FIELD OF THE INVENTION
This invention relates generally to submerged structural supports, and more particularly to a submersible foundation for a wind turbine or similarly configured structure intended for installation on a seabed below a body of water, in addition to systems and methods for manufacturing and installing the same.
BACKGROUND OF THE INVENTION
The rise in the demand for renewable energy sources has led to an increased interest in offshore wind power generation due to more favorable wind conditions and less environmental impact than wind turbines installed on land. As a result, there is now a growing need for structures that can safely and reliably support wind turbines at significant heights above sea level. Typically, these support structures consist of a shaft or tower fixed to the seabed either by means of a foundation or a floating structure connected to the seabed by a mooring arrangement.
Current fixed support structures for offshore wind turbines typically require them to be divided into two parts: a foundation and a tower. The tower is typically mounted on the pre-installed foundation, with the foundation typically fixed to the seabed using either driven or drilled piles or a direct deployment onto an artificial gravel layer.
Unfortunately, existing techniques for delivering wind turbine foundations from certain locations to their intended offshore point of installation cannot meet the high demand for high manufacture and installation. Existing solutions using the force of gravity to fix the foundation to the seabed have been limited by their weight, water depth at the installation site, as well as water depth at the load-out locations and along the transport route. In previously attempted solutions that have relied solely on gravity for anchoring of the foundation, the top soil layers at the contact area of the foundation with the seabed are weak and often require replacement with better materials, such as gravel. Additionally, the seabed may be uneven and inclined, which necessitates further seabed preparation. Such prior concrete gravity-based offshore wind turbine foundations have included monopile, tripod, and jacket foundations. The monopile foundation is a single steel pipe driven into the seabed, while the tripod and jacket foundations consist of steel or concrete legs and a central column or tower. These previously known foundations, while effective in providing support for offshore wind turbines, have limitations in terms of their size, weight, and transportability.
Other prior systems for submersible wind turbine foundations have included a caisson supported by several columns embedded in the seabed, or a foundation structure for a wind turbine tower which can be maneuvered to its offshore position using a vessel and separate buoyancy means. These solutions tend to result in high overall capital investment costs due to fabrication, load-out, transport, seabed preparations, and installation.
In light of the foregoing, there remains a need in the art for systems and methods by which offshore wind turbines may be provided and installed in order to meet the growing demand for renewable energy sources in a cost-effective and sustainable manner.
SUMMARY OF THE INVENTION
In accordance with certain aspects of the invention, a precast concrete gravity-base foundation is provided that is both floatable and submersible in water. The foundation includes a bottom slab, four corner cylinders, a centrally located cylinder, and a top slab covering each of the corner cylinders and having a central opening that receives the top portion of the centrally located cylinder. The positioning of the corner cylinders serves to increase the overall stability of the foundation, similar to the outriggers on a rough-terrain crane. The production process for the foundation involves casting each individual piece on a production line and assembling the pieces piece-by-piece at a production facility on land adjacent to a water body. The foundation is then rolled onto a submersible jack-up barge by rail carts for transport to either a predetermined storage location or an installation site. The versatility of the foundation allows contractors to order and store them when needed and work year-round with less risk and equipment. A precast concrete gravity-base foundation formed in accordance with certain aspects of the invention will thus provide a novel and improved precast concrete gravity-base foundation that overcomes the limitations of prior art devices and methods, providing increased stability, transportability, and versatility.
In accordance with certain aspects of a particularly preferred embodiment, a method is provided comprising forming a precast concrete gravity-base foundation for supporting a structure in a body of water, the foundation further comprising a foundation bottom surface and a foundation top surface, each of the foundation bottom surface and the foundation top surface defining multiple outer corners, the foundation further comprising a plurality of hollow cylinders, wherein one of the plurality of hollow cylinders is positioned at each outer corner, and one of the plurality of hollow cylinders is centrally positioned on the foundation; positioning the foundation on a floating barge; transporting the barge and the foundation to a submersion site in a body of water; and removing the foundation from the barge at the submersion site for storage or service installation of said foundation.
Still other aspects, features and advantages of the invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the invention. The invention is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized. The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements, and in which:
FIG. 1 is shows placement of a precast concrete gravity-base foundation in a body of water and holding a wind turbine in accordance with certain aspects of an embodiment of the invention.
FIG. 2 is a side perspective view of a precast concrete gravity-base foundation according to certain aspects of an embodiment of the invention.
FIG. 3 is an exploded view of the precast concrete gravity-base foundation of FIG. 2.
