System and method for cleaning of biofouling and pathogens and use of the system

Abstract

System, method and use for cleaning structures submerged into water or affected by water spray, flows of water and volumes of water, from biofouling and / or pathogens. The system is distinguished in that it comprises: a number of laser units, wherein each laser unit comprises a fluid tight housing containing a laser source, such as laser array diodes, laser diodes or other laser or light source feasible for the purpose, electric power and cooling, coupled to the laser units, wherein the laser units are arranged so as to provide full coverage of laser irradiation for rendering biofouling and / or pathogens harmless when operatively positioned or moved relative to said structures, flows of water or volumes of water.

Description

[0001] SYSTEM AND METHOD FOR CLEANING OF BIOFOULING AND PATHOGENS AND USE OF

[0002] THE SYSTEM

[0003] Technical Field

[0004] The present invention relates to cleaning of biofouling and pathogens, for rendering biofouling harmless and rendering pathogens harmless. The cleaning takes place subsea, in splash zones, in flows of water or in stagnant volumes of water. More specifically, the invention relates to a system and a method for cleaning surfaces from biofouling and / or pathogens, such as ship hulls, containment walls, windmill structures, streamers for seismic surveillance, anchoring structures, and also for cleaning fluid contents, including flowing fluid and / or stagnant fluid, by rendering the biofouling and / or pathogens harmless. The invention also relates to uses of the system.

[0005] Background Art

[0006] On a clean ship hull floating on seawater, or in general any structure in or near surface or submerged within the zone where light contributes to photosynthesis, biofouling starts to form after few minutes, starting as proteins, diatoms and bacteria settling on the submerged part of the hull surface. After a few hours, a microbial biofilm starts to form. Then, formation of microfouling starts, wherein the biofilm receives secondary colonizers. After days or weeks, the microfouling will allow attachment of invertebrate larvae. Later, invertebrate larvae and algae will grow, forming macrofouling, which can grow very thick with algae and calcareous species.

[0007] The effect on fuel consumption for a ship caused by biofouling is surprising. Increase of 25% of fuel consumption caused by only 0,5 mm thickness of soft biofouling with 50% hull coverage on a 175 m bulk carrier has been reported. 55% increase in fuel consumption has been reported with 5 mm thickness of barnacles (small calcareous fouling or weed) and only 1 % coverage on a 320 m tanker.

[0008] Reducing the overconsumption of fuel caused by biofouling on ships will contribute significantly to the reduction of greenhouse gas emissions and help accelerating the shift towards a more sustainable economy. Other structures facing the same or similar problems are anchoring structures, and static or dynamic structures being subject to increased stress, such as streamers towed through water for receiving seismic signals, aquaculture structures, and more.

[0009] Another effect of biofouling is spreading of invasive species, resulting in damage to existing ecosystems. On the website of IMO, the International Maritime Organization, the United Nations specialized agency for the safety and security of shipping and the prevention of marine and atmospheric pollution by ships, a non-exhaustive list of invasive species and effects caused by the invasive species can be found, at: inyasiye-Species.aspx

[0010] Said spreading is via organisms on ship hulls or via ballast water.

[0011] A further serious problem, not well known yet, is spreading of diseases, such as ILA (infectious salmon anaemia), PA (pancreas) and SARS (severe acute respiratory syndrome) virus, between salmon farming plants and further to other aquaculture facilities. For example, service vessels such as well ships used extensively in aquaculture, may transport disease from one plant to another. Unwanted parasites, such as salmon lice, and other pathogens and parasites can probably spread likewise.

[0012] A further problem is damage of antifouling coating on ship hulls or surfaces / structures like aquaculture structures such as cages for salmon farming, fibres of a streamer with hydrophones, and other structures, when removing biofouling by mechanical brushing or high-pressure water, since friction, chemicals and high-pressure flows may leach the active antifouling substances, such as copper, and wear the antifouling and any other coating, and spread hard substances such as calcareous fragments, and damage fibres of a streamer or fish farming cage. Spreading of biocides, copper and microplastics are the results, as well as damaging structure / fibres, according to the specific situation.

[0013] An additional problem is removal of biofouling and / or pathogens inside pipes, tanks, on intricate areas on ships, on windmill structures, wave power plant structures, cooling structures, anchoring systems, oil and gas installations, pipes, cables; on ships in dry docks or wet docks, and on areas subject to water spray, such as on windmill structures and support structures. Biofouling can be a step towards structural problems and operational problems and can initiate corrosion on the structure. Removal of biofouling in said contexts is a current industrial problem without good solutions yet. In addition, existing UV-based equipment, for example for water sterilization by UV (ultraviolet light) irradiation, can still become more effective and better technology would be welcomed.

[0014] The objective of the present invention is to provide a system and a method contributing to reducing or eliminating some or all of the problems described above.

[0015] Summary of invention

[0016] The invention provides a system, according to claim 1 , for cleaning structures submerged into water or affected by water spray, flows of water and volumes of water, from biofouling and / or pathogens.

