Patent Application
20250196975
This disclosure relates generally to floating platform structures, and more particularly to methods and systems for floating platforms whose dynamic response to environment-induced motion may be damped by passive in-plane fluid dampers.
A variety of marine structures may be deployed at offshore locations. Such marine structures may include offshore floating platforms and structures used for wind turbines. In terms of the future of wind turbine design, one such design is a buoyant platform tethered to the sea floor by mooring lines (as is the case for semi-submersible platforms as is known in the art) that must support a very large tubular tower (e.g., on the order of hundreds of feet) with a nacelle mounted at the top of the tower. Rotor blades up to 200 feet or more in length are attached to the nacelle using mechanical and electrical equipment mounted in the nacelle. In order to support such large towers and rotor blades, a wind turbine's floating support platform may need to be quite large in order to compensate for the dynamics of the wind turbine system that will be subjected to environment-induced wave and wind-generated motion. Unfortunately, floating platforms large enough to compensate for wave and wind-generated motion require high capital expenditures that may make large wind turbines impractical or impossible to justify.
Rather than relying on a large floating platform for the support of a wind turbine, active and passive control systems have been contemplated for use in “absorbing” or damping wave/wind-induced dynamics acting on a wind turbine system. Active control systems typically rely on an external source of power to constantly power a damping mechanism. This leads to increased operational costs due to the need for constant application of power as well as maintenance. Passive control system approaches are typically based on “tuned mass dampers” (TMD) that are only impactful over some targeted and narrow range of frequencies based on the mass of the structure being damped. Unfortunately, floating-platform-supported wind turbines are subject to several frequencies at which dynamic responses could be the source of structural resonance. In addition, TMDs are extremely difficult to tune in an in-situ field environment such as the open ocean. Accordingly, TMDs do not provide an effective and reliable solution to the damping of varying types of motion or resonance that will be experienced by an offshore, floating-platform-supported wind turbine.
Accordingly, it is an object of the present disclosure to describe methods and systems for damping motion of offshore floating platforms.
Another object of the present disclosure is to describe methods and systems for passively damping motion of offshore floating platforms.
Still another object of the present disclosure is to describe methods and systems for damping a variety of environment-induced movements of an offshore floating platform used to support a wind turbine system.
Other objects and advantages of the methods and systems described herein will become more obvious hereinafter in the specification and drawings.
In accordance with methods and systems described herein, a support system includes a platform adapted to float at a surface of a body of water. The platform includes a first pontoon and a set of second pontoons coupled to the first pontoon. Each second pontoon includes a container, a pair of spaced-apart and gas-filled compressible elements disposed in the container, a liquid filling the container between the pair of compressible elements, and a gas flow controller coupled to each compressible element and operable to control a flow of the gas between the compressible elements.
Other objects, features and advantages of the methods and systems described in the present disclosure will become apparent upon reference to the following description of the preferred embodiments and to the drawings, wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings and wherein:
For simplicity and illustrative purposes, the present disclosure is described by referring mainly to exemplary embodiments thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be readily apparent to one of ordinary skill in the art that the present disclosure may be practiced without limitation to these specific details.
The present disclosure describes support systems and methods for passively damping out unwanted motion of a floating platform and any structure supported thereby that may be induced by environmental forces. For example, when the support system is deployed at an offshore location for support of a wind turbine, relevant environmental forces include wind, waves, and water currents. In the presence of such varying and/or cyclical environmental forces, a floating platform and its supported structure may experience movement and resonation at a variety of frequencies.
Referring now to the drawings and more particularly to
In both support systems 10 and 11, platform 20 includes a central pontoon 22 and a set of motion-damping pontoons 24 coupled to central pontoon 22. In some embodiments, motion-damping pontoons 24 may be coupled to a periphery of central pontoon 22 and extend outward therefrom. In some embodiments, one or more of motion-damping pontoons 24 may be integrated or incorporated into central pontoon 22. In some embodiments, one or more of motion-damping pontoons 24 may be tangentially positioned relative to central pontoon 22. In some embodiments, central pontoon 22 and motion-damping pontoons 24 lie in a common plane at or near surface 102. Each motion-damping pontoon 24 may be configured to include a fluid damper as will be described further below.
As mentioned above, floating platform support system 10 is free-floating, while support system 11 is tethered or moored to the bottom 104 of the body of water 100. In terms of supporting a structure such as a wind turbine in a preferred orientation in the body of water 100, the tethered floating platform system 11 will generally be used. Accordingly, by way of example, the remainder of the present disclosure will focus on tethered floating platform support system 11.
