Government agencies such as the Defense and Energy departments are working to adapt new technologies like hydrogen-fuel-cell-powered vehicles that conserve finite, pollution-producing and increasingly expensive fossil fuels.

The Army has been testing a prototype hydrogen-fuel-cell system installed within a conventional truck platform for about a year now, said Bill Haris, a mechanical engineer at the Army's National Automotive Center. The NAC is part of the U.S. Army's Tank Automotive Research Development and Engineering Center at Warren, Mich. The application is geared toward nontactical vehicle usage.

A hydrogen fuel cell is a device that produces electricity, water and hot air, Haris said. Hydrogen coming into the fuel cell, he said, is chemically converted into electricity and steam.

"There is zero pollution," Haris said.

The one-of-a-kind prototype is based on a Chevrolet Silverado, Haris said. The truck's original engine, transmission and gas tank were removed and replaced with two hydrogen fuel cells and two electric motors - one motor drives the front wheels and the other drives the rear wheels.

And "the plumbing and the storage tanks for the hydrogen, as well as the brains to control all the energy flow" are installed, Haris said.

In comparison, a hybrid vehicle uses two types of energy sources to provide motive power, Haris explained. One type of hybrid vehicle now being sold has an electric motor, a large battery used to operate the motor, and a small gasoline engine, he said.

At slower speeds the hybrid's electric motor moves the vehicle, Haris said, while the gasoline engine is employed during faster highway travel or to provide more acceleration. Hybrids are designed to provide better fuel mileage and less pollution than a conventional gasoline-powered internal-combustion-engine vehicle.

"So a hybrid is an extension of what you've already got. It's taking what you have and adding things to it to try and give it a little bit more capability," Haris explained. By comparison, a fuel-cell vehicle "is essentially a battery-driven vehicle," he said.

Hydrogen fuel-cell vehicles employ "a totally different technology than what you'd find under a conventional hood," Haris said. When viewing the motive system of a hydrogen fuel cell vehicle "people just don't know what they're looking at," he said. "It's all very foreign."

A conventional gasoline-powered automobile will achieve around 30 percent energy efficiency, Haris said, while a fuel-cell unit will post about 50 percent efficiency.

"That's where you gain your fuel efficiency," Haris said, adding that no hydrocarbon-based fuels, like gasoline or diesel, are used to power the Army's prototype hydrogen-fuel-cell vehicle.

Hydrogen fuel is available in both liquid and compressed gas form, Haris said. The industry, he said, is currently favoring compressed hydrogen gas for fuel-cell-powered vehicle application.

The Army's developmental hydrogen fuel-cell truck is capable of reaching speeds of 95 mph, Haris said. But its current range of 125 miles per fill-up is only about half of hydrocarbon-fueled vehicles, he said.

"That's one of the areas that really need to make a huge step forward," Haris acknowledged. On method under study to solve the distance issue is employing some type of solid-hydrogen storage system.

"We recognize it is a limitation and recognize that the industry is working really hard to address it," Haris said.

The hydrogen truck came on line last spring, Haris said. "It's an interservice program with the military," he said. The Marines also have interest in the project.

Leveraging commercial research on hydrogen fuel cells dovetails with DoD's desire to harness private-industry expertise, said Harold Sanborn, an expert on alternative fuel sources who also works at NAC.

"We need to look at commercial technologies and find out if they are ready for military applications," Sanborn said.

The hydrogen-fuel-cell-truck concept also "is a good starting point for discussion about modernizing our bases and the base infrastructure to make our bases more efficient and cleaner overall," Sanborn said.

Right now, fuel cells are from five to 10 times more expensive than internal-combustion-engine-driven systems, Sanborn said. He also acknowledged that using compressed hydrogen, a highly flammable element, does present unique safety and storage concerns. However, those concerns are being addressed with success, Sanborn said.

Some day military bases may replace their internal-combustion-engine truck fleets with fuel cell or fuel cell/ hybrid vehicles, Sanborn said.

"Then they could use clean-burning hydrogen in that application and drive those vehicles in their duty cycles," he said.