A central structure of a fish farming tank

Abstract

The invention provides a central structure (often termed a cigar) of a fish farming tank or for arranging into a fish farming tank, wherein the central structure is arranged coaxial to a central vertical axis of the fish farming tank. The central structure is distinguished in that it comprises a double coaxial pipe structure wherein an outer pipe thereof is closed towards a bottom of the tank and extends from a tank bottom elevation up to an elevation above a fish farming operation water level, wherein the outer pipe comprises openings for flow of water evenly distributed around and along the outer pipe from a distance above the tank bottom level up to a fish farming operation level of the fish tank, and wherein an inner pipe thereof is closed towards a bottom of the tank and extends from a tank bottom elevation up to within a control range of the fish farming operation water level, wherein the inner pipe has closed wall without openings for flow, wherein the water flowing through the openings of the outer pipe flows from a volume between the outer pipe and the inner pipe out over an upper end of the inner pipe, down the inner pipe and through a flow outlet through the bottom of the tank. The invention also provides a floating plant for aquaculture, an outlet for use in a plant for aquaculture, a method for unloading fish and a constriction structure for unloading live fish.

Description

[0001] A CENTRAL STRUCTURE OF A FISH FARMING TANK

[0002] Field of the Invention

[0003] The present invention relates to aquaculture in general, such as aquaculture of salmon and other salmonids. More specifically, the invention relates to a central structure, an outlet opening concept, and a plant for aquaculture, and a method for unloading fish from a plant for aquaculture.

[0004] Background of the invention and prior art

[0005] Aquaculture is vital for providing food for the growing population. About 50% of all seafood originates from aquaculture. Aquaculture of salmon and other species of fish are substantial industries, involving a large chain of activities, structures, personnel and capital.

[0006] Fish health is a serious issue, both from ethical and economic point of view. The mortality of salmon farming in Norway in 2023 was as high as 16,7 %. In addition, the use of medicines and chemicals cause major concern.

[0007] Escape of farmed fish is another severe problem, threatening the populations of wild salmon. In Norway, the Norwegian Fish Directorate estimates that an annual average of about 140 000 individuals of salmon escaped from aquaculture during the last 10 years, the real number may even be larger. Minimizing or eliminating the continued blooming of sea lice, caused by intense aquaculture in open cages, would be beneficial for wild salmon populations and would reduce mortality significantly. Reduction of the so called “winter wounds” is also beneficial for improving fish welfare and consequently delivering a better product to the market. Winter wounds are primarily a result of high occurrence of the Moritella Viscosa bacteria and can be reduced or eliminated by water treatment at the water intakes. Pollution is a further serious issue. In Norway, in 2023, about 360 metric tons of copper leached out due to aquaculture, and between 7-800 000 metric tons of feces, and large quantities of uneaten food, in addition to lots of nets, ropes and various polymer structures of hardly degradable types. Chemicals used for reducing growth of algae and other organisms on the structures cause increasing concern, based on recent findings.

[0008] Closed plants for aquaculture on land and closed plants for aquaculture floating in the sea appear to be the solution for the above-identified problems. However, finding concepts reducing cost and solving biological and technical challenges are not easy.

[0009] In this context, closed floating plants means plants with closed wall and bottom, impermeable for water, without leakage of water in through wall or bottom from the sea, eliminating the lice problem, and without leakage of water, feces, waste food or pollution out through wall or bottom, eliminating the severe pollution problem. The top of the tank of the plant is closed or open to the atmosphere and daylight.

[0010] Cost is a serious issue, especially since large investments have been made in open cage aquaculture by large companies over many years and investing heavily in other more sustainable but still quite risky technologies before full revenue of earlier investments have been achieved is not easy.

[0011] A demand exists for cost-effective concepts and solutions solving or significantly reducing one or more of the challenges mentioned above.

[0012] Extensive searching has not revealed any known fish farming outlet or aquaculture plant, central structure for an aquaculture plant or method for unloading live fish from a plant for aquaculture, close to the concept of the present invention.

[0013] Summary of the invention

[0014] The demand is met by each of the central structure, the outlet, the floating plant and the method for unloading live fish of the present invention, as defined in independent claims, to which reference is made. Some of the preferable embodiments thereof are as defined in dependent claims, to which reference is made.

[0015] The invention provides a central structure (often termed a cigar) of a fish farming tank or for arranging into a fish farming tank, wherein the central structure is arranged coaxial to a central vertical axis of the fish farming tank. The central structure is distinguished in that it comprises a double coaxial pipe structure wherein an outer pipe thereof is closed towards a bottom of the tank and extends from a tank bottom elevation up to an elevation above a fish farming operation water level, wherein the outer pipe comprises openings for flow of water evenly distributed around and along the outer pipe from a distance above the tank bottom level up to a fish farming operation level of the fish tank, and wherein an inner pipe thereof is closed towards a bottom of the tank and extends from a tank bottom elevation up to within a control range of the fish farming operation water level, wherein the inner pipe has closed wall without openings for flow, wherein the water flowing through the openings of the outer pipe flows from a volume between the outer pipe and the inner pipe out over an upper end of the inner pipe, down the inner pipe and through a flow outlet through the bottom of the tank.