FIG. 4 is a side perspective view of the precast concrete gravity-base foundation of FIG. 2 being loaded onto a barge after assembly.
FIG. 5 is a side perspective view of the precast concrete gravity-base foundation of FIG. 2 underway on a barge to an installation or storage site.
FIG. 6 is a top view of the precast concrete gravity-base foundation of FIG. 2.
FIG. 7 is a side view of the precast concrete gravity-base foundation of FIG. 2.
FIG. 8 is a top view of a base slab of the precast concrete gravity-base foundation of FIG. 2.
FIG. 9 is a side view of the base slab of FIG. 8.
FIG. 10 is a cross-sectional view of the base slab of FIG. 8 along section line A-A.
FIG. 11 is a cross-sectional view of the base slab of FIG. 8 along section line B-B.
FIG. 12 is a cross-sectional view of the base slab of FIG. 8 along section line C-C.
FIG. 13 is a top view of a top slab of the precast concrete gravity-base foundation of FIG. 2.
FIG. 14 is a side view of the top slab of FIG. 13.
FIG. 15 is a cross-sectional view of the top slab of FIG. 13 along section line D-D.
FIG. 16 is a cross-sectional view of the top slab of FIG. 13 along section line E-E.
FIG. 17 is a cross-sectional view of the top slab of FIG. 13 along section line F-F.
FIG. 18 is a schematic view showing a system and method for manufacturing a precast concrete gravity-base foundation according to further aspects of an embodiment of the invention.
FIG. 19 is a top view of a mandrel for use in the system of FIG. 18.
FIG. 20 is a top view of the mandrel of FIG. 19 in a partially collapsed configuration.
FIG. 21 is a close-up view of a closure joint of the mandrel of FIG. 19.
FIG. 22 is a schematic view of a production flow layout for casting cylinders for use in a concrete gravity-base foundation according to further aspects of an embodiment of the invention.
FIG. 23 is a schematic view of an assembly layout for assembling a concrete gravity-base foundation according to further aspects of an embodiment of the invention.
FIG. 24 is a side view of a barge for transporting a concrete gravity-base foundation assembled at the assembly layout of FIG. 23.
FIG. 25 is a side view of the barge of FIG. 24 with a fully assembled concrete gravity-base foundation loaded onto the barge.
FIG. 26 is a side view of the barge and concrete gravity-base foundation of FIG. 25 with the barge submerged and the concrete gravity-base foundation partially submerged.
FIG. 27 is a side view of the barge and concrete gravity-base foundation of FIGS. 25 and 26 with the barge submerged and released from the partially submerged concrete gravity-base foundation.
FIG. 28 is a top view of the barge of FIG. 24.
FIG. 29 is a close-up side view of the barge of FIG. 24.
FIG. 30 is a side cross-sectional view of the barge of FIG. 28 along section line A-A.
FIG. 31 is a side cross-sectional view of the barge of FIG. 28 along section line B-B.
FIGS. 32(a) and 32(b) are top and side views, respectively, of hydraulic cylinders for use with the barge of FIG. 28.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention may be understood by referring to the following description, claims, and accompanying drawings. This description of an embodiment, set out below to enable one to practice an implementation of the invention, is not intended to limit the preferred embodiment, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent assemblies do not depart from the spirit and scope of the invention in its broadest form.
Descriptions of well-known functions and structures are omitted to enhance clarity and conciseness. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, the use of the terms a, an, etc. does not denote a limitation of quantity, but rather denotes the presence of at least one of the referenced item.
The use of the terms “first”, “second”, and the like does not imply any particular order, but they are included to identify individual elements. Moreover, the use of the terms first, second, etc. does not denote any order of importance, but rather the terms first, second, etc. are used to distinguish one element from another. It will be further understood that the terms “comprises” and/or “comprising”, or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.
Although some features may be described with respect to individual exemplary embodiments, aspects need not be limited thereto such that features from one or more exemplary embodiments may be combinable with other features from one or more exemplary embodiments.
Unless otherwise indicated, all dimensions shown in the attached drawings are exemplary only and should not be construed as limiting the scope of the invention to those specific dimensions.
