Researchers in Germany have recently unveiled a hydrogen-powered engine that could challenge diesel in some of the toughest applications by operating without emissions and achieving efficiency levels above 60 percent.

Developed by a research team at the Otto-von-Guericke University Magdeburg, the so-called hydrogen cycle engine operates in a closed loop and reuses most of its working gases after each cycle.

The project was led by Hermann Rottengruber, PhD, a professor at the university’s Institute for Engineering of Products and Systems (IEPS). It was also backed by the Federal Ministry for Economic Affairs and Energy of Germany.

“This approach could become particularly important in applications where engines must operate under high loads for long periods, be highly robust, and deliver significant power,” Rottengruber pointed out.

A zero emissions engine

The innovative concept utilizes a carefully balanced mix of hydrogen, oxygen and argon. While hydrogen serves as the energy source, oxygen enables the reaction, and argon, which is a chemically inert noble gas, acts as a stable carrier.

Because argon does not burn or react under operating conditions, it helps create more controlled thermodynamic conditions inside the engine. This, as a result, improves the system’s efficiency and stability.

Unlike a traditional combustion system, most of the gas mixture in this engine stays inside the system and is reused. It’s cooled, processed and fed back into the cycle after each power stroke.

The system removes only specific byproducts, while it separates and liquefies the hydrogen involved in the reaction. This unique design enables the engine to run without producing conventional exhaust emissions.

For the project, the team tested multiple variants of the so-called Argon Power Cycle engine on a dedicated test bench, along with their colleagues from WTZ Roßlau gGmbH, a research institute specializing in engine technology, energy conversion and future fuels. They also validated performance through detailed computer simulations.

Clean power solution

The results revealed that the engine could combine high output with exceptional efficiency (over 60 percent), as it is capable of delivering power levels comparable to those of diesel engines. This makes it especially attractive for heavy-duty applications where both performance and durability are critical.

These include sectors where battery-electric solutions often struggle as a result of weight, range limitations, and charging infrastructure requirements, such as long-haul trucks, agricultural machinery, construction equipment and stationary power generators.

But, according to Rottengruber, the closed-loop design could also offer economic advantages. “In our assessment, the closed system could be more cost-effective over realistic operating periods than an open hydrogen combustion engine,” he stated in a press release.

This, the expert believes, is partly because of the elimination of expensive exhaust treatment systems and the high efficiency of the process, which could offset the engine’s greater technical complexity over time.

Still, the current concept faces limits in power density, as only a certain amount of hydrogen can be injected during each cycle. The team also noted that the carbon dioxide could accumulate in the system, for instance, through the combustion of lubricants.