Freightliner's SuperTruck concept offers lessons for manufacturers
The Supertruck concept tractor-trailer was developed as part of a U.S. government project to improve fuel efficiency
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Car owners are always looking for better fuel efficiency, but they’re not alone. It’s also a major issue with tractor-trailers, since fuel is usually a trucking company’s largest operating cost.
As part of a U.S. government project involving four truck manufacturers, Freightliner has developed its SuperTruck. This concept tractor-trailer has achieved real-world testing of 19.3 L/100 km when fully loaded, about half of what a conventional truck would use.
“Seventy per cent of the freight in the U.S. is hauled by trucks, so trucking is an important part of the economy, but it consumes about 20 per cent of all fuel for road vehicles,” says Derek Rotz, manager in advanced engineering for Daimler Trucks North America, which owns Freightliner. “If a truck uses less fuel, fleets can reduce their operating costs and it’s good for the environment.”
The SuperTruck concept is a combination of technologies, some of which are already in use in production trucks, including aerodynamic styling and low-rolling-resistance tires.
Others that may be used in the future include lightweight materials, electric air conditioning, and active grille shutters that improve airflow over the nose when full engine cooling isn’t needed.
But while engineers tried as many things as possible, not all of them turned out to be viable. A technology has to cost less in the long run than the equivalent value of the fuel it will save, and also can’t be so complicated that it’s difficult to manufacture or install. The SuperTruck uses an exhaust-mounted turbine that runs off waste heat to produce electricity, but it’s too heavy and complex for real-world use.
The truck also has a gasoline-electric hybrid system that ultimately didn’t return the efficiency expected. Hybrid systems recharge their batteries with regenerative braking, which captures kinetic energy generated by the wheels when slowing down. Since these trucks primarily cruise at steady speed on the highway, there isn’t much opportunity to recharge.
“There is limited stop and go, which means less energy recovered,” Rotz says. “And it needs a lot of power to drive the vehicle, so you need a unique hybrid design for trucks and it’s difficult to leverage passenger car technology. We went into the program in 2010 and (truck) hybrids were in discussion at the time, but very little was known about them. Five years later, we know the potential but also the limitations of the system, and we feel hybrids are actually not the best solution for long-haul trucks.”
The engineers also optimized more than 2,000 of the truck’s components, gaining a fraction of fuel economy with each that adds up over the entire vehicle. The truck’s integrated aerodynamic trailer is also part of the project, and contributes about two-thirds of the SuperTruck’s overall fuel savings.
• The U.S. government’s SuperTruck program goal was a 50 per cent freight efficiency improvement, which includes fuel, distance travelled and weight carried, but Freightliner achieved a 115 per cent improvement.
• Concept vehicles like the SuperTruck allow engineers to test new technologies not just in laboratories, but in real-world scenarios including hauling loads.
• Freightliner has also introduced a self-driving concept truck, the Inspiration, currently being tested on Nevada’s highways.