WO2014207528A1

WO2014207528A1 - Static testing of wind turbine blades

Info

Publication number: WO2014207528A1
Application number: PCT/IB2014/001109
Authority: WO
Inventors: Bipinkumar Nathalal LUNAVIA; Yogesh Jogindernath MEHRA
Original assignee: Lunavia Bipinkumar Nathalal; Mehra Yogesh Jogindernath
Priority date: 2013-06-26
Filing date: 2014-06-19
Publication date: 2014-12-31

Abstract

The present subject matter relates to static testing of wind turbine blades. In one embodiment, a testing apparatus (100) for static testing of a wind turbine blade (302) is described. The testing apparatus (100) comprises a base (102), and a platform (104) vertically above the base (102) and supported by the base (102). The platform (104) being adapted to support a rotor assembly (300) comprising a rotor hub (200), at least one wind turbine blade (302) mounted to the rotor hub (200), and at least one actuator adapted to actuate the at least one wind turbine blade (302) about a longitudinal axis of the at least one wind turbine blade (302) into a plurality of testing positions.

Description

STATIC TESTING OF WIND TURBINE BLADES

TECHNICAL FIELD

[0Q01] The present subject matter relates, in general, to wind turbines and, in particular, to static testing of the wind turbine blades.

BACKGROUND

[0002] Wind turbines generate electricity by transforming kinetic energy of wind into electrical energy. Major components of a wind turbine include a generator, a tower, and a rotor. The rotor further includes blades that are employed to convert the kinetic energy of wind into mechanical energy which is then converted into electricity by the generator. With the increasing demand for renewable energy, wind turbine designers are working to provide blade designs that allow the wind turbines to effectively convert wind into electricity. Once designed, the blades have to be tested in order to ensure that their specifications are consistent with the actual performance of the blade. The fundamental purpose of a blade test is to demonstrate, up to a reasonable level of certainty, that a blade type, when manufactured according to a certain set of specifications, possesses the strength and service life that the blade is designed for.

[0003] Current techniques for testing the wind turbine blades involve performing different tests on the blades to assess the load-bearing ability of the blades. One of the important tests is the static test which is used to predict the ability of the blade to withstand extreme loads, such as those caused by hurricane wind forces or unusual transient conditions, in order to determine an ultimate strength of the blade. Full-scale static testing of the blades is usually performed for certification of a new blade design and is important for detecting defects or inadequacies in a blade's manufacture.

SUMMARY

[0004] This summary is provided to introduce the concepts related to static testing of the wind turbine blades. These concepts are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter. l [0005] According to one embodiment, a testing apparatus for static testing of a wind turbine blade is described. The testing apparatus comprises a base, and a platform vertically above the base and supported by the base. The platform being adapted to support a rotor assembly comprising a rotor hub, at least one wind turbine blade mounted to the rotor hub, and at least one actuator adapted to actuate the at least one blade about a longitudinal axis of the at least one blade into a plurality of testing positions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0007] Figure 1 illustrates a testing apparatus, in accordance with an embodiment of the present subject matter.

[0008] Figures 2(a)-2(d) illustrate perspective views of the testing apparatus, in accordance with an embodiment of the present subject matter.

[0009] Figure 3 illustrates a top view of the testing apparatus in a testing environment, in accordance with an embodiment of the present subject matter.

[0010] Figure 4 illustrates a side view of the testing apparatus in a testing environment, in accordance with an embodiment of the present subject matter.

[0011] Figure 5 illustrates the testing apparatus in a testing environment, in accordance with another embodiment of the present subject matter.

[0012] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views illustrative of the testing apparatus for static testing of the wind turbine blades embodying the principles of the present subject matter.

DETAILED DESCRIPTION

[0013] As fossil fuels become scarcer and more expensive to extract and process, energy producers and users are becoming increasingly interested in other forms of energy. One such energy form that has seen resurgence is wind energy. Wind energy is typically harvested by placing a multitude of wind turbines in geographical areas that tend to experience steady, moderate winds. Modern wind turbines typically include an electric generator connected to one or more wind-driven turbine blades, which rotate about a vertical axis or a horizontal axis.

