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EP-4735326-A1 - BARGE FOR ASSEMBLY OF A FLOATING SUPPORT STRUCTURE

EP4735326A1EP 4735326 A1EP4735326 A1EP 4735326A1EP-4735326-A1

Abstract

The invention describes a barge for assembly of a floating support structure (1) comprising a lower buoyancy section (2) with a lower buoyancy volume V L and a working deck (3) comprising support elements (4) for receiving parts of the floating support structure to be assembled. The barge further comprises a ballasting system (7) for lowering and elevating the barge (1). The barge is characterized by a divisional section (6) holding the lower buoyancy section (2) and the working deck (3) in a vertical distance from each other and having a divisional buoyancy volume V D considerably smaller than lower buoyancy volume V L , such that the ballasting system, by pumping a quantity of water equal to V D in or out, is able to move the barge (1) between a lower position with a bottom side of the working deck (3) in the waterline, and an upper position with the top side of the lower buoyancy section (2) in the waterline.

Inventors

  • APELAND, INGVAR
  • ALQUIST TØNNESSEN, Reidar

Assignees

  • Ocean Ventus AS

Dates

Publication Date
20260506
Application Date
20240625

Claims (16)

  1. 1. Barge (1) for assembly of a floating support structure (8) comprising: a lower buoyancy section (2) with a lower buoyancy volume VL, a working deck (3) comprising support elements (4) for receiving parts of the floating support structure to be assembled, a ballasting system (7) for lowering and elevating the barge (1), characterized by a divisional section (6) holding the lower buoyancy section (2) and the working deck (3) in a vertical distance from each other and having a divisional buoyancy volume VD considerably smaller than the lower buoyancy volume VL, such that the ballasting system, by pumping a quantity of water equal to VD in or out, is able to move the barge between a lower position with a bottom side of the working deck (3) in the waterline, and an upper position with the top side of the lower buoyancy section (2) in the waterline when the barge is unaffected by external buoyancy volumes.
  2. 2. Barge according to claim 1, wherein a major part of the divisional buoyancy volume VD resides in buoyancy structures (12) extending in the entire height of the divisional section (6) and being positioned in an area at least comprising each corner of the barge to provide stability when the lower buoyancy section is totally submerged.
  3. 3. Barge according to claim 2, wherein the divisional section (6) comprises stabilizing pillars (12) at each corner of the barge (1) extending between the lower buoyancy section (2) and the working deck (3) for stabilizing the barge when the lower buoyancy section is submerged (6).
  4. 4. Barge according to any of the preceding claims, wherein the working deck (3) comprises a safety buoyancy volume Vw.
  5. 5. Barge according to any of the preceding claims, wherein the divisional section (6) comprises support beams (13) extending between the lower buoyancy section (2) and the working deck (3).
  6. 6. A floating support structure (1) to be assembled on a barge according to claim 1- 5.
  7. 7. The floating support structure according to claim 6 comprising: a horizontal transverse part (16) having a first and second vertical transverse buoyancy unit (17a, 17b) at each end respectively and a horizontal aft part (18) connected to a midpoint of the transverse part (16) and having a vertical aft buoyancy unit (19) at the aft end thus providing an open space underneath the horizontal transverse and aft parts (16, 19) for accommodating the barge (1) and a connecting flange (15) for connecting a windmill tower (9).
  8. 8. The floating support structure (1) according to claim 6 comprising: a first, second and third main section (33a, 33b, 33c) each comprising a horizontal part (29) and a vertical part (30), wherein the vertical part comprises a buoyancy unit (31), a central transition piece (34) for connecting the respective three horizontal parts of the main sections by means of respective connector ends (35) adapted to fit the respective horizontal parts, the central transition piece further comprising a connecting flange (15) for connecting the windmill tower (9).
  9. 9. The floating support structure according to claim 6 wherein the floating support structure is manufactured in a set of subparts (20) comprising first, second, third, etc. subparts (20a, b, c...) constituting the floating support structure when assembled.
  10. 10. The floating support structure according to claim 7 and 9, wherein the set of subparts (20), comprises: the first subpart (20a) comprising the vertical aft buoyancy unit (19) and the horizontal aft part (18), the second subpart (20b) comprising the first vertical transverse buoyancy unit (17a), a major section of the horizontal transverse part including a connector (23) for connecting the horizontal aft part to the midpoint of the horizontal transverse part and, and the third subpart (20c) comprising the second vertical transverse buoyancy unit (17b) and a minor section of the horizontal transverse part.
  11. 11. The floating support structure according to claim 8 and 9, wherein the set of subparts (20), comprises: the first subpart (20a) comprising the central transition piece (34), and the second, third and fourth subpart (20b-d) comprising the first, second and third main section (33a, 33b, 33c) respectively.
  12. 12. The floating support structure according to any of claims 9 - 11 wherein each subpart of the set of subparts (20) have suspension connectors (21) positioned such that the horizontal sections of the subpart are horizontal when lifting lines are connected to the suspension connectors (21) and suspended from the lifting device (14).
  13. 13. Method for assembly of a floating support structure (8) according to claim 9 by means of a barge according to 1-5 and a lifting device (14) positioned at a quayside (25) for lifting a set of subparts (20) that constitutes the floating support structure (8) when assembled, the method comprising the steps: a. proving the subparts (20) that constitutes the floating support structure (8), b. lifting a subpart onto the barge (1) using the lifting device (14) letting the subpart (20) rest on the support elements (4) and, if needed for stability, also letting the subpart remain suspended from the lifting device while the subpart is connected to a previously positioned subpart if the lifted subpart is not the first to be lifted onto the barge, c. when the assembly is completed, lowering the barge by means of the ballasting system (7) until the floating support structure is free of all obstacles on the barge (1) and d. removing the barge from underneath the floating support structure.
  14. 14. Method according to claim 13, when dependent on claim 10 wherein step b comprises the following substeps: 1. Lifting the second subpart (20b) onto the barge, 2. Lifting the third subpart (20c) onto the barge and holding the second transverse subpart (20c) in position with the lifting device until it is connected to the second subpart (20b), and 3. Lifting the first subpart (20a) onto the barge and connecting the aft horizontal part to the connector (23) of the first transverse subpart (20b).
  15. 15. Method according to claim 13, when dependent on claim 11 wherein step b comprises the following substeps: 1. lifting the first subpart (20b) onto the barge and positioning a connector end (35) in a direction parallel to the quayside (25), 2. lifting the second subpart onto the barge and connecting it to the first subpart (20a, 3. turning the barge until the second subpart (20b) is perpendicular to and pointing outward from the quayside (25), 4. lifting the third and fourth subpart (20c and d) onto the barge and connecting them to the connector ends (35) of the first subpart (20a) in succession.
  16. 16. Method according to any of the claims 13 - 15 wherein step c comprises moving the barge to deeper water before lowering the barge.

