WO2017131510A1

WO2017131510A1 - Device, system and method for growing seaweed

Info

Publication number: WO2017131510A1
Application number: PCT/NL2016/050538
Authority: WO
Inventors: Eric Henricus Laurens Antonius VAN DEN EIJNDEN; Douglas KALKWARF
Original assignee: Seatechenergy Ip B.V.
Priority date: 2016-01-26
Filing date: 2016-07-19
Publication date: 2017-08-03
Also published as: NL2016158B1

Abstract

The invention relates to a device for growing seaweed in a volume of water such as a sea. The device comprising a frame having a plurality of growing strings attached to the frame for growing seaweed thereon. It also comprises a plurality of floating bodies that are connected to the frame. The floating bodies are arranged to maintain the frame submerged at a substantially constant depth independent of a water depth. The invention also relates to a method for growing seaweed using such a device and a system for growing seaweed comprising at least two of such devices.

Description

Title: Device, system and method for growing seaweed

Description

According to a first aspect the invention relates to a device for growing seaweed in a volume of water such as a sea.

According to a second aspect the invention relates to a method of growing seaweed using a device according to the first aspect of the invention.

According to a third aspect the invention relates to a system for growing seaweed in a volume of water such as a sea using at least two devices according to the first aspect of the invention.

Methods and devices for growing seaweed are known wherein growing strings for growing seaweed thereon are attached to anchors at a sea bottom. The strings are lifted from the sea bottom by attaching buoys to the growing strings. These methods and devices function relatively well in shallow and quiet waters. However, these devices and methods can be improved to realise enhanced growing results.

It is an objective of the present invention to provide a device to realise enhanced growing results.

The objective is achieved by the device according to the present invention whereby the device comprises a frame having a plurality of growing strings attached to the frame for growing seaweed thereon, further comprising a plurality of floating bodies that are connected to the frame, wherein the plurality of floating bodies is arranged to maintain the frame submerged at a substantially constant depth independent of a water depth of the volume of water, wherein the frame of said device comprises an outer ring surrounding a growing area and a cross member extending through the growing area, wherein the cross member is connected at two positions to the outer ring. The combination of frame and growing strings is thus arranged to sink. Through submersion of the frame at a substantially constant depth independent of the water depth, thus at a variable height above the sea bottom, the device can also effectively be applied in relative deep and less quiet waters. The invention at least partly relies on the insight that more favourable growing conditions can be achieved by growing seaweed in deeper seawaters compared to the known methods. In deeper waters circulation of water between the seaweed is increased subjecting the seaweed to additional nutrition thereby creating more favourable growing conditions. Furthermore by arranging the floating bodies to maintain the strings at a relative constant depth the growing conditions are improved. Improved growing conditions are favourable for increasing the production volume per hectare of a surface area of the water volume.

The frame comprises an outer ring and a cross member to provide a relative robust layout to resist rough weather conditions and permit ease of handling for instance for moving the device towards a growing location. The cross member provides stiffness to the frame to reduce the deformation of the outer ring due to currents and weight of the growing lines. In addition, the cross member reduces sagging of the growing lines, thereby creating more uniform growing conditions across the growing area.

It is a further insight of the inventor that the growing conditions of seaweed are more favourable at specific depth ranges. Through the floating bodies the influence of tides, for example, on the growing process is eliminated or at least significantly reduced. At a specific depth range the photosynthetic conditions of the seaweed can be enhanced. In addition, at a specific depth range, the light intensity is relatively stable thereby reducing the risk of burning the seaweed. Furthermore, at a constant depth range, the variation of water temperature is relative small, thereby enhancing the growing conditions.

Preferably, the outer ring has a substantial circular shape and the cross member is configured to maintain the outer ring in the substantial circular shape. I n a practical embodiment the cross member is connected at two positions to the outer ring 180 degrees apart along the outer ring, to maintain the outer ring in a substantial circular shape. This is a very simple but effective construction which is easily scalable. It is further advantageous if an inner diameter of the outer ring is at least 10 meters, preferably at least 50 meters, and maximally about 300 meters.

The outer ring preferably comprises at least one, preferably three, tube members extending mutually parallel, spaced apart by a plurality of spacers, along the outer ring.

