The present invention relates in general to modular structures at least partly submerged in water, and in particular to tank structures for storage or processing of media in fluid form or carried in a fluid.
In many contexts there is a need to keep a large volume separated from the surroundings with the help of an enclosing barrier, where the primary criterion is to prevent physical exchange of material. Secondary criteria can relate to e.g. thermal insulation.
Examples of the above are holding tanks for liquids, bioreactors and enclosed fish farms. In many cases the delimited volume can be very large. Furthermore, in addition to tanks and retaining vessels of various types, large scale facilities that contain or process liquid-borne materials shall generally require physical infrastructure on a correspondingly large scale.
Traditionally, these challenges have been met by creating heavy structures with high inherent strength, employing traditional materials such as masonry, reinforced concrete and high strength steel. Examples of this are large bioreactors, protected by elaborate security constructions.
Considering first state of the art in constructing large land-based structures, a basic strategy has been to add incrementally a large number of building blocks that are linked together and immobilized by mortar or cement. Drawbacks of such “wet” methods are well known: They require skilled labour, they are time consuming and labour intensive and create irreversible structures that cannot be modified or dismantled without demolition. Over time, improvements have included generic strategies for guiding and supporting the building blocks by “dry” means, e.g. by shaping the mutually contacting surfaces of the building blocks with protrusions and cavities that fit into each other, assisting the building process and stabilizing the structure. Further improvements include shaping the building blocks with grooves or channels that communicate from one block to the next when they are assembled, being adapted to receive elements that hold the structure together, e.g. in the form of reinforcing rods that may be stabilized in castable concrete or in the form of metal bars or tie cables that are secured by nuts, clips or other means. Examples of solutions where modular building blocks are adapted to employ techniques referred above include:
U.S. Pat. No. 3,618,279, “Building block” by T. F. Sease teaches a building block having male and female portions adapted to hold a series of blocks in interconnecting relation, with or without the use of mortar. Truncated pyramidal projections on top and matching cavities at the bottom provide mating connections when the blocks are assembled on top of each other. The blocks may be held together by “wet” or “dry” means.
UK Patent Application GB 2,394,730 A, “Mortarless brick and locking bolt building system” by J. H. O. Morrison teaches combined interlocking bricks that have recesses on their lower surface that can receive protruding studs on their upper surfaces. The studs are hollow and communicate between successive courses, and segmentally connectable bolts with integral threaded sockets are passed through any number of the aperture studs to secure successive courses.
U.S. Pat. No. 5,685,119, “Wall construction system” by B. Zschoppe teaches a wall construction system based on shaped bricks for dry attachment to each other. Each brick has a shaped projection on the top bearing surface and a complimentarily shaped recess on the bottom that engage when bricks are assembled in a wall. The bricks are formed with chases extending perpendicular to the top and bottom bearing surfaces creating vertical channels through the assembled wall.
US Patent Application US 2002/0148187 A1, “Construction blocks and structures therefrom” by D. L. Walters teaches blocks for construction of walls and other structures, where the blocks have ridges and longitudinal grooves that fit together when the blocks are assembled on top of each other, providing horizontal and vertical channels that are adapted to receive reinforcing rods and castable concrete.
The building blocks described in the above referred patents and patent applications are generally limited to applications involving straight, right angled and planar structures such as walls in static, unalterable configurations. A solution with somewhat higher degree of constructive freedom is taught by W. A. Rice:
U.S. Pat. No. 2,826,906, “Wall of building blocks” by W. A. Rice teaches a single tier wall of substantially identical elongated blocks having planar top and bottom faces. When the blocks are laid in superposed courses, segmental-spherical protrusions on top of the blocks fitting into corresponding sockets at the bottom of the blocks and help to keep them in alignment. Circular bores in each block create connecting channels between blocks in different courses and can be used for threading of reinforcing rods. The protrusions and sockets are positioned and shaped to allow rotational motion about a vertical axis, which combined with rounded corners on the blocks allow them to be assembled at an angle with each other to create corners and curved walls. The protrusions and sockets are too shallow and rounded to provide cohesion of the wall without mortar, and there are no provisions for introduction of strengthening elements beyond vertical reinforcing rods. Thus, the invention shall in practice be limited to static land-based constructions
Prior art as exemplified above presents substantial problems when attempting to implement it on large scale marine and water-immersed structures: Whereas land-based structures are static and immutable, large structures in water shall generally be exposed to wave- and tidal-induced forces and motion. This may damage or cause disintegration of stiff and unyielding structures, particularly when acting on large assemblies of building blocks across long distances encountered with large structures. In situ construction in water is generally not practicable with “wet” methods, and typical prior art building materials are generally heavy, making deployment of prefabricated large structures or modules difficult.
