Hybrid trucks on the way

TEXT: PER-OLA KNUTAS

Transport volumes are increasing worldwide at the same time as environmental regulations and concerns about carbon dioxide emissions are mounting. Reversing this trend, which is necessary from a sustainable point of view, is a tough challenge for the transport industry as well as for the vehicle manufacturers. Hybrid vehicles will be an important part of the answer.

Tow types of hybrid technology

The two main types of hybrid technology, series hybrid and parallel hybrid, are in the pipeline for heavy vehicles and Scania is developing both types.

Series hybrids are most suitable for city buses and distribution vehicles and are advantageous from a vehicle layout standpoint. The combustion engine can be placed anywhere in the vehicle. The powertrain components are only connected to each other, which means that there is great freedom of design.

Parallel hybrids can be integrated in a normal powertrain. In such a hybrid, the electric motor and the combustion engine can either propel the vehicle separately or simultaneously. 

Recover and store energy

Both hybrid technologies have in common that they recover and store energy generated when the driver applies the brakes, most effectively in stop-and-go traffic where the driver must brake and accelerate frequently, such as in an urban environment or in curvy, hilly terrain.

“Our new hybrid buses, which will begin field testing in scheduled service in Stockholm during 2008, get at least 25 percent of their energy from braking. In addition, the ethanol engine reduces carbon dioxide emissions by up to 90 percent,” says Lars Stenqvist, responsible for hybrid technology at Scania.

Different applications

He views the spread of hybrid technology as rings on water. The first ring is city buses and refuse trucks. The next is distribution trucks and intercity buses. The last ring is likely to be long-haul trucks, where some energy can be stored to drive auxiliary systems like parking heating and cooling systems.

“After 20 years of hybrid research using various concepts, Scania recently made a breakthrough with robust hybrid powertrains in our concept buses,” says Stenqvist. “The components we need to build a powertrain capable of lasting the service life of the vehicle are coming onto the market. From 2008 we will gradually broaden our scope to include large-scale field testing in real-life operation. In five years’ time, robust hybrid powertrains with engines running on renewable fuels will be part of our normal offer.

Pay extra for hybrid powertrains

“Operators will be prepared to pay extra for hybrid technology if they know it will pay off as a normal vehicle,” he adds.

During his most recent visit to tram-intensive Amsterdam, Stenqvist presented his latest idea to hauliers and industry representatives: Why not develop a distribution truck version of Scania’s series-hybrid bus, with large doors on the sides, as a flexible alternative to the freight-carrying trams used in the city today?

“I got good response to the idea,” he says. “Environmental concern forces us all to think in new ways.”

Hybrid facts

• Hybrid technology involves recovering vehicle braking energy and storing it in a storage module (supercapacitors or batteries).

• The vehicle brakes with the help of a generator similar to the dynamo that powers bicycle lights.

• A city bus may derive at least 25 percent of its energy supply from recovered braking energy, which would otherwise simply be wasted.

• The generator doubles as a motor that helps propеl the vehicle.