It is advantageous in this regard if the plurality of growing strings extend mutually parallel in the growing area. Parallel growing strings are favourable for harvesting the seaweed. Furthermore, parallel growing strings add to the strength of the frame and allows relative easy assembly of the device. In addition, parallel extending lines reduce the risk of marine wildlife getting caught in the device. It is advantageous in this regard if growing strings of the plurality of growing strings, preferably each growing string, is suspended via both ends thereof from the frame. In an embodiment, each of the growing strings may be tensioned within the growing area. Thereby the depth of the growing strings is well defined and the growing strings contribute to the stiffness of the frame, in particular the outer ring thereof.

In a very practical embodiment the device comprises a single cord forming the plurality of growing strings. A single cord is beneficial to reduce the need for manufacturing growing strings of various lengths and/or reduce waste of string material to attach the strings at various positions at the frame.

It is beneficial for the strength of the frame if the cross member is dividing the growing area in two areas of substantially equal size and/or shape.

Preferably, the floating bodies are distributed substantially evenly over the frame. Thus the frame is kept very stable at each position along the frame.

Preferably a distance between neighbouring floating bodies of the plurality of floating bodies, or at least the connection thereof at the frame, is less than two metres.

It is advantageous if the floating bodies have a substantially elongated shape in a longitudinal direction thereof, wherein the connection between a respective floating body and the frame is arranged to maintain the longitudinal direction of the floating bodies substantially upright. Elongated floating bodies are less susceptible to external influences at the water surface, in particular disturbances by wind and/or waves. The floating bodies are configured to protrude upwards from the water surface with between 20 and 80 percent of the length thereof, preferably between 30 and 70 percent.

It may furthermore be advantageous if a cross-section of the floating bodies in longitudinal direction is substantially constant. This results in a high independence to above mentioned external influences. Preferably, each of the plurality of floating bodies is formed by a hollow cylinder having closed ends. Preferably the cross-section has an oval shape to align the floating bodies with a current in the volume of water.

It is advantageous in this regard if said device comprises, for each of the plurality of floating bodies, a cable that connects that floating body at an end thereof to the frame. Preferably, the plurality of floating bodies of said device comprises at least 100 floating bodies and at most 1000 floating bodies. The influence to the device of waves, wind and current is reduced for a larger number of floating bodies.

It is beneficial if the device further comprises a propulsion means that is arranged to maintain said device in a predetermined area of the water.

In a preferred embodiment of the device the outer ring comprises at least two mutually parallel endless rings surrounding the growing area, wherein said endless rings are interconnected for stiffening of the frame.

According to a second aspect of the invention, the invention relates to a method for growing seaweed using a device according to the first aspect of the invention. The advantages of the method are analogue to the advantages of the device according to the first aspect of the invention.

In a preferred embodiment of the method according to the second aspect the frame is submerged at a depth in the range of 1 to 15 meters. It is an insight of the inventor that the growing conditions of seaweed are favourable at depth range of 1 to 15 meters.

Preferably, the method of growing seaweed comprises the steps of providing an anchor to the sea bottom and anchoring the device to anchor, wherein preferably a distance between said device and the anchor is at least 2 times larger than a distance of said device to the sea bottom so as to allow free movement of said device with respect to the sea bottom in the depth direction. By anchoring the device in such a way drifting away of the device to a remote location is prevented while allowing free movement of the device in the water. As such the anchor plays no role in regulating or influencing the depth of the device.

It may further be advantageous when using a device according the first aspect of the invention provided with a propulsion means that is arranged to maintain said device in a predetermined are of the water, if the method comprises the step of propelling said device using the propulsion means for maintaining said device in a predetermined area of the water.

According to a third aspect of the invention, the invention relates to a system for growing seaweed in a volume of water such as a sea, the system comprising at least two devices according to the first aspect of the invention wherein neighbouring devices are connected via an anchor at the sea bottom. Connecting neighbouring devices is advantageous to realise a relative high growing capacity in a volume of water. A system according to the invention is favourable for increasing the production volume per hectare of a surface area of the water volume.

