Taking the lead on hydrogen safety
Lloyd’s Register is focusing on the safety of using hydrogen as a fuel
“One of the challenges for projects using hydrogen as a fuel is that we still have some significant gaps in our understanding about how hydrogen behaves,” Olav Hansen, Senior Principal Consultant in Lloyd’s Register Risk Management Consulting team based in Norway told the Motorship in a telephone interview in May.
Hansen is a leading authority on the use of hydrogen and is involved in a number of hydrogen development projects, both in Norway, which is currently at the leading edge of attempts to commercialise hydrogen as a fuel for the maritime sector, as well as across Europe.
“When the marine industry began to use gaseous fuels in the form of liquefied and compressed natural gas, it already had decades of experience of transporting the gas as a cargo, as well as utilising the boil-off gas as fuel and so on,” Hansen said. “We are starting from a much lower level of understanding with hydrogen.”
Compressed and liquefied
The two main methods of storing and using hydrogen, excluding conversion into different energy vectors, are compression and liquefaction of hydrogen.
NORLED’s short-sea demonstration project connecting Hjelmeland and Nesvik in southwest Norway will be fuelled by liquefied hydrogen, but a second car ferry in the same area supported by the EU-funded FLAGSHIPS project will be fuelled by compressed hydrogen.
The first vessel will consume around 150kg/hydrogen per day with bunkering every two or three weeks, while the second ferry will require up to 500kg/hydrogen per day and may require almost daily bunkering.
Projects looking into the use of hydrogen as a fuel are tending to favour compression because of better availability of fuel and less challenging technology. There are however issues with bunkering velocity and energy storage density which make liquefied hydrogen attractive, in particular for larger vessels and weight and space sensitive fast ferries. Swap tanks are considered for both liquefied and compressed solutions.
Larger storage tanks, potentially exploring the use of membrane tank technology, might help increase the range of vessels, as the low volumetric energy density of hydrogen imposes operational limits.
Norway is planning to decarbonise its 200 strong car ferry network, with up to 80 battery powered vessels likely to serve short-sea routes within the next couple of years. A smaller number of longer routes are currently unsuitable for battery solutions, and hydrogen vessels are under consideration for some of these.
A similar attempt to decarbonise high speed passenger ferries in Norway is also ongoing. Due to energy demand and travel distance pure battery solutions is not an option for most of these routes. The authorities are currently encouraging the development of hydrogen fuel cell vessel concepts to meet this gap in the market.
“The likely tenders for hydrogen-fuelled high speed ferries in Norway, which I expect to see coming later in 2019, represents an interesting niche for hydrogen vessels,” Hansen noted.
Lloyd’s Register is in the process of developing guidance flagging up hazards and helping to inform the industry about the challenges of working with hydrogen. The classification society is also stepping up internal training to increase the understanding of its workforce regarding the particular characteristics of hydrogen, in both its compressed and liquefied forms.
Lloyd’s Register is involved in a range of hydrogen-related projects, including the PresLHy R&D project, the HyDime and HySEAs projects in Orkney, as well as safety studies for a range of hydrogen onshore projects.
“At this point in time it is perhaps somewhat premature to produce prescriptive rules and regulations when the marine industry as a whole doesn’t yet have the necessary understanding, particularly with regards to the safety of liquefied hydrogen. Since so many different vessel types may consider hydrogen propulsion it is also very challenging to make one set of rules that fits all. Additionally, introducing prescriptive rules too early may restrict the innovation necessary to develop cost efficient hydrogen solutions with the result that the future of hydrogen in shipping may fail as the solutions developed are not sustainable. The current goal-based alternative design regime is therefore more optimal in these early days but this will change as the knowledge and experience increases,” Hansen said.
One of the research projects, PresLHy, involves experimental releases of liquefied hydrogen from a 1 inch bore pipe at HSL in Buxton, studying dispersion and explosion effects. While main focus may be releases ashore rather than maritime challenges, and release rates significantly lower than typical bunkering rates of 0.7-1.0kg/sec, test results will still be valuable to understand the behaviour of liquid hydrogen releases in general.
Research into releases will not just cover the risk of explosion/detonation and the range of the flammable plume, but also issues such as the negative buoyancy of a liquefied hydrogen spray, and its second-order effects on the surrounding air (precipitating frozen oxygen and nitrogen potentially to settle in snow-like accumulations).
Meanwhile, such negative buoyancy impacts on the potential location of containment tanks. Tanks mounted on deck, as in the latest Norwegian project, reduces the risk of accumulation in an engine room or another low point inside the vessel.
Leaks of hydrogen gas is a recurrent challenge owing to the size of hydrogen molecules. The effects of hydrogen embrittlement are very well understood in other industries, however shipyards may be less familiar with the phenomenon. The temperature resistance ranges of the specialty steels for containment tanks will need to be wider than those required for LNG vessels, but Hansen saw little need to dimension the tank surroundings for cryogenic exposure.
Such detailed research is likely to be closely followed by the IMO which is expected to begin the process of updating the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code) to include rules covering hydrogen in due course.
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