Volvo hybrid bus more fuel-efficient than expected
The latest version of Volvo’s hybrid bus is about 37 percent more fuel-efficient than the corresponding diesel variant. That is far better than customers and Volvo Buses’ own experts expected just a few years ago.
When Volvo Buses started field testing hybrid buses in 2007, the company calculated on a fuel saving of about 25 percent in urban operations compared with the corresponding diesel bus. When the first commercially built hybrid buses were launched two years later, their fuel consumption was about 35 percent lower. Since then the fuel consumption of new hybrid buses has dropped even more, thanks not least to lower vehicle weight and electric drive for several auxiliary systems.
“The fuel data from the 260 Volvo hybrids already in service throughout the world show that reality surpasses our calculations. At the same time we are continuing to develop the technology towards even better fuel efficiency and lower emissions,” says Edward Jobson, Environment Manager at Volvo Buses.
Fuel economy and environmental responsibility
One of Luxemburg’s largest travel and transport companies, Sales-Lentz, took delivery of its first Volvo hybrid in 2009 and now runs a total of eleven hybrids, operating both in inner-city urban traffic and in rural areas. Additional two Volvo Hybrids will be delivered in September 2012. The company maintains thorough records of its operating costs and notes that its hybrid buses more than match expectations.
“The fuel consumption of our Volvo hybrids is an average of 25.7 litres/100 kilometres, which is a very good figure. At the same time, we’re making a positive impact on the environment, which is appreciated by drivers and passengers alike,” says Jos Sales, CEO of Sales Lentz.
Electrically powered auxiliary systems
Volvo’s hybrid bus is propelled entirely electrically, is quiet and emission-free from start and up to 15-20 km/h. At higher speeds, the bus is powered by a small 4-cylinder diesel engine that can operate under optimal conditions within a narrow rev band. The energy generated during engine braking is stored in the bus’s batteries and is used to power the vehicle’s electric motor and various auxiliary systems.
The choice of gearchanging system also helps cut fuel consumption: Volvo’s hybrid bus is equipped with I-Shift, which results in far lower energy losses than with a conventional automatic transmission. When the bus is at a standstill at a bus stop or traffic light, the diesel engine shuts off and all auxiliary systems such as the climate unit, doors, power steering and so on are powered electrically.
“It is not uncommon for a city bus to spend between 30 and 40 percent of its operating time idling, so this solution not only saves fuel, it also significantly improves the local environment around the bus,” explains Edward Jobson.
Lower weight raises productivity
The latest version of Volvo’s hybrid bus weighs about 500 kg less than before. This means it can carry another seven passengers, raising the vehicle’s productivity by eight percent. This in turn means that 112 Volvo hybrid buses can carry as many passengers as 130 diesel buses can.
Strong environmental alternative
“Our experience so far shows that our hybrid solution delivers what it promises, beating our fuel economy and environmental performance expectations by a wide margin. Compared with the corresponding diesel bus, the hybrid emits 30 to 40 percent lower emissions of climate-impacting carbon dioxide and only half the nitrogen oxides and particles. What is more, the hybrid is far quieter,” says Edward Jobson.
Plug-in hybrid saves up to 60 %
While continuing to optimise the hybrid technology in today’s buses, Volvo Buses is also testing a variety of additional solutions such as a plug-in hybrid, where the bus’s batteries are recharged via the main electrical grid. With this system, fuel savings of up to 60 percent are possible.
Since Volvo Buses started building hybrid buses in 2010, the company has sold more than 650 units to customers in 18 countries. This makes Volvo the leading supplier of hybrid buses in Europe.