Some of the issues that transit agencies need to consider include: • Electric buses have a range based on varying geographical terrain, passenger load and ambient temperatures. This has a huge impact as the agen- cies will need to define new ways to meet service demands balanced by recharging intervals. • When buses have to be brought back to the depot for charging in the daytime, that likely uses power at the peak rate, which will increase the agency’s costs. • The installation of an en-route charging system on the street requires special permits and approvals from the local municipalities, which can add to the project timeline. • Scaling up the number of buses to accommodate range and power requirements adds cost for the infra- structure, as more buses are charged at the same time. • Electrification requires new training of the workforce on safety and maintenance of the battery technology and the high-voltage charging systems. • Transit agencies often need help working with the power and utility companies in the early planning stages of fleet conversions. Q: How does conversion to an electric fleet affect the workforce? A: Workforce development is a major issue. Transit is expecting 30-40 percent of its current workforce to be eligible for retirement in the next two to three years. Layering on adoption of new technology will require a major invest- ment in training for employees across the board, from those who will be charging the buses in the depot, to the mechanics and bus operators. This will change the entire face of workforce as we need technicians with troubleshooting and repair skills to understand the complex propulsion and
control systems as well as electricians who can work on high-voltage systems. To accommodate these changes, transit agencies might have to pay more for these new skill sets and certifications. Additionally, employees will now be working around high-voltage equipment, so new and improved safety policies, procedures, and pro- tective equipment will be required. Some agencies that also operate electrically driven rail systems will have experience that can carry over to the electric bus program. Q: What technology is coming down the pike that will affect electric vehicle capacity and range? A: The battery is the heart of the electric bus. It’s a rapidly chang- ing technology that is gradually bringing down electric bus costs, while extending the average duty cycle. The goal for manufacturers and transit agencies is to extend the range of vehicles without adding
extra batteries, thereby making them more efficient. Manufacturers are currently working to improve the energy output, storage capacity and density in batteries without adding significant weight through the use of alternative battery chemistries such as nickel-manganese cobalt lithium-ion and lithium-iron phosphate. The solid state battery is in currently development stage, and in the future this investment will help address the current challenges with the efficiency, range and weight of the batteries. New charging systems could also offer solutions to improve range. En- route charging stations have been designed to fast charge a huge bank of on-board batteries while buses dwell at stations to receive passen- gers. Wireless inductive fast charging systems using magnetic fields to transfer power between two coils of wire (one on the bus and the other under the roadway surface) over an air gap with no physical connection are also being tested. This makes it easier to charge the bus en-route, or in the depot at designated inductive charge zones.
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csengineermag.com
july 2020
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