As anyone who commutes into a major city around the world will tell you, it’s often easier to take mass transit than it is to drive, reducing stress and congestion at the same time. It’s also cleaner too, especially if you’re replacing several hundred private cars with one train, or 80 separate cars with one bus.
While replacing many cars with mass transit can help ease congestion however, there’s still emissions from the bus or train in question. And while many city centre trams and metro systems use electricity as their power source of choice, most buses today rely on the suck-squeeze-bang-blow of a diesel internal combustion engine.
In the last few years however, we’ve seen a steady growth in the number of cities around the world welcoming all-electric buses onto their roads for short city-centre routes as part of pilot projects designed to clean up a city’s mass transit system. To date, most have been aftermarket conversions of existing bus models or limited-production custom-built electric buses from brand-new companies keen to make a mark on the electric bus segment.
But now one of the largest bus manufacturers in the world has helped electrify a bus route in Gothenburg, Sweden with a fleet of fast-charging, all-electric buses that not only reduce carbon emissions in the Swedish city but also provide the latest in transportation technology for their passengers, too.
Enter Volvo, a collaborative project in Gothenburg called “ElectriCity,” and Gothenburg’s route 55 — which runs from Chalmers Johanneberg to Chalmers Lindholmen via Gothenburg City Centre. Aided by the work of ElectriCity — a collaboration between various industry leaders, governmental bodies and academic institutions, the city of Gothenburg was able to to install a new set of bus stops, charging systems and traffic management systems designed to make the electric bus route possible.
The result? Earlier today, Volvo introduced three all-electric buses to Gothenburg’s route 66, supplementing the existing seven hybrid electric buses already in service on the same route. In addition to offering full zero-emissions capabilities, the buses boast complementary on-board Internet connectivity via an on-board Wifi for customers, as on-board USB sockets for mobile phone recharging.
Unlike some electric buses we’ve seen in the past, the electric buses introduced to route 55 today make use of overhead rapid charging technology designed to allow the bus to quickly recharge en-route without significant down time. Similar to some of the technology used in Proterra’s electric buses, Volvo’s rapid charging system makes use of specially-designed bus stops with an overhead cantilever which lowers onto the top of the bus to transfer high-current power to the bus battery pack while passengers are getting on and off the bus.
With such high charging currents, Volvo had to design a special battery management system to keep both the bus and its battery pack happy. The result was the Energy Storage System (ESS), which Volvo’s cheif engineer of the ESS system Niklas Legnedahl says is extremely versatile.
“We buy the battery pack, but the control and functionality around it is our own,” he said. “We are far ahead in this respect.”
Designed to be modular, Legnedahl says Volvo’s ESS system is versatile enough to be used on both hybrid electric buses, as well as with different types of battery cell chemistries in the future.
At the moment, the ESS is programmed to work with lithium-ion battery packs made up of 192 cells connected in series, with either a single pack in the case of hybrid electric buses, or four battery packs connected together in the case of an electric bus. In the case of the electric bus, total system discharge power is 170 kilowatts, with a total battery capacity of 19 kilowatt-hours.
When it comes to charging, Volvo says 8.5 kilowatt-hours of electricity can be fed back into the battery pack via the overhead charging apparatus in about 6 minutes, which last about half an hour on the route. Moreover, some of the charging stations en-route are incorporated into fully-enclosed drive-thru shuttered bus stations, ensuring that the bus and its passengers are protected from the elements during the brief charging stops.
Designed to cover around 60,000 kilometres (37,282 miles) per year, Volvo predicts that the battery pack used in its hybrid buses will need replacing after every 6 years, while those in its electric buses — which are put under a much higher strain — will last 4 years before replacements are necessary.
That might seem like a short period when compared to the lifespan of battery packs in electric cars, but as Volvo explains, the high-charging and high-cycling of these packs means that 4-years is more than acceptable when considering they’ll cover at least 150,000 miles before needing a replacement.
“The Volvo Group aims to be the world leader in sustainable transport solutions. A unique collaboration in Gothenburg enables us to launch the electric bus route here and remain a leader in the development of future public transport,” said Niklas Gustafson, Chief Sustainability Officer for the Volvo Group.
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