METHOD OF REPAIRING A WIND TURBINE TOWER FOUNDATION USING A HARDENING LIQUID COMPRISING FUNCTIONALIZED GRAPHENE

Abstract

A method for repairing a wind turbine tower foundation, wherein the method comprises steps of providing a hardening liquid comprising functionalized graphene, wherein the hardening liquid has density above water or salt water; introducing the hardening liquid to the wind turbine tower foundation, thereby displacing the water or salt water due to higher density of the hardening liquid; hardening the hardening liquid by resistive heating.

Claims

1. A method for repairing a wind turbine tower foundation having one or more cracks, wherein the method comprises steps of providing a hardening liquid comprising functionalized graphene, wherein the hardening liquid has density above water or salt water; introducing the hardening liquid to one or more cracks of the wind turbine tower foundation, thereby displacing the water or salt water due to higher density of the hardening liquid; hardening the hardening liquid by resistive heating.

2. A method according to claim 1, wherein the wind turbine tower foundation comprises a load carrying concrete structure with an imbedded steel reinforcement connected to a bottom of a wind turbine tower and the step of introducing is along at least part of the imbedded steel reinforcement.

3. A method according to claim 1, wherein the wind turbine tower foundation comprises a mounting element comprising T- and L-flanges and an embedded ring, where the L-flange is connected to the steel tower and constitute the foundation top flange and the step of introducing is along at least part of the T- and L-flanges.

4. A method according to claim 1, wherein the step of providing is performed by mixing a hardening liquid with the functionalized graphene, thereby resulting in a low resistivity hardening liquid.

5. Use of functionalized graphene-containing material in a repair system for wind turbine tower foundations.

6. The use according to claim 5, wherein the use includes resistive heating of the functionalized graphene-containing material during a hardening process of the foundation.

Description

DESCRIPTION OF THE DRAWING

[0338] FIG. 1: Illustration of a wind turbine.

[0339] FIGS. 2A-2C: Illustrations of a wind turbine blade.

[0340] FIGS. 3A-3B: Illustrations of two embodiments of a multi-layered structure.

[0341] FIG. 4: Illustration of a typical foundation for a steel tower for a wind turbine.

[0342] FIG. 5: Illustrating the road map to functionalized graphene-containing material

DETAILED DESCRIPTION OF THE INVENTION

[0343]

TABLE-US-00001 No Item 10 Wind turbine blade 12 Blade structure 14 Wind turbine 20 Shell structure 21 Multi-layered structure 22 Sandwich structure 23 Top layer 24 Intermediate layers 25 Bottom layer 26 Dedicated blade area 27 Functional surface area 28 Surface area 29 Layer thickness 30 Load-carrying spar 40 Functionalized graphene-containing material 41 Tape (film) 42 Graphene-based material 44 Functionalized graphene-based material 46 Host/carrier material 47 Functional layer 48 Functionality 49 Resilient layer 50 Blade root 55 Hub 60 Conductive structure 70 Surface 72 Hydrophobic surface 73 Conductive surface 74 Wear resistant surface 75 Light absorbing surface 76 Surface coating 77 Radar-absorbent surface 80 Wind turbine concrete tower 81 Wind turbine tower 82 Load carrying structure 83 Transition piece 84 Height 85 Nacelle 86 Repair system 88 Tower foundation 90 Sensor containing graphene 91 Rotor 92 Leading edge 93 Tailing edge 94 Suction side 95 Pressure side 100 Use 200 Method 210 Retrofitting 301 Hub height 302 Blade length 310 Soil 312 Mounting element 314 Foundation top flange 400 Method for functionalization

[0344] FIG. 1 illustrates a wind turbine 14 comprising a rotor 91, a nacelle, a tower 80 and foundation 88 for the wind turbine 14. The rotor 91 may comprise the wind turbine blades 10 comprising a blade structure 12, blade roots 50 and a hub 55. The nacelle 85 is illustrated with a cover. The illustrated embodiment comprises a wind turbine concrete tower 80 with a load-carrying structure 82. The load-carrying structure 82 constitutes a top part zone, a middle section zone and a base section zone. The middle section zone and the base section zone may be precast pre-stressed concrete shells. Alternatively the base section zone may be cast in situ. The top part of the tower is illustrated to comprise two sections which may comprise mainly steel elements. The upper section zone includes a transition piece 83. The transition piece 83 may be made in steel with flanges connecting to a yaw system and/or a nacelle 85. The upper section zone may comprise steel tubes or alternatively precast pre-stressed concrete shells.