[0017] The system is distinguished in that it comprises: a number of laser units, wherein each laser unit comprises a fluid tight housing containing a laser source, such as laser array diodes, laser diodes or other laser or light source feasible for the purpose, electric power and cooling, coupled to the laser units, wherein the laser units are arranged so as to provide full coverage of laser irradiation for rendering biofouling and / or pathogens harmless when operatively positioned or moved relative to said structures, flows of water or volumes of water.

[0018] Some of the preferred embodiments of the system of the invention are defined in dependent claims.

[0019] The laser units are apparently novel and inventive per se. The number of laser units are from one, two or more, preferably a plurality of laser units, up to a number providing a practical and feasible system for the specific purpose. The fluid tight housing of each laser unit, containing a laser source operatively coupled to electric power for laser generation, and cooling, provides marinized laser units feasible for subsea service.

[0020] The system of the invention, preferably comprising two or more laser units simultaneously irradiating the surface and / or volume to be cleaned, apparently is novel and unique. The system of the invention is designed to be capable of irradiating at an intensity and coverage destroying the biofouling and / or pathogens, rendering the biofouling and / or pathogens harmless and dead, which in this context is referred to as cleaning the surface and / or volume of biofouling and / or pathogens, without harming coating or fibres. The detailed structure, parameters and functionality required, as determined by extensive research and testing, are described in detail below. Research and testing indicate that the dead biofouling on most coatings, such as coatings based on silicones, will fall away instantly or quickly when the ship starts sailing or the surface object moves relative to the water, thereby the surface will be literally cleaned. However, biofouling rendered harmless by the system of the invention on coating based on metal-containing antifouling, such as copper, may require active steps such as brushing and / or water jetting for removal and / or collection. In this context the term pathogens include viruses, bacteria and parasites on surfaces and / or in water.

[0021] In this context, moving the laser unit, array or row of laser units relative to a surface or volume of water, includes arranging the laser unit, array or row stationary on a structure and moving the water relative to the structure, and moving the laser unit, array or row relative to a structure or volume.

[0022] In this context, an array is a two-dimensional structure in an orthogonal x-y coordinate system or on the inner or outer surface of a cylinder structure or other three-dimensional structure, curved or double curved.

[0023] The system and method of the invention can render harmless soft biofouling at thickness from start of formation up to at least 3, 4 or 5 mm thickness, research and testing have revealed. Thick biofouling, such as macrofouling containing calcareous species and algae seaweed, often termed macrofouling, is not effectively made harmless by the system and method of the invention.

[0024] For many embodiments, the laser unit or units of the system of the invention preferably is coupled to or integrated into an ROV (Remotely Operated Vehicle), AUV (Autonomous Underwater Vehicle), robot or craft / vehicle, capable of moving said laser units along a submerged surface, such as along a ship hull, or precisely cleaning a submerged sensor or heat exchanger or other submerged structure or volume for biofouling and / or pathogens. In other preferable embodiments, the system can be arranged on a manipulator arm, be operated with a quay crane, or is configured for operation by a diver, preferably having buoyancy elements integrated to have near neutral weight as submerged. For many preferable embodiments, the system of the invention is piggybacked on existing robot (ROV, AUV) systems or cleaning and / or collecting systems. For many other preferable embodiments, the system of the invention is arranged in water inlets and / or outlets for aquaculture, such as RAS (recirculating aquaculture systems) and closed or semi-closed plants or tanks for aquaculture, and in water inlets, water outlets and / or containment volumes in well boats and other service vessels for aquaculture. For inlets and outlets, the laser array(s) or row is preferably arranged in the outer wall on at least one or two sides or spaced around the circumference at angular intervals as arrays or rows of lasers with the lasers units directed inwards so as to irradiate the full volume inside the inlet or outlet and the full internal surface of the inlet or outlet. Alternatively, or in addition, several laser arrays or rows and / or a central coaxial laser array irradiating outwards is arranged in the inlet and / or outlet. For tanks and other containments, the laser array(s) is preferably arranged in the outer wall on at least one side or in two or several walls with the lasers directed inwards so as to irradiate the full volume inside the tank and the full internal surface of the tank. Alternatively, or in addition, several laser arrays and / or a central laser array irradiating outwards is arranged in the tank or containment, such as a number of arrays arranged evenly in the volume to irradiate the full volume.

[0025] For embodiments with sterilization and / or cleaning of potable water or water for other use, laser unit arrays and / or rows are preferably arranged around the circumference at angular intervals or on at least one or two sides of a sterilization unit where the water flows through, and / or is arranged as a coaxial central laser array irradiating outwards, and / or is arranged as a number of laser arrays arranged in a larger volume to be irradiated, irradiating outwards, so as to cover the full volume by the combined effect of the arrays and / or rows.

