Scour Prevention Systems Wants to Tackle Sediment Plumes from Wind Turbines

Lowestoft-based Scour Prevention Systems Ltd (SPSL) says it could have the solution to sediment plumes from wind turbines discovered in recent satellite images by NASA.

Brown masses of suspended sediment were highlighted on the newly-released images from space of North Sea wind farms by NASA’s Operational Land Imager (OLI).

SPSL’s mats, made from end-of-life car tyres fixed together, are designed to catch and retain suspended sediment, and are said to reduce the problem and stabilise the seabed.

The placement of tyres flat on the seabed is key to their ability to entrap sediment within their centres, the company said. The trapped sediment gives the mats a self-stabilising function and prevents the lowering of the seabed by scouring.

High energy flows transport sediment across scour prone sites, especially within offshore wind farms.

As they pass across the mats’ surface, flows are disturbed and speed reduced. Sediment transport across the mats is disrupted and the sediment is trapped and retained within the mats’ gaps, SPSL said.

According to the company, the tyre-mattress solution remains the only solution on the market to this growing problem caused by tidal current moving around turbine foundations. Technologically simple, it is internationally protected by a range of patents, SPSL said.

NASA’s detailed views of images of some of the North Sea’s largest wind farms – Greater Gabbard, London Array, and Thanet – show light brown plumes of suspended sediments extending from each turbine foundation.

Wind turbines have shown up as white dots in images from space for the last decade – but this is the first time sediment plumes have featured.

John Balch, SPSL chairman, said the new images had prompted the company to invest in research on the effectiveness of its product to tackle the issue clearly shown by the satellite images.

“This is an important piece of research from NASA showing something that has never been seen before in this kind of detailed resolution, and we are acting on it immediately,” Balch said.

“This significant increase in suspended sediments in the water column left unchecked could have devastating impacts on marine life, reducing visibility that could impact the growth of aquaculture and affect migratory species. The technology of our tyre mats offer a practicable solution to North Sea sediment plumes and the only solution to capture suspended sediment, remediating sites where there is known scour and preventing the onset of future scouring. We know that there is a major pipeline of new offshore developments across the North Sea, and if we identify these plumes now with a handful of wind farms, solutions can be put in place to solve the problem or counteract the effects going forward in the fast-moving industry.”

It is not fully clear how increased suspended sediment could affect the relatively shallow underwater environment, which is known to be an important fish nursery, NASA said.

Two years ago, researchers analysed satellite imagery and found that wakes and plumes could measure anywhere from 30 to 150 meters wide and up to several kilometres long.

Quinten Vanhellemont, a researcher at the Royal Belgian Institute of Natural Sciences and lead author of the 2014 research paper, said: “The fact that the wakes are browner than the surrounding waters shows that they contain more suspended sediments. This shows that the installation of the wind turbines not only modifies the wind field above the sea surface (which is expected as they are extracting wind energy), but that they also modify the currents and sediment transport in the water.”