[0345] The illustrated embodiment presents a hybrid concrete tower, which is referred to as a concrete tower 80 in this invention. The tower has a height 84 and the hub height 301 is illustrated along with the blade length 302. The hub height 301 differs from the tower height 84 by an additional height given by the hub 55.

[0346] FIGS. 2A, 2B and 2C illustrate a wind turbine blade 10. The wind turbine blade 10 comprises a blade structure 12 with a leading edge 92, a tailing edge 93, a suction side 94 and a pressure side 95. The leading edge 92 is that edge of a wind turbine blade 10 that cuts through the air. It is generally that region of the blade 10 which experiences the highest level of erosion.

[0347] The illustrated wind turbine blade 10 comprises a shell structure 20 and a load carrying spar 30. The wind turbine blade further comprises a surface 70.

[0348] In FIG. 2A the load carrying spar 30 is illustrated as a load carrying box. It may also be referred to as a load-carrying box, a main spar, a spar web, a load carrying web, amongst others.

[0349] In FIG. 2B the load carrying spar 30 is illustrated as a single load carrying structure. It may also be referred to as a main spar, a spar web, a load carrying web, amongst others. The blade structure may comprise a hydrophobic surface 72, a conductive surface 73, a wear resistant surface 74, a light absorbing surface 75 and/or a radar-absorbent surface 77. The blade structure may comprise a surface coating 76 which may constitute the surface 70.

[0350] In FIG. 2C the leading edge 92 of a wind turbine blade 10 is illustrated. The leading edge is part of the surface 70. The leading edge 92 is illustrated as two different areas. The extent of the leading edge may depend on the design of the blade and the specifications of the blade. The leading edge 92 may only refer to the outer-most tip part illustrated by the black area or it may extend more towards the rod of the blade illustrated by the black and white area.

[0351] FIG. 3A illustrates a layered structure 21 being a sandwich structure 22 with six layers 12. The layered structure 21 comprises a bottom layer 25, four intermediate layers 24 and a top layer 23. The layers each have individual film thicknesses 29.

[0352] In the illustrated embodiment, the top layer 23 and the intermediate layers 24 all have different functionalities and may accommodate a surface being super environmentally resistant. The top layer 23 provides for a hydrophobic 72 and wear resistant 74 surface. The intermediate layer 24 is a resilient layer 49. This layer's properties of being flexible and/or impact-absorbing may, in combination with the wear resistant top layer, add a further contribution to the wear resistance 74 of the functional surface and thus being super environmentally resistant. This may be due to dampening the impacts of particles inflicting on the surface area. The intermediate layer 24 adjacent to the resilient layer 49 may accommodate a functional layer 47 being light-absorbing 75 and thus, with a reduced light reflectance back to the top layer 23. The intermediate layer 24, adjacent to the light-absorbing layer 75, may be a conductive 73 functional layer 47 accommodating for Joule heating to support a de-icing functionality. The next intermediate layer 24, being the layer between the conductive functional layer 73 and the bottom layer 25 may accommodate an organic solar cell or a photovoltaic. This layer may provide a functionality 48 of delivering power to the Joule heating and thus the de-icing functionality.

[0353] FIG. 3B illustrates a layered structure 21 being a sandwich structure 22 with four layers 12. The layered structure 21 comprises a bottom layer 25, two intermediate layers 24 and a top layer 23.

[0354] In the illustrated embodiment, the top layer 23 and the intermediate layers 24 all have different functionalities and may accommodate a surface being super environmentally resistant. The top layer 23 provides for a hydrophobic 72 and wear resistant 74 surface.

[0355] The intermediate layer 24 adjacent to the top layer 23 is a functional layer 47 being radar absorbent and thus, accommodates for a radar absorbent surface 77. The intermediate layer 24 adjacent to the radar-absorbent layer 77 is also a functional layer. This layer could be absorbent for other wavelengths, be stretchable, add strength to the structure, provide conductive structures amongst others.

