ETH software makes buses smarter

A new electric bus with a hybrid electric drive system has been on the roads in Zurich for a little while now. With its large windscreen and covered wheels, it looks quite similar to a tram. The bus can draw power from both overhead wires and an on-board traction battery, with software to optimise the use of energy at each particular moment.

This intelligent city bus is the result of a joint project between Carrosserie Hess from Bellach in the canton of Solothurn and the ETH. ETH researchers have developed an energy management software package tailored to the vehicle’s needs for the bus manufacturer. Using algorithms, the software determines when the bus should alternate between the overhead wires and battery pack. For example, during a hill climb the most sensible choice is to drain the traction battery, because the bus can subsequently take advantage of regenerative braking on a downhill stretch to recharge the battery “for free”. According to ETH, this software can reduce energy use by up to 15 per cent and cut costs considerably.

The cooperation offers advantages for both ETH and the bus manufacturer. “We simply don’t have the resources to develop that kind of efficient energy management system on our own,” comments Martin Widmer from Carrosserie Hess in an article by Globe, the ETH magazine. This collaboration has allowed the Swiss bus manufacturer to maintain a competitive edge over rivals from other countries. For their part, ETH researchers were able to translate their theoretical expertise into concrete projects. “The project attracts students like a magnet,” said Christopher Onder, Professor at the Institute for Dynamic Systems and Control at ETH.

The smart Zurich pilot bus is the only one of its kind, though three additional bi-articulated buses based on the same technology will start operating on local routes this autumn. Martin Widmer is confident that others will soon follow in the footsteps of public transport operator Verkehrsbetriebe Zürich (VBZ). Some have in fact already expressed interest.