MAN Engines

Hydrogen engine: a climate-friendly alternative

Hydrogen for combustion engines as a climate-friendly alternative
in focus

Hydrogen engine: a climate-friendly alternative

Hydrogen can make combustion engines locally climate neutral. MAN has decades of experience in this area and is developing solutions for mobile and stationary applications.

Hydrogen is considered the energy source of the future because this gas only leaves behind water vapour when it is burned, making it climate neutral. In fuel cells, hydrogen can be used to generate electricity for an electric drive. However, combustion engines can also use it as an alternative to conventional diesel for various applications – for example, in the maritime or agricultural sectors, as well as in logistics.

Hydrogen engines in logistics and in the off-road sector

MAN has had a truck prototype powered by a hydrogen combustion engine since 2021. The core element is a 16.8 litre hydrogen engine with a power of over 500 hp and 2,500 Nm of torque based on the modular diesel engine system. The expected service life is comparable to that of conventional diesel engines – even when using low-grade hydrogen. The integration of hydrogen pressure tanks into existing vehicle concepts enables a range comparable to that of a conventional vehicle with the same payload.

MAN trucks with hydrogen tanks
The space for hydrogen tanks must be considered when designing the vehicle.
Kässbohrer snow groomers can be operated with hydrogen
On the slopes with hydrogen: off-road vehicles such as Kässbohrer snow groomers could switch to this climate-friendly fuel.

Off-road applications can also benefit from climate-friendly hydrogen. The MAN D3876 diesel engine is currently driving the PistenBully 800 from Kässbohrer Geländefahrzeug AG, whereby HVO can also be used as a fuel in addition to conventional diesel. When designing the PistenBully 800, the developers thought further ahead and the powerful snow groomer is prepared for the future integration of a hydrogen combustion engine (MAN H4576) and provides the interfaces necessary for this purpose, as well as space for hydrogen tanks. The MAN H4576 is based on the basic engine of the MAN D3876 and around 80 percent of the parts are identical.


There are significant changes to the assemblies for hydrogen supply and combustion, engine control and exhaust gas regulation. Compared with the MAN D3876 diesel engine, the bore has also been increased from 138 millimetres to 145 millimetres while retaining the same stroke of 170 millimetres. This results in a larger engine displacement of 16.8 litres, compared with the 15.3 litres of the MAN D3876. The torque and power output of the hydrogen combustion engine therefore come close to the values of its diesel counterpart.

Sustainable change: from diesel to hydrogen engines

H4576 hydrogen internal combustion engine contains modified components
man-engines-sustainability-wasserstoffverbrennungsmotor-1-16x9.jpg

Ignition system

The high ignition limit ratio of hydrogen means that rapid ignition is required to ensure efficient combustion. The specially aligned ignition system takes these properties into account and enables reliable and controlled external ignition of the hydrogen mixture.

man-engines-sustainability-wasserstoffverbrennungsmotor-2-16x9.jpg

Exhaust gas aftertreatment

This reduces the nitrogen oxides generated through the combustion of hydrogen. The exhaust gas aftertreatment is based on the diesel engine system and has been adapted to the requirements of the hydrogen combustion engine. The Euro VII emission standard is met with the hydrogen combustion engine and exhaust gas aftertreatment.

man-engines-sustainability-wasserstoffverbrennungsmotor-3-16x9.jpg

Engine control unit

Among other things, it controls the supply of hydrogen and air, regulates injection and ignition, and continuously adjusts the engine parameters to enable reliable and efficient combustion.

man-engines-sustainability-wasserstoffverbrennungsmotor-4-16x9.jpg

Turbocharger

The higher engine displacement and the modified combustion process compared with the MAN D3876 diesel engine result in an altered air requirement and different exhaust gas temperature. The new turbocharger helps to achieve optimal performance values, and thereby also to reduce consumption.

