Patent Publication Number: US-2023141340-A1

Title: Floating wind turbine systems and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional of and claims the benefit of U.S. Provisional Application No. 63/276,082, filed Nov. 5, 2021, entitled “SELF-UPENDING FLOATING WIND PLATFORM SYSTEMS AND METHODS,” with attorney docket number 0105198-037PR0. This application is hereby incorporated herein by reference in its entirety and for all purposes. 
     This application is a non-provisional of and claims the benefit of U.S. Provisional Application No. 63/276,086, filed Nov. 5, 2021, entitled “DOWNWIND FLOATING WIND TURBINE AND ITS CONTROL SYSTEM,” with attorney docket number 0105198-038PR0. This application is hereby incorporated herein by reference in its entirety and for all purposes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG.  1   a    is first side view of an example embodiment of a floating wind turbine. 
       FIG.  1   b    is a second side view of the example embodiment of the floating wind turbine of  FIG.  1     a.    
       FIG.  2   a    is first side view of another example embodiment of a floating wind turbine. 
       FIG.  2   b    is a second side view of the example embodiment of the floating wind turbine of  FIG.  1     a.    
       FIG.  3    is a perspective view of a further example embodiment of the hull and tower of a floating wind turbine. 
       FIG.  4    is a side view of a floating wind turbine in a near horizontal or non-vertical configuration. 
       FIG.  5    is a side view of an articulating tug barge with retractable rams in accordance with an embodiment. 
       FIG.  6    is a top perspective view of a rigid arm single point mooring (SPM) buoy system in accordance with an embodiment. 
       FIG.  7    is a perspective view of a nacelle that includes a wind turbine comprising three turbine blades. 
       FIG.  8    illustrates an example embodiment of a self-upending floating wind turbine in an upright (e.g., operational) configuration. 
       FIG.  9    is a close-up view of a lower portion of the floating wind turbine of  FIG.  8   . 
       FIG.  10    illustrates an example embodiment of a self-upending floating wind turbine in a folded (e.g., transport) configuration. 
       FIG.  11    illustrates an example embodiment of a self-upending floating wind platform during an upending operation. 
       FIG.  12    illustrates another example embodiment of a floating wind turbine that has three outer columns. 
       FIG.  13   a    illustrates an example of an upwind floating wind turbine where the central axis Y of the tower is at a heel angle of 0° with a rotor tilt angle of 5°. 
       FIG.  13   b    illustrates the upwind floating wind turbine of  FIG.  13   a    at a heel angle of 10°. 
       FIG.  14   a    illustrates an example of a downwind floating wind turbine where the central axis Y of the tower is at a heel angle of 0° with a rotor tilt angle of 5°. 
       FIG.  14   b    illustrates the downwind floating wind turbine of  FIG.  14   a    at a heel angle of 10°. 
       FIG.  15    illustrates an example of a downwind floating wind turbine with a teetering rotor. 
       FIG.  16    is a block diagram of a wind turbine controller method. 
       FIG.  17   a    illustrates an example embodiment of a downwind floating wind turbine under static conditions with a static tilt angle of 5° and a heel angle of 0° which in this example causes an Annual Energy Production (AEP) reduction of 0.4% compared to a tilt angle of 0°. 
       FIG.  17   b    illustrates an example embodiment of a passive downwind floating wind turbine under rated thrust conditions with a static tilt angle of 5° at a heel angle of 100 that causes a rotor misalignment of −5°, which in this example causes an AEP reduction of 0.4% compared to a rotor misalignment of 0°. 
       FIG.  18   a    illustrates an example embodiment of an upwind floating wind turbine under static conditions with a static tilt angle of 5° and a heel angle of 0°, which in this example causes an AEP reduction of 0.4% compared to a tilt angle of 0°. 
       FIG.  18   b    illustrates an example embodiment of a passive upwind floating wind turbine under rated thrust conditions with a static tilt angle of 5° at a heel angle of 5° that causes a rotor misalignment of 10°, which in this example causes an acceptable AEP reduction of 1.5% compared to a rotor misalignment of 0°. 
       FIG.  18   c    illustrates an example embodiment of a passive upwind floating wind turbine under rated thrust conditions with a static tilt angle of 5° at a heel angle of 100 that causes a rotor misalignment of 15°, which in this example causes an unacceptable AEP reduction of 3.4% compared to a rotor misalignment of 0°. 
    
    
     It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. It also should be noted that the figures are only intended to facilitate the description of the preferred embodiments. The figures do not illustrate every aspect of the described embodiments and do not limit the scope of the present disclosure. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One advantage of deploying some embodiments of floating wind turbines offshore over bottom-fixed wind turbines can be that such floating wind turbines can be assembled and commissioned using onshore cranes and machinery and then towed out to site. However, the access to many ports around the world can be hindered by bridges or other obstacles (e.g., airport regulations) that can constrain the distance a structure rises from the sea level (known as the ‘air draft’). Much of the world&#39;s existing infrastructure has been driven by the global shipping industry, which has standardized vessel classes (e.g., PANAMAX, CHINAMAX, etc.). Air draft allowances can be 50-70 m in some examples. Some wind turbines can have hub heights in excess of 100 m, rendering many large ports or shipyards inaccessible. 
     The present disclosure in one aspect provides systems and methods for accessing these ports by articulating the wind turbine to a horizontal position during transit. Once located in deeper waters, past the obstruction, the turbine can then be upended into an erected configuration. Furthermore, many ports can have draft restrictions that can be as low as 7 m-8 m. By transporting the turbine in a horizontal position, the wind turbine, the draft can be reduced in various embodiments. 
     Another benefit of some examples discussed herein can be to reduce loading on the wind turbine and floating hull structure in extreme wind or fault events. The turbine tower, in some embodiments, can be forced to articulate to a horizontal (or near horizontal) position either by strong winds or by the inclusion of a motor, actuator, or the like. When the turbine is in such a position, the loads on the turbine and the floating hull can be reduced. During a turbine fault event, the forces from the turbine may not be directly transferred to the hull in some examples. Instead, the energy can be dissipated through the viscous damping of the turbine sub-structure in various embodiments. 
     Current wind turbines can be robust on land and on fixed offshore wind platforms but their usage on floating platforms typically requires elaborate control systems or large platforms. These platform control systems are costly to install and difficult to maintain and operate as they require regular maintenance. In some wind turbines, the rotor is tilted upward by 4-8 degrees in order to increase the clearance between the blade tips and tower in operation. This angle relative to the horizontal is referred to as the shaft axis, as the main shaft of the wind turbine is from the generator or gearbox to the hub to transmit torque from the rotor. 
     A wind turbine described in various embodiments of the present disclosure includes a downwind turbine, where the rotor is oriented 4-8 degrees upward from the horizontal in order to increase the clearance between the blade tips and tower in operation. The wind turbine in various examples produces a thrust force in order to produce power from the wind. The thrust force can result in an overturning moment on the platform, which can cause the platform to have a mean heel angle. Here, a heel angle can be the mean pitch angle of the platform, in the direction of the wind. 
     In some examples of a floating wind platform, the target design heel angle is the heel angle of the platform when it is subject to the rated thrust force of the turbine. Generally, the rated thrust force is the maximum mean thrust force on the turbine during operation. The design heel angle of a platform can depend on the restoring force of the platform and mooring system, which can be a function of its center of gravity and buoyancy, its waterplane moment area of inertia and the restoring force due to the mooring system. In general, increasing the platform&#39;s hydrostatic stiffness can result in increased cost or complexity of the system, or both. For instance, for a conventional semi-submersible floating wind platform, the hydrostatic stiffness can be increased by increasing the spacing of the columns, increasing the size of the columns, or both. Wind platforms, without active platform control systems, can target a design heel angle of 4-5 degrees, so that that the maximum rotor misalignment is 8-13 degrees from the horizontal. In various embodiments, the power of the turbine is a function of the swept area of the rotor. The swept area decreases as function of the tilt angle of the turbine as function of the cosine of the tilt angle (gamma). Mathematically, 
         P= 0.5* rho*Cp*A *cos(gamma)* V{circumflex over ( )} 3 
     Where rho is air density, Cp is power coefficient, A is swept area of blades, gamma is tilt angle of turbine, V is velocity of wind. 
     Some embodiments include a floating, downwind fixed-hub turbine that passively operates at a mean heel angle. For example, to produce power thrust is produced, and such thrust can cause the platform to tilt (heel) over in the direction of the wind. By designing a floating wind turbine that has a mean heel angle of 10 degrees, for example, then in various embodiments you have the same rotor misalignment as an upwind turbine that is oriented vertically, such as one on land (+/−5 degrees). By designing a platform that has a mean heel angle of 15 degrees, for example, then you have the same rotor misalignment as an upwind turbine on a floating platform with a heel angle of 5 degrees. 
     Some embodiments include a floating, downwind teetered turbine that passively operates at a mean heel angle. By designing such floating wind turbine that has a mean heel angle of 15 deg, for example, in various embodiments you then can have less rotor misalignment than an upwind turbine that is oriented vertically (e.g., 0 deg vs+5 degrees). 
     Some wind platforms, with active platform control systems, can target a design heel angle of 5-8 degrees, so that the tower can remain vertical and the maximum rotor misalignment can be maintained at 4-8 degrees. Some wind turbines can have larger active control systems which can cause an increased tilt angle, resulting in 0 degrees rotor misalignment. However, a need exists for an improved floating-specific wind turbine and method for its control in an effort to overcome the aforementioned obstacles and deficiencies of some examples of wind turbine systems. 
     In various embodiments, a benefit of a tilting, downwind floating wind turbine operating at a tilt angle can be that the wake generated by the floating wind turbine can be driven down and have a reduced effect on the downstream floating wind turbine where a plurality of floating wind turbines are disposed in an array, group or farm. In various embodiments, this can allow more floating wind turbines to be packed into in a given area, which can be a large concern for floating wind turbine operators and other stakeholders (fishing, e.g.). 
     Below are described example systems and methods, that in accordance with some embodiments, can be used to design lighter, more inexpensive floating wind turbines including towers and supporting hull platforms. For example, various embodiments can include a floating wind turbine comprising one or more of: 
     (1) A one-, two- or three-bladed wind turbine (e.g., horizontal-axis: upwind or downwind rotor, or vertical-axis). 
     (2) A platform comprising of multiple, buoyant assemblies (e.g.,  4  such assemblies). For example, in some embodiments the assemblies can comprise four-bar linkages using members connected by pin bearings or other suitable element. The assemblies in some examples contain a main buoyant member (e.g., a column). In one embodiment, each of the assemblies are connected to a central column. 
