Maintenance of an offshore wind farm making use of an assembly of a floating harbour ship and a plurality of shuttle vessels

Abstract

A method for use with maintenance of an offshore wind farm includes a plurality of offshore wind turbines installed in open sea, where the method uses an assembly of a plurality of shuttle vessels 8, 9 and a seaworthy harbour ship 1 which includes an internal harbour basin 4 within outlines of the ship 1 and a plurality of mooring positions 7 for mooring the plurality of shuttle vessels 8, 9 to the ship 1 when lying inside the basin 4 , where the method further includes comprises sailing the assembly of the plurality of shuttle vessels 8, 9 and the harbour ship 1 towards an anchoring position near or in the wind farm and anchoring the harbour ship 1 there, and sailing the plurality of shuttle vessels 8, 9 back and forth between the mooring positions 7 of the anchored harbour ship 1 and distinctive ones of the wind turbines for performing the maintenance thereto.

1 . A method for use with maintenance of an offshore wind farm comprising a plurality of offshore wind turbines installed in open sea, in which the method comprises:
 providing a shuttle vessel for transfer of service engineers and/or goods to and from the wind turbines;   sailing the shuttle vessel to one of the wind turbines;   landing the shuttle vessel against the wind turbine for allowing transfer of the service engineers and/or goods between the shuttle vessel and the wind turbine;   sailing the shuttle vessel to another wind turbine for allowing transfer of service engineers and/or goods between the shuttle vessel and that other wind turbine; and   sailing the shuttle vessel to a harbour facility and mooring it there for allowing exchange of the service engineers and/or the goods between the shuttle vessel and the harbour facility before sailing the shuttle vessel out to another wind turbine;   wherein the method makes use of an assembly of a plurality of the above-mentioned shuttle vessels and a seaworthy harbour ship which serves as the abovementioned harbour facility and for this comprises an internal harbour basin within outlines of the ship and a plurality of mooring positions for mooring the plurality of shuttle vessels to the ship when lying inside the basin, the basin being provided with an entrance opening for the shuttle vessels to sail into and out of the basin;   wherein the method further comprises:
 sailing the assembly of the plurality of shuttle vessels and the harbour ship towards a halt position near or in the wind farm and substantially keeping the harbour ship in its halt position; and 
 sailing the plurality of shuttle vessels back and forth between the mooring positions of the halted harbour ship and distinctive ones of the wind turbines for performing the maintenance thereto. 
   
     
     
         2 . The method according to  claim 1 , wherein the harbour ship, while being kept substantially in its halt position, is maintained in a position in which the entrance opening for the shuttle vessels to sail into the basin lies leeward. 
     
     
         3 . The method according to  claim 1 , wherein both during the sailing of the assembly towards the halt position as well as during the sailing of the plurality of shuttle vessels back and forth between the halted ship and the wind turbines, the internal basin is kept filled with sea water. 
     
     
         4 . The method according to  claim 3 , wherein both during the sailing of the assembly towards the halt position as well as during the sailing of the plurality of shuttle vessels back and forth between the halted ship and the wind turbines, the internal basin is kept in open connection with the surrounding sea water by means of its entrance opening being open for the shuttles to sail into and out of the basin at all times. 
     
     
         5 . The method according to  claim 3 , wherein both during the sailing of the assembly towards the halt position as well as during the sailing of the plurality of shuttle vessels back and forth between the halted ship and the wind turbines, the internal basin is kept in open connection with the surrounding sea water by means of the basin having its bottom at least partially open for the surrounding sea water to flow into and out of the basin. 
     
     
         6 . The method according to  claim 4 , wherein adjustable flow through openings of damping means are provided in the basin which openings are adjusted in dependence of sea swell inside the basin. 
     
     
         7 . The method according to  claim 1 , wherein the harbour ship is halted near or in a wind farm which lies at least 30 miles offshore and comprises at least a hundred wind turbines which are each visited for maintenance within a period of less than a month by using a number of at least two of said shuttle vessels at the same time and mooring them at least during the night during the maintenance period inside the basin of the harbour ship. 
     
     
         8 . The method according to one  claim 1 , wherein, in the case of relocation of the harbour ship and/or during extreme weather conditions, the shuttle vessels are taken out of the water and placed upon a deck of the harbour ship. 
     
     
         9 . The method according to  claim 1 , wherein the harbour ship is further equipped with sleeping quarters for the service engineers. 
     
     
         10 . A harbour ship, in particular for use in the method according to  claim 1 , comprising:
 a seaworthy floating construction;   halting means for substantially keeping the floating construction in a halt position at open sea;   an internal harbour basin within the outlines of the floating construction which basin has an entrance opening for shuttle vessels to sail into the basin; and   a plurality of mooring positions for mooring a plurality of shuttle vessels to the floating construction when lying inside the harbour basin;   wherein the internal basin has an open connection with the surrounding sea water such that it is kept filled with sea water both during sailing and anchoring.   
     
     
         11 . The harbour ship according to  claim 10 , wherein the internal basin has its entrance opening in open connection with the surrounding sea water. 
     
     
         12 . The harbour ship according to  claim 10 , wherein the internal basin has an at least partially open bottom such that the basin is in open connection with the surrounding sea water. 
     
     
         13 . The harbour ship according to  claim 10 , wherein the basin is provided with damping means that comprise adjustable flow through openings for damping sea water flowing through these openings. 
     
     
         14 . The harbour ship according to  claim 12 , wherein the damping means comprise adjustable panels which at least partly delimit the basin at its lower side, in particular extending in a transverse direction of the harbour ship. 
     
     
         15 . The harbour ship according to  claim 10 , wherein sleeping quarters are provided for personnel of the plurality of shuttle vessels. 
     
     
         16 . The harbour ship according to  claim 10 , wherein the floating construction comprises deck space for at least some of the plurality of shuttle vessels to be placed upon, and lifting means for taking one of the shuttle vessels out of the basin onto the deck space. 
     
     
         17 . The harbour ship according to  claim 10 , wherein propulsion means are provided which comprise thrusters for turning the floating construction, while being substantially kept in its halt position, towards a position in which the entrance opening of the basin is kept leeward. 
     
     
         18 . The harbour ship according to  claim 10 , wherein propulsion means are provided for propelling the floating construction over sea to its halt position. 
     
     
         19 . The harbour ship according to  claim 10 , wherein the floating construction comprises two longitudinal floating bodies delimiting opposite sides of the basin, which floating bodies are connected at their front sides by a bow. 
     
     
         20 . The harbour ship according to  claim 19 , wherein the floating bodies each comprise an anti-rolling fluid tank, which tanks are connected to each other by a fluid duct in which pumping means are provided for pumping fluid from one tank to the other one in a direction which is opposite to a rolling movement of the floating construction around its longitudinal central axis in response to sea swell. 
     
     
         21 . The harbour ship according to  claim 20 , wherein the duct extends underneath the basin. 
     
     
         22 . The harbour ship according to  claim 10 , wherein the basin is provided with at least two mooring positions in its basin and has dimensions large enough for mooring at least two vessels inside the basin at the same time. 
     
     
         23 . The harbour ship according to  claim 10 , wherein the halting means comprise dynamic positioning means for substantially keeping the floating construction in its halt position at open sea. 
     
     
         24 . The harbour ship according to  claim 10 , wherein the halting means comprise anchoring means for substantially keeping the floating construction in its halt position at open sea. 
     
     
         25 . An assembly of a harbour ship according to  claim 10  and a plurality of shuttle vessels.