Description

Title: BARGE FOR ASSEMBLY OF A FLOATING SUPPORT STRUCTURE Technical field The invention relates to off-shore wind turbines, more specifically to a barge used for assembly of a floating support structure for an offshore wind turbine. Background Floating support structures for offshore wind turbines are known in the art and several methods for assembly of wind turbines and the substructure have been described. A common disadvantage for many of the known floating support structures are the issues arising from the assembly process. Issues that may arise are excessive space requirement on shore, low assembly rate, and limited depth by the quay side at assembly location. As the size, and thereof the weight, of the wind turbines have increased, the size of equipment for assembly have also increased and the depth of typical support structure for a 15 MW wind turbine is a lot more that 10 meters when the tower and nacelle is mounted. A harbor with a depth deeper than 10 meters are hard to find and/or expensive to build. Ideally, the assembly site should also be close to the final destination, i.e. the wind park, because towing of the wind turbine is expensive and time consuming. One partial solution is to assemble the floating support structure on shore and mount the tower and nacelle at sea, but this puts high demands on a crane big enough to rise a tower at sea. In view of the above, it is an object of the invention to provide a process that mitigates several of the problems related to use of prior art solutions. An object of the invention is to find a way to assemble a large floating support structure at a quay side with limited depth. Another object of the invention is to reduce the assembly area needed near the quay side. Another object of the invention is to reduce the time consumed when assembling a floating support structure and wind turbine. Another object is to reduce the time and energy consumption during launching the completed floater/turbine assembly. Summary of the invention In a first aspect of the invention it is described a barge for assembly of a floating support structure. The barge comprises a lower buoyancy section with a lower buoyancy volume VL, a working deck comprising support elements for receiving parts of the floating support structure to be assembled and a ballasting system for lowering and elevating the barge. The barge further comprises a divisional section holding the lower buoyancy section and the working deck in a vertical distance from each other and having a divisional buoyancy volume VD considerably smaller than lower buoyancy volume VL, such that the ballasting system, by pumping a quantity of water equal to VD in or out, is able to move the barge between a lower position with a bottom side of the working deck in the waterline, and an upper position with the top side of the lower buoyancy section in the waterline when the barge is unaffected by external buoyancy volumes from structures resting on the barge. In an embodiment of the barge a major part of the divisional buoyancy volume VD resides in buoyancy structures extending in the entire height of the divisional section and being positioned in an area at least comprising each corner of the barge to provide stability when the lower buoyancy section is totally submerged. In an embodiment of the barge the divisional section comprises stabilizing pillars at each corner of the barge extending between the lower buoyancy section and the working deck for stabilizing the barge when the lower buoyancy section is submerged. In yet an embodiment of the barge the working deck comprises a safety buoyancy volume Vw. In yet an embodiment of the barge the divisional section comprises support beams extending between the lower buoyancy section and the working deck. In a second aspect of the invention it is described a floating support structure to be assembled on a barge as described above. In an embodiment the floating support structure comprises a horizontal transverse part having a first and second vertical transverse buoyancy unit at each end respectively and a horizontal aft part connected to a midpoint of the transverse part and having a vertical aft buoyancy unit at the aft end thus providing an open space underneath the horizontal transverse and aft parts for accommodating the barge. The floating support structure further comprises a connecting flange for connecting a windmill tower. In an embodiment the floating support structure comprises a first, second and third main section each comprising a horizontal part and a vertical part, wherein the vertical part comprises a buoyancy unit. The floating support structure further comprises a central transition piece for connecting the respective three horizontal parts of the main sections by means of respective connector ends adapted to fit the respective horizontal parts, the central transition piece further comprising a connecting flange for connecting the windmill tower. In an embodimen