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RELATED APPLICATIONS 
       [0001]    This application claims priority from Provisional Patent Application No. 60/921,432 filed Apr. 2, 2007, the disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to harvesting wind energy in deep waters of the ocean far away from shore with floating wind turbines anchored to the sea bottom. 
       BACKGROUND OF THE INVENTION 
       [0003]    At the present time most of the wind turbines are located on land or offshore in shallow waters and rest on stable foundations. The recently increased use of wind turbines created backlash from populations living near them due to their noise, negative visual impact and the killing of birds. This is one of the reasons that prompted attempts to install wind turbines out of sight of populations living along coastlines. The other reason for the development of this new technology is that winds in open seas are more steady and stronger, which significantly improves the economic efficiency of wind turbines. A further reason is that oceans provide unlimited areas where wind can be harvested at a cost that is competitive with the cost of generating electricity with conventional power plants. 
         [0004]    A major obstacle to achieving this goal is the existing technology of assembling modern wind turbines, which requires very large cranes that assemble windmills piece by piece and are not suited for assembling wind turbines in deep waters. In shallow waters, jack-up platforms are used as the base for crane operation, but they can only be deployed to limited depths of not more than about 60 meters. Use of floating cranes for assembling wind turbines in the open sea is impractical due to floating crane unavoidable rolling and pitching, which creates wide amplitudes of undesirable vertical and horizontal crane hook movements. 
         [0005]    Newly appearing technology of harvesting wind energy in deep waters far away from shorelines is based on the use of floating structures anchored to the ocean floor and having minimum waterplane areas to withstand hurricane category wave actions. To avoid the use of cranes in open seas, the windmills have to be fully assembled in shallow water protective harbors, and they must then be moved in their upright positions to the points of installation. Since these deepwater installations have very small waterplane areas, they require special technology, which does not yet exist, to assemble them in shallow waters and to transport them safely through open seas to the point of installation. The most promising type of floating platform for wind turbines in deep waters is the tension leg platform with a gravity-type anchoring base. However, the weight of the gravity anchoring base (“GAB”) for modern wind turbines of 5 MW capacities can be as high as 10,000 tons in water, which creates problems for their manufacture, delivery and installation. There is further the problem of attaching and tensioning tethers to floating platforms, which presently requires special vessels and lengthy, complicated procedures. 
         [0006]    The development of the new technology for locating and operating windmills in deep waters started only a few years ago, and as a result the available prior art is limited. The available prior art does not address the above-mentioned problems of assembling wind turbines in deep waters, transporting them in upright positions to their destinations, installing gravity anchors and attaching hold-down structures such as tethers to floating platforms of the windmills to secure them in place. The most relevant, recent U.S. patents include:
       U.S. Pat. No. 7,156,586 B2 for a “Wind turbine with floating foundation” by Nim. This patent offers a new tension leg platform having three separate pontoons, but provides no information how the turbines are to be assembled, transported to a destination site and installed there.   U.S. Pat. No. 7,156,037 for a “Device for wind power station placed in deep water” by Borgen discloses two embodiments, one that consists of a tower attached to the ocean floor through a rigid rod, and the other which has the same tower, but it floats and is anchored to the ocean floor with several anchors. Both embodiments expect the tower to incline under wave and wind forces and therefore have means to keep the wind turbine perpendicular to the wind direction. Both have significant rigid ballasts for lowering the device center of gravity and water ballast, the volume of which can be changed to thereby provide the required counter moment to withstand wind and wave forces. Also, both embodiments have their wind turbines located on the leeward side of the tower to prevent propeller blades from smashing into the tower during platform inclinations. This patent does not indicate how the device is assembled, towed to the installation site and installed.   U.S. Pat. No. 7,075,189 for “Offshore wind turbine with multiple wind rotors and floating system” by Heronemus, et al. discloses a floating semi-submersible platform in the form of a vertically oriented tubular column with a very small waterplane area. It is moored to a single anchor point, which allows it to naturally weathervane under wind force. The above-water structure supports several wind turbines. To reduce the angle of inclination of the entire structure and prevent it from sinking under waves, a rigid ballast is located well below the ocean surface and further uses a water ballast for controlling the depth to which this system sinks. This patent does not explain how the windmill is assembled, delivered to its desired destination and installed.       
