Mercedes-Benz Special Trucks has tested a Unimog implement carrier prototype with a hydrogen combustion engine in real operation.

The Unimog is a test vehicle that is used to research the conditions under which hydrogen combustion can be implemented as a supplement to battery-electric and fuel-cell-based drives. On a decommissioned section of the highway between Bayreuth and Bamberg, engineers collected measurement data when mowing the verge, accelerating and refueling at a public gas station. The data will be used for further vehicle development.

Employees from Autobahn GmbH accompanied the tests. Practical testing at low temperatures and in varied topography is an important step in the ongoing “WaVe” development project, in which 18 partners are working together on the hydrogen combustion engine drive concept.

Franziska Cusumano, Head of Mercedes-Benz Special Trucks and Custom Tailored Trucks, said: “We are very happy with the current development status of the test vehicle. After a good two-year project term, we are already in practical testing with the first operational Unimog prototype featuring hydrogen combustion engine.

“The tests with Autobahn GmbH staff in Upper Franconia are particularly valuable for us because here we can collect important feedback from practical application for the further development work,” he said.

The Mercedes-Benz Unimog test vehicle is based on the Unimog U 430 implement carrier. A specially converted natural gas engine with tank, safety and monitoring systems as well as measurement technology is installed for the alternative hydrogen technology drive. Hydrogen combustion in the engine compartment produces water, which is discharged as steam via the exhaust system.

The wheelbase and platform length are dimensioned so that the hydrogen tanks can be installed behind the cab. The four TÜV-certified, 700-bar high-pressure tanks hold a total of around 14kg of gaseous hydrogen. They are combined into two double tanks, each of which is operated independently of each other with a tank control unit.

In a next development stage, the engineers aim to increase the volume to be able to cover a regular working day. The engine delivers around 216kW (290hp) and 1000Nm and is noticeably quieter than its diesel equivalent. The prototype was equipped with a front mowerfeaturing two mowing heads in order to gain further insights in work mode.