Technical Field

The invention relates to floating structures, in particular floating structures made up of frames supported by buoyant members. More specifically, the invention relates to floating structures which provide a platform for an installation, such as an array of PV panels, a desalination plant, or an energy storage unit, or for some other type of use. The floating structures may be used both inshore, e.g. on rivers or lakes, or offshore.

Background

In many parts of the world, land is increasingly scarce, as cities expand and an increasing population requires more land to be reserved for agriculture. Therefore, there is a trend that installations which take up a large surface area, like e.g. solar farms, are increasingly built on large scale floating structures or artificial islands. These floating structures can be positioned in the vicinity of cities where the energy harvested from the solar farm will be used. Many of the world’s largest cities are situated near a body of water, like a sea or lake.

As illustrated by the documents discussed below, conventional floating structures usually comprise a relatively large rigid frame, which is either supported by separate buoyant members or which is made up of hollow elements providing inherent buoyancy. With some exceptions, the frame of a conventional floating structure is usually rectangular. Conventional floating structures have a relatively high wave resistance, leading to relatively high loads on their frames, which must therefore be strong and comparatively heavy. Moreover, although rectangular frames can accommodate movement as a result of frontal waves, they are not suitable for accommodating torsional wave movements. Floating structures made up from a number of rectangular frames require relatively complex couplings and a relatively wide spacing to accommodate torsional wave movements.

Prior art document WO 2017/118998 Al discloses a rectangular floating solar platform which includes a unified floating structure that is formed of a horizontal mesh of one or more horizontal support members connected to each other in a matrix pattern, and one or more vertical support members fixedly mounted on the horizontal mesh. A horizontal planar modular deck is fixedly mounted on the unified floating structure and supports one or more arrays of solar panels. This floating structure is too rigid to follow the waves, resulting in high wave loads on the structure and/or large air gap requirements between the wave surface and the array of solar panels.

Prior art document WO 2017/023536 Al discloses a floating solar array made of a closed loop of flexible high density polyethylene pipes with elbows, T fittings and couplings forming a pontoon. An anti-lift membrane fills with water and mitigates the wind forces. The array can have a stabilizing skirt going downwardly from the border of the array, especially when it is used offshore in the sea. This document shows not only rectangular pontoons, but also hexagonal and octagonal pontoons.

Prior art document KR 101997077 Bl discloses a floating water solar power generation module which comprises: a closed circular or elliptical support frame provided at the outside of a structure; a support net having a rope provided in a lattice shape inside the support frame; an array of solar panels on the support net; and a main floating body coupled to one side of the support frame.

In view of the above, there is a need for improved floating structure.

Summary

In accordance with the invention, a floating structure is provided which comprises a plurality of interconnected frames and a plurality of buoyant members supporting the structure, and wherein at least some of the frames are substantially triangular in planform.

By interconnecting a plurality of frames, which may be relatively small, rather than using a single frame which is relatively large, the floating structure may be built relatively easily and swiftly by assembling the frames. Moreover, such a plurality of smaller frames is easier to stock, transport and handle than a single large frame. For instance, if the edges of the frames are designed to be no longer than 12 m, they may be transported in standard 40 feet containers.

And by using triangular frames, rather than the commonly used rectangular frame, loads on the structure can be absorbed and/or transferred in a more efficient manner. Triangular frames are particularly well suited for absorbing and/or transferring shear loads within the plane of the triangle and have a relatively high strength to weight ratio.

And finally, by using separate buoyant members, rather than providing the frame with buoyancy, a clear functional division is established, which allows the frame to be optimized for its load-bearing function. This arrangement also allows the frame to be kept clear of the water, thus reducing wave resistance of the floating structure and keeping the upper surface of the floating structure dry and free of water loads. Moreover, this arrangement leads to less movement of the frame in comparison to a partially submerged frame or pontoon, which is beneficial when the floating structure is used to support an installation.