[0026] The invention also provides system embodiments for open cage aquaculture, particularly feasible for open cage plants with a floating ring structure around the cage and / or a bridge arranged diagonal over the cage, wherein the diagonal bridge preferably can rotate over the cage, wherein the laser units, array(s) and / or rows, are arranged for irradiating downwards and outwards and / or inwards from the bridge and / or ring structure. Preferably, laser unit systems of the invention are arranged movable to a floating ring structure or other floating structure around or between net cages. Preferably, that laser unit systems of the invention are arranges so as to irradiate downwards into the water but inclined outwards through a net cage structure, preferably not directed to where the fish is contained but downwards and slightly outwards inclined through the net, movable around the net and up and down from a ring structure or a bridge structure. Preferably the net can be raised up during irradiation. In a preferable embodiment, the system of the invention comprises an array or row of laser units arranged so as to be lifted or lowered from a vehicle or ROV or AUV that can move around the cage, operable from a ring structure of the cage, while the array or row is moved along the inside of the net, optionally outside the cage, irradiating outwards and downwards through the net, optionally inwards and downwards, wherein in principle one revolution of laser irradiation from top to bottom and around the net cage cleans the net cage. Cleaning of open cage (open nets) aquaculture structures can thereby be effected and / or be improved and periods between fish farming in the nets can be significantly shortened, from months to weeks or from weeks to days. In addition, the problems with pathogens, including parasites, can be reduced and fish health can be improved. In other preferable embodiments, one or more ROVs or ALIVs with a system of the invention integrated or operatively arranged can be used for cleaning the net cages, pipes and other submerged or immersed structure.

[0027] The array or row of laser units of the system of the invention has three main embodiments:

[0028] Firstly, comprising a laser array of at least 2 x 2 laser units, closely packed with each laser displaced from the neighbouring lasers by a suitable distance ensuring full coverage of the surface or volume to be cleaned when moving the array in at least one direction along or relative the surface or volume to be cleaned. Preferably, every second row is displaced half the distance between laser units compared to the row above and below. Alternatively, the displacement of laser units is slightly displaced for each row and / or column, for the full row in one direction or symmetrically about a mid-column- or mid-row position in opposite directions.

[0029] Secondly, comprising a laser array of at least 2 x 2 laser units or a row of at least 2 laser units, closely packed and arranged resulting in full coverage of the surface or volume to be cleaned in a single pass relative to the surface or volume. For these embodiments, quadratic or hexagonal or otherwise shaped laser units are packed closely, adjacent element to element. This represents the closest type of arranging the laser units.

[0030] Thirdly, comprising a laser array of at least 2 x 2 laser units or a row of at least 2 laser units, packed and arranged, wherein some or all of the laser units comprise a spreading lens, resulting in that a full surface or volume passed by moving the laser array relatively to the surface or volume to be cleaned is covered. For this embodiment, the effect or intensity is spread over a larger area or volume for each laser unit, and the laser units are not necessarily closely packed or displaced for full coverage, since the spreading provides full coverage of the area or volume to be cleaned.

[0031] The cleaning system of the invention also comprises any combination of two or three of the main embodiments defined above.

[0032] As understandable from the above, for some embodiments of the system of the invention the laser array(s) or row(s) are moved relative to an object to be cleaned, while in other embodiments moving fluid is cleaned when flowing through static objects like inlets or outlets comprising array(s) and / or row(s) of lasers operatively arranged.

[0033] In some embodiments of the system of the invention, the laser array is arranged in a ring-shaped tool, preferably hinged, to be arranged around a streamer, fibre rope, chain, pipe or other longitudinal object to be cleaned. For streamers, chains, fibre ropes, wires, hoses or cables, in some embodiments the system of the invention comprises arrays or rows of lasers as operatively arranged at or integrated in coiling-winding distribution arrangements, for even winding-unwinding on a reel or drum whilst cleaning for biofouling and / or pathogens.

[0034] A preferable embodiment of a system of the invention comprises a laser array with for example 16 x 9 rows, with displaced position between every second row in one direction, positive or negative half the distance between laser units in a row, providing laser effect controllable by moving the array along a surface to be cleaned at a specific speed, and / or controlling the laser intensity, and / or controlling fluid flow rate through an inlet or outlet. In other preferable embodiments, the laser units are displaced one third of the distance between laser units for every row, so that every third row are in line.

[0035] The number of laser units can be for example 9 in rows 1 and 3 and 8 in row 2, wherein row 2 is displaced half the distance between laser units. The number in even and odd rows and / or columns must not be equal, ± 1 is feasible.

[0036] An array of lasers means at least 2 x 2 lasers or laser units arranged side by side, as at least 2 rows and 2 columns. The number of rows and columns are preferably larger, such as 2x2, 3x3, 4x4, 5x9, 6x12, 16 x 9 and any other combination not resulting in being too heavy and / or large to handle by a robot (ROV, AUV) or otherwise. As integrated with a robot (ROV, AUV), the width of the array preferably is equal to the width of the robot (ROV, AUV), for example the array is 0,5 m wide and 0,3 m long. The number of column x number of rows is determined by the intended intensity and area and / or volume for the specific case.