     (3) A moveable truss member for each assembly, such that each assembly can be reconfigured depending on the position of said truss member. In various examples, when the truss member is connected the final position of the assembly is determined. In one embodiment, the final position of the assembly is such that the column is oriented vertically. 
     One embodiment can be designed so that platform is as shown in  FIG.  8   . Such a design can comprise, consist essentially of, or consists of one or more of the following elements, with one or more of such elements being specifically absent in some embodiments. 
     (a) Multiple buoyant columns that can have a variable amount of mass (such as partially or fully filled ballast tanks). 
     (b) Multiple, independent assemblies, such that the horizontal members (e.g., the upper and lower truss members in  FIG.  8   ) form a four-bar linkage with the central column and a buoyant structure (e.g., an outer column). Each of the structural members can connected by pin bearings in some examples. 
     (c) A diagonal cross-beam for one or more pinned structure. 
     (d) A mechanism to allow the end of the cross-beam to transit across the central column/tower. 
     One embodiment comprises, consists essentially of, or consists of a floating downwind turbine with a turbine control system that can be used to optimize the tilt angle of the platform. 
     Another embodiment comprises, consists essentially of, or consists of a floating downwind turbine with a teetered hub, and a turbine control system that can be used to optimize the teeter angle of the rotor and the tilt angle of the platform. 
     In some such embodiments, no active control system exists on the platform, as the platform can be allowed to passively pitch or tilt in the direction of the wind. However, in various examples, the turbine is able to produce full power, as the rotor plane can remain aligned with the horizontal. 
     Turning to  FIGS.  1   a ,  1   b ,  2   a  and  2   b   , two example embodiments  100 A,  100 B of a floating wind turbine  100  are illustrated in  FIGS.  1   a  and  1   b    and in  FIGS.  2   a  and  2   b    respectively. The floating wind turbine  100  is shown comprising a tower body  110  having a tower shaft  112  that extends along an axis Y. The tower body  110  further comprises a tower base  114  at a bottom end of the tower shaft  112 , with a keel plate  116  disposed at a terminal bottom end of the tower body  110 . One or more fins  118  can extend between the keel plate  116  and tower base  114  to reinforce a coupling between the keel plate  116  and tower base  114  and/or provide dampening for rotation, movement or pitch of the tower  110 . 
     A nacelle  170  can be disposed at a top end of the tower body  110 . The nacelle  170  can be configured in various suitable ways and comprise various suitable elements, including a wind turbine  700  comprising a hub  172  with a plurality of blades  174  extending from the hub  172  as shown in the example of  FIG.  7   . Further embodiments can include any suitable plurality of blades  174 , including 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 16, 24, 36, 48, or the like. In some embodiments, a wind turbine  700  can operate in a horizontal-axis with and upwind or downwind rotor or can operate in a vertical-axis. 
     Various embodiments can include any suitable turbine elements, so the example of  FIG.  7    should not be construed as being limiting. Additionally, while various example embodiments herein relate to wind turbines, it should be clear that further embodiments can be employed for various suitable purposes including a light house, bridge, communications array, weather station, observation station, weapon mount, or the like. 
     Returning to  FIGS.  1   a ,  1   b ,  2   a  and  2   b   , the floating wind turbine  100  is further shown comprising a hull  130  that includes a pair of base elements  132  and a pair of support architectures  134 , which are spaced apart and coupled together via one or more bars  136 . As shown in the examples of  FIGS.  1   b  and  2   b   , the pair of base elements  132 A,  132 B, the pair of support architectures  134 A,  134 B and the one or more bars can define a hull cavity  138 . 
     A pitch plate  140  can extend between the support architectures  134 A,  134 B and be rotatably coupled to the hull  130  via pitch shaft  142 , which allows the pitch plate  140  to rotate about an axis X. The tower shaft  112  and/or tower base  114  can extend through and be coupled to the pitch plate  140 , which can allow the tower  110  to rotate about the axis X via the pitch plate  140 . In various embodiments, axis Y of the tower  110  can be perpendicular to and/or coincident with the axis X. As shown in the examples of  FIGS.  1   a ,  1   b ,  2   a  and  2   b    (and also  FIG.  3    discussed in more detail herein), such rotation of the tower  110  via the pitch plate  140  can allow the tower base  114  and/or keel plate  116  to swing or pitch within the hull cavity  138  to various configurations as discussed herein. 
     Additionally, the tower  110  can be coupled to the pitch plate  140  via a yaw bearing  144 , which can allow the tower shaft  112  and/or tower base  114  to rotate about axis Y of the tower  110 . Providing for rotation of the tower  110  about the axis Y can be desirable in some embodiments to position the nacelle  170  in a desired or optimal direction, such as at an angle where a wind turbine  700  associated with the tower  110  produces a maximum amount of energy, produces a maximum amount of energy without compromising structural integrity of the blades  174 , to protect the blades  174  from wind damage, and the like. Additionally, in some embodiments, the nacelle  170  can be rotatably coupled to the top of the tower  110  in addition to or as an alternative to a yaw bearing  144 . In some embodiments (e.g., downwind turbine embodiments), there may be or may not be a yaw motor or actuator that actively drives yaw rotation of the tower  110  about central axis Y. In some examples, wind turbine weathervanes can be downwind and the yaw bearing  144  can allow passive rotation of the tower  110  relative to the hull  130 . In another embodiment, a conical bearing can allow free yaw motion of the tower  110 , while the hull  130  can be split (e.g., as shown in  FIGS.  1   a ,  1   b ,  2   a  and  2   b   ). 
     In an upwind turbine embodiment, the yaw bearing  144  can replace the need for a yaw controller in the nacelle  170 . In one such embodiment, a motor can drive the yaw bearing  144  so that the nacelle  170  faces into the wind. In this configuration, in some examples, it can be desirable for the axis X of the pitch shaft  142  to be perpendicular to the incident wind direction to minimize off-axis loading on bearings or other elements of the floating wind turbine  100 . 
     The floating wind turbine  100  can be configured to float and be disposed on the surface  101  of a body of water  102  with a portion of the floating wind turbine  100  being disposed within the body of water  102  and a portion of the floating wind turbine  100  being disposed above  103  the body of water  102 . For example, in the embodiments  100 A,  100 B of  FIGS.  1   a ,  1   b ,  2   a  and  2   b   , the nacelle  170 , tower shaft  112 , pitch plate  140 , pitch shaft  142 , yaw bearing  144 , and axis X are shown being disposed above  103  the surface  101  of the body of water  102 . A portion of the tower base  114  and support architectures  134  are shown as being partially above  103  and within the body of water  102 . The base elements  132  of the hull  130  and keel plate  116  of the tower  110  are shown being below the surface  101  of the body of water  102 . The floating wind turbine  100  can be disposed in any suitable body of water or fluid, including an ocean, lake, river, man-made body of water, or the like. 
     Further embodiments can be configured for various elements of the floating wind turbine  100  to be positioned in various suitable locations relative to the surface  101  of a body of water  102  that the floating wind turbine  100  is floating on, so the examples of  FIGS.  1   a ,  1   b ,  2   a  and  2   b    should not be construed to be limiting. Additionally, as discussed herein, the buoyancy of the floating wind turbine  100  can be modified in various embodiments, which may change which elements are above  103  or within the body of water  102  at a given time. In some embodiments, it can be desirable to have elements such as at least a portion of the tower base  114  and the keel plate  116  disposed within the body of water  102  to provide resistance to or dampening of rotation of the tower  110 . 
     For example, in some embodiments, one or more fins  118  can have a planar face that is parallel to the axis of rotation X, which can provide a surface area that provides resistance to or dampening of rotation of the tower  110  based on friction between such a surface area and water  102  in which the fins  118  of the tower rotate  110 . Additionally, in some embodiments, it can be desirable to have elements such as the pitch plate  140 , pitch shaft  142 , and/or yaw bearing  144  disposed above the surface  101  of the water  102  to prevent or reduce water intrusion, corrosion, or the like, of such elements. 
     In various embodiments, it can be desirable to fix or substantially fix the floating wind turbine  100  in a location on the surface  101  of the water  102 . For example, it can be desirable to prevent the floating wind turbine  100  from drifting away or preventing the floating wind turbine  100  from contacting undesirable objects such as another floating wind turbine  100  (e.g., in a wind farm), a reef, a beach, rocks, a cliff, or the like. In various embodiments, including the examples of  FIGS.  1   a ,  1   b ,  2   a  and  2   b   , one or more mooring lines  150  can be coupled to the floating wind turbine  100  to fix or substantially fix the floating wind turbine  100  in place. For example, such one or more mooring lines  150  can coupled to various suitable locations on the hull  130  such as the support architecture  134  (see  FIGS.  1   a  and  1   b   ) base element(s)  132  (see  FIGS.  2   a  and  2   b   ), or the like. Mooring lines  150  in some examples can be coupled to weights or anchors at an ocean floor, lakebed, riverbed or the like. 
     In some embodiments, the floating wind turbine  100  can be connected to a turret system or a single point mooring buoy, such as those on Floating Production, Storage and Offloading units (FPSOs). An example of such a mooring buoy system  600  is shown in  FIG.  6   . In some embodiments, such a turret system can either be driven to rotate upwind or be passively allowed to weathervane downwind. 
     In various embodiments, the floating wind turbine  100  can generate electrical power (e.g., via wind turning a wind turbine  700  as illustrated in the example of  FIG.  7   ) and generated electrical power can be transmitted to various locations via one or more electrical cables  155 , which in various embodiments can extend from the bottom of the keel plate  116  as shown in  FIGS.  1   a  and  1   b   . For example, in some embodiments, the electrical power generated by a floating wind turbine  100  can be transmitted to land, a battery station, another floating wind turbine  100 , a water-based electrical power consumer (e.g., a floating home, ship, station, or the like). Additionally, in some embodiments, one or more electrical cables  155  can be configured to provide electrical power to a floating wind turbine  100 , which can be received from land, a battery station, another floating wind turbine  100 , or the like. 
     Turning to  FIG.  3   , a portion of further embodiment  100 C of a floating wind turbine  100  is illustrated, which includes a tower  110  that is rotatably coupled to a hull  130  via a pitch shaft  142 . In this example embodiment  100 C, the hull  130  can comprise one or more floater modules  334  that surround the tower  110  and one or more connectors  336  extending between floater modules  334 . In some examples, the connectors  336  can comprised hinged connections that stiffen the hull  130 , but allow for the tower  110  upending as discussed herein. 
     A yaw unit  344  can be disposed at a top end of the hull  130 , with a pair of pitch units disposed on the yaw unit  344  that hold the pitch shaft  142  and can allow the tower  110  to rotate via the pitch shaft  142 . The floater modules  334 , connectors  336  and yaw unit  344  can define a hull cavity  338  through which the tower  110  can extend and pitch or rotate via the pitch shaft  142 . The yaw unit  344  can be configured to rotate to allow the tower  110  to rotate about a central axis (e.g., axis Y as shown in  FIGS.  1   a ,  1   b ,  2   a  and  2   b   ). The hull  130  can further comprise one or more fairleads  350  that allow mooring lines  150  to couple with and secure the floating wind turbine  100  as discussed herein. 
