Hydrogen has been used for decades in a variety of different industrial processes. Oil refining relies on hydrogen to remove sulphur from fuels, it is used as a reducing and oxidising reagent in metallurgical processes, and it is a vital part of the production of two of the other future fuels we have discussed in this series – ammonia and methanol. And without hydrogen as a fuel, we would not have been able to send crews and cargo into space.
But there’s a problem. Almost all the hydrogen used today is so-called grey hydrogen and is produced using fossil fuels, typically natural gas, in a process known as steam reforming. Moving along the colour spectrum we have black or brown hydrogen, produced using coal. Blue hydrogen is hydrogen that has been produced in a process where the carbon generated during steam reforming is captured and stored, while green hydrogen production uses clean renewable energy to split water into hydrogen and oxygen in a process known as electrolysis.
Q: What is the current status of hydrogen as a marine fuel?
“Global hydrogen production was around 70 million tons in 2018. Currently, almost all hydrogen is produced at or very close to where it is needed, and directed to industrial processes, so it is not transported by ships in the same way as LNG, for example,” says Jussi Mäkitalo, Business Development Manager, Wärtsilä. “However, February this year saw the world’s first liquefied hydrogen cargo transported between Australia and Japan aboard the Suiso Frontier, which is a significant step forward. Unlike an LNG carrier, however, this vessel doesn’t use its cargo as fuel.”
Mathias Jansson, Director, Fuel Gas Supply Systems, Wärtsilä Marine Power continues: “From a regulatory perspective the biggest challenge is that there simply are no rules concerning the use of hydrogen as a fuel for shipping. The IGF Code provides high-level requirements for using low-flashpoint fuels like hydrogen in maritime applications but to date it has mostly been applied for projects involving LNG. There is work ongoing at the IMO to add hydrogen to the code but it is still at the very early stages, with draft proposals expected later this or next year at the earliest.”
“Progress is being made on the regulatory side, but slowly,” explains Kaj Portin, General Manager, Sustainable Fuels & Decarbonisation, Wärtsilä. “DNV has published a Handbook for Hydrogen-Fuelled Vessels, which covers the key aspects such as safety and risk mitigation, as well as engineering specifications for systems. As it stands today new hydrogen applications have to follow the Alternative Design approval process, which is a risk-based process for designs that cannot be approved with current regulations. There are several pilot projects in the pipeline that will provide benchmarks, but it’s still very early days. One worth mentioning is the partnership between Wärtsilä and the class society RINA to deliver a viable hydrogen fuel solution.”
Q: What are the main pros and cons of using hydrogen as a marine fuel, and how do the storage and supply technologies differ from traditional marine fuels?
Jussi Mäkitalo: “Compared to diesel operation the assumption is that CO2 tailpipe emissions are far lower or even non-existent when using hydrogen as a fuel; if we’re talking about green hydrogen the well-to-wake emissions are expected to be dramatically lower as well. On the downside, using hydrogen directly as a fuel as opposed to using it as a raw material to manufacture other renewable fuels requires a lot of space onboard.”
Kaj Portin: “Even as a liquid, hydrogen storage takes up significant space compared to marine gas oil. To get the same equivalent energy content requires a tank volume that is almost eight times more than that of marine gas oil. Land-based storage for liquid and compressed hydrogen already exists so there is technology that can eventually be adapted for use in maritime applications. Hydrogen is also very light compared to diesel, so if you are limited by weight rather than space onboard then it could make sense.
Mathias Jansson: “Hydrogen could be stored onboard either as liquid hydrogen, which gives you the biggest storage capacity in the smallest possible space, or possibly as compressed hydrogen in 200 or 700 bar pressurised tanks. Liquid storage, however, brings its own set of challenges due to the extremely low temperatures.
To keep hydrogen in liquid form it needs to be stored below -253 C, which is highly energy intensive and places huge demands on the storage and supply system in terms of insulation requirements. The extreme cold can lead to oxygen from the air condensing on the pipework, resulting in a risk of explosion. There will be boil-off to deal with as well, which means you will need an energy-intensive reliquefaction solution. Leakages are another important consideration because of the highly explosive nature of hydrogen. In principle it is possible to use a similar setup as with LNG but with a greater focus on insulation and preventing leakages.”
Q: What is the status of marine engine technology capable of burning hydrogen? What exists now, and what are the likely future developments?
Kaj Portin: “Prior to 2015 the specifications for our gas-fuelled engines allowed for fuel with a maximum hydrogen content of 3% and following this we have tested and developed our dual-fuel engine technology further, demonstrating that it can utilise fuel blends with a hydrogen volume of up to 25%.
“Moving on from this we learned a great deal more about the special requirements that hydrogen brings in terms of engine and material design and are confident that this volume could safely be increased. However, we have to take into consideration the fact that things get a lot more complex when the hydrogen content of a gas is above 25%. This changes the classification from IIA to IIC according to the IEC 60079 standard, which covers areas where flammable gas or vapour hazards may arise.
“This has significant implications from a design perspective because it means the allowed voltages in components are lower and components such as pumps in the fuel supply system need to be hydrogen specific.”
Fredrik Östman, Product Manager, Lifecycle Upgrades, Wärtsilä Energy: “For energy production in land-based applications we are actively supporting our customers with proof-of-concept demonstrations for hydrogen blending. Our aim is to launch the first retrofit packages during 2023, and on the newbuild side we aim to have a pure hydrogen engine concept ready by 2025.”