[0014] Recent developments in the wind turbines are constantly driven towards obtaining higher power outputs. Several attempts have been made to maximize the power output. However, such attempts have resulted in an increased size of the components of the wind turbine. An example of one of such components is the blade of the wind turbine; since the larger wind turbine blades are considered to produce energy more efficiently than the smaller blades. The wind turbine blades have become dramatically large over the last few years as manufacturers strive to extract as much energy as possible with a given wind turbine. Accordingly, the equipment for testing the wind turbine blades has become progressively large, expensive, and cumbersome to use. To accommodate such testing equipments, separate testing facilities have been built that are limited in number and usually located in remote locations. The testing facilities are equipped with rigid fixed structures commonly referred as testing jigs, load application equipments, such as ballistic weights or hydraulic actuators, loading cables, various fixtures, sensors, controllers, and measurement systems.

[0015] Once designed and manufactured, the wind turbine blades are tested in such testing facilities using different testing techniques. One such technique is static testing, which is performed to assess the safety and strength characteristics of the wind turbine blades. To perform the static testing, pre-testing setup is required to be made at the testing facilities. The setup involves fixing the root of the wind turbine blade under testing to the testing jig, mounting fixtures to the blades, fixing loading cables to the fixtures and the metallic structures mounted on the floor of the testing facility, mounting load measurement devices with the loading cables, and disposing sensors to measure strains and deflections on the wind turbine blade (interchangeably referred to as a blade).

[0016] When the setup is ready, static testing is performed by applying load to the blade using the load application equipments. Conventional load application equipments include electric winches, hydraulic actuators, or ballast weights that are hanged from the blade at specified locations. The loads are applied to the blade at predetermined locations along the length of the blade. Such locations are usually referred to as loading points. The load applied to the blade is measured using load measurement devices, such as load cells. The ultimate static test is applying load to the blade till the point of failure of the blade. Subsequent to the application of the loads, blade deflection and strains on the blade are measured using the sensors disposed on the wind turbine blade. The measured data is later analyzed to determine the blade strength and the load-bearing capacity of the wind turbine blade.

[0017] Said testing process is performed in various testing positions of the wind turbine blade and at various loading points on the wind turbine blade. For example, the testing can be performed at flaps of the wind turbine blade and edges of the wind turbine blade, where each of the flaps and each of the edges of the wind turbine blade correspond to a loading point. After completing the testing of the wind turbine blade in one testing position, the wind turbine blade is disassembled, i.e., unbolted from the fixed testing jig, rotated to another testing position for testing the wind turbine blade in the another testing position. Subsequently, the blade is re-assembled, i.e., bolted to the testing jig. This process of disassembling and reassembling the wind turbine blade in conventional static testing is an iterative process, and is time consuming. Moreover, handling of the wind turbine blades during the disassembly or re-assembly is difficult, and involves extensive labor as the wind turbine blades are typically large and heavy.

[0018] Further, as stated above, conventionally, the static testing is carried out in testing facilities that are generally limited in number and located remotely. With the limited testing facilities and need of transporting ihe blades to these testing facilities to carry out the testing, significant delay occurs in the testing process. For example, according to the conventional testing methodology, the static testing process typically takes around 1-2 weeks to complete. Moreover, the transportation of large wind turbine blades to these testing facilities is difficult, costly, and resource intensive.

[0019] In accordance with the present subject matter, a testing apparatus for performing static testing of the wind turbine blade is described. The testing apparatus described herein is portable, and flexible to use for the static testing of the wind turbine blades. Further, the testing apparatus described herein reduces the overall time taken to complete the static testing. [0020] According to one embodiment, the testing apparatus comprises a base and a platform vertically above the base to support a rotor assembly thereon. The rotor assembly referred herein includes a rotor hub having at least one wind turbine blade mounted therewith, one or more actuators for rotating the wind turbine blade about the longitudinal axis of the blade. According to one embodiment, the plane of the platform supporting the rotor assembly is inclined with respect to a horizontal plane of the base. The inclination being measured in a plane perpendicular to the plane of the platform.