     In various embodiments, the base of the yaw unit  344  can comprise a floating body that is designed in a “C” shape that can allow for 90 degrees of pitch rotation for the tower  110  of the floating wind turbine  100 . In some embodiments, connectors  336  can be hinged and can allow for the tower  110  to articulate when the connectors  336  are opened, and when the connectors  336  are closed, can provide load transfer throughout the structure of the hull  130 . 
     In some embodiments, pitch bearings can be disposed on the tower  110  and the pitch shaft  142  can comprise a retractable ram that allows the tower  110  to disconnect from the floating hull  130 . In various examples, such an assembly can be used with an articulating tug barge  500 , as shown in  FIG.  5   . In another embodiment, the tower  110  can be connected to the hull  130  via a hinged joint. In order to up-end the turbine in some examples, internal cables can be tensioned. In one such an embodiment, the floating hull  130  can be in a more structurally efficient toroidal shape. 
     As discussed herein, in various embodiments a pitch shaft  142 , or the like, can allow the tower  110  of the floating wind turbine  100  to assume a vertical or near-vertical configuration (e.g., for power-producing) as shown in the  FIGS.  1   a ,  1   b ,  2   a  and  2   b    or horizontal or near-horizontal configuration (e.g., for installation, transit, load mitigation) as shown in  FIG.  4   . For example,  FIG.  4    illustrates an embodiments  100 A of a floating wind turbine  100  where the central axis Y of the tower  110  is in a near-horizontal configuration and disposed along axis Y 1 , with the tower  110  being configured to pitching about pitch shaft  142  an angle θ to assume a vertical or near-vertical configuration where the central axis Y of the tower  110  is disposed along axis Y 2 . In various embodiments, configuration or axis Y 2  can be vertical or near-vertical relative to gravity, the plane W of the surface  101  of the body of water  102  that the floating wind turbine  100  is floating on, a main horizontal axis of the floating wind turbine  100 , or the like. 
     In some embodiments, a floating wind turbine  100  can be configured to pitch or rotate any suitable angle θ from a vertical or near-vertical configuration (e.g., from axis Y 2 ), including positive and/or negative 45°, 50°, 55° 60°, 65°, 70°, 75° 80°, 85°, 90°, 95° 100°, 105°, 110°, 115°, 120°, 125°, 130°, 135°, or the like. For example, some embodiments can be configured to rotate in only one direction from a vertical or near-vertical configuration or can be configured to rotate or pitch both directions from a vertical or near-vertical configuration. In some embodiments, a maximum rotation in both directions can be the same or can be different (e.g., any of the example values cited above). In some embodiments, the tower  110  can be configured to pitch or rotate and amount that prevents the tower  110 , nacelle  170  or a wind turbine of the nacelle  170  from extending into the water  102  or engaging the surface  101  of the water  102 ; however, some embodiments can be configured for the tower  110 , nacelle  170  and/or a wind turbine of the nacelle  170  to extend into the water  102  or engage the surface  101  of the water  102 . 
     In various embodiments, rotation or pitch of the tower  110  can be configured based on the ability of the hull  130  to rotate, pitch or move on the surface  101  of the water  102  due to waves, wind, storms, or the like. In some examples, the orientation of the tower  110  can be actively controlled relative to the hull  130  such that the tower  110  can be maintained at a vertical or near-vertical configuration even if the hull  130  rotates, pitches or moves on the surface  101  of the water  102 . For example, the orientation of the tower  110  and/or hull  130  can be monitored and determined relative to a desired vertical or near-vertical configuration and a motor, actuator, or the like can actively change to the orientation of the tower  110  toward the desired vertical or near-vertical configuration despite rotation, pitch or movement of the hull  130  on the surface  101  of the water  102 . 
     One embodiment of a method of operating a floating wind turbine  100  can include determining an orientation of the tower  110  and/or hull  130 ; determining whether the tower  110  is in an orientation that is not a vertical or near-vertical configuration or within a margin of error of a vertical or near-vertical configuration based at least in part on the determined orientation of the tower  110  and/or hull  130 ; and actuating the tower  110  (e.g., about the pitch shaft  142 ) to move the tower  110  toward the desired vertical or near-vertical configuration or within a margin of error of the desired vertical or near-vertical configuration. In some embodiments, such a method can be performed in real time, near real-time, or every 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 10.0 seconds, or the like. 
     A floating wind turbine  100  where the tower  110  is configured to assume a horizontal, near horizontal or non-vertical configuration can be desirable for operations such as installation of the floating wind turbine  100 , assembly of the floating wind turbine  100 , transit of the floating wind turbine  100 , maintenance of the floating wind turbine  100 , load mitigation of the floating wind turbine  100 , or the like. For example,  FIG.  4    illustrates an example embodiment, where tow lines  410  are coupled to the hull  130  of the floating wind turbine  100 , which can be used to move the floating wind turbine  100 . 
     Additionally, in some examples, where a determination is made that winds or other weather conditions could cause damage to elements the floating wind turbine  100  (e.g., blades  174 , tower shaft  112 , or the like), the tower  110  can be automatically or manually lowered to a horizontal, near horizontal or non-vertical configuration to protect the floating wind turbine  100  from damage. For example, a method of operation of a floating wind turbine  100  can include determining that wind or weather conditions are above or are predicted to be above a safety threshold, and if so, lowering the tower  110  to a horizontal, near horizontal or non-vertical configuration to protect the floating wind turbine  100 . Such a determination can be made by one or more weather, wind or other sensors at the floating wind turbine  100 , at another floating wind turbine  100 , by a weather station, by an onshore device, or the like. In some embodiments, a computing device of the floating wind turbine  100  can make such a determination based on local and/or remote data and can automatically lower the tower  110  without user input, alert a user to the danger and receive instructions to lower the tower  110 , or the like. In some examples, lowering of the tower  110  can be performed by a motor or other actuator and in some examples, the tower  110  changed from being in a locked configuration to an unlocked configuration, which can allow the tower  110  to fall or lower under its own weight. 
     In various embodiments, portions of the floating wind turbine  100  can be configured to have or contain a variable amount of mass or ballast. In some embodiments, a portion of the tower base  114  or portion of the tower  100  below the pitch shaft  142  can be configured for mass or ballast to be added or removed therefrom. For example, in various embodiments, the tower base  114  and/or keel plate  116  can comprise a cavity in which a ballast material (e.g., sand, weights, water or the like) can be introduced or removed from. In further embodiments, ballast or mass (e.g., weights, sandbags, water bladders, or the like) can be coupled to or removed from the tower base  114  and/or keel plate  116 . 
     Such an addition of such ballast material can lower the center of gravity of the tower  110  in various examples such as from a first higher center of gravity CG 1  to a lower center of gravity CG 2  as shown in  FIG.  3   . In various embodiments, addition of such ballast material can lower the center of gravity of the tower  110  from being above the pitch shaft  142  to below the pitch shaft  142  (see e.g.,  FIG.  3   ), which can cause or make it easier for the tower  110  to rise from a horizontal, near horizontal, or non-vertical configuration (see e.g.,  FIG.  4   ) to a vertical or substantially vertical configuration (see e.g.,  FIGS.  1   a ,  1   b ,  2   a , and  2   b   ). In further embodiments, adding ballast can lower the center of gravity of the tower  110  from first position above the pitch shaft  142  to a second position above the pitch shaft  142  or can lower the center of gravity of the tower  110  from first position below the pitch shaft  142  to a second position below the pitch shaft  142 . 
     A single floating wind turbine  100  or an array of a plurality of floating wind turbines  100  can be manufactured, erected or positioned in various suitable ways with various portions occurring on land and/or a body of water  102 . For example, in some embodiments, during fabrication and/or assembly of the hull  130  and tower  110 , the tower  110  can be either in a vertical position or in a horizontal position. In one embodiment, the nacelle  170 , wind turbine  700  and/or blades  174  can be mated with the tower  110  in a horizontal position or substantially horizontal position. Such an embodiment in some examples can use smaller, more readily available cranes to lift the tower  110  or sections thereof, along with the nacelle  170  and/or blades  174  of the wind turbine  700 . In some examples, before, during, or just after installation of the nacelle  170 , wind turbine  700 , blades  174 , or the like, ballast (e.g., solid or liquid ballast) can be added to the tower base  114  to balance out the weight of such elements. In one embodiment, the solid ballast can take the form of batteries. In some embodiments, ballast can be added incrementally as additional elements are installed on the tower  110 , nacelle  170  or the like. 
     In one embodiment, the amount of ballast added can be calculated so that the vertical center of gravity of the tower  110  (including a nacelle  170  wind turbine  700 , and the like) is located at or substantially the pitch axis X (see e.g.,  FIGS.  1   b  and  2   b   ). In such an embodiment (in the absence of friction), there may be no resultant overturning moment from the weight of the turbine  700 , tower  110 , or the like, on the hull  130 . Such an embodiment may reduce the holding force required to keep the floating wind turbine  100  in a horizontal, near horizontal position or non-vertical position and may also reduce the force required to rotate the tower  110  relative to the hull  130  (e.g., to or from a vertical or near vertical position). 
     In some embodiments, once the tower  110  has been integrated onto the hull  130  on or near land (e.g., via the pitch shaft  142 , in various examples the assembled floating wind turbine  100  can be towed from a port to a location on a body of water  102  where the floating wind turbine  100  will be installed. Many ports have draft or air draft restrictions as previously described, which can be the distance from the surface of the water  101  to a highest point on a vessel, cargo on a vessel or cargo being towed by a vessel. Draft restrictions can be less than or equal to 7 m, 8 m, 9 m, 10 m, 12 m or the like. Air draft restrictions can be less than or equal to 35 m, 40 m, 45 m, 50 m, 55 m, 60 m, 70 m, 75 m, 80 m, 85 m, 90 m, or the like. Once these obstructions or restrictions have been cleared, the platform can be reconfigured to have a larger draft, or a larger air draft or both a larger draft and a larger air draft. 
     In one embodiment, the tower base  114  and/or keel plate  116  can be filled with sand, gravel, dirt or the like, away from the port (e.g., once any port obstructions and/or restrictions have been cleared), since such a material may be a readily available, low-cost solid ballast option. Furthermore, on return to the port or land for a maintenance operation where lowering the tower  110  may be necessary or desirable, such a ballast material can simply be dropped to the seafloor, if necessary, without harming the environment, which can allow the tower  110  to be lowered or more easily lowered. After the maintenance operation and when the floating wind turbine  100  is being re-installed or installed in a new location on a body of water  102 , new ballast can again be added to the tower  110  as discussed herein to raise the tower  110  or to make raising the tower  110  easier (e.g., tower pitch motors may be incapable of raising the tower without the addition of a sufficient amount of ballast. 