Although the floating structure might include some frames having a different planform, e.g. a row of rectangular frames at an edge or in a centre of the structure, in one embodiment all frames are substantially triangular in planform. In this way the floating structure as a whole is optimally suited for accommodating in-plane shear loads.

In a further embodiment, adjacent triangular frames are movably connected. By providing a movable connection between adjacent frames, they may accommodate movement due to torsional waves more efficiently, so that loads on the floating structure are reduced. By “movably connected” it is meant that a frame has one or more of six possible degrees of freedom with respect to an adjacent frame.

In yet another embodiment, adjacent triangular frames are pivotably connected. A pivotable connection allows the frames to more or less conform to the waves on the body of water on which the structure floats, thus reducing the loads on the structure even further.

In order to maximize the useful surface area of the floating structure, in one embodiment the triangular frames may have substantially the same shape. In that way they can be mounted relatively closely together.

A uniform floating structure may be achieved in an embodiment wherein the triangular frames have substantially the same dimensions.

In an alternative embodiment of the floating structure, at least one of the triangular frames may have dimensions which are a multiple of the dimensions of another one of triangular frames. In that way the floating structure might be made up of a combination of larger and smaller triangles.

In one embodiment, each triangular frame may have a base, an apex and two sides connecting opposite ends of the base with the apex, and adjacent triangular frames may be connected along their respective sides such that the base of a first frame is closest to the apex of a second frame and the base of the second frame is closest to the apex of the first frame. In this way a row of alternating triangles may be formed, such that the series of bases at opposite sides may form substantially continuous edges.

Additionally or alternatively, in one embodiment each triangular frame may have a base, an apex and two sides connecting opposite ends of the base with the apex, and adjacent triangular frames may be connected along their respective bases. In this way two interconnected triangular frames may form a diamond.

In one embodiment, the triangular frames may comprise right-angles triangles. Such triangular frames may easily be combined to form a rectangular floating structure.

In another embodiment, the triangular frames may comprise isosceles triangles. In this way a uniform floating structure may be formed.

Uniformity of the floating structure may be further increased by an embodiment in which the triangular frames comprise equilateral triangles.

In order to obtain an efficient load-bearing structure of each frame, in one embodiment the isosceles triangle may have an apex angle between about 20-120°, in particular an apex angle of 60°.

In one embodiment of the floating structure, at least some of the triangular frames may have at least one corner which is chamfered or rounded. For practical purposes, e.g. in order to provide sufficient strength or to avoid dangerously sharp angles, small deviations from a purely triangular shape may be accepted without loss of the fundamental advantages of that shape.

In one embodiment of the floating structure, at least some of the triangular frames may have a substantially open load-bearing structure, the three sides of the triangle comprising beams connected at or near their ends. By concentrating the loads acting on the frame in beams forming the edges of the triangle, a well-defined and efficient load distribution may be achieved.

In order to allow an installation to be mounted on the floating structure, in one embodiment the beams forming the sides of the triangle may support an internal grid or a platform.

In one embodiment, each triangular frame is supported by at least one buoyant member. In this way the frames are self-supporting and do not rely on being connected to other frames for their buoyancy.

In one embodiment the at least one buoyant member may be connected to the respective triangular frame by at least one post. In this way a distance is maintained between the floating structure and the surface of the body of water in which it floats.

In order to ensure stability of the individual frames, in one embodiment of the floating structure each triangular frame may be supported by at least three buoyant members.

In a further embodiment, each buoyant member may be connected to a respective triangular frame near a corner of the frame. In this way stability of the floating structure is even further increased.

In one embodiment, when adjacent triangular frames are connected along their respective sides or bases, each buoyant member may be connected to a respective triangular frame at a position along a side or base which is offset with respect to a position of a buoyant member along a side or base of an adjacent triangular frame to which the first side or base is connected. In this way there is no risk of buoyant members of adjacent triangular frames colliding during movement of the frames on waves of a body of water on which the structure floats.

