How does a hydrogen train work?

Put simply, it burns nothing. Hydrogen stored in roof tanks flows into a fuel cell, where it reacts with oxygen pulled in from outside air and produces electricity. A battery holds braking energy and helps on take-off. The motors do the rest, and what comes out of the vent is water vapour.

Introduction

Jind isn't a town most people link with new technology. Yet on 17 July 2026, India's first hydrogen passenger train pulled out of its station, bound for Sonipat. No diesel engine. No overhead wire. Within eight days it had run over 1,200 km and saved more than 3,200 litres of diesel, according to Indian Railways.

We get asked about it a lot, mostly by students and faculty. How does a hydrogen train work, really? The fuel cell part is easy to explain. What surprises most people is how much of the train is about everything else: tanks, batteries, converters, cooling. So that's where we'll start.

Key Components of a Hydrogen Fuel Cell Train

Six systems, give or take. On most designs the tanks go on the roof, the traction gear goes under the floor, and cooling pipes run between the two.

Look down that list again and you'll notice what isn't there. No engine block, no exhaust stack, no pantograph. On a line nobody ever wired, that absence is the whole point.

How the Hydrogen Fuel Cell Works

The type you'll find on nearly every passenger train is PEM, short for proton exchange membrane. It's a film of polymer, thinner than paper, pressed between two platinum-coated electrodes. Hydrogen goes in on one side. Air goes in on the other.

On the hydrogen side, the anode, platinum pulls each molecule apart into protons and electrons. The membrane is picky. Protons get through, electrons don't, and they're forced the long way round through an external circuit. That detour is your electric current.

The two meet again at the cathode, along with oxygen from the air, and form water. A fair bit of heat comes off too.

One cell on its own gives you 0.6 to 0.8 V under load. Hardly anything. You need hundreds of them in series before a traction inverter is interested. And there's a catch students spot quickly on a test bench: draw more current and the voltage drops, sometimes steeply. So stacks get sized for the worst moment on the route, usually a full train on an uphill grade.

Onboard Hydrogen Storage

Hydrogen is light, which sounds helpful until you try to carry enough of it. Per litre, there's very little energy in the gas. The fix is pressure, typically 350 bar and sometimes 700. India's Jind train carries 27 hydrogen cylinders and manages about 250 km between fills. CRRC's CINOVA H2 crams in up to 316 kg at 70 MPa.

Is that safe? It's the first thing people ask, and the engineering answer comes in layers. Sensors near the tanks, pipes and stack watch for hydrogen and close the supply valves if they catch any. If a cylinder overheats, relief devices vent the gas upward. The cylinders themselves are usually Type 4 (a plastic liner with carbon fibre wound over it), tested against drops, impacts and fire.

India's trainset adds its own detection for leaks, heat, flames and smoke. Hydrogen's lightness helps here, oddly enough. A leak shoots upward and thins out fast, so roof-mounted tanks make a lot of sense.

Battery Buffer and Power Electronics

Look closely and every hydrogen train in service is really a hybrid. There's a lithium ion pack sitting next to the stack. Why bother, if the fuel cell already makes power?

• Braking. As the train slows, its motors start generating, and that current has to go somewhere. Into the battery, ideally.
• Starting from a standstill. Leaving a station takes a big burst of power for a short time, and the battery supplies most of it.
  
• Keeping the stack happy. Fuel cells wear out faster when the load keeps jumping around, so the battery takes the jumps instead.

Builders don't agree on chemistry. Jind's train uses lithium iron phosphate. CRRC went with a 366 kWh lithium titanate pack alongside four 240 kW fuel cells on the CINOVA H2.

Tying it all together is the power electronics. A DC to DC converter boosts the stack's wandering output up to a fixed DC link. An inverter then makes three-phase AC for the motors, at whatever frequency the speed calls for. Power has to flow both ways, into the battery on braking and out of it on a climb. Getting that control loop stable is, in our experience with lab setups, where students lose the most hours.

Drive Train and Traction Motors

Crawl under one and you'd struggle to tell it apart from a normal electric multiple unit. That's really what it is. An electric train that brings its own power station along.

The motors drive the axles through a single-stage gearbox, and two kinds are in common use. Induction (asynchronous) motors are tough, affordable and have been on electric trains for decades. Permanent magnet synchronous motors weigh less and run more efficiently at part load. They also cost more and need rare earth magnets, which is why plenty of operators haven't switched.

The motor doesn't know, or care, whether its current came from a fuel cell, a battery or a wire overhead. Handy if you're a student. Learn traction drives once and the knowledge travels with you.

Step by Step: How a Hydrogen Train Moves

Put together, here's how a hydrogen train works in practice, tank to wheel.

• Hydrogen leaves the storage tank, passing through a regulator that knocks the pressure down.
• It enters the fuel cell stack on the anode side. A compressor pushes filtered air into the cathode side.
• The fuel cell reaction produces electricity, as DC.
  
• The power electronics send the electricity to the motor and battery, rebalancing many times a second.
  
• Motors on the powered bogies take that current and turn the wheels through a gearbox.
  
• On acceleration the battery tops up the power, and on braking it takes energy back.
  
• The only exhaust is water vapour. On a cold morning you can actually see it.

Hydrogen Train vs Diesel Train vs Electric Train

How does it stack up against diesel and conventional electric? Roughly like this.

We'd be doing you a disservice if we skipped the downside. Hydrogen loses energy at every hop: electrolysis, compression, then the fuel cell itself. Put an electric train under wires and it will use far less electricity for the same trip. Hydrogen earns its place where there are no wires.

Real World Hydrogen Train Examples

Germany got there first. Alstom's Coradia iLint started carrying passengers in Lower Saxony in September 2018, with a top speed of 140 km/h and about 1,000 km on a tank.

China came at it from the city side. CRRC Changchun's urban hydrogen train touched 160 km/h in 2024 testing, and CRRC claims more than 1,000 km of range.

And then Haryana. Indian Railways' Jind to Sonipat train, ten coaches and built in India, has run daily since July 2026. It's capped at 75 km/h in service but has done 120 km/h in tests.

Why Hydrogen Trains Matter for India

Most articles skip an awkward fact. By November 2025, Indian Railways had wired up 99.2% of its broad gauge network. Only 574 route km were left. Diesel on the main lines is on its way out regardless.

So where does hydrogen fit? Think of the hill railways, metre and narrow gauge sections, heritage lines and quiet branch routes where nobody can justify catenary. That's the thinking behind Hydrogen for Heritage, which plans 35 hydrogen trains.

Then there's the 2030 deadline. Indian Railways has promised to be a net zero carbon emitter by 2030, and diesel units count against it. Where the hydrogen comes from matters a great deal here. Jind makes its own by electrolysis. Gas-derived grey hydrogen would just push the carbon further up the chain.

For a student trying to understand how a hydrogen train works, Jind is a gift: electrolysis, fuel cells, converters and storage, all in one system.

Conclusion

So, how does a hydrogen train work? Hydrogen in, electricity out. A battery covers the peaks, motors turn the axles, and the vent puffs out water vapour.

Honestly, most of this clicks faster on a bench than on a page. Electrolysis is easy to see in a green hydrogen lab. Stack behaviour under load shows up quickly in a fuel cell lab, especially when students plot their first polarisation curve. And the battery and converter juggling? A microgrid lab covers that well.