Mack Trucks Inc. this week, in conjunction with the United States Air Force Advanced Power Technology Office, displayed on Capitol Hill a prototype hybrid electric powertrain for Class 8 heavy-duty trucks.

The powertrain is mounted in an Air Force R-11 6,000-gallon capacity refueler truck built on a Mack RD 6x4 chassis.
Diesel hybrid electric vehicles combine the power of an electric motor with that of a diesel engine. The electric motor assists the diesel in launching the vehicle and regenerates energy during braking. This energy is stored as electrical energy and is then used in place of diesel fuel.
Anticipated advantages of hybrid electric technology include better fuel economy, reduced emissions and noise, longer engine and brake system service intervals, and lower overall operating costs.
The refueler displayed on Capitol Hill Wednesday was developed largely in Hagerstown, Md. The work was done under a $1.2 million Department of Defense contract Mack received through Southwest Research Institute in 2003. Enova Systems supplied the motor, motor control and battery system used in the vehicle. Kovatch Industries manufactured the refueler tank and pumping station.
The vehicle is what is referred to as a mild hybrid. Mild hybrids assist in launching the vehicle and recover braking energy.
Congressional support has since resulted in additional funding to build upon the knowledge gained via the refueler project. The goal is to develop a full hybrid system that can launch a heavy-duty truck with only electric power. Full hybrids do not require the engine to idle while stopped. This further reduces the amount of fuel consumed and noise levels associated with vehicles that stop frequently, such as refuse trucks. The majority of this additional development work is being performed in Hagerstown at Volvo Powertrain North America, supplier of engines to Mack Trucks Inc.
“The development of this technology is in line with our goals of enhancing our nation’s military capabilities, supporting the Air Force's environmental policy requirements and reducing our dependency on foreign energy sources,” said APTO Chief Mike Mead.
A likely commercial use for full hybrid technology is a refuse hauler based on a Mack platform. Mack is the leading manufacturer of refuse trucks in North America with more than 70 percent of the market.
“We believe this technology shows promise for urban vehicles such as refuse trucks for many of the same reasons that the Air Force is interested in the refueler – reduced cost of operations and emissions without loss of performance,” said Guy Rini, director of advanced propulsion systems and Mack program manager for the hybrid project.