Patent Publication Number: US-2004042876-A1

Title: Method and apparatus for placing at least one wind turbine on open water

Description:
[0001] The invention relates to a method for placing at least one wind-mill on open water. The invention particularly relates to such a method for placing a windmill farm at sea—Such a method is known from practice.  
       [0002] In the known method, parts of a windmill are shipped, with the aid of a vessel, to a set-up location on open water, for instance a foundation built up on the sea floor. With the aid of a jack-up platform with crane, the parts are hoisted onto the foundation and assembled so as to form the desired windmill. Such a method has as a drawback that it requires relatively many shipping movements, while, for each windmill, the jack-up platform has to be brought into a floating position, has to be shipped to a subsequent set-up position and there has to be brought back into a position in which the platform extends entirely above the water. A further drawback of this method is that with a jack-up platform, only relatively small loads can be carried and the effective surface of such a platform is relatively small, so that only few parts can be placed thereon. Moreover, with this known method, employees have to work at relatively high altitude when assembling the windmill, to which altitude they have to be brought above open water with a crane or by climbing the windmill. In particular in unstable weather this is dangerous, particularly because of occurring swinging movements of the crane and the cages carried by cables in which the employees are received.  
       [0003] The invention contemplates a method of the type described in the preamble, wherein the drawbacks mentioned are obviated, while maintaining its advantages. To that end, a method according to the invention is characterized by the features of claim 1.  
       [0004] Using a vessel for shipping windmills to one or more set-up locations, which windmills have already at least for the larger part and preferably completely been assembled prior to shipping, and which can be placed in a simple manner on foundations already installed, offers the advantage that assembly of the windmills on open water is no longer necessary, at least that operations on open water are reduced to a minimum. The windmills are already assembled on land or near land and, supported by stages. arranged on the vessel. Assembly above land has the advantage that the working conditions are better controllable there, for instance by building in auxiliary stages, by using scaffoldings and the like. Swinging movements of cranes and the like as a result of swell are then precluded. Furthermore, thus, the advantage is achieved that the windmills can already be assembled in advance, also during a season when assembly on open water is virtually or completely impossible due to swell, wind, temperature and such weather conditions. Placing the or each windmill during the suitable season can then be done rapidly, with relatively few shipping movements. Surprisingly, it has been found to be relatively easy to hoist the windmills from the vessel in assembled condition and to place them onto the foundations with great accuracy.  
       [0005] In an advantageous embodiment, a method according to the invention is further characterized by the features of claim 3.  
       [0006] Stabilization of the vessel by supporting it on the floor of the open water offers the advantage that influences of movements of water on the vessel are considerably reduced. By subsequently lifting the vessel at least slightly out of the water and thus reducing its draft, the influence of the movements of water is virtually completely eliminated.  
       [0007] In a method according to the invention, the vessel can be partly lifted out of the water, whereby the draft is reduced, for instance, between 20% and 75%, thus achieving the advantage that the hoisting device can be designed to be relatively light, while still a substantially more stable position is obtained. In particular when several windmills are taken along simultaneously, this is particularly advantageous. An outstanding stabilization with a suitable lifting device for the vessel can be achieved by lifting the vessel out of the water by between 20% to 50%.  
       [0008] The vessel can also be arranged such that the vessel is, at least can be completely lifted above the water. Thus, the influence of the wave motion is even further reduced.  
       [0009] It is preferred that the vessel in lifted position be actively stabilized in particular when it is lifted out of the water only partly, by continuously monitoring and, if necessary, adjusting the pressure force of the legs on the basis of the wave motions and tidal movements, for instance with hydraulic or pneumatic means.  
       [0010] In a further advantageous embodiment, a method according to the invention is characterized by the features of claim 6.  
       [0011] As a result, the windmills and the hoisting device can be transported to the set-up location simultaneously, so that the number of shipping movements is still further reduced, while, furthermore, fewer vessels are required. Further, in this manner, the advantage is achieved that, each time, a hoisting device is available at the appropriate location, for instance also during shipping.  
       [0012] Preferably, the windmills are built up in the stages and wheeled onto the deck of the vessel. Then, preferably, two, three or four windmills are assembled next to each other in a stage, while a series of stages can be built up on the deck of the vessel, with, for instance, eight or ten completely built-up windmills. It is then preferred that a larger number of stages are used than are carried on the vessel. Then, in a number of the stages, on the quay, windmills are built up which, upon return of the vessel and the unloading of the empty stages, can be placed, in particular, wheeled onto the vessel, while in the empty, unloaded stages, once again, windmills can be built up. It will be clear that, thus, a complete windmill farm can be built up even more rapidly.  
       [0013] The invention further relates to an apparatus for placing at least one windmill on open water, characterized by the features of claim 11.  
