APRIL 2011

Fairfax County utilizes hydrostatic regenerative braking in trash truck

The Fairfax County Solid Waste Program in Virginia is using a Bosch Rexroth parallel hydrostatic regenerative braking system (HRB) in the county’s first hydraulic hybrid trash and recycling vehicle. The Rexroth HRB system was retrofitted in January 2011 on a 2007 Mack Truck Granite Chassis with a Heil Environmental Formula® 5000 rear loader body.

According to Michelle DuHadway, account manager for Rexroth’s parallel regenerative hybrid braking systems unit, the HRB system can generate up to 25 percent savings in fuel and energy costs depending on duty cycle and driver behavior. The actual savings for this project will be determined during these field trials.

The Rexroth HRB system, funded by a grant from the American Recovery and Reinvestment Act, uses a hydraulic pump/motor connected to the driveline, to capture kinetic energy during vehicle braking. When the driver presses the brake pedal, a hydraulic unit integrated into the drivetrain presses the hydraulic fluid into a high-pressure reservoir. The resulting resistance makes the vehicle decelerate. When accelerating, the hydraulic pressure reservoir is controlled electronically to release the pressure and relieve the load on the diesel engine. Each time a driver brakes, the HRB system stores energy which would otherwise be lost.

“Every refuse truck in Fairfax County stops and starts about 800 times a day filling trash and recyclables,” added Ben Boxer, communications and outreach manager for the Fairfax County Solid Waste Management Program.

Hydraulic hybrids have the potential to capture a large portion of the braking energy and use it more effectively, extending brake wear and reducing brake maintenance costs and the associated vehicle downtime. Since it is possible to slow the vehicle without engaging the foundation brakes as often, the life of the vehicle’s brakes is extended and the amount of brake dust released into the environment is reduced.