     In various embodiments, once the additional ballast has been added, the vertical center of gravity of the tower  110  can be dropped below the pitch axis X (see e.g.,  FIG.  3   ). This can result in the wind turbine tower  110  being up-ended and in a vertical or near-vertical position. The floating wind turbine  100  can then be towed (e.g., via tow lines  410 ) to an offshore wind farm site, so it can be installed (e.g., connected to a mooring and/or cabling system comprising mooring lines  150 , electrical cables  155 , or the like). In another embodiment, the floating wind turbine  100  can be towed with the tower  110  in a horizontal, near horizontal or non-vertical position (e.g., as shown in  FIG.  4   ) so that the drag on the tower  110  and associated elements can be reduced. In such an embodiment, the turbine upending can occur at the wind farm site (e.g., via adding ballast, a pitch motor, crane, or the like). 
     In various examples, after the hull  130  is connected to the cable and/or mooring systems, the turbine  700  can be commissioned. In one embodiment with an upwind horizontal-axis wind turbine, the horizontal center of gravity of the tower  110  is located towards the hub  172  of the nacelle  170 . A static overturning moment can result and the turbine  700  can be tilted into the wind. An optimal static tilt angle into the wind in some examples may be in the range of 5-15 degrees, 7-13 degrees, 9-11 degrees, 4-17 degrees, 3-19 degrees, 2-20 degrees, and the like. For certain low wind speeds, the tilt of the turbine  700  can result in increased power production since the tilt angle of the turbine  700  can offset the tilt angle of the nacelle  170  in various embodiments. In higher wind speeds, in some examples the turbine  700  can tilt out of the direction of the wind. 
     In some embodiments, fins  118  can added to the base  114  and or keel plate  116  of the tower  110  which can increase the viscous damping effects of the tilting tower  110 . In the case of an emergency shutdown, or other event where there is a dramatic change in the thrust force, the floating wind turbine  100  may exhibit large dynamic tilting motion. The fins  118  can, in some examples, dissipate the energy from the dynamic tilt motion into the surrounding fluid  102  thereby reducing the loads transferred to the hull  130 . 
     As previously described, if the floating wind turbine  100  is to return to port for maintenance, decommissioning, or the like, ballast in and/or on the keel plate  116  and/or tower base  114  can be removed. This can decrease the draft of the floating wind turbine  100 , allowing it to enter a port with draft restrictions. Furthermore, the tower  110  can be moved into a horizontal position in various examples without the need for large tugboats when the vertical center of gravity aligns with or is close to the pitch axis X (e.g., based on addition or removal of ballast). 
     Accordingly, a method of installing at least one floating wind turbine  100  can include one or more of the follow steps, which can start with assembling at least a portion of a tower  110  and hull  130  floating wind turbine  100  and then coupling the tower  110  to the hull  130  (e.g., via a pitch shaft  142 ). Some or all of such assembly can occur on land including at a port or shoreline, or away from a port or shoreline. For example, the tower  110  and hull  130  (or portions thereof) can be transported to a port or shoreline as separate pieces, with the tower  110  and hull  130  (or portions thereof) being assembled to form a full or substantially complete floating wind turbine  100 . 
     Such a full or substantially complete floating wind turbine  100  can have the tower  110  in a horizontal or near horizontal configuration while being assembled and/or during a portion of a journey from a port or shoreline to a desired location where the floating wind turbine  100  is to be installed. When possible or desirable, the floating wind turbine  100  can be converted from the tower  110  being in the horizontal or near horizontal configuration to an erected configuration where the tower  110  is in a vertical or near vertical configuration. 
     For example, as discussed herein, in some embodiments erecting the tower  110  can include adding ballast into and/or on a portion of the tower  110  to change the center of gravity of the tower  110 , which can cause the tower  110  to self-erect or may make it possible for a pitch actuator, crane, or the like to erect the tower  110 . In various embodiments, such a method or portions thereof can be performed in reverse when the floating wind turbine  100  needs to be decommissioned, repaired, lowered or moved to prevent damage that may be caused by wind or weather, or the like. 
     Turning to  FIGS.  8 - 11    another embodiment  100 D of a floating wind turbine  100  is illustrated that comprises a tower  110  coupled to a hull assembly  830  that includes with a central column  840  and a plurality of outer columns  850  that are coupled to the central column  840  via one or more respective upper truss members  860 , one or more respective lower truss members  870  and one or more respective cross-beams  880 . Note that elements such as a nacelle, rotor and turbine are not illustrated in these figures for purposes of simplicity. 
     The tower  110  can comprise a tower shaft  112  having a central axis Y with the central column  840  being disposed at a bottom end of the tower shaft  112  with the central column  840  sharing the central axis Y. As shown in the examples of  FIGS.  8  and  9   , the floating wind turbine  100  can comprise four outer columns  850 A,  850 B,  850 C,  850 D that are spaced apart from the central column  840  at an equal distance via the upper and lower truss members  860 ,  870  and cross-beams  880 . In various embodiments, the outer columns  850  can have separate respective central axes that are parallel to the central axis Y of the tower  110  and central column  840 . In various embodiments, the outer columns  850  and/or central column  840  can comprise ballast tanks configured to hold fluid such as air and/or water as discussed herein. 
     Additionally, the four outer columns  850 A,  850 B,  850 C,  850 D can be equally spaced about the central column  840  with respective adjacent outer columns  850  being  900  from each other about the central axis Y. For example, the first and third outer columns  850 A,  850 C can be disposed in a first common plane that is coincident with the central axis Y. The second and fourth outer columns  850 B,  850 D can be disposed in a second common plane that is coincident with the central axis Y and perpendicular to the first common plane of the first and third outer columns  850 A,  850 C. 
     Also, in various embodiments, the four outer columns  850 A,  850 B,  850 C,  850 D can be of equal length such that bottoms of four outer columns  850 A,  850 B,  850 C,  850 D are disposed within a third common plane and tops of the four outer columns  850 A,  850 B,  850 C,  850 D are disposed within a fourth common plane that is parallel to the third common plane and that is perpendicular to the central axis Y. In some embodiments, (e.g., a 10-15 MW turbine  700 ) the floating wind turbine can have a rotor diameter of 180-230 m. In various examples, the tower  110  can have a height of 100-150 m. In various embodiments, the columns  840 ,  850  can have a diameter of 8-12 m. In some examples, the outer columns  850  can be 40-50 m from the central column  840  (e.g., the upper and/or lower truss members  860 ,  870  can be 40-50 m long). In some examples the columns can have a height of 30-40 m. In various embodiments the columns  840 ,  850  can have an operating draft of 15-25 m. 
     As shown in the example embodiment  100 D of the floating wind turbine  100  of  FIGS.  8 - 11   , each outer column  850  can be coupled to the central column  840  via a pair of upper truss members  860 . For example, as shown in  FIG.  9   , the first outer column  850 A can be coupled to the central column  840  via first and second upper truss members  860 A 1 ,  860 A 2 . In various embodiments, the pairs of upper truss members  860  can extend from a top end of respective outer columns  850  at an angle with the distance between the pair of upper truss members  860  increasing toward the central column  840 . For example, such an angle can be 2°, 4°, 6°, 8°, 10°, 12°, 14°, 16°, 18°, 20°, 22°, 24°, 26°, or the like, including a range between such values. In various embodiments the upper truss members  860  can be configured to extend toward the central column  840  in a common plane that is perpendicular to the central axis Y. 
     In various embodiments, the upper truss members  860  can be cylindrical bars as shown in the example embodiment  100 D of the floating wind turbine  100  of  FIGS.  8 - 11   , but in further embodiments, the upper truss members  860  can be any suitable form such as an I-beam, box truss, or the like. Additionally, in various embodiments, there can be any suitable number of upper truss members  860  associated with each outer column  850  such as  1 ,  2 ,  3 ,  4 ,  5 ,  10 ,  25 ,  100  and the like. Also, various structures can be associated with the upper truss members  860  such as plates, walkways, and the like. 
     As shown in the example embodiment  100 D of the floating wind turbine  100  of  FIGS.  8 - 11   , each outer column  850  can be coupled to the central column  840  via a lower truss member  870 . For example, as shown in  FIG.  9   , the first outer column  850 A can be coupled to the central column  840  via a first lower truss member  870 A, the second outer column  850 B can be coupled to the central column  840  via a second lower truss member  870 B, the third outer column  850 C can be coupled to the central column  840  via a third lower truss member  870 C and the fourth outer column  850 D can be coupled to the central column  840  via a fourth lower truss member  870 D. 
     In various embodiments, the lower truss members  870  can comprise various suitable structures such as a plate and/or one or more bars (see e.g.,  FIGS.  9  and  10    showing a lower truss plate  872  covering a pair of lower truss bars  874 ). In some embodiments, where a pair of lower truss bars  874  extend from a bottom end of respective outer columns  850 , such lower truss bars can extend at an angle with the distance between the pair of upper truss members  860  increasing toward the central column  840 . For example, such an angle can be 2°, 4°, 6°, 8°, 10°, 12°, 14°, 16°, 18°, 20°, 22°, 24°, 26°, or the like, including a range between such values. In some examples, such an angle can be the same as upper truss members  860 . In various embodiments, the lower truss members  870  can be configured to extend toward the central column  840  in a common plane that is perpendicular to the central axis Y, and in some examples such a common plane can be parallel to a common plane of upper truss members  860 . 
     In various embodiments, the lower truss bars  874  can be cylindrical bars, but in further embodiments, such lower truss bars  874  or the lower truss members  870  can be any suitable form such as an I-beam, box truss, or the like. Additionally, in various embodiments, there can be any suitable number of lower truss bars  874  or the lower truss members  870  associated with each outer column  850  such as  1 ,  2 ,  3 ,  4 ,  5 ,  10 ,  25 ,  100  and the like. 
     As shown in the example embodiment  100 D of the floating wind turbine  100  of  FIGS.  8 - 11   , cross-beams  880  can extend between respective outer columns  850  and the central column  840  from a bottom end of the respective outer columns  850  to respective locations at a top end of the central column  840 . However, in further embodiments, cross-beams  880  can extend between respective outer columns  850  and the central column  840  from a top end of the respective outer columns  850  to respective locations at a bottom end of the central column  840 . 