In one embodiment, the floating structure may further comprise anchoring means for maintaining the floating structure substantially at a fixed location in a body of water.

In a further embodiment, the floating structure may further comprise an installation supported by the floating structure.

In yet another embodiment, when the beams forming the sides of the triangle support an internal grid or a platform, the installation may be arranged on the internal grid or the platform of a respective triangular frame.

In one embodiment, the installation may comprise a plurality of PV panels. Alternatively, the installation could comprise e.g. a desalination plant, or an energy storage unit, e.g. an array of batteries. Other possible uses for the floating structure are the generation of wind energy through one or more turbines, or the generation of wave energy. In addition to one or more floating structures dedicated to energy generation, a further floating structure could support energy intensive activities, like e.g. a hydrogen production unit, a hydrogen-to-fuel conversion plant, or a data center. The floating structure could also be used for urbanization, i.e. housing and/or recreation, for agriculture or for aquaculture. And finally, the floating structure could be used as an offshore mooring or satellite port, where ships could load or offload cargo or supplies, in particular fluidic cargo that can be brought ashore through pipelines.

In yet another embodiment, the number of buoyant members and their volume, as well as a length of the at least one post may be selected as a function of the weight of a respective frame and its installation, such that the frame is supported at a distance above a still waterline of a body of water in which the floating structure is used. In this way the frame can be kept free of waves on the body of water on which the structure is floating.

The invention further provides a triangular frame which is evidently intended for use in a floating structure as described above.

Brief description of drawings

The invention will now be elucidated by way of a number of exemplary embodiments, with reference being made to the annexed drawings, in which:

Fig. 1 is a perspective top view of a first embodiment of a floating structure made up of four interconnected triangular frames in accordance with the invention;

Fig. 2 is a perspective top view of a second embodiment of the floating structure in accordance with the invention, made up of triangular frames having a different planform than those of the first embodiment;

Fig. 3 is a view corresponding with that of Fig. 1 , but showing each triangular frame of the floating structure supporting an array of PV panels;

Fig. 4 is a perspective bottom view of the floating structure supporting PV panels as shown in Fig. 3;

Fig. 5 is a rear view of the first embodiment of the floating structure according to arrow V in Fig. 1 ;

Fig. 6 is a side view of the first embodiment of the floating structure supporting PV panels according to arrow VI in Fig. 3, showing an exemplary still waterline around the buoyant members;

Fig. 7 is a top view of the first embodiment of the floating structure;

Fig. 8 is a bottom view of the first embodiment of the floating structure;

Fig. 9 is a top view of the second embodiment of the floating structure; Fig. 10 is a top view of a triangular frame in accordance with a third embodiment of the invention, illustrating both different buoyant members and a different positioning of the buoyant members;

Fig. 11 is a view corresponding with that of Fig. 3, but showing a single frame in accordance with the third embodiment;

Fig. 12 is a view corresponding with that of Fig. 11, but without the array of PV panels;

Fig. 13 is a perspective view of an example of a pivot connection between adjacent triangular frames in which an edge of one of the frames has been removed for improved clarity;

Fig. 14 is a general diagram of a triangle illustrating various angles and dimensions; and Fig. 15A-C are schematic planforms of various types of triangular frames having the arrangement of the buoyant members of the third embodiment.

Detailed description

A floating structure 1 (Fig. 1) comprises a plurality of triangular frames 2, in this embodiment four frames 2A-2D, which are mutually connected along their adjacent edges. Each frame 2 is supported by one or more - in this embodiment three - buoyant members 3. In the illustrated embodiment each buoyant member 3 is connected to the triangular frame 2 by a single post 6. The three buoyant members 3 are shown to be connected to the respective frame 2 near a corner 7 of the frame 2, i.e. near one of the three angles of the triangle forming the frame 2.

