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.

Engineers collected measurement data when mowing the verge, accelerating, and refueling at a public gas station on a decommissioned section of the highway between Bayreuth and Bamberg.

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.

Enhanced Performance and Quieter Operation

The test vehicle for Mercedes-Benz Unimog is derived from the Unimog U 430 implement carrier.

It incorporates a specially converted natural gas engine, equipped with a tank, safety and monitoring systems, and measurement technology to accommodate an alternative hydrogen technology drive.

Hydrogen combustion within the engine compartment generates water, which is expelled as steam through the exhaust system.

The wheelbase and platform length are configured to allow installation of hydrogen tanks behind the cab. Four TÜV-certified high-pressure tanks, operating at 700 bars, collectively hold approximately 14 kilograms of gaseous hydrogen. These tanks are grouped into two double tanks, each independently managed by a tank control unit.

Engineers aspire to expand the volume in the upcoming development stage to cover a standard working day.

The engine produces around 290 hp/1000 Nm and is notably quieter than its diesel counterpart. For further insights into its operational mode, the prototype has a front mower featuring two mowing heads.

Advances Unimog's Future with Hydrogen Combustion Engine

Hydrogen Combustion Engine in "WaVe" Project" Daimler Truck is actively contributing to the "WaVe" project, a publicly funded initiative by Germany's Federal Ministry for Economic Affairs and Climate Protection, involving 18 partners from industry and science.

Launched in July 2021, the project aims to assess the potential substitution of a conventional diesel engine with a hydrogen-powered combustion engine, focusing on its applicability for traction drive and all power take-offs.

While Daimler Truck primarily concentrates on battery-electric drives and hydrogen-powered fuel cells, the "WaVe" project indicates that hydrogen combustion engines could be a sensible and complementary solution for specific applications in the decarbonization of Daimler Truck's drivetrain portfolio.

For the Unimog, especially, the hydrogen combustion engine emerges as a promising propulsion option due to limited installation space and the high-performance demands of this versatile vehicle.

Following a successful initial application, the development team anticipates six more months of adjustments and refinements to optimize this innovative mode of propulsion for the future.

Dr. Günter Pitz, Head of Powertrain Development at Mercedes-Benz Special Trucks: “The hydrogen combustion drive concept can serve as a blueprint for power-intensive applications in the specialty vehicle sector. Hydrogen combustion can make it possible to drive and work with very low emissions on construction sites, in municipal or agricultural sectors. To reach series maturity for such vehicles, reliable funding is and will be required.”