Method and apparatus for wind power foundation

An apparatus and method for a wind power foundation. An embodiment of a wind power plant includes a tower having a top and a bottom. The plant also includes an assembly, the assembly including a transition piece that is coupled with a concrete cap. The assembly has a top and a bottom, with the top of the assembly being coupled with the bottom of the tower. The plant also includes a jacket structure. The jacket structure has a top and a bottom and multiple legs, with the bottom of the assembly being coupled with the top of the jacket structure.

FIELD OF THE INVENTION

The invention relates to wind power plants in general. More particularly, the invention relates to a foundation for a wind power plant.

BACKGROUND

Wind power continues to grow as a source of electricity because of its potential to provide abundant, pollution-free power. Demand for this alternative energy source is expected to increase because of concerns regarding reductions in fossil fuel supplies, the impact of traditional energy sources on the environment, and the increasing need for electric power throughout the world.

As the use of wind power increases, more questions have arisen regarding the placement of wind power plants. For all of the benefits of wind power, it is clear that wind power conventionally requires a large amount of real estate for placement of plants. As an alternative to land-based wind power generation, wind power plants have been placed offshore in ocean waters, thereby making use of offshore winds while not requiring any land for placement.

However, the establishment of offshore wind power generation introduces new factors. An offshore wind power plant requires a foundation that will withstand the combination of the lateral stresses that are inherent in wind generation together with the additional forces of waves and currents in an offshore environment. If wind power plants are established farther offshore, the deeper waters may result in an increase in intensity for these natural forces. In addition to creating greater forces in operation, the placement of wind power plants farther off-shore creates a more complex environment for plant construction, with much of the plant foundation being deep underwater.

BRIEF DESCRIPTION OF THE INVENTION

A method and apparatus for a wind power plant foundation is presented.

In a first aspect of the invention, an embodiment of a wind power plant includes a tower having a top and a bottom. The plant also includes an assembly, the assembly including a transition piece that is coupled with a concrete cap. The assembly has a top and a bottom, with the top of the assembly being coupled with the bottom of the tower. The plant also includes a jacket structure. The jacket structure has a top and a bottom and multiple legs, with the bottom of the assembly being coupled with the top of the jacket structure.

DETAILED DESCRIPTION

In an embodiment of the invention, a method and apparatus for a wind power plant foundation is disclosed.

For the purposes of this description:

“Wind power plant” means a structure to generate electrical power from wind energy. A wind power plant may also be referred to as a wind power turbine. A wind power plant may include any type of component to capture wind energy, including a rotor and rotor blades.

“Foundation” means all or a part of a structure intended to hold up a wind turbine in place. For instance, an off-shore wind power turbine may include a foundation that is intended to hold the turbine above the water surface. A foundation may include a base or pad at the ground surface and/or penetrating therein and intervening sections coupled with a, the tower being a section that, among other purposes, provides the needed height for the wind power turbine. In one example, a foundation may be placed or installed in a body of water to hold a wind power turbine in place. A tower may be coupled with the foundation to hold a wind power turbine at a desired location. In this example, a foundation is wholly or partially below the surface of the water, depending on the particular implementation.

A “Pile” is a length of material to be driven into the earth. A pile may include a cylinder or other shape and may be made of any material, including metal.

“Concrete” means any mixture of aggregate (rocks, sand, gravel), water, and a binder. The binder is commonly cement. The elements of concrete are provided in certain proportions to harden to a strong consistency. For the purposes of this disclosure, the term concrete includes reinforced concrete, which is generally concrete to which some reinforcement or strengthening material has been added. Reinforced concrete may include, but is not limited to, metal or fiber reinforcement, including common metal bar (“rebar”) reinforcement.

“Cement” means a material, usually in powdered from, that develops adhesive qualities when combined with water.

“Jacket” or “jacket structure” means a metal lattice intended to support a platform. A jacket may commonly support an offshore platform, which may be referred to as a jacket platform. A jacket generally includes multiple legs and braces, which may include multiple horizontal, vertical, or diagonal crossbeams, to form the lattice structure and to provide strength and rigidity in the structure.

