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How to Adapt Your Bus Depot to Refuel and Service Hydrogen Fuel Cell Buses

5 minute read
Nov. 19, 2020
Article by David Yorke

As community leaders and transit operators plan the transition to zero-emission bus fleets, the question arises: “How can we adapt our existing bus depots to refuel and service a fleet of hydrogen fuel cell buses?” 

As you’ll learn in today’s article, the modifications are simple, straightforward, and well-understood. We’ll walk you through what depot adaptations are needed so you can successfully transition your fleet and begin providing clean, zero-emission transit service to your community.

Hundreds of major transit providers have successfully and safely transitioned to hydrogen 

Today, there are 3,400 fuel cell electric buses (FCEBs) in operation all over the world. Collectively, these buses operate from hundreds of facilities that have been converted for hydrogen. So, you can rest easy knowing that the question of how to convert and maintain your facility for hydrogen fuel cell buses has already been answered hundreds of times. 

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The modification process is simple, and as with any shift or transition, it’s helpful to learn from those who have gone before you, for insights on what the steps are and what to expect. 

To read the story of how London’s Tower Transit modified their service depot  for hydrogen, download our informational >>

If you have CNG buses, the updates may be minimal

Transit bus operators who are familiar with CNG (compressed natural gas) will appreciate how similar the codes and standards are for handling hydrogen, which is also a Class 2 flammable gas. However, a number of hydrogen's properties make it safer to handle than CNG, which is one of the key benefits of choosing it to fuel your fleet. 

(To learn more about hydrogen safety, see our blogs Dispelling Common Hydrogen Safety Myths and Hydrogen Fuel Safety: Essential Facts for Transit Operators.) 


If your maintenance personnel are trained in CNG, and your facilities are designed for a fleet of CNG buses, you will only need minor modifications to implement the necessary hydrogen infrastructure.

We’ll outline five required modifications below, but first:

Follow local regulations! 

The direction we provide here is for guidance only, but it will give you a sense of what may be involved as you transition to a zero-emission solution. 

Before proceeding with any modifications, ensure that you follow all local laws and regulations. Early in the planning phase, contact your local authorities and emergency response services for information and guidance. 

If you have any specific questions about this process, simply ask us at Ballard—we are ready to help, and will most likely have already solved your particular issue in another jurisdiction.

Preparing for fuel cell electric buses: 5 modifications needed for your existing bus depot

1. Put a defueling system and procedures into place

While the hydrogen stored onboard a bus remains inside its sealed system, there are times—such as after an accident, during specific repair and maintenance procedures, or in preparation for long-term storage—when the bus may have to be partly or completely defueled. Your maintenance depot will need a system for off-loading the fuel, plus your maintenance staff will have to be trained in this technical process. 

Normally, nitrogen, an inert gas, is used to purge the hydrogen from the system. The defueling system can either transfer the hydrogen gas from the vehicle to a storage tank, vent it to the atmosphere, or a combination of both.

When working in an indoor workshop, you need to ensure the hydrogen is properly vented outside the building. Even when working outside, it may be necessary to vent the hydrogen away from any potential ignition sources. This is a standard procedure when working with all combustible fuels, including fossil fuels such as gasoline, diesel, and CNG. 


2. Design your depot and workshop for safety

The hydrogen storage tank onboard a fuel cell electric bus is rigorously built to prevent leaks. Yet, just as with fossil fuels, it’s essential to integrate preventative measures and preparedness planning into the design of your depot and maintenance workshop to ensure safety. 

For example, hydrogen is lighter than air; when released, it rises. Any released hydrogen will end up at the highest point in the workshop—at the top of a peaked roof or sloped ceiling. Ensuring proper ventilation in these areas is key for maintaining a safe work environment. 

3. Install fire alarm, sprinklers, and a hydrogen detection/alarm 

Your facility will already have a fire alarm and integrated sprinkler system. When adding fuel cell electric buses to your fleet, you’ll need to install a hydrogen detection system as part of the monitoring mix. 

We recommend a two-stage monitor with Level 1 indicators (e.g. flashing beacons) that are activated at 20% of the lower explosion limit (LEL), and a Level 2, (with full audible alarm and flashing beacons) at 40% LEL.

Ensure that hydrogen detectors are also installed at the highest points of your premise, wherever released hydrogen could collect.

4. Remove sources of ignition 

Safety trainers teach of the “fire triangle”, the three elements that, when combined, can result in a fire: fuel, heat, and an oxidizing agent (oxygen). 

When making design improvements to your bus facility to accommodate fuel cell buses, you need to consider that hydrogen is properly handled. Keep heat (or other ignition sources) away from anywhere that hydrogen could potentially escape to. This will prevent two sides of the fire triangle from forming. 

Additionally, choose spark-proof electrical wiring in the hydrogen workshop. Keep hot works, such as welding, away from the hydrogen workshop or the designated hydrogen bay.


5. Provide adequate ventilation

Hydrogen, when released into the air, becomes flammable when it reaches 4-75% concentration. Adequate venting will prevent it from accumulating to this concentration. 

This could include anything from simple venting that provides an escape path, to more complex measures such as automatic or forced venting systems that occur when the hydrogen detection system reaches a pre-set level.


Final thoughts: With the right depot modifications, maintenance is manageable and routine

As with any kind of fuel handling or engine repair, there are safety precautions to put in place when adapting your service depot for hydrogen fuel cell buses. Once these adaptations are completed, bus operators and technicians will soon find the maintenance of fuel cell electric buses routine and enjoyable. 

We at Ballard have years of experience in helping operators make the transition to hydrogen fuel cell buses, and we would be happy to assist you with whatever advice or technical assistance you need in setting up your depot and maintenance workshop. 


Adapting Maintenance Facilities for Hydrogen

This informational will provide you with essential details on what's involved when modifying your bus depot to service hydrogen buses.

Download Now