with and the programs that we’re aware of, the peaks tend to fall during times when the buses are probably going to be out shuttling people around,” Leach said.

The way utilities alert asset owners about discharging times can vary by region. Some give 24 hours’ notice about periods when they’ll need to pull energy from batteries, but others may have a much narrower window, notifying fleet operators just a few hours beforehand, Leach said.

These shorter alert times “tend to be more lucrative,” but they can also make the charging equation more complex, he said. And that extra complexity is more easily handled by school bus fleets, which sit dormant for long, predictable periods, than it is for busier city buses.

“We’re leaning really heavily on machine learning and AI, because at a very early point, we realized a human really can’t run a large EV fleet at scale and manage every single thing, especially when you start thinking about signals from utilities,” he said.

But eventually, with enough of these insights and processing power to sort through them, even these trickier assets could benefit cities.

“If you distribute it amongst the transit buses that happen to be parked at that time…and then you also spread it across the rest of the fleet, like vans, trucks—the smaller batteries…That’s a ton of energy that you can grab little bits and pieces from all sorts of vehicles across the county or town, and have them help when they need to,” Leach said.

“I definitely think there’s an opportunity there,” he added.