[0016] The central structure preferably further comprises a pipe section, often termed a sleeve, adjustably positioned over and to the top elevation of the inner pipe, for adjusting an effective height or elevation of the inner pipe upper end and thereby adjusting freeboard and effective water volume in the fish farming tank and an outlet flow rate therefrom out through the inner pipe of the central structure without having or operating valves or other control mechanisms inside the central structure or below or further downstream. This is far more important than may be easily acknowledged. The sleeve can be operated, that is used for adjusting height of the inner pipe upper end, and thereby adjusting freeboard and effective tank water volume, for example to fit a specific weather criteria or weather forecast or size of fish. More specifically, by using the sleeve to adjust freeboard for positioning the plant in smooth or harsh weather conditions, hence giving the possibility of maximizing the fish tank volume corresponding to the weather criteria on site. Operating draught can be adjusted corresponding to the height of the inner pipe, by adjusting sleeve position. A standard tank can be suitable to operate on various locations but is easily optimized with respect to tank volume versus weather criteria (freeboard adaptation). When weather forecast is worsening, the operators can lower the sleeve to increase freeboard hence increasing a safety margin. When the bad weather is over, the sleeve can be raised again to maximize the water volume inside the tank. When fish grows larger and will take advantage of increased flow rate / flow velocity through / in the tank, adjusting the sleeve position down to increase flow rate and velocity is a surprisingly easy and effective control mechanism. These features and functionality enable maximizing cost efficiency (CAPEX in terms of cost per cubic meter fish tank water volume), combined with safety and securing health of the fish.

[0017] The central structure preferably is comprising an integrated outlet with an outlet opening through which live fish can be unloaded from the plant, wherein the outlet further comprises: a hatch, a mechanism operatively arranged to the hatch, for arranging the hatch in a closed position with the hatch covering the outlet opening or an open position with the hatch not covering the outlet opening, an outlet conduit extending between the outlet opening in an end of the outlet conduit facing a fish farming tank of the plant for aquaculture and an opposite end of the outlet conduit ending in a wellboat or other facility feasible for loading live fish, wherein the plant is in an unloading mode, wherein live fish is or can be unloaded from the plant and the hatch is in the open position, wherein the hatch comprises openings of size and distribution allowing feces and waste food, but not live fish, to pass through the openings of the hatch as entrained with an outlet opening flow of water from the fish farming tank, wherein the plant is in a fish farming mode, wherein the hatch is in the closed position covering the outlet opening, locking out live fish from passing through the outlet opening. Preferably, one, two, three, four or six such outlets are integrated in the central structure, arranged evenly around the circumference towards the bottom floor of the tank. The central structure preferably is comprising an extendable outlet pipe, enabling adjustment of the outlet elevation of a lower end of the extendable outlet pipe, preferably in the form of an integrated telescope-pipe configuration of one or more telescopic pipe parts, with a weighted lower end thereof and a winch, a motor or similar device operatively arranged to the telescope-pipe structure. Preferably, the central structure is made of steel or a combination of steel and / or polymer and / or GRP; preferably with steel for lower parts, including any integrated outlets through the outer pipe, and PE (polyethylene) of potable water quality and / or GRP (Glass Fiber Reinforced Polymer), for elevation above any integrated outlets through the outer pipe. Preferably, the central structure is comprising a vortex breaker, preferably in the form of guiding baffles or vanes inside the outer pipe of the central structure.

[0018] In a further preferable embodiment, the central structure is integrated into a plant for aquaculture according to the description and illustrations of patent application NO 20240598, filed June 7, 2024, herein incorporated by reference.

[0019] The invention provides an outlet for use or integration into a floating plant for closed aquaculture of fish or a plant for closed aquaculture of fish on land, the outlet comprising an outlet opening through which live fish can be unloaded from the plant. The outlet is distinguished in that it further comprises: a hatch, a mechanism operatively arranged to the hatch, for arranging the hatch in a closed position with the hatch covering the outlet opening or an open position with the hatch not covering the outlet opening, an outlet conduit extending between the outlet opening in an end of the outlet conduit facing a fish farming tank of the plant for aquaculture and an opposite end of the outlet conduit ending in a wellboat or other facility feasible for loading live fish, wherein the plant is in an unloading mode, wherein live fish is or can be unloaded from the plant and the hatch is in the open position, wherein the hatch comprises openings of size and distribution allowing feces and waste food, but not live fish, to pass through the openings of the hatch as entrained with an outlet opening flow of water from the fish farming tank, wherein the plant is in a fish farming mode, wherein the hatch is in the closed position covering the outlet opening, locking out live fish from passing through the outlet opening.

[0020] Preferably, the outlet conduit comprises a flow direction controller, in the form of a valve, a baffle or other feasible structure for directing the outlet opening flow in the conduit either to a wellboat or other facility feasible for loading live fish, when unloading live fish from the plant, or directing the outlet opening flow in the conduit to a separation facility for separating out any waste food, feces and any further more or less solid material from the outlet opening flow, when operating the plant in a fish farming modus. For example, the outlet comprises two or more pipes / tubes / channels, with a guiding baffle directing the flow either to a live fish load station or wellboat or tank or similar or directing the flow to a facility for collecting feces, surplus food and any further solid material, upstream optional further separation / cleaning steps for separating / cleaning out solved pollution.

[0021] Preferably, the outlet is arranged with the hatch arranged at the lowermost part or parts of a fish tank for aquaculture, preferably with one side or end thereof in direct contact with a floor, directly facing or abutting the floor. Most preferably, the outlet opening is arranged in the lower end of a central structure coaxial to a central vertical axis of the tank, with the opening facing radially out from the central vertical axis.

[0022] Preferably, the opening is integrated in a central structure of the fish farming tank, often termed a cigar, coaxial to a central vertical axis of the fish farming tank, with the outlet opening facing radially outwards from the central vertical axis, wherein an outlet chamber inside the hatch comprises a fish launch chute, in the form of a volume wherein any change in flow direction or cross-section shape or -size is gradual, with transition or curvature large enough to ensure a careful treatment of the fish, avoiding or reducing friction-contact between fish and structure and collisions between fish, for not stressing or hurting live fish being brough / pumped through the outlet. Preferably, said transition or curvature is with radius > 0,4 m, > 1 ,25 m or > 2,5 m. The result is healthier fish, of higher quality, compared to other outlet concepts and other unloading concepts. Preferably, the hatch is single curved or flat or a combination thereof.

