Can Electric School Buses Pass Tests Posed by Heat Waves?

November 7, 2022

As temperatures start to dip nationwide, student transporters in many states have turned their attention toward implementing wintertime operations. But it was only two months ago that California student transporters were feeling the heat.

A September heat wave prompted the California Independent System Operator — managers of the state’s power grid — to send an alert asking all residents to voluntarily reduce their electricity use during certain hours. The call included foregoing charging electric vehicles. Questions continue about how electric buses will operate in cold weather, but the record September temperatures prompted some to wonder how heat waves and electric vehicles will co-exist going forward.

One benefit of vehicle-to-grid charging is that electrical school buses (ESBs) could become mobile power plants that not only offset peak electricity consumption times for utilities but also serve as emergency generators for school districts and potentially even communities.

But a December 2020 Net Zero America study by Princeton University found that $360 billion in additional investments, beyond what is being funded by the federal Infrastructure Investment and Jobs Act, is needed to upgrade and expand the grid to accommodate an increasingly electric society. And heat waves, like the one that exhausted the state with record temperatures for nearly two weeks straight, are expected to worsen.

Student transporters in California have so far escaped the electrical vehicle mandates that are in place for passenger vehicles as well as commercial trucks and buses, but the trend is for a marked increase in electric school buses (ESBs) over the coming decade.

As of last month, according to the California Air Resources Board, electric school buses account for 2 percent of the state’s 23,800 bus fleet — 1,800 vehicles — either in operation or on order. That’s the largest percentage nationwide.

That is despite CARB leaving school buses out of its Advanced Clean Fleets regulation that requires medium- and heavy-duty commercial fleets achieve zero emissions by 2045. Still, CARB requires the strictest emissions reductions standards nationwide, and the state boasts 1,800 electric school buses as of last month, also the most in the U.S.

Meanwhile, the U.S. Environmental Protection Agency’s Clean School Bus Program Rebate alone last month announced nearly $68.3 million going to 21 California school districts to procure 177 more ESBs.

Cajon Valley Union School District (CVUSD) near San Diego, which transports 1,000 students and has seven electric school buses (ESBs) in its fleet and is currently undertaking the first V2G school bus project on the West Coast. Transportation Director Tysen Brodwolf noted the district’s electric buses weren’t on route during the heat wave and were plugged in to test the V2G functionality during an actual Emergency Load Reduction event.

The district found that the 10 days of 100-degree-plus temperatures had little negative effect on the electric buses, she said.

“We are fortunate to have enough spare vehicles to cover our routes while the ESBs were left in to assist with power to the electric grid,” Brodwolf pointed out. “The goal of the pilot is to add energy back to the grid during times the grid needs it and during times it does not interfere with our routes and charging plans.”

CVUSD can determine if it will participate in a V2G event and “therefore we can control the time in which these vehicles are used, thereby ensuring it will not affect our daily operations,” she added.

If needed to support the grid during times that CVUSD expects its buses to be on route, the district can plan to have drivers take spare vehicles.

“We help with storing energy and stabilizing our local grid using the energy stored in the bus batteries,” said Brodwolf.

Near the state capital of Sacramento, Tim Shannon, director of facilities, planning, efficiency and transportation for the Twin Rivers Unified School District, maintains that ESBs can work anywhere in the U.S., but that “it’s going to be a little more challenging for some.”

“It’s just a matter of looking at those challenges and those barriers and finding solutions,” he continued. “Up north, where it’s really cold, there are going to be challenges there.”

Challenges will start to dissipate as technology improves, he said, adding batteries will get smaller and contain more energy. Additionally, school buses have a unique duty cycle, Shannon pointed out.

“We use them in the morning and not very much during the day. We use them again in the evening for a little while, and then they sit all night,” he commented.

In 2017, Twin Rivers Unified School District became the first school district in the nation to deploy zero-emission electric school buses. The effort was partially funded by a $7.5 million California Climate Investment grant using proceeds from California’s cap-and-trade program. The district’s fleet currently numbers 57 electric buses, which will increase to 82 in less than two years, noted Shannon.

