Precast segment for wind turbine tower and method for building a wind turbine tower using said precast segment

Abstract

Precast segment for wind turbine tower especially designed to be used in wind turbine towers installed in cold climates, and which comprises joint flanges showing a configuration intended to establish the boundaries for forming the joints between said precast segment and an adjacent precast segment and which comprises conduits provided with an inlet and an outlet, situated in the proximity of the joint flanges of the precast segment intended to house some heating cables that generate heat. The method comprises the use of the described precast segment and the stages of introducing heating cables in the conduits of the precast segment, applying current to said cables and removing the cables when a filler material used in the joint between precast segments has set.

Claims

1. A precast segment for wind turbine tower which comprises at least one joint flange configured to establish a boundary to the formation of at least one joint between said precast segment and an adjacent precast segment, where the joint is to be filled with filler material, wherein the precast segment comprises at least one conduit and: the conduit comprises one inlet and one outlet, the conduit is located in the vicinity of the at least one joint flange of the precast segment, and the conduit has a cross section of a similar shape and size to that of the cross section of a heating cable so as to house the heating cable; and wherein the longitudinal direction of the conduits is parallel to the joint flange of the precast segment and the conduits are built with the same curvature as the precast segment and with a radial portion at its ends designed to facilitate the introduction of the heating cable in the conduit through the inlet hole, and the radial portion of the conduits comprises an elbow joint having a curvature large enough to facilitate the insertion and removal of the heating cable.

2. The precast segment of claim 1 wherein the inside of the at least one conduit houses a heating cable.

3. The precast segment of claim 1 wherein the conduit has a coating intended to facilitate the insertion and removal of a heating cable in the conduit.

4. The precast segment of claim 3 wherein the coating of the conduit comprises at least one layer of lubricant material.

5. The precast segment of claim 1 wherein it is made of reinforced concrete and the surfaces which delimit the at least one conduit are made of concrete.

6. The precast segment of claim 1 wherein it is made of reinforced concrete and the at least one conduit is formed by a pipe made of a material with a high thermal conductivity embedded in the concrete of the precast segment.

7. The precast segment of claim 1 wherein the precast segments comprise reinforcements inside and the conduits are joined to said reinforcements.

8. The precast segment of claim 1 wherein the precast segments comprise reinforcements in their interior and the conduits are made of metal and form part of said reinforcements.

9. The precast segment of claim 1 wherein the conduits are blind and the inlet and the outlet coincide.

10. A method for manufacturing a wind turbine tower using precast segments for wind turbine towers wherein the precast segments comprise: at least one joint flange configured to establish a boundary to the formation of at least one joint between said precast segment and an adjacent precast segment using a filler material, at least one conduit provided with one inlet and one outlet, located in the vicinity of the at least one joint flange of the precast segment intended to house a heating cable and at least one heating cable located inside the conduits, wherein the method comprises the following stages: disposing the precast segments adjacent to each other, in such a way that a joint is formed between precast segments, making an electrical current flow through the heating cables, pouring a filler material into the joint between precast segments, removing the heating cables from the conduits through the outlet of the conduits, once the filler material has acquired a sufficient degree of setting.

11. The method of claim 10 wherein it comprises a stage of placing connectors between the ends of the heating cables that are in the conduits allowing the flow of electrical current between said heating cables.

12. The method of claim 10 wherein the conduits used are coated in a lubricant material and the method comprises a stage of removing the conduit from the inside of the precast segment.

13. The method of claim 10 wherein the insertion of the heating cable into the conduit is performed using a lubricant material which facilitates said insertion.

14. The method of claim 10 wherein the method comprises a stage of removing the heating cable from the conduit of one precast segment and a subsequent stage of inserting said heating cable into the conduit of another precast segment.

15. The precast segment of claim 1 wherein the cross section of the conduit and the cross section of the heating cable are circular and wherein the diameter of the cross section of the conduit is slightly greater than the diameter of the cross section of the heating cable.

Description

DESCRIPTION OF THE DRAWINGS

(1) To complement the description and with a view to contributing to a better understanding of the characteristics of the invention in accordance with a preferred example of a practical embodiment thereof, a set of drawings is attached as an integral part of said description wherein, by way of illustration and not limitation, the following has been represented:

(2) FIG. 1a.Shows a close-up plan view of a vertical joint formed between two adjacent precast segments.

(3) FIG. 1b.Shows a view of one of the precast segments which appears in FIG. 1a wherein the conduits can be seen placed in one of its vertical joint flanges.

(4) FIG. 2a.Shows a view of a horizontal joint formed between two adjacent precast segments.

(5) FIG. 2b.Shows a plan view of one of the precast segments that appears in FIG. 2a with the conduits placed in one of its horizontal joint flanges.

(6) FIG. 3.Shows a view of a precast segment with blind conduits wherein the inlet and the outlet coincide and are placed in one of the vertical joint flanges of the precast segment.

(7) FIG. 4.Shows a view of a precast segment with a close-up of a conduit formed by a pipe with fins to increase the thermal conductivity embedded in the concrete.