man-engines-sustainability-wasserstoffverbrennungsmotor-5-16x9.jpg

Hydrogen supply

The hydrogen supply in the hydrogen engine comprises the system made up of new low-pressure lines and a rail, which together supply the injector with the required hydrogen. The hydrogen requirement is dosed via precise pressure control to ensure efficient combustion and to provide an optimal fuel supply for the engine.

man-engines-sustainability-wasserstoffverbrennungsmotor-6-16x9.jpg

H2 injector

The hydrogen injector is used for low-pressure direct injection with a pressure of up to 40 bar. It is fitted directly in the combustion chamber to achieve higher performance and better engine response.

man-engines-sustainability-wasserstoffverbrennungsmotor-7-16x9.jpg

Piston/liner

In contrast to the diesel engine, the hydrogen engine requires new pistons and liners because hydrogen has a lower lubrication capability than diesel fuel. In addition, the pistons are equipped with a piston recess and their diameter is increased to 145 mm. With the resulting higher engine displacement, an output similar to that of the MAN D2676 diesel engine is achieved at 500 hp (368 kW).

Highly efficient electricity generation with hydrogen engines

MAN Engines is currently researching the potential of stationary hydrogen engines in the field of combined heat and power (CHP) at the engine test station in the Nuremberg Engine Competence Centre. At the centre they are running an eight-cylinder MAN H3268 V engine with a bore of 132 millimetres and a stroke of 157 millimetres. As a stationary engine, it is operated at a constant speed of 1,500 rpm at 50 Hz. It is very similar to the MAN E3268 V8 natural gas engine – after all, both combustion engines are based on the same base engine that has been used in many thousands of natural gas and special gas engines for years.

Various aspects including the turbocharging, the injectors and the mixture preparation have been adapted for operation with hydrogen. “Thanks to the similar geometry and identical connections of our future hydrogen engines, we can already offer our customers products that are H2-ready. This simplifies the conversion of existing systems from operation with natural gas to hydrogen,” explains Jürgen Haberland, Head of Power MAN Engines.

When it comes to output, the developers of the MAN H3268 are also guided by the MAN E3268 natural gas engine, which offers 370 kWmech. The aim here is to achieve a high power density, i.e. to provide a high output in a compact space. “Our objective is for the hydrogen engine to achieve a similar power class to our natural gas engine,” says Werner Kübler, Head of Development at MAN Engines. “In essence, we are improving our existing natural gas engine by converting it to a hydrogen engine. When operated with green hydrogen, it produces electricity and heat highly efficiently – 100 percent locally CO2-neutral.”

Stationary hydrogen engines make combined heat and power generation more sustainable
Among other things, MAN Engines is researching stationary hydrogen engines that make combined heat and power generation even more sustainable.

Hydrogen in combination with diesel or HVO

Hydrogen can also be used in combination with conventional diesel or alternative fuels such as HVO. A first practical example already exists, namely the twelve-cylinder V engine MAN D2862, which has been driving the wind farm supply ship Hydrocat 48 as a hydrogen dual-fuel engine since mid-2022. At low speeds, up to 80 percent of the diesel can be replaced by hydrogen, and around 50 percent is still possible at medium and high speeds. This makes a big impact when it comes to emissions because at typical speeds of 22 to 25 knots, 54 to 66% of CO2 tail-pipe emissions are prevented and nitrogen oxide emissions are reduced by 30 to 40 percent.

  • Pioneering hydrogen combustion engine for off-road applications

At Agritechnica 2023, MAN Engines presented an innovative hydrogen combustion engine for off-road applications that sets new standards. The groundbreaking technology marks a significant step forward in the industry and underlines MAN Engines' commitment to sustainable solutions. The newly developed engine not only offers powerful features, but also demonstrates the company's commitment to promoting environmentally friendly drive alternatives in the off-road sector.

Learn more about this groundbreaking development in the official press release.

To the press release

Header image: © iStockphoto/Evgeniy & Karina Gerasimovi