The all-out industry effort to create a fuel-efficient Super Truck
By Paul Abelson
What’s all this talk about a Super Truck, and what makes it so super? When the government cash awards hit the headlines earlier this year, more and more drivers started asking those questions. Well, here’s the story in a nutshell.
The Department of Energy awarded money for research to improve fuel efficiency in real-world, over-the-road (OTR) operations. The improvements will have to be demonstrated by trucking fleets delivering real loads from real shippers to real receivers.
The goal: to improve fuel economy by 50 percent by 2015.
The history of fuel economy
When I entered the trucking industry in the late ‘70s, fuel cost less than 50 cents a gallon. Rates were regulated by the now- defunct Interstate Commerce Commission, so fleets and owner-operators alike were not that concerned that trucks were getting about 3 to 3.5 miles per gallon of diesel. In 1982, along came deregulation, bringing us a 5-cent-a-gallon additional fuel tax, uniform weight limits and unlimited tractor size across the country. Fuel prices were rising and fuel economy gained in importance.
Even the best-run fleets struggled in the ’80s and early ’90s to improve fuel economy. Aerodynamics came into their own. Soon full aerodynamic shrouds yielded a whopping 13 percent improvement in fuel economy. It was measured by the then-new set of objective tests to measure fuel consumption, the SAE/TMC Recommended Practices (SAE J1321 and TMC RP1102). Soon after, electronic engine controls, the first steps to exhaust emissions reductions, helped improve fuel economy to 5 mpg. Even owner-operators who did not have speed-limited trucks were getting almost that. During the ’90s, fuel economy for fleets improved more than 40 percent and about 60 percent for owner-operators.
Today, I regularly hear from owner-operators who are achieving close to 7 mpg, and many exceed that mark. The baseline today is between 6.5 and 7.0 mpg with van-type trailers and streamlined tractors. We’re there because just about everything on or around our trucks has gotten more efficient. The Super Truck program uses $115 million from the American Recovery and Reinvestment Act, also known as the Stimulus Bill, to develop and demonstrate the 50 percent improvement. That would take our 7 mpg trucks to 10.5 mpg in real-world service. The program is also “expected to create approximately 500 new jobs,” according to U.S. Energy Secretary Steven Chu.
In view of the advances made already, is such a goal really achievable? The question reminds me of an urban legend (not really so) that in 1899, the director of the U.S. Patent Office declared, “Everything that can be invented has been invented.”
Of course, that was before the advent of the airplane, satellites, television and computers.
The next steps
So where will these fuel economy improvements come from? While tractor aerodynamics have come a long way in the past one and a half decades, trailer aerodynamics are in their infancy. Since the ’80s, diesel engine efficiency has improved from about 33 percent to more than 40 percent, but there is still a lot of wasted energy to be captured. Tire makers are working on structures and compounds that offer greater fuel efficiencies. Transmission makers are working to optimize engine torque for better overall fuel economy. Even electrical systems can reduce fuel use with capacitor starting systems and electrically driven accessories.
Since so many varied technologies contribute to increased overall efficiency, several teams of manufacturers will partner to develop improved tractor-trailer combinations. Peterbilt will be teamed with Cummins, Delphi, Eaton, Modine, Bridgestone and USXpress Enterprises. International is teamed with Wabash National, Advanced Transit Dynamics (ATD), an unspecified tire maker and fleet operators Safeway and Swift Transportation. Daimler Trucks (Freightliner, Western Star and Detroit Diesel) will be working on aerodynamics and improved engine efficiency.
Idle reduction will factor into fuel savings, so the Peterbilt team will be working on hydrogen fuel cells for auxiliary power. Even though auxiliary power units (APUs) and fuel-fired heaters use as little as 10 percent of what an idling engine does, they still contribute to fuel consumption and produce a carbon footprint. Hydrogen fuel cells generate electricity with no carbon in their exhaust, only water vapor.
Freightliner will work on hybridization and improved tractor aerodynamics. Detroit Diesel will work on downsizing engines, electrifying auxiliary systems and recovering waste heat. A smaller engine producing the needed amount of power will burn less fuel than a larger engine with the same ratings.
Power output per liter or cubic inch of displacement can be improved by retaining more heat energy to do useable work. Today, about 40 percent of diesel’s energy goes to driving the truck. The rest goes into the cooling system to be dispersed through the radiator or out the stacks as hot exhaust. Last year, Detroit Diesel was given the Truck Writers of North America Technical Achievement Award for 2008 for applying turbo compounding to their new series of engines. It uses a second turbine to capture energy still in the exhaust after it leaves the primary turbocharger. It turns a shaft connected to the engine to utilize power that would otherwise be lost through the exhaust.
Other strategies to direct heat to do useful work include insulating manifolds and exhaust pipes and experimenting with heat-to-electricity converters.
Freightliner has its own tractor-only wind tunnel, enabling it to refine tractor shapes. Navistar will work on tractor-trailer aerodynamics, as well as efficiency in their MaxxForce engines. Other technologies to be looked at with their partner, Argonne National Labs, will be idle reduction, low rolling resistance tires and hybridization.
Additional fuel savings can be achieved by removing belt and gear driven accessories such as cooling fans, air conditioner and air system compressors and power steering pumps from the engine. Driving them electrically only when needed, and locating them near where they function will cut parasitic loads on the engine significantly. Eaton’s automated transmissions can be computer controlled to respond correctly to the demands placed on the truck in the most fuel-efficient way. Gear selection and time in gear can be optimized.
Navistar is working with the Lawrence Livermore National Laboratory and the NASA Ames Center wind tunnel, the world’s largest wind tunnel. They will be testing both proposed and currently available aerodynamic devices and trailers. ATD makes folding extended tail structures for trailers. Navistar is also developing a device to adjust the tractor-trailer gap according to truck speed and load so the gap is always as small as possible.
In more than 30 years working with and around trucks, I’ve discovered that things can always be improved, and if they can be, they will be. The OTR segment, while just a small fraction of vehicles on the road, account for nearly 20 percent of fuel used in the U.S., according to DOE. Improving fuel efficiency by 50 percent can save a huge amount of diesel, lowering costs for truckers and reducing our petroleum imports.