Wal-Mart's Trucks Go Green

New hybrid truck developed by Peterbilt Motors and Eaton.

As part of its "Sustainability 360" program, Wal-Mart Stores, Inc. will be switching over to the hybrid version of the Peterbilt Model 386. The hybrid technology, which was jointly developed by Peterbilt Motors Company and Eaton Corp., has been integrated into an aerodynamically styled heavy-duty vehicle.

"We are continually looking for new, innovative ways to improve the fuel economy and reduce the emissions of our fleet. We currently operate the Peterbilt Model 386, and we anticipate that the hybrid version will help us move toward our goal to increase our fleet efficiency by 25% over the next few years," said Tim Yatsko, senior vice president of Transportation.

During third-party testing, the Eaton Hybrid Power System has routinely achieved a 5-7% fuel savings versus comparable non-hybrid models, the companies said. It may result in a savings of one gallon of fuel per hour when idling. At the current average diesel price of almost $2.50 per gallon, those savings equate to about $9,000 to $10,000 a truck per year in operation. The heavy-duty hybrid electric power system is expected to become available in 2009.

The heavy-duty hybrid electric power system features an automated manual transmission with a parallel-type "direct" hybrid system, incorporating an electric motor/generator located between the output of an automated clutch and the input to Eaton's Fuller UltraShift transmission. The system captures energy generated by the diesel engine and recovers energy normally lost during braking and stores the energy in batteries. That electric torque is then sent through the motor/generator and blended with engine torque to improve vehicle performance, operate the engine in a more fuel-efficient range for a given speed and/or operate only with electric power in certain situations.

In this heavy-duty application of Eaton's hybrid power technology, fuel efficiency and emissions reductions are best achieved both while the truck is rolling or standing still. The system's batteries power the heating, air conditioning and vehicle electrical systems while the engine is off. When the idle reduction mode is active, engine operation is limited to battery charging, an automatically controlled process that takes approximately five minutes per hour to fully charge the system. In the proposed system design, a proprietary feature minimizes engine vibration during start-up and shutdown during the recharge periods, allowing the driver to rest without interruption.

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