Navistar's SuperTruck achieved a freight efficiency improvement of 104% compared to the DOE’s control vehicle, 50.5% brake thermal efficiency and it ran the test course at 13 mpg.  -  Photo: Jim Park

Navistar's SuperTruck achieved a freight efficiency improvement of 104% compared to the DOE’s control vehicle, 50.5% brake thermal efficiency and it ran the test course at 13 mpg.

Photo: Jim Park

Later this year we’ll begin hearing much more about the U.S. Department of Energy’s SuperTruck II program. It wrapped up officially late 2021 with four of the five teams essentially finished their work. The fifth team, Navistar, got a late start and was substantially delayed by the COVID-19 pandemic. The other four teams, Daimler, Cummins/Peterbilt, Paccar (Kenworth) and Volvo are expected to report their findings sometime in 2022.

The SuperTruck program was established by the DOE’s Office of Energy Efficiency and Renewable Energy in 2009. The goal of the first project was to improve heavy-duty truck freight efficiency by 50% over a baseline 2009-model-year truck. SuperTruck directed hundreds of millions of dollars toward research and development of technologies that would improve heavy truck efficiency, such as better aerodynamic equipment, lighter weight tractors and trailers, more thermally efficient engines, low-rolling-resistance tires, and technologies like turbo compounding and waste heat recovery and more.

Four teams participated in SuperTruck I: Daimler Trucks, Volvo Trucks, Navistar and a joint effort involving Cummins and Peterbilt. Each of the tractor OEM teams partnered with a trailer manufacturer to produce a trailer optimized for fuel efficiency.

The DOE grants were matched by the participating teams, which was a stroke of genius, according Rick Mihelic, the director of emerging technologies studies at the North American Council for Freight Efficiency (NACFE). He was also directly involved in the development of the aerodynamic systems on the Peterbilt/Cummins team for SuperTruck I.

“It was a 50/50 cost share between the OEMs and the Department of Energy, which I thought was a brilliant way to ensure technology that was developed under SuperTruck would actually make it into the marketplace,” he says.

Daimler's SuperTruck achieved 12.2 mpg along with a 115% freight efficiency improvement and hit 50.2% brake thermal efficiency for the engine.  -  Photo: Jim Park

Daimler's SuperTruck achieved 12.2 mpg along with a 115% freight efficiency improvement and hit 50.2% brake thermal efficiency for the engine.

Photo: Jim Park

Not all of what emerged from SuperTruck I made it into production — or ever will — but the project helped OEMs and fleets determine what was viable and what would remain pipe dreams. By the time SuperTruck I wrapped up in 2015, the agency had identified 26 different technologies with the potential to succeed in the market within two to four years (2017-2019). An additional dozen technologies were pegged as potentially viable with five to ten years (2020-2025).

SuperTruck I technologies that have already been commercialized include downspeeding, intelligent torque management, neutral shifting on downgrades, predictive gear shifting, reduced rolling resistance tire compounds and designs, predictive GPS-based cruise control, trailer aerodynamics (side skirts, boat tails, gap fairings), lighter viscosity lubricants, and more.  

Technologies identified at the end of SuperTruck I as longer term, i.e., would be just now starting to come to market, include improved combustion technologies (piston bowl designs and materials), advanced aerodynamics (active aero such as grille shutters and tractor-trailer gap reduction), battery-based idle reduction systems, waste heat recovery (turbo compounding), electrified engine components (compressors, coolant pumps, fans, etc.), cameras replacing mirrors, solar energy harvesting, and more.

“Back in 2009, the OEM thought the goal of increasing freight efficiency by 50% would be a very challenging target,” Mihelic says. “In the end, everyone greatly exceeded that target.”

The Cummins/Peterbilt SuperTruck turned 10.7 mpg on the official test run. It demonstrated a 75 percent increase in fuel economy, a 43 percent reduction in greenhouse gas emissions and a 86 percent gain in freight efficiency.  -  Photo: Jim Park

The Cummins/Peterbilt SuperTruck turned 10.7 mpg on the official test run. It demonstrated a 75 percent increase in fuel economy, a 43 percent reduction in greenhouse gas emissions and a 86 percent gain in freight efficiency.

Photo: Jim Park

Actual fuel economy (which wasn’t really the goal of the project) results reported by each of the teams exceeded 10 mpg on the official test run. Cummins/Peterbilt reported 10.7, Daimler and Volvo both topped 12 mpg, and Navistar checked in with 13 mpg. Back in 2009, even the best trucks on the highway were averaging only six or seven miles per gallon. That was an extraordinary jump in slightly more than a decade. We owe much of those gains to technology and vehicle designs developed under the first SuperTruck program.

