Interview with Ammonia Engine Expert

Q. Due to the uncertainty surrounding fuel options in the shipping industry’s path to carbon neutrality, it is expected that various fuels, rather than a single dominant one, will be used. How do you assess the importance of ammonia fuel among these alternative fuels?

A There are several fuels being considered for greenhouse gas (GHG) reduction, including biofuels, LNG, methanol, ammonia, and hydrogen. In the transition to carbon-neutral fuel for shipping, the share of each fuel may vary depending on the ship owner or type of vessel. However, LNG is expected to continue being used, and biofuels will likely serve as transitional fuels. That said, the limited production of biofuels may restrict the amount available for maritime use, leading to the potential use of various e-fuels (e-LNG, e-Methanol, e-Diesel) based on green hydrogen.

Ammonia, on the other hand, is expected to be less costly to produce and to have fewer production limitations than other fuels. Given its well-established bunkering and supply infrastructure, if operational safety for ship propulsion can be ensured, ammonia could have a competitive advantage over other fuels. This is also true for hydrogen. While hydrogen may seem like the ideal fuel, if its transportation challenges, due to the need for cryogenic conditions for liquefaction and its low energy density, are not resolved, ammonia is likely to hold a competitive edge under current conditions.

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Q. There is significant interest in HD Hyundai’s HiMSEN ammonia dual-fuel engine. Can you share the current development progress?

A The world’s first 4-stroke H22CDF-LA engine, which uses high-pressure ammonia combustion, completed its type approval test with classification societies in October. The HiMSEN ammonia engine has been developed with the goal of achieving high output and reducing greenhouse gas emissions by more than 90%. Additionally, our 2-stroke main propulsion ammonia engine also employs a high-pressure system. When used together with the HiMSEN ammonia engine, the fuel supply systems for ships become simplified, which is another advantage. Next year, we plan to expand our ammonia dual-fuel engine portfolio by conducting classification type approval tests for the HiMSEN H32CDF-LA engine.

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Q. The shipping industry is curious about the flow rate of pilot oil in 2-stroke and 4-stroke ammonia engines. Some argue that using traditional diesel as pilot fuel may prevent these engines from being fully carbon-neutral. What is HD Hyundai’s target for pilot oil quantity in upcoming engine type approval tests, and are you considering biomass-based carbon-neutral pilot fuels?

AWhile the use of a certain amount of pilot fuel is inevitable, we are striving to minimize the amount of pilot fuel in the HiMSEN ammonia engine to maximize GHG reduction. Since using diesel as the pilot fuel would prevent the engine from being truly carbon-neutral, we are preparing to use biofuels that meet the International Maritime Organization’s (IMO) carbon-neutral fuel standards as pilot fuel. For example, our methanol HiMSEN DF engine has been proven to ignite using biofuels and has been validated on ships.

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Q. The industry has noted that you recently developed the world’s first 4-stroke methanol engine in a short period of time and are now close to conducting actual type approval tests for a high-pressure ammonia engine. What has been the driving force behind shortening the development period for these engines?

A We have accumulated over 30 years of design expertise with HiMSEN engines and have cultivated excellent R&D personnel through our Engine Research Institute within the Engine & Machinery Business Unit. By building on the platform of HiMSEN engines, which dominate the 4-stroke market, we have focused on optimizing new technologies for green fuel supply and injection systems.

In addition, close collaboration with Advanced Research Center of Korea Shipbuilding & Offshore Engineering (our parent company) and networking with leading domestic and international universities and research institutions, including KR (Korean Register), has helped us enhance the engine's completeness and safety while shortening the development period.

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Q. There is a lot of curiosity about the emissions from ammonia engines, including concerns over ammonia slip and the emissions of nitrous oxide (N₂O), which has a high global warming potential. To address these issues, it seems that an aftertreatment systems are ready during engine development. Could you introduce the methods you’ve established for reducing and managing emissions in the HiMSEN ammonia engine?