Off-shore wind power plants are subjected to numerous forces. If the size of an offshore wind power plant is increased for overall cost effectiveness, the forces on the structure can increase, thereby increasing the load on the foundation. In addition, forces may also potentially increase if the wind power plant is established farther offshore, such as when near shore placements for a location are exhausted, or in deeper waters.

A foundation suspends a wind power turbine, the foundation being a means for holding the turbine and being wholly or partially submerged in water when installed. Under an embodiment of the invention, a foundation for an offshore wind power plant includes a concrete platform, or concrete cap. In an embodiment of the invention, a transition piece made primarily of metal, or metal and concrete, is coupled with the concrete cap to form an assembly. The transition piece/concrete cap assembly may be produced onshore in climate-controlled conditions and then be transported to the turbine location for installation. In an embodiment, the assembly is coupled to and suspended on a jacket structure or similar metal structure. In an embodiment, the jacket structure includes multiple legs, the legs expending generally from the top of the structure to the bottom of the structure. In an embodiment of the invention, the concrete cap and the jacket structure are coupled by one or more of the legs passing at least partly through the concrete cap. In an embodiment of the invention, a flanged connection is used to mount the concrete pad on the top of the jacket, the legs of the jacket running through the flange into or through the concrete cap. In an embodiment, a tower is installed on the foundation, and a wind turbine is installed on the tower, the wind turbine being a means for producing electrical power from wind energy.

In an embodiment of the invention, a wind power plant may be installed in a desired location by constructing all or a part of the foundation at another location, transporting the foundation to the installation location, and placing the foundation into the desired location. Once the foundation is in place, the construction of the wind power plant may be completed, which may include the installation of the wind power turbine on the tower. The installation process may thus be quicker and simpler than conventional processes.

An embodiment of a wind turbine may be secured in a location in a variety of different manners using different base structures, with the manner depending on the particular location and conditions. An embodiment may be secured using any known method of securing a jacket structure in a location. The base provides a means for holding the wind power plant in place.

In a first embodiment, a jacket structure supporting a wind turbine plant is secured by one more piles driven through the legs of the jacket structure into the earth surface. In this embodiment, the legs of the jacket structure are hollow sleeves, such as pipe-like structures, through which a pile may be inserted. The jacket structure may be placed in the appropriate location for the wind turbine plant, with the piles inserted through the leg sleeves of the jacket structure and driven into the earth.

In a second embodiment, a jacket structure supporting a wind turbine plant is secured by a concrete pad or similar gravity base. The concrete pad may be referred to as a gravity base structure (GBS). A GBS secures a structure using the mass of the base structure. In an embodiment, the bottom portions of the legs of the jacket are run at least partially through the GBS. The legs of the jacket may be secured by a flanged connection, each leg running through the flange into the GBS.

In a third embodiment, a jacket structure supporting a wind turbine plant may be secured by multiple concrete pads or GBSs. For example, the bottom portion of each leg of the jacket may run partially or wholly through a concrete pad. Each leg may be secured by a flanged connection, the leg running through the flange into the concrete pad.

In an embodiment of the invention, the load transfer of a wind power turbine is modified to increase the strength and resiliency of a base structure. In certain types of structures, a load on a tower is transferred to a concrete section, and then is transferred directly to the soil. While the concrete cap may provide a good physical connection to the tower, the concrete cap may not effectively transfer the load to the soil, and may create concentrations of stress in the structure. In another example, a wind turbine supported by a jacket structure may better transfer load forces, but the jacket does not provide an optimal coupling with the tower. In an embodiment of the invention, the advantages of coupling a tower with a concrete cap are combined with the load transfer capabilities of a jacket structure. In this embodiment, the loads encountered by the wind turbine tower are transferred from the tower to a transition piece/concrete cap assembly. In an embodiment, the foundation allows the dispatching load while avoiding stress concentrations, which is of great importance because the fatigue lifespan of a structure is critical in the design of an offshore structure. The loads encountered by the jacket assembly are then transferred to the base structure, such as a GBS or piles driven into the earth, and then to the soil.