[0023] Preferably, the hatch comprises openings of diameter or side lengths in a range of 0,4 to 3 cm, or 0,5-2, 5 cm, or 1-2 cm. The hatch can also be termed a grating or a two-dimension grating, a grid or a mesh, if the structure provides functionality as intended. The hatch can be a plate with the openings as prescribed distributed evenly over the area for flow. The hatch preferably has openings evenly distributed all over the area to cover the outlet opening. The hatch preferably comprises an edge or side without openings, preferably where the mechanism for opening and closing is connected. Preferably, the edge or side of the hatch to face downwards, against a floor, is with no or more narrow sides without openings than the top and sides of the hatch, in order not to block the flow therethrough near the floor.

[0024] For many embodiments of plants of the invention and uses of the opening of the invention, the outlet opening flow rate with the hatch closed results in that in substance all surplus food and feces of more or less solid nature are included in the flow through the outlet opening, but said flow is only a minor flow part of the total flow rate of all flow through the plant during fish farming. Thereby, in substance all surplus food and feces is included in a separate minor flow, far smaller than the total flow rate through the plant and thereby easier to direct to a facility for separation / filtration / cleaning, for example on a dedicated unit on a deck level or below, in a larger system or plant for fish farming. A major part of the total flow rate, 2 / 3 or more thereof, up to at least 9 / 10, can thereby be cleaned far less with respect to separation, filtration and any further steps. The equipment, processing and investments required are all significantly reduced, typically by 1 / 3 or more, up to 9 / 10, compared to a typical plant without any outlets of the invention.

[0025] In a preferable embodiment, the outlet comprises a hatch displaceable between a closed position and an open position, operatively coupled to a cylinder or motor or other operatively similar mechanism for opening or closing the hatch, with movement in a length or width direction in the plane of the hatch. In a further preferable embodiment, the outlet comprises a hatch displaceable between a closed position and an open position, operatively coupled to a cylinder or motor or other operatively similar mechanism for opening or closing the hatch, adapted for rotation about a pivoting axis for opening or closing the hatch. In a further preferable embodiment, the outlet comprises one or more injection heads or nozzles for oxygen, arranged for distributing oxygen over the full area of the outlet opening and / or an outlet chamber volume of the outlet. In a further preferable embodiment, the outlet comprises one or more water nozzles for jetting water into the water flowing through the opening and / or an outlet chamber volume of the outlet and / or a volume around but near the outlet opening. The jetted water preferably is cleaned and preoxygenated, for improved fish health. In a further preferable embodiment, the outlet comprises one or more cameras for monitoring, controlling and documenting the operations.

[0026] One or more outlets of the invention can also be arranged in a floor structure, preferably in a recessed part of the floor structure and / or in a sidewall part of a plant for fish farming.

[0027] The invention also provides a floating plant for closed aquaculture of fish, comprising a tank for aquaculture, a water inlet and a water outlet. Preferably, the plant is according to the description and illustrations of patent application NO 20240598, filed June 7, 2024, herein incorporated by reference.

[0028] More specifically, the invention also provides a plant for aquaculture, as floating in a body of water, comprising a tank for aquaculture, the tank comprises one side part and one bottom part, which parts are watertight and are made of concrete, the side part of the tank extends upwards parallel to and around a central vertical axis of the tank, wherein the tank has a circular, elliptical, polygonal or similar cross section shape, the plant further comprises one or more water inlets, one or more pumps for pumping in water, an outlet system for water, an outlet system for faeces and any surplus food, an outlet system where any dead fish can be taken out, and operatively connected or integrated sterilization and / or oxygenation equipment as required. The plant is distinguished in that it further comprises: a number of outer cells extending parallel to the vertical axis, wherein the outer cells extend from a bottom elevation of the tank up to a top elevation of the tank, wherein the outer cells are integrated with the tank, on the outside of the tank, wherein the tank and the outer cells is one single structure, wherein the outer cells have a bottom part in the lower end, at the bottom elevation of the tank and the outer cells, wherein the outer cells are made of concrete, wherein the outer cells are arranged around the periphery outside the tank as groups of cells, with distance along said periphery between the groups of cells; wherein each group of cells comprises two, three or four cells, or a single cell; wherein the integrated tank and outer cells have identical cross section shape, preferably over the full vertical height from the integrated tank bottom part and the outer cell bottom, at the bottom elevation of the tank and outer cells, up to a top level, wherein the outer cells are closed at a top elevation, wherein the plant comprises or is operatively coupled to a ballast pump system for emptying or filling the tank and any number of the outer cells with ballast water, enabling lifting the plant, i.e. the tank and the integrated outer cells, to an upper position, feasible for cleaning / transit / inspection / maintenance, wherein the draught is minimized, by emptying the outer cells and the tank; and immersing the plant at least down to an operating mode position, in which position aquaculture is to take place within the tank, by filling the tank to an operation level whilst emptying the outer cells, wherein the plant comprises three, four or five or six groups of cells arranged evenly apart around the periphery of the tank on the outside if measured from a vertical centerline of each group around the periphery of the tank, comprising 6 to 12 or 18 cells, arranged as groups of one, two or three cells around the periphery of the tank.

[0029] In some preferable embodiments, the tank and outer cells can be installed in a multi array system comprising multiple plants, preferably with each plant similar in shape and dimensions, alternatively as two, three or more tanks inside multiple groups of outer cells. For all embodiments, the number and volume of outer cells are sufficient to provide buoyancy and hydrodynamic stability to allow at least one, more preferably at least two or three, of the outer cells to be damaged and losing their buoyancy function as empty for ballast water, whilst keeping the plant floating and stable, preferably by having a ratio of the total aggregated inner cross section area of the outer cells to the inner cross section area of the tank or tanks in the range 0,15 - 0,75.