       [0014] With such an apparatus, in a simple and rapid manner, with good working conditions, in a safe and economical manner, one or more windmills can be placed on open water.  
       [0015] A vessel according to the invention is preferably provided with means, in particular legs, with which it can be supported on the floor of this open water, as well as with means for lifting the vessel out of the water to some extent, such that its draft is at least reduced, for instance by 10, 20 or 50%, to be selected, for instance, depending on the load, the swell and further weather conditions and the like. By continuously monitoring and correcting the occurring forces on the legs, the possibility is provided to keep the vessel always in the desired position. Thus, in a simpler manner, it becomes possible to take up and place the at least substantially assembled windmills on the foundation with the hoisting device with great, at least sufficient accuracy.  
       [0016] Preferably, with a device according to the invention, a pontoon is used, in particular a pontoon with a relatively flat deck, which offers sufficient space for, for instance, six, eight or ten windmills, arranged in stages, as well as for a suitable hoisting device, for instance a mobile crane. Such pontoons axe known per se and can be provided in a relatively simple manner with, for instance, legs and stabilizing means according to the invention.  
       [0017] Further advantageous embodiments of a method and device according to the invention are given in the further subclaims. In clarification of the invention, a method and device according to the invention are further elucidated with reference to the drawing. 
     
    
    
     [0018] In the drawing:  
     [0019]FIG. 1 shows a windmill under construction, on a quay;  
     [0020]FIG. 2 shows a top plan view of a windmill under construction according to FIG. 1;  
     [0021]FIG. 3 shows, in perspective view, a windmill under construction, in a stage, according to FIGS. 1 and 2;  
     [0022]FIG. 4 shows, in top plan view, a vessel according to the invention, with eight windmills in stages;  
     [0023]FIG. 5 shows, in side view, a vessel according to FIG. 4;  
     [0024]FIG. 6 shows, in side view, a vessel according to FIG. 5, in a position partly lifted out of the water and stabilized, at a windmill park under construction, with the aid of a device and method according to the invention;  
     [0025]FIG. 7 schematically shows, in side view, a leg with adjusting means for a vessel according to the invention;  
     [0026]FIG. 8 shows in perspective view, schematically, a leg with adjusting means, in further elaboration; and  
     [0027]FIG. 9 shows, in perspective, partly cutaway view, a buffer system for a leg according to FIG. 7 or  8 . 
    
    
     [0028] In this description, identical or corresponding parts have identical or corresponding reference numerals. In this drawing, one type of windmill is the starting point, to which the device, in particular the or each stage, has been adjusted. It will be clear that for any type of windmill a suitable stage can be built up. In the embodiments shown, the windmills are built up and transported in substantially vertical, upright position. Thus, in a particularly advantageous manner, use can be made of the deck space of the vessel.  
     [0029] Moreover, thus, damage to in particular the generators of the windmills is prevented. Due to the generators used, many types of windmills are not to be transported in horizontal position. However, it will be clear that, with suitable windmills, also wholly or partly horizontal positions can be used in the stages, for instance for lowering the center of gravity of the vessel with the windmills or for reducing the building costs of the stages.  
     [0030] In FIG. 1 a stage  1  is shown, which rests on a quay  2 . The stage  1  comprises a platform  4  having thereon, in side view, triangular supports  6 , which, adjacent the top end, carry four brackets  8 . The brackets  8  extend above the platform  4 . As is clear from FIG. 2, the platform  4  is built up from a construction of profiles, wherein, next to each other, two pairs of supports  8  are arranged, each support carrying a bracket  8 . Two brackets  8  are attached directly against the supports  6 , while two neighboring brackets  8 A are situated at some distance from the support  6 . On the platform  4 , four windmills  10  can be built up, each supported by a bracket  8 ,  8 A. In the FIGS.  1 - 3 , each time, a fully built up windmill  10  is shown, as well as a second windmill  10 A which is under construction. The windmills are substantially built up from a column  12 , a generator  14  and vanes  16 , in a manner known per se. The bracket  8  engages the column  12 , for instance slightly above the middle, viewed in vertical direction, while the leg  12  is attached to the platform  4 . In this condition, the windmill  10  is secured in the stage  1  and can be moved therewith.  
     [0031] As is clear from FIG. 1, the windmill  10 ,  10 A can be built up with the aid of a mobile crane  18 , also in a manner known per se. To this end, different auxiliary means can be used, for instance temporary auxiliary constructions, lift cars and the like, such, that assembly is safe, under ergonomically sound conditions. As the brackets  8 ,  8 A are arranged in a staggered relation to each other, while two of the windmills  10  are arranged having the vanes facing outward and the other two windmills are arranged having the vanes facing each other, in the stage  1 , as is clear from for instance FIG. 4, four windmills  10  can be arranged in a relatively compact stage  1 .  
