Part of what makes a full-scale deployment of electric buses difficult is the integrated, detailed analysis necessary to develop a fleet electrification road map. The analysis may seem overwhelming as it covers several areas that cannot be evaluated individually. Given that the transition will occur over multiple years, the plan will need to address maintaining a diverse bus fleet during the transition period, working within the capital budget constraints, and minimizing impact to existing and future operations. A few keys areas should be assessed once the decision has been made to electrify a fleet.
Route And Fleet Analysis
Bus routes are already well-established within a transit agency’s service territory. Routes are added or removed over time based on ridership, urban expansion and future demand. These elements will continue to drive route planning; however, the location, availability or need for charging infrastructure will be a new element for consideration in route planning. Comprehensive route analysis is an important step in building an electrification plan.
Before performing the route analysis, it is important to understand the technical parameters or limitations of the commercially available technology. These parameters are based on a snapshot in time and feed into the route analysis, so potential technological advancements should be considered. Evaluating multiple vendors allows the transit agency’s electrification road map to maintain flexibility and minimize the potential of stranded assets. By understanding range and charging capabilities under a variety of environmental conditions and use cases, transit agencies can determine the appropriate fleet to meet their needs.
Once technical parameters are established, the detailed route analysis may be performed to marry the parameters of electric buses with the characteristics and timetables of routes, identifying potential charging windows and determining whether the route can be electrified given the parameters selected. The analysis can also be modified by adjusting the parameters, resulting in multiple solutions. For example, varying battery sizes or charging powers could result in a one-depot-only charging solution or a combination of depot and on-route charging. Or the analysis could determine that multiple on-route chargers are needed or that an additional bus is needed to maintain the desired level of service. Analysis results can also prioritize routes for electrification. For example, a transit agency may elect to prioritize routes that can be electrified by using commercially available electric buses and depot charging while delaying other routes that cannot.
Regardless of the methodology, a transit agency’s analysis could result in a fleet of short-, medium- and long-range electric buses with various high-powered chargers, both in the depot and on-route, to align with future ridership demand and mobility.
Coordination With The Electric Utility
Understanding electrical limitations depot-only, as well as on the local distribution system, is a must when building an electrification road map. Limitations may not impede a transit agency’s ability to move forward with fleet electrification but could impact scalability and timing. Therefore, it’s essential to engage the electric utility early and often to navigate this coordination process.
First, agencies should understand the electrical service at their own depots. A fully electrified depot could be a 20- to 30-megawatt (MW) demand customer. While existing infrastructure may be adequate to support a pilot program, electrical infrastructure upgrades may be needed to support a fully electrified fleet charging at the depot. The same applies for local distribution networks. The utility must analyze current and future demand to confirm its local distribution system can meet the agency’s needs, and may need to provide a sub-transmission line and substation to the depot. To help, transit agencies must be able to provide details around the timing and number of buses introduced at the depot — an electrification road map can provide these answers.
On-route charging is a little more challenging, as transit agencies need to optimize the location, making sure it is an adequate place for a utility connection, provides enough charge at an opportune time, and easements can be obtained. More coordination is necessary with on-route charging, as the transit agency is usually considering multiple on-route charging locations.
Electricity rates are another important operational cost consideration for electric buses. Transit agencies must understand the local utility rate schedules and types of rates available, which can vary by time of year, time of day and by utility. Some utilities have EV-specific rates, while others do not. Typically, commercial customers are charged in three ways: customer charges, usage charges and demand charges. Demand charges can significantly increase operational costs, especially when utilizing on-route charging. To mitigate demand charges, transit agencies could optimize charging by staggering charging, charging during off-peak hours, or using on-site renewable power or battery storage to meet their needs. In some instances, utilities have even waived demand charges, for a period, to help minimize electricity costs. Regardless, implementing optimized charging to minimize electricity costs should be easier for depot charging in comparison to on-route charging. On-route charging is done out of necessity, limiting the ability to do so. However, it’s still important to consider electricity costs based on usage and demand when selecting on-route charging locations.
Integration of Renewables and Storage
Many transit agencies have already started to use renewable generation sources by installing solar on the rooftop of their maintenance facilities. With fleet electrification driven by the desire to reduce GHG emissions, it makes sense to increase the use of renewable generation. Storage may become a necessity, depending on how the renewable power supply is sourced, and can provide benefits such as load smoothing and soak up renewable over-generation during peak times.
There are multiple options for sourcing renewable power: on-site generation, off-site generation and green rates through the electric utility. While transit depots come in all shapes and sizes, it’s unlikely most have adequate space for on-site generation and storage. A depot for 120 to 150 buses may only be a site of 8 to 12 acres, not nearly large enough for solar-storage combination without costly site layout creativity. Off-site generation or green rates may be more probable because of space constraints, but might be costlier and unable to operate during an outage.
While each situation is unique, finding a middle ground that incorporates both on-site and off-site renewable generation and storage is a probable solution. The on-site renewable generation and storage will allow the transit agency to minimize costs, capitalize on renewable over-generation, and go off-grid during an outage, while the off-site renewable generation will maximize space utilization at the depot. Backup generators can be incorporated into the on-site microgrid to supplement needs during an outage or emergency. Transit agencies must understand the available space as well as the forecasted demand at each depot to determine the best approach for integrating renewables and storage.
