A road vehicle hydrogen fuelling station, very close to DNV’s headquarters building in Høvik, just outside Oslo, had an explosion in 2019.
The explosion happened because of a very small gas leak, so small only 3kg of hydrogen leaked in 2.5 hours, before it ignited. Nobody was injured. But it gives an example of the dangers of hydrogen, said Mónica Alvarez Cardozo, Senior Engineer, Piping Systems & Alternative Fuels, DNV.
There are two main learnings from the incident, the need for early leak detection, and the need to ensure hydrogen is well contained, she said. But this can be easier to do on land than on a ship.
Hydrogen is much more reactive than other potential alternative fuels, especially at high concentrations, and has a higher burning velocity. “We can say hydrogen has a higher explosion risk potential,” she said.
DNV tested the power of an explosion with a gas mixture 20 per cent hydrogen and 80 per cent air, and 10 percent methane with 90 per cent air. It showed that the hydrogen explosion would be much worse.
Explosions are also hard to model and predict, she said.
Hydrogen has been used safely in many land applications for decades. But it is often used with large safety distances / safety zones, or using blast walls, keeping people well away from risk, which is not possible to do onboard.
And onboard systems have multiple pipes and valves, offering more potential leak locations.
The maritime industry already has experience with competing fuels like LNG and ammonia from carrying them as cargo, but hydrogen has never been carried as a cargo.
Another challenge with hydrogen is that it needs to be either compressed or liquified to carry onboard, and even liquefied hydrogen will be a third of the density of LNG, so needing a tank three times as big for the same energy content.
However there have been a number of research projects looking at hydrogen as fuel.
The MarHySafe joint development project (JDP), with 26 companies, led by DNV, aims to create a knowledge base for safe hydrogen operations in shipping.
The ZeroCoaster project study, coordinated by Vard, a Norwegian shipbuilding company, aims to show that zero carbon shipping “is theoretically possible.”
There is increased interest in use of fuel cells onboard which run on hydrogen.
Where hydrogen is used in shipping, it will likely be on vessels running on coastal areas where hydrogen is available, such as in Norway, UK, and certain areas of Europe, Asia Pacific and the US, she said.