The present invention will now be explained by means of a description of a preferred embodiment of a method, device and system according to the invention for growing seaweed, in which reference is made to the following schematic figures, in which:

Figure 1 is an isometric view of a device according to the present invention;

Figure 2 is an enlarged view of detail A of figure 1 ;

Figure 3 is an enlarged view of detail B of figure 1 ;

Figure 4 is a top view of part of a preferred embodiment of a system according to the present invention;

Figure 5 is an enlarged view of two devices of the system of figure

4;

Figure 6 is a side view of the two devices of figure 5.

Figure 1 shows a seaweed growing device 1 being an embodiment of a device according to the present invention. Device 1 has a frame 3 and a plurality of floating bodies 5. Each of the floating bodies 5 is connected to the frame 3 via a cable 7 forming connection means for connecting that floating body 5 to the frame 3. The frame 3 has a circular frame member in the from of an outer ring 2, which bounds a growing area 13. The frame 3 also has a cross member 4 that extends through the growing area 13 and is connected to the outer ring 2 at both ends thereof, at two respective positions 17, 19, to maintain the outer ring 2 in an at least substantially circular shape. The frame 3 is arranged to be submerged in the water such that a plane defined by the circular shape of the outer ring 2 is at least substantially horizontal.

A plurality of mutually parallel growing strings 9 for growing seaweed thereon are connected to the frame 3 such that the strings 9 are tensioned and thus extend in a more or less straight line within the growing area 13. The growing strings 9 are connected at the outer ring 2 and the cross member 4. The growing lines are of polyethylene but may alternatively be made of a different material.

Furthermore, the device 1 is provided with anchoring lines 1 1 . The anchoring lines 1 1 are in a cradle structure attached at two opposite sides of the outer ring 2 of the frame 3. The anchoring lines 1 1 are adapted to anchor the device 1 to for instance a sea bottom, in such a manner that the frame 3 can freely move in the depth direction 12.

The floating bodies 5 are shaped substantially elongated and formed as elongated hollow cylinders having closed, i.e. sealed ends. Air within each cylinder provides the required buoyancy. A cable 7 is connected to frame 3 at one end thereof, and connected to a floating body 5 at another end. The floating bodies 5 are connected to their respective associated cables 7 at an end 21 thereof.

The outer ring 2 comprises subsequent sections 20 of each time three mutually parallel tube members 23a, 23b and 23c having connection elements 25 at the ends thereof for mutually coupling a number of such sections 20 so as to obtain an endless circular shape. The cross member 4 comprises sections 20' of three mutually parallel tube members 23d, 23e and 23f of HDPE having connection elements 26 at the ends thereof, for interconnecting a number of such sections 20' so as to form the cross member 4. The tube members 23a-c as well as the tube members 23e-f are mutually connected via spacer pipes 27 providing further stiffening of the frame 3. The connection means 7 are attached to the spacer pipes 27 and/or tube members 23a-f via fastening means such as lugs 29. The anchoring lines 1 1 are attached to the connections elements 25.

The tube members 23a-f are hollow and are made of high density polyethylene. A metal chain runs through subsequent tube members 23a to 23f, respectively. The weight of the chain is chosen such that the frame will just sink in water such as sea water. The inner tube member 23b of the outer ring 2 is shorter than the other tube members 23a and 23b such that the circular shape is obtained after assembly of the sections.

The inner diameter of the outer ring 2 of the device shown in figure 1 is 60 meters. It comprises about 120 floating bodies along the outer ring 2, of which about 70 floating bodies are shown.

Upon use of device 1 for growing seaweed, the frame 3 is submerged in water and suspended at a predetermined depth below the water level. The depth of the frame 3 can be set by the length of the cables 7 in combination with the configuration of the floating bodies, more specifically the buoyancy thereof. In addition, the depth can be varied to certain extent by altering the number of floating bodies 5. However, in particular in less calm waters a relative large number of floating bodies is beneficial for reducing the influence of wind, waves and current. Typically the length of the cables 7 is chosen such that the frame is submerged at a depth in the range of 1 to 15 meter.

