On renewable paths

The Unimog WaVe is on its way to Upper Franconia, heading to Bayreuth. But not to the famous Wagner Festival — instead to a place that at first glance seems far less spectacular: a disused section of motorway. Yet on this stretch between Bayreuth and Bamberg something more spectacular is happening than you might think.

Namely, one of the first work deployments with a hydrogen-powered Unimog. A small step for Daimler Truck, a big one for the automotive industry.

More precisely, the trip to Bayreuth was a test drive by the vehicle developers with employees of the Autobahn GmbH to collect data for the hydrogen combustion engine in real-world operation. For this purpose, the Unimog WaVe was equipped with a front-mounted mower consisting of two mowing heads.

On the stretch of motorway near Bayreuth the prototype, modelled on the Unimog U 430 implement carrier, is to prove itself against its diesel-powered counterparts. Namely as a mobile mower. In low temperatures and over challenging terrain.

After mowing the motorway verge, acceleration runs follow and finally a refuelling stop at a public filling station. The measurement data will be useful for further vehicle development when it comes to bringing the climate-friendly alternative to the combustion engine into circulation.

"The tests with employees of Autobahn GmbH in Upper Franconia are particularly valuable to us, because we can feed important practical feedback directly into our development here," explains Franziska Cusumano, Head of Mercedes-Benz Special Trucks and Custom Tailored Trucks.

The Unimog WaVe is being developed as an experimental vehicle for a WaVe hydrogen combustion engine that could, in the long term, replace the conventional diesel engine. The WaVe project, funded by the Federal Ministry for Economic Affairs and Climate Action, started in 2021 and is being implemented jointly by a total of 18 partners from industry and science.

Initial results from the WaVe project have already shown that the hydrogen combustion engine could be a sensible, complementary solution to existing propulsion systems for specific applications. This is particularly true for the Unimog, which should continue to deliver its usual high performance within limited installation space.

In view of the positive test results and the development status of the Unimog WaVe, the head of Special Trucks has every reason to be pleased: "We are very satisfied with the current development status of the test vehicle. After just over two years of project duration we already have a first operational Unimog prototype with a hydrogen combustion engine in field trials." That is impressive.

The Unimog WaVe is equipped with a gas engine that has been specially adapted for hydrogen. It also features a special tank, safety, monitoring and instrumentation system. When hydrogen is burned in the engine, water is formed, which is then released as vapour.

The wheelbase and loading bed length of the Unimog WaVe were designed so that four TÜV-approved 700-bar hydrogen tanks can be accommodated behind the cab, which together store around 14 kg of hydrogen. Each pair of tanks can be controlled independently by tank control units.

In a future development phase the tank volume will be adjusted to the needs of a regular working day. The engine of the Unimog WaVe delivers a remarkable output of around 290 hp (1,000 Nm) and is noticeably quieter than its diesel equivalent.

After the Unimog WaVe successfully completed its first field test in Bayreuth, the development team has until the project’s conclusion at the end of July 2024 to put the finishing touches in place. Günter Pitz, head of powertrain development at Mercedes-Benz Special Trucks, has no doubt about the project’s future viability.

“The hydrogen combustion powertrain concept can serve as a blueprint for high-performance applications in the special-purpose vehicle sector. On construction sites, in municipal services or in the agricultural sector, it could enable very low-emission driving and working,” the engineer once again identifies the potential advantages of this propulsion type.

For Günter Pitz, support from the public sector as well as from private partners is indispensable: “In order to bring such vehicles to series maturity, continued financial predictability through targeted funding is still needed.” Where this is guaranteed, nothing less than a transformation of the German automotive industry can succeed—without having to forgo its decades-long expertise in the field of the combustion engine.

And the Unimog would once again be among the first.