Attempting to avoid the problems adhering to using prior art modular components, materials and building techniques to create large sea-borne constructions, proposals have been made for building enclosed fish farms offshore using the same principles as seagoing ships and offshore drilling platforms, i.e. rigid structures in steel able to withstand large waves and ocean swells, extending across tens to hundreds of meters. A considerable number of such solutions have been proposed but have so far proved too expensive for commercial viability. An example of a large scale heavy structure based on offshore technologies is described in International Publication Number WO 2015/099540 A1: “A semisubmersible, cylindrical net cage, closable bulkheads for a net cage and a bottom for the net cage that can be elevated”, by T. K. Hammernes and A. K. Hammernes. The latter structure is budgeted to cost in excess of 500 million NOK.
Thus, the solutions according to state of the art carry with them a number of undesirable consequences related to cost of construction, limited design flexibility, limited resilience to mechanical stresses and strains, large carbon footprint, and high cost of ultimate removal and clean-up.
It is thus a main purpose of the present invention to provide a system for establishing of large and scalable physical infrastructure in a marine environment, encompassing buoyant structures disposed above and below water.
It is further a main purpose of the present invention to provide a method for the construction of such infrastructure in a simple and inexpensive manner.
It is further a main purpose of the present invention to provide a system for establishing of partly or completely submerged tanks capable of storing or processing of large volumes of substance at low cost.
It is further a main purpose of the present invention to provide a system for establishing of floating platforms supporting production and other facilities.
It is still further a main purpose of the invention to provide structures that respond elastically when subjected to bending forces.
The present invention achieves the purposes defined above by a synergetic combination of strategies which can be summarized as follows:
Submersion in water provides several enabling effects: First, buoyancy in the water reduces the effective weight of the structures and thus the required strength for the structures to support themselves. This effect becomes especially important when the structural materials are themselves lightweight, cf. below. Second, the weight of liquid-borne materials which exerts large pressure strains on land-based tanks and reactors is effectively balanced out by the hydrostatic pressure acting on the tank walls when they are submerged in water. Third, the cushioning and blocking effect of the surrounding masses of water provides a security barrier against explosions, blow-outs and leaks. Finally, in many coastal areas, lakes and rivers there is convenient access to water-borne transport, and stretches of water may out-compete areas of real estate on land for the siting of industrial facilities.
Extensive use of polymeric materials in tanks and other types of physical infrastructure: Contrary to the case of steel and concrete, objects made from polymers have near neutral buoyancy in water, and very large structures can be built and controlled in water by judicious design and incorporation of ballasting and buoyancy elements. Bulk polymeric materials lack the high mechanical strengths that can be encountered in steel and other traditional construction materials. However, they provide extraordinary constructive freedom, allowing for intricate shapes, high precision and a wide range of mechanical and chemical characteristics. This in turn makes possible a close integration of strengthening elements penetrating, supporting and surrounding the structures in question, for example by designing a network of channels for guiding strengthening elements. The latter may be rigid (e.g.: beams, rods and pillars) or flexible (e.g.: cables, straps or tubes) and may consist of any suitable material, and may be added in any required number, location and direction. As a consequence, structures can be given virtually any degree of strength, flexibility and resilience.
Creating structures by the assembly of a plurality of modular structural elements, where each element links mechanically to other structural elements. Modular structural elements can be mass produced from polymers to high precision and can be defined with complex shapes to match their intended function in a structure. This includes internal voids and channels, as well as external contours and topographic features that determine the external appearance of the structure in question, the inter-element connectivity and the mechanical compliance of the structure.
Employing modular structural elements that are typically much smaller than the structure in question and have linear dimensions of 30 cm or less. The consequences of this include some obvious ones, such as easy handling of elements during the building of structures, typically adding one element at a time either by hand or robot, and being able to build structure with feature details down to 30 cm. Less transparently, the choice of size is expected to have great impact on the ability to employ the present invention in remote locations and without incurring high capital cost in transport and manufacturing equipment: A preferred method of manufacturing modular structural elements is injection moulding. The associated infrastructure cost (presses, energy consumption, etc) depend strongly on the size of the elements, and keeping dimensions down opens up opportunities for locally produced elements, in certain cases on site where structures are being built, thus reducing transport logistics and ultimately the cost of the structures in question.
Briefly summarized, the present invention achieves the purposes defined above by a modular structure, a macro structure, and a method for construction of a structure as defined in the claims, where the modular structure and the macro structure comprise structure elements as defined in the claims, and mainly according to the strategies outlined above.
