Volvo released the 7700 Hybrid bus, saying that with up to 30% lower fuel consumption and hybrid components from Volvo, bus operators can earn a payback on the extra cost in five to seven years. The first buses will be delivered to customers during 2009, while mass production begins in early 2010.
The demand for a substantial reduction in fuel consumption within the transportation industry is growing increasingly stronger and for many reasons. One of the most important is the need to reduce CO2 emissions that affect the climate. Another is the extremely high price of oil and expected increase in the foreseeable future.
The lower fuel consumption of the 7700 reduces the emission of the greenhouse gas CO2 by up to 30%. The discharge of particles and nitrous oxides declines by up to 40-50% compared with the diesel version.
Volvo has chosen to develop a parallel hybrid with a technology that will be used in buses as well as trucks and construction equipment within the Group. Long term, this will involve larger volumes, which reduces costs.
Volvo’s hybrid concept is called I-SAM and comprises a combined start motor, electric motor, generator and an electronic control unit. I-SAM works together with a diesel engine and Volvo’s acclaimed I-shift gearbox. In addition, a lithium-ion battery is used that is charged during braking via the electric motor/generator. This battery then provides energy to the electric motor for drive power. As a parallel hybrid, the bus can be powered by the electric motor or the diesel engine independently and well as by both engines simultaneously. As a result, the bus could be equipped with a smaller, 5-liter diesel engine compared with the 9-liter engine in the diesel version of the Volvo 7700. The bus’s performance is enhanced, but fuel consumption is reduced.
“Another major benefit with Volvo’s hybrid technology is that the diesel engine will be turned off at bus stops and traffic lights,” says Håkan Karlsson, President of Volvo Bus Corporation. “The bus starts moving driven by the electric motor and when the bus reaches 15-20 kph, the diesel engine starts up automatically.”
A significant reason for the fuel savings being so large as up to 30% in Volvo’s hybrid bus is that all hybrid components are developed by Volvo.
“A common approach earlier was that bus manufacturers purchased hybrid components externally and attempted to adapt them to their own bus, but this is difficult,” says Karlsson. “Since we developed the components internally, we have been able to optimize the bus’s fuel consumption fully. At the same time we could ensure very high reliability.”
The bus weights only 100 kilograms more than a diesel version. As a result of better weight distribution, it can carry up to seven more passengers than its diesel counterpart.
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