In accordance with certain aspects of an embodiment of the invention, a precast concrete gravity-base foundation and a production process, production machinery, and delivery system for such gravity-base foundation are disclosed herein. The gravity-base foundation is both floatable and submersible in water. As shown in FIG. 1, the gravity-base foundation (shown generally at 100) may, in certain exemplary implementations, be used for mounting the shaft 510 of an offshore wind turbine 500, although a gravity-based foundation configured in accordance with aspects of the invention may likewise be used in other applications. As shown in FIGS. 2 and 3, the gravity-base foundation includes a bottom slab 110, four cylinders 120 positioned at each corner of gravity-base foundation 100, a centrally located cylinder 130, and a top slab 140 covering each of the corner cylinders 120 and having a central opening that receives the top portion of centrally located cylinder 130. In an exemplary configuration, bottom slab 110 is a 120 ft. by 120 ft. square, each corner cylinder 120 has a height of 50 ft. and a diameter of 40 ft., center cylinder 130 has a height of 55 ft. and a diameter of 40 ft., and top slab is a 120 ft. by 120 ft. square. As discussed further below, each slab is preferably provided concrete ribs for additional support of the slabs. Further, as particularly shown in the exploded view of FIG. 3, each of bottom slab 110 and top slab 140 may comprise separate halves (110(a), 110(b), 140(a), and 140(b)) that are joined together during the process of assembling gravity-base foundation 100.
Once assembled, a foundation 100 configured in accordance with aspects of the invention equates to approximately 35,000 cubic yards (cy) of concrete, weighing approximately 7,100 tons with a bottom platform 110 that is 120 ft. by 120 ft. and has a footprint of approximately 14,000 ft2, or approximately 680 lbs./ft2 load on the seabed floor. Due to the tremendous volume capacity of the five cylinders 120 and 130, the foundation 100 has a buoyancy factor of approximately 70%. More particularly, foundation 100 preferably employs cylinders 120 and 130 that have a diameter that is at least ⅓ of the length of each side of bottom slab 110 and top slab 140, and each cylinder 120 and 130 has a height that is at least 25% greater than the diameter of such cylinder. Despite being formed of heavy concrete, such configuration ensures sufficient buoyancy to enable transport and handling of foundation 100 to allow improved, simplified installation over previously known methods, which ensure greater stability by having cylinders 120 located at each outer corner of foundation 100.
As a result of this configuration, the foundation 100 will sit approximately 15 ft. out of the water (70% submerged) while in storage or in transit. Once submerged into an operational position, the voided cylinders 120 (which may be emptied of water, for example, via pumping seawater from the interior of each cylinder) may then be filled with stone, sand, or other materials fostering an aquatic habitat for sea life to further bolster the foundation's mass capacity to accommodate future and possibly larger wind turbines.
The configuration of foundation 100 described herein, and particularly the positioning of corner cylinders 120, serve to function in a manner similar to outriggers on a rough terrain crane, in which the extension of those outriggers to the four corners of the crane provides maximum stability by widening the footprint of the crane. Similarly, corner cylinders 120 of foundation 100 increases the overall stability of the foundation for, for example, a wind turbine positioned in center cylinder 130, by positioning cylinders 120 at the extreme outside four corners of foundation 100. Once corner cylinders 120 are then filled with sand, stone, or the like, those corner cylinders 120 further bolster the overall mass and stability of foundation 100.
As further detailed below, each of the individual pieces of gravity-base foundation 100 is cast in a production line and assembled piece-by-piece at a production facility on land adjacent to a water body, and as shown in FIGS. 4 and 5 then rolled onto a submersible jack-up barge 200 by rail carts. After gravity-base foundation 100 has been loaded on the barge 200, barge 200 may transport the foundation 100 through the water to either a predetermined storage location or an installation site. When the foundation 100 is ready for placement at any such location, barge 200 is submerged to the required depth, allowing the foundation 100 to float due to the buoyancy of empty cylinders 120 and 130. In this position, foundation 100 can either remain afloat (anchored down) for storage, or cylinders 120 (and optionally 130) may be flooded (submerged) for storage, or if ready for installation, foundation 100 may be submerged to the seabed for serviceability. Such versatility and supply on-demand allows contractors to order foundations 100 when needed for a particular project. Additionally, the foundation 100 allows contractors to work year-round (with no moratorium constraints due to limited disturbance to the ecosystem), with less risk, fewer ships, cranes, and equipment, and fewer workers at the jobsite.
FIG. 6 provides a top view of foundation 100 (with cylinders 120 and additional support structure, discussed below, shown in phantom), and FIG. 7 shows a side view of foundation 100.
