The Maritime Research Institute Netherlands (MARIN) has begun testing three new barriers that will help prevent collisions between ships and wind turbines.
The research was prompted by the incident involving the bulk carrier Julietta D on January 31 of this year. On the said date, the drifting bulk carrier initially collided with a tanker before hitting a transformer platform and a turbine foundation for the Hollandse Kust Zuid wind farm currently under construction.
MARIN said a collision with an installed wind turbine carries a real risk of the turbine toppling onto the vessel, seriously endangering crew, passengers, the ship itself, and the environment.
Some 2,500 wind turbines are set to be installed on the North Sea in the period to 2030, taking the risk of a turbine being hit by a ship to around 1.5 to 2.5 times a year as shown by research done by MARIN for the Dutch government.
MARIN said 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.
"The accident involving Julietta D shows the real dangers posed by vessels adrift," says MARIN's Traffic and Safety team leader Yvonne Koldenhof. "Even with current resources such as ETVs, it's difficult to avoid these kinds of incidents."
A group of 20 experts from MARIN and the wider maritime sector developed concepts for maritime crash barriers between shipping routes and wind farms during a workshop held in February.
"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.
MARIN built scale models of all three solutions and ran tests in its Offshore Basin on March 17 and 18 to see if the barriers were capable of deflecting a scale model comparable to Julietta D in storm conditions.
MARIN said 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, 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.
Involved in this project were representatives of Dutch companies Bluewater Energy Services, Mooreast, Vuyk Engineering, Heerema Marine Contractors, Boskalis, GustoMSC, KRVE (Rotterdam Boatmen), Pinkster Marine Hydrodynamics, Huisman Equipment, Orca Offshore, and SBM Offshore.
