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Hydraulic systems & components

4th Quarter 2009 Hydraulic systems & components

The New York City Department of Sanitation is conducting an in-field evaluation of hydrostatic regenerative braking systems in its refuse trucks.

Bosch Rexroth has developed the hydrostatic regenerative braking system (HRB) as a means of improving fuel economy while reducing carbon emissions. The HRB hybrid drive system accumulates energy that is typically lost in the braking process, and uses the stored energy to provide supplementary power to the vehicle’s drive train.

Bosch Rexroth’s HRB technology captures and stores energy usually lost in the braking process

Field tests

Field tests of the HRB parallel hydraulic hybrid system were launched to assess the technology’s viability for use as an alternative drive system for the New York City Department of Sanitation (DSNY) refuse trucks. The field evaluations are designed to authenticate the technical and economic benefits of the HRB system, and to provide real-world operating data, which DSNY will use to consider large-scale deployment of the technology within the city’s in-service and new vehicle fleets.

The HRB system is installed onto a Crane Carrier Company LET2 truck integrated with a Heil Environmental refuse body. Two identically equipped trucks are being provided for the evaluation.

Operating principle

The Rexroth HRB system uses a hydraulic pump/motor, connected to the driveline, to capture kinetic energy during vehicle braking. When braking, the pump/motor acts as a pump, absorbs energy from the driveline and imparts a retarding force on the drive wheels, pumping hydraulic fluid into a nitrogen-pressurised accumulator. During acceleration, the pressurised gas pushes fluid out of the accumulator, and the pump/motor then acts as a hydraulic motor, assisting the engine and reducing the fuel required to launch the vehicle. This process is commonly referred to as regenerative braking.

Ed Greif, vice president, Engineering Development Hydraulics, Bosch Rexroth says, “Field testing in Europe has verified our simulations and we anticipate similar success in the US.”

Additional benefits

Hydraulic hybrids, due to their high power density, are well equipped to cope with the high power requirements of regenerative braking. With high energy conversion efficiency, hydraulic hybrid systems have the potential to capture a large portion of the braking energy and make use of it effectively. Reduced brake maintenance costs and the associated vehicle downtime offer another significant system savings. The lifespan of the vehicle’s brakes is extended and the amount of brake dust released into the environment is reduced.

Hydraulic technology has been widely used for some time in rugged, heavy duty fleet applications such as refuse trucks and construction equipment. While its deployment as a hybrid application is new, the integration of HRB systems into existing commercial fleets is efficient, as hydraulic systems use conventional materials and processes, and have established maintenance, repair and recycling protocols.

For more information contact Willem Gijzelaar, Hytec Holdings, +27 (0)11 979 4630, [email protected], [email protected]

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Hybrids clean up Big Apple

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