With continuing reference to FIGS. 1-7, and the detail and section views of base slab 110 and top slab 140 of FIGS. 8-17, foundation 100 comprises bottom slab 110, corner cylinders 120, central cylinder 130, and top slab 140. Bottom slab 110 includes ring mats 112 (shown in detail in FIGS. 11 and 12) positioned below each corner cylinder 120 and central cylinder 130, which ring mats 112 provide additional support structure for attachment of bottom slab 110 to each of cylinders 120 and 130. As best viewed in the top view of bottom slab 110 of FIG. 8, an outermost portion of each corner ring mat 112 defines a rounded corner edge of bottom slab 110, such that each corner ring mat 112 is in fact positioned at an outer corner of bottom slab 110, in turn positioning each corner cylinder 120 at the outermost corners of bottom slab 110.
Similarly, top slab 140 (FIG. 13) includes ring matts 142 that sit on top of each of corner cylinders 120 and provide further support for attachment of top slab 140 to each of corner cylinders 120. FIG. 11 shows a detail section view (along section line B-B of FIG. 8) of the attachment of bottom slab 110 to a wall of each of cylinders 120 and 130 adjacent the horizontal span of bottom slab 110, while FIG. 12 shows a detail section view (along section line C-C of FIG. 8) of the attachment of bottom slab 110 to a wall of each cylinder 120 adjacent an outer perimeter edge of each such cylinder 120. Likewise, FIG. 15 shows a detail section view (along section line D-D of FIG. 13) of the attachment of top slab 140 to a wall of each cylinder 120 adjacent the horizontal span of top slab 140, while FIG. 16 shows a detail section view (along section line E-E of FIG. 13) of the attachment of top slab 140 to a wall of each cylinder 120 adjacent an outer perimeter edge of each such cylinder 120.
Base slab 110 is heavily reinforced with both #11 and #14 steel bars extending laterally and longitudinally through base slab 110. At 18-in. thickness, base slab 110 is formed of approximately 800-cy of concrete, adding approximately 16-tons of mass to the overall foundation 100. Each ring matt 112 and 142 (that aligns with a wall of one of cylinders 120 and 130) contains a series of, for example, 8-in. corrugated metal sleeves 113 at 24-in in depth. Each ring mat 112 and 142 houses a piece of, for example, #14 threaded rebar (with terminators at the end) projecting from the ends of corner cylinders 120 and from the bottom of center cylinder 130. During assembly, cylinders 120 and 130 are carefully lowered into place onto their respective ring matts 112 on bottom slab 110. The 8-in. corrugated metal sleeves 113 allow sufficient forgiveness for each of the ninety bars to be properly set in place into bottom slab 110. Prior to each respective cylinder 120 and 130 being set onto its associated ring matt 112 of bottom slab 110, each tube housing the cylinder's projecting #14 bars is grouted using a high strength grout locking the connections into place and fusing the cylinders 120 and 130 to the base slab 110. Further, a grouted connection is provided around the base of each cylinder 120 and 130 for further waterproofing and fusing of each cylinder 120 and 130 to base slab 110. This process is carried out for joining each of cylinders 120 and 130 to base slab 110.
In an exemplary configuration, each of corner cylinders 120 is 50-ft. tall and has a diameter of 40-ft., with each cylinder wall having a thickness of 18-in. Each such corner cylinder 120 includes vertical reinforcement bars (#14 size) spaced at 12-in. O.C. and 0.6-in. (7-wire) steel strand is continuously wrapped around the vertical bars for connection to the base and top slabs as discussed above. In total, each of the four corner cylinders 120 are comprised of 350 CY of concrete, weighing approximately 670-tons. This configuration creates a void in each corner cylinder of 51,597 cubic feet, or 1,911 CY per cylinder. Further and as mentioned above, center cylinder 130 (which in certain exemplary configurations may house a windmill tower connection) is slightly taller than corner cylinders 120 with a height of 55-ft., having a volume of approximately 60,210 CF or 2,230 CY. Overall, center cylinder 130 in combination with the four corner cylinders 120 provides 266,598 CF of air volume (9.874 CY), in turn creating sufficient buoyancy necessary to allow the foundation configured as described here to float.
As with bottom slab 110, top slab 140 is preferably 120-ft. by 120-ft. and 18-in. thick. Top slab 140 is similarly configured as a planar member with downwardly extending ring matts 142 aligned with corner cylinders 120, but has a central opening that allows for center cylinder 130 to extend upward and past the top surface of top slab 140. FIG. 17 shows a sectional view of the top edge of center cylinder 130 extending upward from the top surface of top slab 140. While FIG. 17 shows a gap between top slab 140 and center cylinder 130, such gab is provided for tolerance and ultimately is sealed with a closure pour, further locking the full assembly of foundation 100 together. For the corner cylinders 120, the same process that was used for joining the cylinders to base slab 110 may be used for joining the tops of cylinders 120 to top slab 140. Top slab 140 aids in holding the complete assembly of foundation 100 in place, tying all corner cylinders 120 together to form a single, unitary foundation assembly.