     [0032] After the windmills  10  have been assembled on the stage  1 . and have been anchored thereto, the stage  1  with the windmills  10  mentioned can be taken up and be or hoisted onto the deck of a vessel  20 , as shown in FIGS.  4 - 6 . This vessel  20  is, for instance, a pontoon with a substantially flat deck  22 . Viewed in the sailing direction V, on both sides of the pontoon  20 , a series of legs  24  are provided, which legs are adjustable within guiding constructions to be called sleeves connected to the pontoon or integrated therein. With the aid of hydraulic means, the legs can be moved in vertical direction P, between an at least virtually completely raised position shown in FIG. 5 and an at least virtually completely extended position shown in FIG. 6, while the legs  24  can rest on the floor  29  of an open water  30 , for instance the sea. This will be elaborated further.  
     [0033] As is clear from FIGS.  4 - 6  for instance two stages  1 , each with four windmills  10  can be placed on the deck  22 , for instance such, that a part  34  of the deck adjacent the stern  32  or, for instance a middle part of the deck between the stages, at least the respective deck space, remains clear of the stages. On this part  34 , a hoisting device is placed, such as a mobile crane  36 , for instance comparable to or a heavier type than the crane  18  as used on the quay  2 . During sailing of the pontoon, the crane  36  is secured to the deck  22 , while after release, it can be wheeled over the deck  22 .  
     [0034] After the stages  1  have been placed on the deck  22 , as well as the crane  36 , the pontoon  20  can be shipped, for instance be towed, to open water with the aid of tugboats appropriate to that end. Having arrived at the set-up positions where the windmills are to be placed, the pontoon is stopped, whereupon the legs  24  are brought to the extended position shown in FIG. 6, such that the pontoon  20  is lifted somewhat, so that its draft diminishes. In FIG. 6, the water line L 1  is shown during shipping of the pontoon, as well as the water line L 2 , when the pontoon  20  is somewhat lifted in the water. The draft can be reduced by, for instance, 10%, 20% or 50%, but can also be reduced much. more, depending on the legs  24 , guiding construction  26  and, for instance, hydraulic operating means for the legs  24  used. As an illustration, with a pontoon  20 , according to the invention, the draft can for instance be reduced from 2.˜meters to 2 meters. However, this should not be taken as being limitative in any way. Preferably, the complete vessel can be lifted above the water.  
     [0035] With the aid of the legs  24  and the guiding constructions  26 , as well as, in particular, the hydraulic means  28 , the pontoon  20  in the lifted position shown in FIG. 6 can be adjusted such, that the deck  22  is always level. To that end, control means  40  are provided with which, periodically or, preferably, continuously, the hydraulic pressures can be checked and means  28  can be controlled for maintaining the deck  22  in the desired, preferably level position. As the pontoon  20  is stabilized on the seafloor  29 , this is possible in a relatively easy manner, in particular as the pontoon  20  with the load resting thereon is somewhat or, which, periodically or, preferably, continuously, the hydraulic pressures can be checked and means  28  can be controlled for maintaining the deck  22  in the desired, preferably level position. As the pontoon  20  is stabilized on the seafloor  29 , this is possible in a relatively easy manner, in particular as the pontoon  20  with the load resting thereon is somewhat or, possibly completely, lifted above the water surface, so that wave motion has little or even virtually no influence thereon. As the deck  22  can. constantly be held virtually level, at least virtually steady, the crane  36  can be released so that with the crane  36 , the windmills  10  can be lifted from the stages  1  and be placed on the foundations  42 , which have been previously disposed on the floor  29  in the open water  30  and reach, preferably, above the water level L 2 . The windmills  10  can be secured thereto in a manner known per se, for instance with bolt connections  44 . Each time a windmill  10  is placed on a respective foundation  42 , the pontoon can be brought to the initial position by retracting the legs  24 , and can be sailed to a successive set-up location, where, in the same manner, a next windmill  10  can be placed on a foundation  42 . In this manner, with a pontoon  20  according to the invention, series of windmills can be placed on series of foundations  24  in a simple manner. Here, virtually no assembly on or above open water is required. so that placement is made possible in a very safe manner. In particular because the pontoon  20  can be stabilized on the seafloor  29 , undesirably large swinging movements of the windmills  10  during positioning are prevented, so that accurate placement is possible. Naturally, the windmills can there be guided, for instance by cables, rods or the like, from the deck  22 . However, this will often not be necessary.  