[0021] Weight of the rotor assembly is much more than the weight of the testing apparatus. To enable the testing apparatus to maintain the balance when the rotor assembly is placed thereon, the testing apparatus is further provided with a carrier extending horizontally from the base to carry a counterweight to the rotor assembly. The counterweight may be concrete blocks of weight sufficient to counter the weight of the rotor assembly.

[0022] The manner in which the static testing is carried out using the testing apparatus is described in the forthcoming description. Before describing the method of performing the static testing, a brief description of the process of setting up the testing environment is provided below.

[0023] The process of setting up the testing environment involves placing the rotor assembly onto the platform of the testing apparatus. Subsequent to placing the rotor assembly, the rotor assembly, in one implementation, can be fixed to the platform using a fastening element, such as bolts.

[0024] Further, at predetermined loading points along the length of the blade, a plurality of fixtures is mounted. A first end of a loading cable is subsequently tied to each of the fixtures, while a second end of the loading cable is tied to the columns present in the testing environment, such as a factory wall or a manufacturing site. The load application arrangement is then made using a conventional load application system. For example, the hydraulic actuators are arranged for applying the load, or ballistic weights can be used for hanging from the loading cable passing through the columns. A load cell is placed between each of the fixtures and the columns for measuring the load applied to the blade. Further, a plurality of sensors is disposed on the blade to measure strains, deformations, and deflections on the blade during the testing process.

[0025] Subsequent to setting up the testing environment, the testing is carried out by applying load at each of the loading points along the length of the blade. The loading points and loads to be applied thereon are predetermined by, say, the blade designers upon performing buckling analysis of the blade prior to the testing. For example, starting loads and ultimate loads to be applied at different loading points on the blade are predetermined by the blade designers. For applying the load, any conventional mechanism, such as hydraulic actuators, ballistic weights, etc., can be utilized. In an implementation, while testing, a different load is applied at each loading point. For example, if the load is to be applied at three predetermined locations, load X is applied at the first location, load X+Y is applied at the second location, and load X+Z is applied at the third location.

[0026] The testing process is carried out at various loading points, for example, flaps and edges of the blade. In one testing position, starting loads are applied at the loading points on the blade. In subsequent cycles, the loads at the loading points are increased slowly up to the respective ultimate loads predetermined for the blade. The load can be held for predefined time at the loading point and can be released slowly thereafter. During the process, measurement of strain, deflection, or deformations of the blade is performed by the sensors disposed on the blades, and the measured data is analyzed to determine strength and load bearing capacity of the blade. The same testing process is repeated for other testing positions. According to the present subject matter, once the blade is tested at one testing position, moving to the other testing position can be achieved by rotating the blade about its longitudinal axis using the actuators.

[0027] The testing apparatus, thus, facilitates the rotation of the blades without the need of disassembling and reassembling the blades at the testing apparatus, thereby reducing the total time required for testing the blades. Further, the testing apparatus described herein is portable and, therefore, testing can be performed at a testing environment at a manufacturing site, thereby eliminating the need of transporting the blades to the test facilities. Further, the testing apparatus reduces overall time taken to complete the static testing. For example, the testing process can be completed within 4- 5 hours after completing the testing set-up with the testing apparatus described herein.

[0028] Although the testing apparatus, in accordance with the present subject matter, has been described for use in the static testing of the wind turbine blades, such a testing apparatus can also be utilized for the fatigue testing of the wind turbine blades with few modifications that will be apparent to a person skilled in the art.