[0037] Full coverage of the laser array or row means that any point at which the laser array or row is positioned or moved over, in at least one positive or negative direction, is subject to laser radiation at an accumulated intensity sufficient for the purpose of killing the biofouling and / or pathogens by the laser irradiation. What this means will be clear from the detailed description.

[0038] Moving the laser array or row means moving along or relative to the surface and / or volume to be cleaned. However, for the second and third main embodiment, moving also includes positioning the array successively over areas to be cleaned and irradiating for a prescribed period, for providing sufficient irradiation for the purpose. Embodiments with only a row of laser units arranged closely with coverage between laser units, possible for the second and third main embodiment, must be moved transverse relative to the row for relative fast and effective full coverage.

[0039] The system may include removal and collecting of the biofouling. For ships travelling in local waters, the irradiated and thereby dead biofouling and pathogens can probably be allowed to fall from the ship hull when the ship is sailing, since there will be no risk of spreading of invasive species or diseases.

[0040] The system preferably also comprises equipment for separating and collecting pathogens and / or soft biofouling, such as a hydro cyclone arranged in an inlet flow or outlet flow, with pathogens and / or soft biofouling directed through a reject outlet, for further use, separation or disposal.

[0041] In some embodiments, the dead biofouling and any pathogens are removed and collected, for example by high pressure nozzles and / or brushes and / or water flushing and / or vacuum suction, preferably including sucking in the killed, loosened biofouling for collecting and possible later use as fertilizer, for biogas production, soil production or for disposal.

[0042] Power is electric power via an umbilical, preferably a combined handling and power umbilical, or is by an electric power system. Alternatively, power is by batteries, such as Li batteries or Li-ion batteries operatively coupled to or integrated in the system / ROV / AUV.

[0043] The operation is with an ROV, an AUV, a manipulator that can be on quay or on a vessel, by a quay crane, by divers, by operators in a dry dock or wet dock, or by other means, including fixed installations irradiating for example critical parts of pipes or equipment, for example irradiating subsea coolers for preventing biofouling and reduced efficiency by the biofouling. A typical robot (ROV, AUV) is about 0,5 x 0,7 m and weighs about 30 kg and is an observation robot (ROV, AUV) or a light work class robot (ROV, AUV), by robot (ROV, AUV) terminology, or is a larger work class robot (ROV, AUV).

[0044] The system, in a typical embodiment, operatively arranged to the robot (ROV, AUV), weighs about 20 kg submerged, resulting in about 50 kg weight in air. Larger systems for large ships or objects can be much larger and heavier, while smaller systems for coastal use, use from quays, and for covering intricate geometries can be much smaller and lighter for increased access and dexterity.

[0045] The laser used for the system and method of the invention can in principle be any laser or laser unit small enough and with sufficient intensity, and feasible for marinizing into laser units, preferably in an array or row of lasers, as described in the detailed description. The preferred lasers are blue laser diodes (LD), for several reasons. A supplier is for example Nichia, of Tokushima, Japan. Blue lasers provide minimum damping of light intensity through water, maximum match with chlorophyll wavelength sensitivity, good availability, and affordable cost. However, other lasers or light sources, also UV sources, can be included in the system for specific purposes.

[0046] The laser units are marinized for withstanding at least 3, 5 or 8 bar pressure, or higher pressure, as small gas filled, liquid filled or vacuumed containers with cooling as required and with common or individual intensity control. For large depth operation, the marinization can include liquid filling and pressure compensator, enabling operation down to hundreds of meters of depth.

[0047] Research has revealed that the irradiation by the system and method of the invention destroy the photo destructible pigments within the cells. More specifically, the laser attacks the phycoerythrin pigment. The effect can be observed visually since the biofouling changes colour when rendered harmless. Also, pathogens are rendered harmless by the laser irradiation. More specifically, the preferred blue lasers have ionizing effect, killing pathogens and parasites. The energy absorption generates heat, leading to cell death or severe impairment of cells. Blue laser light has 10-100 times lower absorption in water compared to UV.

[0048] In a preferred embodiment of the invention, the system of the invention comprises a bundle of optical fibres arranged in front of the laser array, row of lasers or a single laser unit being an array of lasers itself, for transmission of laser irradiation, wherein the site for irradiation can be remote from the actual laser array, row of lasers or single laser units. For example, a bundle of optical fibres arranged in an umbilical to be handled by an ROV can enable irradiation according to the invention without having the actual laser array, -row or -unit(s) subsea, which can be preferable for accessing difficult positions for irradiation and enable use of smaller, less expensive ROVs. Less power cables in the umbilical and less or no cooling subsea, can be enabled for some systems of the invention. The fibre bundle preferably is of rectangular geometry, for minimizing loss and facilitating control of irradiation. The fibre bundle preferably is designed for lowest damping of blue laser light at about 450 nm wavelength, for example comprising ZLLIV, ZLDLIV and / or ZLDUVCH fibers from Lightguide International (cf. Iightguide.com). In some preferable embodiments, the optical fibers have diameter in the same order of size as the wavelength of the laser waves, resulting in significant spreading of the laser irradiation. In other preferable embodiments, lenses are arranged in front of fibers for reducing the spreading, directing the irradiation more in one direction, which is preferable for confined geometries or volumes, whereby the fiber end (bundle of fiber ends) can be more remote from the target compared to embodiments with no lens.

