A new generation of vessels

One vessel is almost as tall as the Eiffel Tower and has a deck as big as a football field. The other can hoist 27 Boeing 747s in one go. Our latest-generation vessels Voltaire and Les Alizés appeal to the imagination. Behind these innovative vessels is a strong team, from designers and naval engineers to commercial experts. But how do you build such state-of-the-art vessels? We spoke with Jan Van de Velde, Head Fleet Construction at Jan De Nul.

What do the Voltaire and Les Alizés mean for the future of the offshore wind sector?

Jan: "The offshore wind industry has been evolving rapidly in Europe for a number of years. Due to an enormous increase in scale, the current installation vessels are no longer able to install the latest components. Jan De Nul was therefore the first contractor in the world to order a new generation of these vessels: the jack-up installation vessel Voltaire and the floating installation vessel Les Alizés. A calculated risk – both on a technical and commercial level – that we assessed correctly. With the investments in the Voltaire and Les Alizés, we show our clients that we mean business. That we are not temporarily active in the offshore wind sector but invest in its future!"

Surely that requires close consultation with the sector?

Jan: "Absolutely. We regularly consult with various stakeholders in the offshore wind sector. They determine to a significant extent which developments will take place in the coming years.  Conversely, it is also important for them to know that our vessels are able to execute their projects. That is why the Voltaire has already been engaged for some major projects, such as Dogger Bank in the UK, the largest wind farm in the world. Also our floating installation vessel Les Alizés has already received its first orders: it will contribute to the installation of the Borkum Riffgrund 3 and Godewind 3 wind farms."

Does Jan De Nul surpass its own innovative limits here? 
Jan: "We have a lot of experience with dredging vessels, but we had never built a jack-up installation vessel ourselves. And what a vessel at that: the Voltaire has a crane capacity of over 3,000 tonnes and the jack-up system can lift as much as 16,000 tonnes out of the water. The challenge was to integrate these legs into the vessel, taking into account all operational aspects. Fortunately, we have learned a lot from the two jack-ups we’ve already been working with. Les Alizés has a crane capacity of over 5,000 tonnes. This vessel is constantly working in a dynamic environment and is able to work while floating. Lifting such a huge load under these conditions is unprecedented in the world."

How sustainable are these installation vessels?
Jan: "Both vessels have been designed to have minimal impact on the environment. An exhaust gas treatment system and diesel particulate filters drastically reduce our emissions. Currently, such Ultra-Low Emission vessels by far exceed current regulations at sea. Better still: we even meet the regulations for inland waterways. And it’s our ambition to move towards standards that apply in city centres. We are ready for the increasingly stringent sustainability requirements."

How long do you work on such a vessel? 
Jan: “The first drawings of the Voltaire already date from 2017. This was followed by an internal consultation and interaction process that easily took a year. In close cooperation with our commercial people, we carefully examined what we as a technical department could do ourselves and what the sector needs. We entrusted the further development to a smaller team bursting with knowledge and experience. This close-knit team ensured that nothing could escape our attention."

What technical choices did you face during the construction of the vessels?
Jan: "With a jack-up installation vessel such as the Voltaire, everything is very closely linked to each other: the strength of the crane, the weight of the vessel, the strength of the legs. It was our job to find the ideal balance to get the most out of all these factors. Some choices depended on the best available option on the market at the time, such as the jacking system. It contains, for example, a plate of a certain thickness. We chose the strongest and best quality available worldwide. The most important choices had to do with the increase in scale: crane size, deck size, operational depth and workability. This results into very strict design requirements for the vessel to deliver on all promises, not only on paper, but also in practice.

What was for you the biggest challenges while constructing both vessels?
Jan: "The biggest challenge on a human and technical level was without a doubt the pandemic. The team working on these vessels has never seen them in reality. That is very exceptional.  Normally, we would visit the shipyard in China every month, together with internal and external experts. Fortunately, we have our own people on the spot, who always stay there for a few months.  Also in the coming months, this will continue to be the biggest challenge."

This is an extract from the 2021 activity report.