Volvo 7900 Articulated Hybrid will save at least 30% of fuel

A humble confession:
When the Volvo 7700 Hybrid was introduced in 2010 we were all nervous. Introducing a hybrid bus in the middle of the worst recession since the 1930:s. Still, the sales exceeded the forecasts and we were all taken by surprise. The experience and the success has given us the strength to continue the development.

When we started the planning for the 18 meter articulated hybrid bus, different alternatives were considered. One option included using the new 5.1 liter 240 Hp diesel engine with two batteries and an upgraded 150 kW electrical motor (the 7900 12 meter hybrid has a 120 kW electric motor). 

I was skeptical. Historically, I have more frequently been accused of supporting too wildly. This time however, no doubt, I argued for a stronger diesel engine in order to secure sufficient drive ability and performance.

Volvo parallell hybrid driveline

Some colleagues argued that the experience of the rightsizing of the D5 engine for the 12 meter version of the 7900 Hybrid turned out to be one of the reasons for the success. In addition, a second battery increased the energy storage by 100%, the power of the electrical machine was boosted by 15% and the torque was increased by 50%  while the weight was increased by 35% when going from 12 meters to 18 meter articulated. The concept was evaluated together with a number of selected alternatives.

Soon it turned out I was wrong. The new concept will be excellent and even preferred for at least 70% of the city bus routes in Europe. The reasons for the progress are: the highly efficient right sized diesel engine will provide a baseline for the efficiency. Further savings are realized by: the brake energy recuperation, the idle shut down at bus stops, electrification of steering servo, air compressor, climate control and the new electric doors and finally by utilizing the I-shift gear box. Together at least 30% fuel savings relative the corresponding articulated diesel bus are confirmed.

Considering that the articulated buses already have a higher efficiency per passenger the achievement is truly excellent. I expect the pay-back time to be even shorter than for the 12m version of the 7900 Hybrid. We need to come back with more detailed data on different types of routes when we are ready.

Volvo 7900 Hybrid Articulated

Volvo 7900 Articulated Hybrid is the most recent family member in our Volvo hybrid range

The articulated hybrid bus has a very high passenger capacity. The bus in the picture, with double glazed windows, 2+2+2+2 doors and three climate systems is specified for 151 passengers.

When the hybrid bus arrives at the bus stop the engine is shut down to avoid idling, this saves fuels and local emissions. As for the 12m hybrid we have secured that the bus can start from most bus stops in electric mode in order to avoid leaving an emission cloud behind.

About volvobuses

Adjunct Professor of Catalysis at Chalmers University of Technology. Lives in Gothenburg, Sweden, with my wife and three daughters born in 1991, 1994 and 1997. Is a passionate runner.
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