 
         [0010]    A paper, “Design of a Semi-Submersible Platform for a 5 MW Wind Turbine”, presented to the AIAA Aerospace Sciences Meeting on 9-12 Jan. 2006 in Reno, Nev., uses a tension leg floating platform and a gravity anchoring base. In comparison to the above-mentioned patents, this paper provides for a stable positioning of the wind turbine without using any system that must operate continuously, which makes this design more reliable and practical. This paper also describes how the GAB can be manufactured and delivered to the designated point and how it might be installed. According to this technology, the anchoring base would be fully manufactured on the shore and is then moved to a floating dry-dock. The dry-dock moves to the floating platform construction site, from which the floating platform with the assembled wind turbine on it moves on the anchoring base in the dry-dock. There they are coupled and the dry-dock sinks, allowing them to free-float with sufficient waterplane area to provide needed stability during towing by tugs to an installation site. There, under control of three winches, each having a single wire rope that serves as a tether, the anchoring base is lowered to the sea bottom. After the anchoring base is installed, the winches on the floating platform pull it down below water to the project depth. This is done by combining winch pull with ballasting the inner space of the floating platform pontoon. This paper is a result of R&amp;D investigation contracted by the National Renewable Energy Laboratories of the Department of Energy. 
       SUMMARY OF THE PRESENT INVENTION 
       [0011]    It is an objective of the present invention to provide means and methods for assembling wind turbines near shore in shallow waters, transporting them to their destination sites, and installing and anchoring them in deep waters in a manner of hours with a minimum of manpower and without the help of floating cranes, which leads to a significant reduction in installation and assembling time to thereby reduce the total cost of wind turbines installed in deep waters. 
         [0012]    A deepwater windpower plant (“DWP”) according to the present invention uses a tension leg platform concept and comprises a typical offshore windmill assembled on a floating platform (tension leg platform) attached to a gravity anchoring base that rests on the ocean floor. 
         [0013]    In accordance with a first aspect of the instant invention, a special onshore high-rise crane station with underwater supports is used for completely assembling the floating offshore windmill or generator. The crane installed at this station has a relatively short boom, which allows it to operate in relatively strong winds. Presently windmills are assembled with cranes having a very long boom (100+ meters), because of the need for placing the nacelle and the wind turbine on towers that are 80+ meters high. This restricts their operation to periods when winds are relatively weak. They are therefore not adapted for a year-round operation, especially in areas where strong rather than relatively weak winds are frequently encountered. 
         [0014]    A second aspect of the instant invention employs a special catamaran-type vessel, also referred to herein as a “DWP installer”, with which floating wind turbines that were fully assembled close to shore are towed to destination sites while in their vertical positions. The DWP installer engagement and guiding arrangement allows the DWP free vertical movement due to wave action, but the degree of DWP inclination under wave and wind actions is limited by the stability of the catamaran-type vessel. In this manner the DWP can be delivered to a destination site even in moderately stormy seas. 
         [0015]    A third aspect of the present innovation concerns the installation of the gravity anchoring base (GAB) and loading ballast in it.
       In accordance with a first embodiment of the instant invention, the GAB is towed to the destination point as a pontoon in a form of an open box or container. The fully assembled tethers and power cable with buoys are loaded into the box, which is sunk to the ocean floor. After the GAB has been sunk to the ocean floor, dump barges unload suitable ballast, such as rock, for example, into the GAB. The use of this embodiment might not be practical in areas with strong currents and in deep waters, where unloaded ballast from dump barges might disperse over a large area and therefore not efficiently fill the GAB with ballast material.   In accordance with an alternative embodiment of the instant invention, the floating GAB is loaded with ballast near shore by cranes and assembled with the appropriate tethers and power cable. For the purpose of being floated and towed to a destination point, the GAB is provided with additional buoyancy formed by upward extensions of its side walls. It uses the same process of sinking to the ocean floor as was described in connection with the earlier described embodiment.       
 
         [0018]    These embodiments of the innovation relating to the GAB include:
       A special floating, stabilizing platform, for controlling the sinking of the GAB to the ocean floor, provides the condition that assures a flat landing of the GAB on the ocean floor. This simplifies its installation by eliminating the need for cranes that control the descent of the GAB to the ocean floor.   For future connection of the DWP to the GAB, tethers and the power cable are brought up to the ocean surface with buoys, which are attached to anchors on the GAB while the GAB is being lowered to the ocean floor. This creates the conditions needed for an automatic attachment of the DWP floating platform to the tethers.       
 
         [0021]    A further embodiment of the invention uses an automated method of connecting the floating base of the wind generator to the tethers in a matter of minutes. In combination with pre-positioning the tethers near the surface, the need for multiple auxiliary vessels and cranes is eliminated, which are needed for conventionally connecting floating platforms to tethers attached to the anchoring base. 
