Pioneering turbocharger innovation to meet IMO decarbonisation targets

Overcoming combustion challenges

Ammonia is another strong contender as a zero-carbon fuel for shipping, although it presents its own set of technical challenges. Unlike hydrogen, ammonia has a relatively low combustibility and slow flame propagation, making it challenging to achieve complete combustion in marine engines. Accelleron’s turbochargers can be adjusted to deliver boost pressures according to combustion requirements, ensuring an optimal air supply for both diesel and Otto cycles.

Furthermore, ammonia combustion generates nitrogen oxides (NOx), which are regulated due to their harmful environmental impact. However, enginemakers can apply SCR technology, which injects a reducing agent like urea into the exhaust stream, converting NOx into harmless nitrogen and water vapour. The combination of calibrated turbocharging pressure and SCR supports ship operators in enabling the use of ammonia as a scalable low-emissions shipping fuel that could significantly accelerate progress towards meeting IMO’s ambitious emissions targets.

“Ammonia is corrosive to copper alloys”

Christoph Rofka, president of the Medium- and Low-Speed Division at Accelleron, notes: “Ammonia is corrosive to copper alloys. So, Accelleron conducted rigorous material tests. None of the tested materials showed a risk of a critical corrosion rate.” Mr Rofka adds: “To ensure safety and peak operation, turbochargers of forerunner engines operating with ammonia as a fuel are also inspected periodically for possible impact from combustion products and unburned fuel.”

Ammonia’s chief selling point is its scalability. Since safe ammonia production, storage, and distribution methods have already been well established for other industries, like agriculture, ammonia is likely to be the easiest carbon-neutral fuel to produce and use at scale. This is reflected in an increasing preference for ammonia, as ship makers place orders for a second wave of new ships designed to run on alternative fuels.

Cleaner combustion

Among alternative fuels, hydrogen theoretically offers one of the most promising solutions for zero-carbon operations when produced sustainably. However, in practice, it brings additional, unique challenges, due to its extremely low energy density per unit volume. This limitation means that turbochargers must operate at much higher-pressure ratios to provide adequate power output, especially important for long-distance marine voyages where energy efficiency is paramount. Accelleron’s turbocharger technology is designed to address these high-pressure demands, enabling efficient operations while supporting precise control over the air-to-fuel ratio.

This control is crucial because hydrogen combustion requires a delicate balance to avoid hotspots, which could lead to pre-ignition and subsequent wear on engine components. By allowing for this precise management, Accelleron’s turbochargers play a vital role in making hydrogen a viable fuel for maritime use.

Onboard storage is another major hurdle in practical sailing applications, and solutions for lowering the gas temperature to compress it enough to fit into a reasonable tank size are expensive and not yet proven.

However, since green hydrogen is the foundation for both green methanol and ammonia production, whether it is used as an operational fuel on its own or not, it will be vital to scale up its production over the next decades, to support the scale-up of methanol and ammonia.

Mr Rofka stresses that efficiency and flexibility are key for the practical application of any carbon-neutral fuel. Since carbon-neutral fuel supplies will continue to be limited and expensive for an indefinite number of years, efficiency will be critically important to making limited quantities more affordable for marine operators, helping the industry to move closer to IMO’s zero-emission goals.

Biofuels add another layer of complexity. Their combustion properties vary based on the feedstock used; for instance, biofuels from waste products may differ in ignition characteristics compared to other biofuels. Accelleron’s flexible turbocharger systems allow operators to adjust to these variations, ensuring efficient and consistent performance regardless of biofuel composition.

“Methanol presents challenges because of its lower energy density”

Mr Rofka points out that the global availability of biofuels is extremely limited. There is not enough biofuel potential in the world to support global shipping. So, it is generally not considered a viable fuel for long-haul shipping routes. It may be considered as a pilot fuel, in combination with another more scalable carbon-neutral fuel as the main propulsion fuel, to arrive at a 100% emissions-free voyage.

Flexibility in a multi-fuel future

One of Accelleron’s most impactful contributions to maritime decarbonisation is its commitment to flexibility in turbocharger design. During this transitional period in which multiple fuel types coexist, turbocharging flexibility ensures propulsion systems can perform optimally on any fuel, without the need for major system overhauls.

Accelleron’s next-generation turbochargers in the ACCX300-L series exemplify that principle, deploying a cartridge concept that allows the rotary elements of the turbocharger to be removed, as a whole cartridge or individually, and replaced at any port, no drydocking required. This will make maintenance more flexible and cost-efficient, allowing components to be replaced only as needed, independent of a rigid drydock schedule.

In addition, turbochargers have been tested and proven safe, robust, and efficient across the full range of conventional, transitional, and future carbon-neutral fuels. So, a dual-fuel vessel running primarily on LNG today can be converted to methanol or ammonia in the future using the same turbocharger platform.

That means that ship operators are not locked into a single fuel type, a crucial advantage as fuel infrastructure and availability evolve over time. and ship operators increasingly adopt alternative fuels based on both regulatory requirements and market availability.

Digital integration

Beyond hardware innovations, Accelleron is revolutionising marine propulsion through digital integration. The company’s Tekomar XPERT software represents a major advancement in this area, providing a digital platform that enables ship operators to monitor turbocharger and engine performance in real time. By utilising AI and machine learning, Tekomar XPERT analyses a range of turbocharging and engine parameters, providing actionable insights that enhance fuel efficiency and reduce emissions. This capability is particularly valuable for alternative fuels, where combustion properties can vary significantly.

Mr Rofka explains: “Accelleron’s Tekomar XPERT solutions address engines, hulls and propellers, and emissions. The engine module provides real-time information to the operator on engine performance, including insights to help optimise the engine for higher efficiency, resulting in fuel and CO2 savings.”

Mr Rofka continues: “Our Smartly Enabled Services also use operational data from turbochargers and engines to help individually optimise turbocharger maintenance, performance, and customer experience. Synthesising operational data with our 100 years of engineering expertise allows us to offer precise and in-depth insights, so that we can warn ship operators of potential issues and provide condition-based operational recommendations.”

Accelleron’s broad digital portfolio also includes emissions reporting, CII forecasting, voyage optimisation, and charter process support, from pre-voyage estimates to post-voyage claims, to support fleet compliance with environmental regulations. By providing real-time insights into fuel efficiency and emissions, the software enables operators to adjust for individual vessels and entire fleets, ensuring they remain within strict energy and emissions regulatory limits, for example those under the European Union Emissions Trading System and FuelEU Maritime. As these stepwise regulations become more stringent over time, digital tools will become increasingly useful to avoiding carbon excesses and fines.

Supporting decarbonisation

Accelleron’s technology is poised to play a critical role in the marine industry’s energy transition as IMO’s 2050 net zero emissions target approaches.

In a sector that is increasingly cost-sensitive as it faces growing environmental pressure, Accelleron’s approach offers solutions that fulfil both economic and ecological priorities. By prioritising fuel efficiency, adaptability, and digital integration, Accelleron’s innovations extend beyond meeting current emissions standards; they prepare the marine industry to operate successfully in a net zero future.