Shallow draft, wide-base floating wind turbine without nacelle

Abstract

Disclosed are wind turbines suitable for floating application. The wind turbines include multiple floats and multiple towers connected to the floats, a turbine rotor, including a hub and a plurality of blades, structurally supported by the plurality of towers, the turbine rotor coupled to an electrical generator; and have a very shallow draft even for rated capacities of at least 1 MW. The wind turbines can have a single mooring line for yawing eliminating the need for a nacelle, and can allow for deck-level belt driven electrical generators without the need for gear boxes.

What is claimed is: 
     
         1 . A wind turbine, (i) comprising a) a plurality of floats and one or more connectors interconnecting the plurality of floats; b) a plurality of towers connected to the plurality of floats; and c) a turbine rotor, including a hub and a plurality of blades, structurally supported by the plurality of towers, the turbine rotor coupled to an electrical generator; and (ii) (a) having a rated capacity of at least about 1 MW and a draft of less than about 1 meter per 1 MW of rated capacity, or (b) having a mass of at least 30,000 kg and a draft of less than about one sixth of the length of the blades. 
     
     
         2 . The wind turbine of  claim 1 , having a draft of less than 10 meters. 
     
     
         3 . The wind turbine of any one of the preceding claims, wherein the plurality of floats are spaced apart defining an area A between the floats, the blades have a length l, and l/√{square root over (A)} is less than 5. 
     
     
         4 . The wind turbine of any one of the preceding claims, wherein connections between the plurality of floats include one or more rigid connectors selected from beams and trusses. 
     
     
         5 . The wind turbine of any one of the preceding claims, wherein connections between the plurality of floats include taut cables. 
     
     
         6 . The wind turbine of any one of the preceding claims, wherein at least two floats of the plurality of floats are rigidly connected. 
     
     
         7 . The wind turbine of any one of the preceding claims, wherein at least three floats of the plurality of floats are rigidly connected. 
     
     
         8 . The wind turbine of any one of the preceding claims, wherein at least four floats of the plurality of floats are rigidly connected. 
     
     
         9 . The wind turbine of any one of the preceding claims, wherein the plurality of floats is 2 to 10 floats. 
     
     
         10 . The wind turbine of any one of the preceding claims, wherein the plurality of floats includes floats that are approximately biconical. 
     
     
         11 . The wind turbine of  claim 10 , wherein the floats which are approximately biconical include an apex-up top cone with truncated top and an apex-down bottom cone connected below the apex-up top cone. 
     
     
         12 . The wind turbine of  claim 11 , wherein the apex-down bottom cone is truncated to provide a central hole. 
     
     
         13 . The wind turbine of any one of the preceding claims, having a mass of at least 30,000 kg and a draft of less than about one ninth of the length of the blades. 
     
     
         14 . The wind turbine of any one of  claims 1  to  9 , wherein the plurality of floats are round surface piercing floats, and the wind turbine has a draft of less than twice the diameter of the round surface piercing floats. 
     
     
         15 . The wind turbine of any one of the preceding claims, wherein the floats are adapted to provide a maximum buoyancy of about 120% to about 300% the weight-required buoyancy for the wind turbine. 
     
     
         16 . The wind turbine of any one of the preceding claims, wherein the turbine rotor is positioned such that the blades rotate between at least two towers of the plurality of towers. 
     
     
         17 . The wind turbine of any one of the preceding claims, wherein each tower of the plurality of towers is connected on top of a float. 
     
     
         18 . The wind turbine of any one of the preceding claims, characterized by a heave frequency larger than about 0.2 Hz, when it is not operating. 
     
     
         19 . The wind turbine of any one of the preceding claims, wherein the wind turbine has a mass of less than 1,000,000 kg. 
     
     
         20 . The wind turbine of any one of the preceding claims, not having a nacelle. 
     
     
         21 . The wind turbine of any one of the preceding claims, wherein the electrical generator is positioned between the plurality of towers. 
     
     
         22 . The wind turbine of any one of the preceding claims, wherein the electrical generator, when the wind turbine is floating on water, is positioned closer to the water than the turbine rotor. 
     
     
         23 . The wind turbine of any one of the preceding claims, wherein the turbine rotor is coupled to the electrical generator with a coupling comprising a sheave holding a belt, the sheave connected to the turbine rotor to rotate with rotation of the turbine rotor and the belt wrapping a smaller drum on a shaft which drives the electrical generator. 
     
     
         24 . The wind turbine of  claim 23 , wherein the sheave has a diameter which is about 25% to about 35% the length of the blades. 
     
     
         25 . The wind turbine of any one of the preceding claims, wherein the sheave has a diameter which is about 10% to about 20% of the diameter of the turbine rotor. 
     
     
         26 . The wind turbine of any one of the preceding claims, further comprising a gear box coupled to a shaft of the electrical generator. 
     
     
         27 . The wind turbine of any one of the preceding claims, wherein the wind turbine, when floating, is adapted to allow the plurality of towers to yaw as a single unitized structure to orient the turbine rotor against the wind. 
     
     
         28 . The wind turbine of any one of the preceding claims, further comprising a mooring cable attached to a fixed underwater mooring point, which, when under tension, points from the underwater mooring point to the hub or to a point in space within a distance from the hub which is less than about 20% of the length of the blades. 
     