     For example, as shown in  FIG.  9   , the first outer column  850 A can be coupled to the central column  840  via a first cross-beam  880 A, the second outer column  850 B can be coupled to the central column  840  via a second cross-beam  880 B, the third outer column  850 C can be coupled to the central column  840  via a third cross-beam  880 C and the fourth outer column  850 D can be coupled to the central column  840  via a fourth cross-beam  880 D. 
     Additionally, the four cross-beams  880 A,  880 B,  880 C,  880 D can be equally spaced about the central column  840  with respective adjacent cross-beams  880  being  900  from each other about the central axis Y. For example, the first and third cross-beams  880 A,  880 C can be disposed in a first common plane that is coincident with the central axis Y. The second and fourth cross-beams  880 B,  880 D can be disposed in a second common plane that is coincident with the central axis Y and perpendicular to the first common plane of the first and third cross-beams  880 A,  880 C. 
     In various embodiments, the cross-beams  880  can be cylindrical bars, but in further embodiments, such cross-beams  880  can be any suitable form such as an I-beam, box truss, or the like. Additionally, in various embodiments, there can be any suitable number of cross-beams  880  associated with each outer column  850  such as  1 ,  2 ,  3 ,  4 ,  5 ,  10 ,  25 ,  100  and the like. 
     In various embodiments, the floating wind turbine  100  can be operable to change configurations between an erected configuration as shown in  FIGS.  8  and  9    and a collapsed configuration as shown in  FIG.  10   . For example, the outer columns  850  can be individually movably coupled to the central column  840  such that the outer columns  850  can be folded upward and/or downward relative to the tower body  110  so that the outer columns  850  are retracted closer to the central axis Y to reduce the maximum dimensions of the hull assembly  830 , which can be desirable for transportation of the floating wind turbine  100  in some examples as discussed herein. 
     For example, as shown in  FIG.  10   , a first pair of adjacent outer columns  850 B,  850 C can be configured to fold downward relative to tower body  110  so that the outer columns  850  are retracted closer to the central axis Y such that this pair of outer columns  850 B,  850 C is disposed fully or at least partially below the bottom of the central column  840 . A second pair of adjacent outer columns  850 A,  850 D can be configured to fold upward relative to tower body  110  so that the outer columns  850  are retracted closer to the central axis Y such that this pair of outer columns  850 A,  850 D is disposed fully or at least partially above the top of the central column  840  about the tower shaft  112  of the tower body  110 . 
     In various embodiments, such as shown in the example of  FIG.  10   , a respective main axis of the outer columns  850  can remain parallel to the central axis Y in the collapsed configuration of  FIG.  10    and/or during the process of the outer columns  850  folding upward or downward from the erected configuration to the collapsed configuration. Such a folding in some embodiments can be based on one or more rotatable couplings between the outer columns  850  and the central column  840  and/or one or more translational rotational couplings between the outer columns  850  and the central column  840 . 
     For example, respective ends of the upper and lower truss members  860 ,  870  can be rotatably coupled to the respective outer columns  850  and to the central column  840 , which can allow the outer columns  850  to rotatably fold up and/or down. Additionally, ends of the cross-beams  880  that are rotatably coupled to the central column  840  can be configured to translate up and/or down the length of the central column  840  and/or tower shaft  112  of the tower body  110  and opposing ends of the cross-beams  880  that are coupled to the respective outer columns  850  can be rotatably coupled to the respective outer columns  850  such that the cross-beams  880  can fold toward the central column  840  and/or tower shaft  112  when the outer columns  850  rotatably fold up and/or down. 
     For example, referring to  FIGS.  9  and  10   , the first pair of adjacent outer columns  850 B,  850 C can be configured to rotatably fold downward relative to tower body  110  with opposing ends of the cross-beams  880 B,  880 C coupled to the central column  840  translating downward along the face of the central column  840  via respective cross-beam lower tracks  820  to allow the cross-beams  880 B,  880 C to fold toward the central column  840 , to the collapsed configuration of  FIG.  10   , based on rotatable couplings at the ends of the second and third cross-beams  880 B,  880 C. (The lower track  820 B of the second cross-beam  880 B is shown in  FIG.  9   ). Accordingly, the first pair of adjacent outer columns  850 B,  850 C are folded closer to the central axis Y such that this pair of outer columns  850 B,  850 C is disposed fully or at least partially below the bottom of the central column  840 . 
     The second pair of adjacent outer columns  850 A,  850 D can be configured to rotatably fold upward relative to tower body  110  with the opposing ends of the cross-beams  880 A,  880 D coupled to the central column  840  translating upward along the face of the tower shaft  112  of the tower body  110  via respective cross-beam upper tracks  810 A,  810 B to allow the cross-beams  880 A,  880 D to fold toward the tower body  110 , to the collapsed configuration of  FIG.  10   , based on rotatable couplings at the ends of the first and fourth cross-beams  880 A,  880 D. Accordingly, the second pair of adjacent outer columns  850 A,  850 D are folded upward closer to the central axis Y such that this second pair of outer columns  850 A,  850 D is disposed fully or at least partially above the top of the central column  840  proximate to and about the tower shaft  112  of the tower body  110 . 
     Folding of the outer columns  850  from the erected configuration to the collapsed configuration (and vice versa) can be performed in various suitable ways. For example, in some embodiments, the translational couplings of the cross-beams  880  in the cross-beam upper and lower tracks  810 ,  820  can be based on buoyancy of the central column  840  and/or outer columns  850  as discussed herein and/or can be motorized (e.g., fluidic, electric, or fuel-powered), which can allow the up and down movement in the cross-beam upper and lower tracks  810 ,  820  that causes motorized actuation of the outer columns  850  up and/or down. Accordingly, in various embodiments, configuring the floating wind turbine  100  between the erected/extended and collapsed configurations can be motorized based on passive and/or powered translation of the cross-beams  880  in the cross-beam upper and lower tracks  810 ,  820 . 
     In further embodiments, translation of the cross-beams  880  can be mechanical such as by a user rotating a crank or otherwise applying external mechanical force. In further embodiments, other portions of the floating wind turbine  100  can be configured to cause actuation of the outer columns  850 , such as cables, winches, motors on a rotatable coupling, or the like. In some embodiments, actuation of the outer columns  850  can be performed by an external apparatus such as a crane, or the like. In some embodiments, actuation of the outer columns  850  can be performed based on forces of gravity or buoyancy such as based on ballast and/or air being introduced into or removed from the central column  840  and/or one or more outer columns  850 . 
     In some embodiments, such as shown in  FIGS.  8 - 11   , the outer columns  850  are only configured to fold up or down from the erected configuration to the collapsed configuration. For example, a given outer column  850  may only be associated with a cross-beam upper track  810  or a cross-beam lower track  820 , which can make the given outer column  850  only operable to fold up or down from the erected configuration to the collapsed configuration. In the example of  FIGS.  8 - 11   , the floating wind turbine  100  only has two cross-beam upper tracks  810  and two cross-beam lower tracks  820 , which makes it such that the first pair of outer columns  850 B,  850 C are only configured to fold downward and the second pair of outer columns  850 A,  850 D are only configured to fold upward. 
     However, in some embodiments one or more of the outer columns  850  can be configured for bi-directional folding and can, for example, have both upper and lower cross-beam tracks  810 ,  820 . Also, in some embodiments, each of the outer columns  850  can be separately actuated or can be configured to always be actuated as a group. For example, the first pair of outer columns  850 B,  850 C can be configured to be actuated together as a group; the second pair of outer columns  850 A,  850 D can be configured to be actuated together as a group; all four outer columns  850 A,  850 B,  850 C,  850 D can be configured to be actuated together as a group, or the like. 
     In various embodiments, a floating wind turbine  100  can be configured in pieces for assembly and/or disassembly, which can be desirable for transportation as discussed herein. For example, the upper truss members  860 , lower truss members  870 , and/or cross-beams  880  can have couplings (e.g., via pins, bolts, or the like) that allows such elements to be easily coupled and de-coupled with the central column  840  and/or outer columns  850  such that the upper truss members  860 , lower truss members  870 , and/or cross-beams  880  can be separable from the central column  840  and/or outer columns  850 , which can allow the outer columns  850  and such elements to be separated from each other and the central column  840 . In some embodiments, the central column  840  can be separated from the tower  110 . Additionally, in various embodiments, elements such as the nacelle  170 , blades  174 , rotor and the like can be configured to be disassembled from each other and/or the tower  100 . For example, in various embodiments, one or more of such couplings can be non-permanent couplings instead of a weld or other integral coupling. 
     A single floating wind turbine  100  or an array of a plurality of floating wind turbines  100  can be manufactured, erected or positioned in various suitable ways with various portions occurring on land and/or a body of water  102 . For example, in some embodiments, elements such as a tower  110 , nacelle  170 , blades  174 , central column  840 , outer columns  850 , upper truss members  860 , lower truss members  870 , and/or cross-beams  880  can be manufactured separately and transported in a disassembled, partially assembled, or fully assembled form from a manufacturing location to a port, dock, or other location at a body of water  102 . 
     For example, using  FIGS.  8 - 11    as an illustration, in some embodiments the hull assembly  830  can be fully assembled (and may or may not be coupled with a tower  110 ) and transported to a body of water  102  in a collapsed configuration (see e.g.,  FIG.  10   ). In some examples, the central column  840 , outer columns  850 , upper truss members  860 , lower truss members  870 , and/or cross-beams  880  can be manufactured separately and transported to a body of water in a disassembled set and assembled at the body of water  102 . In various embodiments, it can be necessary for the tower  110  to be present in a collapsed configuration so that outer columns  850  folding up can engage the tower  110  instead of over-folding or undesirably moving in the collapsed configuration. 
     In some embodiments, with the tower  110  integrated onto the hull assembly  830  on or near land, in various examples the assembled floating wind turbine  100  can be towed from a port to a location on a body of water  102  where the floating wind turbine  100  will be installed. Many ports have draft or air draft restrictions as previously described, which can be the distance from the surface of the water  101  to a highest point on a vessel, cargo on a vessel or cargo being towed by a vessel. Draft restrictions can be less than or equal to 7 m, 8 m, 9 m, 10 m, 12 m or the like. Air draft restrictions can be less than or equal to 35 m, 40 m, 45 m, 50 m, 55 m, 60 m, 70 m, 75 m, 80 m, 85 m, 90 m, or the like. Once these obstructions or restrictions have been cleared, the floating wind turbine  100  can be reconfigured to have a larger draft, or a larger air draft or both a larger draft and a larger air draft. For example, the floating wind turbine  100  can be configured from a collapsed configuration to an erected configuration, where the collapsed configuration is compliant or compatible with obstructions or restrictions (e.g., draft restrictions), but where the erected configuration would not be compliant or compatible with one or both of obstructions and restrictions. 