[0049] The invention also provides a method for cleaning structures submerged into water or affected by water spray, flows of water and volumes of water, from biofouling and / or pathogens by laser irradiation, thereby rendering the biofouling and / or pathogens harmless. The method is distinguished in that the system of the invention is operated so as to provide full coverage of laser irradiation, by controlling laser irradiation coverage by one or more of the steps: controlling positioning relative to said structures, controlling velocity relative to said flows and structures, controlling positioning relative to said volumes, and controlling the laser intensity by adjusting an electrical power control.

[0050] The laser unit or units are directed at or oriented to the structure, surface or volume to be irradiated, as considered obvious and in this context included in the step “controlling positioning relative to said structures”. A combination of distance, relative velocity and / or laser intensity provides an intended accumulated full dosage of irradiation, the meaning and enabling disclosure of which are described in detail below. As must be understood by the person skilled in the art, there is no fixed combination of parameters that are in general correct, since the turbidity of water vary, the nature and thickness of biofouling vary and the nature and concentration of pathogens vary, and in some uses there are limits of full dosage of irradiation that should not be exceeded, as described in the detailed description.

[0051] The invention also provides use of the system of the invention and / or the method of the invention, for rendering biofouling and / or pathogens and / or parasites harmless by laser irradiation, for submerged structures, structures in the splash zone, for submerged parts of floating structures, for water inlets and outlets, for tanks and other containments, for aquaculture structures in the form of tanks or net cages, pipe structures and mooring structures, for streamers, for subsea coolers, for general cleaning of soft biofouling and\or for general cleaning and / or disinfection of water in stagnant tanks or containments or in flowing water.

[0052] Brief description of drawings

[0053] Figure 1 illustrates a typical laser array and laser unit of a typical embodiment of the invention.

[0054] Figures 2a and 2b illustrate a typical laser unit and a longitudinal section thereof, of a typical embodiment of the invention.

[0055] Figure 3 is a flow chart illustrating the laser array of a system of the invention.

[0056] Figure 4 illustrates a system of the invention for laser irradiation in a water inlet or outlet.

[0057] Figure 5 illustrates a system of the invention for laser irradiation in a tank containing water.

[0058] Figure 6 illustrates a system of the invention for laser irradiation of a streamer with geophones or general chain or fibre rope irradiation.

[0059] Figure 7 illustrates a system of the invention for laser irradiation of an aquaculture net cage.

[0060] Detailed description of the invention

[0061] Figure 1 illustrates the laser array 2 of a typical embodiment of the system 1 of the invention, only illustrating an array for clarity, as seen from underneath, and with one laser unit 3 highlighted for illustrating more details. When moving the laser unit array along positive or negative y direction (upwards or downwards, transverse to longest dimension), full coverage is ensured. A spreading lens 4 (not visible on Figure 1 ) on each laser unit 3 ensures that full coverage is achieved also in the transverse x-direction. The laser diode 7 is in this embodiment an array of laser diodes but can be a single laser. The result is a laser array according to a combination of the first and third embodiment as described above. This represents a preferable embodiment of the laser arrays, for many systems of the invention, since the investment cost is relatively low and the cooling requirement is reduced compared to closer arranging of the laser units. But more time for irradiation / lower speed of the robot and / or higher intensity of lasers and / or shorter distance between laser and biofouling and / or lower water velocity / larger arrays can be required, compared to closer arranging or packing of laser units. But all parameters are controllable and are preferably optimized or tailored for each case.

[0062] For embodiments without or with spreader lenses, individual intensity of singe laser units, or rows or columns thereof, can be preferable for full coverage. Examples are embodiments with uneven number of laser units in rows or columns, without full symmetry in orthogonal x and y directions, for example with odd number of rows.

[0063] Full coverage means that no area or volume irradiated has received less than 60%, 70%, 80% or 90% of the intended accumulated irradiation dose, preferably without exceeding a maximum accumulated dosage limit, if relevant for the embodiment. Preferably, overlapping radiation by neighbour laser units is less than 20%, 10%, 5%, 3% or 1 %, of the intended accumulated dose of irradiation.

[0064] Figures 2a and 2b illustrate a typical laser unit 3 as viewed from the side and a longitudinal centre section thereof, respectively, of a typical system embodiment of the invention. The piping 5 of the cooling system is visible, running through the mounting of the laser unit. Visible are also the laser diode 7, lens 4 and mirror 6 on top. In the longitudinal section, the spreading lens 4, typically a quartz spreading lens designed for the purpose, is easily recognizable. The laser diodes 7 themselves are in this embodiment also an array, but an array of laser diodes, closely arranged. Laser array diodes, laser diodes or other lasers feasible for the purpose are available commercially. Also, spreader lenses and feasible housings can be custom designed and built for the purpose, or can be found as commercially available components that can be modified or not and be arranged together by a person skilled in the art. The laser unit in general comprises a driver (circuit board, not illustrated in detail), a blue laser-diode array or a blue diode array, an optical system, and means for cooling, arranged in a marinized housing.

