Bosch Rexroth is working with the City of Los Angeles Department of Public Works, Bureau of Sanitation, to study the benefits of hydraulic hybrid technology in its refuse truck fleet. The project involves Bosch Rexroth's Hydrostatic Regenerative Brake (HRB) system, which captures a vehicle's braking energy and converts it to energy for propulsion.
As a first step, two American LaFrance LLC Condor liquid natural gas (LNG) trucks in the city's fleet will be outfitted with vehicle data acquisition systems to monitor real-world operating conditions.
New West Technologies LLC is analyzing the data and providing Bosch Rexroth with the truck duty cycle data for the refuse fleet. Most important are vehicle speed profiles, engine operating maps, and operating characteristics that help determine sizing for the hydraulic components.
The Rexroth HRB system uses a hydraulic pump/motor, connected to the driveline, to capture kinetic energy during vehicle braking. This energy would otherwise be lost as heat in the vehicle's friction brakes. When braking, the pump/motor acts as a pump, absorbing energy from the driveline, and imparting a retarding force on the drive wheels. The absorbed energy is used to pump hydraulic fluid into an accumulator that contains inert gas that is compressed by the incoming fluid. During acceleration the pressurized gas pushes fluid out of the accumulator and the pump/motor now acts as a hydraulic motor, assisting the engine and reducing the fuel required to launch the vehicle.