Back in 2009, the US Department of Energy issued its SuperTruck Challenge. The program provided funding for truck manufacturers to design and build a prototype vehicle that was at least 50 percent more freight-efficient than a baseline 2009 truck. Daimler Trucks North America recently unveiled its response – the Freightliner SuperTruck. It goes beyond the 50 percent figure, with a claimed efficiency increase of 115 percent.
The truck was created through a collaboration between Daimler-owned companies Freightliner, Detroit Engines, Mercedes-Benz and Fuso.
Much of its increased efficiency is due to better aerodynamics. This was achieved partly through a very streamlined tractor that includes features such as adjustable ride height, rear wheel fairings, articulated side extenders that bridge the gap between tractor and trailer, and ventilation slats in the grille that close when the vehicle is traveling at highway speeds.
That streamlining proceeds back to the trailer, where side skirts channel air past the wheels and away from the underside, while rear fins keep turbulence from building up in the space behind the trailer. As a result, the SuperTruck is a claimed 54 percent more aerodynamic than the baseline truck.
A lot of emphasis was also placed on using lightweight materials, and reducing friction. This includes a tractor frame design that requires fewer crossmembers, a lighter rear suspension, and custom Michelin tires made with a rubber compound that decreases rolling resistance. Utilizing these approaches and others, a total of 700 lb (318 kg) was shaved off of the tractor.
Perhaps not surprisingly, the SuperTruck also has a hybrid diesel/electric drive system. As a means of boosting its battery power, however, it utilizes a waste heat recovery system which harvests thermal energy from the hot exhaust. The custom-designed low-friction 10.7-liter engine, meanwhile, manages an impressive 50 percent brake thermal efficiency (which was another stated goal of the SuperTruck Challenge).
Many other efficiency-boosting features were additionally incorporated. A few of these include rooftop solar panels on the trailer that can independently power its cargo-cooling system; an exhaust aftertreatment system that allows the engine to run at higher temperatures and pressures; and a GPS-based predictive system that shifts gears and adjusts speed, based on the upcoming terrain.
The 115-percent figure was arrived at based on a five-day, 312-mile (502-km) round trip route on Texas Interstate 35 between San Antonio and Dallas, at a weight of 65,000 lb (29,484-kg) GVWR (gross vehicle weight rating) and a speed of 65 mph (104 km/h). Its actual fuel efficiency on that trip was 12.2 mpg (19.3 L/100km), which is reportedly about twice what most trucks are able to attain under similar conditions.
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