Transit Electrification Q&A: Why Are Transit Operators Choosing To Electrify Their Fleets?

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Over the last couple of years, there’s been a surge of excitement surrounding electric fleet vehicles, especially transit buses as a key momentum-driver for the EV industry. Pat Hayes and Kendell Whitehead, who together manage ABB’s transit charging business in the United States, were interviewed to discuss what’s driving the transit segment — through the lens of charging infrastructure technology.

Why is the transit electrification market growing so quickly? What are the drivers?

Kendell Whitehead: The use case is very good. You have the buses traveling on the same routes with approximately the same time available each night to charge. It’s easy to optimize. Transit agencies are looking at total cost of ownership over the lifetime of the vehicles and the charging systems, including maintenance and personnel costs. Electric buses cost more up front but are much cheaper to operate. Fuel and maintenance costs for combustion vehicles can also vary a lot over the life of the assets, so predictability comes into play, too.

Pat Hayes: Even things like brake pads — they’re the same on ICE (internal combustion engines) and electric buses, but with regenerative braking, the pads on an electric bus will last years versus months on a comparable gas- or diesel-powered vehicle. Environmental and health concerns are also high on transit agencies’ lists and electrification helps address those head-on. Then you have funding — state funding grants are really helping to move electrification plans forward now. When you combine all of these forces pushing in the same direction, you have a very dynamic market.

How much bigger are transit bus batteries than those for passenger EVs? Do they charge at the same power level as passenger EVs?

Kendell: They’re much larger, five to 10 times bigger than those you’d see in a car. Fortunately, the size of the vehicle allows for larger batteries. In terms of capacity, they can be anywhere from 200 kWh to 400 kWh for a “normal” transit bus. But in cases where you have a long route, you might have a bus with 600 kWh or 700 kWh to get that extended range. It all depends on the particular application and operating environment.

Keep in mind that the whole system has to work together. So, for example, DC fast chargers in bus depots regularly operate at 150 kW in part because higher power levels would require larger, heavier cables. So, even if the bus could take a charge at higher power, it has to operate at a power level that is compatible with the charger. Pantographs don’t involve cables at all. Those systems operate at 150 kW to 450 kW, which obviously reduces charging time substantially as compared to the lower power chargers commonly used by passenger cars. 

Pat: Buses use the same mass-produced cells that passenger EVs use, but they’ll have as many as nine packs to get the capacity and power levels they need. The bus OEMs have gotten very creative about where they locate the battery packs on the vehicle. Some put them under the floor, where luggage on a coach bus would go, or in enclosures within the passenger compartment, or even on the roof. The configuration is driven by the use case.

Bus makers are learning all the time, too. They can tweak the algorithms in the battery management system (BMS) to optimize the bus’s performance. They can design different charge profiles to reflect different state-of-charge conditions — that’s all to protect the longevity of the battery.

Are transit bus charging systems like ‘regular’ EV chargers? How are they the same, and how are they different and why?

Kendell: Transit operators want low-cost, robust industrial systems. As a result, you won’t see any flashy user interfaces on transit fleet chargers like you do on public EV chargers. A simple indicator light and a mating connection — that’s about it. Less complex means fewer things that can break. They also operate at higher power levels.

An ABB depot charging installation for charging during breaks or overnight at 150 kW. Image courtesy of ABB E-mobility.

Pat: Transit agencies prefer automated connections like pantographs for ease of use, space savings, and eliminating cables on the floor. These chargers operate at higher power, as we mentioned earlier. There’s also a kind of historical organizational structure in conventional depots where the driver never touches anything with the fueling systems. So, a fully automated solution allows charging to fit into existing work practices: the driver pulls in, the pantograph connects the charger to the bus, and that’s it. Currently there isn’t anything like that for passenger EV charging.

Do transit agencies prefer to put their charging systems on routes or in depots (or both)?

Kendell: The answer is dictated by the specific operational needs of the transit agency and each one is different. For some, depot charging alone is adequate — they can run their routes all day and charge at night. We’ve seen other instances where an agency can do everything with on-route charging, whether that’s two minutes at a bus stop or maybe 30 minutes at a station while the driver eats lunch. TriMet in Portland, Oregon was able to take this approach with one of their lines.

Pat: Some agencies are doing hybrid (on-route and depot) charging. They might have just one DC fast charger (DCFC) in the depot for fast charging in a pinch, for example, and more chargers on route. Depot charging is generally less expensive since it’s usually done at night when rates are lower. Every transit agency has different strategies for charging their fleet. Some utilize depot charging, some opportunity charging, and more and more are incorporating both strategies for a hybrid scenario.

