Kenworth, owned by Paccar, has a medium-duty Class 6 (26,000 pound gross vehicle weight) hybrid-electric truck based on the model T270 platform. This truck utilizes the Paccar-Eaton diesel-electric hybrid drivetrain in a parallel hybrid format and produces 25-35 percent better fuel efficiency for most applications and up to 50 percent for others.
The truck is offered in the North American market through Kenworth dealers nationally. The truck has been deployed by several fleets, including Coca-Cola and FedEx. The core of its drive train is a combination of the PX-6 6.7-liter, 300 horsepower, 620 pound-feet of torque diesel engine from Paccar combined with Eaton's transmission-mounted motor and control system as well as a 370V lithium-ion battery pack.
The plug-in hybrid truck uses the motor in a parallel hybrid setup to assist the engine in propelling the truck up to 30 mph. At that point, the motor shuts off and the truck drives as a standard diesel. The low-speed propulsion boost significantly lowers fuel consumption, however, as this is when diesel engines are at their worst in terms of efficiency.
Diesel engines are made to have an rpm range that marks their best efficiency (in terms of torque and fuel use). During low speed operations and while gaining speeds on highways, this is often not where the engine's optimum rpm range is and that, combined with a heavy load, pull down the truck's mpg.
By assisting during this critical phase of truck operation, the motor vastly improves efficiency. In normal duty cycles for medium-duty trucks such as boom lifts, tow trucks, and delivery applications, these vehicles often do a lot of stopping and starting and travel at below highway speeds through urban traffic. For this reason, the hybrid system in the T270 is capable of bringing fuel efficiency improvements of 30 percent. For vehicles which stop and idle often, such as boom lift work trucks, the larger energy storage capacity can cut idling time and improve efficiency up to 50 percent over standard diesel rigs.
The trucks come at a premium, however, adding $30,000 or more to their price tag for the hybrid option. This can be mitigated over time in fuel and maintenance savings, with most fleets having a return on investment in 3-5 years. For most medium-duty fleets, the average lifespan of a truck is 5-7 years, so the return could become profitable.
In addition, of course, the trucks can also see more environmental improvement by substituting petroleum diesel for biodiesel and are fully capable of running on biodiesel blends up to B85.
With recent studies showing that the largest fleet adoption of commercial hybrids will be in the medium-duty (Class 4-7) range, hybrids like the Kenworth T270 will become more and more common on the roads around us.