A hydrogen power unit lets electric trains run without overhead wires, where only 57% of the European rail network is electrified

A hydrogen power unit lets electric trains run without overhead wires

A hydrogen power unit lets electric trains run without overhead wires, and HERMES is the version ALTPRO built, without changing the locomotive itself. HERMES stands for Hydrogen Repowering Management System. ALTPRO, a Croatian railway signalling company with more than 30 years in the business, unveiled HERMES at InnoTrans 2026, a rail industry trade fair held in Berlin, Germany, from September 22 to 25, 2026, the 30th anniversary edition of the fair. HERMES is a hydrogen power system built into a standard railway wagon, a rail car that carries the hydrogen tanks and the fuel cell. A fuel cell is a device that makes electricity from hydrogen and oxygen without burning anything, with water as its only waste. That electricity feeds an existing electric locomotive as traction power, the same power an overhead wire would otherwise supply. The locomotive itself needs no modification, and keeps its pantograph, the arm that reaches up to draw power from a wire, for use on the parts of a route that already have one.

We developed a system that addresses this challenge by using hydrogen, while at the same time recognising its potential beyond railways, in energy, industry and critical infrastructure.

Tin Viduka, Board member at ALTPRO, speaking about why HERMES was built. Source 1.

HERMES refuels at a hydrogen station, or by swapping its hydrogen container, a 20 foot storage unit, for a fresh one. ALTPRO has not stated a power output, a hydrogen storage capacity, or a driving range for HERMES. The company says on its own product page that renting a fleet of HERMES units costs an infrastructure manager multiple times less in upfront capital than wiring the same route, without stating a number for either side of that comparison. No test line, launch customer or country has been named for where HERMES will actually run in service.

How much of the European rail network already has overhead wire

ALTPRO frames HERMES as an answer to a gap that is not unique to Croatia. The company states that only about 40% of the rail network in Croatia is electrified, against an average of about 57% across Europe. A calculation made for this article puts the German rail network at about 60% electrified, subtracting from 100 the 40% the German industry association VDE states remains unelectrified as of September 2025. VDE itself states only the unelectrified share, not a share already electrified, so the 60% figure is a derivation, not a number the association states directly. The 40% figure for Croatia and the 40% figure for Germany describe opposite things by coincidence, one counts what has wire and the other counts what does not, not the same measurement in 2 countries.

Why the missing wire matters more on some German track than others

In Germany, the wiring gap is not spread evenly across how the network gets used. VDE, the German association of electrical, electronic and information technology industries, states that 90% of German rail traffic runs on just the 62% of the network that already carries overhead wire, a figure the association published in September 2025. That concentration is the same one HERMES targets, letting an electric locomotive add traction power on the smaller, less used share of track that still has none.

What still stands between a hydrogen power unit and wider use on unwired track

ALTPRO has shown a working idea, not a finished commercial deployment. The company has named no power figure, no cost figure and no country where HERMES will run in service. What it has confirmed is a system that lets an existing electric locomotive draw power from a hydrogen wagon instead of a wire, on exactly the kind of track that the Croatia, Europe and Germany figures above show still has none.