         [0022]    Another feature of the invention is the configuration of the tether, which utilizes multiple standard wire ropes or cables in the form of a loop instead of conventional steel tubular members used by the offshore industry for accommodating thousands of tons of force acting on tethers supporting tension leg platforms. The loop form of wire ropes simplifies the attachment and disconnection of wire ropes to and from the GAB. It also excludes the need for wire rope end connectors, which in the case of large diameter wire ropes are difficult to use and reduce the strength of wire rope connection. 
         [0023]    The use of the DWP installer and the speedy method of disconnecting and reconnecting the DWP to the anchoring base provides conditions for replacing heavy parts of windmills or entire nacelles by floatingly moving the entire wind generator to a high-rise crane station, where required replacements can be done in a relatively short time and in a safe manner, and thereafter returning it to the offshore site for reinstallation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  shows a deepwater windpower plant (DWP) during operation (elevational view); 
           [0025]      FIG. 2  shows a deepwater windpower plant (DWP) during operation (side view); 
           [0026]      FIG. 3  shows a floating base general arrangement (Section A-A from  FIG. 5 ); 
           [0027]      FIG. 4  shows a floating base general arrangement (side view); 
           [0028]      FIG. 5  shows a floating base (plan view); 
           [0029]      FIG. 6  is Detail I from  FIG. 3 ; 
           [0030]      FIG. 7  is Detail II from  FIG. 5 ; 
           [0031]      FIG. 8  is Detail III from  FIG. 5 ; 
           [0032]      FIG. 9  is a section taken along B-B of  FIG. 8 ; 
           [0033]      FIG. 10  shows Section C-C of  FIG. 9 ; 
           [0034]      FIG. 11  is View D from  FIG. 9 , without center cone  77 ; 
           [0035]      FIG. 12  shows a tether in elevational view; 
           [0036]      FIG. 13  shows a tether in side view; 
           [0037]      FIG. 14  shows an empty gravity anchoring base (GAB) in plan view (Embodiment I); 
           [0038]      FIG. 15  shows an empty GAB in section taken along E-E from  FIG. 14 ; 
           [0039]      FIG. 16  shows an empty GAB assembled with tethers in plan view; 
           [0040]      FIG. 17  shows an empty GAB assembled with tethers along Section F-F of  FIG. 16 ; 
           [0041]      FIG. 18  shows a GAB installed on the ocean floor in plan view; 
           [0042]      FIG. 19  shows a GAB installed on the ocean floor and is taken along Section G-G of  FIG. 18 ; 
           [0043]      FIG. 20  is Detail IV from  FIG. 18 ; 
           [0044]      FIG. 21  is a section view taken along H-H of  FIG. 20 ; 
           [0045]      FIG. 22  is a section view taken along K-K of  FIG. 21 ; 
           [0046]      FIG. 23  shows a stabilizing platform in plan view; 
           [0047]      FIG. 24  shows a stabilizing platform in elevational view; 
           [0048]      FIG. 25  illustrates the process of transporting and installing an empty GAB at Positions I and II; 
           [0049]      FIG. 26  illustrates the process of transporting and installing an empty GAB at Positions III and IV; 
           [0050]      FIG. 27  illustrates the process of transporting and installing an empty GAB at Positions V and VI; 
           [0051]      FIG. 28  illustrates the process of transporting and installing an empty GAB at Positions VII and VIII; 
           [0052]      FIG. 29  illustrates the process of unloading ballast from a dump barge into the GAB in an elevational view; 
           [0053]      FIG. 30  illustrates the process of unloading ballast from a dump barge into the GAB in section; 
           [0054]      FIG. 31  shows the DWP installer in elevational view; 
           [0055]      FIG. 32  shows the DWP installer in side view; 
           [0056]      FIG. 33  shows the DWP installer in plan view; 
           [0057]      FIG. 34  shows the DWP installer, Detail IX from  FIG. 32 ; 
           [0058]      FIG. 35  shows the closed position of the DWP installer engaging guide; 
           [0059]      FIG. 36  shows the open position of the DWP installer engaging guide; 
           [0060]      FIG. 37  shows a floating platform delivered and installed on underwater supports near a high-rise crane station; 
           [0061]      FIG. 38  illustrates the installation of the DWP tower; 