Adjacent triangular frames 2 are connected such as to be movable with respect to one another, so that the floating structure 1 has some degree of flexibility. In the illustrated embodiment, adjacent triangular frames 2 are pivotably connected. To that end the frames 2 may be provided with pivotable connecting elements 19, in this case two connecting elements 19 near the corners 7. These connecting elements 19 may comprise a single lug 8 on one of the triangular frames 2 and a pair of lugs 9 on the other frame 2, wherein the lugs 8, 9 may have aligned holes for receiving a pin 10 (Fig. 12). The pivotable connections between the frames 2 lead to the formation of an articulated floating structure 1 , in which the triangular frames 2 can follow movement of waves when the structure 1 is floating on a body of water.

In the illustrated embodiment the four triangular frames 2A-2D all have the same shape and dimensions. In fact, the frames 2 are shown to be formed by equilateral triangles of which the base 11 (Fig. 14) has the same length as each of the two sides 12 which connect the base 11 to the apex 13. In such an equilateral triangle the three angles are identical so that each corner can be considered the apex 13.

In another embodiment (Fig. 2) the frames 2 are formed by isosceles triangles, in which the base 11 (Fig. 13) has a different length than the sides 12 and the apex 13 has an angle a that is different from the angles of the two lower vertices 21. In this embodiment the apex 13 has an angle of 90°, so that the base 11 is some 40 percent longer than the sides 12, thus forming a blunt triangle.

In both embodiments the three outer triangular frames 2A, 2C and 2D are arranged mutually parallel and have their apexes 13 all at the same side, while the central triangular frame 2B is arranged in opposite direction. The left and right triangular frames 2A, 2C are connected to the central triangular frame 2C along their respective sides 12, while the foremost triangular frame 2D is connected to the central triangular frame 2C along their respective bases 11.

In this arrangement, the four triangular frames 2A-2D together form a floating structure 1 which is triangular in itself, and has the same triangular shape in planform as the constituting triangular frames 2. The edges of the triangular floating structure 1 are twice as long as those of the individual triangular frames 2. The floating structure 1 could comprise more or less than four triangular frames 2. The floating structure 1 could further comprise triangular frames having different dimensions or different shapes. For instance, the structure 1 could include a central triangular frame having the same dimensions as a combination of four triangular frames as shown in the drawings, which could be surrounded by combinations of four smaller triangular frames of the type shown in the drawings. For practical purposes, the length of the edges of the triangular frames 2 can be selected with a view to ease of transportation, and could be a multiple of 6 m (20 feet), which is a standard container size.

Alternatively, the arrangement of Fig. 1 could be extended e.g. by placing two triangular frames having the same orientation as central frame 2C on both sides of the foremost triangular frame 2D, thus leading to an “hourglass” shape, and then adding two isosceles triangles having an apex of 120° at the sides to form a rectangular or square floating structure 1.

A square floating structure 1 could also be formed by mirroring the arrangement of Fig. 2.

In addition to the triangular frames 2, the floating structure 1 could also include frames having a different planform. For instance, one or more square frames could be arranged between the triangular frames 2C and 2D to form an arrow-shaped floating structure. Additionally or alternatively, relatively narrow rectangular frames could be arranged at the outside of the floating structure, either for increasing buoyancy or to support e.g. walkways for maintenance staff.

In the illustrated embodiments, each triangular frame 2 has an open load-bearing structure comprising three beams 14, which are connected at their ends. In order to allow an installation to be mounted on the floating structure 1, an internal grid 15 may be arranged between the loadbearing beams 14. In the illustrated embodiments the internal grid 15 includes four longitudinal girders 16 and a transverse girder 17. As illustrated here, the internal grid 14 not only serves to support an installation, but also forms a connection between the buoyant members 3 and the loadbearing frame 2, since the posts 6 are shown to be connected to the outer longitudinal girders 16 and to the transverse girder 17 (Fig. 4). Although the beams 14 and girders 16, 17 are shown here as having closed rectangular cross-sectional profiles, it is conceivable for these members to have different cross-sectional profiles. The beams and/or the girders could have a round or oval cross-section, or could have another polygonal cross-section, e.g. triangular. Alternatively, the beams and/or the girders could have an open cross-section, and could e.g. be C-shaped, H-shaped, I-shaped or L-shaped. It is also conceivable for the beams and/or the girders to be formed by trusses or by a spaceframe.