Optionally, rib beams 114 may be provided on base slab 110 (and optionally on top slab 140) extending between each corner cylinder 120, and between each corner cylinder 120 and center cylinder 130, as additional structural support for each of cylinders 120 and 130.
Foundation 100 is erected and water-sealed through a series of concrete closure pours and grout along seams of joined elements. For example, as mentioned above with regard to FIG. 3 and as shown in FIGS. 8 and 13, each of bottom slab 110 and top slab 140 may be formed in separate halves to accommodate lifting capacity constraints, which separate halves must then be joined together during assembly of foundation 100. During the casting of each half, steel reinforcement used for slabs 110 and 140 comprise #8 size rebar, which is placed running both longitudinally and laterally through the slab profiles, and the 8-in. diameter corrugated metal sleeves 113 are tied into place for each of cylinder rings 112 and 142. Once casted and cured, each half of bottom slab 110 and top slab 140 may be individually moved to the assembly staging area or to a storage area. When ready for assembly, the two separate halves may be moved to the assembly area and fused together using a closure pour as shown in the section view of FIG. 10 (along section line A-A of FIG. 8).
Next, FIG. 18 shows a schematic view of the steps undertaken to cast each of corner cylinders 120 and center cylinder 130 prior to their assembly in foundation 100. Cylinders 120 and 130 are constructed on steel pads 302 that carry mandrel 304 (shown in FIGS. 19-21 and further detailed below) and that travel along train trollies on tracks 306 in a series of phases, with each phase comprising a designated production zone. The first production zone comprises a rebar crescent assembly zone 310, in which a series of steps are carried out to provide the rebar cylinder cage to be formed. More particularly, at stage 311, a cleaned and oiled mandrel 304 on steel pad 302 is rolled into position between open halves of a rebar tower 312. A rebar crescent jig allows for ten (10) vertical #14 rebar to be set at a time. The rebar jig may use a series of #4 rebar bent to the radius of the cylinder in order to keep the vertical rebar spacing intact while placing within the form and mandrel. After ten #14 bars are set into the crescent at a time, at stage 313 a crane then picks the rebar crescent up and sets it vertically alongside onto the mandrel, guided by workers on the platform of rebar tower 312. The bars are secured in position using a series of chairs (used to maintain the required amount of concrete cover) and a coupler ring at the base of the cylinder. This process is done nine times (to place 90 bars) until all vertical bars are in place. Once all the vertical rebar are in place, the rebar tying phase begins at stage 315.
Rebar tower 312 utilizes a series of winches on each vertical leg to lower and raise a continuous work platform 314. After all the vertical rebars are set, the work platform 314 slowly lowers at a rate of 1-ft per 3-minutes, allowing enough time for two 0.6″ (7-wire) 270-ksi high strength strand on two strand packs to revolve clockwise on a rail around the cylinder, equivalent to steel spiral for pile reinforcement. During this time, workers tie the strand to the #14 vertical rebar, maintaining a 12-in spiral spacing as they move downward. In an exemplary configuration, the entire rebar-tying process should be completed in approximately three (3) hours.
When the rebar tying phase of construction is complete, the rebar tower 312 is opened and disassembled into its two halves at stage 317, allowing for the cylinder cage and mandrel to be rolled (on train tracks 306) to cylinder concrete casting zone 330 that employs a Concrete Casting Machine (“CCM”) 332. Much like rebar tower 312, CCM 332 is formed of two halves that at stage 331 are brought together and secured to the mandrel 304 by a series of through-bolts and braces. Once ready for concrete casting of the cylinder, at stage 333 a high-capacity concrete pump truck(s), for example, delivers concrete to the form of CCM 332 from the bottom up (tremie pour). The concrete pour should take approximately four (4) hours to complete.
Once the concrete pour has been completed, the concrete is preferably cured with steam to accelerate the curing process. When the cylinder has cured, the tie bolts on the form are released and at stage 335 the two halves slide out and away from the newly casted cylinder 120/130. The concrete cylinder and mandrel then roll to the next zone for stripping of the mandrel. Here, and with reference to the detail views of mandrel 304 of FIGS. 19-22, mandrel 304 is collapsed and lifted from cylinder 120/130. Mandrel 304 is then immediately moved back to the initial production zone 305 (FIG. 18) where it is cleaned and oiled. At this point, the concrete cylinder 120/130 has successfully been cast, cured, and through holes have been filled. The concrete cylinder 120/130 is now ready for storage.
