Solis Marine is developing designs to retrofit ships with engines capable of burning ammonia. Can you tell us more about this?
We have been involved in a couple of projects with vessels running on ammonia as a fuel. Most recently we provided design engineering services for the Fortescue Green Pioneer, which is a Platform Supply Vessel (PSV) converted to run on ammonia. This was the world’s first use of ammonia as a marine fuel following its sea trials in Singapore earlier this year.
Our role was to provide naval architecture and design engineering relating to the integration of Fortescue’s ammonia fuel technology onto the existing vessel. This started with the concept design for the ‘Fuel ready’ stage in terms of deck layout, ammonia tank connection space, fuel preparation room and bunker station arrangements. We continued through to detailed design aspects relating to the ammonia fuel tank foundation, vent mast, ventilation and fire systems and vessel structural modifications, amongst others.
What are the key challenges faced when retrofitting a ship for ammonia-fuelled engines?
There are two principal areas. Firstly, the challenge of retrofitting any new fuel system and secondly, the challenges specifically relating to ammonia.
Retrofits
The challenge is adapting vessels that were not designed to accommodate this technology, which means working within the constraints of the original design.
In a recent project, Solis Marine compared hydrogen fuel cell and battery hybrid technologies for a coastal research vessel application.
Hydrogen has to be stored as gas (not cyrogenic) and has a low volumetric energy density. So, even with reduced range the fuel storage was always problematic. This showed that whilst it might be possible, the fuel storage required would be extensive - tanks on deck, next to wheelhouse etc – and therefore not a desirable solution.
The next stage in study looked at a hybrid system; with a hydrogen / electric drive train installed in parallel with the existing diesel engines. The vessel would run on hydrogen most of the time but rely on diesel as a backup in case of any supply issues.
The benefit of a hybrid approach with a modular layout is that the electric drive train can be powered by any suitable fuel, even diesel, so the vessel has more flexibility and supports futureproofing. Electric motors are more efficient than ICE (internal combustion engines), even when running on diesel.
Combining electric motors with some element of energy storage allows for more efficient energy usage overall – such as cruise ships switching to diesel electric propulsion and stacking up the generators as power is required.
Newbuilds
By comparison, newbuilds are more efficient in terms of the design process as the new fuel system can be incorporated from the outset. The system can be optimised for the duty cycle and operating profiles, incorporating safety critical considerations for both ammonia and hydrogen. However, there are the additional emissions associated with newbuilds that vary greatly depending on the source of the raw materials and processing methods. It takes three to six years to achieve a net benefit in terms of emissions for a newbuild.
Ammonia challenges
Ammonia has also been around for a considerable time and a global supply chain is already in place for use in fertilisers. A fleet of 100 buses in Belgium was converted to run on ammonia due to fuel shortages during the Second World War. It is even used on the International Space Station (about 400 tonnes) so it has been proven that it can be handled safely in high-risk environments.
It is highly toxic gas, so safety is a key consideration that drives design requirements with regard to the layout for fuel storage and equipment. The first line of defence are secondary enclosures that are required for any piping / equipment / space that may contain ammonia at any time.
Automated detection and ventilation mean that any leak within the space is isolated without needing human intervention. Incorporating these systems into an existing vessel can be challenging and can require modifications in spaces otherwise unrelated to fuel or powering.
Codes and standards are under continuous development, even during the course of a project, with future significant changes likely. Different Flag states have different requirements and levels of engagement.
Ammonia is less expensive (compared with hydrogen powered fuel cells) if internal combustion engines (ICE) can be modified. The balance of equipment can add up (double wall piping, valves, control systems etc), but all are readily available.
What considerations are made in the design to deal with the risk and safety aspects for the crew?
Design is led by safety considerations from the concept stage, whether a newbuild or a retrofit. The arrangement of fuel storage and associated equipment is defined by the proximity of any opening that could lead to ammonia entering a manned space in the event of a release.
The requirements for dealing with an ammonia release scenario are extensive, impacting normal operations which might be due to purging the system when switching to / from ammonia fuel operation. A scrubber needs to be fitted to reduce the ammonia concentration to acceptable levels before the gas can be released to the environment.
Only in a true emergency situation, such as a fire, would you have ammonia release direct to the environment and this would need to be to within a safe zone, well away from manned spaces.
Piping or machinery that may contain ammonia must have a secondary enclosure which acts as the first line of defence in the event of a leak and there must be extensive sensors installed for detecting ammonia in these spaces.
Any leak must be automatically isolated and ventilated by the system. There must be no reliance on human intervention which could be a weak link in the process.
Manned machinery spaces have similar detection and ventilation systems and are designed to safely contain any leakage with primary and catastrophe ventilation systems in place as well as primary and secondary fans so that no single failure can cause a system failure.
Safe escape routes must be provided and safe spaces in case of ammonia release on deck. Crew training and protective equipment is also a key consideration although not directly related to design.
There are concerns that the burning of ammonia will lead to emissions of NOx and N2O. Is this correct?
Depending on the temperature at which ammonia is burnt, the combustion process can produce nitrous oxides, but if this is the case then it can be mitigated by treating the exhaust.
NOx and N2O, whilst not containing carbon, are greenhouse gases that are produced in the combustion of ammonia. Exhaust gases can be treated by a selective catalytic reduction systems (SCR), also known as scrubbers, which convert nitric oxide into nitrogen and water.
SCRs are already in use on conventional vessels to reduce NOx emissions, so this solution is proven and readily available.
The debate around alternative fuels appears to be quite polarised. What is the way forward?
There is no silver bullet. Different applications will be suited to different solutions. As a global consultancy, Solis Marine is technology agnostic. We always start with open mind and allow a full assessment of all the options.
Fully electric solutions are well developed and in operation for ferries on short haul journeys.
Batteries are heavy and range is limited to about a day before hybrid / hydrogen solutions come into play, and even then, might only be extended up to a week or so. But this is useful for short haul shipping, fishing vessels and the leisure sector.
A lot of work in future fuels is taking place on smaller vessels, but deep sea shipping is responsible for 80% of GHG emissions. Ammonia is currently the only zero-carbon solution with sufficient energy density to be feasible for this sector – methanol still contains carbon.
Sphera’s well-to-wake study for the Society for Gas as a Marine Fuel confirms that GHG emissions can be reduced by up to 61% using ammonia, meaning there is no longer a question of whether ammonia will contribute to the solution for achieving the IMO reduction targets.
The first dual-fuel ammonia engines are reported to be delivered later this year (2024) although it is expected that a period of sea trials, for up to a couple of years, will take place before these come into commercial operation.
Any other thoughts?
It is important to consider the bigger picture and the way we live could change significantly between now and 2050. We should think about:
Join Ros for the NorthStandard podcast which is now available. You can listen to it here.
For further information about future fuels and decarbonisation, please email r.blazejczyk@solis-marine.com.