[0030] The invention also provides a plant for closed aquaculture of fish, comprising a tank for aquaculture, a water inlet and a water outlet, distinguished in the plant comprises a central structure of the invention according to any of claim 1-6 and / or an outlet of the invention as described herein..

[0031] The floating plant preferably is comprising an outlet with an outlet opening through which live fish can be unloaded from the plant, the outlet further comprises: a hatch, a mechanism operatively arranged to the hatch, for arranging the hatch in a closed position with the hatch covering the outlet opening or an open position with the hatch not covering the outlet opening, an outlet conduit extending between the outlet opening in an end of the outlet conduit facing a fish farming tank of the plant for aquaculture and an opposite end of the outlet conduit ending in a wellboat or other facility feasible for loading live fish, wherein the plant is in an unloading mode, wherein live fish is or can be unloaded from the plant and the hatch is in the open position, wherein the hatch comprises openings of size and distribution allowing feces and waste food, but not live fish, to pass through the openings of the hatch as entrained with an outlet opening flow of water from the fish farming tank, wherein the plant is in a fish farming mode, wherein the hatch is in the closed position covering the outlet opening, locking out live fish from passing through the outlet opening.

[0032] The floating plant preferably is comprising a central structure (often termed a cigar) of a fish farming tank or for arranging into a fish farming tank, wherein the central structure is arranged coaxial to a central vertical axis of the fish farming tank, wherein the central structure further comprises a double coaxial pipe structure wherein an outer pipe thereof is closed towards a bottom of the tank and extends from a tank bottom elevation up to an elevation above a fish farming operation water level, wherein the outer pipe comprises openings for flow of water evenly distributed around and along the outer pipe from a distance above the tank bottom level up to a fish farming operation level of the fish tank, and wherein an inner pipe thereof is closed towards a bottom of the tank and extends from a tank bottom elevation up to within a control range of the fish farming operation water level, wherein the inner pipe has closed wall without openings for flow, wherein the water flowing through the openings of the outer pipe flows from a volume between the outer pipe and the inner pipe out over an upper end of the inner pipe, down the inner pipe and through a flow outlet through the bottom of the tank, further comprising a pipe section, often termed a sleeve, adjustably positioned over and to the top elevation of the inner pipe, for adjusting an effective height or elevation of the inner pipe upper end and thereby adjusting freeboard and effective water volume in the fish farming tank and an outlet flow rate therefrom out through the inner pipe of the central structure without having or operating valves or other control mechanisms inside the central structure or below or further downstream.

[0033] The invention also provides a method for unloading live fish from a plant for aquaculture, wherein the plant is located on land or is floating in the sea, characterized by the step: to open an outlet opening for unloading live fish when a constriction structure is moved from a high elevation in or above a water volume for fish farming in the tank down to an elevation at or just above the outlet opening, whilst a conduit for unloading live fish is extending from the outlet opening to a wellboat or other location feasible for loading the live fish. Preferably, the plant is a floating plant according to the present invention, preferably comprising an outlet according to the present invention.

[0034] The invention also provides a constriction structure for unloading live fish from a plant for aquaculture, wherein the plant is on land or is floating in the sea, comprising a tight or rigid net or grating, arranged inside an outer ring or ring-like structure, and outside an optional inner ring-like structure for plant with a central structure / cigar, wherein the outer ring or ring-like structure, and preferably also the inner ring-like structure if present, comprise wheels and / or whiskers for closely following and / or rolling on the inner surface of a fish farming tank being unloaded for live fish by moving the constriction structure from an upper elevation down to an elevation at or just above an outlet opening for unloading live fish. Fish health is a very serious issue in the aquaculture industry and particular in the salmonid farming industry. The constriction structure of the invention, used as prescribed in a plant of the invention or in other plant but with outlet for unloading fish in or at the bottom of the fish tank, enabling full tank water volume whilst unloading live fish, appear to result in far less stress over much shorter time, relative to unloading over the top of the tank or by emptying the tank volume for water and fish simultaneously, and / or involving other hydrodynamic control steps such as tilting the tank for placing the outlet at the lowermost position in the tank. The result is maintaining superior fish health beyond unloading of the live fish. Also, combining the method with several outlets for unloading fish appear to be extra beneficial since once stressing of the fish is detected, or to avoid stressing the fish, two, three, four or more outlets for unloading fish can be used for unloading simultaneously.

[0035] A preferable plant of the invention comprises a tank for aquaculture, the tank comprises one side part and one bottom part, which parts are watertight and are made of concrete, the side part of the tank extends upwards parallel to and around a central vertical axis of the tank, wherein the tank has a circular, elliptical, polygonal or similar cross section shape, the plant further comprises one or more water inlets, one or more pumps for pumping in water, an outlet system for water, an outlet system for feces and any surplus food, an outlet system where any dead fish can be taken out, and operatively connected or integrated sterilization and / or oxygenation equipment as required. The plant is distinguished in that it further comprises: a number of outer cells extending parallel to the vertical axis, wherein the outer cells extend from a bottom elevation of the tank up to a top elevation of the tank, wherein the outer cells are integrated with the tank, on the outside of the tank, wherein the tank and the outer cells is one single structure, wherein the outer cells have a bottom part in the lower end, at the bottom elevation of the tank and the outer cells, wherein the outer cells are made of concrete, wherein the outer cells are arranged around the periphery outside the tank as groups of cells, with distance along said periphery between the groups of cells; wherein each group of cells comprises two, three or four cells, or a single cell; wherein the integrated tank and outer cells have identical cross section shape, preferably over the full vertical height from the integrated tank bottom part and the outer cell bottom, at the bottom elevation of the tank and outer cells, up to a top level, wherein the outer cells are closed at a top elevation, wherein the plant comprises or is operatively coupled to a ballast pump system for emptying or filling the tank and any number of the outer cells with ballast water, enabling lifting the plant, i.e. the tank and the integrated outer cells, to an upper position, feasible for cleaning / transit / inspection / maintenance, wherein the draught is minimized, by emptying the outer cells and the tank; and immersing the plant at least down to an operating mode position, in which position aquaculture is to take place within the tank, by filling the tank to an operation level wherein the plant comprises an outlet of the invention, the outlet comprising an outlet opening through which live fish can be unloaded from the plant, the outlet further comprises: a mechanism operatively arranged to the hatch, for arranging the hatch in a closed position with the hatch covering the outlet opening or an open position with the hatch not covering the outlet opening, an outlet conduit extending between the outlet opening in an end of the outlet conduit facing a fish farming tank of the plant for aquaculture and an opposite end of the outlet conduit ending in a wellboat or other facility feasible for loading live fish, wherein the plant is in an unloading mode, wherein live fish is or can be unloaded from the plant and the hatch is in the open position, wherein the hatch comprises openings of size and distribution allowing feces and waste food, but not live fish, to pass through the openings of the hatch as entrained with an outlet opening flow of water from the fish farming tank, wherein the plant is in a fish farming mode, wherein the hatch is in the closed position covering the outlet opening, locking out live fish from passing through the outlet opening.