A first aspect of the invention is a modular structure for being at least partly submerged in a body of water, where the modular structure comprises a plurality of structure elements, where each structure element comprises polymers. Each structure element comprises one or more protruding and receiving parts, wherein the protruding parts of a structure element are arranged for mating connection with the receiving parts on another structure element, the direction of mating motion defining a longitudinal direction of the structure element. Further, the modular structure comprises strengthening elements for providing structural integrity to the modular structure, where the strengthening elements are enveloping and/or penetrating at least parts of at least two structure elements of the modular structure. The structure elements are adapted to form longitudinal channels inside the protruding and receiving parts, where the channels communicate across two or more structure elements that are in a mated connection. The structure elements have apertures adapted to form channels through the structure elements in at least one direction transverse to the longitudinal direction. Further, the structure elements and strengthening elements are adapted to provide flexibility to the modular structure while maintaining its structural integrity by at least one of the following i) comprising material with inherent elasticity, and ii) being formed to allow relative movement between at least two structure elements.
The structure elements can have linear dimensions not exceeding 0.3 m, and each structure element can comprise at least 80% by volume of polymers. The structure elements and strengthening elements can be adapted to provide flexibility to the modular structure while maintaining its structural integrity when the structure is subjected to bending up to 10 degrees pr. linear meter.
The modular structure can form at least one closed structure, where a number of structure elements that overlap partially or completely in the longitudinal direction can be connected in a network that closes upon itself around a volume.
The closed structure can be a tank structure delineating a volume for the storage or processing of media in fluid form or materials carried in a fluid, where the closed structure can be a cylinder.
A longitudinal dimension of the closed structure can be smaller than the largest dimension in a plane transversal to the longitudinal direction, such that the closed structure forms a circular or polygonal disk or annulus.
The protruding parts and the receiving parts of the structure elements can each be provided with at least one set of two apertures positioned so that the apertures in the protruding part align with the respective apertures in a receiving part in longitudinally attached adjacent structure elements and thus forming transversal channels perpendicular to the longitudinal direction.
The modular structure can comprise strengthening elements of which at least one is inserted in at least one of the longitudinal and the transversal channels.
The strengthening elements comprise at least one of the following: i) an elongate strengthening element, and ii) a surface element for enveloping at least parts of the structure, and said elongated strengthening element can comprise at least one of the following: a strap, a cable, a container, a tube, and a rod, and said surface element can comprise at least one of the following: a foil, a tarp, a flexible plate, and a band. Further, said elongated strengthening element can form a closed loop attaching at least two structure elements and/or modular structures, and can be arranged according to one or more of the following alternatives: i) in the longitudinal channel and ii) along an outside of each of the at least two structure elements.
The strengthening element can comprise a container or a tube adapted to be filled with one ore more of the following materials: sand, gravel, earth and pellets, gas filled bodies, expanded polystyrene and polymeric-based pellets.
The strengthening element can act as a buoyancy controlling device as one of the following: i) a flotation element by the container being filled with a material giving the strengthening element a positive buoyancy, and ii) a ballast element by the container being filled with a material giving the strengthening element a negative buoyancy.
The modular structure can comprise a strengthening element for attaching at least a first and a second structure element wherein the strengthening element is arranged to pass through both holes in each of the adjacent structure elements.
Further, the strengthening element can comprise at least one of the following: pin, bolt, and clasp. The strengthening can be arranged with one or more through holes for introduction of a strengthening element.
The protruding part and the receiving part of the structure elements can be provided with polygonal mating surfaces so that the mating connection is made at predetermined angles between the structure element and an adjacent structure element.
The modular structure can comprise at least one of a top floor and a bottom floor respectively arranged in a transversal plane perpendicular to the longitudinal direction, where the at least one of the top and bottom floors can comprise a number of disks or annuli. The at least one of the top and bottom floors can be in contact with an inside of the closed structure at an end in the longitudinal direction.
A further aspect of the invention is a macro structure comprising at least a first and a second modular structure, wherein the first and second modular structures are attached to each other.
The at least first and second modular structures can contribute to form a perimeter wall of a closed macro structure delineating a macro volume. The perimeter wall can comprise an inner and/or an outer wall sandwiching the closed modular structures of the perimeter wall.
The at least two of the closed modular structures can be attached by an elongated strengthening element, where the elongated strengthening element is looped through a longitudinal channel or around a part of one of the at least two attached modular structures, and through a longitudinal channel or around a part of another of the at least two attached modular structures.
At least two contiguous closed structures of a macro structure can be coupled by at least one surface element.
