When visions ignite: methanol engine passes stress test

The powerful sound of the methanol engine fills the test bench as the indicator lights flash and the engineers watch the displays intently. Right in the middle of the action – behind a glass wall, but still right there – is Denise Kurtulus, Head of Marine Business at Rolls-Royce. She can hardly believe the moment: after years of development, the world's first high-speed single-fuel methanol engine with 2,000 kilowatts of power is running on the test bench.

"It's just overwhelming," she says, her eyes shining. "Six years ago, we started with a small group to think about methanol as a fuel for shipping. Now I'm standing here watching our engine actually run. I'm more than proud of our team – we've proven that CO₂-free marine propulsion with combustion engines is possible."

Methanol for the maritime energy transition: why this fuel is a good fit

Methanol offers exactly what shipping needs right now – practical decarbonisation without exotic technology:

• CO₂-neutral balance sheet: Green methanol is produced from CO₂ and green hydrogen or from plant residues. Although CO₂ is produced during combustion, only as much as was previously extracted from the air – which is why the balance sheet remains balanced. This is the difference to fossil fuels: the oil remains in the ground and no additional CO₂ is released.
• Clean combustion: No sulphur and significantly less nitrogen oxides and particles than in diesel fuel reduce the effort required for exhaust gas aftertreatment.
• Tank volume: Methanol has only about half the energy density of diesel. This means that twice as large tanks are needed to achieve the same range. Compared to other green fuels such as hydrogen or ammonia, however, methanol is more space-efficient.
• Easy handling and logistics: Unlike LNG, methanol does not need to be cooled; it is liquid at ambient temperatures and can be integrated into existing tank and bunker processes.
• Safety: Methanol is biodegradable, water-soluble and less explosive than LNG or hydrogen. This reduces environmental and safety risks in the event of accidents. 

In short, methanol is the viable lever for climate-friendly propulsion at sea.

Milestone in the network: MeOHmare drives methanol forward

The engine is being developed as part of the meOHmare research project – a joint venture between Rolls-Royce, injection system specialist Woodward L'Orange and the WTZ Roßlau technology and research centre. The joint project is funded by the German Federal Ministry for Economic Affairs and Energy. The goal is clearly defined: the methanol engine is to be tested on the test bench by the end of 2025.

Test on the test bench: stable running – now it's time for fine-tuning

The test hours completed so far show that the engine runs smoothly. At the same time, the engineers are learning more with each session.

"The engine behaviour differs significantly from that of a diesel engine. We are currently improving the settings so that the engine runs smoothly and accelerates cleanly under load," says Dr Johannes Kech, Head of Methanol Engine Development at Rolls-Royce.

The difference: injection, mixture formation, turbocharging

Methanol is not a drop-in fuel, meaning it cannot replace another fuel without modifications to the engine – and that is precisely where the art of engineering comes in:

• Injection: There were no off-the-shelf methanol injectors for this performance class. Together with their partners, Rolls-Royce engineers are developing hardware that is precisely metered and durable.
• Mixture formation: Since methanol does not lubricate as well as diesel, extreme pressures cannot be generated, which makes the necessary fine atomisation more difficult. The aim is to achieve a homogeneous, ignitable air-fuel mixture that burns cleanly and immediately at the spark plug.
• Air system & turbocharging: The combustion process is tailored to the specially designed turbocharging system – for clean combustion, fast revving and high efficiency across the entire operating range.

The result: performance, dynamics and clean methanol combustion are not mutually exclusive. The engine combines the dynamic response of high-speed diesel engines with a fuel that advances the maritime energy transition. For operators, this means familiar performance and a better carbon footprint.

Methanol: technology matures – infrastructure follows suit

As promising as methanol technology is for the maritime energy transition, it is also clear that the availability of green methanol is still limited at present. While the technology is making great strides and customer interest is huge, there is not only a lack of green fuel, but in many places also a lack of the necessary infrastructure to use methanol as a marine fuel across the board.

"I am convinced that the question is no longer whether methanol will arrive in shipping, but only when we will experience the breakthrough together," says Denise Kurtulus, adding: "The technology is ready, customers are interested – now we need the infrastructure and the political will to promote it."

The path to the fleet: single fuel as the goal, dual fuel as the bridge

To bridge the gap until green methanol is widely available, Rolls-Royce engineers are also testing dual-fuel engines as a bridge technology: these engines can run on 100 per cent diesel or a flexible proportion of methanol. This allows customers to remain flexible while improving their carbon footprint the more they drive with the highest possible proportion of methanol.

Outlook: From the test bench to the future

With the successful run of the full engine and the findings from the test bench tests, an important step has been taken. The next project phases will focus on system integration and fine-tuning for real-world application profiles.

What began quietly with a small idea now has a strong, loud and powerful-sounding technical foundation: the world's first high-speed single-fuel methanol engine makes the vision of CO₂-free shipping with combustion engines more tangible than ever before.