[0029] Specific details of several embodiments of the apparatus and the method for performing the static testing on the blades are described below with reference to particular testing components and associated procedures. In other embodiments, the components and associated methods can have other arrangements. Several details describing structures and processes that are well-known and often associated with static testing, but that may unnecessarily obscure some significant aspects of the disclosure, are not set forth in the following description for purposes of clarity. Moreover, although the following disclosure sets forth several embodiments of different aspects of the present subject matter, several other embodiments can have different configurations or different components than those described in the forthcoming section. As such, the present disclosure and associated technology can encompass other embodiments with additional elements and/or other embodiments without several of the elements described below with reference to Figures 1-5.

[0030] Figure 1 illustrates the testing apparatus 100, in accordance with an embodiment of the present subject matter. The testing apparatus 100 includes a base 102 and a platform 104 vertically above the base and adapted to support a rotor assembly (not shown). The rotor assembly referred herein comprises a rotor hub having at least one blade mounted therewith, and one or more actuators to rotate the blade about the longitudinal axis of the blade. In one implementation, each of the one or more actuators 105 may be an electric pitch motor/actuator. The testing apparatus 100 shown in the figure can be a test bench made up of a metallic material. In an implementation, the plane of the platform 104 supporting the rotor assembly is inclined, say by around 10 degree, with respect to a horizontal plane of the base 102 to provide ground clearance while performing the static testing on the flaps of the wind turbine blade as the flapwise testing may lead to deflection of the blade tip by, for example, 4 to 5 meters. The inclination is being measured in a plane perpendicular to the plane of the platform. By designing the inclined platform, a ground clearance of approximately 4 meters is achieved.

[0031] The blade referred herein may, in general, be any kind of blade of a wind turbine. In the context of the present subject matter, the term blade refers to a complete blade or a portion of the blade (also otherwise referred to as blade segment). The blade may be. provided with a flange by which the blade is connected to the rotor hub of the wind turbine. In one implementation, the rotor assembly can be fixed to the platform 104 by a fastening element. As an example, the rotor assembly can be bolted onto the platform 104. The testing apparatus 100 further comprises a carrier 06 for carrying a counterweight 108 used for establishing a counter balance with the rotor assembly. In an example, the counterweight 108 may be concrete-filled pipes or concrete blocks that are placed onto the carrier 106 for maintaining the balance of the carrier 106 supporting the rotor assembly which is heavier in weight. The balanced testing apparatus can thereafter be utilized for testing of the blade. In one implementation, the counterweight 108 to be placed on the carrier may be predetermined according to the weight of the rotor assembly.

[0032] Figures 2(a)-2(d) illustrate perspective views of the testing apparatus 100, in accordance with an embodiment of the present subject matter. Specifically, figure 2(a) illustrates a front view of the testing apparatus 100 supporting a rotor hub 200 of the rotor assembly, figure 2(b) illustrates a left view of the testing apparatus 100 supporting the rotor hub 200, figure 2(c) illustrates a top view of the testing apparatus 100 supporting the rotor hub 200, and the figure 2(d) illustrates a isometric view of the testing apparatus 100 supporting the rotor hub 200.

[0033] According to one embodiment, the base 102, the platform 104, and the carrier 106 may be designed in a rectangular shape. The base 102 may be of about 2000 millimeter (mm) in length and 2000 mm in width, the platform 104 may be of about 1500 mm in length and 1500 mm in width, and provided at about 000 mm upwardly from the base 102, the distance being measured in a vertical direction. The carrier 106 may be of 2500 mm in length and 2000 mm in width. [0034] It is to be understood that the embodiment described above should not be construed as a limitation, the base 102, the platform 104, and the carrier 106 of the testing apparatus 100 can be designed in any other shape or size suitable to perform the above mentioned functions, and can be made up of any suitable material with which strength as well as portability of the testing apparatus 100 can be achieved. Further, the base 102, the platform 104, and the carrier 106 described herein can have a variety of other possible arrangements not described herein for the sake of simplicity.