     Using  FIGS.  8 - 11    as an example, in various embodiments, the process to upend a floating wind turbine  100  can include one or more fore floats (e.g., first and fourth outer columns  850 A,  850 D) and/or the central column  840  being filled with ballast (e.g., water from a body of water  102  that the floating wind turbine  100  is disposed in) so that the one or more fore floats (e.g., first and fourth outer columns  850 A,  850 D) are sunk within the body of water  102  and reach an extended configuration (e.g., as shown in  FIG.  11   ). In doing so, the cross-beams  880  can have transited along their respective upper tracks  810  and can be (e.g., temporarily) locked into place. 
     In various embodiments, sinking of the floating wind turbine  100  into the body of water  102  below the water line (e.g., based on filling one or more columns  840 ,  850  with ballast) can cause one or more aft floats (e.g., second and third columns  850 B,  850 C) to move from a collapsed configuration (e.g., as shown in  FIG.  10   ) to an extended configuration (e.g., as shown in  FIG.  11   ). For example, where the floating wind turbine  100  has been sunk to a sufficient level within the body of water  102 , the buoyancy of the one or more aft tanks (e.g., second and third columns  850 B,  850 C) can cause cross-beams  880  of such aft tanks to transit across the lower tracks  820  and reach an extend position, as depicted in  FIG.  11   . 
     The cross-beams  880  can be (e.g., temporarily) locked into place, and the floating wind turbine  100  can be upended in various embodiments to an erected configuration by (e.g., partially) evacuating the fore float(s) (e.g., first and fourth columns  850 A,  850 D) and/or central column  840  while partially filling the aft float(s) (e.g., second and third columns  850 B,  850 C). The change in ballast can produce a large uprighting moment, which can cause the floating wind turbine  100  and turbine  700  to upright from a configuration as shown in  FIG.  11    and reach an operational erected configuration such as shown in  FIG.  8   . In some embodiments, a cross-beam  880  can be locked into place by inserting a pin into the cross-beam  880  which prevents the cross-beam from translating. Such a pin insertion in some examples can be triggered remotely such as by an operator on a support vessel, or the like. 
     In some embodiments, outer columns  850  can be extended one-by-one. Additionally, in some embodiments, the floating wind turbine  100  can rotate (e.g., about the main axis Y) based on ballast being introduced and/or removed from columns  850 , which may be desirable for making it easier for the outer columns  850  can be extended one-by-one sequentially. For example, a first collapsed downward-facing outer column  850  can be extended based on ballast being added to this first collapsed outer column  850  to cause it to sink and become extended. Changing the buoyancy of one or more of the outer columns  850  can cause the floating wind turbine  100  to rotate and cause a second collapsed outer column  850  to be oriented downward such that the second collapsed outer column  850  can sink downward and extend. Further collapsed columns  850  can be extended sequentially in a similar manner. 
     In some embodiments, in such an operational erected configuration, the lower truss members  870  can be fully submerged within a body of water  102  below the surface  101  of the water  102 ; the central and outer columns  840 ,  850  can be partially submerged in the water  102 , with a bottom portion submerged within the body of water  102  below the surface  101  and a top portion out of the water  102  above the surface  101 ; the upper truss member  860  can be above the surface  101  of the water  102 ; and the tower  110  can be above the surface  101  of the water  102 . In various embodiments, the level of the central and outer columns  840 ,  850  above/below the surface  101  of the water  102  can be changed based on an amount of ballast and/or air in ballast tanks of the central and outer columns  840 ,  850 . 
     In some embodiments, movement of some or all of the outer columns  850  from a collapsed configuration (e.g.,  FIG.  10   ) to an extended configuration (e.g.,  FIG.  11   ) can be completely based on buoyancy and/or gravity. For example, motorized or other active powered actuation of the upper truss members  860 , lower truss members  870 , and/or cross-beams  880  can be absent. In other words, in some embodiments, changing the configuration of the floating wind turbine  100  between a collapsed configuration and an extended configuration can be substantially or completely based on ballast or air being introduced or removed from the central column  840  and/or outer columns  850 . 
     In one embodiment, ballast pumps are located on the floating wind turbine  100  and can be remotely operated to enact the filling of the ballast tanks (e.g., of the central column  840  and/or outer columns  850 ). In another embodiment, the ballast tanks (e.g., of the central column  840  and/or outer columns  850 ) are filled by opening a valve on the column via a remotely operated vehicle (ROV) or diver. In another embodiment, the ballast tanks are connected via a hose to ballast pumps onboard a support vessel such as a boat, ship or the like. In such an embodiment such ballast tanks can be filled and evacuated using the same pump run in reverse. 
     In various examples, after the floating wind turbine  100  is erected and connected to electrical cable systems  155  and/or mooring systems  150 , the turbine  700  can be commissioned for attachment to the floating wind turbine  100 ; however, in some embodiments the turbine  700  can be installed onshore or in transit on water to an installation location and can be present when the floating wind turbine  100  is erected. For example, in some embodiments an upending maneuver can be performed with the nacelle  170  and blades  174  pre-installed or an upending maneuver can be performed without the nacelle  170  and blades  174  being pre-installed with such elements being added on after the upending maneuver. Some embodiments can include a nacelle  170  and blades  174  that can be pre-assembled horizontally. 
     As previously described, if the floating wind turbine  100  is to return to port for maintenance, decommissioning, or the like, such an installation or erection method can be reversed in part or in whole. This can decrease the draft of the floating wind turbine  100 , allowing it to enter a port with draft restrictions or to access shallow water. Furthermore, the tower  110  can be moved into a horizontal position in various examples without the need for large tugboats when the vertical center of gravity aligns with or is close to the tower axis X. In some embodiments, the floating wind turbine  100  can be loaded on to a barge (e.g., submersible barge), for transport to or from shore. 
     Accordingly, a method of installing at least one floating wind turbine  100  can include one or more of the follow steps, which can start with assembling portions of the tower  110  and hull assembly  830  and then coupling the tower  110  to the hull assembly  830 . Some or all of such assembly can occur on land including at a port or shoreline, or away from a port or shoreline. For example, the tower  110  and hull assembly  830  (or portions thereof) can be transported to a port or shoreline as separate pieces, with the tower  110  and hull assembly  830  (or portions thereof) being assembled to form a full or substantially complete floating wind turbine  100 . In one example embodiment, each of the tower  110  and hull assembly  830  can be assembled in parallel. For example, an outer column  850  can be attached to a lower and upper truss member  860 ,  870 , as well as a cross-beam  880  during assembly of the tower  110 . 
     In one embodiment, a lower section of the tower  110  and a tower base are mated. The central tower  110  can be lifted off the ground with temporary supports such that fore floats (e.g., first and fourth outer columns  850 A,  850 D) can be connected underneath. For example, the two fore floats can be connected to the central column  840  (e.g., via a pin bearing). The two aft floats (e.g., second and third outer columns  850 B,  850 C) can be connected to the central column  840  (e.g., via a pin bearing). Remaining sections of the tower, such as the nacelle, rotor, and the like can be attached to the tower shaft  112 . 
     Such a full or substantially complete floating wind turbine  100  can have the tower  110  in a horizontal or near horizontal configuration while being assembled and/or during a portion of a journey from a port or shoreline to a desired location where the floating wind turbine  100  is to be installed. In one embodiment, the turbine can be mated with the tower base in the horizontal position. Such an embodiment can use smaller, more readily available cranes to lift the tower sections, nacelle and blades (e.g., a gantry crane). Before, during, or just after the turbine installation, solid ballast can be added to the central or outer columns  840 ,  850  to lower the center of gravity of the structure. In one embodiment, the solid ballast can take the form of batteries. 
     In another embodiment, the platform is towed with the turbine in the horizontal position so that the drag on the turbine can be reduced. In one such an embodiment, the turbine upending can occur at the wind farm site. For example, when possible or desirable, the floating wind turbine  100  can be converted from the tower  110  being in the horizontal or near horizontal configuration to an erected configuration where the tower  110  is in a vertical or near vertical configuration, so it can be connected to a mooring and cabling system. 
     In some embodiments, once a turbine has been integrated onto tower  110 , in various examples the floating wind turbine  100  can be towed from port. Many ports have draft or air draft restrictions as previously described. In one embodiment, the fully assembled floating wind turbine  100  can be transported on a barge. In another embodiment, the fully assembled floating wind turbine  100  can be skidded directly into the water (e.g., in a collapsed form such as shown in  FIG.  10   ) and towed via tow lines  410 . In another embodiment, the floating wind turbine  100  can be assembled in a dry dock, which can be filled with water after the assembly process is completed. Then, the assembled floating wind turbine  100  can be towed out of the port and to an offshore location (e.g., wind farm site), which in some examples can be via standard tug boats The floating wind turbine  100  can be transported in some examples by such vehicles as self-propelled modular transports, which are commonly used in port facilities. In this manner, the fully assembled floating wind turbine  100  can be loaded on to a barge for offshore transport. 
     In various embodiments, once the port obstructions, restrictions or shallow water have been cleared, the floating wind turbine  100  can be upended. For example, the floating wind turbine  100  can be towed out of port via tow lines  410  in the collapsed configuration as shown in  FIG.  10    with ballast (e.g., water) absent or substantially absent from central or outer columns  840 ,  850 . 
     The floating wind turbine  100  can be upended from a collapsed configuration (e.g., as shown in  FIG.  10   ) by a first set of one or more columns  850  (e.g., first and fourth outer columns  850 A,  850 D) and/or the central column  840  being filled with ballast (e.g., water) to change the buoyancy of the first set of one or more columns  850  so that the first set of one or more columns  850  sink within the body of water  102  and reach an extended configuration (e.g., as shown in  FIG.  11   ). In various embodiments such a configuration change can include the cross-beams  880  of the first set of one or more columns  850  translating along their respective upper tracks  810 . 
     In various embodiments, such as shown in the example of  FIG.  11    extension of the first set of one or more columns  850  can include the first set of one or more columns  850  going from being partially submerged in the water  102  to being fully submerged within the water  102  and can include the central column  840  going from being partially submerged in the water  102  to being fully submerged within the water  102 . 
     In various embodiments, a second set of one or more columns  850  (e.g., second and third columns  850 B,  850 C) can move from a collapsed configuration (e.g., as shown in  FIG.  10   ) to an extended configuration (e.g., as shown in  FIG.  11   ). For example, the buoyancy of the second set of one or more columns  850  can cause cross-beams  880  of the second set of one or more columns  850  to translate along the lower tracks  820  and reach an extend position, as depicted in  FIG.  11   . In some embodiments, the second set of one or more columns  850  can remain floating on the surface  101  of the body of water  102  with a portion of the second set of one or more columns  850  disposed in the water  102  and a portion of the second set of one or more columns  850  remaining out of the water throughout the transition of the second set of one or more columns  850  from the collapsed configuration to the extended configuration. 
