Unimog meets crawler: From hydrogen project to operational use

The development of two hydrogen combustion engines has been successfully completed…

The goal on the road to CO2-neutrality is to drive and work without emissions. Not only fully electric vehicles can help in this, but also other alternative drive systems. The two-year project, which was funded by the German Federal Ministry for Economic Affairs and Climate Protection, has now come to an end.

Mercedes-Benz Special Trucks and Mörtlbauer presented their duo: Unimog and crawler. Both vehicle prototypes have a hydrogen combustion engine. Both machines are already very much at work.

The Unimog device carrier has been using this drive system in various tests for more than a year, while the crawler has been working in the first specific tests since spring 2024. At the presentation, the Unimog drove the crawler on a low loader trailer. A small test drive using the device was carried out on the Mörtlbauer factory grounds, and the charging process was shown to the public.

With minor adjustments, the hydrogen combustion engine can be used much like today’s diesel engines. In both models, a medium-power engine provides propulsion, and engineers have modified it to run on hydrogen. All that was needed were custom pistons, a hydrogen supply system and optimized ignitions. The water produced by combustion goes out through the exhaust system into the atmosphere.

Four high-pressure tanks of 700 bar in total can receive about 13 kilograms of gaseous hydrogen in the Unimog. 290 hydrogen horsepower and 1000 Nm of torque are comparable to the 300 horsepower diesel variant. This must allow all additional devices to work without problems. The crawler receives 14.5 kilograms of hydrogen also at 700 bar, which makes it possible to move up to 16 cubic meters of content at 30 tons.

These two prototype vehicles show how low-emission driving and operation, with consistently high engine power, can be achieved in the future together with purely electric vehicles. The hydrogen combustion engine (WaVe) development project started in July 2021 in cooperation with 18 partners from industry and science.