(8) FIG. 5a.Shows a view of a precast segment with conduits in its vertical flange and a close-up view in which the pipe that forms the conduit, the lubricant material and the heating cable can be appreciated.

(9) FIG. 5b.Shows a view of a precast segment with conduits on its vertical flange as in FIG. 5a but in this one the pipe has been removed.

PREFERRED EMBODIMENT OF THE INVENTION

(10) The present invention describes a precast segment for wind turbine towers installed in zones with cold climates and a method for manufacturing wind turbine towers using said precast segment. The objective of the invention is to allow local heating of the precast segments of the wind turbine tower in the zones of interest to allow a correct setting of the mortar or cement that is poured into the joints between precast segments.

(11) In particular, the invention is especially advantageous in the case of concrete towers, normally built using precast segments made of concrete and a metal reinforcement inside consisting of interwoven steel rods, commonly referred to as reinforcements.

(12) The precast segment of the present invention comprises at least one joint flange (3) which shows a configuration designed to establish a limit to form the at least one joint (4) between said precast segment and a contiguous precast segment using a filler material. The most important characteristic of the proposed precast segment is that it comprises conduits (2) provided with an inlet (9) and an outlet (10), situated in the proximity of the joint flanges (3) and which are designed to house some heating cables (1).

(13) The heating cables are designed to generate heat when an electrical current is made to pass through them.

(14) Said heating cables (1) can form part or not of the precast segment itself and are introduced into the conduits (2) through the inlet (9) and removed through the outlet (10). To facilitate these operations, the conduit (2), the heating cables (1) or both may have a coating (7). Additionally, said coating may comprise at least one layer of a lubricant material (7).

(15) In one embodiment which can be appreciated in FIG. 5.b, the conduits (2) are defined by the concrete itself of the precast segments, and have been left formed in the manufacture of the precast segments by means of the use of inserts.

(16) In one alternative embodiment, the conduits (2) may be pipes (11) of a material with a high structural resistance such as steel for example, which are left embedded in the concrete of the precast segment. In this case, in addition to acting as a housing and guide for the heating cables, they would act as a structural reinforcement of the precast segment itself.

(17) In another embodiment, the conduits (2) are pipes made of a material with a low structural resistance in which case they act only as a housing and a guide.

(18) In addition, the pipes (11) may be made of a material with a high thermal conductivity to boost the effect of the heat that is generated in the heating cables (1) when an electrical current is applied to them. In one preferred embodiment, the conduits (2) comprise on their outer surface a series of fins (12) designed to increase their thermal conductivity.

(19) To manufacture the precast segments the reinforcements are disposed on a mould that is covered with a countermould for subsequently pouring the concrete. In one embodiment, the conduits (2) are formed with inserts. Said inserts are disposed joined to the reinforcements of the precast segment by means of joining elements which are left embedded in it once the concrete has set. Either the inserts or the joining elements or both are rigid, to allow better control of their position with respect to the surfaces of the mould which will define the flanges of the precast segment. This guarantees that the distance from the heating cables to the flanges of the precast segment is always the same.

(20) In the embodiment wherein the conduits (2) are steel pipes (11), these are disposed interwoven with the reinforcements before pouring of the concrete to manufacture the precast segments, in such a way that they form part of said reinforcements. This embodiment is especially advantageous from the point of view of the positioning of the conduits and resistance they confer on the precast segments. Also, their manufacture is simpler, as it is not necessary to carry out any subsequent unmoulding operation as in the case of the previous alternative.

(21) In specific embodiments wherein the precast segments have one of their joint flanges closed, the conduits (2) are blind and the inlet (9) coincides with the outlet (10).

(22) In one embodiment of the invention that works with vertical joints, the conduits (2) are built in a vertical direction, parallel to the vertical joint flange (3) of the precast segment (6). In another embodiment that works with horizontal joints, the conduits (2) are built in a horizontal direction, parallel to a horizontal joint flange (3) of the precast segment (6).

(23) In another embodiment, the conduits (2) are built with the same curvature as the precast segment (6) and with a radial portion (8) at its ends designed to facilitate the introduction of the heating cable (1) into the conduit (2) through the inlet hole (9). In this case, the radial portion (8) of the conduits (2) comprises an elbow joint having a curvature large enough to facilitate the insertion and removal of the heating cable (1).

(24) Likewise, an object of the present invention is a method for manufacturing a wind turbine tower using the precast segments described above which allow working even when the ambient temperature is below 5 C. This is a simple manufacturing method which does not make more expensive the wind turbine concrete towers that are manufactured with it. Heating cables are used to heat the area of the joint between precast segments and allows said heating cables to be placed quickly and easily with respect to the joint of the precast segments.

(25) The proposed method for manufacturing wind turbine towers comprises the use of precast segments such as the ones described above which incorporate at least one heating cable (1) inside the conduits (2). The method comprises a step of disposing the precast segments (6) adjacent to each other, in such a way that a joint (4) is formed between precast segments. Subsequently, an electrical current is made to flow through the heating cables (1), pouring a filler material into the joint between precast segments (6), and finally to remove the heating cables (1) from the conduits (2) through the outlet (10) of the conduits (2), once it has acquired a sufficient degree of setting.

