Now, as he reaches the latter stages of his career, the 62-year-old letter carrier is carrying his bundles of letters and packages in a vehicle that offers an eerily quiet ride, doesn't rely heavily on oily lubricants and emits droplets of water from the tailpipe.

Sisk is among a select group of government workers, academics and individuals testing hydrogen-powered vehicles in demonstration projects across the country. With gasoline prices hovering around the $3 mark this summer, the routine driving done by Sisk and others is helping researchers develop improvements for the technology, which could form the basis of the next generation of alternative vehicles.

"People think I was around for the horse and buggy days - but I wasn't," Sisk said with a smile during a recent ride along his route aboard General Motors Corp.'s HydroGen3 minivan.

Virtually every automaker is conducting tests of hydrogen-powered vehicles, which have received support from a 5-year, $1.2 billion hydrogen initiative first announced by President Bush in his 2003 State of the Union address.

The pollution-free technology holds the potential of zero emissions and a sustainable source of energy produced when hydrogen and oxygen are mixed. The vehicles could begin appearing in showrooms by 2020, or even earlier, according to government and industry experts, but many obstacles exist, ranging from high costs and a lack of fueling stations to the need for improved storage capacity and better range.

With the technology still in its early stages, the vehicle testing gives automakers valuable information on their progress based on typical driving experiences. Hydrogen technology can be applied to various forms of transportation, including public buses, delivery vehicles and airport ground support vehicles. It's also being used to power items such as video cameras, flashlights and other small electronics.

But real world experience is help guiding its development. From the back of a post office in a Virginia strip mall that includes a barbershop and a coin collector's store, Sisk takes the hydrogen vehicle, based on an Opel Zafira minivan, on his route three days a week.

"It drives like an ordinary car," Sisk said. The vehicle has a range of about 170 miles to 250 miles and a top speed of 99 mph, although Sisk said it's "not as fast on takeoffs" compared to a conventional vehicle.

In Albany, N.Y., deputy commissioner John Spano has two Honda fuel cell vehicles as part of the state's clean fueled vehicles program. The program, through the state's Office of General Services, has more than 5,000 alternative vehicles, including flexible fuel vehicles, hybrids, electric and vehicles fueled with compressed natural gas and propane.

When deploying the hydrogen vehicle, Spano said the agency does not "handle it with kid gloves at all." He said the Honda FCX has responded with strong performance, although it hasn't been used on long trips outside the state's Capitol region because of limited range and a lack of fueling stations around the state.

In 2004, Spano said the office had a couple of cases where the vehicle's range dropped to 70 to 80 miles in cold weather and one instance where the vehicle failed to start in temperatures of about 10 degrees. But otherwise, it's passed the test thus far.

"I drive an (Honda) Accord hybrid. There's absolutely no difference," Spano said. "It's quiet. It's quick. We really haven't had any complaints."

Cold starts and adjusting to hot desert climates are among the challenges the vehicles face, along with a price - about $1 million per vehicle - which does not make mass production feasible right now.

Scott Samuelson, director of the National Fuel Cell Research Center at the University of California, Irvine, said the main drawbacks involve the lack of an infrastructure of hydrogen fueling stations and the limited onboard storage of hydrogen in current models.

Most vehicles have a range of about 180 miles but the lack of fueling stations lead to a typical use range of about 110 miles, said Samuelson, whose program tests Toyota hydrogen vehicles.

California has launched an ambitious "hydrogen highway" to address the lack of fueling stations; the state has 16 hydrogen fueling stations and an additional dozen being developed, according to the National Hydrogen Association. In the U.S. and Canada, a total of 37 are now in use and another 22 are being developed within the next year and a half.

Energy companies are working to develop the hydrogen infrastructure necessary to fuel the vehicles. Chevron Corp. has two stationary fuel cells in San Ramon, Calif., and Houston which can convert hydrogen from natural gas into electricity, clean water and heat, and provide power to data systems and laboratories.

Donald Paul, Chevron's vice president and chief technology officer, said in testimony to a Senate panel Monday that the current fuel system took more than a century to develop, "and given the complexities, it is absolutely critical that both the fuel cell vehicles and the hydrogen infrastructure be developed simultaneously."

Automakers are pushing ahead. GM has introduced the Sequel concept vehicle, which is the first fuel cell vehicle capable of driving 300 miles between fill-ups. Ford has hydrogen-fueled shuttle buses in central Florida and is distributing Ford Focus fuel cell vehicles in the United States, Canada and Germany.

Nissan is developing its first in-house fuel cell stack and a high-pressure hydrogen storage system. Mazda is working on a hydrogen-fueled rotary-engine version of its RX-8 sports car.

"We believe this technology will simultaneously increase energy independence and security, remove the automobile as a source of emissions," said J. Byron McCormick, executive director of GM's fuel cells activities, "And allow automakers to create better vehicles that customers will want to buy in high volumes."
 

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