[0035] Figure 3 illustrates a top view of the testing apparatus 100 in a testing environment, in accordance with an embodiment of the present subject matter, and Figure 4 illustrates a side view of the testing apparatus 100 in a testing environment, in accordance with an embodiment of the present subject matter.

[0036] As shown in the Figure 3, in operation, the platform 104 carries the rotor assembly 300. The rotor assembly 300 includes a rotor hub 200 and a wind turbine blade 302 connected thereto. In one implementation, the rotor assembly 300 can be fixed to the platform 104 via fastening elements, such as bolts (not shown). Further, a plurality of fixtures 304 can be mounted to the blades at predetermined loading points 306 along a length of the wind turbine blade 302. Further, loading cables 308 can be tied to these fixtures 304 at one end and to columns 310 at another end, for fixing the wind turbine blade 302 for testing. As shown in Figure 3, the columns 310 can be mounted on a rigid structure, such as a factory wall at another end.

[0037] According to another embodiment illustrated in Figure 4, the columns 310 are mounted on a floor. The columns 310 depicted herein may be a pulley carrying a loading cable 308. In addition, load cells 312 are mounted in between the fixtures 304 and the columns 310 for controlling the load to be applied on the blade during the testing procedure. Further, in an implementation, a safety steel mesh can be provided below the blade 302, to protect the blade 302 in case of an accident, say in case the loading cables 308 accidentally buckle and the blade 302 is dismounted.

[0038] During the testing process, the loads are applied at different loading points 306 along the length of the wind turbine blade 302. In one implementation, a controller (not shown) can be provided to control the load cells 312 for applying the loads. The controller can include a processor, a memory, and/or other features, for example, input/output features. The controller can be configured to control the loading cells 312 and regulate the maximum load to be applied on the wind turbine blade 302 during testing. Accordingly, for example, the controller can be programmed with instructions to coordinate the actions of the loading cells 312 to avoid subjecting the blade 302 to unbalanced loads. The controller can also receive data from the sensors disposed on the blade 302. For example, the controller can be configured to receive data related to strains, deformations and deflections on the wind turbine blade 302 for assessing the strength and load bearing capacity of the wind turbine blade 302.

[0039] The method for static testing of the wind turbines blades 302 performed using the testing apparatus 100 illustrated in the above mentioned embodiments include applying a predetermined load at each of a plurality of loading points 306 along the length of the wind turbine blade 302. The wind turbine blade 302 is mounted to the rotor hub 200 placed on the testing apparatus 100. In an implementation, the load applied at each of the loading points 306 is different. In an example, the loading points 306 and loads to be applied thereon are predetermined by the blade designers upon performing buckling analysis of the wind turbine blade 302. For instance/starting loads and ultimate loads to be applied at different loading points 306 on the wind turbine blade 302 are predetermined based on buckling analysis. Initially, starting loads are applied at the loading points 306. Subsequently, the loads at the loading points 306 are increased slowly up to the ultimate loads.

[0040] The load applied at the loading points 306 is then released slowly. Before being released, constant load can be applied for a predefined time at each of the loading points 306 and subsequently released gradually. The predefined time may be decided by the blade designers, or a tester, depending upon the design of the wind turbine blade 302.

[0041] During the testing process, strains and/or deflections that the wind turbine blade 302 undergoes during loading and unloading are measured, for each testing cycle, using the sensors disposed on the wind turbine blade 302. The measured data is thereafter analyzed either manually or by a controller to determine the strength of the wind turbine blade 302 and the load bearing capacity of the wind turbine blade 302. [0042] The above mentioned testing process is performed on the wind turbine blade 302 at various testing positions. For example, once the above mentioned steps are performed with the wind turbine blade 302 in one testing position, the wind turbine blade 302 is then tested in another testing position. Moving from one testing position to the other testing position can be achieved by rotating the wind turbine blade 302 to about the longitudinal axis of the wind turbine blade 302 using actuators 105, thereby eliminating the need of disassembling and reassembling the wind turbine blades 302 from the testing apparatus 100.

