There's no magic bullet yet for turning construction truck fleets green. While LNG and diesel-electric hybrid powertrains may eventually be offered on construction trucks, right now the best way to turn these workhorses green is by carefully considering spec'ing choices of everything from the diesel engine to the tires.
The goal should be to squeeze every ounce of fuel efficiency out of the truck while all performance criteria are fully met. Fleets would be wise to consult with truck dealers to get the most out of their powertrains. According to Robert Johnson, director of fleet relations liaison for the National Truck Equipment Assn. (NTEA), a properly spec'd powertrain will ensure a truck's engine operates within its peak efficiency power band at all times. “Optimizing the powertrain for peak fuel efficiency is not as complex is it may seem. Truck dealers are equipped with computer software programs that can match engine ratings, transmission gear ratios and final drive [rear end] gear ratios to achieve the desired performance,” he says.
Providing auxiliary power generation is another fuel-saving strategy advocated by Johnson. “If an application requires a limited amount of hydraulic or electric power, a small auxiliary engine generator set may provide sufficient energy to eliminate the need for idling the truck engine for extended periods of time,” he observes. “If electricity is only needed for relatively short periods of time, a static inverter may do the trick.”
A wide avenue to pursue for maximum greenness is getting as much weight out of the vehicle as possible. The frame, suspension and wheels are big areas to key in on for weight savings. “Modern batteries and starters are much more efficient than they used to be, yet some fleet managers still spec four cranking batteries when three would be adequate,” says Johnson. “The same idea applies to bypass oil filters and auxiliary oil coolers. Newer engine cooling systems and oil filters are more efficient than those of even a few years ago. Eliminating an unneeded bypass oil filter will save close to 100 lbs. Stop to think it through before including a potentially outdated spec.” He says an oversized fuel tank will also add unnecessary weight. “Unless the vehicle will be used in an area where fuel isn't easily accessible, why carry around three or four days' worth of fuel?” asks Johnson. A gallon of diesel weighs 7 lbs. Factor in the weight of the fuel tank, and 50 extra gallons of fuel will amount to hauling up to 400 lbs. extra.
Along with considering aerodynamic treatments that will save fuel during highway operations but also make sense given the ground clearance needed for on/off-road trucks, Johnson suggests doing all possible to keep the truck's exterior “clean” of wind-catchers. “Anything that interrupts the smooth flow of air over and around the vehicle will cause drag. Some of the worst offenders are items such as frame-mounted battery boxes, bypass oil filters, and traditional vertical exhaust stacks with perforated stainless steel heat shields,” he advises.
It should go without saying that low-rolling resistance tires suitable for severe service should be investigated as well. Johnson also recommends not overlook installing oil bath wheel seals on non-drive axles, using synthetic fluids wherever possible and installing free-flow air filters to help increase fuel efficiency.