In an embodiment of the invention, a wind turbine is supported by a structure that provides effective support in deep waters. A concrete GBS may provide a sufficient structure in more shallow waters, but the size and weight of the GBS will become extremely large in deep waters. In an embodiment of the invention, the amount of concrete required for the wind power turbine foundation may be greatly reduced by providing a jacket structure as an intermediary between the concrete cap and the base of the foundation. In addition, the jacket structure allows for reduction in wave loading because of its lattice structure, while the advantages of the coupling between the tower and the concrete cap are retained. In an embodiment, the lattice structure of the jacket may used to provide needed stiffness, support, and lateral strength to handle the significant wind and wave loading forces that may be encountered in deep water wind turbine installations.

If a wind power plant is placed in a deep offshore location, then stresses on the foundation of a wind power turbine include not only lateral stresses caused by the wind, but also include considerable stresses from the water environment. The water stresses include wave pressures and current pressure. Further, the multiple stresses on a wind power plant in an offshore location may come from different directions simultaneously and may shift directions quickly. In an offshore marine environment, a wind turbine may potentially experience extreme conditions, including winds reaching hurricane-force and waves that may approach tsunami waves. In an embodiment of the invention, a foundation utilizing a transition piece/concrete cap assembly coupled with a jacket structure may provide secure coupling for a wind power tower, effective transfer of the loads encountered in the environment, and simplified construction for deep water installation.

While this description refers to placement of a wind power plant offshore, embodiments of the invention are applicable to any wind power plant that is located in water locations, including an ocean, lake, man-made reservoir, or river.

FIG. 1is an illustration of an embodiment of a wind power plant. In this simplified illustration, the wind power plant100includes a rotor105and one or more rotor blades110. While this illustration shows a common rotor and rotor blade apparatus, embodiments of the invention are applicable to any type of wind power plant design, which may include various structures and components that are designed to capture wind power. In this illustration, the wind power plant100also includes a tower115to suspend the rotor105and rotor blades110. The wind power plant100also includes a foundation120to support the tower115, with the foundation potentially including multiple sections. The foundation120is attached to a base or pad structure125to secure the wind power structure in a location. In this illustration, the wind power plant100is installed in the earth130(through the mudline below the surface of water135(LAT). The wind power plant may be placed in deep waters offshore.

In an embodiment of the invention, the foundation120is constructed to provide good coupling with the tower115while also providing effective load transference to the earth surface130. In an embodiment, the foundation120includes an assembly, the assembly including a concrete cap coupled with a transition piece for coupling with the tower. In an embodiment, the foundation120further includes a jacket structure, the assembly to be coupled with the jacket structure. The jacket structure is then coupled with the base125of the wind power plant100. Embodiments of the foundation120are further illustrated in the other drawings.

FIG. 2is an illustration of possible base structures for an embodiment of a wind power plant. In this illustration a wind power plant is installed below the surface of the water205in the seabed210. A base structure may include a monopile215, such as a pipe or column structure that is drilled or otherwise driven into the ground. A pile220may be a column made of a material such as steel or concrete that is driven into the ground to provide support for a structure, but may be made of any material. Conventional offshore structures have often utilized monopile foundations, but such structures are expensive to install, with the cost increasing as the wind power plant is increased in size or placed further offshore. A pile base may also include a multiple pile base225, with multiple piles230being driven into the seabed210.FIG. 2also illustrates a gravity base235including a gravity base structure (GBS) or ballast base240, which is a heavy base structure that used the force of gravity to keep the base in place. The size of the foundation may be limited by forces on the base and the stability of the structure.

FIG. 2further illustates a suction base245, which includes one or more Caissons or chambers250that placed on the seabed and installed using suction or vacuum Forces, such as by pumping the water out of the chamber. The chambers, commonly known as caissons or suction caissons, are watertight chambers that are open on the bottom, resembling a can that is opened on one end and is filled with water and placed open side down. This structure may be also referred to as a bucket foundation. A suction foundation may be installed relatively quickly in comparison with pile foundations.

