A panel of ship design experts discuss the many questions still to be answered concerning the use of ammonia as fuel, including scale, cost, availability, technology and safety
A panel of ship design experts looked at how best to future-proof a vessel by making it ‘ammonia-ready’, concluding that the challenges were many but not “insurmountable,” if there was strong industry collaboration.
Ammonia as a fuel and ‘ammonia-ready’ design were key topics at Riviera Maritime Media’s VLEC design: improving efficiencies at the terminal and at sea webinar, part of LPG Shipping & Terminals Webinar Week, held on 4 August. The webinar was produced by LNG Shipping & Terminals with the WLPGA joining as a supporting organisation.
With decades of ship design, operation and regulation under their belt, the panel included: ABS Europe global gas development director Sean Bond; Safinah Group senior consultant, whole ship design and naval architecture, professional, technical and engineering services Keith Hutchinson; and PG Shipmanagement Pte QHSE manager Shiraz Lakhani.
Ammonia’s carbon-free characteristics have captured the imagination of shipowners as a future fuel to reach decarbonisation targets in the decades ahead. This has led shipowners of gas carriers and other vessel types to invest in ‘ammonia-ready’ newbuilds, laying the groundwork to burn ammonia when the technology and supply becomes available.
“One of the most important elements is your concept design and how you deal with the challenges of ammonia”
To burn cargo as fuel such as ethane, ammonia or other gaseous fuel, Mr Bond said there is a roadmap, noting: “The IGC Code will permit you to use cargo as fuel that is not methane.” While ethane engines have been approved and the fleet is operating on ethane at the moment, Mr Bond said there is “still an equivalency path that must be followed for approval.” This involves discussions around concept design, various risk assessments that must be reviewed and approval prior to certification.
Ammonia as a fuel
One trend noticed by ABS is a move towards future-proofing of vessels, specifically using ammonia. “This is to cover the intent of the CO2 emissions requirements, as ammonia doesn’t really have any CO2 emissions, with the exception being the pilot fuel needed to burn it,” said Mr Bond.
Ammonia as a fuel does have certain challenges, he noted, including a lower energy density and toxicity. “All these things have to be addressed in the design phase,” said Mr Bond.
Getting approval for a ‘Ready’ notation, there are three levels that are offered by ABS. Level 1 is an approval in principle (AiP) for the concept design and a statement in the ABS Record; Level 2 is a suitably worded Statement of Compliance and a statement in the ABS Record; and Level 3 is a class notation with a description note in the ABS Record.
“One of the most important elements is the concept design and how you deal with the challenges of ammonia and how easy it will be in the future to make the kind of changes necessary to burn ammonia as a fuel,” said Mr Bond.
Overwhelmingly, delegates attending the webinar thought that ethane carrier designs would be built ‘Ammonia Ready’ to be able to be converted to burn ammonia fuel when it becomes available. In a poll, ‘How likely do you feel it is that design of ethane carriers will accommodate early design changes to be considered ammonia fuel ready?’ 4% voted ‘certain’, 18% ‘almost certain’, 32%% ‘likely’ and 39% ‘possible’. Only 7% of voters choose ‘unlikely’.
Questions around ammonia
One of the questions around ammonia as fuel posed by Mr Lakhani was availability. “I’m not sure how the scale of this is going to work out in the future. 80% of the ammonia produced is used in the fertiliser industry. If 30% of the world’s shipping uses ammonia as a fuel, production will need to be doubled. Do we have that upscale capacity?” he asked. Mr Lakhani was referring to a technical paper published jointly by Alfa Laval, Hafnia, Haldor Topsøe, Vesta and Siemens Gamesa.
He noted a number of questions that shipping would have to answer: If I have the ability to change over my cargo to carry ammonia would my engines be capable?; What would be the cost impact of changing fuels?; Is the technology mature enough? Mr Lakhani noted the need for bunkering infrastructure and ammonia’s toxicity. He concluded:” There is a lot of research to be done.”
Mr Lakhani also voiced safety concerns about the ability to detect an ammonia leak when using the cargo as a fuel. “Ammonia is not an easy fuel to carry. As long as it remains in the containment system it is fine. If there is a leak, then we need to have proper systems, proper crew capable of handling those,” he said. He made the point that response time to a leak was limited because of the toxicity of the cargo. “We need to be very careful,” he added.
“If 30% of the world’s shipping uses ammonia as a fuel, production will need to be doubled”
Building on Mr Lakhani’s comments, Mr Hutchinson said specialised materials, equipment and venting to handle ammonia as fuel could be specified, but it was the layout – the conceptual ship design and layout of the machinery space – that will be the big drivers. “I don’t think it is insurmountable by any stretch of the imagination but there isn’t a lot of experience in shipyards or with consultants designing machinery spaces intending to burn ammonia fuel,” he said.