[0065] In most system embodiments mainly intended for rendering soft biofouling harmless, the array is coupled to or integrated in a typical robot (ROV, AUV) system for the purpose. The speed of the robot (ROV, AUV) / system of the invention on the surface to be cleaned, and the intensity, is controlled to ensure that the accumulated irradiation will be within the prescribed range for rendering the biofouling harmless while at the same time not damaging any antifouling coating below the biofouling. The distance between the laser array and the biofouling on the surface to be cleaned preferably is set to be constant by distance wheels on the robot (ROV, AUV), or is controlled by other means. For example, a constant or near constant distance, such as controllable within ±25%, ±10% or ±5% from a nominal distance in the range [0,05 - 1 m] is feasible, but the system of the invention can be effective up to above 5 m distance in clear water. Each laser unit is controllable within on / off and 1 - 200 w, preferably, whereby a feasible combination of all parameters can be enabled.

[0066] Figure 3 is a flow chart illustrating a typical laser array of the system of the invention. Positioning data is gathered from the robot (ROV, AUV). This information is the positioning and the speed of the robot. Biofouling detection is information on what kind and how much biofouling that is in front of the laser system, as visually observable, for example by an integrated camera. Norsjor effective cleaning matrix is a matrix that gives out the most effective cleaning parameters without damaging the antifouling. The parameters are radiation time (robot speed) and laser intensity. The Controller is the brain of the system. It uses information from the biofouling detection, positioning data and Norsjor effective cleaning matrix to control laser intensity (voltage) and robot speed. Power supply delivers electricity to the laser units. The power supply has a voltage regulator to control the intensity. The water cooling system is in the typical embodiments a closed looped water cooling system that cool down the lens system and blue laser diode arrays. Blue laser diode array comprises a number of blue diode laser units arranged as an array and connected in a parallel. The number of diode units of the arrays is not necessarily fixed but is found for each case. The number of diodes corresponds to the efficiency of the system. Lens systems are preferably included and are lenses that collimate the laser beam. Spreader lenses are added as required for the specific embodiment and use.

[0067] Laser intensity, accumulated when the array of the system is moved over the surface area to be cleaned, is sufficient to kill / damage the biofouling and pathogens, but below a limit causing damage / leaching to the antifouling / coating system or other structure hit by the irradiation, if relevant.

[0068] The laser units preferably have wavelength 420-499 nm, more preferably 430- 470 nm, most preferably 450 nm, since 450 nm window is a window that lets laser light through with minimum optical power loss. This corresponds to blue lasers.

[0069] The laser units, when turned on, preferably have intensity 1 - 200 w, preferably adjustable. This will enable killing / destroying / rendering harmless soft biofouling in thickness 0,0 - 8 or 5 mm, and the intensity, together with the specific coverage and speed of moving for the specific system, will enable the intended effect, as found by both research and testing. Rendering pathogens harmless will also be achieved by 1 - 200 w intensity for each laser unit. ILA (infectious salmon anaemia), PA (pancreas, also termed IPNV) and SARS (severe acute respiratory syndrome) can thereby be eliminated or strongly reduced in a plant for aquaculture. Preferably, also collected faeces, waste food and / or dead fish are irradiated by the system of the invention, since said viruses can spread through faeces, waste food and / or dead fish. The system of the invention is also effective for rendering harmless other pathogens than here exemplified.

[0070] The observed actual biofouling thickness estimate, based on visual inspection by the ROV / AUV or otherwise, and time since last cleaning, preferably is used as input for determining the required combination of intensity and speed for the radiation by the system of the invention.

[0071] Preferably, the system and method of the invention are used proactively, meaning frequent cleaning of biofouling with small thickness of biofouling, in the range 0-3 mm. Preferably, the intensity and speed is set so as to ensure that in any areas of 0 mm biofouling, the antifouling coating is not damaged.

[0072] Preferably, the system is used in water inlets and outlets for aquaculture and well boats or other service boats for aquaculture, and preferably also in water tank containments when not holding fish or other aquatic species that should not be harmed. This also includes ballast water inlets, outlets and tanks.

[0073] It is possible to find feasible operation parameters analytically, but usually after much research and testing. Antifouling coatings vary, type and thickness of biofouling vary, the permeability of laser irradiation and intensity versus volume or distance irradiated in water vary a lot according to the turbidity of the water, and type and populations and distribution of pathogens and parasites vary for different applications of the system, and it is in practice easier to build up / calculate an operation method matrix as part of the Controller. Many of said parameters vary through the year and for each location. To calculate intensity of the laser and radiation time multiple research attempts are applied in a matrix. Maximum intensity and radiation time is found through testing different antifouling coatings to find the destructive threshold. Each coating will have its own individual maximum destructive threshold to not harm the coating. Efficiency results (shortest time to lethally harm the biofouling and / or pathogens) from various biofouling tests with variable parameters such as laser intensity, radiation time and biofouling thickness will create the matrix for most effective cleaning. The preferably intensity of 1 - 200 w for each laser unit, preferably adjustable, will work for all or almost all typical situations. Intensity of 85 w for each laser unit can be a typical feasible intensity, according to practical testing, but numerous factors will influence each case or situation.

