The hybrid electric Class 8 tractor, being built for a U.S. Army program that promotes joint military and commercial development, will be propelled at low speeds by electric motors and at high speeds by a diesel engine. The propulsion system will combine a 460-horsepower diesel engine with two 250-horsepower electric motors. Lead acid batteries charged by an on-board generator will power the electric motors.
The combination of the two technologies could significantly reduce emissions while increasing fuel efficiency -- all without sacrificing performance, according to Keith Brandis, vice president-business offer development at Volvo Trucks.
"Drivetrain technology is advancing so quickly that we must change the way we think of 'electric' power," Brandis said. "We expect this truck to demonstrate unprecedented acceleration.
"The theory behind the system suggests that the combination of diesel and electric propulsion could give drivers more power than today's high-torque, high-horsepower engines," Brandis said. "We also expect that the system will reduce operational costs due to the greater fuel efficiency and reduced engine maintenance requirements."
The future tractor also will be equipped with advanced safety systems. "Traffic safety is a critical issue for the Army, just as it is for commercial motor carriers," Brandis said. "Historically, 42 percent of peacetime fatalities suffered by the Army have occurred in convoy accidents. This truck will be a dramatic test to see how we can apply our well-known safety expertise to improve peacetime truck safety."
In addition to an Eaton Vorad collision warning system, the truck will feature a lane-tracking system that will warn the driver prior to an inadvertent lane change so corrective actions can be taken. It will also include an electronically enhanced vision system for the operator.
The electric motors will also be used as an auxiliary retarder. During brake applications, the motor's magnetic field will be reversed to provide increased stopping ability. The auxiliary retarding effect of the electric motors will also be used to re-charge the batteries.
Routine maintenance is expected to be reduced substantially due to the elimination of the mechanical transmission and reduced workload on the engine. The auxiliary retarding effect of the electric motor is also projected to double brake life.
Volvo engineers are currently overseeing the integration of Lockheed Martin's HybriDrive propulsion system with the driveline and electrical systems on a Volvo VNL highway tractor. The truck will begin testing this month. Some or all of the technologies being developed on the truck could be ready for commercial use within seven years.