(Updated 8/4/09; Original 3/20/07). Walmart operates 7,000 trucks that in 2005 drove 872 million miles to make 900,000 deliveries to its 6,600 stores. Wal-Mart has set a goal of doubling the fleet efficiency by 2015 from a 2005 baseline.
Wal-Mart operates the nation’s second largest private fleet. Wal-Mart is also famous for being operationally efficient. Every large fleet and logistics operator hopes to save millions by learning from Wal-Mart’s new initiatives. Wal-Mart has hundreds of hybrid passenger vehicles. Now Wal-Mart sees bigger potential savings in heavy-duty Class 8 trucks.
Wal-Mart uses a three-phase new technology deployment process, to test and pilot promising technologies, and then deploy the technologies that make economic and environmental sense.
Wal-Mart is defying the conventional wisdom that hybrid technology is of little help for large trucks that already have efficient diesel engines. Wal-Mart delivers goods from regional warehouses on an optimized route to its stores. Routes often involve heavy stop-go city driving. With hybrid technology, every touch of the brakes causes energy to be captured. Where trucks previously idled with engines running, hybrids can run all auxiliary power with the engine off, using large battery stacks for the electricity.
The Eaton heavy-duty hybrid system with idle reduction features an automated manual transmission with a parallel-type direct hybrid system, incorporating a 44 kW 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.
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. With a successful test and evaluation program, the heavy-duty hybrid electric power system will be available in 2009.
Wal-Mart Transportation is also evaluating an ArvinMeritor hybrid dual-mode diesel-electric tractor prototype. It will be based on an International Class 8 ProStar tractor and powered by a Cummins engine. ArvinMeritor will provide the tandem axle, regenerative braking system, air disc brakes and advanced ABS with integrated stability control and driver assistance systems, software, electronic controls, transfer case, motors, as well as the battery power.
“ArvinMeritor is a leader in all areas of drivetrain and brake system development for heavy-duty commercial vehicles and is an ideal partner for Wal-Mart for the development of these dual-mode diesel-electric systems,” said Tim Yatsko, Senior Vice President of Transportation for Wal-Mart.
A big loss for Wal-Mart and all long distance truckers is that engines are left running at stops for many auxiliary needs including air conditioning, heating, running electronics inside the cab and more. Not waiting for the implementation of hybrid drive systems, Wal-Mart installed auxiliary power units on new trucks.
Wal-Mart worked with the Rocky Mountain Institute to introduce new trucks with many energy saving improvements including better aerodynamics, transmissions and tires. Wind skirts under the trailer significantly reduced wind resistance and improved mileage. Wal-Mart combined the two wheels normally seen on a rear axle into a single wheel that is not quite as wide as the sum of two wheels. This gives a smoother ride and better fuel economy from the reduced surface area and improved tire wall stiffness. Wal-Mart is also disciplined about keeping tires properly inflated.
Wal-Mart saves diesel fuel both with vehicle technology and common sense. By working with its suppliers, Wal-Mart is fitting more goods in smaller and lighter packaging. More goods move in a truck without adding weight. Fuel is saved.
Fleet efficiency is just part of part of Wal-Mart’s sustainability strategy.