Ammonia as fuel was just one topic tackled by the panel. In his presentation, Mr Bond discussed the evolution of the ethane trade, coinciding with the US shale boom. “Prior to the current ethane fleet, mainly ethylene carriers were the only vessels suitable to carry ethane,” he said. “These were typically Type C tank, semi-pressurised tanks and smaller vessels, ranging in size from 5,000 to 22,200 m3 prior to 2015.”
How big is too big?
In recent years, vessels have gradually grown larger. This started in 2013, with the ordering of 37,500 m3 ethane carriers fitted with bi-lobe Type C tanks ordered by Navigator Gas, followed by orders a year later for 87,000-m3 VLECs with membrane tanks ordered by Reliance Industries and 85,000-m3 VLECs ordered by JHW.
Capacities increased further, with the order for a 98,000-m3 VLEC with membrane cargo containment in 2018. We have seen designs of even larger vessels, but those have not yet been built,” said Mr Bond. He highlighted designs for a 147,000-m3 VLEC from Hudong-Zhonghua and a 150,000-m3 VLEC from Jiangnan.
Based on a poll, “Which direction do you believe ethane carrier sizes will go?” 52% of respondents said the ‘Trend will be towards larger vessels’, 32% choose ‘Maximum size will remain at the current 99K size’ and 16% said ‘Maximum size will decrease below 99K cubic metres’.
“It’s interesting to correlate methane with ethane because of the size and temperature of the cargo,” Mr Bond noted. In particular, he said that the differences in temperature and density have an impact on design. As far as density, he said, this impacts the design of the hull, cargo-containment system and cargo-transfer system. Temperature has an impact on the material, insultation and capacity and operability of the reliquefaction plant.
Additionally, VLECs have the option of using ethane as a fuel, making gas dispersion and gas detection around the ship an important design feature.
When it comes to designing ethane carriers, cargo-containment systems have consisted of membrane technology, Type B independent tanks with leak-before-failure design and partial secondary barriers, and Type C pressure tanks with no secondary barrier.
“Many of the earlier ships were Type C, limiting the capacity and how large the vessel can be. The bulk of the ships are using membrane technology, and, of course, Type B tanks are an option,” said Mr Bond.
Advances in cargo containment
“There have been metallurgical advancements for cargo-containment systems,” noted Mr Lakhani. Traditionally, 5% nickel steel was used, but recent advancements have seen the use of high-manganese austenitic steel used in Type B containment systems in ethylene and ethane carrier design.
He noted Type B containment will be used in a new ultra-large ethylene/ethane carrier design, with a capacity of 165,000 m3 in 2019. He said this vessel is almost 70% more than the current largest designs available.
Another is the BrilliancE 99,000 m3 design that will use a Type B prismatic containment system, tailored for the North America-China route.
Among the efficiency advancements in more recent newbuilds are an additional refrigerant compressor and an additional genset, with a total of four, two of which are capable of taking over the full cargo-discharging load. Two gensets are also capable of maintaining the cargo temperature and a third will be brought online to achieve the discharge temperature at the terminal.
During his presentation, Mr Hutchinson made the point that the ship design process has evolved, too. “We need to transpose this operability right into the ship design process. Operational efficiency has become paramount,” he said.
Traditionally, naval architects would be guided by naval architecture ‘exam questions’ when designing a ship: ‘What do you have to carry and how fast and how far?’ Typically, a shipowner would want minimum cost, explained Mr Hutchinson.
However, regulations from IMO, the EU and other regulatory bodies are now central drivers, as are societal pressures. “Ports don’t want to see dirty fuels burned in the harbour and [there is] public pressure to reduce global CO2 and greenhouse gas emissions,” he said.
There are key benefits to the shipowner, namely reduced fuel cost and less emissions might mean obtaining “some carbon tax advantages,” pointed out Mr Hutchinson. He noted other benefits would be lower first and through-life costs because of less maintenance and the reputational advantage of being a “clean operator”.
Still, it is a balancing act for a ship designer. Faced with conflicting operational performance aspects, the naval architect is like a “juggler”, he said, optimising the maximum efficiency and minimising the installed power. ”We need to evolve designs that are very different from those just 10 years ago,” said Mr Hutchinson.
To obtain good propulsion efficiency requires collaboration between the ship designer, propeller manufacturer and engine manufacturer.
The two main drivers that will produce an efficient ship design are principal dimensions and hull form, he noted. “They affect the efficiency and fuel costs,” he said.
He cautioned that the minimum opex designs do not always coincide with the minimum capex. While shipyards strive for minimum lightship to keep costs low, larger ships can be more economical to operate. “Steel is cheap and air is free,” he said.
He said the principal dimensions of a ship can be frozen far too early in the design. “Once they are frozen, you are not going to get them back,” said Mr Hutchinson.
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