Impacts to Operations, Maintenance and Training
Intelligent route analysis coupled with the appropriate technology should minimize impacts to route operations, but each situation is unique. Route schedules may be adjusted to provide additional time for charging, whether in the depot or on-route, or additional buses may be added to maintain the same level of service. Transit agencies should be prepared to assign buses to specific routes, especially if a transit agency wants to avoid on-route charging.
Each bus will likely have a unique charging window, requiring a mix of high-powered chargers. This may facilitate the need to assign buses to specific parking spaces in the depot if a transit agency does not install uniform, high-powered chargers. The flow of the depot and available parking should influence the type of chargers installed, whether pedestal- or overhead-mounted. Cord management procedures — a simple but often overlooked challenge — or the use of automated, contact charging also need to be considered. Changes in the order of operations such as fare collection and washing once buses return to the depot may need to occur to accommodate charging. Identifying these operational changes is paramount for complete fleet electrification, but especially for incremental deployment of electric buses to minimize impacts to customers while operating mixed fleets.
Maintenance programs will also need adjusting, even though electric buses require less maintenance. Maintenance personnel will need training on new procedures, potentially at differing frequencies, and record keeping and reporting must be adapted. Maintenance on new equipment, such as chargers, on-site generation and storage, will require a specialized maintenance program and skill sets or might need to be outsourced. Most importantly, any and all changes to maintenance procedures must be rolled out while simultaneously maintaining existing assets. Bus manufacturers provide adequate support services during pilot implementations, but a strong change management program is beneficial to support complete fleet electrification because each phase will convert a small subset of personnel at a time.
Operators will also require detailed, specialized training on the nuances of driving an electric bus. As with maintenance support services, bus manufacturers provide adequate operator training services during pilot implementations, but a revamped training program is needed for all ongoing operations. New EV fleet monitoring solutions enable vehicle operations to be linked to a specific operator, which can be used to highlight specific training needs of individual operators. Targeted operator training could help an agency maximize vehicle range and minimize electricity costs.
New Hardware and Software
A smooth transition to an electrified fleet requires the integration of new hardware and software, which is becoming more commercially viable and available. Industry organizations are working to make it more standardized to mitigate concerns of stranded assets. Regardless, transit agencies should use findings from their route analysis to identify the number of and appropriate size of chargers and determine a charging strategy. There are two extremes with combinations in between that a transit agency could utilize. One extreme is a dedicated charger for every bus while the other is optimized charging via a minimum number of chargers.
Depending on the charging strategy, an EV charging software platform may be a critical addition to the transit agency’s software suite. Such platforms provide value by enabling visibility into charging operations and allowing a transit agency to perform load management through charge optimization or load smoothing to minimize electricity costs. The platforms can integrate distributed energy resources, such as battery storage or on-site generation, to minimize electricity usage during peak hours. The great news is that once the fleet is completely transitioned to electric, traditional fueling software tools are no longer needed. The new platforms provide realtime insights into charging operations and the opportunity for predictive analytics.
Establishing a Capital Budget
As with any project, the implementation of the electrification road map must fit within budget constraints. Transitioning to an electric fleet will occur in a multiyear rollout, meaning certain routes or regions of a transit agency’s service territory will be electrified at a time. Therefore, a transit agency could build its capital budget around a phased implementation or set an annual budget for electrification and build an implementation plan around it.
Regardless of the methodology, the transit agency must carefully plan its capital expenditures. An electrification road map will help establish a capital budget by identifying an end-state as well as incremental phases along the way that include vehicle and infrastructure costs. To help fund the transition, transit agencies should take advantage of state and federal grants, as well as transportation electrification programs that shift costs of infrastructure installation to their electric utility. While not widespread, electric utilities across the nation have initiated or are exploring transportation electrification programs.
Changes to the Depot
It’s safe to say that the bus depot of tomorrow will look different from the depot of today. Renewable generation, energy storage and chargers will shape the depot of tomorrow. Maintenance facilities, such as engine and transmission overhaul facilities, will be repurposed. Traditional fueling facilities will be eliminated altogether. To add to the complexity, modifications will need to be implemented over a five- or 10-year period, all while maintaining service operations.
Determining charging needs and a charging strategy will help inform the number of chargers needed, allowing an agency to assess potential reductions in yard space or impacts to bus flow. Because depots are typically located in industrial areas with limited room for expansion, a transit agency will need to optimize its depot space. Some agencies will have the luxury of building a new depot, but those that don’t will need to be creative with their space as they look to incorporate high-powered chargers, renewable generation, energy storage, backup generation or a distribution substation at their depots. One appealing option for transit agencies may be to construct a building shell overtop their existing depot. This shell could provide a way to elevate charging equipment, eliminating the potential for operators to drive into it, minimizing implementation costs as wire and conduit are installed overhead rather than underground, and providing space for more on-site solar.
Designing and installing the infrastructure is not necessarily a complex task; however, doing so while trying to implement the plan over several years and maintaining minimal impacts to operations and services can make it quite complicated. An electrification road map can help a transit agency mitigate unforeseen issues, as the road map breaks the implementation into multiple phases.