The expo was organized by the U.S. Fuel Cell Council, a trade organization, and Rep. Nancy L. Johnson, as a publicity exercise and educational seminar for members of Congress and their staffs. It was a quiet riot of banners, flyers and gismos of all sizes, whirring and clicking and humming in the decidedly low-tech caucus room of the Cannon House office building.

At another display table set up by the Department of Energy, government scientists displayed an actual fuel cell powered computer mounted in a large steel suitcase, like the ones silver-screen secret agents might handcuff themselves to.

Outside, a bright blue bus powered by a battery and a 75-kilowatt fuel cell designed by South Windsor-based UTC Fuel Cells ferried passengers around the Capitol building until D.C. bicycle cops pulled it over and scolded the driver to stay away from congressional buildings. A line of similar buses using UTC fuel cells began serving tourism areas in Palm Springs, Calif., last November.

Buses are easier than cars, says UTC Fuel Cell’s Vice President of Operations Jim Bolch. There are fewer size constraints on a bus than a car. And the infrastructure is easier to manage – the buses have a range of about 250 miles, so they can run all day and return to a single depot at night to re-fuel on compressed hydrogen.

Plus, chimed in UTC press secretary Peter Dalpe, the cells can’t really handle sub-freezing temperatures yet. So California was probably a practical place to start.

Several other companies are also experimenting with phasing fuel-cell vehicles into public transportation, as well as pursuing the glittering dream of the Zero Emission Car.

Brian Walsh of Breakthrough Technologies Institute described how the fuel cell vehicle industry is becoming a race for commercial viability among a stable of different low-emission fuel cell systems: gaseous hydrogen, solid hydrides, liquid methanol and clean gasoline. The winner will be the system that can deliver both the vehicle and the infrastructure affordably, reliably – and first. But technological hurdles remain, he said.

Gregory A. Dolan, a vice president at the Methanol Institute, another trade organization, explained that methanol fueling stations would be much cheaper to build than hydrogen fueling stations. Methanol is so toxic, he said, that scientists have had to design a special vapor-proof pump to make it impossible for the consumer to come in contact with the raw fuel. He proudly displayed a model. It looked like a gas pump.

Transportation is far from the only application of fuel-cell technology. Johnson highlighted the potential of fuel-cell power generators in homes to transform the nations energy supply.

Currently, Johnson noted, power plants constantly produce electricity at near maximum surge levels. If Americans had fuel-cell power plants in their homes, the nation’s energy supply could be tailored to community and individual needs.

Danbury-based FuelCell Energy has already started by building trailer-sized power plants run by natural gas for commercial and industrial facilities. Director Andrew J. Skok said they are the world’s first fully commercial fuel cell product. They’re not quite turning a profit yet, he said, but that will come soon.

UTC has a similar project installing prototype power plants in two Connecticut high schools.

Despite common predictions citing the years 2020 or 2030, Dalpe insists that UTC can get fuel cell bus lines commercially viable by 2006.

The number of bills with financial incentives for fuel cell development that have already made it through Congress shows that government interest in fuel cells has been high – but it could be higher, Johnson said.

“You need to get out there and educate,” she shouted to conventioneers. “America moves fast, when its knowledge base is good.”

Kenneth L. Rubow, of the Mott Corporation, in Farmington, said the government has already helped. Mott is a small shop with perhaps 150 employees that produces parts and materials for fuel cell companies, including UTC. The benefits of government programs, he said, have filtered down even to small local technology companies like Mott, in terms of increased business and demand for parts.

Johnson said the upcoming energy bill would provide further tax breaks for fuel cell research, particularly for residential power units.

“Government doesn’t move,” she said, “the private sector moves.”

But the best part, she added, strolling past the remote controlled cars and the vapor-sealed methanol pumps, was seeing how many more companies were at the expo than in previous years.