ferred via heated engine coolant to heat exchangers in the floor or driver area via tube and fin coils with fans. The 12- volt with fans circulate air across the coils distributing the heat extracted from the coolant. “In the northern U.S. and Canada, it is common to have
shutters in front of the engine radiators and/or a fuel-fired heater to heat the coolant for cold weather starting and to supplement the heat from the engine,” he added. “In extreme cold applications, there is not enough BTUs or heat energy from the engine alone in the coolant to heat the vehicle, so a fuel-fired heater on a diesel is required.” Passenger body heat help warms the bus cabin in con- trast to warm weather, when it must be transferred out of the passenger area via the air conditioning system, Lehnert noted. Electric vehicles require a holistic solution to meet
requirements for safe student transportation, he said, adding thermal management systems optimize bus operation and range. Depending on the battery, the bus may need to operate in a temperature range requiring heating or cooling of the battery pack. “Battery thermal management is sometimes via air
movement or coolant circulation,” he contined, add- ing thermal management may be required to operate reliably and provide the driver and passengers a com- fortable temperature range. He said the most sophisticated electric bus systems
have a total thermal management system connecting and incorporating the movement and transfer of heat or cooling from areas when it is not needed to areas where it can be used to optimize the total vehicle operational range and efficiency. Base level air conditioning and heating of an electric
vehicle is similar to ICE systems, Lehnert said, but the cool- ing utilizes a high voltage compressor versus a belt-driven compressor on the engine and an electric high voltage coolant heater with a circulating pump to move heated coolant through the floor heaters or driver heater box. Higher level systems exist that may be more efficient
as well as more expensive and complicated, Lehnert said. However, he noted that pre-heating or pre-cooling the bus while on the grid to maintain its temperature and not re- duce or add heat to a battery can help mitigate challenges.
“In extreme cold climates, you can’t get around the
need for a small fuel-fired heater, which is counter to the zero-emission scenario,” he added. “Invest in the best possible insulation in the body, best thermal floor selection and look at improved thermal windows. These features may cost more initially but help under all condi- tions for the life of the bus.” Russell Schmidt, vice president of digital products for
InCharge Energy, said thermal management software platforms can help end users start the day with a ful- ly-charged fleet of EVs to successfully complete daily routes regardless of the weather. This can include auto- matically extended charging sessions to keep vehicle batteries warm for longer overnight charging. Thermal management software can also restart any
unintentionally interrupted charging sessions that may have occurred overnight, Schmidt noted. Frank Giradot is the director of marketing for BYD and
RIDE. He said the company engineers electric buses to work in all climate conditions, working with school districts and transportation providers to ensure their re- quirements are met. He noted the company’s extensive experience with electric transit buses worldwide. Jason Johnson is the associate director of trans-
portation for Horseheads Central School District in Horseheads, New York, where he works with 85 vehicles and services another 15 diesel vehicles for a small- er school district. He has overseen a migration of 70 percent of the fleet from diesel to gasoline due to check engine light issues, which Johnson said has resulted in fewer fuel and maintenance expenses, as well as being “mechanic-friendly.” But fuel mileage isn’t as favorable. Yet driver comfort has improved, he said, as seats are
fully heated within five minutes. Johnson noted gasoline buses start up and warm faster. Paul Baczewski, Webasto Group national account man- ager, commented that most engines will start at extremely low temperatures with some differences. Studies show diesel engines omit much more exhaust gases, especially particulate matter, when engine temperatures are low. Denny Coughlin, owner of the School Bus Training
Company, added diesel fuel with the proper additives should not gel temperatures as cold as 25 or 30 degrees
Does your school district/company currently have at least one
electric school bus in the fleet? No ..............................................................................................................................................80% Yes, and it is on route ...........................................................................................................18%
Yes, but it is not currently in operation .............................................................................2% (Out of 142 responses to a recent STN reader survey.)
42 School Transportation News • APRIL 2024
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