FIG. 3is an illustration of an embodiment of a GBS foundation for a wind power plant300. In this illustration, a tower305is mated to a steel or steel/concrete transition piece310that transfers the loads to the concrete (generally with steel rebar reinforcement) base, referred to here as the GBS or concrete cap315. The transition piece310and the concrete cap315may form an assembly320that may be fabricated together. In an embodiment of the invention, piles325may optionally be driven through the outer portion or “skirt” of the GBS315to increase lateral load capacity. Such piles325may be referred to as “skirt piles”, which generally refers to smaller diameter piles driven at the bottom of a structure, including a jacket-type structure, to secure the structure to the soil. “Skirt piles” may specifically refer to small-diameter piles driven around the circumference of a GBS-type foundation to prevent sliding of the foundation. In addition to concrete, the GBS315may include cavities into which rock can be placed to increase foundation weight. The GBS may be fabricated onshore, which could potentially include inclusion of a lower portion of the tower section305and wind turbine components housed therein. The components may then transported to a site that has been prepared and leveled to receive the GBS and installed. However, the illustrated wind power plant300is placed in relatively shallow water depth340from the LAT335to the mudline345.

FIG. 4is an illustration of an embodiment of a GBS foundation for a wind power plant400in a deep water installation. In this illustration, a tower405is again mated to a steel or steel/concrete transition piece410that transfers the loads to the concrete (with steel rebar reinforcement) GBS415, the transition piece410and concrete cap415forming an assembly420. Skirt piles425may be optionally used to increase lateral load capacity and cables430may enter the GBS. In this illustration the wind power plant400is placed in a relatively deep water depth440from the LAT435to the mudline445. Because of the depth, the GBS415is required to be large with a wide base for stability, thus requiring a great amount of concrete and creating a very heavy structure. A portion450of the GBS415may be modified to improve the structure, such as providing an “inverted wine glass” shape that provides more mass at the bottom of the structure, while providing a relatively thinner portion to attach to the transition piece410. Further, the GBS may be hollow in part to allow flooding with water. However, the GBS415remains very large, and will be more difficult to fabricate offshore for transport to the desired location than smaller bases for shallow water installations.

FIG. 5is an illustration of an embodiment of a wind power plant foundation with a pile base. In this illustration, a tower505of a wind power plant500is mated to a steel or steel/concrete transition piece510that transfers loads to a concrete cap (with steel rebar reinforcement)515, the transition piece510and concrete cap515forming an assembly520. In this illustration, the assembly520is relatively small and may be assembled as a unit and transported to an installation site with less difficulty than larger concrete bases. The assembly520is coupled with a jacket structure555, allowing the transfer of loads from the concrete cap515to the metal lattice of the jacket structure555. The concrete cap515may include flanged connections565to accept insertion of the tops of the legs of the jacket structure555into the concrete cap515. In an embodiment, the wind power plant500is secured by a pile base, formed by the piles560being driven through the legs of the jacket structure555into the earth. In this illustration the wind power plant500may placed in a relatively deep water depth540from the LAT535to the mudline545, with the assembly520and the jacket structure forming a foundation with a secure mounting for the tower while also providing effective load transference to the soil.

FIG. 6is an illustration of an embodiment of a wind power plant foundation with a single concrete pad base. In this illustration, a tower605of a wind power plant600is again mated to a steel or steel/concrete transition piece610that transfers loads to a concrete cap (with steel rebar reinforcement)615, the transition piece610and concrete cap615forming an assembly620. The assembly620is coupled with a jacket structure655. The concrete cap615may include flanged connections665to accept insertion of the tops of the legs of the jacket structure655into the concrete cap615. In an embodiment, the wind power plant600is secured in place by a single concrete pad or GBS675. The concrete pad675may also include flanged connections670to accept insertion of the bottoms of the legs of the jacket structure655. The wind power plant600may again be placed in a relatively deep water depth640from the LAT635to the mudline645.

