Concentration of CO2 in the Atmosphere

Vermont’s Electric School Bus Success Story

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Martin Wahl

South Burlington Schools celebrates one year of successful clean electric bus transportation for students across the district.

Burlington, Vermont school district’s four electric buses completed more than 30,000 miles of clean driving last year, offsetting more than 100,000 pounds of CO2 equivalent emissions, and were ready to get rolling when students headed back to school on August 30. Bi-directional chargers allow electricity to flow from the grid to charge the electric vehicle’s (EV) battery and also to flow from the battery to the grid. South Burlington’s installation included four bi-directional chargers allowing the district to share energy stored in the buses’ batteries during periods of peak energy use. Synop, a software company for EV fleets, manages the Vehicle to Grid (V2G) transactions through its charging and energy management platform. When stored energy in the buses is transferred to the grid, it is the equivalent of taking about 80 homes off the grid during those peak energy times.

The South Burlington District received a $965,000 Vermont state grant from the VW Environmental Mitigation Trust Funds to help purchase the buses. Green Mountain Power (GMP) provided additional incentives towards the buses and V2G chargers. Based on the reduction in carbon emissions the project was estimated to achieve the equivalent of taking 905 gasoline powered cars off the road. Fossil-fueled transportation is a major source of carbon pollution in Vermont, and switching to driving with clean electricity is the biggest step we can take to help reach emission reductions goals. GMP’s energy supply is 100% carbon free on an annual basis.

OK, How About in Winter?

As a result of another Vermont initiative, the State’s Department of Environmental Conservation issued a report in June of this year on its Vermont Electric School and Transit Bus Pilot Program project conducted by the Vermont Energy Investment Corporation (VEIC). The two-year vehicle testing period ranged from spring of 2021 through spring of 2023.

One of the project objectives was to determine how the buses would perform in cold weather. The project found mixed results:

It is feasible to operate electric school and transit buses in Vermont even in cold weather and varied terrain. The success of that implementation, particularly in winter, may vary between bus manufacturers. Some brands performed well in winter, and some failed to perform at all. Among the buses that were in-service in the winter, some buses performed better than others. Charging equipment performance remained a persistent issue for all sites year-round … however, most electric buses performed well on daily routes with more than enough battery range, even in cold weather. All project partners realized fuel cost savings and greater efficiency over their diesel counterparts. In-service days showed the greatest variability. One bus had a perfect service record (a Lion bus) while others were out for significant periods for service.”

While South Burlington’s Thomas Built school bus model was not included in the VEIC study, a similar bus performed well in Alaska over the winter months. The big issue there was keeping the interior of the bus warm – it required more energy to do that than drive the vehicle!

Keeping passengers warm in winter is a concern in colder climates: some electric bus manufacturers resolve this by providing diesel-fueled heaters, reminding us that part of the efficiency of electric vehicles is that they do NOT generate much waste heat, which provides the heat we take for granted from fossil-fueled vehicle “heaters.” A solution previously used in some earlier air-cooled gasoline powered vehicles with heat management issues, most notably Porsches, gasoline-fired heaters kept passengers warm on chilly days.

No information was provided about the consumption of diesel fuel for the heaters compared to consumption of fuel, and related emissions, of diesel-fueled buses.

What Else?

In addition to the greenhouse gas (GHG) emission reduction, electric buses provide cost benefits as well.

Traditional diesel school buses get an average of 8 miles per gallon (mpg), dismal, but better than city transit buses that clock in at an astonishingly low 4 mpg. As the Vermont Department of Conservation’s report shows, the GHG savings resulting from replacing transit buses with electrics is more compelling than for school buses. However, the additional benefit of eliminating diesel exhaust particulate emissions around kids is significant, and integrating school bus batteries in a “smart grid” promises future cost and GHG reduction benefits.

Electric school buses are three times as efficient as diesel buses when comparing diesel fuel miles-per-gallon to electric versions’ miles-per-gallon equivalent as measured in miles per kilowatt hour of electricity used. Maine discovered that the cost of charging them was 40% to 75% cheaper than fueling diesel versions, depending on variations in diesel fuel and electricity costs. They also anticipate reduced maintenance costs due to fewer parts and the reduced brake wear of regenerative braking. The VEIC report however notes that because of the higher upfront costs of the electric buses and the charging equipment, “[without the funding sources available to help offset the cost of the project for each partner, buying electric buses outright would have been cost prohibitive.” Nevertheless, electric school bus providers maintain that their buses are cost-competitive with diesel versions considering the lower fuel and maintenance costs over their lifetimes.

After a career in data product management, Martin Wahl has worked in biofuels since 2006, currently with Lee Enterprises Consulting, a large bio-economy consulting group. Dividing his time between California and New Hampshire, he serves on Corte Madera, California’s Climate Action Committee and is a Newfound Lake Region Association member.


Image: Thomas Built Buses

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