Montreal’s transit agency lifts the curtain on what it takes to convert a big-city depot to support electric buses
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May 5, 2023
Mehanaz Yakub

Electric Autonomy gets a guided, behind-the-scenes look at the Société de Transport de Montréal’s first electrified bus depot

As part of its electrification plan, the STM is working on a pilot project to upgrade its Stinson Transport Centre and bus depot with the necessary equipment and infrastructure needed to operate, maintain and recharge an electric bus fleet. Photo: STM

Electric Autonomy gets a guided, behind-the-scenes look at the Société de Transport de Montréal’s first electrified bus depot

Dozens of public transit agencies across Canada are overhauling their operations and fleets to make the switch to electric vehicles.

One transit agency facing this challenge is the Société de Transport de Montréal (STM). The STM is in the process of electrifying its 2,000 transit buses. The goal is to have 55 percent of its fleet be electric by 2030.

As part of its electrification plan, the STM is working on a pilot project to upgrade its Stinson Transport Centre and bus depot with the necessary equipment and infrastructure needed to operate, maintain and recharge an electric bus fleet.

“The detailed planning for the complete electrification of the Stinson Transportation Center is not completed…but it is certain that, in the long term, the centre will exclusively accommodate electric buses,” says a spokesperson for the STM to Electric Autonomy.

The green logos on the depot floor designates the parking spaces where an electric bus may park. Photo: STM

The Stinson garage is home to the STM’s first 30 12-metre battery electric buses. The e-buses are from Winnipeg bus manufacturer, New Flyer.

The first buses were delivered to Montreal in 2020.

Electric Autonomy took a tour of the Stinson bus depot for a firsthand look at the technologies in place to maintain and operate STM’s fleet of electric buses.

Depot charging configuration

The most noticeable feature upon entering the Stinson garage is the large green floor markings in four aisles of the depot. These colour-coded lines and rectangles indicate the spaces where the STM’s electric buses must park for charging.

Fifty-three satellite units along with 44 charging plugs were installed at the Stinson depot. Photo: Electric Autonomy

These spaces contain electrical equipment used to power the buses, says Alexis Gagnon-Fortin, Stinson’s electrical engineer.

There are 44 charging plugs inside the garage with speeds of 130 kW. The charging time for the buses is up to three hours and thirty minutes. But it depends on how much power remains in the batteries when the buses return to the depot, says Gagnon-Fortin.

Each plug connects to an overhead satellite unit (they look like transformer boxes). These link the buses to the charging stations.

The STM installed 12 Siemens charging stations with speeds of 150 kW inside an electrical room on the second floor of the Stinson transport centre.

Siemens 50 kW charging stations inside STM Stinson Transport Centre
A second electrical room houses four 50 kW chargers that provide charging to the electric buses in the maintenance area of the depot. Photo: Electric Autonomy Canada

The charging stations are far away from the plugs due to space limitations. They take up 18 to 25 per cent of the depot’s area and STM had to install 50 kilometres of electrical and fibre optic cables to connect everything.

According to Gagnon-Fortin, the transit agency looked at “local charging” where chargers are installed next to the buses. Outdoor charging was another option on the table.

“The advantage is that it is much simpler, however, it would decrease the number of electric buses we can operate in our transit fleet,” says Gagnon-Fortin.

The STM says that it hopes that technology will advance, allowing for smaller, more efficient chargers that require less space.

Charging plug at the STM's Stinson depot
The STM installed 44 CCS charging plugs at the Stinson depot. Photo: Electric Autonomy

Adding pantograph charging systems

Stinson is the first STM depot to undergo an electrification process. So, the transit agency took the opportunity to experiment with different charging technologies available in the market.

Along with the charging plugs, the STM also installed nine Pantograph Down Systems from Stemmann-Technik. These further maximize the available space in the depot and ensure efficient, flexible recharging operations.

Pantographs are a charging system that uses an apparatus from the ceiling to connect to rails on the roof of an electric bus to provide fast charging.

The charging process involves multiple steps, including detecting when a bus is stationary, activating a switch by the driver and ensuring proper alignment and communication between the pantograph, bus and charging station.

The STM set up nine pantograph-down systems, used to charge the electric buses. Photo: Electric Autonomy

The main advantage of this system is that it has faster charging capabilities (up to 150 kW per pantograph), compared to traditional plug charging, says Gagnon-Fortin.

But although pantographs have the benefit of fast charging, they also presented certain difficulties for the STM, adds Gagnon-Fortin.