[0074] Reference is made to Figure 4, illustrating an embodiment of a system of the invention for laser irradiation in a water inlet or outlet 8, comprising one, two or more two-dimensional arrays of laser units, and / or rows of laser units, arranged around the periphery, irradiating inwards 2i , and / or arranged coaxially, irradiating outwards 2o, wherein water flowing 9 through the inlet or outlet receives sufficient irradiation for killing pathogens and parasites. The illustrated embodiment, in longitudinal section, comprises several arrays irradiating inwards, of which only two are indicated for clarity, and one coaxial array irradiating outwards. Such embodiments are preferred for water inlets and outlets for aquaculture, for well boats and other service vessels in aquaculture, and outlets from sewage treatment plants, grey water treatment plants, inlets and / or outlets from potable water treatment plants, inlets and / or outlets for ballast water tanks, and general cleaning of industrial water and wastewater from pathogens and / or parasites. The inlets and outlets are preferably without internal coating that can be damaged by the irradiation. Preferably said inlets or outlets comprises a reflective inner surface or coating reflecting and spreading the irradiation better in the inlet or outlet. The specific extent of laser units being sufficient in the form of arrays and / or rows, as combined with controllable intensity, depends on water flow rates and size of the inlets and outlets, and can be estimated analytically and verified by testing by following the guidance in this document, for each specific embodiment and use.

[0075] Further reference is made to Figure 5, illustrating a system of the invention for laser irradiation in a tank 10 or basin containing water. The arrangement of the laser arrays and / or rows of laser units are based on the same principles as for inlets and outlets, but the size of the tank or containment, and residence period of the contained water, are parameters that must be taken into account when designing the arrays and / or rows and distribution thereof for providing the functionality as required. The illustrated embodiment comprises two arrays 2o irradiating outwards, as indicated by arrows 11 . Said arrays irradiate outwards, comprising rows and / or arrays of laser units arranged around, along and from the ends of an inner cylindrical structure.

[0076] For inlets, outlets and containment volumes having circular cross-section shape, arrays and / or rows of lasers, preferably with a lens on all laser units, are preferably arranged around the inner periphery continuously or in angular steps, such as every 30° around the periphery. For large containments or inlets / outlets, arrays and / or rows of lasers are preferably or in addition or instead arranged coaxially and / or evenly inside, irradiating outwards. For example, well boats and / or ballast systems in ships, may comprise arrays in water inlet and outlets, as well as arrays in containments that can be used for storing / transport of fish or in containments for ballast water.

[0077] All structures and volumes for containing fish are preferably rendered harmless by cleaning from biofouling, pathogens and parasites before loading fish.

[0078] Figure 6 illustrates a system of the invention for laser irradiation of a streamer with geophones or general chain or fibre rope or pipe or tube irradiation. The arrays or rows, preferably at least two arrays or rows, are hinged and configured to circumvent the outer periphery of the streamer, chain or rope, or other elongated structure, so as to provide sufficient intensity of irradiation, at the relative speed between arrays / rows and streamer, chain or rope or other structure. In the illustrated embodiment, a system 12 of the invention, with hinge 13 and four arrays 2i irradiating inwards is illustrated. The arrays comprise spreader lenses (not illustrated) for full coverage and the hinge can be locked or unlocked automated, manually, by an ROV or by other means. Figure 7 illustrates a system 1 of the invention for laser irradiation of an aquaculture net cage. One system 1 of the invention is arranged to a ring structure 15 on top of the cage, and one system 1 of the invention is arranged to a diagonal, preferably rotatable, bridge 14 over the ring structure. Lowering and retrieving the system and laser arrays 2 of the invention, from the ring and bridge, can result in cleaning the cage net from biofouling and pathogens in hours. Working from a rotatable bridge 14, all parts of the net cage 16, briefly indicated, can be reached by controlled lowering, lifting, and positioning on the bridge. Working from the ring structure 15, thrusters can be required on the array 2, since the net takes form according to current and waves. For both embodiments, a camera is preferably included on the array unit, preferably also a distance measurement device and a recorder to be operated to document the full operation. The laser arrays can preferably be piggybacked on an ROV or AUV.

[0079] With the system of the invention, with blue laser units, the optical effect with up to 200 w nominal for each laser unit, is up to about 137 w, meaning up to about 3000 w optical effect for a typical system of the invention. Water clarity is a parameter somewhat out of control, but in clear water the irradiation can reach above 5 m and still having intensity as required. In very opaque water, such as in algae blooms, the laser can typically be effective up to at least 0,2 m. If practically achievable, prefiltering of water to be cleaned can be preferable. In typical conditions, an operative distance from 0 to 2, 3, 4 or 5 m is feasible, which also directs the distance between laser unit arrays or rows to be in similar distance apart or closer.

