Hydrogen Train Technology

The rail industry is undergoing its most significant propulsion shift since the transition from steam to diesel in the mid-20th century. For decades, diesel locomotives have been the workhorses of non-electrified tracks, but they come with heavy carbon footprints and noise pollution. Hydrogen fuel cell technology is now emerging as the primary alternative, offering a clean, quiet solution that emits nothing but condensed water.

This shift is not theoretical. From the rolling hills of Lower Saxony in Germany to the test tracks of Pueblo, Colorado, hydrogen trains are actively replacing diesel engines. This technology allows rail operators to decarbonize lines where installing overhead electric wires is too expensive or logistically impossible.

The Science of Hydrail: How It Works

Hydrogen trains, often called “hydrail,” function much like electric trains but generate their own electricity onboard rather than drawing it from an overhead catenary wire or a third rail.

The process relies on a device called a fuel cell stack, typically mounted on the roof of the train. Here is the basic chemical process:

• Storage: Hydrogen gas (\(H_2\)) is stored in high-pressure tanks on the train.
• Reaction: The hydrogen is fed into the fuel cell, where it mixes with oxygen (\(O_2\)) taken from the outside air.
• Conversion: Inside the cell, a catalyst separates the electrons from the hydrogen atoms. These electrons flow through a circuit, creating an electric current that powers the traction motor and charges onboard lithium-ion batteries.
• Exhaust: The hydrogen protons migrate through a membrane and recombine with oxygen and the electrons to form pure water (\(H_2O\)) and steam.

The batteries act as a buffer. They store excess energy generated by the fuel cell and capture kinetic energy during braking (regenerative braking). When the train accelerates or climbs a hill, the battery provides the extra power needed to assist the fuel cell.

Europe: Leading the Charge with Alstom

Europe is currently the global leader in commercial hydrogen rail operations. The geography of the European rail network makes it an ideal candidate for this technology. While main lines are electrified, roughly 40% of the European network still relies on diesel.

The Coradia iLint in Germany

The biggest success story so far is the Alstom Coradia iLint. In August 2022, the world’s first 100% hydrogen-powered train route began operation in Lower Saxony, Germany. The route connects the towns of Cuxhaven, Bremerhaven, Bremervörde, and Buxtehude.

A fleet of 14 Alstom trains replaced 15 older diesel locomotives. The switch saves approximately 1.6 million liters of diesel fuel and eliminates 4,400 tons of CO2 annually. These trains have a range of 1,000 kilometers (about 621 miles) on a single tank, allowing them to run all day without refueling.

Expansion to Italy and France

Following the German success, Italy has moved aggressively. FNM (Ferrovie Nord Milano), the main transport group in the Lombardy region, ordered six hydrogen fuel cell trains from Alstom for use in the Valcamonica valley. This area is known as the “Italian Hydrogen Valley” and aims to integrate hydrogen power into both industrial and transport sectors.

France is also deploying the technology across four different regions (Auvergne-Rhône-Alpes, Bourgogne-Franche-Comté, Grand Est, and Occitanie), with orders for dual-mode trains that can switch between overhead electric power and onboard hydrogen power.

The United States: Breaking Records and Starting Service

While the US rail network is vast and heavily freight-dominated, passenger rail authorities are beginning to adopt hydrogen for commuter lines.

The Stadler FLIRT H2

The most prominent player in the US market is Swiss manufacturer Stadler. They have developed the FLIRT H2, a train specifically designed for American railways.

In March 2024, the FLIRT H2 set a Guinness World Record for the longest distance traveled by a hydrogen fuel cell electric passenger train without refueling or recharging. The test took place at the Transportation Technology Center in Pueblo, Colorado. The train traveled an astounding 1,741.7 miles (2,803 kilometers) over 46 hours on a single tank of hydrogen.

San Bernardino’s ZEMU Project

The first commercial application of this technology in the United States is the “ZEMU” (Zero-Emission Multiple Unit) project. The San Bernardino County Transportation Authority (SBCTA) ordered the FLIRT H2 for its Arrow passenger rail service.

This train will operate between San Bernardino and Redlands, California. This nine-mile route is crucial for demonstrating that hydrogen can handle the stop-and-go nature of American commuter transit. The train arrived in San Bernardino in mid-2024 for final testing.

California’s Intercity Push

Beyond local commuting, the California Department of Transportation (Caltrans) has signed a $127 million contract with Stadler for four hydrogen trainsets, with options for 25 more. These are intended for intercity routes in the Central Valley, specifically connecting Merced and Sacramento. This indicates a state-level commitment to moving away from diesel on state-supported Amtrak routes.

The Economic and Infrastructure Reality

The primary driver for choosing hydrogen over traditional electrification is cost. Electrifying a railway (installing poles, overhead wires, and substations) costs between $2 million and $5 million per mile. For rural or low-traffic routes, this capital expenditure is difficult to justify.

Hydrogen trains run on existing tracks without requiring modification to the rails. The cost is shifted from track infrastructure to the train itself and the refueling stations.

However, challenges remain:

1. Fuel Sourcing: The environmental benefit depends on how the hydrogen is made. “Green hydrogen” is made using renewable energy (wind/solar) to split water. Currently, most industrial hydrogen is “grey,” made from natural gas, which still has a carbon footprint.
2. Transport and Storage: Hydrogen is less dense than diesel. It requires large, high-pressure tanks or cryogenic storage (liquid hydrogen) to achieve comparable range.
3. Refueling Stations: Unlike diesel depots which are everywhere, hydrogen refueling infrastructure is scarce. Operators like the SBCTA have to build dedicated fueling stations alongside the tracks.

Frequently Asked Questions

Is hydrogen rail safe? Yes. Hydrogen tanks on trains are rigorously tested for impacts and crashes. Hydrogen is lighter than air, so in the event of a leak, it dissipates upward rapidly, reducing the risk of ground-level fires compared to pooling liquid diesel.

How fast can hydrogen trains go? The Alstom Coradia iLint has a top speed of 140 km/h (87 mph). The Stadler FLIRT H2 is capable of similar speeds. While they are not high-speed bullet trains (which require overhead wires for massive power draw), they are perfectly capable of handling regional and commuter speeds.

Why not just use battery-electric trains? Batteries are heavy and have lower energy density. A battery-only train is great for short hops (under 50 miles) or bridging gaps between electrified sections. For routes over 60 miles without overhead wires, hydrogen offers the range and refueling speed necessary to replace diesel.

Does cold weather affect hydrogen trains? Generally, fuel cells perform better in cold weather than pure battery systems, which lose significant capacity in freezing temperatures. The heat generated by the fuel cell reaction can also be used to warm the passenger cabin, increasing overall efficiency.