Left: MARIN’s testing process involves scale model ships in a giant basin, in order to recreate sea conditions.
Opposite page: MARIN’s solutions include the use of so-called ‘surface buoys’ that are attached to a line at 50m intervals to halt a ship as it attempts to drift across.
that’s before you consider the dangers to crew or passengers aboard a stricken ship. No wonder, then, that industry insiders are working so hard to make the seas secure for both shippers and energy providers. Buoyed by careful planning and new technology, researchers are developing a number of ways to keep drifting ships safe from turbines in the sea. Yet, if these platforms are inarguably ingenious, to be genuinely successful in the field they also require close collaboration with other stakeholders. Battle through these obstacles, however, and the North Sea could soon be transformed forever – if commercial companies are forward-thinking enough, anyway.
Hitting on something 80 MARIN 36
The approximate number of ships that get loose in the North Sea each year.
2,500
The number of new wind turbines that are due to be installed in the North Sea by 2030.
The North Sea is one of the busiest shipping regions on earth. An estimated 250,000 vessels sail through the Dutch portion of the sea each year alone, with major ports like Bremen and Antwerp also located nearby. This is a situation which could soon lead to problems – especially as offshore wind becomes more popular across the region. “Obviously the risk of a collision increases with the amount of turbines installed,” says Yvonne Koldenhof, senior project manager and team leader at Maritime Research Institute Netherlands (MARIN), “which is why collisions have not been common till very recently and why, if we do not think about mitigations, it will be common in the near future.”
As the senior project manager at MARIN implies, incidents like with the Julietta D have been mercifully rare so far. But if anything, that makes the looming threat even more worrying. We don’t know, Koldenhof emphasises, what would happen if a turbine collapsed right onto a ship post-collision – though given their blades alone can weigh as much as 55t, the answer can’t be anything good. And with the whole structure coming in at around 300–400t, Koldenhof fears that any crash would surely put the crew at risk. And if that wasn’t bad enough, the North Sea’s role as a major thoroughfare for cruise ships and ferries means that human life could be threatened in other
ways too. Once again, this is currently a theoretical risk. But given ferry disasters can quickly cause dreadful casualties – the 1993 sinking of the Herald of Free Enterprise off Belgium killed 193 – Koldenhof is right to be concerned. Then there’s the potential impact to turbine operators themselves. Given a 50MW offshore farm can cost up to $2bn merely to build, you have to imagine that repairing any ship-induced damage would be eye-watering.
Of course, it’d be wrong to suggest that the shipping industry is oblivious to these dangers. If nothing else, anchors are the obvious solution here, designed as they are to slow or stop a vessel that’s run amok. But as Koldenhof says, anchors are not always enough to stop a drifting ship. That could either be because their chains break or because they can’t hold ground, or even because active intervention by the crew in poor weather may actually make the situation worse. Given the infamous reputation of the North Sea as a place of bad weather – where snow and winter winds are common – that’s hardly a trivial concern. It’s surely not incidental that the Julietta D herself first got into trouble during inclement winter weather.
Buoy oh buoy If January’s chaos offered a warning to users of the North Sea, MARIN took the incident as an opportunity. That, at any rate, is clear from the range of options the Wageningen-based team has developed to stop ships from wreaking havoc on new wind farms. These solutions begin, says William Otto, with so-called ‘surface buoys’. “A line is equipped with small floating buoys every 50m, which prevents the ship from drifting over the line,” explains Otto, a senior project manager at MARIN. From there, he continues, larger buoys are installed every 500m or so. These are used to connect what Otto calls “mooring legs” – chains anchored to the seabed.
All this sounds fiendishly complicated. But the physics, Otto summarises, is simple enough. If a heavy-enough object, say a drifting ship, succeeds in stretching the line and dragging an anchor,
World Wind Technology /
www.worldwind-technology.com
MARIN
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