Hybrids – Vehicles, Battery & Hydraulic Technology

Could Your Next Work Truck Be a Hybrid?

March 2007, Green Fleet Magazine - Feature

by Terry Parkhurst

While hybrid passenger vehicles have garnered the lion's share of media attention and sales, many major truck manufacturers are developing diesel-electric hybrid trucks for the same reasons they did cars: fuel cost savings and a desire to reduce emissions, especially in congested urban environments.

No medium- or heavy-duty hybrids are for sale in America at this time. However, national fleets such as the U.S. Postal Service, United Parcel Service, Federal Express, Verizon and Coca-Cola are testing hybrid trucks and vans, as is the Department of Defense.

General Motors
On the light duty side, General Motors, along with corporate partners DaimlerChrysler and the BMW Group, have teamed up to co-develop a dual-mode hybrid system.

GM's version of the system will be launched this year in GM's 2008 Chevrolet Tahoe and GMC Yukon. The system uses two electrically continuously variable transmission (ECVT) modes to optimize power and torque for various conditions. Those modes are then combined with four fixed gear ratios for better efficiency and power handling applications.

When combined with Active Fuel Management, GM's cylinder deactivation technology, the dual mode hybrid system is hoped to give large SUVs a composite fuel economy improvement of 25 percent.

Work-truck pickup users take note: GM says it will implement the same system in its huge-selling full-size Silverado and Sierra pickups, though a release date has not been announced.

Breaking Down the Benefits

There are basically two types of hybrid systems: series hybrids, which use an internal combustion engine to generate electricity for the electric motor that drives the vehicle, and parallel hybrids, which use both internal combustion engines and electric motors for propulsion, yet switch back and forth as the situation demands.

One unique feature of a hybrid system is that brake energy can be recuperated with a large enough energy storage system. This can make a significant impact on fuel economy, especially in city driving.

"The more stop-and-go driving you do, the better the efficiencies," says Leif Johansson, president and CEO of truck-maker Volvo Group AB. "There's also higher starting torque than a normal diesel engine." "The diesel engine can be 35 percent smaller with a hybrid drivetrain. Also, you'll see more savings with complete electrification of the air conditioning, power steering and power take-off," explains Sten-Ake Aronsson, senior vice-president at Volvo Powertrain North America in Hagerstown, Md.

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