This week's U.S. debut of Volkswagen's zero-emission, hydrogen-powered Tiguan Hymotion sport-utility in the Bay Area illustrates both the promise and the pitfalls of a type of alternative-fuel vehicle that many automakers are developing.

Hydrogen vehicles offer a clean alternative for the nation's highways and a way to ease our dependence on the gasoline engine, proponents say. That's important as motorists face record gas prices and the world confronts climate change caused by carbon emissions from cars and other sources.

But electrical glitches prevented the Tiguan from running at the opening of the new Capitol Volkswagen in San Jose, and at a news media event in San Francisco on Thursday. (VW execs said those problems were unrelated to the hydrogen technology but show that the cars are still a work in progress.)

A more serious challenge facing VW and other car manufacturers is the lack of hydrogen stations. Indeed, company executives said VW could be as much as a decade away from putting a hydrogen car into production because of infrastructure deficiencies.

"The issue that you come up against," said Mark Barnes, chief operating officer of Volkswagen of America, "is we can produce it, but where are consumers going to refuel?"

Gov. Arnold Schwarzenegger's ambitious plan for a statewide network of hydrogen stations called the Hydrogen Highway, unveiled more than four years ago, has been slow to materialize. The chair of the state's Air Resources Board now says 50 to 100 hydrogen fueling stations will be open by 2015, five years later than originally promised.

VW, which has a research lab in Palo Alto, won't put fuel-cell cars into production until hydrogen is "readily accessible" nationwide, Barnes said.

That will take seven to 10 years, perhaps more, said John Tillman, who heads VW's fuel-cell research program at the California Fuel-Cell Partnership in Sacramento.

Fuel cells produce electricity by taking hydrogen and oxygen, separating protons and electrons, and routing electrons to create an electrical current that powers the vehicle's motor. The only emission is water.

VW officials said the Tiguan Hymotion has run well during hundreds of miles of testing in Germany and California. But overuse prior to the Bay Area event led to battery glitches, they said.

General Motors and Honda have more aggressive plans than VW for introducing hydrogen cars.

GM's Project Driveway program has rolled out 80 Chevy Equinox fuel-cell vehicles, including 49 in California, for short-term test drives, spokesman Pete Barkey said.

Meanwhile, Honda will begin production of its FCX Clarity fuel-cell vehicle Monday in Japan, spokesman Sage Marie said.

Honda plans to lease about 200 FCX Clarity models in Southern California over three years at $600 a month, with the first leases starting in July. More than 50,000 people have expressed interest via Honda's Web site, Marie said.

The Clarity sedan has a 270-mile range and gets the equivalent of 68 miles per gallon.

While hybrids, plug-in hybrids and diesel cars get most of the attention today, hydrogen technology continues to make progress, said John Addison, who publishes the Clean Fleet Report.

But, Addison said, "There's a question mark over the next 10 years of how well it may do with consumers because both automakers and the average consumer want to see a nice, available infrastructure for filling up."

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FAST FACTS ABOUT VW'S TIGUAN HYMOTION

_What: Prototype sport-utility vehicle.

_Power: Makes 107 horsepower from the vehicle's hydrogen fuel-cell stack. An electric motor boosts horsepower to 134. A lithium-ion battery stores energy. The Tiguan's tank can hold 3.2 kilograms of hydrogen.

_Fuel economy: The equivalent of 42-62 mpg, VW says. The gasoline-powered Tiguan gets 18-19 mpg/city and 24-26 mpg/highway, depending upon the model. The diesel Tiguan, not sold in the United States, gets 33-34 mpg.

_Fuel cost: San Jose's Valley Transportation Authority says the cost of fuel for its three experimental hydrogen buses is $2.86 per mile vs. 56 cents per mile for its diesel buses. Conversely, Honda said the cost of hydrogen for its Clarity vehicle would work out to about $2 per gallon equivalent.

_Performance: 0 to 60 mph in about 14 seconds. The gas version gets up to that speed in less than 8 seconds.

_Price: Priceless. The Tiguan Hymotion is hand-built, and only two exist. The gas version of the Tiguan sells for $23,200-$32,940. A production version of the fuel-cell vehicle would probably have the same several-thousand-dollar premium of a hybrid over a comparable gasoline car.

_About the name: Readers of a German auto magazine got to name the Tiguan, a hybrid of the words tiger and iguana.

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© 2008, San Jose Mercury News (San Jose, Calif.).

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