AWe are paying close attention to emissions during the development of ammonia engines. While maximizing efficiency was the key focus for previously developed engines (LNG, diesel, etc.), the priority for ammonia engines is to minimize nitrous oxide emissions and reduce ammonia slip, or ensure that any unburned ammonia is removed in the aftertreatment system.

Other developers of 2-stroke engines are known to follow a similar strategy. HiMSEN ammonia engines are continuously improve the engine performance and reduce the unnecessary emissions generated such as slip of Ammonia with nitrous Oxide. We effort to make a high efficiency combustion to find the minimize emission levels. At the moment the actual test results cannot veil but we can support to the customer to establish their strategies.

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Q. Can you explain the safety philosophy behind the HiMSEN ammonia engine?

A Whilst there is limited experience in operating ammonia engines, there are learnings from other fueled engines. For example, the HiMSEN ammonia engine uses double-walled fuel supply piping and purging systems, similar to other low-flashpoint fuel engines. Additionally, ammonia slip is minimized by the engine itself, and the ammonia concentration is further reduced after passing through the aftertreatment system.

We are also working to make the HiMSEN ammonia engine easy to operate and maintain, with a user-friendly design.

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Q. Once ammonia engines are developed, improvements may still be necessary. How do you plan to address such issues?

A Several methanol-powered ships equipped with methanol engines are currently in operation. We receive feedback from ship engine manufacturers and shipyards regarding the performance, safety, and stability of these engines, which helps address any issues and establish the product in the market.

Even after receiving type approval from the classification society, HiMSEN methanol engines continue to undergo performance and durability improvement tests. Any necessary improvements will be communicated to shipowners. We expect a similar process for ammoniapowered ships and engines.

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Q. Ammonia fuel is expected to play a significant role in global decarbonization. How do you view the competition between ammonia fuel cells and ammonia engines?

A It is generally true that fuel cells are more efficient than internal combustion engines. While solid oxide fuel cells (SOFCs) could be applied to medium-to-large vessels, they lack the acceleration performance of internal combustion engines. Therefore, in electric propulsion ships, a hybrid propulsion system might be considered, where 4-stroke internal combustion engines manage the load fluctuations caused by changes in operating conditions, while SOFCs handle the base load.

However, for medium-to-large vessels, the key challenge for the expanded application of electric propulsion systems will be how to minimize the cost and space required for SOFC installation. Even though SOFCs are more efficient, their efficiency would still be lower than 2-stroke internal combustion engines when accounting for electricity conversion losses, which would need to be offset by new technologies. SOFCs may be applied in the short term as supplementary power (PTI), but their inherent challenges must be addressed. Also, if ammonia SOFCs are used, the efficiency losses due to reforming would need to be considered.

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Q. After developing the ammonia engine, the next step seems to be hydrogen engines. HD Hyundai has already completed the development of LNG-hydrogen co-combustion technology. Could you tell us about your plans for hydrogen engine development?

A Hydrogen engines are expected to be used as propulsion for hydrogen carriers. This year, we plan to test a hydrogen-diesel cocombustion engine, and we are preparing to test a fully hydrogen engine in the near future. Recently, we started a government R&D project with KR and others to develop a hydrogen injector. Once the hydrogen engine is developed, we expect to complete our lineup of engines for all alternative fuels.

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Q. Lastly, what recommendations or advice would you give to shipowners and engineers regarding ensuring the safety of ammonia usage?

AIn the early days of LNG dual-fuel engines, there were many concerns about handling LNG at 300 bar. However, LNG has since been recognized as a safe alternative fuel and is widely used.

Methanol, although harmful to humans, is being safely operated as an alternative fuel, and the systems of methanol and ammonia engines are not significantly different. While it’s true that ammonia has different risks compared to other fuels, safety technologies for ammonia fuel propulsion and transport are currently being developed.

Based on our experience with LNG, LPG, and methanol, we expect to overcome the safety challenges of ammonia as well.

To address global warming, eco-friendly fuels that can replace HFO and LNG must be applied to ships. Addressing the associated costs and safety risks is a shared challenge, but we believe it also presents a golden opportunity for the Korean shipbuilding industry to differentiate itself from competitors, such as China.