In tethered or moored support systems such as support system 11, one or more mooring elements or mooring lines may be used to tether the platform to the bottom of the body of water. For example, support system 11 illustrates one such embodiment where each of support system 11's motion-damping pontoons 24 has one or more mooring elements or mooring lines 30 connected at one end 30A to a pontoon 24 and connected at another end 30B (i.e., anchored) to a location at the bottom 104 of the body of water 100. In some embodiments, end 30A is coupled to an outboard end of its corresponding pontoon 24. Each anchored end 30B of a mooring element 30 may be attached to an anchor (“A”) 32 embedded in the bottom 104 of the body of water 100. In general, each mooring element 30 is either in tension or under slack (depending on the movement of the platform structure) such that the set of mooring elements 30 associated with support system 11 keeps platform 20 substantially at its installed vicinity and at a generally horizontal orientation, while allowing platform 20 to experience what will be referred to herein as “shifted movements” along and about (i.e., vertical movements and rotations) the surface 102 of the body of water 100. Such shifted movements are generally caused by one or more of wind, waves, and water currents acting on platform 20 or any structure (not shown in
Support system 11 passively damps the above-described environmentally-induced shifted movements of platform 20 using the set of motion-damping pontoons 24 in order to prevent support system 11 (and any structure supported thereon) from resonating at one or more frequencies at which damage may occur. Referring now to
A gas flow controller 48 is coupled to each of compressible elements 44 to control the flow of gas between compressible elements 44. That is, gas flow controller 48 is in fluid communication with the gas-filled regions of both compressible elements 44. In general, controller 48 may be operable to balance the gas pressure acting on each of compressible elements 44 to thereby oppose the momentum of liquid 46 caused by either of motions 200 or 202 of container 42. By opposing shifting momentum of liquid 46, fluid damper 40 effectively damps the motion 200 or 202 of container 42 that causes the shifting momentum of liquid 46. Examples of gas flow controller 48 include, but are not limited to, an orifice plate having one or more holes, a pressure-sensing two-way valve, a flow restricting pipe(s), a venturi, etc.
The features of fluid damper 40 may be incorporated into a motion-damping pontoon 24 of support system 10 or 11 in a variety of ways without departing form the scope of the present disclosure. For example and with reference to the isolated plan view depicted in
As mentioned above, platform 20 may be configured in a variety of ways without departing from the scope of the present disclosure. For example, a floating platform's central pontoon 22 in accordance with the present disclosure may have a footprint at or near the water's surface defined by a polygonal shape having vertices or corners. Such polygonal shapes may include triangles, rectangles, or other multi-sided polygons. In some embodiments, the polygonal shape may utilize identical-length sides (e.g., equilateral triangle, square, etc.) to simplify both the above-described vertical support and motion damping using symmetrical arrangements of support and damping features.
Referring now to
As mentioned above, a structure (e.g., a wind turbine tower) may be coupled to a floating platform system described in the present disclosure. In some embodiments a tower structure may include an open-framework base coupled to the floating platform. For example and with reference to
As also mentioned above, support systems in accordance with the present disclosure may include a supported structure disposed on a tethered version of the support system's platform. For example, a wind turbine may be mounted on the support system's platform. In general and as is well-known in the art, wind turbines include a tubular solid-wall support tower, a nacelle housing a generator, gear box, bearings, etc. mounted atop the support tower, and blades coupled to a rotating hub extending from the nacelle. In accordance with the present disclosure and as illustrated in
The advantages of the systems and methods described herein are numerous. The disclosed floating platform support system passively damps shifted movement of a floating platform. The multiple motion dampers may be distributed about the periphery of a floating platform support system to damp the platform's shifted movements in a variety of directions. Since each motion damper operates independently, the support system is able to adapt to and damp motion over a variety of frequencies thereby making the support system ideally suited for inclusion as part of an offshore wind turbine installation.
Although the methods and systems presented herein have been described for specific embodiments thereof, there are numerous variations and modifications that will be readily apparent to those skilled in the art in light of the above teachings. For example, motion dampers described herein may additionally or alternatively be disposed along sides of a platform. The hybrid tower described herein may also be used with other types of floating or land-based installations. It is therefore to be understood that, within the scope of the appended claims, the methods and systems presented herein may be practiced other than as specifically described.
