Fuelling a greener maritime industry

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Tuesday 1 March 2022 14:46 PM

Fuelling a greener maritime industry

The maritime industry is on course to becoming greener. Responsible for around 2.5% of global CO2 emissions, it’s the aspiration of many shipping companies, shipyard operators, and the Paris Climate Accord to enable the industry to help achieve the goal of limiting global warming to below 2^oC.

“The key enabler for greener shipping is the fuel,” emphasises Dr Daniel Chatterjee, Director of Technology Management & Regulatory Affairs at Rolls-Royce Power Systems.

While e-fuels – which are produced from renewable energy sources and subsequently refined – can be converted into propulsion power in ways that are climate-neutral, finding the right fuel for the maritime industry is a challenge we at Rolls-Royce have been tackling head-on.

The search for the right Power-to-X fuel

In recent years, our team of experts has been working with customers and partners to examine the entire fuel system – from fuel infrastructure, the cost of creating it and vessel range, to the propulsion system and its integration in the vessel.

All e-fuels share a much lower energy density than conventional diesel. This means that the weight and space requirement of fuel tanks increases with every e-fuel but not to the same extent for every type. The further the hydrogen produced via Power-to-X is processed and the closer the fuel comes to conventional diesel during processing, the higher the resultant energy density. However, these fuels are not 'zero emissions' when combusted.

Setting the standard for e-fuels

At Rolls-Royce, we’re committed to developing solutions that will achieve our climate targets and are focussing our efforts on methanol as a key power source for green shipping. We’ve already begun developing a high-speed, four-stroke engine optimised for methanol combustion.

“We want to be a pioneer here and set new standards with a methanol engine. After all, our customers need planning certainty, and we urgently need to work with them to create specific solutions to meet climate targets,” comments Denise Kurtulus, Vice President, Global Marine at Rolls-Royce Power Systems.

The benefits of methanol

Methanol has a high energy density compared to other sustainable fuels, and its liquid state means it's easy to store and refuel at ambient temperatures, making use of existing infrastructure. Unlike ammonia, methanol is environmentally safe and its combustion can be shown to be climate-neutral, obviating the need for complex exhaust gas after treatment.

Onboard, methanol tanks can be arranged flexibly in vessel designs and have significantly lower safety requirements than hydrogen or ammonia. In addition to safety aspects, methanol tank systems are less complex and require a lower investment outlay.

Methanol can also be used not just in diesel and spark-ignition combustion engines, but in conjunction with zero-emission fuel cells. This is an especially attractive proposition aboard ships where space is a premium commodity (or not available at all).

Hydrogen propulsion – when range is not an issue

Despite methanol’s positives, our developers have their eye on other options, including a hydrogen combustion engine for use aboard ferries and tugboats. On typically short, well-defined routes, these vessels are able to refuel frequently and can rely on fuel being available at their next port of call.

Range is also an important consideration for yachts which often sail in exotic locations where novel fuels like hydrogen or methanol are not always available. This is where diesel – and its net-zero cousin e-diesel – remain important options. Diesel will continue to be available at most ports and has a much higher energy density than hydrogen, while e-diesel can also be used in today's existing engines.

The time for action is now

Either way, Chatterjee is convinced: “We'll need to commit to a certain path in three to five years' time at the latest in order to achieve our overriding goal of making shipping climate-neutral by 2050.”

While this goal seems far off, preparations must begin now. Ships have service lives of anywhere up to 40 years. If the entire shipping industry is to be climate-neutral in 2050, the vessels in service must be planned today and any vessel entering service in 2030 should have climate-neutral propulsion.

Vessel architectures with hybrid systems

Alongside new and additional fuel requirements, the architecture of propulsion systems is also changing. Vessels powered solely by combustion engines are becoming less commonplace, while hybrid systems are now more popular.

“Our focus is on vessel architectures involving hybrid systems that are able to use combustion engines and fuel cells. Combustion engines are still being powered by diesel, but in the medium term they'll be running on methanol,” says Kurtulus.

The call for political support

Unfortunately, the huge demand for e-fuels coming from the maritime industry – the equivalent of around two trillion litres per year – cannot be met before 2030. While the technology is certainly available, it cannot yet be implemented on an industrial scale and political intervention is needed to enable infrastructure capable of supporting e-fuel ambitions.

“Advancing this and creating the framework for these fuels to find a market need the support of political decision-makers,” urges Chatterjee.