Hydrogen in the wheels: German firm tackles the storage problem holding back hydrogen tractors

Where do you store enough hydrogen on a tractor without sacrificing space, balance, or functionality? German engineering company Hörmann Vehicle Engineering has an answer that is as logical as it is unexpected: inside the wheels themselves. The company has unveiled a concept integrating ring-shaped carbon fibre tanks directly into the rear wheel rims of tractors. Operating at 700 bar, the tanks can together store up to 42 kilograms of hydrogen — roughly equivalent to 200 litres of diesel in usable energy.

The storage problem

Even at high pressure, hydrogen's volumetric energy density is significantly lower than diesel. That makes physical storage space on a working machine a limiting factor in a way it simply isn't for conventional fuel. The Fendt Helios — the hydrogen tractor developed by Fendt/AGCO as part of Germany's publicly funded H2Agrar project in Lower Saxony — illustrates the challenge clearly. The tractor runs on five roof-mounted tanks, each holding 4.2 kg of hydrogen at 700 bar. Together, those 21 kg provide enough fuel for 5 to 8 hours of field operation per fill. That is workable, but not sufficient for a full day under intensive conditions.

The H2Agrar project — launched in February 2021 with approximately €7.6 million in state funding from Lower Saxony — is Germany's first end-to-end demonstration of hydrogen in agricultural use. Green hydrogen is produced by two 1 MW electrolysers fed by a local community wind farm of 16 turbines near Haren. The Fendt Helios tractors now operate on real farms in the Emsland region as part of ongoing data collection.

The solution: the wheel as a tank

Hörmann Vehicle Engineering approaches the storage problem from a different angle. Large agricultural tractor wheels are substantial structures with considerable internal volume that currently serves only mechanical and structural purposes. By converting that idle volume into functional energy capacity, the concept uses space that would otherwise go to waste.

The ring-shaped tanks are made from carbon fibre-reinforced composite and are embedded in the rear wheel rims, operating at 700 bar with a combined capacity of up to 42 kg of hydrogen — twice the storage of the Fendt Helios's roof solution. That should be sufficient for a full working day without refuelling, bringing the hydrogen tractor closer to practical parity with diesel equipment.

There is an additional benefit to weight distribution: placing fuel close to the axles rather than on the roof improves machine balance on uneven ground. The system is modular and compatible with both hydrogen internal combustion engines (H2-ICE) and fuel cell powertrains, meaning manufacturers can integrate it without redesigning the entire tractor architecture.

Still at concept stage?

An important caveat: whether the concept has reached prototype stage has not been confirmed in available sources. The engineering challenges are real — any hydrogen storage system in a rotating wheel must manage fuel transfer, pressure integrity under continuous mechanical stress, and safe refuelling access. Hörmann has indicated it is working on safety measures including thermal relief valves and impact sensors, but independent validation data have not yet been published.

Agriculture as an overlooked decarbonisation challenge

Agricultural machinery accounts for around 8.5% of total emissions in German agriculture. That may seem modest, but it represents a significant volume at the scale of European agricultural production. Battery-electric is not a realistic option for heavy field work due to weight and charging time constraints. Hydrogen is the most promising alternative powertrain for these applications — provided on-board storage becomes practical enough. That is precisely the problem Hörmann is trying to solve.

Sources:

- Hörmann Vehicle Engineering / AgInsights (04-04-2026): https://www.aginsights.blog/hormann-introduces-new-wheel-integrated-hydrogen-storage-system-to-deliver-full-day-tractor-autonomy-without-chassis-redesign/

- Daily Galaxy / Fuel Cells Works (03-04-2026): https://dailygalaxy.com/2026/04/germany-made-tractor-hydrogen-wheel-storage/

- Fendt H2Agrar (official): https://www.fendt.com/int/h2-fendt-helios-tractor-on-display-as-part-of-german-hydrogen-week-2024

- H2-Mobile.fr (11-04-2026): https://www.h2-mobile.fr/actus/reservoirs-hydrogene-roues-tracteurs-non-routiers/