Norway-based Edda Wind has adopted an ingenious solution to storing hydrogen on the service operation vessels (SOVs) it is building. The hydrogen will be used to power fuel cells, enabling the ships to operate in zero-emissions mode
As Edda Wind chartering manager Håkon Vevang told Riviera Maritime Media’s Offshore Wind Journal virtual conference on 25 March 2021, the company is planning to use liquid organic hydrogen carriers (LOHCs) – liquid oils that can chemically store hydrogen at high storage densities – to store the hydrogen it plans to use in fuel cells it will retrofit to its vessels.
Edda Wind currently has six SOVs under construction. All will have much-reduced emissions compared to a conventional vessel when they enter service – thanks to the adoption of battery-hybrid technology – but in due course the company expects to operate them in ‘zero-emissions’ mode, using fuel cells powered by hydrogen.
Describing the SOV of the future, Mr Vevang said Edda Wind feels strongly that there is ‘no option’ other than to aim for zero-emissions ships, and LOHC technology will help it do so.
“We are working in a green industry and we need to be green as well,” he told delegates. “But the safety of our people and our clients is the single most important thing. We can’t increase risk to get to zero emissions. We need to do it in a way that is at least as safe as existing technology.
“We also need to provide our clients with exactly the same level of endurance. We can’t take hours a day to charge the batteries on a vessel or run back and forth to port for bunkering. We need to be able to achieve zero emissions and deliver the same amount of time on operation that we do now.
“And when it comes to logistics, we can’t add any additional hassle to our operations, we need to be able to bunker and be ready again just as easily as we do today. All of this explains why we opted for LOHC.”
In an LOHC, hydrogen is chemically bound to an oil via a process known as hydrogenation. It is then released by dehydrogenation. Compared to storing hydrogen in pressurised form in tanks, Mr Vevang and his colleagues at Edda Wind believe LOHCs have a number of advantages.
“The process can provide hydrogen ‘on demand’ as and when it is needed,” Mr Vevang told the conference, “but it is much safer than pressurised hydrogen because at any time we have less than 0.5 kg of free, molecular hydrogen in the system on board the vessel. That is very different to having tonnes of liquid hydrogen on a vessel and means that risk is very much reduced compared to conventional hydrogen.
“Another great advantage is that hydrogen stored in this way is not regarded as transportation of dangerous goods on the vessel, so the regulation is less complex. The process is non-toxic, the oil is hardly flammable and the hydrogen can be stored at ambient conditions, without any additional equipment.”
Mr Vevang explained that the thermal oil in which the hydrogen is held can be stored in a ship’s tanks and the logistics associated with using LOHCs is not especially complicated.
“We don’t need any additional tanks on our vessels for LOHC. We can store the oil containing the hydrogen in the same tanks we use for fuel today,” he said.
“We only need heat and a catalyst to release the hydrogen when required, and we can bunker in a couple of hours, and we can do it sat sea,” he explained. “Essentially what we have is two sets of oil, one ashore that is fully charged with hydrogen, ready for us to bunker with, and the oil on the vessels that has been used, that we pump back into the system so that it can be recharged so that it’s ready for use next time. It’s very easy and very convenient.
“All of our newbuilds are prepared for this technology,” Mr Vevang confirmed. “All of them are already battery-hybrid vessels. That’s the bare minimum for any SOV nowadays.
“When they enter service they will already have 30% lower greenhouse gas emissions, but in a few years’ time they will be able to operate as zero-emissions vessels.
“And the risk compared to conventional hydrogen or other fuels like ammonia is virtually non-existent, and it will be ready for use as soon as 2025. It really is a game-changer. We hope the rest of the market will follow our lead and go to zero emissions. It’s the future of this industry.”
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