MariNH3 aims for decarbonised marine sector

2 min read

Nottingham University is leading MariNH3, a programme exploring ammonia fuelled engine concepts with an aim of helping to decarbonise the marine sector.

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The MariNH3 team hopes that through developing disruptive engine technology solutions with minimised end energy use and reduced pollutants, the EPSRC-funded project will help to push the marine sector toward Net Zero as well as boosting the UK’s strong powertrain sector.

Professor Alasdair Cairns, principal investigator on the project and director of Nottingham University’s Powertrain Research Centre, explained that he believes the 'real challenge' for marine is retrofitting. 

Speaking to The Engineer, Cairns said that around 80 per cent of the sector’s greenhouse gases come from the large commercial ships used to move materials around the world, something that has historically been cheap and made sense from an economic stance — but presents a massive environmental problem, he stressed.

“These big ships have got engines that stay in service for up to 30 years. If you look at the timing of Net Zero … it’s still going to be these large engines that are in service,” he said. “And the problem is, when you look at competing energy vectors like batteries or fuel cells, they just don’t have the energy density.”

MariNH3 hopes to solve this problem by exploring retrofit solutions that can address issues around engine efficiency and pollutants. Whilst ammonia is described by Cairns as set to play a key role in marine’s decarbonisation efforts, he acknowledged that the issue of NOx emissions needs to be addressed.

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“We have to reduce the NOx emissions, and the technologies we’re looking at are what you would call ultra-low NOx combustion systems,” Cairns said. “There’s this classic trade-off … as thermal efficiency goes up, NOx goes up as well unfortunately.

“The big issue with ammonia is it’s a really slow-burning fuel, it burns roughly five times slower under like-for-like conditions than conventional fossil fuels.”

Industry partners helping the team to address this challenge include  MAHLE Powertrain. MAHLE’s novel ‘Jet Ignition’ technology is a fast burning combustion system currently used in Formula 1 engines, which the team aims to scale and transfer to marine where the fast burning could allow the engine to operate under conditions where NOx can be avoided or reduced.

Another UK company involved is Dolphin-N2, bringing its Split Cycle engine technology to the programme which the team hopes could serve as a long-term replacement solution to achieve diesel-like efficiency whilst being ultra-low NOx.

Whilst the sector has been slowly moving toward dual fuel technologies whereby a secondary clean fuel supply is fixed to the existing diesel engine, Cairns said, some natural gas is still being used, limiting decarbonisation efforts.

An idea proposed by MariNH3 is that instead of using a small amount of diesel as a liquid spark plug to cause combustion of ammonia, a biodiesel or more sustainable renewable fuel could be used for full decarbonisation of dual fuelling, he added.

“Our goal is to develop the best technical solutions in parallel to appropriate acceptance criteria and policy so that we ultimately develop technologies and policies which are ‘right first time’ and appropriately scaled across marine,” Cairns said. 

“This framework is based around a ‘technology agnostic’ life cycle analysis led approach to help us ensure we place ammonia end use appropriately.”