[0036] Preferably, for the plant is according to the teaching of application NO 20240598, with or without the outlet of the invention and / or the central structure of the invention, the tank has circular cross section shape, and the outer cells have circular cross section shape, providing maximum structural strength for minimum material consumption and minimum work. Preferably, the circular walls are joined as circular walls tangential to each other, meaning the circular walls go into each other to become one common wall at the point or section of full joining or overlapping, between the outer cells and the tank and between neighbor outer cells of the same group of outer cells, avoiding double walls. Arranging the outer cells as groups of outer cells, with distance between the groups of outer cells along the outer periphery of the tank, provides increased hydrodynamic stability and buoyancy at reduced material consumption, labor and cost, compared to arranging outer cells around the full periphery distance of the tank or a double tank structure with vertical bulkheads. The structure of the plant of the invention according to application NO 20240598, preferably integrating the outlet and / or the central structure of the present invention, enables a significant cost reduction compared to other concepts of similar nature for closed or semi-closed aquaculture. The tank with integrated outer cell structure is cylindrical, with equal and parallel heights, with a common floor level shared between the tank and the outer cells, with a single cylindrical continuous structure above, which enable continuous, effective concrete slip forming from the floor level up to the top level, cutting the time and cost for fabrication significantly. With an expected lifetime above 100 years for the concrete structure, combined with a modest investment cost, the economy of the concept is favorable. Savings of at least 30% of the initial investment can be expected, compared to non-cylindrical and / or uneven dimensions in vertical direction, which is very surprising. If calculating the cost over many years, the result is promising. With state-of-the-art slip casting, the main structure, which could be about 30-50 m in diameter and up to 30 m high, can be built within a couple of weeks, estimates indicate. The plant is preferably without any openings or embedded structures within the vertical walls, reducing cost further. Deviations from vertical direction, and identical shape, is within 5%, 4%, 3%, 2%, 1 % or 0,5% or 0,25% or less, which ensures smooth fabrication by eliminating or reducing having to adjust slip formwork dimensions, arrangements or support structure during fabrication.

[0037] The central body (fish tank) does not provide net positive buoyancy while operating (fishfarming), as it is connected to the sea. Thus, only the outer cells provide positive buoyancy and stability in these conditions. However, for cleaning / transport conditions, the central tank enables the emersion of the unit as it provides the extra buoyancy required to raise the structure partly out of the water. The inner walls and / or floor / bottom of the central body (fish tank) preferably is finished with a coating and / or liner that provide simultaneously a smooth surface to avoid fish damage when entering in contact with the surface, that also allow cleaning of the surface with high pressure means regularly without damaging the surface, that avoid the marine growth without leaching copper that endanger the health of the fish, and improves transport of any surplus food, feces and any dead fish to respective outlets, and enable reduced angular inclination of the tank bottom. The plant preferably comprises a grating, or a deck, on top of the cells and around the periphery of the tank. Preferably, the grating or deck is octagonal with four sides of equal length, or near octagonal, with four and four sides of equal length, as seen from above, or the grating is hexagonal as seen from above, enabling close packing or arranging of a plurality of plants of the invention to a larger structure for aquaculture.

[0038] In many preferable embodiments the plant of the invention according to application NO 20240598, preferably integrating the outlet and / or the central structure of the present invention, is comprising outer cells with circular cross section, ideal for withstanding pressure. In other preferable embodiments, the plant comprises outer cells with circular cross section, but partly cut away vertically by the inner tank, and / or curved outer cells with common walls in between and to the tank outer wall. Elimination of surplus volumes, and double walls, can thereby be provided. An example of a preferable embodiment is that the cells are cut vertically by the wall of the tank, wherein the cell wall meets the tank wall at an angle in the range 90-30° as measured on the outside, and wherein walls between cells are shared walls, meeting the tank wall at around 90° angle. The plant design promotes natural compression by taking advantage of the outer pressure from hydrostatic loads, leading to an efficient concrete design, minimizing concrete and armoring consumption while maximizing building efficiency. Preferably, the plant comprises a structure coaxial to and along a vertical centerline of the tank, the structure is termed a cigar 17 and is not made of concrete. Preferably, the cigar 17 is a central structure as herein defined and claimed separately. The plant preferably comprises a number of groups of cells arranged evenly, such as 30°, 45°, 60°, 90° or 120° apart around the periphery of the tank on the inside if measured from a vertical centerline of each group around the periphery of the tank, comprising 6 to 12 or 16 or 18 cells, arranged as groups of two or three or four cells around the periphery of the tank. In some embodiments, the plant comprises six single, double or triple cells arranged 60° or 120° apart around the periphery of the tank if measured from a vertical centerline of each single, double or triple cell around the periphery of the tank. The arrangement of groups or single cells apart around the periphery, reduce the building work while enabling a functionality as described, with empty tank and empty cells providing a transport, cleaning and / or service mode position, and filled tank and empty cells providing an operating mode or position, preferably designed for still allowing safety with the plant floating and stable even if one or two cells are destroyed, for example in an unintended collision.

