Four-stroke Wärtsilä ammonia engine now delivers 90% GHG emissions reduction

Image: Wärtsilä

Wärtsilä reports that its ammonia-fueled four-stroke engine now delivers higher than ever levels of efficiency and performance. Following its introduction to the commercial marine sector in November 2023, the Wärtsilä 25 ammonia engine has undergone extensive testing to optimize its performance parameters. According to Wärtsilä, the latest results, assessed against the FuelEU Maritime reference and measured on both a Well-to-Wake and Tank-to-Wake basis, show that a 95% ammonia energy share now achieves up to a 90% reduction in greenhouse gas emissions compared to equivalent fuel oil engines. This is an 18% improvement in the ammonia engine’s emissions performance.

The Wärtsilä 25 ammonia engine, which is available as part of the Wärtsilä 25 engine platform, was developed based on Wärtsilä’s safety and operational experience gained from low pressure dual-fuel (DF) engines running on LNG.

The recent tests have shown ammonia to be a suitable fuel for the low-pressure Otto cycle concept which is the design that Wärtsilä has utilized for its ammonia engine solution. The decision to opt for a low-pressure Otto cycle concept was based on several factors, including safety, efficiency and overall potential for greenhouse gas reduction, among several other parameters. Comprehensive tests conducted on different engine sizes have shown that the efficiency of the low-pressure Otto cycle concept is consistent with, and equal to, that of dual-fuel LNG engines. Ammonia is also highly knock resistant, with robust combustion capabilities across a wide range of engine settings.

“With decarbonization front and center of our company strategy, we have continued to enhance the capabilities of our ammonia engine solution – adding even more safety features and further improving its performance,” said Stefan Nysjö, vice president of power supply, Wärtsilä Marine. “This is in line with our commitment to ‘continuous improvement,’ whereby we continue to develop, test and enhance new and current technologies and solutions which will support the industry with making meaningful reductions in greenhouse gas emissions. For our ammonia engine we opted for the low-pressure Otto cycle concept as we are confident this will deliver the best levels of safety, efficiency and reliability for our customers,”

The enhancements made to the Wärtsilä 25 ammonia engine’s performance benefit the entire ammonia solution, which comprises of an AmmoniaPac fuel gas supply system, the Wärtsilä Ammonia Release Mitigation System (WARMS), and the Wärtsilä NOx Reducer (NOR) for optimal exhaust after-treatment.

Wärtsilä says that safety, efficiency and reliability are central to the solution design, maximized by a highly sophisticated automation system and maintenance agreement to ensure safe and efficient onboard operations. Alongside future engine orders, the enhanced performance will also be integrated into engines already contracted as first deliveries are due to take place from 2026 onwards.

Ammonia has emerged as a promising alternative fuel as the shipping industry looks for more sustainable fuel options. With global regulations having set a clear destination for shipping – net zero emissions by mid-century – ammonia will play a significant role in enabling the shipping industry to reduce its emissions. A report from Wärtsilä highlights the role that sustainable fuels will play in achieving this target which is set by the International Maritime Organization (IMO). According to the report, existing decarbonization solutions, such as fuel efficiency measures, can cut shipping emissions by up to 27%, however, fuels such as ammonia will be a critical step in eliminating the remaining 73%

• Download the report HERE