The Maritime Research Institute of the Netherlands (MARIN) has tested three innovative barriers to prevent collisions between ships and wind turbines. The immediate cause for this research was the incident with the Julietta D on 31 January 2022.
This drifting ship first hit a tanker and then a transformer platform and wind turbine foundation of the wind farm Hollandse Kust Zuid currently under construction. Installed wind turbines can fall on a ship in the event of a collision, posing a great danger to the crew, passengers, the ship itself and the environment.
Until 2030, approximately 2500 wind turbines are set to be installed in the North Sea. MARIN research for the Dutch government has shown that as a result, a ship may collide with a wind turbine 1.5 to 2.5 times a year. To give an idea: vessels going adrift on the North Sea number around eighty each year.
Accidents can be avoided in various ways: drifting vessels can put down their anchors, for example. But this requires active intervention by the ship’s crew in often difficult circumstances. Alternatively, emergency towing vessels (ETVs) can be deployed to tow the drifting ship to safety, while shipping supervision can be upgraded to include some form of vessel traffic management.
Yvonne Koldenhof, team leader Traffic & Safety at MARIN: ‘The accident involving the Julietta D shows the real dangers posed by vessels adrift. Even with current resources, such as ETVs, it’s difficult to avoid these kinds of incidents.’
Crash barriers at sea
In a workshop on 23 February, a group of twenty experts from the sector and from MARIN developed three innovative concepts for maritime crash barriers between shipping routes and wind farms.
‘Our mission statement includes both marine safety and sustainable sea use,’ explains MARIN’s general director Bas Buchner. ‘That means more than simply drawing attention to the dangers; it means going in search of solutions to prevent accidents. We were keen to do this in tandem with experts from the offshore sector and that’s why we opted for an open innovation project. We gave it the working title “Crash barriers at sea” because many wind farms are planned near traffic separation schemes: the freeways of the sea.’
The first concept involves a string of surface buoys secured by drag anchors. The second concept comprises a smart suspension net between fixed poles and the third is an anchored underwater hook line designed to catch the anchor of the drifting vessel.
Scale model tests
MARIN built scale models of all three solutions and ran tests in its Offshore Basin on 17 and 18 March to see if the barriers were capable of deflecting a scale model comparable to the Julietta D in storm conditions. The first results are promising.
We’ve established that all three concepts are able to intercept the vessel,’ says William Otto, MARIN’s Offshore project manager. ‘The drag anchors of the buoy string dissipate the drift energy evenly, so that the vessel stays afloat across the waves. The anchored underwater hook heads the vessel into the waves, so reducing roll. That means the vessel remains in place while being exposed to relatively low forces. The smart suspension net initially showed too much droop, but with a bit of fine-tuning, we were able to get this functioning too. Over the coming months we will go on to assess the various pros and cons of these systems.’
The various concepts and all test results are being shared as an open innovation project to enable further development of the most promising concepts. The initiative has also sparked widespread international interest.
Representatives of the following Dutch maritime and offshore organisations were involved in this project: Bluewater Energy Services, Mooreast, Vuyk Engineering, Heerema Marine Contractors, Boskalis, GustoMSC, KRVE (Rotterdam Boatmen), Pinkster Marine Hydrodynamics, Huisman Equipment, Orca Offshore en SBM Offshore.
Video below: The three concepts: a string of surface buoys secured by drag anchors, a smart suspension net between fixed poles and an anchored underwater hook line designed to catch the anchor of the drifting vessel. All concepts were tested in the Offshore Bassin to see if the barriers were capable of deflecting a scale model comparable to the Julietta D in storm conditions.