     
         29 . The wind turbine of  claim 28 , wherein the mooring cable, when under tension, has a slope of about 0.7:1 to about 3:1. 
     
     
         30 . The wind turbine of  claim 28  or  29 , wherein the wind turbine further comprises an axle to which the hub is rotably connected, and the mooring cable is attached to a fixed underwater mooring point and windward attached to the axle. 
     
     
         31 . The wind turbine of  claim 28  or  29 , wherein the mooring cable is supported windward of the base by a standoff structure. 
     
     
         32 . The wind turbine of any one of  claims 28 ,  29 , and  31 , wherein the wind turbine comprises an axle to which the hub is rotably connected, and the mooring cable is not attached to the axle. 
     
     
         33 . The wind turbine of any one of  claims 28  to  32 , wherein yawing of the turbine rotor is the result of movement of the entire wind turbine. 
     
     
         34 . The wind turbine of any one of the preceding claims, wherein the plurality of towers is a plurality of lattice towers. 
     
     
         35 . The wind turbine of any one of the preceding claims, wherein the plurality of floats includes four floats configured in a square arrangement with a distance of about 36 meters to about 72 meters, the plurality of towers includes four lattice towers, each of the flour lattice towers attached to the top of one of the four floats, the four lattice towers sloping upward to structurally support the turbine rotor, each pair of diagonally opposite floats being rigidly connected. 
     
     
         36 . A wind turbine comprising a) four floats configured in a rectangular arrangement with a perimeter of about 144 meters to about 288 meters, each pair of diagonally opposite floats being rigidly interconnected; b) a turbine rotor, including a hub and a plurality of blades, each blade having a length between about 70 and 130 meters; c) four lattice towers, each of the four floats structurally connected on top to one of the four lattice towers, the four lattice towers sloping upwards to structurally support the turbine rotor positioned approximately above the centroid of the rectangular arrangement; d) a sheave connected to the turbine rotor to rotate with rotation of the turbine rotor, the sheave holding a belt coupled to a shaft of an electrical generator, the sheave having a diameter of about 15 to 40 meters; the electrical generator mounted closer to the floats than the turbine rotor. 
     
     
         37 . The wind turbine of  claim 36 , having a rated capacity of at least 10 MW and a draft of less than about 5 meter. 
     
     
         38 . A wind turbine, (i) comprising a) a plurality of floats and one or more connectors interconnecting the plurality of floats; b) a plurality of towers connected to the plurality of floats; c) a turbine rotor, including a hub and a plurality of blades, structurally supported by the plurality of towers, the turbine rotor coupled to an electrical generator; and d) a mooring cable attached to an underwater mooring point, which, when under tension, points from the underwater mooring point to the hub or to a point in space within a distance from the hub which is less than about 15% of the diameter of the turbine rotor, and with a slope of about 0.75:1 to about 3:1. 
     
     
         39 . The wind turbine of  claim 38 , wherein the mooring cable is positioned within the wind turbine at a position below 40% of the height of the hub. 
     
     
         40 . The wind turbine of  claim 38  or  39 , wherein the mooring cable is attached to an underwater mooring point and attached to the non-rotating axle. 
     
     
         41 . The wind turbine of  claim 38  or  39 , wherein the mooring cable is held windward of the base by a standoff structure. 
     
     
         42 . The wind turbine of any one of  claims 38 ,  39 , and  41 , wherein the wind turbine comprises an axle to which the hub is rotably connected, and the mooring cable is not attached to the axle. 
     
     
         43 . The wind turbine of any one of  claims 38  to  42 , wherein yawing of the turbine rotor is the result of movement of the entire wind turbine. 
     
     
         44 . The wind turbine of any one of  claims 38  to  43 , having a rated power of at least about 1 MW and a draft of less than about 1 meter per 1 MW of rated capacity. 
     
     
         45 . The wind turbine of any one of  claims 38  to  44 , having a mass of at least 30,000 kg and a draft of less than about one sixth of the length of the blades. 
     
     
         46 . The wind turbine of any one of  claims 38  to  44 , characterized by a natural frequency in heave exceeding 0.2 Hz when mooring lines have been removed. 
     
     
         47 . The wind turbine of any one of the preceding claims, wherein electric power generated by the wind turbine is used to produce ammonia, hydrogen, liquid fuels, metals, or distilled water. 
     
     
         48 . The wind turbine of any one of the preceding claims, comprising a single mooring rope of controlled slope to prevent wind induced pitch while permitting rising with the tide, and yawing to follow the wind. 
     
     
         49 . The wind turbine of any one of the preceding claims, comprising a single mooring rope, wherein the mooring rope is a neutrally buoyant rope to prevent catenary sag and compliance. 
     
     
         50 . The wind turbine of any one of the preceding claims, having no ballast. 
     
     
         51 . The wind turbine of any one of the preceding claims, comprising one or more pressure wheels on a belt carried by a sheave to permit minimum belt tension. 
     
     
         52 . The wind turbine of any one of the preceding claims, further comprising a water source controlled to water-flood the sheave, when driven, to prevent damage in the event of overload. 
     
     
         53 . The wind turbine of any one of the preceding claims, wherein the turbine rotor has a rotor axle extending through the hub which is structurally supported by the towers at both ends of the rotor axle. 
     
     
         54 . The wind turbine of any one of the preceding claims, wherein at least one tower is downwind and one tower is upwind.