The Right Catalyst at the Right Time

Who could forget the mess this industry was in back in 2009? The industry was a year into what would be a devastating recession, and still reeling from the EPA 2007 emissions regulations that saw the introduction of diesel particulate filters and massive reductions in fuel economy. OEMs had more on their minds than developing exotic fuel saving technologies, and fleets were in survival mode. At the time, practically no one was even remotely interested in new fuel-saving technologies.

OEMs, though, still had lots of science projects on the go which were overshadowed by the push to meet EPA 2007. So, when DOE came around with scads of cash to bring these projects to life, the OEMs were well prepared.

“At the time, there were a lot of things on the shelf that had not yet been put into production,” NACFE's Mihelic says. “There wasn’t much money going into [research and development] in 2009, so the DOE’s timing was great. It allowed OEMs to focus on aerodynamic research and to look really closely at real-world duty cycles, which at that time were not well understood. SuperTruck gave [OEMs] the opportunity to look at tractor-trailers as a complete system, which was something fairly new at the time.”

Volvo Trucks’ SuperTruck achieved more than 12 mpg during the test run, and demonstrated an 88% improvement in freight efficiency and a 70% improvement in fuel efficiency.  -  Photo: Jim Park

Volvo Trucks’ SuperTruck achieved more than 12 mpg during the test run, and demonstrated an 88% improvement in freight efficiency and a 70% improvement in fuel efficiency.

Photo: Jim Park

For obvious reasons, tractor makers get credit for work done to tractor systems while trailer manufacturers get credit for enhancements to trailers. SuperTruck gave truck and trailer manufacturers a unique opportunity to collaborate on the whole vehicle. The results upended thinking on tractor aero systems.

Dean Opperman, who, at the time, was the chief engineer for advanced vehicles and the SuperTruck group at Navistar said his team engineered the aerodynamic design from back to front, starting with the trailer.

"We are pretty well tapped today [2017] on what we can do with the tractor alone until we clean up the trailer," he said. "Once we did the trailer, speaking in relative numbers, a 2 to 3% improvement on the tractor became an 8 to 10% improvement because of the overall reduction in drag on the rear of the trailer."

Even seemingly small improvements, like rounding the leading edge of the trailer underride guards, made a difference.  -  Photo: Jim Park

Even seemingly small improvements, like rounding the leading edge of the trailer underride guards, made a difference.

Photo: Jim Park

Fine tuning tractor and trailer aerodynamics together would produce a reduction in drag, but currently no tractor OEM owns a trailer building business. Even if one did, trying to align, for example, Daimler-built tractors with Daimler-built trailers in the real world would be logistically nearly impossible. However, current research into improving battery-electric vehicle range to make the absolute most of a very limited energy supply could turn toward married tractor-trailer units in cases where it is logistically feasible such as private fleets with dedicated tractors and trailers.

Hyundai could upend that thinking later this year, when it’s expected to bring a hydrogen fuel-cell powered tractor-trailer to North America. That would make Hyundai the first OEM to have the same badge on the power unit and the trailer on this side of either pond.

Success Stories from SuperTruck I

The SuperTruck I projects demonstrated what was possible. The next step was turning the possible into the practical.

After seven years of tinkering and toying with existing ideas and some revolutionary new ones, OEMs came away a whole new menu of options to offer energy-conscious customers. During the 2016 to 2020 timeframe, all the OEMs were looking at what their next model upgrades were going to be, and they used SuperTruck as a proving ground.

“Daimler and Paccar both brought to market new models that be much more aerodynamically efficient during that period, and most of that was based on R&D that came directly from SuperTruck,” Mihelic says.

Here’s an abbreviated list of some of the advanced technology that SuperTruck proved commercially viable since then and up to the present day:

  • Advanced Aero: The most obvious development in each case was the aerodynamic work. All the OEMs went long on aero, and why not? It's an easy target. The closer each could get to the ideal aerodynamic shape, i.e., something similar to a rain drop, the greater the gains were. We saw tighter close-out around wheels, tractor under-body fairings, mirrors replaced with cameras and changes to the width and slop of tractor hoods. These and other development can be found on current model trucks.

Tightly closed wheel wells were tried during the SuperTruck I project and med it into production a few years later.  -  Photo: Jim Park

Tightly closed wheel wells were tried during the SuperTruck I project and med it into production a few years later.

