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114 8.1 Overview Best practices for operation and maintenance of ZEB technology are still evolving since the ZEB market is maturing. Therefore, monitoring bus deployment data and evaluating performance will help inform any adjustments that should be made to your operational plan. ZEBs may require less preventative maintenance than diesel counterparts since they have fewer moving parts; however, there is not enough data from ZEB deployments in the U.S. to provide detailed insight into maintenance requirements. Many transit agencies have experienced issues with the availability of spare parts, where long lead times extend the time required for maintenance activities. In addition, the existence of high-voltage systems may require a licensed electrician or OEM-provided technicians for preventative service. Be sure you understand what service is required and the technician capabilities required to perform the service. Battery capacity will degrade over time, impacting BEB performance. However, battery health is complex and difficult to measure. Having a plan to measure and track battery health will help you estimate expected degradation, identify anomalies, manage warranty claims, and plan for future service capabilities. Best practices for the operation and maintenance of ZEBs and fueling infrastructure include: ⢠Promoting energy efficient driving behaviors. ⢠Monitoring battery state of health. ⢠Understanding and preparing for bus and fueling infrastructure maintenance activities, including spare part inventories and lead times. PHASE 8 OPERATION AND MAINTENANCE
Operation and Maintenance 115 8.2 Key Stakeholder Considerations Project Managers ⢠Ensure operations and maintenance departments are briefed on battery degradation and potential service impacts for BEBs. Identify useful blocks that your BEB fleet can complete throughout its entire service life. ⢠Establish a method to measure the battery capacity at time of delivery, and a schedule to periodically measure battery health at least once per year. Track battery degradation and any impacts on service. ⢠Monitor operator efficiency throughout the deployment. ⢠Facilitate coordination of OEM and maintenance staff to create a spare parts inventory and a catalog of ZEB components and lead times. Operations, Maintenance, and Facilities ⢠Consider incentivizing efficient driver behaviors to optimize ZEB use. ⢠Coordinate with OEMs and component manufacturers to create spare parts inventories and understand lead times for ZEB components. Procurement ⢠Coordinate spare parts procurements needed for ongoing ZEB maintenance. External Stakeholders ⢠Depending on the service required, licensed technicians or OEM-provided technicians may be needed for some maintenance activities. ⢠OEMs should provide suggested spare part inventories and indicate driver behaviors that can increase efficiencies. ⢠Third-party data monitoring services or OEM technicians may be required to measure battery health.
116 Guidebook for Deploying Zero-Emission Transit Buses 8.3 Operations Since the ZEB industry is still maturing, transit agencies around the country are learning how to optimize bus performance and utilization. Data from normal ZEB operat ions should be monitored and analyzed to inform potential changes to your deployment plans. Understanding how your buses perform in real transit service will allow you to make better decisions about what blocks are available, or how fueling practices can be optimized. 8.3.1 Driver Procedures Driving habits can significantly affect ZEB efficiency and performance. Work with your OEM to understand driver behaviors that can extend the range of your daily ZEB operation . Consider creating an incentive program that rewards good driving habits to achieve operational goals. 8.3.2 Monitoring Battery State of Health The usable capacity of bus batteries will degrade over time and the amount of degradation can be difficult to accurately and consistently measure. Ensure that you incorporate this consideration in your deployment planning, as a ZEB may not be able to complete the same planned service at the end of its service life as it was able to upon delivery. This is of particular importance for BEBs. Battery degradation is not as significant for FCEBs, as the typical allowed degrees of battery charge and discharge preserve battery health. Battery warranties typically guarantee a battery to 70% to 80% of the nameplate capacity. It can be difficult to know the absolute value of the usable battery capacity during the service life of your bus. This makes submitting warranty claims related to battery capacity a challenge. Some transit agencies use a contractor to conduct a detailed battery capacity test while others use OEM-provided test procedures to measure battery capacity. These tests sometimes require specialized equipment. It is important that your transit agency understands the complexity of accurately measuring battery health and determines a consistent method for measuring battery health (See Section 2.5.3: Major Component Useful Life and Warranty Considerations). Your transit agencyâs staff or the OEM should test the battery capacity at the time of each busâs delivery to establish a baseline for battery capacity. Then, create a plan for measuring this metric over consistent intervals of time (at least annually). The combination of these measurements will help you understand typical degradation, identify anomalies, and plan for future service capabilities. Some data monitoring services provide a measure of battery state of health. Be sure to review how the metrics are being calculated, and determine how to best apply them, if utilizing this information for planning purposes.
Operation and Maintenance 117 8.4 Maintenance Since many ZEB deployments are still in their adolescent stages, maintenance data for aging fleets is sparse. While ZEBs may have lower maintenance costs due to fewer moving parts, ânormalâ maintenance costs will become more apparent as the ZEB industry matures. NREL tracks and reports on maintenance costs for several ZEB deployments around the country. These reports are an excellent resource for transit agencies wanting to learn more about other agenciesâ experiences and lessons learned with ZEB maintenance. The sections below outline the significant components of ZEB maintenance (Figure 8-1). 8.4.1 Spare Parts Inventories Parts availability is a common issue with transit agencies deploying advanced technology buses (Eudy and Jeffers, 2018b). Require your bus and fueling infrastructure OEMs to provide a list of critical and recommended spare parts for on-site inventory to speed the repair process. For other spare parts, request that they provide pricing and common lead times to determine expectations for vehicle downtime. Coordinate directly with your OEMs or their component manufacturers to obtain the desired parts at the best cost. While delays on a bus repair due to part lead times can be difficult to absorb, fueling infrastructure (such as hydrogen station or fast charger) maintenance events can immobilize large portions of your ZEB fleet. Spare part inventories should balance the effects of downtime with the cost of keeping them in stock. Figure 8-1. Components of vehicle maintenance. Deployments in Action AC Transit in California experienced issues with the availability of bus parts with long lead times for delivery. One reason for the lead time is the need to order foreign supplied parts through a distributor. AC Transit found that their distributor only offered some components as kits. This added unnecessary cost for cases where only one part out of the kit was needed for repair. Working directly with the component manufacturer helps address this issue (Eudy et al., 2017).