           [0062]      FIG. 39  illustrates the installation of the DWP nacelle; 
           [0063]      FIG. 40  illustrates the installation of the DWP wind turbine; 
           [0064]      FIG. 41  shows the completed DWP and a DWP installer approaching it; 
           [0065]      FIG. 42  shows the DWP installer engaging the DWP; 
           [0066]      FIG. 43  is a plan section taken on H-H of  FIG. 40 ; 
           [0067]      FIG. 44  shows the DWP lifted from its underwater supports and connected to a tug; 
           [0068]      FIG. 45  shows the DWP installer with the DWP being towed by tug to open sea in elevational view; 
           [0069]      FIG. 46  shows the DWP installer with the DWP being towed by tug to open sea in side view; 
           [0070]      FIG. 47  shows the DWP installer approaching mooring tethers; 
           [0071]      FIG. 48  shows the DWP installer in elevation and the DWP engaged with mooring tethers; 
           [0072]      FIG. 49  illustrates the process of engaging the floating base with the mooring tethers; 
           [0073]      FIG. 50  shows in side view the DWP installer engaged with mooring tethers and tensioning them; 
           [0074]      FIG. 51  is Detail X from  FIG. 49 ; 
           [0075]      FIG. 52  is Detail XI from  FIG. 50 ; 
           [0076]      FIG. 53  shows the DWP installer in the process of disconnecting the tether buoys  71 ; 
           [0077]      FIG. 54  shows the DWP installer being towed away with attached tether buoys from the DWP; 
           [0078]      FIG. 55  shows an empty gravity anchoring base (GAB) in plan view (Embodiment II); 
           [0079]      FIG. 56  shows a floating empty GAB taken along Section L-L of  FIG. 55 ; 
           [0080]      FIG. 57  shows a ballast loaded GAB assembled with tethers in plan view; 
           [0081]      FIG. 58  is a section of the GAB loaded with ballast and assembled with tethers taken along M-M of  FIG. 57 ; 
           [0082]      FIG. 59  shows a ballast loaded GAB installed on the ocean floor in plan view; 
           [0083]      FIG. 60  shows a ballast loaded GAB installed on the ocean floor and is taken along N-N of  FIG. 59 ; 
           [0084]      FIG. 61  is Detail XII from  FIG. 59 ; 
           [0085]      FIG. 62  is Section O-O of  FIG. 61 ; 
           [0086]      FIG. 63  is Section P-P of  FIG. 62 ; 
           [0087]      FIG. 64  illustrates the process of transporting and installing an empty GAB at Positions I and II; 
           [0088]      FIG. 65  illustrates the process of transporting and installing an empty GAB at Positions III and IV; 
           [0089]      FIG. 66  illustrates the process of transporting and installing an empty GAB at Positions V and VI; and 
           [0090]      FIG. 67  illustrates the process of transporting and installing an empty GAB at Positions VII and VIII. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0091]      FIGS. 1 and 2  illustrate a deepwater windpower plant (DWP)  21  and its operation under wind and wave forces. It has a typical offshore wind turbine  22 , with a nacelle  24 , a floating platform  26 , at least three tethers  27 , the number of tethers preferably being an uneven number to prevent generating undesirable moments on a gravity anchoring base (GAB)  28 , and a power output cable  29 . 
         [0092]      FIGS. 3 through 11  illustrate the design of floating platform  26 . It has a doughnut-shaped pontoon  31 , a boarding platform  33  having a flange  34  for the quick connection with a tower  25  of a typical offshore wind turbine, three legs  35  that connect pontoon  31  to boarding platform  33 , and a central berthing post  36 . Boarding platform  33  includes a deck  37  and a berthing ring  39 , which also serves as a conduit for compressed air. The doughnut-shaped pontoon  31  is a vessel that can contain water and/or compressed air and it has on its bottom a remote controlled valve  46 . Pontoon  31  has three equally spaced-apart outreach arms  41 , each having on their outer end a tether catcher  43  defined by two bars  45  and a cone receptor  47 . The cone receptor  47  (see  FIG. 11 ) has an open slot  48  for tether  27  to enter it. Berthing ring  39  has a pipe outfit  49  for receiving compressed air. The inner space of berthing ring  39  is interconnected with the inner space of pontoon  31  through the inner spaces of legs  35  so that air can flow through the legs to the inside of pontoon  31 . On the side of pontoon  31  is located box  51 , to which the power cable  29  is connected. 
