Advocates of hydrogen-fuel-cell propulsion have a new target for their technology: trolleys. At the Fifth International Hydrail conference, held 11 and 12 June in Charlotte, N.C., engineers and transit planners concluded that streetcars are an ideal early application for hydrogen propulsion. Traditional trolley cars have drawn their power from catenaries, unsightly overhead electricity supply lines running along city streets. Hydrogen-powered streetcars will eliminate the wires, which otherwise might stand in the way of a streetcar comeback.
At first blush, streetcars may not seem worth devoting much effort to. Many Americans think of them as a quaint anachronism retained by a few cities like New Orleans for nostalgia’s sake. But more than a dozen municipalities around the world have restarted and extended trolley car lines because they attract wealthier riders than buses and inspire new, high-density property development. What’s more, streetcars—because of the low rolling resistance of steel wheels on rails—require much less energy than the rubber-tired buses that elbowed them aside decades ago. For these and other reasons, says the American Public Transit Association, some 50 cities in the United States are planning new streetcar lines.
Choosing a streetcar design based on hydrogen could save such municipalities millions of dollars per kilometer, say advocates. A 2006 assessment found that roughly one-quarter of the total cost of a planned 16-kilometer rail extension connecting the city and surrounding suburbs would have gone toward installing a catenary system, according to Brian Nadolny, interim project manager for the Charlotte Area Transit System (CATS).
Transit operators are cautiously optimistic about hydrogen-powered trolleys. ”If the technology is proven viable, it could revolutionize the industry,” says Keith T. Parker, CEO of Via Metropolitan Transit in San Antonio. Parker explains that in addition to saving the installation cost of a catenary system and support poles, the operator would save the maintenance costs.
”The biggest issue with [hydrogen trolleys] is that there isn’t one on the ground and running, so municipalities don’t have anything to test that would allow us to make a decision about whether to purchase one,” says Parker.
Proterra, in Golden, Colo., may be the first to deliver a prototype. It makes a plug-in hydrogen-electric hybrid bus with a battery pack that can be fully recharged in 10 minutes. The bus can travel roughly 50 to 70 km between charges, enough for 2 to 3 hours of operation.
Proterra’s system carries more batteries than hydrogen-fuel-cell stacks, because the system can draw most of the energy it needs for a day’s travel from the grid, charging periodically at high-voltage links when the bus is in service and via lower-voltage connections when it’s out of service. Hill says Proterra hopes to demonstrate to Charlotte’s CATS system the potential for turning the bus into a pseudo-trolley by putting it on steel wheels.
”The more widely the issue is discussed now and the sooner a proof-of-concept hydrogen trolley system is formally demonstrated, the smaller the risk that transit systems’ investments in overhead trolley planning will be for naught,” says H. Stan Thompson, chair of the hydrogen economy advancement team at the Mooresville–South Iredell (N.C.) chamber of commerce.
Of course, hydrogen fuel cells aren’t the only way to untether trolleys. Bombardier’s German subsidiary has rolled out a system based on contactless inductive transfer of electricity to pickup coils on a streetcar’s undercarriage from cables buried beneath the track bed. Shanghai’s Sunwin Bus Co. has fielded battery-powered trolleys that quickly draw power every few stops, extending an arm hidden on the top of the car. And Kawasaki Heavy Industry’s SWIMO light-rail vehicle travels 10 km or more between stops on a 5-minute charge of its Gigacell batteries.
The French firm Alstom pioneered the wireless streetcar movement with its Citadis tram, which went into service in Bordeaux, France, in 2003 and has cars powered by a segmented ground-level third rail. Only the segment that is completely covered by a train is electrified.