School Bus Electrification: Charging Q&A
More than 25 million American children are transported to and from school on a national fleet of 480,000 school buses, accounting for 80% of the total bus fleet in the United States. Today less than 1% of school buses are electric; however, with the push to provide clean transportation while lowering annual fuel and maintenance costs for school districts, school bus electrification has begun to move quickly in several US states.
Steve Bloch, the Western Region VP from the ABB E-mobility business, was interviewed about his thoughts on where the school bus electrification is headed and what the charging infrastructure landscape looks like.
How are school buses different from transit buses in terms of electrification?
When we look at the use case, right away you see that charging time is less of an issue with school buses than with other electric bus applications. DC fast charging may not be necessary if the bus has shorter morning and afternoon routes. A higher power 11 kw or 19 kW AC charger may be adequate. However, some school buses do not have an “onboard” AC charger, and those vehicles will require a DC fast charger.
The battery packs in electric school buses are smaller than transit buses too, from 100 to 200 kWh is typical, which translates to roughly 75 to 150 miles of range – where transit bus batteries are often greater than 300 kWh. So, the purchase price for an electric school bus is typically lower as well, perhaps $300,000 to $400,000, versus a transit bus that could be as much as $1 million due to the larger battery and longer range requirements.
How are the charging systems serving school buses differently? Do school buses all use the same charging technology?
The chargers themselves are lower-power versions of those you’d find in a transit depot. School buses don’t need to charge at 450 kW, so extremely high power chargers and ultra fast charging pantograph connectors aren’t necessary. Anything over 50 kW is usually overkill.
All school bus OEMs use the same CCS charger connection standard as transit buses, but the charging inlet can be located in a variety of different places on the bus so it’s good to have very long cables for reach. For example, ABB’s Terra DC Wallbox (24 kW) and Terra 54 (50 kW) DC chargers come with 23- and 20-foot long cables respectively.
What is driving electric school bus adoption? What agencies drive investment in school bus electrification?
Decades of research show how childhood asthma and related health issues are aggravated by air pollution and vehicle emissions – and recent studies have shown the air quality can actually be worse inside of the bus than outside of it. But school district budgets are tight, and upfront costs are still a barrier for some electric school bus fleets, so funding programs are critical to drive adoption.
A big boost came late last year with the Infrastructure Investment and Jobs Act. Among its clean transportation initiatives, it allocates $5 billion for America’s school bus fleet over the next five years, with at least half of that funding dedicated to specifically electric school bus programs, and the other half dedicated to clean school buses.
Agencies at the state level have been working for many years to drive clean school bus programs. In California for example, the California Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project (HVIP) offers rebates of as much as $100,000 per electric bus purchase. There’s also $2.7 billion in funding for state-level projects that’s been made available via the Volkswagen settlement, and state agencies have chosen to spend a third of that money on school bus programs.
In addition, some utilities are investing in school bus electrification programs. One of the main areas of focus is partnering with school districts to use smart charging programs to help districts lower their electricity costs. In a few cases, they’re helping finance upfront costs as well.
So, there is a lot of momentum with these programs to support initial costs. But even better, electric buses really show their economic value to school district budgets with lower operational costs, which pay off throughout their service life. Electricity costs, especially when managed by a smart charging program, can be significantly less expensive than diesel and propane fuel; and electric drivetrains require far less maintenance and last longer than their combustion engine counterparts.
Why is vehicle-to-grid (V2G) so attractive for electric school buses and why isn’t it mainstream yet if the use case is such a good fit?
With a V2G charger and V2G-capable EV, the power can flow two ways: to the vehicle battery just like a regular EV charging session, but then the battery can send the energy stored as power back to the grid in response to demand and pricing signals from a utility.
When you look at school bus fleets and their usage, they are a great use case to add V2G to the operational model. Utilities tend to need extra power during the warmest days of summer when schools are largely not in session, so you can envision fleets of grid-connected school buses intelligently delivering power back to the utility during peak demand periods.
Because V2G is a promising technology, a lot of work is being done with pilot projects and standardization, but there is still a higher cost for bidirectional charging devices along with more implementation complexity.
A more immediate strategy for managing electricity demands and related costs is smart charging, which you can think of as V1G, meaning it’s not bidirectional. Right now this is much easier to implement for school bus fleet operators. School districts who want to minimize electricity costs can take advantage of time-of-use rates. This is usually done using a software platform that can schedule charging when the utility rates are low, usually overnight, but perhaps also during the day when a surplus of solar energy is available.
It’s important to note that not all electric school buses support plugging in the station in the afternoon and starting the charge session at night because the vehicle may “go to sleep” to conserve its battery power. Fleet operators should check with the bus manufacturer to make sure they support delayed charging features.
What advice do you have for school bus fleets that are looking into charging infrastructure?
Redundancy is the lowest cost option to ensure the highest up-time of the vehicles and to ensure that the vehicles are always fully charged. Another approach is to purchase an SLA (service level agreement) from the station manufacturer and keep high-touch and consumable parts stocked. The best advice is to look at your requirements and put in the chargers you need based on the miles driven, number of vehicles and expected community growth. Now assume you need to meet those same requirements if a charger or two go down. For example, cloud data centers are rarely down for more than a couple of minutes or hours per year, and that’s because of the redundancy built into their network.
Another aspect to pay close attention to is the software capabilities of charging infrastructure. Every charger should be connected so that it can communicate and report data from all aspects of the charging process as well as vehicle actions. Additionally, connectivity is important for remote service support and diagnostics and software updates. In ABB’s case, our interface allows us to remotely diagnose issues, and we’re also able to tell the vehicle OEM “hey, you have a problem here” if we see charging errors on the vehicle side. This can happen with new bus models where the communications that support vehicle-to-charger interoperability require occasional software updates.
In some cases, a school bus fleet manager may implement a network back-end for advanced charging management, such as what can be done via OCPP (Open Charge Point Protocol). The software-side interoperability that OCPP provides is important for easy integration of any bus or any charger while a school bus fleet grows over time.
To learn more about electrifying bus fleets, the Electric School Bus Initiative is an advisory resource that brings together school districts and partner organizations to develop electric school bus transition plans and provide technical assistance.
About Steve Bloch: Steve Bloch is the Western Regional Vice President for the ABB E-mobility business in the United States, managing charging infrastructure business development for public and fleet EV segments. Steve has worked in the EV industry for nearly 10 years, and holds a Masters of Engineering and a Bachelors of Science in Electrical Engineering from Cornell University.
This article is supported by ABB.
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