[0039] The plant of the invention preferably comprises an inclined bottom in the tank, inclined inner side downwards from periphery to center, at an angle of about 5° ±3°, ±2° or ±1 °, wherein the vertical thickness of the tank bottom at center typically is > 1 m, with increasing thickness towards the periphery due to the inclination, preferably with horizontal, flat outer bottom side facing downward, i.e. facing the building site ground and oriented downwards during operation. The inclination facilitates transport of live fish, feces, any surplus food and any dead fish to respective outlets. The inner walls and bottom of the tank preferably is coated with a low friction material protecting the fish from skin injuries (later evolving to winter wounds) and enabling easier cleaning and disinfection of the tank. An inert silicone-based coating is feasible as said coating, since it is free from any harmful substances.

[0040] The invention also provides a method of building a plant for aquaculture according to the present invention, that is a plant according to application NO 20240598, with or without an outlet and / or a central structure of the present invention. The method is distinguished by the steps: to build the floor of the tank and outer cells, as one single structure, with any pipes or openings embedded in the floor, on a yard or building site ground, such as in a dry dock, by casting the floor using concrete or grouting and armoring, embedding any piping as required, to arrange slip forms where vertical walls are to be built, and slip casting the vertical walls of the tank and the outer cells as one single structure, integrated with the floor, up to a top level for concrete in the plant, without any openings or embedded structures within the vertical walls, to complete outfitting of the plant.

[0041] Preferably, the slip casting is undertaken as a single, continuous slip casting operation. Otherwise, the amount of rebar and post-tensioning steel will increase the cost of the structure and slow down the manufacturing process. Besides it would also add “cold joints” which make it difficult to ensure watertightness. The result is a more reliable structure to lower cost. Preferably, the method further comprising flooding the building site, i.e. a dry dock or similar, for floating and transporting the plant to an operation location.

[0042] The method of the invention preferably includes building and integrating one or more outlets of the invention into the plant and building and / or integrating one or more central structures of the invention into the plant, completing the outfitting of the plant.

[0043] The invention also provides use of the plant of the invention, for aquaculture of fish.

[0044] In many preferable embodiments, the central structure comprises one, two, three or more outlets of the invention at the lower end of the outer pipe of the central structure of the invention, in addition to possible further outlets of the invention in a drainage sump recessed in the bottom of the fish tank, and optional further outlets of the invention, providing a sum of outlet opening flows which enable separating out and transporting in substance all surplus food and feces through the outlets while in substance all of the water of the main flow through the outer pipe openings of the central structure of the invention is in substance without any surplus food or feces, reducing or eliminating further processing like filtering and cleaning thereof.

[0045] Preferably, the central structure and / or the plant of the invention comprises an extended or extendable outlet pipe, extendable by telescopic structure and / or by winches and / or as preinstalled and to be coupled in or out by operating valves, for ensuring that any contamination in the outlet flow is not recirculated into the inlet flow. Preferably, also an inlet pipe inlet elevation is adjustable or electable, down to at least 25-30 m depth, for ensuring that and any lice or poisonous algae in the inlet water can be avoided, and for adapting the water temperature to optimal level for the fish under any season.

[0046] Drawings

[0047] Figures 1-5 illustrate a plant of the invention, with the basic structure as defined in application NO 20240598, of which

[0048] Figure 1 illustrates the plant in oblique view,

[0049] Figure 2 illustrates the plant in longitudinal section,

[0050] Figures 3a and 3b illustrate the plant of the invention as seen from above, without an upper grating or other structure.

[0051] Figure 4 illustrates some typical dimensions and arrangements of piping in a plant of the invention.

[0052] Figures 5a and 5b illustrate cleaning / transit mode and operating mode of a plant of the invention.

[0053] Figure 5c illustrates some details of some parts of a typical sea water circulation system of a plant of the invention.

[0054] Figures 6 and 7 illustrate an outlet of the invention.

[0055] Figures 8 - 10 illustrate a central structure, a cigar of the invention.

[0056] Figure 11 illustrates a central structure, a cigar, of the invention with adjustable outlet pipe.

[0057] Detailed description

[0058] Reference is first made to Figures 1-5, wherein identical or similar equipment items have the same numerical reference. Notice that in Figures 1-5 neither the outlet of the invention nor the central structure of the invention is illustrated in any detail, or not at all, since detailed design, was not invented yet when filing application NO 20240598. For illustrations of the outlet of the invention reference is made to Figures 6 and 7. For the central structure, also termed cigar, reference is made to Figures 8- 11.