     In some embodiments, extension of the first set of one or more columns  850  and extension of the second set of one or more columns  850  can occur simultaneously or can occur sequentially in any suitable order. In some embodiments, sinking of the first set of one or more columns  850  and central column  840  into the body of water  102  can cause extension of the second set of one or more columns  850  based on the second set of one or more columns  850  remaining floating on the surface  101  of the body of water  102  based on the buoyancy of the second set of one or more columns  850 . 
     The floating wind turbine  100  can be upended in various embodiments to an erected configuration by removing ballast from the first set of one or more columns  850  and/or central column  840 . Additionally, in some examples, the second set of one or more columns  850  can be at least partially filled with ballast during such an upending. Such a change in ballast of the first and/or second sets of one or more columns  850  can generate an uprighting moment, which can cause the floating wind turbine  100  to upright from a configuration as shown in  FIG.  11    and reach an operational erected configuration such as shown in  FIG.  8   . 
     In some embodiments, the first and second sets of one or more columns  850  can be filled with the same amount of ballast to generate equal buoyancy of the first and second sets of one or more columns  850  or the ballast of the first and second sets of one or more columns  850  can otherwise be configured to generate equal buoyancy of the first and second sets of one or more columns  850  (e.g., different amounts of ballast for columns having different weight). 
     While various examples of a floating wind turbine  100  can include four outer columns  850 A,  850 B,  850 C,  850 D, further embodiments can include any suitable number of columns  850  as discussed herein, including 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 16, 25, 100, and the like. For example,  FIG.  12    illustrates an example embodiment of a floating wind turbine  100  having three outer columns  850 A,  850 B,  850 C. 
     In this example, the three outer columns  850 A,  850 B,  850 C are shown equally spaced about the central column  840  with respective adjacent outer columns  850  being  1200  from each other about the central axis Y, which can define three planes of symmetry that are coincident with the central axis Y. It should be clear that descriptions of embodiments having four outer columns  850  can be equally applicable to embodiments having other numbers of outer columns  850  (e.g., three) in accordance with some examples. 
     Additionally, an embodiment  100 D of a floating wind turbine  100  having three outer columns  850 A,  850 B,  850 C such as shown in  FIG.  12    (or other number of outer columns  850 ) can fold or otherwise assume a collapsed, expanded and/or erected configuration as discussed in other example embodiments herein. Using  FIG.  12    as an example, one or two columns  850  of the three outer columns  850 A,  850 B,  850 C can be configured to fold upward (e.g., like first and fourth columns  850 A,  850 D shown in  FIG.  10   ) and one or two other columns  850  of the three outer columns  850 A,  850 B,  850 C can be configured to fold downward (e.g., like second and third columns  850 B,  850 C shown in  FIG.  10   ). Similarly, introduction and/or removal of ballast from respective columns  850  can cause fore and aft sets of one or more columns  850  to extend and/or contract and to cause the floating wind turbine  100  to be upended or lowered as discussed herein. Outer columns  850  can be configured to move via tracks  810 ,  820  as discussed herein or such tracks  810 ,  820  can be absent. In some such embodiments where tracks  810 ,  820  are absent, the stiffness of the upper and/or lower truss members  860 ,  870  can keep the column  850  aligned during the unfolding process. In some examples, the end of a cross-beam  880  can be attached to a winch line that guides the cross-beam  880  into a final position in a controlled manner. Once the cross-beam  880  reaches a final position, a pin can be inserted into the cross-beam  880  to lock the cross-beam  880  into place. 
     Also, as shown in the example of  FIG.  12   , the floating wind turbine  100  can comprise various access elements  890 , which can include one or more ladders  892 , one or more outer column platforms  894 , one or more walkways  896  and one or more central column platform  898 , and the like. For example, when the floating wind turbine  100  is floating in a body of water  102 , a boat or ship can dock with the floating wind turbine  100  and a human operator can climb a ladder  892  on one of the outer columns  850  to the outer column platform  894 , across the walkway  896  and to the central column platform  898 . In various examples, the tower  110  can house elements of the floating wind turbine  100  that can be accessed by the human operator for purposes of maintenance, repair, or the like. Additionally, in various examples, there can be a ladder within the tower body  112 , which allows an operator to climb up to the nacelle  170  for purposes of maintenance, repair, or the like, of elements of the turbine  700 . 
     Additionally, while various embodiments can include a plurality of outer columns  850  radiating from a central column  840 , further embodiments can include columns  840 ,  850  in any suitable configuration with a central column  840  being absent in some embodiments. For example, a set of outer columns  850  can be disposed in a triangular, quadrilateral, pentagonal, hexagonal, heptagonal, octagonal arrangement, or the like, with a central column being absent. Additionally, while various embodiments illustrated herein include a tower  110  extending from a central column  840 , in further embodiments, one or more towers  110  can extend from one or more outer columns  850 , including in some embodiments where a central column  840  is present. 
     One embodiment comprises, consists essentially of, or consists of a downwind and/or upwind floating wind turbine  100  with a turbine control system that can be used to optimize the tilt angle of the floating wind turbine  100  or portions thereof. Another embodiment comprises, consists essentially of, or consists of a downwind and/or upwind floating wind turbine  100  with a teetered hub, and a turbine control system that can be used to optimize the teeter angle of the rotor and the tilt angle of the floating wind turbine  100  or portions thereof. 
     In some such embodiments, no active control system exists on the floating wind platform, as the floating wind turbine  100  can be allowed to passively pitch in the direction of the wind. However, in various examples, the wind turbine  700  is able to produce full power, as a rotor plane of the floating wind turbine  100  can remain aligned with the horizontal. 
     Turning to  FIGS.  13   a ,  13   b ,  14   a ,  14   b    and  15 , various embodiments of a floating wind turbine  100  are illustrated that comprise a tower  110  disposed on a hull assembly  830  with a wind turbine  700  disposed on the top of the tower body  112  of the tower  110 . The wind turbine  700  comprises a nacelle  170  with a hub  172  and a plurality of blades  174  extending from the hub  172 . The  110  tower can have a central axis Y. The hub  172  and blades  174  can rotate about a rotor axis R, with the blades  174  having a blade plane B that is perpendicular to the rotor axis R. 
     In various embodiments, the hub  172  and corresponding rotor axis R can have a rotor tilt angle defined by a difference between the rotor axis R and a horizontal axis H (i.e., an axis perpendicular to gravity) when the central axis Y of the tower  110  is completely vertical (i.e., the central axis Y is parallel with an axis of gravity). For example,  FIG.  13   a    illustrates an example where the central axis Y of the tower  110  is at a heel angle of 0° (i.e., the central axis Y is parallel with an axis of gravity), and the horizontal axis H is perpendicular to the central axis Y of the tower  110 . The rotor axis R in this example is 5° from the horizontal axis H, which defines the rotor tilt angle of the example of  FIG.  13   a    as being 5°. In some embodiments, rotor tilt angle can be defined based on a difference in angle between the central axis Y and blade plane B. 
     Turning to  FIG.  13   b   , the floating wind turbine  100  of  FIG.  13   a    is shown having a heel angle of 10° (i.e., the central axis Y of the tower  110  is 10° from true vertical as shown in  FIG.  13   a   ). Here, the heel angle of 10° plus the rotor tilt angle of 5° means that the rotor axis R is 15° from the horizontal axis H in this example. In various embodiments, having the rotor axis R parallel with the horizontal axis H (e.g., 0° misalignment) can be considered to be an optimal configuration for a wind turbine  700  (e.g., because such a configuration can maximize the swept area by the blades  174 ); accordingly, in such embodiments, the rotor axis R being 15° from the horizontal axis H can be considered a  150  misalignment of the rotor axis R from an optimal configuration. 
     However, in further embodiments, any suitable axis can be defined as an optimal axis for the rotor axis R, which can be based on wind direction, wind angle, or the like. In some examples, such an optimal axis for the rotor axis R can change based on changing environmental conditions (e.g., changing wind direction, wind angle, or the like) or can remain the same even if environmental conditions change. 
     In various embodiments, such misalignment of the rotor axis R can be desirable or acceptable for various reasons, but may come at the cost of reduced energy production; for example, a reduction in Annual Energy Production (AEP), or the like. In some embodiments, a reduction in AEP can be considered acceptable or can be unacceptable. For example, in some embodiments, a reduction in AEP of less than or equal to 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or the like can be considered acceptable. in some embodiments, a reduction in AEP of greater than or equal to 1%, 1.5%, 2%, 2.5%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 4%, 4.5%, 5% or the like can be considered unacceptable. Accordingly, various embodiments of a floating wind turbine  100  can be configured to operate at mean heel angle with a rotor tilt angle that generates a rotor misalignment that creates a reduced energy production compared to optimal (e.g., reduced AEP) that is considered acceptable or that is not considered unacceptable. 
     A floating wind turbine  100  of some various embodiments includes a downwind turbine  700 , where the rotor is oriented 4° to 8° upward from the horizontal H in order to increase the clearance between the blade tips and tower shaft  112  in operation. The floating wind turbine  100  in various examples produces a thrust force in order to produce power from the wind. The thrust force can result in an overturning moment of floating wind turbine  100 , which can cause the floating wind turbine  100  to have a mean heel angle. In some examples, a mean heel angle can be the mean pitch angle of the floating wind turbine  100 , in the direction of the wind. In some embodiments, the mean heel angle can be 0°, 1°, 2°, 3°, 4°, 5°, 6°, 7° 8°, 9° 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, or the like, or a range between such example values. 
     In some examples of a floating wind turbine  100 , the target design heel angle is the heel angle of the platform when it is subject to the rated thrust force of the turbine. Rated thrust force can be the maximum mean thrust force on the turbine during operation. The design heel angle of a platform can depend on the platform&#39;s hydrostatic stiffness, which can be a function of its center of gravity and buoyancy, its waterplane moment area of inertia and the restoring force due to a mooring system. In some examples, increasing the floating wind turbine  100  hydrostatic stiffness can result in increased cost or complexity of the system, or both. For instance, for some semi-submersible floating wind turbines  100 , the hydrostatic stiffness can be increased by increasing the spacing of the columns  840 ,  850 , increasing the size of the columns  840 ,  850 , or both. 