         [0093]      FIGS. 12 and 13  illustrate a tether  27  preassembled with a buoy  71  having a quick-disconnecting clutch or connector  72  for ease of releasing it from the tether. Tether  27  has an upper part  73  and a lower part  74 , which are interconnected by a pair of wire ropes  75  and  76 , each shaped as a loop. The upper part  73  includes a centering cone  77  connected to a rod  78  with a chain-type connector  79 , which provides the capability of a universal joint, and to an upper wire rope receiver  80  in the form of half a circle. The lower part  74  includes a lower wire rope receiver  81 , a rod  82  and an anchor  83 , which is connected to a rod  82  through a chain-type connector  79 . 
         [0094]      FIGS. 14 and 15  illustrate an empty GAB  28 . The GAB is a box  84  to which are attached three equally spaced outreach levers  85 . The box  84  has an open top and it includes a floor  89 , walls  91 , a central post  93 , three girders  95 , soil knives  97  located along the GAB perimeter, a valve  98 , a power cable connector  99  and a tether connector  101  on each end of outreached levers  85 . Each tether attachment  101  has a cut-out  102  for insertion of anchor  83  of tether  27 . (See  FIGS. 20-22 ) 
         [0095]      FIGS. 16 and 17  illustrate the empty gravity anchoring base assembled with tethers  27  having buoys  71  and a power cable  29  with a buoy  105  in accordance with one embodiment of the invention.  FIG. 16  is a plan view and  FIG. 17  is a sectional view. They also show a sling arrangement  107  having three ropes  109  assembled with one sheave  111  and attached to girders  95  through ears  113 . 
         [0096]      FIGS. 18 through 22  illustrate the installation of the gravity anchoring base, which is in a form of an open container filled with ballast  87  on the ocean floor. The drawings illustrate a GAB connected with tethers  27  through anchor  83  and a tether connector  101 . The drawings also illustrate the extension of the power cable  29  from the GAB and the penetration of soil knives  97  into the ocean floor. 
         [0097]      FIGS. 23 and 24  illustrate the configuration of a stabilizing platform  115 , which provides the conditions so that at the end of it&#39;s sinking, the GAB lands flat on the ocean floor. It has a pontoon  117 , four legs  119 , a winch platform  121 , a winch  123 , a hoisting line  125  and a hoisting line quick release device  127 . 
       Transporting and Installing the GAB 
       [0098]      FIGS. 25 through 28  illustrate the sequence of positions during the process of transporting and installing an empty GAB in accordance with one embodiment of the invention. 
         [0099]    Position I shows a tug  129  towing an empty GAB  28  that is followed by a stabilizing platform  115 . The stabilizing platform  115  hoisting line  125  is engaged with a sheave  111  of the GAB sling arrangement  107  (shown in  FIG. 17 ). 
         [0100]    Position II ( FIG. 25 ) shows an intermediate position of a free-sinking GAB  28 . At this position the tether buoys  71  have reached the ocean surface and partially pull tethers  27  and wire ropes  75  and  76  out of the GAB, while a buoy  105  pulls power cable  29  partially out of the GAB. The initial limited force acting in the hoisting line  125  causes movement of the stabilizing platform  115  toward the GAB center. 
         [0101]    Position III ( FIG. 26 ) shows further sinking of the GAB under the limited force, which causes winch  123  to pay out hoisting line  125  as the GAB descends. 
         [0102]    Position IV ( FIG. 26 ) shows the moment when the GAB has descended to about 10 meters above the ocean floor and winch  123  stopped paying out hoisting line  125 . The gravity force exerted by the GAB then starts to sink the stabilizing platform. Under this force the slings  109  and sheave  111  (see  FIG. 17 ) are located above the GAB&#39;s center of gravity. This causes the GAB to become horizontally (generally parallel to the ocean floor) oriented even if it was partially inclined during its free-sinking downward movement. 
         [0103]    Position V ( FIG. 27 ) shows that the GAB has reached the ocean floor and the stabilizing platform is almost fully submerged, leaving only winch platform  121  above the ocean surface. 
         [0104]    Position VI ( FIG. 27 ) shows stabilizing platform  115  resubmerged to the ocean surface. This is achieved by gradually releasing hoisting line  125  from winch  123 . 
         [0105]    Position VII ( FIG. 28 ) shows one end of hoisting line  125  detached from quick release device  127  while the remaining hoisting line  125  is wound up by winch  123 . 
         [0106]    Position VIII ( FIG. 28 ) shows the installed GAB with buoys  71  and  105  floating on the ocean surface, tensioned tethers  27  and power cable  29 , and stabilizing platform  115  being towed away by tug  129 . 
