Mack Trucks is deploying a highly intelligent GPS that tells a plug-in hybrid truck when to run in electric mode and when to revert to diesel.
The company is using a method of geofencing – GPS and radio-frequency identification technology that creates a virtual geographic boundary – that tell the vehicle when swap powertrains.
So far, the ongoing “geofencing” test program out of the ports of Los Angeles and Long Beach has shown a 25 to 30 percent fuel savings.
“It’s too soon to tell whether there is a business case, but we are trying to design this as if we will build it one day,” project chief Pascal Amar told Trucks.com.
In the meantime, “we are still refining and we need to get more prototypes into operation,” Amar said.
Even if Mack decides to build retail versions of its GPS-guided, diesel-electric truck, “it is an interim solution” at best, said Antti Lindstrom, trucking industry analyst with IHS Markit.
Neither geofencing nor plug-in hybrid technologies are new, although Mack has combined them in a novel manner. But plug-in hybrids are expensive because they use two competing powertrains.
The project also could result in a truck that uses diesel for many of its miles without violating ever-tightening emissions standards, but Lindstrom doesn’t see it as a bid to shield diesel from environmental pressures in air quality-impacted areas.
Mack parent Volvo Group and its various brands “are moving step by step” along with most other truck and engine manufacturers to develop trucks that can operate economically in “the zero emissions environment that California’s ports are heading to,” Lindstrom said. “This project is an effort to use technologies they are familiar with to further the move toward [full] electrification. Plug-in hybrids are just an interim step,” he said.
Among the other test programs in operation at the Southern California port complex — the nation’s largest in terms of annual freight tonnage handled — a Cummins Westport Inc. venture is testing low NOx natural gas engines, Toyota is testing a fuel cell electric drayage truck and a number of all-electric BYD drayage trucks are shuttling freight from the ports to area warehouses.
Additionally, Kenworth is developing both a fuel cell electric drayage truck and a port truck using a natural gas generator to extend the range of its battery-electric powertrain. Tesla Inc. is developing a battery-electric Class 8 truck with drayage capabilities, and British engineering and engine development firm Ricardo recently began development work on a liquid nitrogen enhanced diesel engine that promises very low production of smog-producing nitrogen oxides, or NOx.
Mack’s project began in 2012 when Volvo Group decided to see if the plug-in hybrid system in its European transit buses could be applied to heavy-duty trucks. This would help address the Southern California port area’s well-documented air-quality issues, Amar said.
It took several years of development and testing to get the first truck built and into service in 2016. A second truck, designed to take advantage of things learned during the initial phase of the program, was put into service in late 2017.
Both trucks, Mack Pinnacle day cabs, are outfitted with a plug-in hybrid system consisting of a 150-kilowatt electric motor sandwiched between the gearbox and a slightly downsized, 11-liter, 400-horsepower diesel engine. A non-hybrid drayage truck of the same size would typically use a 13-liter diesel, Amar said. A 15-kilowatt-hour lithium battery pack stores energy to run the electric motor.
That’s the muscle. The electric motor only puts out 200 horsepower, but the port area is mostly flat, and a drayage truck’s work demands torque, not horsepower. “We have plenty of torque in the electric motor,” Amar said.
It has proved sufficient to enable the trucks to run in all-electric mode within the ports, where air-quality regulators are pushing hard for elimination of diesel engine operation.
Using an on-board computer linked to the truck’s GPS system, Amar’s team programmed the boundaries of the port area into the first truck, creating a geofence.
When the truck’s GPS system could “see” that it was within the area outlined by the geofence, the computer switched the drive system into all-electric mode, running it as an energy-efficient, emissions-free vehicle. It automatically swapped to diesel-hybrid mode when it left the geofenced area.
In diesel-hybrid mode, the truck’s powertrain delivers 1,550 pound-feet of torque and 400 horsepower, Amar said. The electric motor gives the diesel engine a bit of boost on takeoff and when it is shifting gears, to improve drivability, he said.
The 11-liter hybrid-electric powertrain “has more oomph than a 13-liter diesel,” Amar said. Combining the smaller diesel with the truck’s all-electric mode has resulted in 25 to 30 percent fuel savings and substantial emissions reductions over the trucks’ full operating cycles, he said.
The second truck greatly enlarged the area in which the all-electric mode was employed and did away with the need to load the computer with pre-determined electric-only areas.
“We were almost too conservative with the first truck,” Amar said. With the original scheme, there were missed opportunities to turn the engine off and run in electric mode, he said.
The new truck is programmed to decide for itself where it can run in all-electric mode. It doesn’t carry a set of preprogrammed geofenced areas; the onboard computer creates and continuously updates them using parameters such as engine operating conditions, vehicle weight and road conditions.
“It identifies areas [on the truck’s route] where only electric power is needed, and it decides when to turn the diesel power on and off, and it’s seamless to the driver,” Amar said.
“It’s constantly learning, changing data as needed,” he said. “If traffic slows and the truck can handle the speed in electric mode, then it will switch to zero-emission operation until speeds pick up again.”
As Mack enters phase three of its test, the goal is to document reductions in emissions of NOx.
NOx are reduced in all-electric mode, but increased zero-emissions operation also keeps the diesel engine cool. The treatment system designed to reduce NOx in diesel exhaust “struggles to perform well when the engine is cold or cool,” Amar said.
During the second phase, Amar’s team did measure reductions in NOx output for two days. “The numbers were almost too high, in the same order of magnitude as the fuel savings,” he said. “Now we want to make sure that is consistent.”
There’s no timeline for ending the testing, but Amar said the emissions phase should be wrapped up sometime next year.
“Then we’ll sit down and determine where to go,” he said.