[0059] The invention provides a plant 1 for aquaculture, comprising a tank 2 for aquaculture for floating in a body of water 3, the tank comprises one side part 4 and one bottom part 5, which parts are watertight, the tank has a circular cross section shape and is made of concrete, the plant further comprising one or more water inlets 6, one or more pumps 7 for pumping in water, an outlet 8 for water, an outlet for live fish, an outlet 9 for feces and any surplus food, and an outlet 10 where any dead fish can be taken out, and operatively connected or integrated sterilization 12 and / or oxygenation equipment 13 as required. The plant is distinguished in that it further comprises: a number of outer cells 11 , made of concrete, with a full or partly round cross section shape, comprising a closed lower end 14, wherein the outer cells are integrated with the tank as one single structure, to the outside of the tank, and wherein the cells preferably extend from the bottom part level of the tank up to a top level of the tank, extending preferably over the full vertical height of the tank; wherein the outer cells are arranged around the periphery outside the tank as groups of two, three or four cells, or single cells, with distance 15 along said periphery between the groups of cells or single cells; wherein the cells are operatively coupled to a ballast pump 16 for emptying or filling the fish tank or any number of the cells with ballast water, enabling lifting the plant, i.e. the tank and the integrated cells, to a cleaning / transport position wherein the draught is minimized, and immersing the plant at least down to an operating position, in which position aquaculture is to take place within the tank, wherein the tank and the cells are cylindrical in shape, preferably with identical cross section shape and dimension, preferably over the full vertical height, from the integrated tank bottom and cell bottoms up to a top level at the upper elevation thereof, and preferably, the number and volume of cells are sufficient to allow at least one, more preferably at least two, or more, of the cells to be damaged and losing their buoyancy function as empty for ballast water, whilst keeping the plant floating and stable.

[0060] The cells and the tank are integrated structures, meaning that they together are one single structure, behaving as one single structure. The relatively large weight of the plant, and the intended location in relatively confined waters, results in very low dynamic load, favorable for fish health. The term cylindrical means having the same cross section shape and size along a length axis, here the vertical axis, as if the structure were extruded along the vertical direction. Cylindrical is not necessarily spherical. The effect is that slip forming becomes far more effective, resulting in faster and more cost-effective building process. The cylindrical tank and cells as integrated preferably have no openings or feedthroughs in the vertical walls, reducing the cost further.

[0061] The shape of the tank and the outer cells is intentionally designed to produce a permanent compressive stress on the walls thanks to the hydrostatic pressure. For this reason, the spaces enclosed by the tank and each pair of adjacent outer cells (if existing) must also be connected to sea, ensuring a water level matching the draught of the unit. This contributes to the generalized compression of the walls, improving their structural capacity, corrosion resistance and watertightness, and therefore reducing the required amount of reinforcement steel. In addition, when casting the whole wall ensemble as a monolithic piece of concrete, the natural compression attained at the walls allows to disregard the need of horizontal post-tensioning elements between walls, which would increase the cost and slow down the manufacturing process.

[0062] As seen in Figure 5a, the plant is at lifted or high elevation in the cleaning / transit mode, enabling effective transport from a dry dock or similar building facility, and effective transport to the operating location, which reduce cost.

[0063] The cigar 17 is only briefly illustrated in Figures 1-5 but is illustrated in more detail in Figure 8-11.

[0064] Figures 6 and 7 illustrate an embodiment of an outlet 18 of the present invention. The outlet 18 is for use or integration into a floating plant for closed or semi closed aquaculture of fish, with the basic structure as defined in application NO 20240598 for many preferable embodiments, but also for any other version of floating plant for closed aquaculture or plants on land for closed aquaculture. The outlet 18 comprises an outlet opening 19 through which live fish can be unloaded from the plant. The outlet further comprises a hatch 20, a mechanism 21 operatively arranged to the hatch, for arranging the hatch in a closed position 22 with the hatch covering the outlet opening or an open position 23 with the hatch not covering the outlet opening, an outlet conduit 24 with the outlet opening 19 in an end of the outlet conduit facing a fish farming tank of the plant for aquaculture and an opposite end 25 of the outlet conduit ending in a wellboat or other facility feasible for loading live fish, in an unloading mode of the plant, when unloading live fish from the plant, with the hatch in the open position, wherein the hatch comprises openings 26 of size and distribution allowing feces and waste food to pass through the openings of the hatch as entrained with an outlet opening flow of water from the fish farming tank, in a fish farming mode of the plant, with the hatch is in the closed position 22 covering the outlet opening, locking out live fish from passing through the outlet opening.

[0065] In the illustrated embodiment the outlet further comprises a flow direction controller 27 in the form of a valve, a baffle or other feasible structure. The outlet comprises one or more injection heads or nozzles 28 for oxygen, arranged for distributing oxygen over the full area of the outlet opening and / or an outlet chamber volume of the outlet. The outlet may comprise one or more water nozzles 29, and cameras 30. In many embodiments, the outlet 18 is arranged with the outlet opening 19 integrated in a central structure 17 of the fish farming tank, often termed a cigar, coaxial to a central vertical axis of the fish farming tank.

[0066] Further reference is made to Figures 8 - 10 illustrating a preferred embodiment of a central structure 17, also termed a cigar, of the invention. The illustrated central structure 17 (often termed a cigar) of a fish farming tank or for arranging into a fish farming tank, is preferably arranged coaxial to a central vertical axis of the fish farming tank. The central structure 17 comprises a double coaxial pipe structure wherein an outer pipe 31 thereof is closed towards a bottom 5 of the tank and extends from a tank bottom elevation up to an elevation above a fish farming operation water level, wherein the outer pipe 31 comprises openings 32 for flow of water evenly distributed around and along the outer pipe from a distance above the tank bottom level up to a fish farming operation level of the fish tank, and wherein an inner pipe 33 thereof is closed towards the bottom of the tank and extends from a tank bottom elevation up to within a control range 34 of the fish farming operation water level, wherein the inner pipe has closed wall without openings for flow, wherein the water flowing through the openings of the outer pipe flows from a volume between the outer pipe and the inner pipe out over an upper end 35 of the inner pipe, down the inner pipe and through a flow outlet 36 through the bottom of the tank.

[0067] Preferably the outer pipe comprises ventilation openings at the top of the pipe to allow air to be sucked into the outer pipe thus preventing pressure and / or vacuum to be created inside the cigar due to the water flowing through the outer pipe and over the top and out of the inner pipe through the bottom of the tank.