One of the challenges the transit company faced was opting for the Pantograph Down System to meet their charging needs.

This system is more complex and less frequently used compared to Pantograph Up Systems, says Gagnon-Fortin.

In order to power the buses, the STM had to install over five kilometres of electric and fibre optic cable to connect the charging stations to the charging plugs and pantographs.
Photo: STM

The Pantograph Up System configuration attaches to the roof of a bus and rises up to connect with the charger. Pantographs are also typically installed outdoors, not indoors.

The installation of the indoor Pantograph Down System required blocking access to part of the ceiling in the depot. This can sometimes create technical communication issues between the chargers and the buses, says Gagnon-Fortin.

“[With pantographs] it’s a lot of steps and considerations that need to be made,” says Gagnon-Fortin. There have been some hurdles but “the technology is still maturing,” he adds.

Charging stations operation

Two rows of charging stations inside the STM's Stinson transport centre
These 12 Siemens charging stations are used to power the electric buses back in the depot. Photo: Electric Autonomy

Inside the electrical room of the Stinson Transport Centre, the charging stations perform “sequential” charging of the buses, says Gagnon-Fortin.

This means that once the first bus in a sequence finishes charging the next bus will start charging automatically. The buses usually charge up to a maximum of 90 per cent, per the advice of the manufacturer.

The electric bus fleet charges on a “first-in, first-out” basis in the depot, says Gagnon-Fortin.

“This is older technology compared to now, where there is dynamic charging where charging can happen in parallel, but this was what was available [in 2020].”

STM's signal concentrator box inside Stinson transport centre
The STM’s signal concentrator box was custom-made to fit its need to collect alarm data, electrical data and charge dates. Photo: Electric Autonomy

The benefit of having sequential charging is that it requires fewer charging stations (that take up a lot of space) and the chargers are more economical to maintain and operate.

In the electrical room, the STM built a signal concentrator box that collects data such as alarms, electrical information, and charge dates from the chargers. With this data, STM officials can remotely monitor the buses’ charging progress.

To prevent overheating, a ventilation and air conditioning (HVAC) system runs at the back of the electrical room.

Boosting power supply

Three disconnectors installed on wall inside STM's Stinson transport centre

The STM installed a dozen disconnectors inside its transport centre to cut off power to the chargers for security reasons. Photo: Electric Autonomy

The next phase of the electrification plan for Stinson is expanding the facility’s electrical capacity.

The centre currently has a load capacity of two megawatts of electricity. With the dozen 150 kW chargers in use, the garage is almost reaching its maximum load capacity, says Gagnon-Fortin.

In the future, the STM is looking to set up more charging equipment to be able to serve 300 electric buses at Stinson.

In other to for that to be possible, the load capacity of Stinson must extend to an estimated 10-15 more megawatts, says Gagnon-Fortin.

The STM is collaborating with the province’s utility provider, Hydro-Québec, to make sure the Stinson facility as well as all of the STM’s transportation centers, have enough electrical capacity to operate more electric buses by 2040. The goal is to have Stinson garage be 100 per cent electrified by 2028.

“The full electrification of each center will require significant investment to increase electrical capacity, not to mention the energy requirements to support a fleet of some 2,000 electric buses,” says the STM spokesperson. “We share the desire to ensure that our electric buses are charged as efficiently as possible. To do so, we will rely on software to optimize our charging operations, including smart, sequential charging and optimal timing.

STM’s next steps

In addition to the Stinson garage, the STM is also equipping three other bus depots with the necessary infrastructure to accommodate future electric vehicles. These facilities, all located on the east end of the island of Montreal, include one unnamed bus garage, a Saint-Michel bus garage specifically designed for paratransit vehicles, and the Bellechasse bus garage located in Rosemont–La Petite-Patrie borough, which is currently under construction.

“The Bellechasse bus garage will be the first bus garage in North America to make use of underground space. It will eventually be equipped with the facilities to operate an entire fleet of electric buses,” said Luc Lamontagne, innovation and IT executive director at STM, during a panel at the Impulsion International Summit on Electric and Smart Transportation conference in March.

The construction of the Bellechasse garage is expected to be completed by the summer of 2024. It will eventually house 200 electric buses.

STM says it is sharing its findings with transit agencies across Canada. As well they are keen to learn from others.

“At a certain point we want to be adding electric buses pretty much everywhere,” said Lamontagne. “We have a lot to tackle right now for electrification and we need to focus. I think that’s the key thing.”

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