As shown in FIGS. 19-22, mandrel 304 forms a semi-collapsible cylinder that may be in an expanded position (FIG. 19), in which the outer wall of mandrel 304 forms a cylinder for rebar of cylinders 120 and 130 to be set, to a collapsed position (FIG. 20), in which portions of the outer wall of mandrel 304 slightly bend inward towards the interior of mandrel 304. In this regard, mandrel 304 includes a first gusset having a fist gusset angle 341 and a second gusset 342 having a second gusset angle 343. When in the fully expanded position (FIG. 19), first gusset angle 341 mates closely with second gusset angle 343 to form a closed joint 346 on the outside of mandrel 304. When moved to the collapsed position (FIG. 20) in order to withdraw mandrel 304 from a molder cylinder 120 or 130, first gusset 340 separates from second gusset 342 at first gusset angle 341 and second gusset angle 343, drawing both of them inward toward the interior of mandrel 304. A hydraulic cylinder 344 is provided and affixed to the interior of both first gusset 340 and second gusset 342, such that upon retraction of the piston of hydraulic cylinder 344, mandrel 304 assumes the collapsed position shown in FIG. 20, and such that upon extension of the piston of hydraulic cylinder 344, mandrel 304 assumes the expanded position shown in FIG. 19.
Next, FIG. 22 provides a schematic overview of a production flow layout for casting cylinders 120 and 130 as detailed above, with each step of the cylinder production flow process showing the same sections of a production facility with the cylinders being moved at different stages of their production. First, at step 1, at position 1 (“POS 1”), the rebar cage is tied about the mandrel 304 on a first steel pad 302 to form the rebar form of a first cylinder 120/130, and at position 2 (“POS 2”), concrete is poured to form a second cylinder 120/130 on an already-formed rebar form on a second steel pad 302. POS 1 thus reflects rebar crescent assembly zone 310, while POS 2 reflects cylinder concrete casting zone 330. Next, at step 2, at POS 1, rebar cage formation continues, while at POS 2, a now-finished cylinder with the mandrel 304 still installed is moved to position 3 with the second steel pad 302 (“POS 3”), which POS 3 serves as an intermediate staging area. Next, at step 3, at POS 1, rebar cage formation continues, while at POS 3 the mandrel 304 is moved onto a concrete slab of the work area for cleanup and oiling for its next use while the finished cylinder on the second steel pad 302 remains in place at POS 3. Next, at step 4, at POS 1, rebar cage formation continues, while the finished cylinder and the second steel pad 302 is moved by crane to position 4 (“POS 4”), which POS 4 serves as a final staging area for removal of the finished cylinder from the second steel pad 302. Next, at step 5, rebar cage formation continues at POS 1, while at POS 4 the second base 302 is removed and returned to POS 3 for processing of the next finished cylinder. Next, at step 6, the now-finished rebar cage on the first steel pad 302 is moved from POS 1 to POS 2, and CCM halves are brought together about the rebar cage for casting of the concrete cylinder about the finished rebar cage at POS 2. Finally, at step 7, second steel pad 302 is placed back on the track with the mandrel 304 positioned on the second steel pad 302 and moved into position at POS 1 to receive the next rebar cage, with the foregoing process thereafter repeating to form the desired quantity of cylinders 120/130.
Likewise, FIG. 23 provides a schematic view of an assembly layout (shown generally at 600) for assembling foundations 100 after each of cylinders 120 and 130, bottom slabs 110, and top slabs 140 have all been casted and cured. Assembly layout 600 forms at least part of a manufacturing facility that is positioned adjacent to a body of water that provides water access to open waters in which foundations 100 are to be installed. Thus, a first end 602 of assembly layout 600 includes the production stations POS 1, POS 2, POS 3, and POS4 discussed above, preferably in addition to storage of materials used during the assembly layout process, as well as storage of separate halves of bottom slabs 110 and top slabs 140 that are to be formed into finished foundations 100. From first end 602, finished cylinders 120/130 are stored at cylinder storage 604 adjacent to a slab assembly area 606 at which slab halves are joined together as detailed above. More particularly, a finished bottom slab 110 is positioned downstream of cylinder storage 604, such that finished cylinders 120/130 may be lifted via an overhead crane 608 and placed onto a completed base slab 110. The base slab 110 with mounted cylinders 120/130 may then receive top slab 140 to form a finished foundation adjacent to an exit from assembly layout 600. The exit from assembly layout 600 aligns with a barge that is floating in the body of water, such that the finished foundation 100 may be immediately loaded upon its completion for transport, as discussed in greater detail below.