Do current DCFC standards for connectors used with passenger cars (such as CCS1 and CHAdeMO) apply to transit? Are there any standards unique to Transit/Buses? Are there any proprietary standards, such as with Tesla?

Kendell: CCS1 is the de facto standard for heavy vehicles in North America, as with passenger vehicles. We’ve even tested chargers in transit facilities using cars before the buses were delivered to the agency. CHAdeMO isn’t really relevant in heavy vehicle charging. There are some proprietary standards from the vehicle OEM side, but the industry seems to be strongly converging on CCS1 for cable-connector based charging.

Pat: Pantograph chargers are almost exclusively for bus applications and we expect these to continue as a popular option for the reasons noted earlier. Some OEMs are looking at a pin-in-socket version of the pantograph standard (SAE J3105) that would also be automated. Ports are looking at this, too. There is also the Megawatt Charging Standard (MCS) being developed by a CharIN committee for heavy trucks that may come into play for buses as well.

How are utilities engaging with transit electrification programs?

Kendell: Transit electrification is both exciting and terrifying for utilities. It’s a large, consistent source of revenue and much of the charging happens off-peak, which normalizes their base load. But obviously adding multiple chargers to a depot represents a major new load that may involve substantial upgrades to the local grid.

Our advice to transit agencies is to engage their utility early and often. Foster relationships; create transparency around project needs. The key is to get ahead of any potential issues. Ideally, the agency and utility work together not only on the physical installation, but on things like using demand response to allow chargers to power up or down depending on grid strain; or creating special rates to reduce demand charges and make the business model for going electric more sustainable.

Pat: In practice, the owner of the charging infrastructure is either the transit agency or the utility itself due to the size of the load, but regardless there is skin in the game on both sides. Permitting and overcoming grid constraints can take a long time, which is why we emphasize engaging early. On our projects, the team always includes both the agency and the local utility, and we really do look at it as a project versus just a “sale.” It’s about collaboration because it has to be for the transit agency to be successful.

It’s also worth noting that utilities are in an excellent position to help transit agencies in their transition to electric buses by providing consulting and related services. They have the technical expertise and an intimate knowledge of the grid, so why not sell it?

What must transit agencies consider when adding high-power charging to sites that traditionally served fuel-based vehicles?

Kendell: There are a lot of things to consider, which again is why you want to work with the utility early on. You’ll likely need transmission and site electrical upgrades, but it varies. Chargers in one installation might be equivalent to building a McDonald’s restaurant or they could be like dropping a 10 MW data center at the edge of the grid.

Interoperability is key. You want to make everything work together so users have confidence in system, so it’s vital that the vehicle OEM and charger OEM have a good relationship in order to address any unforeseen problems or novel configurations. Transit agencies are in a good position to drive that conversation.

One area that is often overlooked is training, which impacts how operators work with the vehicles. It can add challenges, so again it’s important to address early on.

Pat: Transit agencies and utilities both have long-set processes. Switching to electric buses requires a change of mindset in many cases. For example, in trying to address demand costs there are some interesting solutions that have come out of California. One involves the utility creating a special bus charging rate (with lower demand charges) in exchange for the transit operator agreeing to purchase a certain amount of power over some period of time. This arrangement provides each side with certainty that improves the bankability of the project.

Who should transit agencies talk to about charging?

Kendell: There’s a certain fellowship among transit agencies, and I would say they should leverage that since there is already good communication among them. Consultants focused specifically on bus electrification (such as Center for Transportation and the Environment) have also helped transit agencies by providing information on market trends and convening agencies at conferences to share experiences, for example.

Pat: Aside from the local utility, I’d say the bus and charger OEMs. Early engagement is critical with each of these as they will all be working together over the duration of the project and beyond.

Name one thing you wish every transit agency knew before they begin the shift to electric.

Kendell: It’s a long journey. There’s more involved in electrification than a charger and a bus: the utility connection, charging management software, networking, service partners … the list goes on.

Pat: The idea that an EV should replace an ICE vehicle one for one is not necessarily the right approach. You may be able to optimize better if you “start over” with electric buses and design the support systems from there. It’s important to remember this is not simply a vehicle replacement.

ABB’s E-mobility team will be at the APTA TRANSform Conference & EXPO, a major industry trade show dedicated to public transit, taking place next week in Orlando. As a recognized leader in the electrification of transport for decades, ABB E-mobility has sold more than 460,000 EV chargers — including more than 21,000 DC fast chargers — in more than 88 countries around the world.


This article was supported by ABB. Images courtesy of ABB E-mobility.

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