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Walmart showcases WAVE tractor-trailer at MATS; micro-turbine range extended electric vehicle with 45.5 kWh Li-ion pack
28 March 2014
Walmart showcased its Walmart Advanced Vehicle Experience (WAVE) at the Mid-America Trucking Show (MATS) in Louisville, Ky. WAVE is a tractor-trailer combination that features leading edge aerodynamics; an advanced turbine-powered range extending series hybrid powertrain; electrified auxiliary components; and control systems.
The project aims to demonstrate a wide range of advanced technologies and designs Walmart is considering in an effort to improve the overall fuel efficiency of its fleet and lower the company’s carbon footprint. Although the prototype currently runs on diesel, its turbine is fuel-neutral and can run on compressed or liquid natural gas, biofuels or other fuels.
|Walmart Advanced Vehicle Experience. Click to enlarge.|
The prototype is the result of collaboration between Walmart and many vendors, including Peterbilt, Roush Engineering, Great Dane Trailers and Capstone Turbine.
Tractor. Walmart and Peterbilt have collaborated on aerodynamic, hybrid, electrification and alternative fuel projects in the past, each with incremental gains in fuel efficiency and emission reductions. The Walmart Advanced Vehicle Experience tractor combines many of these projects in a single vehicle.
Powertrain. WAVE is a Range Extending Series Hybrid that features a microturbine Range Extender generator developed by Capstone Turbine Corporation. The micro-turbine is fuel neutral and produces very low emissions without the need for aftertreatment. Turbines are also appealing because of their few moving parts, low maintenance requirements and lighter weight.
Range extending hybrids are a synergy between electric trucks and series hybrids, and their design reduces the energy storage size required for trucks to run on batteries alone.
With Walmart Distribution Centers now located closer to metropolitan areas, transport vehicles have shorter transit times to their delivery destinations. These shorter trips reduce the vehicles’ average trip speed and create more opportunities to recover energy through regenerative braking. The generator and energy storage on the truck are scalable based on the range desired.
Capstone also engineered the truck’s integrated hybrid drivetrain solution. The use of a hybrid powertrain allows the turbine to remain at optimum operating rpm, while the electric motor/energy storage handles acceleration and deceleration. A longer-range version of this powertrain would feature a larger turbine and smaller energy storage system.
Vancouver (Canada)-based Corvus Energy is the Energy Storage System supplier for the truck. In each truck, there are 7 lithium polymer battery modules (96V) to provide 650 VDC for a total of 45.5 kWh. The system includes both the traction, braking, and control elements. The energy storage system is also used to supplement the generator and buffer the power for the accessory systems.
The batteries are sized to provide power for the truck’s systems when the vehicle is waiting for a few hours to drop off a load. Batteries also power the vehicle in a pure electric mode (w/o generator) for limited miles of stop and go driving, such as what might be found in a busy shipping terminal or traffic jam.
Component Electrification. With automobiles moving to electrified accessories such as power steering and air conditioning, this truck scales those systems up for use on a larger vehicle. These electrified components are used only when needed and at peak efficiency.
Aerodynamics. Designers used extensive computational fluid dynamics (CFD) analysis to optimize the truck’s styling. The truck’s shape represents a 20% reduction in aerodynamic drag over Walmart’s current Peterbilt Model 386. By placing the cab over the engine, the truck’s wheelbase is greatly shortened, resulting in reduced weight and better maneuverability.
Further, with the air-cooled microturbine, there is no need for a large radiator in front of the vehicle.
Walmart relied on product development supplier Roush Engineering to carry out the vehicle’s construction.
Trailer. The vehicle’s trailer, manufactured by Great Dane Trailers, offers a host of fuel-saving features. The trailer body is built almost exclusively with carbon fiber, including one-piece carbon fiber panels for the roof and sidewalls, saving nearly 4,000 pounds (1,814 kg) when compared to traditional designs. The trailer’s convex nose also enhances aerodynamics while maintaining storage space inside the trailer.
Other special features of the trailer include special low-amperage LED lighting strips, composite trailer skirts, aerodynamic disc wheel coverings, a Posi-lift suspension, and a one-piece, fiberglass-reinforced floor panel with a 16,000 lb (7,257 kg) forklift rating.
A number of vendor partners were involved in the design and creation of the Walmart Advanced Vehicle Experience. Key partners—in addition to Peterbilt Motors Company, Roush Engineering, Capstone Turbine Corporation and Great Dane Trailers—include Qualnetics Corporation; Allison Transmission; Transpower; New Eagle; Fiber-Tech Industries; Grote Industries, Inc.; Laydon Composites Ltd.; Isringhauser Seats; Graykon, LLC; Dometic Corp; RealWheels Corp; Corvus Energy; Parker Hannifin; Accuride; Milliken Chemical; SAF-HOLLAND USA Inc.; and Whiting.
In 2005, Walmart, one of the nation’s largest private fleet operators, announced its goal to double fleet efficiency by 2015. As of last year, the company had achieved an 84% improvement in fleet efficiency over its 2005 baseline.
Walmart is continually looking for innovative ways to increase our efficiencies and reduce our fleet’s emissions. The Walmart Advanced Vehicle Experience is a bold step in transportation technologies that, although not on the road in its current form, will serve as a learning platform for the future that will accelerate our progress toward our goals.—Tracy Rosser, senior vice president of transportation at Walmart
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