An additional aspect of the invention is a method for construction of a modular structure, characterized by the following steps:
The method for construction of a modular structure can comprises can further comprise the following steps:
a. establishing a first part of the modular structure;
b. assembling of structure elements where the assembling occurs with the modular structure floating partially submerged in the body of water; and
c. sinking of the modular structure such that the assembly occurs at approximately a constant height over the body of water.
The assembling step of the method can occur by sequential application of the structure elements, layer by layer.
b,
1
c,
1
d, and 1e disclose a detailed section of a tank structure.
a, b, c discloses construction of a tank structure in situ.
a, b, c disclose a curved structure element and a top view and a side view of a cylindrical structure comprising a plurality of such structure elements.
a, b, c disclose structures comprising different types of structure elements.
a, b, c disclose structures comprising rounded structure elements; freely curving wall, branching walls and helix-shaped wall, respectively.
a, b, c disclose alternative embodiments of structure elements.
The invention shall be described with reference to the figures showing several examples of embodiments.
The invention is based upon the building of structures over all size scales based upon assembling and mechanical consolidating of modular elements, discussed as structure elements and strengthening elements.
A significant insight related to the preferred embodiment of the present invention is that it is considerably easier to establish structures for the storage of large volumes of liquid in tanks submerged in water than up in the open air. This is because the internal hydrostatic pressure from the liquid in a submerged tank is balanced by water pressure from the outside. Thereby, the tank's walls and bottom mainly have a limiting function between the liquid inside and outside the tank, which places considerably less demand on the tank's mechanical strength. Furthermore, deliberate use of buoyancy forces in the water reduces the demands for mechanical strength even further. By building the tank's different parts out of materials with approximately neutral buoyancy in water, for example plastic or hollow elements, there will be a greatly reduced need for strengthening elements that can bear the tank's own weight.
The construction of large structures under water has the potential to be very costly and demanding. In a preferred embodiment of the present invention, this problem is solved by constructing the structures of special building elements that are assembled and locked in a dry zone over the water line in a continuous process where the structure slowly sinks deeper into the water as construction progresses.
The net result has dramatic effects on the volume of the structure that can be constructed within given cost limits. It also opens the way for structures constructed of light, cheap materials based upon recycled plastics. It remains to secure the structures against dynamic forces, for example: waves and underwater currents, which require special methods against stretching and bending stresses, cf. below.
The internal channels can contribute to the tank's structural strength by employing them as guides or containment volumes for strengthening elements or materials in the form of cables, pipes, rods, beams, fill or casting material. Sand-filled stockings of strong textiles are relevant in this context.
Interconnection between structure elements via topographic details can occur in several ways. Direct methods include, among others, friction and male/female type click-connections of supporting elements, hooks, bayonet couplings, etc. It can also occur through indirect methods comprising the use of helping components, for example: locking pins, rods, and columns through hole and channels in contiguous or nearby elements. Indirect methods can also comprise supporting elements, as well as clips, clamps, cables, and bands. On the segment in
By treading lashing bands through the channels and stretching the bands, the tank is given elasticity and improved resistance against external physical effects. The structure maintains tight connections between the individual structure elements over time, even with mechanical wear, matter flow, etc.
Additional structural strength, and possibly other functions, can be achieved with the help of bands that stretch and tighten over the tank's outer surface and/or by enveloping parts of either the whole tank's outer and/or inner surfaces with foil, tarp, or bendable plates that are anchored in the tank's walls and possibly bottom and top. Relevant fastening techniques include, but are not limited to, the following: glue, Velcro bands, buttons, pins, and screws. A preferred fastening method is to use a mechanical fastening system where the structure elements are textured on the surface that forms the tank's outer and/or inner side. The texturing can, for example, be in the form of spikes, columns, pimples, hooks, or pipes, shaped such that it binds with reciprocal texturing on the foil, tarp, or the bendable plate to be fastened. Several layers of foil, tarp, or bendable plates can be laid on top of each other, such that they are textured on both sides and possibly added in several layers and stretching directions.
With big tanks, where the radius of curvature far exceeds the size of the structure elements, the linear structure elements can form segments with linear facets in curved macro-surfaces that form in other ways than by the shape of the individual structure elements. Tensile and bending forces can occur between anchoring points inside or outside the tank's walls, from stiffening and tension elements that follow the channels through the structure in strategic directions or by connecting via elements and struts to anchoring points on other parts of the structure or outside this.
Examples of structures that can be stabilized by tensile forces are domes and arches with radial stress and cylinders with tangential and axial stresses.
It will be clear that tank structures based on structure elements and strengthening elements that are assembled and connected according to the present invention may be built and utilized on dry land.
