Evan Whitlock said he only noticed one difference after test driving one of the even dozen hydrogen-powered cars that were roaming the University of Washington, Bothell campus on June 2.

“It was very smooth, very quiet” he said. “You couldn’t even hear the engine.”

Another driver, Dustin Greene, said the car he drove made it up a hilly part of the campus circuit “no sweat,” and again, with no noise. Green said he hopes to own one of the cars someday.

“I want my next car to be something different and these are definitely different,” he added.

Sponsored by the California Fuel Cell Partnership, the Hydrogen Road Tour stop at UW-Bothell was the 25th in a 28-city tour that ended in Vancouver, B.C. The tour featured hydrogen-powered cars from numerous big-name manufacturers, ranging from Honda to Nissan to GM.

Nissan’s Brian Johnston said the hydrogen used to fuel the new-fangled cars actually feed fuel cells, which generate electricity, which then powers the vehicles. He added the easiest way to think of a fuel cell is as a type of battery, not one that stores energy, but one that creates it.

Basically, Johnston and others said that, using platinum as a catalyst, the fuel cells rip negatively charged electrons off the hydrogen. It is the electrons that are converted into electricity. Oxygen is the only other byproduct of fuel-cell operation and, in this case, it eventually makes its way out a car’s tail pipe as water.

“These are true zero-emission vehicles,” Johnston said.

According to information provided by the fuel-cell partnership, fuel cells currently are used in everything from fork lifts to space shuttles. But there are several challenges connected with moving the technology into your driveway.

“They’re expensive,” Nissan’s Robert Harran said of the hydrogen cars. He and others added there also is no infrastructure in place for refueling the cars. For the tour, the California Partnership had to haul hydrogen with them in tanker cars. About five kilograms of hydrogen are needed to fill the Nissan, providing enough juice to move it about 250 miles.

Not incidentally, working near the filling station, technician Jason Bowman said fueling the cars is perfectly safe. Visitors were even invited to gas up the cars themselves. Once the hose is hooked in, fueling is done automatically, the flow cutting out when the tank is full.

“You don’t have to stand there and pump the gas,” Bowman said. “You can go get your cup of coffee while it’s doing its thing.”

What are some of the sources for hydrogen? Chris White of the California Partnership said natural gas provides an easy supply. But she also noted widespread use of natural gas for cars would be trading one non-renewable, fossil fuel — namely, oil — for another.

Instead, White talked about collecting hydrogen naturally produced at sewer plants, paper pulp mills and similar industrial operations, among other possible sources any one of which greatly would reduce dependence on foreign oil.

With all the differences between fuel-cell vehicles and traditional combustion cars, Johnston admitted your neighborhood mechanic is unlikely to have any idea of how to work on a fuel-cell car.

But Johnston added the California Partnership and others eventually want to work with dealers, community colleges and trade schools to train fuel-cell mechanics.

While all of those connected with the tour said there are roadblocks to getting hydrogen cars to consumers, all also were optimistic it can happen.

“These vehicles are just years from market, not decades,” White said.