         [0107]      FIGS. 29 and 30  illustrate the unloading of ballast material  87  into a GAB  28  installed and resting on the ocean floor.  FIG. 29  is an elevation of a dump barge  131  positioned vertically above GAB  28 .  FIG. 30  is a section taken through the middle of dump barge  131 . 
         [0108]      FIGS. 31 through 36  illustrate a DWP installer  140  used for transporting the assembled DWP from its assembly site close to shore to a position vertically above the GAB on the ocean floor. The DWP installer has two barges  142 , a cross-connecting structure  144 , which includes a support tower  146 , an upper service platform  148 , a lower service platform  150  and two upper and lower engaging clamps  154  and  155  which secure the DWP to the DWP installer  140 . On the barge&#39;s decks there are two workboat stations  152 , two machinery rooms  156  containing, for example, a diesel generator, an air compressor and a hydraulic power pack, which are not shown. The cross-connecting structure  144  includes a pneumatic hose  157 , a winch  158  for handling it and an output valve  159 , to which compressed air is delivered from the compressor in machinery room  156  through the inner space or spaces of the tubular elements of barge connecting structure  144 . 
         [0109]      FIGS. 35 and 36  illustrate engaging clamps  154  and  155  in their open and closed positions. Each of them has three rollers  160 ,  161  and  163 , which in their closed positions engage tower  25 . Rollers  160  and  161  are attached to the arms of two pivoting levers  165  and  166 . Roller  163  is fixed to support tower  146 . Two arm pivoting levers  165  and  166  each have two bars  167  and  169 . Both have a common pivot axis  171 . Bars  167  have on their ends roller  160  or  161 . Bars  167  and  169  are connected by pins  173  to actuators such as a pneumatic or hydraulic cylinder  172 . Cylinder  172  is connected to support tower  146  with a pin  174 . 
       Delivery and Installation of Gravity Anchoring Base at the Destination Point 
       [0110]    The delivery process of gravity anchoring base  28 , which is assembled with tethers  27  and power cable  26 , to the destination point and lowering it to the ocean floor is illustrated by  FIGS. 25 through 28  and is done in the following order:
       Position I ( FIG. 25 ). The gravity anchoring base (GAB)  28  and stabilizing platform  115  attached to it are towed as a pontoon to the designated site by tug  129 .   Position II ( FIG. 25 ). Lowering GAB  28  begins by opening valve  99  ( FIG. 14 ), which allows water to flow into GAB  28 , thereby causing it to sink. As soon as the GAB  28  is fully submerged, it causes a slight tensioning of hoisting line  125  with sling  107  and in this manner pulls the stabilizing platform towards the center of the sinking GAB. The sinking GAB continues to pull hoisting line  125  from winch  123  under limited tension. The sinking of the GAB prompts buoys  71  and  105  to rise upwardly in the water, which pulls tethers  27 , wire ropes  75  and  76  and power cable  29  out of the GAB and upwardly towards the ocean surface.   Position III ( FIG. 26 ). The free-hanging length of hoisting line  125  is chosen to allow GAB  28  to descend downwardly until the stabilizing platform is positioned above the center of gravity of the GAB. At this point the winch  123  starts to pay out hoisting line  125  while maintaining a certain tension force in the line to thereby horizontally level the descending GAB  28 .   Position IV ( FIG. 26 ). The length of the wire ropes  75  and  76  and the height of the buoy  71  are chosen so that tethers  27  are fully pulled out from the GAB when the GAB is positioned about 10 meters above the ocean floor. At this point, winch  123  is stopped and as a result the stabilizing platform  115  begins to sink with the sinking GAB. The created buoyancy force is applied to the GAB through sling  107  and prompts the GAB center of gravity to be located under the hoisting line  125  while the GAB is in a horizontal position even if was initially in an inclined orientation.   Position V ( FIG. 27 ). The GAB has landed flat on the ocean floor and stabilizing platform  115  has been submerged so that only winch platform  121  is located slightly above the ocean surface.   Position VI ( FIG. 27 ). Winch  123  starts to slowly pay out hoisting line  125 , which permits the stabilizing platform to rise from the submerged position until it starts to becomes free-floating again.   Position VII ( FIG. 28 ). The quick-disconnect device  127  ( FIG. 24 ) releases one end of hoisting line  125  so that winch  123  can wind up the entire hoisting line  125 . Position VIII ( FIG. 28 ). Hoisting line  125  has been fully wound up on the hoisting winch  123 , and tug  129  pulls stabilizing platform  115  away from the installed GAB.       
