Paper Shares Successes, Lessons Learned from Early Electric School Bus Adopters

October 14, 2019

File photo of the eLion from The Lion Electric Company.

A new report provides nearly a dozen recommendations that it claims would reduce technological and economic hurdles for cities, states and school districts when adopting electric buses.

The new paper was published on Thursday by the nonprofit U.S. PIRG Education Fund, which identifies itself as an independent and nonpartisan consumer and public interest advocate. The report examined the initial experiences of six early adopters of electric buses—four transit agencies and two school districts—and focused on the successes and challenges of implementing the technology into their fleets.

The report’s recommendations called for collaborative partnerships with electric utilities beginning at the earliest stages of a new project, plus contracts with bus manufacturers to guarantee warranty protection.

It also stressed that agencies should be realistic about the capabilities of electric buses and their charging infrastructure. That evaluation is based on their respective routes and operation conditions. It shows they should invest in as large of an EV fleet as possible.

“Ensure the availability of additional electrical capacity and build the infrastructure to be able to add more chargers, including on-route charging infrastructure,” the report states. “The larger the fleet, the greater its visibility, and the greater the opportunity to demonstrate the vehicles’ functionality and desirability.”

Before going to bid, U.S. PIRG advised districts to have electric buses from different vendors “shadow” diesel bus routes to record specific requirements the EVs must meet. Researchers also advised fleet operators to acquire as much data as possible from agencies that are already using electric buses and include the total lifecycle environmental and health benefits.

One of the districts profiled, Twin Rivers Unified in Sacramento, California, currently has the largest number of electric school buses in one operation in the U.S.

In July, Director of Transportation Tim Shannon shared at the STN EXPO Reno that his 25 EVs have resulted in up to an 80 percent reduction in maintenance costs. He said that is because there is no oil to change, no fuel and oil filters to replace, and less wear on brake components.

In addition, U.S. PIRG said the district has realized similar savings on fuel costs, which the study largely attributed to favorable utility rates.

“The district reports a total savings of $15,000 per year on energy and maintenance costs, and believes its experience proves that electric school buses can be a reliable and cost-effective alternative to diesel buses,” the report summarized.

Shannon clarified for School Transportation News that the $15,000 amount cited by U.S. PIRG was per vehicle per month. He said his district also saves 80 percent per month on fuel by plugging in 16 buses on a revolving basis (the district as of this report had only 16 electric chargers) for total fuel savings of $76,800 a year. The average amount saved per bus is $400 a month.

The Twin Rivers electric buses—which currently number 12 LionC (formerly known as the eLion) buses from the Lion Electric Company, five Blue Bird Vision Electric buses, and eight Trans Tech SST-e minibusses. The buses cost a fuel equivalency of 16 and 19 cents per mile to operate, compared with 82 to 86 cents per mile for diesel. The district is also averaging a range of 100 miles per full vehicle charge.

Shannon said Twin Rivers is adding a half-dozen new chargers within the next several months. It also plans to expand its fleet to 35 electric buses by the end of June 2020, and to 70 electric buses within five years. Range is also expected to increase to 150 miles per charge.

The district’s early experience dates back to 2017 and highlights challenges and lessons learned. For example, there were delays in getting electricity to the bus yard, plus using the right size of smart chargers for larger vehicles that negatively affected the ability to quickly deploy EVs into the fleet.

Twin Rivers discovered that the potential cost savings of sodium-nickel batteries that are used by Trans Tech compared to lithium-ion batteries, cancels out if the buses don’t start. Initially, if the buses went cold, it took two days to warm up to the point that they were functional again, the report said. The manufacturer believed it solved the problem by using a 12-volt battery to warm the nickel batteries.

Twin Rivers also learned that onboard heaters slightly drained the electric systems, which the manufacturers are also addressing. The district discovered that a managed charging infrastructure was needed to regulate overnight charging, rather than charging the EVs on demand. Shannon also reported that it can reduce its already low energy cost of $0.10 kW an hour.

Those issues aside, Shannon told the researchers that the district’s experience has been positive. He said he believes the district’s vehicle performance, along with the reduced labor and operating costs, “far outweigh the higher upfront costs,” when compared to diesel buses.

Twin Rivers paid between $60,000 and $100,000 for each new purchase, with the remainder of vehicle and charger costs picked up by multiple state and local air quality district grants.

Shannon told STN that a vehicle-to-grid project is set to begin within the next six weeks.

The U.S. PIRG report said the initial results were more mixed in New England, where three school districts piloted electric school buses that were funded by $2 million in grants administered by the Massachusetts Department of Energy Resources in April 2015. It was the nation’s first test of how electric school buses operate in a colder climate.

School districts in Amherst, Cambridge and Concord received $400,000 each to purchase a bus from Lion Electric Company—the first EVs the company sold in the U.S. The buses were placed into operation at the beginning of 2017. The Vermont Energy Investment Corporation (VEIC) monitored the program and collected data for the next 12 months. VEIC found that the buses operated well between zero and 75 degrees, with no significant impact on safety.

But VECI also found that each bus emitted less than half of the greenhouse gases of a diesel bus, and considerably lower levels of volatile organic compounds, carbon monoxide, nitrogen oxides, and sulfur oxides.

The study uncovered several additional challenges—most notably the large number of days the buses were out of service, compared to an average diesel bus. The study cited a range of minor glitches, such as faulty headlights, and major issues, like battery pack and computer system failures.

While Lion addressed those mechanical issues (the company also used the project to develop a system to remotely access bus computers to diagnose and repair problems), the study also uncovered smaller than expected energy savings. Usage per mile averaged out at 2.38 kWh per mile, rather than the projected 1.3 to 1.4 kW per mile.

VEIC analyzed that data and concluded that the longer the bus was charged, the more energy it drew—in part due to “vampire loads” that were associated with using auxiliary fans and heaters for the batteries.

“A charging duration of 10 hours or more (such as over weekends and school vacations) could more than double the buses’ per-mile energy use, from around 1.5 kWh/mile to more than 3 kWh/mile,” the U.S. PIRG paper stated. “VEIC concluded that this could be alleviated through the use of a managed charging system, which would allow the buses to remain plugged in for extended periods without actually charging the battery for more than the 6-8 [sic] hours usually required. Such a system would significantly increase the buses’ operating efficiency.”

The higher usage per mile rate over the year of operation resulted in total energy costs of $7,240 per bus, or 64 percent higher than was projected. VEIC found that nearly the entire cost difference was based on electricity demand charges. It determined that more evenly spreading out electricity usage throughout the day, configuring the buses not to use any energy at peak times, and drawing power only for as long as necessary to recharge the battery, would have resulted in nearly a $1,500 savings on the original projected electricity cost.

Stephen Russell, an alternative transportation coordinator with the Massachusetts Department of Energy Resources, told STN EXPO Reno attendees in July that an additional goal of demonstrating the potential revenue of the vehicle-to-grid and vehicle-to-building charging “was not quite ready for prime time.”

“Now, [the buses] are running well. We paved the way for other utilities to prove out the concept,” he told STN on Friday. “We do have a utility interested in the concept but no funds at this time to prove it out.”

Russell advised student transportation officials to make sure electric infrastructure is in place before their first school bus arrives. Requests for proposals should also include service levels, such as the location of the parts depot and availability of service technicians to troubleshoot issues.

The U.S. PIRG report also highlighted the transit EV experiences of Albuquerque Area Transit in New Mexico, Chicago Transit Authority, Clemson Area Transit in South Carolina, and King County Metro in Seattle.