     [0036] In an advantageous embodiment of a method according to the invention, on the quay  2  in a stage  1  windmills  10  are assembled, while, with the vessel  20 , simultaneously, a series of windmills  10  are placed on foundations  42 . Upon returning at the quay  2 , the then prepared stages  1  with windmills  10  can be brought onto the deck  22 , in exchange for the then empty stages  1  on the vessel  20 . As a result, a substantially continuous process can be obtained, so that, rapidly. large series of windmills can be disposed on open water  30 .  
     [0037] In FIG. 7, schematically, a leg  24  with guiding construction  26  and adjusting means  28  is shown. In this embodiment, on the deck  22  a winch  50  is arranged, coupled to the control means  40 . Adjacent the upper side of the leg  24 , first guide pulleys  51  are provided and, adjacent the lower side of the leg, second guide pulleys  62 . Cables  53  extend from the winch  50  over the upper guide pulleys  51  and the lower guide pulleys  52  and are coupled by their free ends, via fastening elements  54 , to sleeves  26 , at least the pontoon  20 . Sensors  41  are coupled to the wires  53  with which, continuously, the occurring forces in the cables can be measured. Herewith, each time, the reactive forces in the cables as a result of, for instance, wave motions and the like can be registered, on the basis of which the winch  50  can he operated for, each time, keeping the legs  24  in the desired position. The fact is that with the aid of the winch  50 , the cables  53  can be adjusted, so that, within the sleeve  26 , the leg  24  can be adjusted relative to the deck  22 . Naturally, in a comparable manner, also other sensors can be used, for instance within the sleeves  26 , for measuring reactive forces. Also, other adjusting means  28  can be used, for instance hydraulic cylinders, toothed racks with fitting driving chain wheels or the like. With a vessel according to the invention, preferably each leg  24  is provided with adjusting means  28 , which are controllable independently of each other, while, preferably, the control means  40  of the adjusting device  28  are mutually coupled, so that a central control can be obtained and the vessel can always be held in the desired position.  
     [0038]FIG. 8 schematically shows, in perspective view, a part of a pontoon  20  with leg  24 , with a buffer system with which in particular impact forces occurring on the legs while placing them on the seafloor, can be compensated. Such forces are usually indicated as bouncing forces and, generally, form the boundaries within which a vessel can be used in waves. With the aid of the buffer means  27 . these bouncing forces can be compensated so that a larger area of application is obtained. In FIG. 9, somewhat enlarged and partly see-through, a part of the buffer means  27  is shown, in particular a casing  58  provided adjacent the deck  22 , with, included therein, a block  56  in which a series of second pulleys  52  are included, over which winch wires  53  are guided which, as is shown in FIG. 8, are attached over first pulleys  51  adjacent the upper end of the pole  24 . In FIG. 8, on both sides of the leg  24 , a casing  58  with block of pulleys  56  is shown, so that a symmetrical load is obtained.  
     [0039] With the aid of a number of, in the shown embodiment four, cylinders  66 , each block  56  is suspended to the upper plate  62  of the casing  58 . The cylinders  66 , two on each side of each block  56 , are preferable double-acting and can be connected to a storage barrel as with a gas, for instance nitrogen, or a liquid, for instance hydraulic oil. It will be clear that, to that end, any suitable fluid can be used.  
     [0040] The buffer means  27  as shown in. FIGS. 8 and 9 can be combined with adjusting means  28 , as described hereinabove with reference to, for instance, FIG. 7, but can also be used as adjusting means, to which end, hereto, a winch  50  is to be added. In an earlier described manner, sensors  41  with control means  40  can be added to the buffer means  27 . In the upper plate  62 , openings  64  are provided through which the cables  53  are guided, while, further, the casing  58  is closed to protect the block  56  and the pulleys  52 .  
     [0041] The invention is not in any way limited to the exemplary embodiments described and shown in the drawing. Many variations thereon are possible within the framework of the invention as outlined by the claims.  
     [0042] For instance, the stages can be designed differently and be made suitable for other numbers of windmills, for instance one or two windmills. Also, the stages can be designed such that the windmills are held in a different position, for instance such that the longitudinal axis of the column is at an inclination relative to the vertical. If generators are used which tolerate a horizontal position, the windmills can also be transported completely or largely horizontally, as a result of which, for instance, wind sensitivity will decrease during transport. As a consequence however, there will be a different requirement as to space on the vessel. Also, then, the windmills can be assembled in horizontal condition and subsequently be brought in a vertical position, for instance for placement in a stage  1  or from a deck of a vessel. With a device and method according to the invention, any type of windmill can be placed at sea, while, always, a suitable stage can be manufactured for at least placing and securing the windmills on the vessel for transport. Naturally, the stages can also be fixedly connected to the vessel, while the windmills are placed in the stages on the deck, optionally with the aid of an auxiliary stage.  
     [0043] These and many comparable variations are understood to fall within the framework of the invention as outlined by the claims.