Parker Hannifin Commercializing Series Hydraulic Hybrid System for Delivery Vehicles; Initial 20 Unit Order from Freightliner Custom Chassis
|The FCCC hydraulic hybrid chassis. Source: FCCC.Click to enlarge.|
Freightliner Custom Chassis Corporation (FCCC), a subsidiary of Daimler Trucks North America, has made an initial 20 unit commercial commitment for a series hydraulic drive system from Parker Hannifin. (Earlier post, earlier post.) The commitment came as part of a grant under the United States Department of Energy’s Clean Cities program and was funded through the American Recovery and Reinvestment Act.
Daimler Trucks North America LLC (DTNA) spearheaded the submittal of these winning applications which will support the purchase of 638 hybrid and alternative fuel vehicles. Parker is the only supplier of the hydraulic hybrid systems for the vehicles. The series hydraulic hybrid systems will be incorporated into delivery vehicle models, based on the FCCC MT-55 chassis, intended for use by United Parcel Service (UPS).
|Hydraulic hybrid system in the FCCC chassis. Source: FCCC. Click to enlarge.|
A hydraulic hybrid drivetrain uses hydraulic accumulators to store energy. As hydraulic fluid enters either accumulator, the nitrogen that accumulator compresses and its pressure rises. Like other hybrid systems, energy saved when applying the brakes is reused to help accelerate the vehicle. Compared to batteries as an energy storage device for hybrids, the hydraulic accumulators offer a higher power density, but a lower energy density. The accumulators support a higher energy flow, not limited by overheating, and are more efficient at charging/discharging.
Field testing of the system during the past year has indicated that the hydraulic system is capable of generating as much as a 50 to 70% increase in fuel economy in stop-and-go applications when compared with traditional diesel powered vehicles that have automatic transmissions. The hydraulic hybrid improves fuel economy in three ways: recovered braking energy; improved engine efficiency; and its engine-off feature.
Brake Energy Recovery. The hydraulic hybrid is able to recover and reuse about 70% of the energy that otherwise would have been wasted during the braking process. Typical electric hybrids can only recapture about 20-25% of the brake energy, according to Parker.
Optimized Engine Control. WIth the engine decoupled from the drive axle (it drives the hydraulic pump when needed), the engine can operate in “the sweet spot” to optimize fuel consumption. There are also no torque converter spin losses.
Engine “Off” Strategy. The engine is off during vehicle operation until needed to drive the hydraulic motor.
|Engine operating points (torque vs. rpm). (Left) Baseline engine. (Right) Series hydraulic hybrid. Source: FCC. Click to enlarge.|
Prior to field testing, the system was validated for fuel efficiency by the United States Environmental Protection Agency at its National Vehicle and Fuel Emissions Laboratory in Ann Arbor, Michigan.
We believe the series hydraulic hybrid technology has application not only in delivery vehicles, but also for yard hostlers and city buses. Additionally, our advanced series hydraulic hybrid system, called RunWise, is currently being field tested in more demanding applications such as with refuse vehicles. This is a technology that holds great promise as a contributor to reduced environmental impact and increased fuel efficiency.
—Dr. Joe Kovach, Group Vice President of Technology and Innovation for Parker's Hydraulics Group
|The RunWise advanced series hydraulic hybrid system. Click to enlarge.|
Unveiled at Waste Expo 2009, RunWise – Modular Gen I features a patent-pending cradle design for packaging mechanical, hydraulic, and electrical components. Because the cradle houses all major hydraulic subsystems, it facilitates manufacturing, installation, testing, and servicing. Cradle design flexibility accommodates multiple chassis configurations and simplifies OEM truck assembly with minimal electrical, driveshaft, and cooling system hookups. If major service is required, the cradle can be removed and a new cradle reinstalled quickly, eliminating vehicle downtime.
A Parker hydraulic hybrid system is also incorporated in the series hydraulic hybrid yard hostler developed by EPA and FEV that will be going into service in New York. (Post.)