Hybrid COMBATT

Automotive Design & Production, March, 2003 by Christopher A. Sawyer

Perhaps because the military is tired of 60 Minutes running stories about $600 toilet seats, the U.S. Army has established its COMBATT program: Commercially Eased Tactical Truck. It cuts development time and cost by taking commercially available products, and modifying them to meet military requirements. Presumably, the monies Formerly spent on design and development now can be spent on making all manner of improvements. Like the diesel-hybrid pickup GM Defense Military Operations has developed.

One of the eight Chevy Silverado-based prototypes From GM looked like a wish-list contestant. The 6.6-liter, 210-hp Duramax V8 diesel is mated to an Allison-developed parallel-hybrid electric drive that packages a split-power CVT in place of the typical Allison 1000 transmission, and integrates it with two AC induction electric motors that provide supplemental power to the drive wheels. [This drive system is a downsized version of the one Allison will introduce later this year for use in intra-city buses.] Mounted behind and to either side of the driveshaft sit two battery boxes filled with nickel-metal hydride batteries, and the power inverter and control modules. "The hybrid drive system reduces emissions and increases fuel economy by 20% compared to diesel trucks, and 25% to 40% compared to conventional gasoline trucks," says Or. Larry Burns, GM vice president, Research & Development and Planning. "With fuel transportation costs ranging from $10 to $400 per gallon, depending on whether the fuel is being us ed for training exercises or battlefield operations, the cost savings could well be in the millions of dollars."

"Fuel efficiency keeps assets fueled and moving," says Brigadier General Roger Nadeau, program executive officer, Combat Service Support, U.S. Army. "But the 'silent watch' capability of this vehicle increases battlefield effectiveness, and reduces the need for generators and all of the on- and offsite staff necessary to support this equipment." An on-board hydrogen fuel cell auxiliary power unit complements the military Silverado's 30-kW diesel generator, which itself eliminates the need for a portable generator unit. The Hydrogenics Carp. (Toronto, Ontario) fuel cell APU quietly provides 5 kW of electricity with a low heat signature for the command center in the pickup bed. Hydrogen for the fuel cell is created by passing electricity generated by the vehicle and is used through an on-board electrolyzer, eliminating the need for an external hydrogen supply. It is stored in a low-pressure, high-density metal hydride tank in the command center.

When the engine is off, or the command center is removed and left behind as a "silent" observation post, the fuel cell can produce up to 5 kW of power to run the command and communications equipment contained within. Three hours of peak power run time are possible, or five hours at an average output of 3 kW. This is six to 10 times greater than possible with a battery-based system of the same size. The water produced by the fuel cell is stored and re-used by the electrolyzer, but must be replenished every six to 10 cycles. It's also possible to use this byproduct for hydrating battlefield personnel.

The COMBATT technology, which also includes Quadrasteer rear-wheel steering and a four-wheel jounce shock system derived from GM's off-road race trucks, will be evaluated by the Army over the next 18 months in order to establish performance and procurement criteria before opening the bidding process for this technology.