     Floating wind turbines  100  of some embodiments without active control systems, can target a design heel angle of 4-5 degrees, so that that the maximum rotor misalignment is 8-13 degrees from the horizontal axis H. Some floating wind turbines  100 , with active platform control systems, can target a design heel angle of 5-8 degrees, so that that the tower  110  can remain vertical and the maximum rotor misalignment can be maintained at 4-8 degrees. Some wind turbines can have larger active control systems which can cause an increased tilt angle, resulting in 0 degrees rotor misalignment. In some embodiments, a floating wind turbine can be configured to operate with a rotor misalignment of −20°, −19°, −18°, −17°, −16°, −15°, −14°, −13°, −12°, −11°−10°, −9, −8°, −7°, −6°, −5°, −4°, −3°, −2°, −1°, 0°, 1°, 2°, 3° 4°, 5°, 6°, 7° 8°, 9° 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, or the like, or a range between such example values. 
     In various embodiments, a benefit of a tilting floating wind turbine  100  operating at a tilt angle can be that a wake generated by the floating wind turbine  100  can be driven into the body of water  102  and can have a reduced effect on the downstream floating wind turbine  100  where a plurality of floating wind turbines  100  are disposed in an array, group or farm. In various embodiments, this can allow more floating wind turbines  100  to be grouped into in a given area, which can be desirable for operators of floating wind turbines  100 . 
     In various embodiments, the design heel angle of the floating wind turbine  100  can be increased to 10−15 degrees, which in some examples can allow for a much smaller floating wind turbine  100  and/or less complex mooring system, or the like. In some embodiments, if the rotor tilt angle is 5 degrees above the horizontal axis H, the floating wind turbine  100  can heel under the influence of the rated thrust on the floating wind turbine  100 . If the design heel angle of the turbine is 10 degrees, in various embodiments the rotor misalignment is only 5 degrees below the horizontal, which can be the same magnitude of misalignment as a conventional wind turbine with 0 degrees heel angle (e.g., oriented vertically). 
     While various examples can include a rotor tilt angle of 5°, various other rotor tilt angles can be defined in further embodiments including −10°, −9°−8°−7°−6°, −5°, −4°, −3°, −2°, −1°, 0°, 1°, 2°, 3° 4°, 5°, 6°, 7° 8°, 9° 10°, or the like, including a range between such example values. In some embodiments, the rotor tilt angle can be defined by various portions of a wind turbine  700  such as the physical position of the nacelle  170 , hub  172 , and the like. In some embodiments, the rotor tilt angle can be fixed based on a physical configuration of the wind turbine  700  or can be changeable in some embodiments (e.g., motorized tilting of the nacelle  170  to change the rotor tilt angle). 
     In various embodiments, the floating wind turbine  100  can be configured to have or can be positioned to heel angle or operating angle (e.g., angle of the central axis Y relative to true vertical) based on weighting or balancing of the hull assembly  830  (e.g., based on amount of ballast in columns  840 ,  850 ), weights of various portions of the hull assembly  830 , tower  110  and/or wind turbine  700 , anticipated or actual wind speed and/or direction, and the like. For example, in various embodiments, wind force on the floating wind turbine  100  can cause the floating wind turbine to be angled. Additionally, in various examples, wind, waves or tidal action of a body of water  102  can cause the floating wind turbine  100  to rock or otherwise move within the body of water  102 . Accordingly, the floating wind turbine  100  can be configured to operate within a range of heel angles. For example, in some embodiments, the floating wind turbine  100  can be configured to be angled −20°, −19°, −18°, −17°, −16°, −15°, −14°, −13°, −12°, −11°, −10°, −9°, −8°, −7°, −6°, 5°−4°−3°, −2°−1°, 0°, 1°, 2°, 3° 4° 5° 6°, 7° 8°, 9° 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, or the like, or a range between such example values. 
     Additionally, a floating wind turbine  100  can be configured for upwind and/or downwind operation. An example of upwind operation is illustrated in  FIGS.  13   a  and  13   b    where the direction of wind is toward the front face of the hub  172  and blades  174  and then moving over the nacelle  170 . In contrast,  FIGS.  14   a ,  14   b    and  15  illustrate examples of downwind operation where the direction of wind is toward the rear face of the hub  172  and blades  174  with wind directed toward the rear of the nacelle  170 . 
     For example,  FIGS.  14   a  and  14   b    illustrate an example where the rotor plane R is 5° away from the perpendicular to the shaft axis Y to define a rotor tilt angle of 5°. As shown in  FIG.  14   b   , where the floating wind turbine becomes angled 10° (e.g., based on wind, balance, or the like), this can cause the rotor axis R to be −5° from the horizontal axis H. In another embodiment the design heel angle can be 20 degrees, with 10 degrees of misalignment between the rotor plane R and the shaft axis Y. 
     In some examples, a downwind, teetering floating wind turbine  100  of various embodiments can afford the platform designer with even a larger design heel angle, while still maintaining 0 degrees of rotor misalignment. In some examples of a teetered floating wind turbine  100 , the rotor axis R can be misaligned from an angle that is perpendicular to the main shaft axis Y. For example,  FIG.  15    illustrates such an example. The platform can have a 15° design heel angle as shown in this example, but has 0 degrees of rotor misalignment with the incident wind due to the additive effects of the downwind turbine and a teetered hub  1500  that allows for movement of the hub relative to the rotor axis R. In this way, in various examples the cost and complexity of the platform and mooring system can be decreased even further from using a fixed hub, downwind wind turbine. 
     In various embodiments, a floating wind turbine  100  can have various suitable control systems such as blade pitch controllers, nacelle yaw control, generator torque control, and the like. In various embodiments, a floating wind turbine  100  can comprise a computing system comprising a processor and memory that stores instructions, that when executed by the processor, cause various methods to be performed. In various embodiments, such a computing system can obtain data from various suitable sensors such as one or more accelerometer, temperature sensor, water sensor, humidity sensor, magnetic field sensor, gyroscope, pressure sensor, torque sensor, light sensor, rain gauge, wind sensor, current sensor, depth sensor, GPS unit and the like. For example, sensor data from such sensors can be used to determine position, tilt angle, orientation, velocity, power generation, turbine speed, depth within a body of water, and other states or configurations of the floating wind turbine  100 . Additionally, in some examples, sensor data from such sensors can be used to determine environmental conditions such as air temperature, water temperature, water salinity, wind speed, wind direction, wave height, wave direction, precipitation, and the like. Various examples can include systems and methods to control the blade pitch of the blades  174  to optimize power production from a floating wind turbine  100 . 
     As a floating wind turbine  100  is subject to dynamic wave loads, in various embodiments the floating wind turbine  100  can undergo dynamic pitch motion. The magnitude of the pitch motion of the floating wind turbine  100  can be related to the magnitude of the variation in these environmental forces, as well the characteristics of the floating wind turbine  100 , such as its pitch stiffness, damping and the like. In some embodiments, the floating wind turbine  100  can exhibit dynamic pitch motion up to 5° in amplitude. For example, for a floating wind turbine  100  with a design mean heel angle of 15 degrees, the platform could pitch from 10-20 degrees away from the vertical. As the floating wind turbine  100  is pitching back and forth, the relative wind velocity on the blades  174  can change. If the blade pitch is not adjusted, in some examples this could lead to unstable behavior of the floating wind turbine  100 . 
     In some examples, the power absorbed by the generator can be proportional to the relative velocity on the rotor to the power of 3. If we approximate the sinusoidal motion of the platform as a step curve, so that the relative velocity is either increased or decreased by a constant value ∇V, in various embodiments we are able to increase the power produced over one cycle. Mathematically, the power generated by a fixed turbine can be proportional to the cube of the incident wind speed V ∞ : 
     
       
      
       P 
       ∞ 
       ∝V 
       ∞ 
       3  
      
     
     Mathematically, the power generated by a wind turbine that is rocking back and forth can be proportional to the cube of the relative wind speed V rel  between the turbine and the wind: 
         P   enh   ∝V   rel   3 =0.5*( V   ∞   −∇V ) 3 +0.5*( V   ∞   +∇V ) 3   =P   ∞ +3 V   ∞   ∇V   2    
     The power enhanced can be proportional to ∇V 2  which can be the square of the pitch velocity of the platform multiplied by the hub height. In some examples, the instantaneous power enhancement is small. However, over the lifetime of the floating wind turbine  100 , the power enhanced can be significant. 
     In order to achieve this power enhancement in various embodiments, the thrust force absorbed by the floating wind turbine  100  must remain relatively constant over one pitching cycle of the floating wind turbine  100 . Natural periods in pitch for a floating wind turbine  100  can be generally 20-30 s in some examples. 
     One embodiment of a wind turbine controller method  1600  is depicted in  FIG.  16   . The purpose of the controller can be to determine the velocity of the rotor relative to the incident wind, by measuring or determining the positions, velocities and accelerations of the floating wind turbine  100  as well as the incident wind speed and direction. Then, blade pitch controllers can be actuated to ensure that the thrust on the rotor remains relatively constant. 
     An ancillary benefit of such wind turbine control system in various embodiments is that the amplitude of the variation of thrust force can be minimized, resulting in reduced fatigue damage on the turbine  700  and hull assembly  830 , and the like. The variation in the thrust force can result in a bending moment on the base of the tower  110 , which can be transferred to the hull assembly  830 . By reducing the variation in the amplitude of the thrust force, in various examples the fatigue damage accrued on the floating wind turbine  100  is reduced. 
     For example, referring to  FIG.  16   , at  1610 , position and/or orientation of the floating wind turbine  100  is measured or determined, which can include pitch, roll and yaw motions along with velocities, accelerations, and the like. In various examples such measurements or determinations can be based on sensor data obtained from sensors as discussed herein. At  1620 , incident wind speed, incident wind direction, and the like, are measured or determined, which can be based on sensor data obtained from sensors as discussed herein. 
     At  1630 , rotational motion, velocity and acceleration in line with wind direction can be determined, and at  1640 , rotational motion, velocity and acceleration in line with wind direction over a time horizon (e.g., 20-30 seconds) can be predicted or determined. At  1650 , a determination can be made for blade pitch angle(s) to minimize thrust variation and/or maximize power production over the controller time horizon, and at  1660 , a blade pitch system can be actuated to change the configuration of one or more blades  174  in accordance with the determination at  1650 . 
     The described embodiments are susceptible to various modifications and alternative forms, and specific examples thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the described embodiments are not to be limited to the particular forms or methods disclosed, but to the contrary, the present disclosure is to cover all modifications, equivalents, and alternatives. Additionally, elements of a given embodiment should not be construed to be applicable to only that example embodiment and therefore elements of one example embodiment can be applicable to other embodiments. Additionally, elements that are specifically shown in example embodiments should be construed to cover embodiments that comprise, consist essentially of, or consist of such elements, or such elements can be explicitly absent from further embodiments. Accordingly, the recitation of an element being present in one example should be construed to support some embodiments where such an element is explicitly absent. Additionally, use of the term “floating,” or the like, should not be construed to indicate that a given element or system is currently floating and instead that such an element is configured, configurable or capable of floating in a fluid.