[0356] FIG. 4 illustrates an embodiment of a tower foundation 88. The foundation is typically arranged in the soil 310 for on shore wind turbines. A typical foundation 88 for a steel tower for a wind turbine may comprise a mounting element 312 comprising T- and L-flanges and an embedded ring, where the L-flange may be connecting to the steel tower and may constitute the foundation top flange 314.

[0357] In other embodiments, the wind turbine tower foundation 88 may be a load carrying concrete structure with an imbedded steel reinforcement connected to a bottom of a wind turbine tower 81. A wind turbine tower foundation 88 will, due to movement of the wind turbine tower 81, form various cracks and these cracks may be filled with sea water or water. Frost may lead to further damage of the wind turbine tower foundation 88 due to local expansion. These cracks can overtime lead to catastrophic failure causing the entire wind turbine tower 81 to fall.

[0358] The cracks in the wind turbine tower foundation 88 will typically be formed at or around the flanges or the embedded steel reinforcement due to movement of the wind turbine tower 81.

[0359] A hardening liquid comprising functionalized graphene may be used to repair these cracks. Graphene is stronger than steel and efficiently conducts heat and electricity, and it can be functionalized with different side groups for different properties. The number of side groups per carbon atoms may differ depending on the functionalization and/or which properties to achieve.

[0360] Mixing a hardening liquid with functionalized graphene may provide for better electrical conductivity of the hardening liquid and increase the strength of the cured hardening liquid.

[0361] The hardening liquid has a density greater than the density of water or salt water, so when introduced to the one ore more cracks in the wind turbine tower foundation 88, the hardening liquid sinks to the bottom of the crack. Thereby filling the crack with hardening liquid from the bottom to the top of the crack. This result in the water or salt water that may be contained in the crack being pushed out of the crack while and with the same rate as the crack is filled with the hardening liquid. Thereby, the entire crack structure is filled with the hardening liquid, and no residual water is salt water remains in the crack.

[0362] In some embodiments, the hardening liquid may have a density above 997 kg/m.sup.3 or 1020 kg/m.sup.3 or 1029 kg/m.sup.3.

[0363] In some embodiments the hardening liquid comprising functionalized graphene may be a functionalized graphene-containing material 40 with additional strength, additional flexibility, and a viscosity suitable for introduction into the crack. Thereby, the hardening liquid may be easy to introduce in the cracks and may provide strong flexible repairs, that prolong the durability of the wind turbine tower foundation 88.

[0364] In some embodiment, the hardening liquid may be introduced along at least part of the imbedded steel reinforcement or the T- and L-flanges. This may provide a repair with additional strength and additional flexibility. Thereby, repaired cracks may be strong and slightly flexible, where the flexibility may absorb some of the forces from the imbedded steel reinforcement or the flanges induced by the movement of the wind turbine tower 81 preventing new cracks and prolonging the durability of the wind turbine tower foundation 88.

[0365] The functionalized graphene will lower the overall resistivity of the hardening liquid such that the hardening of the hardening liquid is uniform throughout the crack structure. A hardening liquid without functionalized graphene would result in an uneven and superficial hardening while the addition of functionalized graphene enables an in-depth and evenly distributed hardening.

[0366] The low resistivity of graphene is utilised during the step of hardening, where an electric current is passed through the hardening liquid introduces into the crack. The electric current may travel through the hardening liquid from the top to the bottom of the crack, and into all corners of the crack. The passage of an electric current through a conductor such as graphene produces heat, also known as Joule heating, Ohmic heating or resistive heating.

[0367] Passing through the hardening liquid, the incoming electric energy is converted to heat, where heating of the hardening liquid may initiate the curing process of the hardening liquid. Thus, a uniform heating of the hardening liquid uniform throughout the crack structure is obtained, and a uniform hardening of the hardening liquid is achieved.

[0368] FIG. 5 illustrates the roadmap to reach functionalized graphene-containing material 40. Graphene-based material 42 is functionalized using a method or process for functionalization 400 resulting in a functionalized graphene-based material 44. The functionalized graphene-based material 44 is/are mixed with host/carrier material 46 resulting in functionalized graphene-containing material 40.