NASHVILLE, Tenn. – At a time when a truck’s typical fuel economy floats around 6 mpg (39 litres/100 kms), the promise of 10 mpg (23.5 litres/100 kms) may seem like a pipe dream. But the dream may be closer to reality than you think.
Fifteen industry manufacturers have joined together in the 21st Century Truck Partnership, experimenting with everything from engines to heavy-duty hybrids, vehicle power demands, creature comforts in sleepers, idle-reducing technology, and new lightweight materials such as carbon fibre and high-strength steel. There are four projects in all – led by Daimler, Navistar, Volvo, or a joint venture between Cummins and Peterbilt – and each of them expect to have working prototypes within two years, a crowd was told during a recent meeting of the American Trucking Associations’ Technology & Maintenance Council.
“There’s a lot of new work going on here. It’s not just tweaking what we already have,” said Ken Howden, director of the 21st Century Truck Partnership in the US Department of Energy’s Vehicle Technologies Office. Each truck includes several technologies.
The Cummins and Peterbilt project includes components such as an enhanced Eaton transmission, Dana driveshaft, Delphi fuel cell, Alcoa wheels and Bridgestone tires, as well as a new energy recovery system. “The challenge is to get a lot of the heat energy out of the exhaust system,” Howden says. And the technology needs to be durable.
Gains in the Cummins engine will focus on things like turbocharger efficiencies and enhanced pumps. New sensors and upgraded electronics will also work closer with the transmission to find the truck’s “sweet spot.” And heat from the truck’s exhaust or exhaust gas recirculation will be recovered and transformed into mechanical power, while parasitic losses are being attacked with things like variable-flow lube pumps and low-friction cylinder kits. The size and shape of piston bowls are also being changed.
A waste heat recovery system for a linehaul truck would look much like an air conditioning loop, explained Jeff Seger, Cummins’ executive director of customer engineering and controls. Refrigerant is fed through a pump at 300 psi and heads to a heat exchanger to capture “high-quality heat.”
At that point, the refrigerant transforms into a vapor which spins a turbine to create power. As it loses heat, the vapor is fed into a condenser where it turns back into a liquid and flows back to the pump. For its part, the turbine combines with gear reducers and belts to deliver driving power to the crankshaft.
Under a heavy state and when fully loaded, it could help a truck improve fuel economy by 5%.
Closely integrated transmissions will support downspeeding, lower weights, and enhance communications, he added, referring to automated transmissions as a key “enabler” of this approach. Cruising speeds of 1,370 rpm could drop to 1,270 or as low as 1,170 rpm. And every 100 rpm drop will improve fuel economy by 1%.
Daimler’s project involves partnering with Great Dane trailers on a complete tractor-trailer package to be tested by Schneider National. A combined solution may be a logistical challenge for some fleets, but it would be an option for dedicated operations.
For its part, Navistar is working with Meritor on a truck with a hybrid powertrain. And Volvo’s SuperTruck team is drawing on European experience, incorporating everything from a new transmission to Freight Wing aerodynamics, and a waste heat recovery system of its own. There are certainly gains to be made. A mere 42% of the energy in a tank of diesel is turned into usable power. The remainder is wasted through friction and parasitic losses in pumps and exhaust gas recirculation loops, coolant, heat transfer through the radiator, and exhaust. Friction accounts for 8% of the lost energy, heat transfer wastes 24%, and exhaust amounts to another 26%.
Heavy-duty trucks consume one-fifth of the fuel consumed in the US, and the world’s commercial transportation needs are expected to consume 70% more energy in 2040 than they did in 2010. “In developing countries, their demand for diesel is even higher than ours,” Howden said. And there are few advantages to looking at other modes of transportation. Doubling the volume of today’s intermodal shipments, for example, would increase the railways’ share of the market by just 0.3%, he said.
But each equipment-based option presents unique challenges for engineers. As valuable as any enhanced aerodynamics may be, they also have to meet practical demands. “It can’t just look good,” Howden said. “This thing needs to work as a truck.” Engines and transmissions may offer the biggest potential gains, but they are the most expensive.
Eaton’s chief technology officer Tom Stover expects hybrids to play a larger role in vocational vehicles by 2025 and even emerge in linehaul vehicles. The good news is that the motors for hybrid systems are more affordable and less complex than ever. But there are still limits on battery technologies. Equipment will also need to rely on faster and smoother shifts, placing a larger focus on automated transmissions.
“GPS-enabled cruise control may just be the first step,” he said. Other controls could base decisions on traffic density, or the information shared between surrounding vehicles and infrastructure. Eaton is already testing a system that will communicate with traffic signals to see if the light is about to change.
As valuable as the equipment may be, the most important piece of the puzzle will still be sitting in the driver’s seat. “You can put all the technology you want in a truck, and a driver who is careless or indifferent about fuel economy can destroy that…the era of unrestricted decisions about gear shifting are likely coming to an end,” Stover said.
It hardly means that more traditional sources of fuel economy gains will be abandoned in the meantime. Selective catalytic reduction (SCR) equipment added to meet 2010 emissions standards improved fuel economy by 5%, Seger noted. The US Environmental Protection Agency’s (EPA) next round of standards, to come in 2014, will also focus on reducing carbon dioxide, and that means improved fuel economy. Over the next four years, EPA mandates will require fuel efficiency to improve by 10-23%. The second phase to come in 2019 will see that improve by another 10-20%.
The gains won’t even be limited to diesel. “The pressure for development for fuel economy improvement is going to be felt across the spectrum,” Stover said. He expects the gap between diesel and natural gas engines to close in the next 10 to 15 years.
“It’s going to be a different world. The trucks are going to look different. If we do it right, we’re going to create a lot of value for our customers.”
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