The bus recharges at stops using its roof-mounted contacts that engage using laser guidance. Click to enlarge.

Although the high-power (600kW, 20s) charging of the high-power density batteries on the bus could result in load peaks affecting the local grid, the flash charger station flattens out the demand by charging batteries located on the wayside over a period of a few minutes while drawing a lower current from the grid.

As this current is up to 10 times less than would be the case without storage, the connection can be made with a cheaper and more readily available low-power supply.

Short top-up charges maintain the battery level until full recharge at a terminus. Click to enlarge.

A further 4- to 5-minute charge at 400 kW at the terminus at the end of the line enables a full recharge of the batteries. The terminal charger consists of an IGBT-based rectifier. This converts the incoming AC supply to DC in a similar way as is done for DC railways, trams or trolleybuses. However, the IGBTs provide the advantage of being able to maintain the output voltage at a desired level independent of fluctuations in the voltage on the AC network.

This is important for two reasons, ABB explains. The first is that the on-board battery chargers need to step up the voltage to charge the batteries and so the voltage provided on the wayside cannot be higher than the on-board battery voltage. Secondly, the voltage cannot be too low because then the current drawn would be too high for the required power.

The flash charger uses the same type of IGBT charger as the terminal but it has a lower power capacity. Its function is to regulate the amount of charging current flowing into the wayside batteries. When the bus connects, the flash-stations’ controller closes a contact on the output side of the batteries to discharge them into the bus.

A third type of charger is used for the depot, where a longer charge is applied to compensate the energy required between the operating line and depot location.

The innovative technology was developed by ABB engineers in Switzerland.

The decision to deploy TOSA on Line 23 was undertaken after the successful pilot of the first such e-bus on the route from Geneva airport to the Palexpo exhibition center.

The Line 23 bus route will be slightly modified in order to provide a fast connection to Praille-Acacias-Vernet, a new suburb being built to accommodate 11,000 flats and office space for about 11,000 employees.

When fully commissioned in 2018, the high-capacity articulated buses will depart from both termini at 10-minute intervals during peak times. The line carries more than 10,000 passengers a day and the replacement of diesel buses by TOSA e-buses reduces noise as well as greenhouse gas emissions.

As part of a separate award by HESS, ABB will supply 12 flexible drivetrain solutions for the buses including integrated traction and auxiliary converters, roof-mounted battery units and energy transfer systems (ETS), as well as permanent magnet traction motors. Both contracts include five-year maintenance and service agreements to ensure operational reliability, efficiency and safety.

ABB provides a range of technologies to support mobility applications such as railways, metros and electric buses and vehicles. Transportation and Infrastructure is one of the three customer groups, served by ABB alongside utilities and industry, and sustainable mobility is a key focus area within ABB’s Next Level strategy.