In the illustrated embodiment the floating structure 1 supports a solar power generating installation. The installation comprises a plurality of arrays of PV panels (Fig. 3). In this embodiment each triangular frame 2 carries a substantially triangular array 4 of PV panels. The PV panels are shown to be arranged in rows 5, the length of which decreases from the base 11 towards the apex 13 of the triangle. In this embodiment, adjacent rows 5 are arranged in the shape of a rooftop, and walkways 18 are shown to be arranged between each pair of rows 5.

Although in the illustrated embodiment the entire surface area of each triangular frame 2 is covered by the array 4 of PV panels, it is also conceivable to reserve a part of the surface area for other parts of the installation, like e.g. control electronics, a transformer or batteries for storage. The floating structure 1 could be made up of triangular frames 2 carrying PV panels and one or more triangular frames 2 carrying other parts of the installation.

Instead of a solar power generating installation, the floating structure 1 could carry a different type of installation, e.g. a desalination plant, a hydrogen production plant or some other installation that requires a large amount of space but involves only limited or no human intervention. In such cases, the triangular frames 2 could be provided with a platform, rather than an internal grid.

In the illustrated embodiment the buoyant members 3 have the shape of an oblate ellipsoid, i.e. a body of revolution about a vertical axis on the basis of an ellipse having a major axis which is horizontal and a minor axis which is vertical. Such an ellipsoid-shaped buoyant member, which is described in detail in the applicant’s co-pending application entitled: “Floating structure having ellipsoid buoyant members”, has been found to have a very low wave drag, so that loads on each triangular frame 2 will be relatively low and its structure may be light. However, in situations where wave drag is less of an issue, more basic shapes of buoyant members could be considered, as illustrated by the rectangular buoyant members 23 shown in Figs. 10-12.

Loads on the triangular frames 2 are further reduced by keeping the frames 2 free of the water during normal use. Moreover, in this way the installation carried by the floating structure, in this case the array 4 of PV panels, is also protected from adverse effects due to the impact of waves. As shown in Fig. 6, the buoyant members 3 are almost fully submerged below the still waterline WL, while the frame 2 is supported at a height h above the still waterline. This is achieved by careful selection of the number of buoyant members 3 and their volume, as well as the length of the posts 6 as a function of the weight of each respective triangular frame 2 and the array 4 of PV panels which it supports. The height h above the waterline WL is selected in accordance with the intended use. For inland waters, like lakes or even rivers, where wave heights will be limited, a free height of 1-2 m may be sufficient, whereas for offshore applications much higher structures, possibly with the frames 2 up to 25 m above the still waterline WL may be needed.

The buoyant members 3 are shown to be fully submerged in this embodiment. However, it is also possible to give each buoyant member 3 a greater volume, so that it provides the required buoyancy even when it is only partially submerged. In that case the potential reserve buoyancy that may be generated when the buoyant member 3 is submerged to a greater extent than necessary for carrying the frame 2 may be used to increase dynamic stability of the floating structure 1. This reserve buoyancy will counter a downward movement of part of the triangular frame 2 when one side of the frame 2 is lifted by an approaching wave.

Although the frames 2 have thus far been shown to be purely triangular, small deviations from this shape can be used without departing from the inventive concept. For practical purposes the corners 7 of each triangular frame 2 may be chamfered or rounded, e.g. in order to provide sufficient strength or to avoid dangerously sharp angles. This is shown in the embodiment of Fig. 10.

