Fuel cell prototype bus gets ZF’s electric drive system

British bus manufacturer Alexander Dennis Ltd (ADL) is expanding its product line, adding a double-decker model powered by a fuel cell drive. This new model is also equipped with ZF's AxTrax AVE electric drive axle to prevent local emissions.

ZF also provided additional hardware and software solutions for optimum performance. An initial prototype was impressive, operating at high efficiency during field testing, says ZF.

The successful AxTrax AVE electric portal axle product line goes from strength to strength. “We are delighted that the British manufacturer Alexander Dennis has placed its trust in the AxTrax AVE electric drive solution from ZF,” said Fredrik Staedtler, head of ZF's Commercial Vehicle Technology Division. “ZF has simplified the process of electrifying vehicle platforms for the manufacturer while making an important contribution toward keeping city center mobility solutions free from emissions.”

The AxTrax AVE will be installed in a bus with a fuel cell drive. The bus, designed by ADL, is based on its Enviro400 product line. This configuration comprises a secure system that uses hydrogen to generate electricity, which, in turn, drives two electric wheel-hub motors in the electric portal axle. As fuel cells do not utilise fossil fuels, they produce no hazardous emissions, only steam.

ADL spent two years developing this hydrogen-driven double-decker bus with ZF selected as a partner right from the start. During field testing, the prototype operated along real bus routes in several cities throughout the United Kingdom. The Enviro400 design impressed everyone with its outstanding efficiency.

In addition to the AxTrax AVE, ZF also provided the inverter, the EST 54 electronic control unit and the appropriate control software. In this complete system, the company optimally aligned performance, efficiency and the service life of the drive. Moreover, this system solution helped reduce the test and homologation costs for ADL.

The British manufacturer has already presented the prototype of the new fuel cell double-decker to the public as well as several fleet operators.

Efficient and proven
The AxTrax AVE was introduced for the first time in 2012 and has been successfully deployed around the world ever since. The electric drive axle can be used in a wide array of possible applications as it can not only be operated in the mentioned fuel cell configuration, but also as a hybrid or purely electrically with lithium-ion batteries. In addition to the striking drive performance – totaling 250 kW up to a maximum axle load of 13,000 kilograms – the compact design is also appealing.

Since neither a conventional unit nor a universally jointed shaft is necessary for transmitting power, manufacturers now have more freedom to design the passenger area the way they want. They can add seating and standing room, for example, or provide for step-less entry and exit or a completely flat passageway.