118 Guidebook for Deploying Zero-Emission Transit Buses 8.4.2 Bus Maintenance Propulsion-related maintenance of your ZEB fleet may be lower than your non-ZEB fleet. Propulsion-related costs include repairs for (Eudy and Jeffers, 2018b): ⢠Fuel; ⢠Electric motors; ⢠Battery modules; ⢠Propulsion control; ⢠Non-lighting electrical (charging, cranking, and ignition); ⢠Air intake; ⢠Cooling; and ⢠Transmission. ZEB propulsion systems are more efficient and have fewer moving parts than conventional internal combustion (IC) engines, potentially resulting in less wear and tear. In addition, the lack of an IC engine negates the need for oil changes, while the use of regenerative braking typically lengthens the life of brake pads. As advanced technology vehicles, ZEBs typically contain onboard communication systems that continuously report error messages and issues to OEMs. This access to detailed bus data allows for quick identification of maintenance issues. A study of King County Metroâs fleet indicated the cab, body, and accessories system contributed to the highest percent of maintenance costs for BEB technology. Figure 8-2 shows maintenance costs by system for their fleets. For FCEB technology, the fuel cell-specific components and the onboard hydrogen storage increase the number of components for maintenance. A 2018 National Renewable Energy Laboratory report found that the majority of issues with FCEBs were due to balance of the fuel cell powerplant, including air handling and cooling (Eudy, 2018). Experience has shown that there are some driving differences with electric buses that reduce some of the wear and tear on brake pads. Bus drivers slow down differently with regenerative brakes. (Aber, 2016)
Operation and Maintenance 119 Figure 8-3 shows the cost per mile by bus system for various maintenance needs, reported by NREL. Figure 8-2. Observed maintenance costs by bus system at King County Metro (Eudy and Jeffers, 2018b). Figure 8-3. Cost per mile of maintenance needs by bus system (Eudy, 2018, page 12).
120 Guidebook for Deploying Zero-Emission Transit Buses For preventative maintenance activities, require your bus and infrastructure OEMs to provide a list of activities, the time interval, skills needed, and required parts to complete each task. Some activities may require expertise from licensed electricians or from OEM technicians. Maintenance costs may be higher for initial ZEB deployments as maintenance staff learns how to troubleshoot and repair unfamiliar systems. As your ZEB fleet grows, so will knowledge in anticipating and preventing issues with proper maintenance (See Phase 7 Personnel Training and Development). Comprehensive tracking of maintenance history will be useful in predicting maintenance needs. Establish a tracking process to ensure that the necessary parts are in stock to conduct the maintenance when needed. As of early 2020, there was little industry data on the maintenance required for fueling infrastructure due to immaturity of the market. The type of infrastructure will affect the maintenance required. Advanced features or communication systems will likely require more periodic maintenance than a basic unit due to the number of components that can malfunction, but many OEMs have remote diagnostic capabilities helping them to quickly identify issues. Require OEMs to provide maintenance manuals that outline preventative maintenance activities, as well as the time and skill needed to complete them. Manuals should also provide definitions of all fault codes with recommended troubleshooting or repair activities. OEMs should also provide a list of recommended spare parts. It is likely that a licensed electrician or OEM technician will be required due to risks involved with high-voltage systems. Depot charging stations will likely require minimal maintenance. They are often modular in design so that malfunctioning components can be replaced without disrupting the entire charging system (Smith and Castellano, 2015). 8.4.3 Fueling Infrastructure Maintenance Fast-charging stations require ongoing maintenance as they typically have cooling systems, filters, and other components that require preventative maintenance (Smith and Castellano, 2015). Your transit agency may need to procure special equipment and fall protection to conduct maintenance on overhead charging stations with high clearances.
Operation and Maintenance 121 All maintenance activities should be conducted in accordance with a written and approved procedure or manual. You should also consider having a risk review completed. The risk review details the activities to be performed, the risks associated with those activities, and control or mitigation steps required to minimize the risks (Sokolsky, 2016). A maintenance schedule must be completed and implemented. Include safety system testing in the maintenance schedule. A maintenance log must be maintained per NFPA Standard #2 (NFPA 2) and should detail: ⢠The maintenance activity performed and the date completed; ⢠The start and stop time of the maintenance work; ⢠Whether the maintenance was scheduled or unscheduled; ⢠If unscheduled, the reason it was performed; ⢠The name of the maintenance inspector; and ⢠A list of the components repaired/replaced, including serial number and/or certification number of the component. ⢠Costs Associated with Non-Residential Electric Vehicle Supply Equipment, U.S. Department of Energy ⢠Fuel Cell Electric Bus Evaluations, U.S. Department of Energy 8.5 Additional Resources