[0043] Figure 5 illustrates the testing apparatus in a testing environment, in accordance with another embodiment of the present subject matter. The testing apparatus 100 comprises a base 102 and a platform 104 vertically above the base 102 and adapted to support a rotor assembly 300. The rotor assembly 300 referred herein comprises a rotor hub 200 having at least one wind turbine blade 302 mounted therewith, and at least one actuator 105 to rotate the wind turbine blade 302 about the longitudinal axis of the wind turbine blade 302. According to said embodiment, the plane of the platform 104 supporting the rotor assembly 300 is inclined, say by around 10 degree, with respect to a vertical plane of the base 102. The inclination being measured in a plane parallel to the plane of the platform 104. Further, the platform 104 is adapted to be mounted to a blade adaptor 500 on the rotor assembly 300. The blade adaptor 500 may be a flange, in one implementation.

[0044] The platform 104 can be mounted to the rotor assembly 300 by fixing the ^' platform 104 to the blade adaptor 500 through fastening elements, say bolts. The platform 104 is designed to support the rotor assembly 300. Additionally, a stand 502 can be provided as an additional support to the rotor assembly 300. The testing apparatus 100 according to said embodiment further comprises a carrier 106 for carrying a counterweight 108 used for establishing a counter balance with the rotor assembly 300.

[0045] Although the subject matter has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. It is to be understood that the appended claims are not necessarily limited to the features described herein. Rather, the features are disclosed as embodiments of the testing apparatus 100.

Claims

We claim:

1. A testing apparatus (100) for static testing of a wind turbine blade (302), the testing apparatus (100) comprising:

a base (102); and

a platform (104) vertically above the base (102) and supported by the base (102), wherein the platform (104) is adapted to support a rotor assembly (300), and wherein the rotor assembly (300) comprises a rotor hub (200), at least one wind turbine blade (302) mounted to the rotor hub (200), and at least one actuator (105) adapted to actuate the at least one wind turbine blade (302) about a longitudinal axis of the at least one wind turbine blade (302) into a plurality of testing positions.

2. The testing apparatus (100) as claimed in claim 1 , wherein the testing apparatus (100) further comprises a carrier (106) adapted to carry a counterweight (108) for establishing a counter balance with the rotor assembly (300).

3. The testing apparatus (100) as claimed in claim 1 , wherein the testing apparatus (100) is portable.

4. The testing apparatus (100) as claimed in claim 1 , wherein a plane of the platform (104) is inclined with respect to a horizontal plane of the base (102), the inclination being measured in a plane perpendicular to the plane of the platform (104).

5. The testing apparatus (100) as claimed in claim 1 , wherein a plane of the platform (104) is inclined with respect to a vertical plane of the base (102), the inclination being measured in a plane parallel to the plane of the platform (104).

6. The testing apparatus (100) as claimed in claim 1 , wherein the platform (104) is fixed to a blade adaptor (500) of the rotor assembly (300) by fastening elements.

7. The testing apparatus (100) as claimed in claim 1 , wherein the wind turbine blade (302) is connected to loading cables (308) and load cells (312) through fixtures (304) mounted at a plurality of loading points (306) on the wind turbine blade (302).

8. The testing apparatus (100) as claimed in claim 7, wherein the -plurality of loading points (306) include flaps and edges of the wind turbine blades (302).

9. A method for static testing of a wind turbine blade (302) using the testing apparatus (100) as claimed in claim 1 , the method comprising:

performing a static testing of the wind turbine blade (302) at the plurality of testing positions, wherein the at least one wind turbine blade (302) is actuated about the longitudinal axis of the at least one wind turbine blade (302) into the plurality of testing positions using the at least one actuator (105).

10. The method as claimed in claim 9, wherein the method further comprises:

placing a counterweight (108) on a carrier ^106) of the testing apparatus (100) for establishing a counter balance with the rotor assembly (300).