Figures 4 - 6 show a system 100 for growing sea weed comprising 20 devices 101 . The growing strings of the devices 1 are not shown in the figures 4 - 6. As figure 4 shows, the system 100 comprises strings of interconnected devices 1 , extending in parallel. Each string may comprise two up to tens of devices and one up to tens of strings of interconnected devices 1 may be provided. In an alternative embodiment of a system, for growing sea weed, the strings of interconnected devices are also mutually coupled to arrive at an array of interconnected devices. An array of interconnected devices is favourable for realising a relative high production capacity of seaweed per hectare of water surface of a volume of water. Neighbouring devices 1 are connected via anchoring lines 1 1 , coupling lines 1 1 1 a and anchor 131 at a sea bottom 133. Buoys 135 are attached to respective anchoring lines 1 1 and coupling lines 1 1 1 a to prevent anchoring lines 1 1 of neighbouring devices 1 getting tangled. The devices 1 are suspended at a predetermined depth d below the water level 137.

Claims

1 . Device for growing seaweed in a volume of water such as a sea, the device comprising a frame having a plurality of growing strings attached to the frame for growing seaweed thereon, further comprising a plurality of floating bodies that are connected to the frame, whereby the floating bodies are arranged to maintain the frame submerged at a substantially constant depth independent of a water depth, wherein the frame of said device comprises an outer ring surrounding a growing area and a cross member extending through the growing area, wherein the cross member is connected at two positions to the outer ring.

2. Device according to claim 1 , wherein the outer ring has a substantial circular shape and the cross member is configured to maintain the outer ring in the substantial circular shape.

3. Device according to claim 2, wherein an inner diameter of the outer ring is at least 10 meters, preferably at least 50 meters.

4. Device according to claim 2 or 3, wherein the plurality of growing strings extend mutually parallel in the growing area.

5. Device according to any one of the preceding claims, wherein growing strings of the plurality of growing strings, preferably each growing string, is suspended via both ends thereof from the frame.

6. Device according to any one of the preceding claims, wherein the device comprises a single cord forming the plurality of growing strings.

7. Device according to any one of the preceding claims, wherein the cross member is dividing the growing area in two areas of substantially equal size and/or shape.

8. Device according to any one of the preceding claims, wherein the plurality of floating bodies are distributed substantially evenly over the frame.

9. Device according to any one of the preceding claims, wherein a distance between neighbouring floating bodies of the plurality of floating bodies, or at least the connection thereof at the frame, is less than two metres.

10. Device according to any one of the preceding claims, wherein floating bodies of the plurality of floating bodies, preferably each of the plurality of floating bodies, have a substantially elongated shape in a longitudinal direction thereof, whereby the connection between a respective floating body and the frame is arranged to maintain the longitudinal direction of the floating bodies substantially upright in use.

1 1 . Device according to claim 10, wherein a cross-section of each of the floating bodies in longitudinal direction is substantially constant and preferably having an oval shape.

12. Device according to claim 10 or 1 1 , comprising, for each of the plurality of floating bodies, a cable that connects that floating body at an end thereof to the frame.

13. Device according to any one of the preceding claims, wherein the plurality of floating bodies are at least 100 floating bodies.

14. Device according to any one of the preceding claims, wherein said device further comprises a propulsion means that is arranged to maintain said device in a predetermined area of the water.

15. Device according to any one of the preceding claims, wherein the outer ring comprises at least two mutually parallel endless rings surrounding the growing area, wherein said endless rings are interconnected for stiffening of the frame.

16. Method for growing seaweed using a device according to any one of the preceding claims.

17. Method according to claim 16, wherein the frame is submerged at a depth in the range of 1 to 15 meters.

18. Method according to claim 16 or 17, comprising the steps of providing an anchor at the sea bottom and anchoring the device to the anchor, whereby a distance between said device and the anchor is at least two times larger than a shortest distance of said device to the sea bottom, so as to allow free movement of said device with respect to the sea bottom in the depth direction.

19. Method according to claim 16, 17 or 18 using a device according to claim 14 further comprising the step of propelling said device using the propulsion means for maintaining said device in a predetermined area of the water.

20. System for growing seaweed in a volume of water such as a sea, the system comprising at least two devices according to any one of the claims 1 to 15, wherein neighbouring devices are connected via an anchor at the sea bottom.