CLEANING UP RUBBISH COLLECTION

The New York City Department of Sanitation (DSNY) is busy testing Bosch Rexroth’s Hydrostatic Regenerative Braking (HRB) system in its refuse trucks. Bosch Rexroth has developed the HRB system as a means of improving fuel economy while reducing carbon emissions. The HRB hybrid drive system accumulates energy which is typically lost in the braking process, and uses the stored energy to provide supplementary power to the vehicle’s drive train.

The HRB system-equipped trucks are being operated in all five of the City’s boroughs, to test fuel efficiency and other parameters in a wide range of neighbourhoods, seasonal conditions, and operating environments. HRB systems typically achieve up to a 25 percent reduction in fuel consumption in heavy vehicles and mobile equipment, by recovering energy used in braking.

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

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.

According to Bosch Rexroth, HRB technology has already undergone field testing in urban settings, with positive results. “We started our in-field testing of HRB last summer with a refuse customer in Berlin, Germany, and are now introducing this proven technology in North America,” says Ed Greif, vice president, Engineering Development Hydraulics, Bosch Rexroth. “Field testing has verified our simulations and we anticipate similar success in the US.”

Hydraulic hybrids, due to their high power density, are well equipped to cope with the high power requirements of regenerative braking. Maintaining efficiency during energy conversion, hydraulic hybrid systems have the potential to capture a large portion of the braking energy and make use of it more effectively. Reduced brake maintenance costs and the associated vehicle downtime offer another significant system savings. Since it is possible to slow the vehicle without engaging the foundation brakes as often, 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.