This report, aimed at public transport authorities, private operators and practitioners, presents an overview of the key steps and considerations needed when designing or retrofitting a zero-emission bus depot as part of accelerating zero-emission bus deployment in urban areas. It draws on the experiences of C40 Cities Finance Facility (CFF) projects on depot electrification in Guadalajara and Monterrey (Mexico), as well as a literature review of other international experiences.
While each depot is tailored to the demands of the service requirements, the guide aims to answer a broad range of questions that operators or authorities may have on how to electrify their depot, including:
- Which depots to select first to electrify?
- How does the electricity grid play a role?
- Can renewable energy be integrated into the plans?
- How do I calculate the electricity required?
- How much space is necessary for electrical infrastructure?
- What infrastructure is needed?
- How can we ensure that infrastructure now is compatible which needs in the future?
- What maintenance is required?
- How safe is a electric bus charging system?
- How resilient will the electric charging system be to future effects of climate change?
Depot electrification for zero-emission bus systems
While it is necessary to consider the financial viability of the operation, it is just as important to tailor the system to meet the unique demands of each city. This report therefore takes a conservative or risk averse approach to system development and errs on the side of caution, to help ensure that the system is able to operate effectively from the outset. Once an operator or public authority has gained experience of electrifying a depot and has gathered much clearer operational data, it is likely that the system can be optimised to give a much better balance in terms of financial performance (and technical performance), and lessons learned can feed in to further deployment of depots. Examples of this approach include having the potential to draw more power than initially planned for or installing more charging infrastructure than technically necessary.
One of the key considerations that operators need to plan for is space. The additional space required for transformers and charging points will leave less space for buses. If space is already limited within a depot the operator may have to reduce the number of buses operating or move a small part of the fleet elsewhere, either of which could be a significant operational hurdle. Similarly, the space requirements are likely to be considerably larger if both electric and ICE buses are operating out of the same depot because of the need for two separate fuelling/charging infrastructure systems.
It is generally recommended to avoid having buses parked in a manner where buses cannot move until another vehicle has been moved to minimise operational challenges:
- A parking space at a 45-degree angle with a 10m turning space should allow for relative ease of parking and turning for medium-sized buses.
Using this information it is possible to calculate the minimum area needed for a given number of buses. The guide includes worked examples of how to calculate the space required when transitioning to zero emission buses.