Bochum, Germany

Braking brings progress

In Germany’s Ruhr region, 11 city buses equipped with Voith hybrid drive systems have been in operation since the summer of 2011. They help regional transportation to save fuel, while also playing an active role in climate protection.

When Michael Mutzenbach steps on the brake pedal, one of the things he is doing, besides decelerating, is helping the environment. For the last 12 months, the 53-year-old has been driving buses for the Bochum-Gelsenkirchener Strassenbahnen AG (BOGESTRA) transportation company, which are equipped with an advanced parallel hybrid drive system from Voith. “We use up to 15% less fuel on our routes,” he explains.

The principle is actually quite simple. Whenever the driver slows the bus by braking, the energy that is released is stored in devices known as “supercaps” located on the vehicle’s roof. These high-performance capacitors are charged by the braking energy and, in contrast to storage batteries, they are not subject to wear and tear. When the bus accelerates again, it uses this energy to reach a speed of around 15 km/h, before the diesel engine automatically kicks in to to take over.

“We use up to 15% less fuel on our routes.”

Michael Mutzenbach,
Bochum-Gelsenkirchener Straßenbahnen AG

In the summer of 2011, BOGESTRA placed the 11 buses complete with Voith drive systems into service. After successfully completing initial test runs on selected routes, the vehicles, from Polish manufacturer Solaris, are now operating on many routes. The transportation company is more than satisfied with its experiences to date. “We’ve not had a single malfunction so far,” reports Jörg Filter, who is head of the infrastructure and vehicles division at BOGESTRA. In fact, thanks to the supercaps, the diesel engine is protected somewhat, while the capacitors themselves are entirely maintenance-free. To top it off, particulate emmission is reduced by up to 90% compared to conventional diesel vehicles, carbon dioxide emissions are cut by 30% and the discharge of nitrogen oxides is lowered by almost 40%.

“It was clear to us that if we wanted to test hybrid technology on a large scale, it would be best to do it with Voith.”

Jörg Filter,
Bochum-Gelsenkirchener Straßenbahnen AG

The decision was quickly made, when, in 2009, Voith proposed entering into a collaboration on hybrid technology with one of the biggest transportation companies in the Ruhr. “We really profited from our long-term relationship with BOGESTRA,” says Helmut Zimmermann, project manager at Voith. Filter adds, “It was clear to us that if we wanted to test hybrid technology on a large scale, it would be best to do it with Voith.”

The project was carried out as part of a program of public development schemes. The state of North Rhine-Westphalia subsidized eight of the vehicles and Germany’s Federal Ministry of Transportation provided funding for the other three. Jörg Filter is convinced that without such development funding, hybrid drives for commercial vehicles would not currently be possible, and he is aware that it may take a few more years until the systems really catch on. “Nevertheless, hybrid drives are a transitory technology for which it’s critical to collect as much information as early as possible. In that way, we will be able to safeguard Voith’s leadership in innovation,” he says.

Of course, image plays a significant role, too. Almost every day, driver Michael Mutzenbach is asked by passengers about his bus with the eye-catching green design. A display behind the driver’s seat provides passengers with a “live” display of the braking and accelerating energy flowing through the bus at any given time. They also notice that the ride comfort is different – the hybrid buses run smoother and more silently. The fact that he’s sitting at the wheel of a high-tech machine also increases Mutzenbach’s driving pleasure. Or, as he puts it simply, “I just like driving these things.”

The green buses represent environmental awareness. The new technology significantly decreases particulate emissions and reduces carbon dioxide and nitrogen oxide pollution by at least one third.

Passengers enjoy the new ride comfort and feel good about taking such a technologically advanced bus. The hybrid drive is also a sound investment in a positive future for the next generation.