Each of the precast components of foundation 100 in assembly layout 600 is picked and moved to assembly by 950-ton gantry crane 608. As mentioned above, due to crane capacity, base slab 110 is comprised of two equal halves 110(a) and 110(b). Each half is moved into position at slab assembly 606 and fused together by a large closure pour as discussed above and as shown in FIG. 10, locking hundreds of hairpin rebar loops in place. This closure pour seals up the series of #8 steel reinforcing hairpin loops and #8 straight bars that are tied together, locking everything in place. Once the closure pour is completed and the joint cured, the bottom slab is ready to receive the cylinders 120 and 130.
When the closure pour reaches strength, cylinders 120 and 130 are moved into position on base slab 110, locked into place by a series of couplers, and finally grouted. The grouting helps to further lock the cylinders into place on base slab 110 while also sealing the joints, making them watertight. When all five (5) cylinders are set and grouted on base slab 110, top slab 140 is moved in and fused together by a similar closure pour to the base slab.
After the completed foundation 100 has been successfully erected on blocking, one or more rail carts carry the foundation to floating submersible jack-up barge 200 (shown in FIG. 24) that is positioned in the waterway adjacent to the assembly layout 600. Once foundation 100 has been placed on barge 200 (as shown in FIG. 25), the rail carts carrying foundation 100 lower the foundation onto permanent dunnage blocks 202 (which dunnage blocks 202 are bolted to the barge) by a series of hydraulic cylinders on the rail carts, all of which are electronically controlled by a common controller for synchronized movement, lowering at the same speed and pressure. Preferably, a support is also provided below the barge during such loading operation. For example, in certain configurations, the barge may be submerged onto a manufactured seabed positioned adjacent the bulkhead so as to align the top of the barge with the elevation of the bulkhead during loading of the foundation 100, as shown in FIG. 25. Likewise in certain configurations, hydraulic cylinders 204 may be provided on the bottom of barge 200 that lower down onto a series of concrete piles driven into the natural seabed, stabilizing the barge to the bulkhead for loadout. Once the barge is loaded and the load is secured, foundation 100 is ready to be shipped to either storage or the installation site.
Because barge 200 is submersible, it may lower down to the required water depth, allowing for foundation 100 to safely float off of the barge as shown in FIGS. 26 and 27. If moved for storage, foundation 100 can either remain floating by anchoring it down or it may be submerged to the ocean/bay floor after removal of submerged barge 200 from below foundation 100. When ready for installation, the ocean seabed is graded and prepared with a level stone bed. Foundation 100 is then slowly submerged by remotely opening and closing valves on the bottom of the cylinders until settling on the seabed. To prevent scouring, large armored stone is preferably set around the perimeter of the foundation base.
The approximate size of submersible barge 200 is 150′ wide by 150′ long. Because of its size and capacity, in a particularly preferred configuration barge 200 only requires 15-18′ draft to successfully ship foundation 100 configured as described above, making it easy to get in and out of almost any port. Once foundation 100 is secured onto submergible barge 200, jacks 204 are pulled up and barge 200 is ready for shipping. At this point, foundation 100 is hauled on barge 200 to the submersion zone. Here, at roughly 60-ft of water depth, barge 200 begins the submersion process in order to separate from foundation 100. When foundation 100 reaches buoyancy, it is guided away from the submersed barge 200. Once clear, barge 200 is brought up to the surface and tugged back to the slip.
FIGS. 28-31 provide detail views of barge 200 (with the footprint of foundation 100 shown in phantom in FIG. 28), and FIG. 32 provides a detail view of jacks 204. With reference to those Figures, barge 200 includes a grid of precast concrete dunnage blocks 202 that are preferably welded to the deck plate of barge 200 and support foundation 100 in a raised position above the deck plate. Hydraulic cylinders 204 are positioned along the port and starboard sides of barge 200, and may be deployed downward onto piles in the seabed as discussed above to stabilize and level barge 200 as foundation 100 is loaded. Likewise, tracks 206 extend across deck plat of barge 200 from the bow towards the stern, which tracks 206 receive rail carts (not shown) that transport the finished foundation 100 from assembly layout 200 onto barge 200 as discussed above, and ultimately lower foundation 100 onto dunnage blocks 202. After foundation 100 has been loaded onto dunnage blocks 202 and hydraulic lifting cylinders on each rail cart have been fully retracted, the rail carts may return along tracks 206 to assembly layout 200 to receive the next finished foundation 100.
