Wal-Mart Stores, which operates the nationÃ¢â‚¬â„¢s second largest private fleet, is supporting development of new hybrid technologies by helping to validate the concept and refine the final design.
During third-party testing, the hybrid system has routinely achieved a 5-7 percent fuel savings versus comparable, non-hybrid models. It may result in a savings of one gallon of fuel per hour when idling, according to Eaton.
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 hybrid electric power system features an automated manual transmission with a parallel-type Ã¢â‚¬Å“directÃ¢â‚¬? hybrid system, incorporating an electric motor/generator located between the output of an automated clutch and the input to EatonÃ¢â‚¬â„¢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.
Fuel efficiency and emissions reductions are best achieved both while the truck is rolling or standing still. The systemÃ¢â‚¬â„¢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.