[0080] Very surprising in view of the presumption that UV light is best for irradiation since the energy is higher due to shorter wavelength, the blue laser provides tens of times better results in water for cleaning surfaces or water volumes from biofouling and / or pathogens and / or parasites. Some of the reason is longer reach or permeability, or less damping of the blue laser light compared to UV light. Another reason is that blue light is far stronger absorbed by chlorophyll a, b and c, respectively, than UV light.

Claims

Claims1.System for cleaning structures submerged into water or affected by water spray, flows of water and volumes of water, from biofouling and / or pathogens, characterized in that the system comprises: a number of laser units, wherein each laser unit comprises a fluid tight housing containing a laser source, such as laser array diodes, laser diodes or other laser or light source feasible for the purpose, electric power and cooling, coupled to the laser units, wherein the laser units are arranged so as to provide full coverage of laser irradiation for rendering biofouling and / or pathogens harmless when operatively positioned or moved relative to said structures, flows of water or volumes of water.2.System according to claim 1 , comprising an array and / or a row of laser units closely arranged.3.System according to claim 1 , comprising a laser unit, an array and / or a row of laser units coupled to or integrated into an ROV (Remotely Operated Vehicle) or AUV (Autonomous Underwater Vehicle).4.System according to claim 1 , comprising a laser unit, an array and / or a row of laser units, arranged inside fluid inlets and / or outlets, preferably coaxially inside, irradiating outwards; and / or arranged around the inner periphery continuously or in angular steps, irradiating inwards, covering the full volumethrough which water flows through the inlet or outlet; and / or if said inlets or outlets are not circular in cross section but quadratic or rectangular, comprising a laser unit, an array and / or a row of laser units on at least one side, irradiating from the at least one side covering the full volume containing water in the inlet or outlet.5.System according to claim 1 , comprising a laser unit, an array and / or a row of laser units, arranged inside a tank or containment for containing water, arranged coaxially inside irradiating outwards and / or arranged around the inner periphery continuously or in angular steps, irradiating inwards, covering the full volume in which water is contained, and / or if said tank or containment is not circular in cross section but quadratic or rectangular, comprising a laser unit, an array and / or a row of laser units on at least one side of the tank or containment, irradiating from the at least one side covering the full volume containing water.6.System according to any one of claim 1-5, comprising an array of laser units with a number of columns x number of rows laser units, with displaced position between every second row in one direction, positive or negative half the distance between laser units in a row, or one third displacement for every row successively.7.System according to any one of claim 1-6, wherein some or all of the laser units comprises a lens, preferably a quartz lens, further comprising a laser or diode driver (circuit board), and an optical system.8.System according to claim 1 , further comprising optical fibres arranged from thelaser units, during operation arranged to reach inside otherwise inaccessible geometries or surfaces.9.System according to any one of claim 1-8, wherein the laser has wavelength in the range 400 - 499 nm, more preferably 430-470 nm, most preferably about 450 nm.10.Method for cleaning structures submerged into water or affected by water spray, flows of water and volumes of water, from biofouling and / or pathogens by laser irradiation, thereby rendering the biofouling and / or pathogens harmless characterized in that the system of any one of claim 1-9 is operated so as to provide full coverage of laser irradiation, by controlling laser irradiation coverage by one or more of the steps: controlling positioning relative to said structures, controlling velocity relative to said flows and structures, controlling positioning relative to said volumes, and controlling the laser intensity by adjusting an electrical power control.11.Method according to claim 10, comprising one or more of the steps: moving the laser unit, array or row of laser units in at least one direction along a surface or structure to be cleaned, and / or arranging the laser unit, array or row of laser units to a water volume moving relatively to the laser unit, array or row of laser units, and / or by arranging the laser unit, array or row of laser units operatively to a contained water volume or a stationary structure.12.Method according to claim 10, whereby the biofouling and / or pathogens rendered harmless is dead and is allowed to loosen from the structure, when the structure is moved relative to water, such as a ship hull when the ship starts sailing.13.Method according to claim 10, whereby the harmless, dead biofouling and / or pathogens is removed and / or collected.14.Method according to claim 10, whereby pathogens, including parasites, bacteria and / or viruses are rendered harmless in volumes of water, and is allowed to retain in the water or is collected by filtering or other separation method.15.Use of the system according to any one of claim 1-9 and / or the method according to any one of claim 10-14, for rendering biofouling and / or pathogens and / or parasites harmless by laser irradiation, for submerged structures, structures in the splash zone, for submerged parts of floating structures, for water inlets and outlets, for tanks and other containments, for aquaculture structures in the form of tanks or net cages, pipe structures and mooring structures, for streamers, for subsea coolers, for general cleaning of soft biofouling and / or for general cleaning and / or disinfection of stagnant water in tanks or containments or in flowing water.

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