[0068] In many preferable embodiments, the central structure is further comprising an outer pipe section 37, also termed a sleeve or an adjustment pipe, adjustably positioned over and to the top elevation of the inner pipe, for adjusting an effective height of the inner pipe and thereby adjusting the water level inside the tank to match the draught (freeboard) of the tank hence making it possible to safeguard a proper freeboard during more intense weather conditions. In smooth waters the adjustment pipe can be raised to a higher position to enable filling of more water inside the tank, thus optimizing environmental conditions for the fish inside the tank.

[0069] The adjustable pipe (sleeve) is arranged with devices to secure a lowermost and uppermost position always within the secure limits of the scantlings and the stability of the tank. Thereby, safe freeboard and control thereof, as well as control of flow rate out through the inner pipe can be provided without having valves or other control mechanisms inside the central structure or below or further downstream. The adjustment distance covers the control range 34, which is an elevation range.

[0070] In some preferable embodiments, the central structure 17 is arranged inside a plant for aquaculture according to the description and illustrations of patent application NO 20240598, filed June 7, 2024, herein incorporated by reference, wherein a number of outer cells are extending parallel to the vertical axis, wherein the outer cells extending from a bottom elevation of the tank up to a top elevation of the tank, ensure buoyancy, elevation and stability of the plant, and thereby also feasible draught and safety for enabling pipe section / sleeve 37 to “detai l”-control the flow rate out through the inner pipe of the central structure, and draught of the plant, without further active control means.

[0071] In many preferable embodiments the central structure is made of steel or a combination of steel and polymer, preferably with steel for lower parts, including outlets of the invention, and polyethylene PE of potable water quality, and / or GRP, for elevation above the outlets of the invention. The main water outlet is through the inner pipe, whilst the outlet opening flows integrated in the central structure, are arranged outside the inner pipe. All outlet opening flows as combined, including possible further outlet flows, are as combined smaller relative to the main outlet flow, typically up to around 10 % of the flow rate of the main flow. Only the outlet opening flows are requiring relatively extensive filtering and cleaning, whilst the main outlet flow require no or moderate filtering and / or cleaning. Gravity and the more stagnant water at the lower part of the fish tank ensures that solid or heavier contamination accumulate in the more stagnant water and are flowing out from the fish tank through the outlet openings. The central structure preferably comprises vortex breakers 38 in the form of guiding baffles or similar structure inside the outer pipe of the central structure, reducing forces, enabling leaner structures.

[0072] Figure 11 illustrates a central structure of the invention comprising an extendable outlet pipe 39, the lower end and thus the effective outlet elevation being controllable by weight 40 and winch 41 , wherein a telescopic functionality can be controlled. The outlet elevation and position can be controlled to avoid any recirculation of water from the outlet to the inlet.

Claims

Claims1.A central structure (often termed a cigar) of a fish farming tank or for arranging into a fish farming tank, wherein the central structure is arranged coaxial to a central vertical axis of the fish farming tank, characterized in that the central structure comprises a double coaxial pipe structure wherein an outer pipe thereof is closed towards a bottom of the tank and extends from a tank bottom elevation up to an elevation above a fish farming operation water level, wherein the outer pipe comprises openings for flow of water evenly distributed around and along the outer pipe from a distance above the tank bottom level up to a fish farming operation level of the fish tank, and wherein an inner pipe thereof is closed towards a bottom of the tank and extends from a tank bottom elevation up to within a control range of the fish farming operation water level, wherein the inner pipe has closed wall without openings for flow, wherein the water flowing through the openings of the outer pipe flows from a volume between the outer pipe and the inner pipe out over an upper end of the inner pipe, down the inner pipe and through a flow outlet through the bottom of the tank.2.The central structure of claim 1 , further comprising a pipe section, often termed a sleeve, adjustably positioned over and to the top elevation of the inner pipe, for adjusting an effective height or elevation of the inner pipe upper end and thereby adjusting freeboard and effective water volume in the fish farming tank and an outlet flow rate therefrom out through the inner pipe of the central structure without having or operating valves or other control mechanisms inside the central structure or below or further downstream.3.The central structure of claim 1 or 2, comprising an integrated outlet with an outlet opening through which live fish can be unloaded from the plant, wherein the outlet further comprises: a hatch,a mechanism operatively arranged to the hatch, for arranging the hatch in a closed position with the hatch covering the outlet opening or an open position with the hatch not covering the outlet opening, an outlet conduit extending between the outlet opening in an end of the outlet conduit facing a fish farming tank of the plant for aquaculture and an opposite end of the outlet conduit ending in a wellboat or other facility feasible for loading live fish, wherein the plant is in an unloading mode, wherein live fish is or can be unloaded from the plant and the hatch is in the open position, wherein the hatch comprises openings of size and distribution allowing feces and waste food, but not live fish, to pass through the openings of the hatch as entrained with an outlet opening flow of water from the fish farming tank, wherein the plant is in a fish farming, wherein the hatch is in the closed position covering the outlet opening, locking out live fish from passing through the outlet opening.4.The central structure of any of claims 1-3, comprising an extendable outlet pipe, enabling adjustment of the outlet elevation of a lower end of the extendable outlet pipe, preferably in the form of an integrated telescope-pipe configuration of one or more telescopic pipe parts, with a weighted lower end thereof and a winch, a motor or similar device operatively arranged to the telescope-pipe structure.5.The central structure of any of claim 1-4, wherein the central structure is made of steel or a combination of steel and / or polymer and / or GRP; preferably with steel for lower parts, including any integrated outlets through the outer pipe, and PE (polyethylene) of potable water quality and / or GRP (Glass Fiber Reinforced Polymer), for elevation above any integrated outlets through the outer pipe.6.The central structure of any of claim 1-5, comprising a vortex breaker, preferably in the form of guiding baffles or vanes inside the outer pipe of the central structure.

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