Swiss Trolley plus, a collaborative project between the public transportation services of Zurich (VBZ), HESS AG, BFH and ETHZ, has developed a 15%-more-efficient hybrid electric bus.

Compared to the already high efficiency of conventional hybrid buses, this additional spike in efficiency was reached by using lightweight materials, improved battery technology and a newly developed energy management system. Equipped traction batteries are not only charged when connected to the contact lines, but also when braking and going downhill. This battery system allows buses to travel up to 30 km without contact lines, making the diesel motor for backup power supply obsolete while also reducing the burden on the city’s contact line network.

The integrated energy management system uses information about the bus’s GPS location along with elevation maps to ensure that battery charge is used optimally, i.e. batteries are not fully charged before long downhill sections. This advancement also extends battery lifetime, further lowering costs.

First test drives have taken place at the HESS AG facilities and trial operation without passengers is scheduled to start the end of February 2017. In the following two-year trial phase, it is planned to evaluate normal passenger operation on lines 33 and 83.

Prof. Vezzini’s group at BFH developed the traction battery system within Capacity Area A1. For more information, please visit the group’s website.

Prof. Onder’s group at ETHZ, active within Capacity Area A2, designed the energy management system. More information can be found here.