In addressing alerts from the California Independent System Operator, Shannon said his district is looking to install “stationary batteries and solar throughout our entire district of 52 schools and adding chargers to each of those so that there will be microgrids all around.”

Time is the biggest barrier to challenges, he added.

“It takes time to build an infrastructure,” Shannon shared. “You’re looking at the planning portion of it, a building, your stakeholder team and working with the power company, working with facilities within the organization, and then getting buy-in from the board.

“After that, there’s probably another nine months of infrastructure building, if you can get all of the pieces. Our upgraded infrastructure has taken us an additional seven months because we couldn’t get switch gear and transformers.”

Shannon pointed out that the district saves 80 percent in fuel costs by operating electric school buses. And with California’s Low Carbon Fuel Standard credits, the district receives more money than it pays for fueling the remaining 100 buses powered by renewable diesel.

“We pay for fuel, but it’s offset with the savings and the monies we get, so it’s about 60 to 70 percent savings in maintenance,” he observed. “It’s much easier to do all of your periodic maintenance that you have to do every 45 days. There are far fewer parts because a combustion engine has over 2,000 moving parts and an electric engine has less than 26.”

Modesto City Schools in California’s San Joaquin Valley, meanwhile, was successful in the first round of the U.S. Environmental Protection Agency (EPA) rebate lottery to receive eight electric school buses. Gilbert Rosas, the district’s director of sustainability and adaptation, noted that a heat wave is unlikely to adversely affect EV school buses.

“Luckily, some of our charging can happen mid-morning, in between morning and afternoon runs,” said Rosas. “The typical state-wide peak load time is 5 p.m. to 9 p.m. We are usually finished with our routes and back to the yard before 5 p.m. We can also use our smart charging to charge overnight or midnight to 5 a.m., if necessary. We get our power from Modesto Irrigation District and Turlock Irrigation District and both utility companies rarely have outages that last very long.”

**Modesto City Schools electric buses.**

Arizona’s Perspective

Meanwhile, Arizona school districts can see average temperatures of 95 degrees at the start of school as well as in the springtime. Summer school regularly sees temperatures that exceed 105 degrees.

Alex Mada, transportation director for the Cartwright School District #83 in Phoenix, noted that Arizona has yet to mandate when to charge ESBs. But if the district was ever required to do so – it obtained its first during the summer of 2021 and plans to have as many as 10 over the next five years – it would create a problem that would be solved by including a timer function on the EV charger.

“EV chargers are not all created equal, so we would need to make sure our chargers have this function in order to set charge times as mandated by our power company. Anyone who buys a charger should make sure to include this function,” Mada said. “At this time, we would plan to adjust to the times set by the power company. We would have to manually set the charger as needed to ensure the charger is used to its full capacity. If this becomes a norm, we will move forward with upgrading to the required charger as necessary.”

In terms of whether V2G would help – or not help – in a heat wave situation, Rosas notes V2G would help by allowing a switch over to solar or battery storage options provided there were automatic transfer switches and bi-directional chargers onsite.

Twin Rivers Unified School District is in the process of implementing a V2G infrastructure program with 26 bidirectional charging units to be used for load balancing with the local utility on hot days.

“Some people say you’ve got to have V2G in order to make the electric school bus work,” Shannon added. “We’re working out a scenario for how payment is going to work – what’s advantageous to both parties. We also don’t know what the ill effects of V2G is going to have on the batteries themselves. There could be unintended consequences.”

Mada noted that V2G charging technology is beneficial.

“It is possible for batteries to overheat or software to miss and continue charging when batteries are full,” he said. “This would help with making sure batteries are not overcharging.”

In school districts that have electric school buses, transportation directors such as Shannon advise other districts to make sure they’re planning for the future as they adopt EV technology.

“I thought having enough room for 24 chargers was going to be enough,” he said, adding more chargers had to be installed for V2G. “Ensure you put enough pipe, wire and capacity in because once you get the electric school bus and start running the data and see the advantages to it and the positive effects it has on kids, you’re going to want to switch.”

Ryan Gray contributed to this report.