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.