At the same time, it will be obvious that the building of large, floating, and light weight tanks such as discussed in
The result of this building method is that the work can always be performed in a dry zone that is easily accessible at moderate height above the waterline. As the construction progresses (
The tank can be equipped with a floor (ref (14) on
This construction technique, where a tank without a bottom is built downwards in a water mass until it reaches the seabed, occurs with a minimum amount of disturbance of the relevant water volume. This gives unique possibilities to survey the local environment and investigate plant and animal life at different depths in the water column.
In many situations it is especially important that the tank is sealed, such that there is no material transport between the tank's volume and the surrounding water mass. This can be achieved in many ways:
It can also be relevant to control the atmosphere in the volume over the fluid surface inside the tank, for example when there are poisonous gasses present in the tank or when the contents must be protected from contamination from outside. When plants and animals are cultivated in the tank, it may be desirable to collect CO2 that is produced. This can be achieved with a number of possible techniques that will be known for one skilled in the art.
The structure elements according to the present invention incorporate the essential enabling features for the assembling of structures where tanks, walls and connecting elements form large scale consolidated complexes with advanced functionalities and unlimited dimensional scalability. This shall now be demonstrated by some preferred embodiments with reference to the structure elements shown in
The structure element in
The structure elements in
a,b,c show examples of how the basic structure elements shown in
A central feature of the present invention is that structure elements can “dry lock” to each other, i.e. they can be reversibly assembled into macroscopic structures with considerable structural integrity without the need to employ glue or cement. This has obvious advantages in many instances (rapid prototyping, test assemblies, etc) and may be followed up by subsequent mechanical consolidating of the macrostructures.
In addition to friction coupling between protruding and receiving parts in the structure elements, the elements may have topographic features as exemplified in
Structure elements according to the present invention are preferably made from polymers by means of a thermal shaping technique such as injection molding. Polymers can be given a wide range of mechanical properties by selection of polymer type and loading with reinforcing fibers. A central property in the present context is the degree of dimensional precision and the complexity of structural details that can be achieved. This enables highly controlled friction and displacement tolerance properties between mating and contacting structure elements, which contribute to predictable compliance and resilience of assembled structures when subjected to external forces.
When high mechanical strength is required, structure elements can be locked in the vertical and horizontal directions by various means as described previously. One solution is shown in
Structures made from structure elements with sharp corners as shown in
i) horizontal and vertical rigid strengthening elements in the form of tubes, rods and pins, and/or:
ii) in-filled bags, tubes and containers in the vertical channels, and/or:
iii) a crosslinking horizontal, vertical and diagonal network of flexible strips, cables and straps.
Together, these features shall enable such macrostructures to absorb and tolerate ocean currents and wave motion while maintaining the structural integrity of critical substructures.
In-filled bags, tubes and containers in the vertical channels may serve multiple functions where they in addition to strength and integrity contribute various functionalities to the structure: In
The basic architecture of the present invention permits virtually limitless scaling and cross-linking in 3 dimensions to achieve the strength and functionality required in a given situation. As an example, the wall construction in
A particularly useful type of planar structures is achieved by coupling together a plurality of low aspect ratio cylinders (annuli). An example of an annulus is shown in
Point or line connections in the form of straps or pins may be undesirable in situations where movement in the structure may cause wear and tear at contact points between different parts of a macrostructure. In such cases, surface-covering sheets may be wrapped tightly around each cylinder to provide strength. In addition to having high stretch strength, the sheet may be backed by an adhesive and incorporate a shock absorbing layer. The same type of sheet can be used on bundled tanks and cylinders in a coupled macrostructure. Added strength can be achieved ad libitum by wrapping sheets in multiple layers.
A plurality of annuli can be coupled side by side form a planar macrostructure, where the pattern of annuli is determined by the couplings between them, e.g. random, square or close-packed hexagonal (HCP) where each annulus is surrounded by six other annuli. Maximum strength against in-plane deformation or compression is generally achieved in a HCP configuration, which also provides the highest in-plane packing density of annuli. The macrostructure may be given positive, neutral or negative buoyancy in water through the choice of construction materials, by in-filling of high- or low-density materials in the vertical channels and/or by positioning buoyancy or ballast elements in the volume inside the annuli.
In addition to providing a flexible and scalable basis for integration into a variety of macrostructures, floating and submerged floors formed by coupled units such as annuli can form functional macrostructures in their own right.
A generic perimeter wall for macrostructures, e.g. fish tanks, is shown in
Number | Date | Country | Kind |
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20161803 | Nov 2016 | NO | national |
Filing Document | Filing Date | Country | Kind |
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PCT/NO2017/050291 | 11/13/2017 | WO | 00 |