To provide additional support to barge 200 as a foundation 100 is loaded, weight bearing hydraulic supports 208 may be provided along the bow of barge 200 near each of the port and starboard sides, which hydraulic supports 208 may engage a receiver in a bulkhead against which the barge is docked to receive finished foundations from assembly layout 200. Such hydraulic supports 208 may aid in ensuring level alignment of the deck plate of barge 200 with the exit from assembly layout 600.
Preferably, barge 200 includes a control tower 210 positioned along the stern of the barge 200 to allow personnel to supervise the loading of a foundation 100. Likewise, as barge 200 is submersible, the interior is formed of open structural framing 212 (best viewed in FIGS. 30 and 31) to allow flotation along with filling with water to submerse at the intended foundation release site. Submersible pumps 214 are positioned along barge 200 preferably to allow water to be pumped into and out of barge 200 to enable submersion and surfacing as desired.
A precast concrete gravity-base foundation, and a production process, production machinery, and delivery system for the same, all configured in accordance with foregoing exemplary embodiments of the invention may provide both ecological and operational benefits over previously known systems, including one or more of the following:
- (1) A foundation 100 configured as above can be quietly lowered to the seabed without disturbing the local habitat. Current methods of driving a steel monopile is disruptive to the environment. Because of this, contractors must mitigate their disturbance to the marine life. Observing spawning seasons and migratory patterns of wildlife can typically account for roughly 4-5 months of stoppage, further pushing the project timelines. Due to the quiet nature of a foundation 100 configured as above and its installation process, operations can run uninterrupted, year-round.
- 312 (2) A foundation 100 configured as above may eliminate the expense and exposure of unforeseen geotechnical issues while driving a large monopile, such as boulders, hard sands, soft soils, etc. There is little to no risk involving the installation of a foundation 100 configured as described above, as it can always be removed and repositioned to another site. In contrast, when dealing with a monopile, if the site is deemed unusable once driving begins, the remaining exposed monopile(s) must be cut off and the entire process restarted at new site.
- (3) A foundation 100 configured as above can be used and re-used for all size/variations of wind turbines. As offshore wind continues to progress, rendering older designs obsolete, a foundation 100 configured as above may provide a “plug-and-play” system. Where smaller, previously employed monopiles cannot support the ever-growing turbine system, a foundation 100 configured as set forth above can.
- (4) A foundation 100 configured as above may provide increased lifespan over previously known systems. Because the foundation 100 described herein is formed of a concrete marine mix, it will sustain the harsh saltwater environment for extended time periods, such as 100 years or more. In contrast, current steel monopiles exhibit a 20-to-25-year lifespan.
- (5) Concrete escalation historically rises 3% to 5% annually. Steel prices, on the other hand, are volatile and can double in a year (as was the case in 2021). This volatility is mostly due to supply shortages, controlled by the limited number of manufacturers worldwide. Thus, a foundation 100 configured as above may provide significant cost savings.
- (6) Each cylinder 120 and 130 is preferably cast with its own respective hole size (not shown) at the top, outer wall of the cylinder to supply shelter for marine wildlife. Such differently sized holes for each cylinder will allow diversification for all shapes and sizes of marine life. For example, such holes may be positioned near the very top of the cylinders (e.g., 2-3 feet from the top edge) so as to prevent water from entering the cylinder while floating, and the holes themselves may be, by way of non-limiting example, from 3″ to 20″ in diameter.
- (7) Use of a rebar tower and a Concrete Casting Machine configured as described above allows for the production rates of the cylinders 120 and 130 of foundation 100 to exponentially increase over conventional precast methods and techniques.
- (8) Employing a submersible barge as a delivery mechanism as described above provides added versatility over previously used systems for transporting anchoring elements to an intended windmill installation site. More particularly, upon loadout and delivery, a submersible barge configured as above requires only 16-ft. of draft, until deep enough water is reached (e.g., 35-40 ft.).
- (9) Given the limited amount of equipment and time required onsite for installation, using a foundation 100 configured as above may drastically reduce project timelines and costs.
- (10) Providing a submersible foundation 100 configured as above can meet the requirement for anchoring a windmill (or other structure) while simultaneously providing a wildlife safe haven within the foundation's cylinders.
Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein.
Patent Application
20230340745