Photo: Jim Park

  • Trailer aero was a different story. All the participants developed full-height, full-length side skirts, highly sculpted nose pieces and additional airflow modifiers for the rear of the trailer. Because of the potential for body damage resulting from day-to-day use of such designs, fleets would never accept the maintenance problems associated with that sort of side skirt. Some of today's newer skirts, however, are taller than previous versions, suggesting fleets seem to be compromising between aero improvements and a slightly increased maintenance burden.
  • Smaller, lighter engines: With advanced aero treatments, low rolling resistance tires and other friction-reducing technologies, the SuperTruck engineers found they needed only 100 horsepower to maintain 65 mph on flat ground. That’s about a third of the horsepower required to keep a non-aero classic-styled truck pushing through the wind. Daimler and Volvo both used 11-liter engines in their trucks. Navistar used a 13-liter and the Cummins/Peterbilt truck had a 15-liter engine.
  • All the engines were significantly downsped. The high-torque, mid-horsepower output proved ideal for fleets in truckload applications where typical gross vehicle weights seldom exceed 70,000 pounds (31,750 kg).

    Daimler developed a 10.7-L engine platform specifically for SuperTruck, using hybridization, a waste heat recovery system and more. The intent was to meet or exceed the 50% brake thermal efficiency target set by DOE. With the installed technology, it succeeded, but the engine is not yet commercially viable.

    Since SuperTruck I, Volvo has made significant inroads with its D11 engine and fleet users report very satisfactory performance in suitable applications.
  • Hotel loads: SuperTruck opened new windows of opportunity into the off-duty life of trucks, and the challenges faced by drivers in maintaining comfortable living environment. Solutions revealed by SuperTruck I include the use of lithium-ion batteries for faster charging and longer discharge cycles, super-capacitors rather than lead-acid batteries for starting, and solar panels for adding charging capacity.

    Some work was also done to improve cab insulation for better thermal management of the cab environment without added strain on the HVAC system. All of these technologies are currently available, though some remain a little pricy for some fleets.
  • Powertrain management: Adaptive and predictive cruise control systems are perhaps two of the most obvious enhancements to emerge from SuperTruck I. As is always the case, the systems have been improved upon since 2016 and are now offered in some form or another by all OEMs.

    Closer engine transmission integration was already underway when SuperTruck launched, but additional refinements emerged, including downspeeding, torque management, idle coasting, and more.

    There was a huge amount of work done on optimizing engine efficiency through mild hybridization (regen braking, 48-volt auxiliary components such as pumps, fans and compressors). Such technologies are not yet available, but will be in some cases by model year 2023 and beyond.

What’s to Come from SuperTruck II?

SuperTruck II got under way in 2016 and will wrap up this year. The Department of Energy has allocated $80 million split between five teams. Each recipient will match that amount, dollar-for-dollar. High-level goals include doubling current truck fuel efficiency and cracking 55% brake thermal efficiency for diesel truck engines. Current engines manage to convert no more than 45% of the chemical energy in a gallon of diesel into motion.

Development objectives for the teams include:

  • Cummins/Peterbilt will design and develop a new more-efficient engine and advanced drivetrain and vehicle technologies.
  • Daimler Trucks North America will develop and demonstrate a tractor-trailer combination using a suite of technologies including active aerodynamics, cylinder deactivation, hybridization, and the electrification of accessories.
  • Navistar will design and develop a vehicle and powertrain with electrified engine components that can enable higher engine efficiency and a significantly more aerodynamically reengineered cab.
  • Paccar will develop and demonstrate a vehicle with greater than 100% freight efficiency improvement relative to a 2009 baseline product with technologies targeted for a 36-month payback period.
  • Volvo will develop and demonstrate a tractor trailer combination with lightweight cab that achieves the freight efficiency goal using alternative engine designs and a variety of system technologies.

(These links take readers to the Annual Merit Review presentations from each of the OEMs describing in more detail their approach to SuperTruck II and some of the technology they developed.)

Like SuperTruck I, some of those technologies will make it to market with a couple of model-years. Some will lake a little longer. Much of what will be unveiled will be helpful in meeting the very challenging GHG Phase II rules for 2024 and 2027.

DOE has already announced funding for SuperTruck III. Five manufacturers will split $128 million in funding (matched by the recipients) to develop electric powertraind for medium and heavy-duty trucks. Teams include Daimler ($25.8 million), Ford Motor Co. ($25 million), General Motors ($26.1 million), Paccar ($33 million), and Volvo ($18.1 million).

A version of this article appeared in the June 2022 issue of Heavy Duty Trucking.

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