Breakthrough paths to the clean-bus future

ABB’s innovative technology is helping to turn the global idea of e-buses into a reliable reality

Cleanly and quietly, the electric bus rolls up to the stop. And in less time than it takes for passengers to alight and others to board, the vehicle’s rooftop battery receives a 20-second, 600-kilowatt refresher charge that enables the e-bus to resume its route through the city.

This innovative flash-charge technology, known as TOSA, will soon bring clean-energy efficiency to a 20-bus fleet in the city of Nantes, France, thanks to ABB.

As with many clean-energy breakthroughs, ABB’s flash-charging technology has taken a Big Idea -- the zero-emission battery-powered city bus -– and turned the vision into a reliable reality.

In this case, the company’s innovative approach has overcome two major barriers to the use of all-electric vehicles in public transportation: the frequent need to recharge the batteries, and the length of time each recharge requires.

Eliminating those obstacles means that battery-powered bus fleets can be more widely and rapidly adopted around the world. That would go a long way toward reducing or eliminating a major source of greenhouse gases and other air pollution.

There is certainly a gaping need for new techniques. More than half of the global population is now concentrated in urban areas, and that portion is growing. But in many cities around the world, the street-level mass transportation systems are outdated, overburdened and over-reliant on fossil-fuel engines. Even in cities where electric trams and other cleaner systems are in use, their routes often are too constrained by the need for tracks or overhead cables – or both.

And in many places where battery-powered all-electric buses or hybrid-electric buses are already in operation, the recharging typically involves an overnight procedure. What’s more, the on-board batteries must be so large that they leave little room for passengers.

That’s why the vehicles that will go into use in cities like Nantes show a potential path to the clean-bus future. These e-buses will have smaller, quick-charge batteries, will be big enough to carry many more passengers and will be able to change their routes as future circumstances and population patterns might require.

The flash-charging technology “provides a model for future urban transport and reinforces our vision of sustainable mobility for a better world” said Claudio Facchin, President of ABB’s Power Grids division.

The system ABB developed for use in Nantes employs alaser-guided robotic arm on the bus’s rooftop that connects to and then quickly withdraws from the overhead charging canopy. Other ABB components include a rooftop traction converter that sends power to the electric motors at the bus’s wheels.

Powering the bus stop’s charging station is a curbside transformer that takes the alternating current (AC) from the utility grid and converts it to the direct current (DC) used by the e-bus. Public safety is designed into the system: the overhead connectors are energized only when engaged.

Between trips, a longer and full recharge will be provided at the bus terminal. And even those sessions will require only 3 to 5 minutes, using the same roof-mounted connectors – whether for full-size hybrid electric buses or the newer all-electric models.

In Nantes, ABB won the $20 million contract to provide the TOSA system for buses made by the Swiss company HESS. The vehicles will be operated on a planned e-Busway rapid-transit system connecting the historic center of Nantes to local municipalities south of the Loire River.

The city’s public transport operator, Semitan, has ordered 20 double-articulated electric buses, each 24 meters long. These new larger electric buses will accommodate 151 riders each, more than one-third larger than current passenger capacity, for a total of nearly 2,500 commuters an hour. The system is to begin operating by the end of next year.

Another, more established, technology based on a common interface for fast charging city buses, known as OppCharge – for “opportunity charging” – is helping streamline the transition to e-mobility in cities throughout Europe, North America and Asia. As an industry standard, OppCharge makes it possible to use charging stations with electric buses from different manufacturers, avoiding compatibility problems.

Electric buses can connect automatically to ABB’s HVC Opportunity chargers, which feature an overhead charging mast with automated pantograph that charges the bus. Charging hybrid-electric and all-electric buses typically takes only three to six minutes size during a layover at the bus route’s endpoints.

“By using open industry interfaces like OppCharge we are providing a system that is open to all bus brands as well as other charger manufacturers,’’ says Frank Muehlon, Product Group Manager for ABB’s Electric Vehicle Infrastructure business. “We believe open interfaces and open standards are key for operators and cities to embrace the large scale adoption of carbon emissions-free public transportation.”

Besides enabling zero emission public transport, OppCharge allows the size of batteries on board the electric buses to be smaller, reducing the overall weight of the buses and therefore improving the energy efficiency of the bus network.

ABB has installed opportunity chargers for hybrid-electric buses in Sweden, Luxembourg, the United Kingdom and Canada, and is in discussion with a number of bus operators and manufacturers for future projects. In Belgium next year, the company will install fast-charging stations in Charleroi, for a fleet of hybrid-electric buses.

The technology for overnight charging continues to develop as well. With the new HVC-Overnight solution ABB provides an intelligent and cost-effective way to charge larger fleet electric buses during the night, ensuring clean transportation during the day. The technology allows for the intelligent distribution from one charger to power three buses without the need for depot staff to monitor the charging procedure.


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