Shiny ship hull surfaces, free from contaminants
Biofouling, the accumulation of microorganisms, plants, algae or small animals, is known to increase the roughness of the colonised surfaces. When those surfaces form the underwater parts of a ship’s hull, the increased roughness significantly alters the ship hydrodynamics. Severe marine biofouling conditions cause negative economic and environmental impacts through increased fuel consumption and carbon emissions. They also promote the transport of invasive species, threatening marine biodiversity.
Biofouling: a sticky problem
“Marine biofouling can be a real curse. Even light fouling increases hull resistance; compensating for this increase and fuel consumption leads to over a million euros in lost revenue per vessel annually,” notes Yves Chardard, CEO at Subsea Tech. The best way to mitigate biofouling is to detect it at a very early stage while it can still be cleaned easily and with soft methods that do not damage the hull paint or coating. Chardard highlights that current technologies are limited in their ability to efficiently manage ship hull biofouling. Maintenance costs are relatively high, especially when inspections are taking place within port waters that are heavily turbid and inhibit visibility. Inspections far from port waters induce costly charter time and are thus avoided.
Seeing the invisible
The EU-funded SleekShip project successfully developed technology to measure and track hull fouling levels to optimise cleaning schedule and increase coating performance. Chardard, who has been coordinating SleekShip, states: “Our semi-autonomous underwater vehicle can detect slime at an early stage using a multispectral camera and clean it softly with a cavitation cleaning system. The operation can be conducted while the ship is docked at port.” The new product significantly enhances the quality of underwater imaging, enabling biofouling measurements previously impossible with conventional methods. Underwater conditions cause light absorption and loss of contrast and colour, challenges that ordinary cameras can hardly overcome. By contrast, SleekShip’s camera detects light beyond the visible in wavelength bands where light backscattering is weak, and slime is, therefore, easier to distinguish. Hyperspectral imaging has already proved itself in remote monitoring. “We showed that the technology can also work well underwater, clearly detecting biofouling at early stages even in water turbidity levels exceeding 250 NTUs,” remarks Chardard.
Underwater cleaning system protecting surfaces
Traditional underwater cleaning systems making use of abrasive brushes or high-pressure jetting remove significant layers of antifouling paint and make the surface vulnerable to the establishment of organisms. However, cavitation cleaning has absolutely no effect on the vessel paint. “SleekShip’s cavitation cleaning system was specifically engineered for light biofouling cleaning levels (levels of fouling 1-2) and integration on a lightweight inspection-class remotely operated underwater vehicle (15 kg),” notes Chardard. Its operation principle relies on the momentary formation and collapse of tiny vapour-gas bubbles as they approach the cleaning surface. The resulting shock waves gently remove biofouling from the hull. Thanks to its novel control and machine learning algorithms, the SleekShip technology produces reports in less than 2 hours for an average vessel without the need of expert operators. By directly tackling the current inefficiencies in biofouling management, SleekShip will enable huge cost savings and contribute to decreasing CO2 emissions by over 100 million tonnes within 5 years after market launch.
Keywords
SleekShip, ship, biofouling, hull, Subsea Tech, cavitation cleaning, turbid waters
