Norwegian scientists have for decades worked on different applications of the bubble curtain technology. As examples, we use the technology to keep our fjords free of ice in the winters by lifting up warmer and more saline water from the depths, and also to canalize and collect plastic from fjords, rivers, and canals.
We need to undertake serious research and testing in order to push the boundaries of what is possible to achieve with the bubble curtain, and we are proud to call ourselves the frontrunners on this journey!
RECENT APPLICATIONS OF THE BUBBLE CURTAIN TECHNOLOGY
The well-known technical principle that the release of submerged air will create a vertical circulation of the water masses – called a bubble curtain – has been implemented to lift deeper and more saline water to the surface, thus lowering the freezing temperature and preventing freezing in fjords and marinas.
The same principle has also been used to lift nutrients from intermediate depths to the surface. Field tests with a towed, submerged bubble raft used as a zooplankton harvester showed promise for the efficiency of wide bubble sources.
During the last years, bubble curtains have been used as a prospective mitigation option against piling noise. California Department of Transportation initiated a pile installation demonstration project to assess this possible effect. Their conclusion was that a modified air bubble curtain may reduce the necessary safety zone during piling.
The German government has set mandatory limits on offshore underwater sound levels from wind farms. To meet the new standards, bubble curtain concepts have been tested for noise attenuation, and the first offshore application of a bubble curtain has been developed at the Borkum West II wind farm in the North Sea.
In the last few years, SINTEF has modeled and assessed the potential of using a wide bubble barrier as a countermeasure in an oil spill situation. Various meso- and large-scale tests showed that a distributed bubble source, a so-called bubble raft, was more effective for containing an oil slick than a single line bubble curtain. The improvement was due to the reduced bubble-induced turbulence. A field test in a strong tidal sound in Norway was the final validation of the bubble raft's capability to retain an oil spill even in strong currents. Two years later SINTEF performed a feasibility study and presented necessary dimensions and details for a bubble oil boom for a power plant facility in Spain.
The world's largest reef system, the Great Barrier Reef off the coast of Australia, has for years been exposed to severe bleaching. Coral bleaching is a phenomenon in which stressed corals expel algae and turn white, often because of high water temperatures. In an attempt to save the corals, Australian researchers have started to pump up colder water from below to reduce the high temperatures in the coral area.
The Norwegian seismic company, PGS, is working on an application of the bubble curtain technology to collect plastic from the ocean by blowing the particles up to the surface. They will use a bubble boom towed by two vessels and submerged to about 50 m depth. The ascending plastic will be collected when it reaches the surface.