LAS VEGAS – What weighs 80,000 pounds fully-loaded, has eighteen wheels, but gets fuel economy of just 19 L/100 km? Cue the music: it’s SuperTruck!
Unveiled by Freightliner earlier this year, the SuperTruck is a concept vehicle intended to test and develop fuel-efficient technologies that could be used on Class 8 tractor-trailers. And I got an up-close-and-personal with it, including a ride that probably chewed up less fuel than a heavy-duty pickup truck would have used.
(Disclosure: Travel, accommodation and meals were provided to the writer by the manufacturer.)
It’s part of a program sponsored by the U.S. Department of Energy, a $187 million (U.S.) investment in nine projects intended to improve fuel consumption, both in passenger and commercial vehicles. In 2010, it was announced that Daimler Trucks North America (Freightliner’s parent company), Navistar, and Cummins would work on the heavy-duty projects.
The companies had to match the government funding, and Daimler received $40 million to work with its sister company Detroit Diesel on the SuperTruck. Cummins would work with Peterbilt on a similar concept, along with a new clean diesel engine, while Navistar would explore fuel-saving technologies. So, in essence, I was riding along a Nevada highway in a truck that might be worth upwards of $80 million dollars. And yes, I wiped my feet first!
But you won’t be sharing the road with a fleet of Freightliner SuperTrucks, and never will. For every revolutionary new technology that makes it to market, whether it’s in a subcompact car or an eighteen-wheeler, there are dozens or more that never get off the ground. The goal of the SuperTruck program was to identify, develop, and test technologies, not just to see if they would work, but if they could be feasible for production vehicles. Sometimes, even if a technology works really well, its cost or complexity outweighs its benefits. At that point, all the engineers can say is that they tried.
“Seventy per cent of the freight in the U.S. is hauled by truck, so trucking is an important part of the economy, but it consumes about 20 per cent of all fuel for all road vehicles,” says Derek Rotz, Daimler Trucks’ manager for advanced engineering. “Per year, a typical long-haul truck would consume maybe 15,000 gallons (56,781 litres) of diesel, so a one per cent fuel savings at $4.00 per gallon would be $600. The cost of the system must be less than that.”
The SuperTruck was tested over 1,173 kilometres on public roads, and averaged just 12.2 mpg (19 L/100 km). By comparison, a conventional tractor-trailer averages about 39 L/100 km.
In freight efficiency, which measures the miles per gallon per ton of freight, the Freightliner SuperTruck achieved a 115 per cent improvement over the baseline 2009 Freightliner Cascadia, a conventional Class 8 truck. The DOE had set a target of a 50 per cent improvement. (The Cummins/Peterbilt truck has achieved a 70 per cent improvement over its baseline truck.)
So how does the SuperTruck make its magic? It’s a complicated stew of technologies, some of which may only contribute a small improvement but add up in the big picture. Some of them, including trailer skirts, low-rolling-resistance tires, more fuel-efficient axle ratios, and predictive shifting of its automatic transmission are not only feasible, but are in use by Freightliner and other truck manufacturers on their products.
The SuperTruck’s cab is lined with lightweight materials
Some that may be available in the future include grille shutters that open and close, fairings over the tractor’s drive wheels, lightweight materials, no gap between the truck and trailer, aerodynamic trailer devices, improved tire treads, and mirror cameras, which display what they see on screens inside the cab and allow for smaller, more aerodynamic exterior mirrors or possibly no mirrors at all.
As for what won’t work, the SuperTruck has some pretty way-out features, starting with its diesel-hybrid powertrain. Yes, this hauler is a hybrid, but it’s not an overgrown Prius. “It takes a lot of power to drive the vehicle and needs a lot of power to brake the vehicle, which means you have to have a unique hybrid design for trucks,” Rotz says. “It’s difficult to leverage passenger-car technology.”
The main issue is that hybrids recharge their batteries using regenerative braking power, but these trucks don’t slow down enough on long hauls. As well, there were significant efficiency losses in transferring the energy from the mechanical regenerative braking into electricity, then into chemical for storage in the battery, and then back into electricity to power the truck from the battery.
“The hybrid system saved less fuel than we expected, primarily because there was limited stop-and go that is usually a benefit for hybrids,” Rotz says. “We went into the program in 2010 and (truck) hybrids were the discussion at the time, but very little was known about them. Five years later, we know the potential but also the limitation of the system, and we feel hybrids are not the best solutions for long-haul trucks.”
Even more fascinating is the SuperTruck’s waste heat recovery system. It boils a fluid, using heat from the exhaust, and uses the resulting steam to spin a turbine that feeds power back into the driveline. Unfortunately, while it’s a great way to recycle heat energy that otherwise is simply lost to the outside air, it’s too complex for a production vehicle. On top of that, weight is the enemy of fuel economy, and the system doesn’t return enough benefit for how much extra it adds to the truck.
Designing a fuel-efficient vehicle is always more than just tweaks to the engine, especially on something this big. While the SuperTruck itself will never go into production, it and concepts like it are essential keys to moving truck technology forward.
“For a truck to reduce its fuel use means fleets can reduce their operating costs and be more profitable,” Rotz says. “Plus it reduces CO2 emissions, which is good for the environment. It’s a win-win.”