 
         [0118]    The process of loading ballast  87  into the GAB is illustrated by  FIGS. 29 and 30 . The dump barge is located between buoys  71  and opens its bottom, from where ballast gravitationally slides downward toward and into the GAB. To fill up the GAB with sufficient ballast might require unloading several dump barges, in part also because some ballast might spill over onto the sea bottom outside the GAB. 
         [0119]    The process of assembling of the DWP at high-rise crane station  260  is illustrated by  FIGS. 37 through 41  and is performed as follows:
       The floating platform  26  is towed to high-rise crane station  260  close to shore, which has a crane  262 , a pedestal  264  and a pier  266  on a piled foundation  268 . At the moment when floating platform  26  is positioned above underwater supports  270 , the valve  46  (see  FIG. 3 ) opens and entering water will sink floating platform  26  onto underwater supports  270 . When platform  26  reaches the ocean floor, valve  46  is closed.   The tower  25  is installed by crane  262  and is connected to the floating base  26  with flange  34 .   The wind turbine nacelle  24  is installed by crane  262  at the top of tower  25 .   The wind turbine  22  is then attached to the nacelle by crane  262 .       
 
         [0124]    The process of engaging the assembled DWP with DWP installer  140 , lifting it from underwater supports  270 , and floating them together is illustrated by  FIGS. 42 through 46  and is performed as follows:
       The DWP installer  140  moves to the DWP installed at high-rise crane station  260  with its engaging clamps  154  in the open position (see  FIG. 33 ). When guiding roller  163  comes in contact with tower  25 , the two lever arms  165  and  166  are activated and their rollers  160  and  161  come in contact with and engage tower  25  (see  FIG. 34 ).   Pneumatic hose  157  is lifted with winch  158  and connected to floating platform  26  pipe outfit  34  (see  FIGS. 6 ,  34  and  41 ). Through hose  157  and the hollow internal space of floating platform  26  leg  35 , the compressed air is pumped inside floating platform  26 , thereby pushing water out through open valve  46 . This prompts the entire DWP to float upwardly from underwater supports  270  to the surface. In this position, valve  46  is closed. The DWP is submerged sufficiently to only keep it afloat, thus minimizing its towing resistance.   The DWP and DWP installer are coupled together and towed by the tug to the destination site.       
 
         [0128]    The process of anchoring the DWP at the designated site is illustrated by  FIGS. 47 through 53  and is performed as follows:
       The DWP installer  140  stops near the designated site (see  FIG. 47 ), where three buoys  71  and their supporting tethers  27  already float on the ocean surface.   Before engaging tethers  27 , valve  46  is opened so that water can flow inside floating platform  26 . The floating platform  26  will then sink to a position where the level of tether catchers  37  meets the middle level of the rods  77  of tethers  27  (see  FIG. 51 ) and valve  46  is closed to stop further sinking of floating platform  26 .   After reaching the desired depth of submergence, the DWP is towed by tug  129  toward the vertically oriented, tensioned tethers  27 . Engaging the DWP with tethers  27  in place is illustrated by  FIG. 49 .   After all tethers  27  are trapped into their respective tether catchers  37 , the pumping of compressed air into floating platform  26  resumes and water from it flows out through open valve  46 .   When almost all water has been pumped out of floating platform  26 , tethers  27  are pretensioned to the degree that provides sufficient restoration forces for DWP to withstand hurricane winds and resulting wave actions. At this position, valve  46  is closed.   The power cable is detached from buoy  105  and attached to connector  51  on the floating platform  26 .       
 
         [0135]    The final installation of the DWP at the designated site is illustrated by  FIG. 53  and  FIG. 54  and is performed as follows:
       Buoys  71  are released from tethers  27  by activating disconnecting clutch  73 .   Hose  157  is disconnected from floating platform  26 .   Buoys  71  are attached to DWP installer  140 .   The engaging clamps  154  are moved into their open positions.   The DWP installer is then towed back to port, towing buoys  71  behind it.   The DWP is ready to start generating electricity.       
