The Ocean Cleanup announced that after a 6-week testing campaign, its main technical challenge is solved by modifying the system to move at a consistent speed through the plastic. The slow-down configuration was most effective in the trials.
The Ocean Cleanup’s first attempt to collect plastic was deployed last year, with the System 001, also known as Wilson. After months of testing, the organization took Wilson back to port in the first days of this year after it suffered a fatigue fracture.
This was not ideal, but both the diagnosis and solution came quite easily. The more complicated challenge was the system’s inability to retain plastic; instead of consistently going faster than the plastic, it alternated between going faster and going slower than the plastic. This meant plastic would float into the system, as planned, but then float out again
As there wasn’t a single obvious fix to this, they decided to set up the upgraded design, System 001/B, in a more modular fashion. This allowed to trial configurations that both sped up the system and slowed it down, in an attempt to find one that would result in a consistent speed difference between the system and the plastic.
[smlsubform prepend=”GET THE SAFETY4SEA IN YOUR INBOX!” showname=false emailtxt=”” emailholder=”Enter your email address” showsubmit=true submittxt=”Submit” jsthanks=false thankyou=”Thank you for subscribing to our mailing list”]
System 001/B was launched in late June, which was followed by a six-week testing campaign to test slowing down the system using a parachute anchor and test speeding up the system using large inflatable buoys.
All configurations performed better than Wilson, as in all tests the system generally experienced a positive speed differential, meaning that the plastic entered the system from the correct side. However, the winning concept is the slow-down approach, in which a parachute is used to slow down the system as much as possible, allowing the natural winds and waves to push the plastic into the system.
In the slow-down configuration, we haven’t witnessed a negative speed differential at all, with plastic always arriving through the front, but never drifting out of the opening again. Hence, this is the concept we’ll be moving forward with
During the tests, the plastic was concentrated by System 001/B by a factor of about up to 10.000. If the organization would do this to the whole patch, it would take the plastic distribution down from twice the size of the state of Texas, to 1/35th the size of the city of Houston, thus proving the concentration effect.
However, when they modified the design from System 001, they moved the screen forward slightly, away from the floater pipe, to eliminate the rail connection, which was the cause of the fracture, and simplify the design.
This made the plastic able to cross over the cork line, thus not considered as within the boundaries of the system, because there is no screen underneath the floater pipe, so it cannot be considered caught, as it is not securely retained in front of the screen.
The Ocean Cleanup will try to solve this by massively increasing the buoyancy and height of the cork line of the screen. The floats of the current cork line measure 15 cm in diameter. In comparison, it will now be using three rows of 32 cm floats stacked on top of each other, creating a total height of about half a meter.
Production has now been completed on this modification and is on its way to the patch, expected to arrive soon.