FIG. 7is an illustration of an embodiment of a wind power plant foundation with a base including multiple concrete pads. In this illustration, a tower705of a wind power plant700is again mated to a steel or steel/concrete transition piece710that transfers loads to a concrete cap (with steel rebar reinforcement)715, the transition piece710and concrete cap715forming an assembly720. The assembly720is coupled with a jacket structure755. The concrete cap715may again include flanged connections765to accept insertion of the tops of the legs of the jacket structure755into the concrete cap715. In an embodiment, the wind power plant700is secured in place by multiple concrete pads780, such as by a concrete pad for each of the legs of the jacket structure755. Each concrete pad775may also include a flanged connection770to accept insertion of the bottom of a leg of the jacket structure755. The wind power plant700may again be placed in a relatively deep water depth740from the LAT735to the mudline745.

WhileFIGS. 5,6, and7have illustrated certain embodiments of a foundation structure, embodiments of the invention are not limited to the illustrated details. Embodiments of the invention are not limited to the base structures shown in such figures, and may be implemented with any base structure, assembly, or mechanism that will secure a jacket structure in place.

FIG. 8is a flow chart to illustrate an embodiment of installation of a wind turbine plant. The flow chart includes general processes in order to illustrate an embodiment of the invention, and is not intended to include every process that may involved in the installation of a wind turbine plant, which may be a very complex undertaking.

In this illustration, an off-shore placement for a wind power plant may be determined805. In an embodiment, the off-shore placement will have a certain expected water depth. A foundation will be placed beneath the surface of the water to hold the wind power turbine, and the foundation will be coupled with a base assembly or mechanism of some kind. The dimensions of the foundation are determined based on the conditions of the chosen location810. The conditions that may be considered include, but are not limited to, the type and size of the wind turbine (affecting loading characteristics); the expected wind conditions (affecting wind loading characteristics, and possibly determining the ultimate height of the turbine above the water surface); the water depth (affecting the needed dimensions of the foundation below the water); and the expected wave conditions (affecting wave loading).

A transition piece, generally being made of metal or metal and concrete, then is formed for the wind power plant815. An assembly is then fabricated using the transition piece and a concrete cap820. The assembly may be fabricated in climate-controlled conditions at any location, thus minimizing the amount of construction that must be done at the site and that will be done underwater. A jacket structure is then constructed825, the size, shape, and other construction details being based at least in part on the conditions of the installation site. The foundation elements may then be transported to the installation site830. At the installation site, the jacket structure may be placed and installed into a base structure835and the assembly installed on the jacket structure840. The tower is installed on the assembly845, and the wind turbine may then be installed on the tower850.

While a particular set of processes has been provided for illustration, embodiments of the invention are not limited to these processes to any particular order of execution of such processes. In other embodiments, the wind power turbine may be constructed in different order or in different locations. For simplicity, the portions of the wind power turbine have been described in general, but a wind power plant includes many mechanical and electronic components are not described here.

FIG. 9is an illustration of load transference for embodiments of wind power plants. InFIG. 9, the load transfer for a wind power plant having a GBS base905, such as shown inFIGS. 3 and 4, in shown. For this structure, the loads encountered by the tower910are transferred to the concrete cap or GBS915. The loads encountered by the concrete cap and then transferred to the soil920.

For a wind power plant having a jacket structure coupled with a pile base925, such as shown inFIG. 5, the loads of the tower930are transferred to the concrete cap935, which can then transfer loads to the jacket superstructure940. The loads then may be transferred to the piles of the pile base structure945and to the soil950.

For a wind power plant having a jacket structure coupled with a single concrete base or multiple concrete bases955, such as shown inFIGS. 6 and 7respectively, the loads of the tower960are again transferred to the concrete cap965, which can then transfer loads to the jacket superstructure970. The loads then may be transferred to the concrete GBS(s)975and to the soil980.