Mercedes-Benz WaVe Project: Unimog with Hydrogen Combustion Engine in Test

Mercedes-Benz Special Trucks has tested a Unimog carrier vehicle prototype with a hydrogen combustion engine under real conditions. According to the manufacturer, the aim of the test vehicle is to investigate the conditions under which the hydrogen combustion engine can complement battery-electric and fuel cell-based drives.

“We are very satisfied with the current development status of the test vehicle,” summarizes Franziska Cusumano, Head of Mercedes-Benz Special Trucks and Custom Tailored Trucks, regarding the current state of testing. “After a good two years of the project duration, we are already in practical testing with a first functional Unimog prototype with a hydrogen combustion engine. The tests conducted with the employees of Autobahn GmbH in Upper Franconia are particularly valuable for us, as we can directly incorporate important feedback from practice into our development.”

For this purpose, the engineers collected measurement data on a closed-off highway section between Bayreuth and Bamberg while mowing the green strip, during acceleration drives, and while refueling at a public pump, which will be incorporated into further development of the vehicle. Employees of Autobahn GmbH accompanied the tests. The practical testing at low temperatures and varied topography is an important step in the ongoing development project Wave, in which 18 partners are working together on the drive concept of the hydrogen combustion engine, according to the company.

The test vehicle with retrofitted engine

The Mercedes-Benz Unimog test vehicle is based on the Unimog equipment carrier U 430 and features a gas engine retrofitted specifically for alternative hydrogen technology drive, with tank, safety and monitoring systems, and measurement technology. During hydrogen combustion in the engine compartment, water is produced, which escapes as hot water vapor from the exhaust.

The wheelbase and platform length are designed so that the hydrogen tanks could be mounted behind the cab. The four TÜV-tested 700-bar high-pressure tanks hold a total of around 14 kilograms of gaseous hydrogen. They are combined into two double tanks, which can be operated independently via separate tank controls. In the next development stage, the volume is to be increased to cover a normal working day. The engine delivers approximately 290 HP / 1,000 Nm and is significantly quieter than its diesel counterpart. The prototype was equipped with a front mower with two mower heads to gain further insights in work usage.

Projekt Wave: Collaboration between Politics, Science, and Industry

The development of the experimental vehicle with a hydrogen combustion engine is taking place as part of the publicly funded project WaVe. The project, funded by the Federal Ministry for Economic Affairs and Climate Action, is being implemented jointly by 18 partners from industry and science and started in July 2021. The project aims to investigate to what extent the conventional diesel engine can be replaced by a hydrogen-powered combustion engine as a multi-energy distributor for vehicle propulsion and all auxiliary drives.

Focus mainly on battery-electric drive

Although Daimler Truck's focus is mainly on battery-electric drives and hydrogen-powered fuel cells, the combustion of hydrogen could represent another option for decarbonizing the drive portfolio, explains Daimler Trucks. Initial results from the project WaVe have shown that for special applications, the hydrogen combustion engine can be a useful complementary solution.