(26) The stage of applying current to heat the precast segments (6) before pouring the filler material is carried out during sufficient time for the precast segments (6) to reach a temperature of more than 5 C. After pouring the filler material, the current continues to be applied to the heating cables until the filler material of the joint has acquired a sufficient degree of setting (understood the level of setting at which the filler material has a necessary minimum mechanical resistance capacity for the joint that encloses it). The time required for this will depend on at least the ambient temperature and the type of filler material. In the proposed method the minimum time for which it is necessary to apply current after pouring the filler material is characterised in dependence with the filler material employed. This time may be several hours, and may even exceed 24 hours when the filler material employed is mortar.

(27) The method described in the present invention may comprise an additional stage of placing connectors (5) between the ends of different heating cables (1) that are located in the conduits (2) to allow the flow of current between said heating cables (1) and carry out the connection to a power supply box for said heating cables (1). When a heating cable (1) is placed in each conduit (2) it is possible to use these connectors (5) to establish the electrical connections between the heating cables (1) in such a way that the current is conducted between the heating cables (1) to reduce the number of connections to the power equipment.

(28) Thanks to the conduits (2) built inside the precast segments (6), the placing of the heating cables (1) with respect to the joint flanges (3) which form the joints (4) is done quickly and easily. It is only necessary to introduce the heating cables (1) through the inside of said conduits and when they have already been used to heat the mortar poured into the joints (4) and these have already set correctly, the heating cables (1) are extracted from the conduits (2). Therefore, the same heating cables (1) can be used in the manufacture of several wind turbine towers which helps to reduce manufacturing costs.

(29) It must be taken into account that the conduits (2) must be free of right angles as otherwise, introduction and extraction of the heating cable (1) is more complex.

(30) In one preferred embodiment, the conduits located close to the flanges that define the vertical joints are blind and the inlet (9) and outlet (10) coincide such that insertion and removal of the cables is done through just one point. Preferably, the conduits are blind and straight, without changes in direction. In this way, the stage of insertion is even easier. In another embodiment, the inlet and outlet of the conduits (2) close to the flanges that define the vertical joints are through-holes. In this way, not only extraction of the heating cables is made easier, but also their insertion in another precast segment for subsequent use thereof.

(31) For the described manufacturing method it may be necessary to use connectors (5) to drive current to each heating cable (1) from power supply equipment.

(32) Generally, the precast segments (6) used in the method for manufacturing wind turbine towers made of concrete have reinforcements inside. In these cases, the method comprises a stage of joining the pipes for manufacturing the conduits to the reinforcements.

(33) When using pipes with a high structural resistance they are preferably embedded in the precast segment and act as a structural reinforcement of the precast segment (6) as well as being the conduits (2) intended to receive the heating cables (1). In a preferred embodiment, the pipes of a high structural resistance are made of metal, preferably steel.

(34) Likewise, the pipes may be made of material with a low structural resistance, such as plastic for example. The difference with respect to the preceding embodiment is that in this case the conduits (2) do not act as a structural reinforcement, their only function is to allow passage and guiding of the heating cables (1) through them, however, because they are low cost and are embedded in the concrete they constitute an efficient option for the heating system.

(35) In another embodiment of the invention, the inserts used for the construction of the conduits (2) are coated with a lubricant material and the method comprises a stage of removing the conduit (2) from the interior of the precast segment (6).

(36) These inserts are placed before pouring the mortar and simply removed after the mortar has set thanks to the lubricant material. This embodiment entails a lower requirement of material for the placing of the heating cables as the inserts which are used to form the conduits (2) can be reused in several towers and/or precast segments.

(37) When the manufacturing method is used to manufacture wind turbine towers which have vertical joints, the conduits (2) are built in a vertical direction, parallel to a vertical joint flange (3) of the precast segment (6). This example is illustrated in FIG. 2. In this specific case, a vertical joint can be appreciated in the end of one precast segment. Said joint is surrounded by a plurality of conduits (2) where the heating cable (1) is introduced.

(38) When the method is used to manufacture wind turbine towers which have horizontal joints, the conduits (2) are built in a horizontal direction, parallel to a horizontal joint flange (3) of the precast segment (6). This embodiment is represented in FIG. 3.

(39) Additionally, when two precast segments (6) are being joined with horizontal joints, the conduits (2) are built with the same curvature as the precast segment (6) and with a radial portion (8) at its ends intended to facilitate the introduction of the heating cable (1) into the conduit (2). This can also be appreciated in FIG. 3.

(40) The insertion of the heating cable (1) in the conduit (2) is performed using a lubricant material (7) which facilitates said insertion.

(41) Likewise the method can comprise some final stages of removing the heating cable (1) from the conduit (2) of a precast segment (6) and subsequently introducing said heating cable (1) into the conduit (2) of another precast segment (6).