Hydrogen Truck Power Goes on Test

| Transport

Mercedes-Benz Special Trucks macht Dampf bei der Entwicklung eines Unimog Versuchsfahrzeugs mit Wasserstoff-VerbrennungsmotorMercedes-Benz Special Trucks is testing a Unimog prototype with hydrogen combustion engine

Mercedes-Benz Special Trucks has been testing a hydrogen combustion engine on a Unimog road maintenance vehicle

As part of Daimler Truck’s quest to explore the advantages of alternative fuels for its heavy haulage vehicles, Mercedes-Benz Special Trucks has been testing a Unimog implement carrier prototype with a hydrogen combustion engine in real operation.

The Unimog that’s undergoing the trial is a test vehicle that’s being 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 refuelling at a public fuel station. The data collected during the test will be used for further vehicle development. Employees from Autobahn GmbH accompanied the tests, which were conducted at low temperatures and in varied topography, an important step in the ongoing “WaVe” development project, in which 18 partners are working together on the hydrogen combustion engine drive concept for Mercedes-Benz.

Franziska Cusumano, Head of Mercedes-Benz Special Trucks and Custom Tailored Trucks is happy with the current development status of the test vehicle, which, after a two-year project term, is already in practical testing with the first operational Unimog prototype featuring a 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,” says Cusumano.

Converted engine

The Unimog test vehicle is based on the existing U430 implement carrier and uses a specially converted natural gas engine with tank, safety and monitoring systems as well as measurement technology 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 14 kilograms 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 the next development stage, engineers aim to increase the volume to be able to cover a regular working day. The engine delivers around 290 hp/1000 Nm and is noticeably quieter than its diesel equivalent. The prototype was equipped with a front mower featuring two mowing heads in order to gain further insights in work mode.

The WaVe project

The development of the hydrogen powered test vehicle is part of a publicly funded “WaVe” project. (WaVe derives from the abbreviations of the German words for Hydrogen – Wasserstoff – and combustion – verbrennung – ). Funded by Germany’s Federal Ministry for Economic Affairs and Climate Protection, the joint project involves 18 partners from industry and science and started in July 2021. The objective is to examine the extent to which a conventional diesel engine as a multi-energy distributor for the traction drive and all power take-offs can be substituted by a hydrogen-powered combustion engine.

For the Unimog, which is the Daimler Trucks platform for special vehicle fleets, this engine variant could prove to be a viable mode of propulsion for the future because of the limited installation space needed and the high performance required for operations involved with this type of vehicle.

After its first successful practical application, the development team is also looking forward to a remaining project duration of six months to make further adjustments and refinements.

According to 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 speciality vehicle sector.

“Hydrogen combustion can make it possible to drive and work with very low emissions on construction sites, as well as in municipal or agricultural sectors. To reach series maturity for such vehicles, reliable funding is and will be required,” he says.

Sustainable Drive Train Portfolio

Daimler Truck’s primary decarbonisation focus is on the use of battery-electric drives and hydrogen-powered fuel cells for heavier or longer range vehicles. In addition to these two technologies, hydrogen combustion can be another option for the decarbonisation of Daimler Truck’s drivetrain portfolio. Also, initial results from the WaVe project show that the hydrogen combustion engine can be a sensible, complementary solution for special applications.

On the preference for the use of hydrogen fuel cells over fully electric drivetrains for larger vehicles with longer range, Daimler Trucks CEO Martin Daun, recently said that the biggest problem is to get enough charging capacity for a truck. They need 300kw if charged overnight but you need a 700kw or 1MW charger to do it enroute or as a daily working process and this is one of the biggest problems Daimler if facing in electrifIcation so Hydrogen fuel cells provide a good alternative. For cars, the abilities of current battery technology are suitable for the application but not for heavier duty applications.

Making use of green energy

Daun says that Daimler Trucks is investing heavily in Hydrogen technology and a joint venture will put in place one of Europe’s largest production facilities for fuel cells. However, an important factor in the choice of Hydrogen is the need for the company to find a way to store and transport green energy.

To discuss this, Daun was recently in conversation with Dr Sopna Sury, the Chief Operating Officer of German energy company, RWE. According to Sury, to get to the point where Hydrogen can be used in such applications cost effectively, there needs to be a greater move to the use of renewables. This brings down the cost of production and consequently of electrolysis for producing green hydrogen. The aim is to get to the point where the cost of using H2 is no greater than the alternatives. “Hydrogen should be like tap-water, abundantly available in large volumes and in all different regions,” she says.

Analysis by Daimler Trucks shows that when comparing diesel, battery electric alternatives and H2, the price for H2 to be competitive needs to be around 4-5 Euros per kg, which is significantly lower than can be achieved at present.

A lot of factors affect the price and the ability to reduce it will be based on where the “electron” is produced (in wind farms, solar farms etc) and where the molecule “H2” is produced, transported and stored. Currently, there isn’t enough electrolysis capacity available for molecule production and the distribution of such facilities introduces transportation and storage challenges.

Sury explains that locally produced hydrogen will have low transportation costs but high production costs while H2 produced remotely in the middle east or USA for example will have much lower production costs but transportation across such long distances will require high costs associated with conversion into a transportable medium then re-conversion back to gaseous hydrogen at the point of use.

In terms of time frames, it’s unlikely to happen before the end of the decade. “A number of companies are now producing electrolysis equipment and there’s the possibility of having the infrastructure in place by the end of the decade but it needs the right flow of capital at appropriate times,” she says.

This fits in with Daimler’s timescales with the company expecting to have its current prototyping and testing phase over by 2027, at which point it expects to be gaining more experience with more trucks being produced in anticipation of commercial readiness by 2030.

Liquid or Gas

Daimler’s existing Hydrogen fuel cell truck, which recently completed a test run of 1000km on German public roads, uses liquid hydrogen, a choice made for technological reasons based on the higher energy density available from liquid hydrogen.

Daun says both forms work well and Daimler is able to produce trucks based on gaseous or liquid hydrogen with similar ease. He believes the choice will come down to fuel availability and the choice of the end user based on cost equations in terms of space savings on fuel tanks and the higher energy density versus the higher price of liquified fuel.

Sury believes that the main factor in the choice of fuel type will come down to the fuelling infrastructure that’s put in place. With the OGE (Open Grid Europe) project on the Continent, the plan is to have gaseous hydrogen available at dispenser points. “It is better therefore to use it in this form rather than go through an expensive liquification process at the point of use,” she says.

The equation has yet to be resolved and will be dependent on who is going to bear the costs, whether this is in the fuel distribution chain or at the point of use.

(The discussion between Daun and Sury can be heard in full in Daimler Trucks’ “Transportation Matters” podcast)

Jonathan Newell
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