The final results won’t be known until the end of the year, but participants in the Department of Energy’s SuperTruck II program are racking up serious efficiency gains aimed at diesels that could ultimately help electric trucks go farther on a single charge.
The goals of SuperTruck II are 55% brake thermal efficiency (BTE) improvement for heavy-duty diesel engines and double the freight efficiency, as measured in miles per gallon multiplied by the freight tons carried.
Daimler Truck North America and its partners are developing a Freightliner tractor-trailer combination using aerodynamics, cylinder deactivation, hybrid engines and the electrification of accessories through 48-volt power.
Not just a diesel program
“SuperTruck is not just a diesel truck program,” Mike Roeth, executive director of the North American Council for Freight Efficiency, told FreightWaves. “A lot of these things make sense on battery-electric or hydrogen trucks. If you can get 20% fuel economy improvement with this stuff, that means you’re going to get 20% more range on an electric truck.
“On an electric truck, you can literally save 20% of the battery pack. You’re talking about huge money savings.”
Some aerodynamic gains from SuperTruck quickly find their way into production. DTNA showed several in 2019 on the 2020 Freightliner Cascadia, options that improved fuel efficiency by 5%. Other SuperTruck efforts, like lightweight chassis components, make good science projects but are hard to standardize for production.
“Aerodynamics and advanced cruise control are the two easiest ones,” Roeth said. “Those are helping get the 9-, 10-, 11-mile per gallon that we’re seeing. We’re seeing efficiency discoveries in SuperTruck that are being put into every model year.”
And not just in the tractor.
Strick Trailers, a DTNA partner, has produced a 53-foot trailer that shaves about 2,000 pounds from a typical trailer with aerodynamic components adaptable to the approximately 2 million trailers on the road, according to material from the June 2021 DOE merit review of DTNA’s technical progress.
DTNA was one of four awardees in SuperTruck II that DOE launched in 2016 after the initial five-year program that began in 2010 led to more than 20 technologies being adopted for production following research. DTNA is also one of five companies picked for SuperTruck III that will kick off in 2023.
Each of the four SuperTruck II participants got an equal share of $80 million from the DOE and put up an equal amount in cost sharing. The other awardees were:
- Cummins Inc. for the design and development of a more efficient engine and advanced drivetrain. It has made numerous upgrades to its X12 and X15 engines, including introducing natural gas versions and a refreshed X15 Performance Series designed to meet EPA and greenhouse gas phase 2 requirements. Cummins picked Paccar Inc.’s Peterbilt Motor Co. as a partner.
- Navistar International for the design and development of a vehicle and powertrain with electrified engine components that can enable higher engine efficiency and a reengineered cab that is significantly more aerodynamic than existing models. Navistar adapted the large cab from its LT flagship model for the new HX off-highway truck.
- Volvo Technology of America for the development of an 18-wheeler with a lightweight cab, alternative engine designs and a variety of improved system technologies. Volvo said it is on track to more than double vehicle payload per mile per gallon for productivity gains and improved fuel efficiency.
DTNA is hinting at what its SuperTruck may look like. Designers, surface modelers, fabricators and studio engineers compete globally to create sharp-edged sculptural shapes inspired by wind-carved snowdrifts and sand dunes.
“We see SuperTruck in a different way than other projects,” said Jeff Cotner, DTNA chief designer. “It allows us to take risks. … We feel very much that this is our opportunity to push a little bit and reach further out than we otherwise would.”
With $20 million in DOE money to spend, resources are less of an issue than normal for experimental pursuits that might not make it to production.
“There is this organic evolution, inspiration and excitement that comes from the competition,” Cotner said.
Though they collaborate with the design team, engineers lack such freedom, forced to stick to stringent parameters that would meet or exceed the 115% freight efficiency improvement target.
“The most difficult part is picking the right technologies with the right balance of performance for systems that are critical for energy conservation while making them complement the vehicle,” said Darek Villeneuve, DTNA advanced vehicle systems manager.
Some extra complexity is OK
The adoption of 48-volt power systems adds complexity to an already complex diesel truck, but it offers numerous advantages, including the potential to help meet lower nitrogen oxide pollution rules coming from the Environmental Protection Agency and the California Air Resources Board in 2024 and 2027, Roeth said.
Efforts on waste heat reduction are less likely to find their way into production.
“The waste heat is being lowered because of the efficiency of these engines and trucks and these systems are really complex,” Roeth said. “Diesel engines are already complex with the aftertreatment and all the other stuff. When we make them more complex, they get harder to compete with relatively simple battery-electric trucks.”