Washing system for nets and hulls
Sustainable net cleaning
Net cleaning is all about creating an ideal environment for the fish. By removing algae from the net, one maintains a good flow of water through the net, thus ensuring the best possible oxygen conditions for the fish, while also removing a breeding ground for all the organisms that can develop in this algae.
The challenge is to get the net clean without damaging it, and with minimal impact on the impregnation intended to prevent the accumulation of algae going forward. ScaleAQ delivers MEOX net cleaners whose patented cavitation washing method make them uniquely gentle, even during high-pressure washing.
Cavitation washing technology
Cavitation is the rapid formation and collapse of bubbles in a liquid. MEOX net cleaners are specifically designed to allow aquaculture practitioners to use cavitation technology to wash nets and other equipment. Millions of tiny air bubbles in the water flow create a jet that hits the net. Because it consists largely of air, even at high pressure this jet is far “softer” than a pure jet of water. Air, or more accurately the steam bubbles formed in the washing unit, implodes when it hits the surface that is to be washed. The implosion creates pressure waves that contribute to the washing effect. This results in very gentle washing, even at pressures up to 200 bar.
During the period 2015–2019, Sintef undertook a project to improve understanding and advance the development of available washing technologies. Low pressure (80 bar), high pressure (200 bar) and cavitation washing (200 bar) were tested. The results of the project showed that washing with low pressure produced little washing effect, and actually resulted in considerable damage to the net. High-pressure spraying yields good results in terms of washing, but was also documented to be very destructive to the impregnation and reduced it by between 21% and 31% after just one washing cycle. After 35 washes, up to 90% of the impregnation was gone. The low-pressure washing removed 5–9% of the impregnation after one wash and 40–46% after repeated washing. Cavitation washing at a full 200 bar, (the same as high-pressure) was found to have no impact after a single wash and to have stripped away only 2–9% of the impregnation after repeated washes. Cavitation washing can also be used down to 80 bar for an even gentler effect.
The conclusion: Cavitation washing and high-pressure washing work, but cavitation washing is by far the gentlest washing method for both fish farm nets and other objects that require washing.
Wear and tear on fish farm nets poses several different types of sustainability challenges. Undetected holes resulting from excessively hard washing can lead to escaped fish, and nets that are washed too hard will have a shorter lifespan than nets that have been gently washed through a single exposure. We estimate that nets washed with MEOX net cleaners will withstand an additional generation of use with minimal maintenance.
Reduced fuel consumption
With this technology, far less energy is needed to wash the nets. This is because one uses less water, i.e., smaller pumps that require less energy. We have seen that energy needs can be reduced all the way down to 1/3 compared to conventional washing. For large pumps and large diesel engines that use up to 100 liters of fuel per hour, reducing energy needs can quickly result in enormous savings. Low consumption simplifies the electrification of washing and makes it possible to wash nets using battery power alone. Energy consumption can be lowered so much that it actually enables the use of power on the net pens for operation and/or charging.