Gif: Birmingham Centre for Railway Research and Education/IEEE Spectrum HydroFlex at a rail testing center in Warwickshire, England, in June 2019.
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The United Kingdom’s first hydrogen fuel cell train rolled down the tracks this week, marking a milestone in the global push for greener transportation. Passengers climbed aboard the HydroFlex prototype as it ambled through the English countryside—without emitting any of the pollution that follows diesel locomotives.
HydroFlex is a joint initiative of the University of Birmingham’s Centre for Railway Research and Education (BCRRE) and Porterbrook, the British railway company. The team demonstrated the four-car train at a rail testing center in Warwickshire, where rail aficionados gathered for an industry event. Researchers say they plan to test HydroFlex on the main U.K. railway network later this year, with funding from the Department of Transport.
“In the next few years, we could certainly see a fleet of these operational in the U.K.,” Stuart Hillmansen, a senior lecturer in electrical energy systems with BCRRE, said in a video at the rail conference.
As countries and cities work to improve air quality and combat climate change, railways have become another frontier for zero-emission technologies. Many rail systems around the world still rely on diesel-electric powertrains, resulting in soot, smog, and carbon emissions. In the U.K., transport officials recently vowed to eliminate the nation’s diesel-only locomotives—about 3,900 trains—by 2040.
To curb diesel use, railway operators can electrify networks with overhead catenary lines or conductive third rails. (About one-third of the world’s track-miles are already electrified; in Europe, Japan, and Korea, the percentage is higher: about 60 percent.) However, converting existing tracks can be prohibitively expensive, particularly where long-distance and low-use networks require new infrastructure. As the costs of fuel cell modules and batteries continue to decline, hydrogen trains are gaining traction.
In Germany, two such trains entered into passenger service late last year. Alstom, the manufacturer that made them, recently announced it will build 27 more of its Coradia iLint trains for European tracks, and it’s developing a separate model for the United Kingdom. Japan and South Korea are planning hydrogen trains, and in the United States, local officials in California and North Carolina are pursuing projects to convert passenger trains.
“Economically, they (fuel cells) can make sense today, where they couldn’t a number of years back,” says Guy McAree, director of investor relations for Ballard Power Systems in British Columbia, Canada. The manufacturing company supplied the fuel cell system for HydroFlex and is working on hydrogen rail projects in Germany and China.
HydroFlex is a hybrid model, designed to draw most of its power from overhead lines or third rails, with the fuel cell kicking in where neither option exists, according to BCRRE. Of the four cars on the converted Class 319 train, one holds all the good stuff: a 100-kilowatt proton-exchange membrane fuel cell module; 200-kW of lithium-ion batteries; and 20 kilograms of hydrogen, stored in four high-pressure tanks.
Hydrogen is piped into the fuel cell, which then pulls oxygen from the air to create electricity. That in turn powers the traction motors beneath the passenger cars, with additional electricity stored in the battery bank. Unlike diesel locomotives, the system doesn’t emit any sulfur dioxide, nitrogen oxides, or greenhouse gases—just a little heat and water.
“It’s a very smooth and quiet ride,” says Andreas Hoffrichter, a professor in railway management at Michigan State University, who hopped on HydroFlex earlier this week. He helped develop BCRRE’s original prototype, Hydrogen Hero, as a doctoral student in Birmingham. When we spoke on Thursday, he’d already made his way to another hydrogen rail conference, this one in Germany.
Fuel cell systems on trains can vary depending on the power demand profile, he says. Light rail and commuter trains frequently start and stop, so it makes sense to have a relatively larger battery and a smaller fuel cell. This also benefits the regenerative braking system, which recharges the batteries. For long-distance and freight trains, which make fewer stops, a larger fuel cell and smaller battery system are a better fit.
Across the sector, fuel cell modules are virtually the same on trains, buses, ferries, and heavy-duty trucks. The main differences are in the supporting components and structural designs that accompany the systems, says Buz McCain, director of systems engineering at Ballard.
For instance, when designing for rail, engineers must account for constant vibrations as trains move down the tracks and dampen the shocks that result from connecting and disconnecting cars. Unlike HydroFlex, other hydrogen trains store their fuel cells on the roof to free up cargo and passenger space; this requires stringing multiple modules together across a flat, trapezoidal surface.
However, the biggest challenge facing hydrogen trains goes beyond the tracks. Hydrogen refueling infrastructure is lacking worldwide, though transportation officials in the U.K. and elsewhere are working to install more refueling stations and deploy more fuel trucks. Hydrogen producers are likewise working to ramp up supplies—and to develop cleaner production methods, such as using renewable energy to split water molecules.