This embodiment also includes an alternative arrangement of the three buoyant members 3, in which the buoyant members 3 are not arranged symmetrically with respect to a center line of the triangular frame 2, as is the case in the previous embodiments. In the embodiments of Figs. 1-9 the buoyant members 3 of adjacent triangular frames 2 are located directly opposite one another in a direction transverse to the connected edge. Therefore these buoyant members could theoretically collide in case of pivoting movement of the frames 2 due to waves. In the embodiment of Figs. 10- 12 each buoyant member 3A-C is connected to the frame 2 - through transverse girder 17 or a diagonal girder 20 - at a position along an edge which is offset with respect to a position of a buoyant member 3A-C along an edge of an adjacent triangular frame 2. If a triangular frame 2 is arranged to the right of the frame 2 shown in Fig. 10, with its apex pointing in the opposite direction, its first buoyant member 3A would not be directly opposite the first buoyant member 3A of the shown frame 2, but instead would be located in the vicinity of, but not directly opposite to the third buoyant member 3C. Similarly, if another frame 2 would be arranged to the left of the frame 2, again with its apex pointing in the opposite direction, its second buoyant member 3B would be offset from the second buoyant member 3B of the shown frame 2. The same applies if a further triangular frame would be arranged below the frame 2 of Fig. 10, again with its apex pointing in the opposite direction.

As shown in Fig. 15, this alternative positioning of the buoyant members 3 can be used in any embodiment of the triangular frame 2. Fig. 15A shows a frame 2 in the shape of an equilateral triangle, in which the angle a of the apex 13 and the angles P of the two other vertices 21 are all the same, as are the lengths of the two sides 12 and the base 11. Fig. 15B illustrates the second embodiment of the frame 2 as shown in Figs. 2 and 9, in which the buoyant members 3 are arranged offset from the apex 13 and other vertices 21 of the isosceles triangle. And finally, Fig. 15C shows another possible shape of the frame 2; a right-angle triangle having three different sides 11, 12A and 12B and three different angles a, and y, respectively. The embodiments of Figs. 15B andl5C lend themselves to being combined into a rectangular floating structure 1 fairly easily. Alternatively, a lozenge-shaped floating structure 1 could be made by connecting triangular frames as shown in Fig. 15C along their sides 11 and 12A bordering the right angle vertex 21 A.

Although not shown in the drawings, the floating structure 1 is further provided with anchoring means for maintaining the floating structure 1 substantially at a fixed location in a body of water. The anchoring means may e.g. include so-called spud poles, which are driven into the bottom of the body of water and along which the structure 1 can float up and down without changing its orientation. Alternatively, the anchoring means could include one or more anchors fixed in the bottom, to which the floating structure 1 could be connected by chains or other flexible elements, so that the structure could change its orientation, e.g. to keep the PV panels in an optimum position relative to the sun. When used on relatively smaller inland waters, the floating structure could also be anchored to the shore.

Although the invention has been illustrated by a number of exemplary embodiments, it will be apparent that many modifications could be made within the scope of the claims.

For instance, the number of buoyant members supporting a triangular frame could be more or less than three. When using less than three buoyant members, each buoyant member must be inherently stable, e.g. in the way of a float used for fishing. It is also conceivable, e.g. when one of the frames 2 has to carry a very heavy load like the weight of an electrical transformer or the forces exerted by the anchoring means, to provide that frame 2 with (a) buoyant member(s) 3 extending under the entire surface area of the triangular frame 2, more or less transforming that frame 2 into a barge.

Also the number of triangular frames 2 which together constitute the floating structure could be more or less than four. In principle there is no upper limit to the number of triangular frames 2 that can be connected together.

Any suitable material can be used in the construction of the triangular frames 2, the buoyant members 3 and the posts 6. Such materials include aluminum, steel, concrete or fiber reinforced plastics.

The scope of the invention is defined solely by the following claims.