days at a time, with all the environmental and organisational benefits that follow. Many like it have since been launched, in time to meet the burgeoning demand for offshore wind farms. “If a technician can have a 12-hour working day,” explains Tyson, “and six of those hours are spent just getting to and from the turbine, that is not a great use of a valuable asset: time. This is where SOVs really have their value.

“A technician can wake up, eat breakfast and be on their turbine for the day within an hour, avoiding long transits, seasickness, commuting, parking or loading their bags. The growing size and distance from shore of more recent offshore wind projects are driving the economics of vessels so that SOVs make greater sense.” MHI is not alone in seeing the advantages of these ships. Built at a Turkish shipyard, for example, Louis Dreyfus Armateurs’s Winds of Change SOV recently started work for Ørsted. Across the Atlantic, there are plans to build a similar vessel for use off the coast of Rhode Island. Another fruitful area of development has been in the creation of ‘service accommodation transfer vessels’, or SATVs. Smaller than full SOVs, these ships nevertheless retain enough room to house cabins for crews to live comfortably for about a week. More to the point, they’re also light enough not to displace landing crews when they sail close to turbines, and can nimbly navigate between rows of pylons without causing accidents. “These days,” says Lewis, “it simply makes more sense to have a vessel that can both accommodate technicians for extended periods and push up to the turbine towers for transfers.”

Whatever the specifics, all these ships do share one thing: a commitment to both environmental and crew safety. In the case of MHI, Tyson and his colleagues are looking at height-adjustable ship landings, allowing the transfer of crews between the SOVs and smaller vessels without climbing dangerous ladders. In terms of the environment, alternative fuels are gaining popularity too, while MHI’s SOVs are designed to transit at a leisurely ten knots, making it far easier for passing whales to avoid their bows. Marrying regular engines with a new propulsion system, BMT’s attempt promises greater fuel efficiency. That, of course, would save money and boost the environment. Yet you can’t help but feel that all this activity might still come at a price. Because there are so many types of alternative fuels – from propane to ethanol to butane – it’s hard in practice to design ships around them. And because many of these environmentally friendly alternatives are low density, they require larger storage containers than regular carbon fuels. To put it another way, then, it may be a while before this new generation of vessels become truly clean – ironic in an industry

World Wind Technology /

that prides itself on its green credentials and commitment to sustainability.

Environmentally dubious What’s next, then, for the future of offshore vessels? Though many developments are encouraging, Tyson strikes a note of caution, and not just about the environment. “The biggest challenge for the US is tailoring the design to [local] shipyard capabilities and materials to reduce the higher build cost and build time,” he says, “which requires cooperation from the whole supply chain including us, designers, yards and owners.”

Midway between an installation vessel and a transfer boat in size, the Esvagt Mercator SOV allows maintenance crews to live at sea for days at a time.

“If a technician can have a 12-hour working day, and six of those hours are spent just getting to and from the turbine, that is not a great use of a valuable asset: time.”

Graham Tyson

Fair enough: new wind farms already cost more in the US than they do in Europe, and a lack of experience in shipbuilding can raise prices further. Lewis, though, is more optimistic. He says the industry is moving too quickly to make hard and fast predictions and expects that moves towards “greener, hybrid propulsion systems” will continue. At the same time, he adds, electrification will probably increase in popularity too. “It would make sense to harness the electricity being generated out at the farm to power the fleet of operation and maintenance vessels,” says Lewis. “As battery technology improves, this will become viable.” Certainly, you can see that if you look at what shipbuilders themselves are saying. By some estimates, the newest models of offshore vessels are 30% more sustainable than their ageing predecessors. To put it another way, the SOVs of the future look set to be just as useful – and make the whole industry even more sustainable too. ●


Number of SUVs that can be carried by the biggest offshore vessels. Bloomberg


Esvagt Mercator

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