WASHINGTON, D.C. The term “hybrid vehicle” typically brings to mind small, oddly shaped passenger cars like Toyota’s Prius— not a beefy 64,000-lb. truck.
Yet that’s what the Mack Trucks operation of Sweden’s Volvo Group is delivering to the U.S. Air Force— a prototype Mack Granite dump truck that sports an electric motor paired with a 365 hp. diesel engine. It is equipped with what the OEM calls “ultra-capacitors,” instead of massive batteries for short-term energy storage, helping it boost fuel economy anywhere from 30% to 35%. By burning less fuel, there are emissions benefits as well.
It’s the latest in a line of six heavy-duty hybrid truck models Volvo and Mack have built for the Air Force as part of a $6.8-million contract. Though hybrids vehicles of this size and scope are very expensive compared to their diesel-only brethren, both the OEMs sees great potential in the commercial market if government incentives can spur enough initial purchases.
“There are a lot of customer benefits to heavy-duty hybrids,” Paul Vikner, president & CEO of Mack Trucks explained at a special event held here at the Swedish embassy.
“You’re also looking at having an auxiliary power source that, for refuse and other vocational operations, may eliminate the need for a PTO [power take off],” Vikner said. “And finally, noise: hybrids produce significantly less noise than diesel-only trucks. For operators in residential and other tight urban areas, that can be a big advantage.”
However, Vikner is well aware of the cost concerns customers have about hybrids. “The initial cost of the technology is the biggest,” he said. “There’s also the long-term reliability of hybrids; these are concerns we’re working on now.”
The Mack hybrid truck is slated for full field tests in 2008, with full production scheduled in 2009.
Volvo Group’s CEO Leif Johansson stressed that higher production volumes are key to lowering the sticker price. Right now, the heavy-duty hybrids, which aren’t equipped with ’07 emissions reduction technology, are more expensive even than their ’07 diesel-only counterparts.
"The cost calculation for these vehicles is also very application-dependent,” Johansson told FleetOwner. “The more stops and starts a vehicle has, the more savings a hybrid generates. We think a hybrid in such an application— such as a refuse vehicle— could have a one- to three-year payback. That is what would make this technology commercially viable.”
Guy Rini, Mack’s director of advanced propulsion systems, added that by using short-term energy storage systems like ultra-capacitors instead of heavy batteries makes the heavy-duty hybrids less expensive and cheaper to operate.
“We’re using electricity just to launch the vehicle, to get it up to 4.5 miles per hour at which point the diesel engine comes on,” he explained to FleetOwner. “You’re getting the truck up to a speed where it’s much more efficient to then activate the diesel engine. You’re only talking about having enough energy just to get it started, to go from one trashcan to the next, for example. And look at the fuel efficiency we’re talking about here. In an industry where a 3% fuel savings is a big deal, we’re looking at over 30% and more in many cases.”
Based on Volvo’s integrated starter alternator and motor (I-SAM) hybrid developed in Europe, Mack’s Granite hybrid also offers another advancement: a lighter hybrid so that payload capacity doesn’t pale compare to its diesel-only counterpart, said Sten-Ake Aronsson, senior vp for Volvo Powertrain.
“The electric motor on this truck generates up to 160 hp— meaning you can reduce the size of the diesel engine,” he said. “A smaller diesel means smaller packaging and less weight. Also, you get full torque capacity from the electric motor even at zero miles per hour. The technology we’re using on this platform has been well established for decades,” he added
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