Scientists at the National University of Singapore present a ship engine that produces hydrogen in real time using a single ammonia tank.

• Global shipping → more than 80% of world trade.
• Engines with ammonia → hydrogen production on board.
• No cryogenic tanks → less complexity and costs.
• IMO 2050 Objective → decarbonisation of the naval sector.
• More efficient combustion → reduction of polluting emissions.
• Experimental technology → first tests in Singapore.
•  Realistic alternative → transition for large cargo ships.

 

How a Naval Engine Could Produce Hydrogen Offshore and Avoid One of Its Biggest Problems

 

Every year, international shipping moves more than 80% of world trade and generates nearly 1,000 million tons of greenhouse gases. The figure is impressive. And a lot. Despite the rise of renewable energies, a large part of ships continue to run on heavy fuel oil, an extremely polluting fuel that continues to dominate the sector due to its high energy density and reliability on long-distance routes.

 

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The pressure to change this situation is increasing. The International Maritime Organization (IMO) has set a goal of reaching net-zero emissions by around 2050, forcing shipping companies, ports and engine manufacturers to look for alternatives capable of operating for weeks at sea without compromising the safety and autonomy of ships.

 

That's where ammonia comes in. In recent years, this chemical compound has become one of the most serious candidates for decarbonising shipping. It has important advantages: it does not contain carbon, it can be stored relatively easily, and there is a global industrial infrastructure already prepared to produce and transport it.

 

But ammonia isn't perfect. It is difficult to light, burns slowly and can generate emissions of nitrogen oxides, gases with a strong climate and health impact. And of course, there appears another protagonist: hydrogen.

 

The problem of hydrogen on ships

Hydrogen burns quickly and cleanly. Mixing it with ammonia improves engine performance and helps reduce polluting emissions. The big obstacle is storing it.

 

To maintain liquid hydrogen, it is necessary to cool it to about -253 °C. It can also be compressed at very high pressures, although that involves huge, expensive, and complex deposits. On a merchant ship, where every cubic metre counts, dedicating space to these systems can be economically unfeasible.

 

This bottleneck has been slowing down the massive use of hydrogen in maritime navigation for years. Not because the fuel doesn't work. The real problem is how to store and transport it safely during journeys of thousands of kilometers.

 

Researchers at the National University of Singapore are now proposing a rather ingenious alternative: producing hydrogen inside the engine itself while the ship sails.

 

An engine that generates its own hydrogen

The study, published in the scientific journal Joule, proposes a concept of an ammonia-hydrogen hybrid engine that uses only ammonia as its main fuel.

 

The key is to transform part of that ammonia into hydrogen directly inside one of the engine's cylinders. Under the very high temperatures and pressures generated during combustion, a fraction of the ammonia breaks down and releases hydrogen. These hydrogen-rich gases are then recirculated to other cylinders to improve the overall combustion of the system.

 

In other words: the engine makes the hydrogen it needs while it is running.

 

And that changes the rules of the game quite a bit.

 

Until now, most designs have relied on external reformers, additional devices that heat ammonia to around 550 °C using expensive catalysts such as ruthenium to obtain hydrogen. They are bulky, complex systems with significant energy losses. In addition, they increase the maintenance and operating cost of the ship.

 

Singapore's proposal avoids much of that ancillary infrastructure. Fewer components. Less weight. Less space occupied. In navigation, that is worth gold.

 

Cleaner ignition and no auxiliary diesel

Another interesting aspect of the design is the active pre-chamber system used to initiate combustion.

 

Many experimental engines fueled with ammonia require small amounts of diesel to properly start combustion. The problem is obvious: even if emissions are reduced, the engine is still partially dependent on fossil fuels.

 

The technology developed by the Singaporean team uses a small chamber where a more flammable mixture is ignited. This combustion generates turbulent and extremely hot jets that allow the ammonia to ignite stably inside the main cylinder.

 

The result: the engine can be operated without the need for auxiliary diesel.

 

It may seem like a minor technical detail, although it has quite a climatic importance. Every litre of fossil fuel removed brings the maritime sector closer to carbon neutrality.

 

Fewer pollutant emissions and greater efficiency

Early simulations and experiments show promising improvements. The system could increase the engine's thermal efficiency and reduce problematic emissions such as unburned ammonia or nitrous oxide.

 

The latter is of particular concern. Nitrous oxide has a global warming potential about 273 times higher than carbon dioxide in the long term. Reducing it is a priority in any ammonia-based technology.

 

Interestingly, the researchers found that adding too much hydrogen doesn't help either. When hydrogen exceeds around 12% of the engine's energy input, efficiency improvements virtually disappear and combustion temperatures rise, leading to more nitrogen oxide emissions.

 

This fine balance between efficiency and emissions will be decisive in the commercial development of this technology.

 

A global race to decarbonise shipping

 

The shipbuilding sector is undergoing an accelerated transformation. Not only for environmental reasons. Also economic and regulatory.

 

The European Union has already partially incorporated maritime transport into its ETS emissions trading system, forcing shipping companies to pay for part of the CO₂ emitted. In addition, the FuelEU Maritime regulation will progressively incentivise fuels with a smaller climate footprint.

 

In parallel, shipping giants such as Maersk, CMA CGM or Mitsui O.S.K. Lines are investing billions in vessels capable of operating with green methanol, ammonia or hydrogen.

 

South Korea, Japan and Singapore are positioning themselves as technology hubs for future marine fuels. In fact, Singapore – one of the most important ports on the planet – has long been committed to becoming an international hub for the supply of low-carbon fuels.

 

All this accelerates interest in flexible engines capable of adapting to different fuels for decades to come. Because the transition will not be immediate. There will be a mix of technologies coexisting for a long time.

 

Potential

Maritime navigation needs realistic solutions, not just futuristic ideas that are difficult to apply outside the laboratory. And this type of engine points precisely in that direction.

 

If the next prototypes work properly in real-world conditions, hybrid ships capable of using green ammonia could emerge with lower operating costs and less technical complexity. This would facilitate the energy transition of the sector without relying exclusively on batteries, something that is not feasible today in large ocean-going vessels.

 

In addition, technologies such as this could be integrated with other measures already in place: modern auxiliary sails, digital route optimisation, commercial speed reduction, port electrification or carbon capture systems on board.

 

There is no single magic solution. Shipping will need to combine many.

Still, getting an engine to produce its own hydrogen in the middle of the ocean... Well, that's already starting to look like a pretty important piece of the climate puzzle.

 

Source:  Fuel Cells Works