 
         [0142]    One embodiment of the gravity anchoring base (GAB)  28 A is illustrated by  FIGS. 55 and 56 .  FIG. 55  shows GAB  28 A in plan view.  FIG. 56  shows a section view through an empty GAB  28 A floating on the ocean surface. GAB  28 A is a box  184  to which are attached three equally spaced outreach levers  185 . The box  184  has an open top and a floor  189 , upwardly extending base walls  190 , further upwardly protruding extended walls  191  above walls  190  with reinforcement brackets  192 , a central post  193 , three girders  195 , soil knives  197  located along the GAB perimeter, a valve  198 , a power cable connector  199  and a tether connector  201  on the end of each outreach lever  185 . Each tether attachment  201  has a cut-out  202  ( FIG. 63 ) for inserting anchor  183  of tether  27 . 
         [0143]      FIGS. 57 and 58  illustrate GAB  28 A loaded with ballast and assembled with tethers  27  having buoys  71  and a power cable  29  attached to another buoy  105 .  FIG. 57  is a plan view, and  FIG. 58  is a section view of GAB  28 A floating on the ocean surface. The drawings also show a sling arrangement  207  having three ropes  209  assembled with one sheave  211  and attached to girders  195  through ears  213 . 
         [0144]      FIGS. 59 through 63  illustrate the installation of gravity anchoring base  28 A filled with ballast  187  on the ocean floor. GAB  28 A is in engagement with tethers  27  and its anchor  83  through connector  201 . Also shown are an extension of the power cable from the GAB and the penetration of soil knives  97  into the ocean floor. 
         [0145]      FIGS. 64 through 67  illustrate the sequence of positions during the process of transporting and installing the GAB according to another embodiment of the invention. 
         [0146]    Position I ( FIG. 64 ) shows tug  129  towing GAB  28 A that is fully loaded with ballast and assembled with tethers  27  and power cable  29  with the associated stabilizing platform  115  being towed behind. The stabilizing platform  115  hoisting line  125  is engaged with sheave  211  of the GAB  28 A sling arrangement  207 . 
         [0147]    Position II ( FIG. 64 ) shows an intermediate position of the free-sinking GAB  28 A. At this position the tether buoys  71  have reached the ocean surface and partially pull wires ropes  75  and  76 , while buoy  105  pulls power cable  29  partially out of GAB  28 A. The initial limited tension force in the hoisting line  125  moves stabilizing platform  115  toward the GAB  28 A center. 
         [0148]    Position III ( FIG. 65 ) shows a further sinking of GAB  28 A under the limited tension force in the hoisting line applied by winch  123 , which pays out hoisting line  125  as GAB  28 A descends. 
         [0149]    Position IV ( FIG. 65 ) shows that GAB  28 A has descended to about 10 meters above the ocean floor, at which point winch  123  stops paying out hoisting line  125 . The force of gravity of GAB  28 A causes the stabilizing platform to become partially submerged as shown in  FIG. 66 . This force locates sheave  211  and slings  209  above the GAB center of gravity, which orients GAB  28 A horizontally (parallel to the ocean floor) even if it was partially inclined during free-sinking. 
         [0150]    Position V ( FIG. 66 ) shows that the GAB has reached the ocean floor with the stabilizing platform almost fully submerged, leaving only winch platform  121  above the ocean surface. 
         [0151]    Position VI ( FIG. 66 ) shows stabilizing platform  115  returned to the ocean surface, which is achieved by gradually releasing hoisting line  125  from winch  123 . 
         [0152]    Position VII ( FIG. 67 ) shows one end of hoisting line  125  detached from quick release device  127  ( FIG. 24 ) and the process of winding the remaining length of hoisting line  125  onto winch  123 . 
         [0153]    Position VIII ( FIG. 67 ) shows the fully installed GAB with buoys  71  and  105 , tensioned tethers  27  and power cable  29  while stabilizing platform  115  is being towed away by tug  129 .

Summary:
A deepwater windpower plant (DWP) has a tension leg-type floating platform with an evacuable base for adjusting its buoyancy for installation at ocean depths ranging from 40 meters up to 1.5 kilometers and more. The DWP has a typical offshore wind turbine assembled close to shore which is then towed to a desired installation site on the ocean, and held in place by a gravity anchoring base (GAB), to which an evacuable portion or space of the DWP platform is anchored. The GAB has upwardly extending mooring tethers and a power cable which are brought to the ocean surface by attached buoys. The GAB is sunk to the ocean floor at the installation site under controlled conditions so that the GAB lands flat on the ocean floor. As the GAB sinks to the ocean floor, the mooring tethers and power cable are pulled to the surface by their respective buoys. The GAB is loaded with heavy ballast material that can be dropped from barges on the ocean surface into the upwardly open GAB below the barges.