WO2018103916A1

WO2018103916A1 - Determining a structural condition of a rotor blade of a wind turbine

Info

Publication number: WO2018103916A1
Application number: PCT/EP2017/075744
Authority: WO
Inventors: Eric S. KNUDSEN; Martin Leong
Original assignee: Siemens Wind Power AS
Current assignee: Siemens Gamesa Renewable Energy AS
Priority date: 2016-12-05
Filing date: 2017-10-10
Publication date: 2018-06-14
Anticipated expiration: 2019-06-05

Abstract

A method is proposed for determining a structural condition of a rotor blade (100) of a wind turbine, comprising the following steps: – monitoring at least one optical characteristic inside at least a part of the rotor blade (100), - determining the structural condition of the rotor blade (100) based on the monitored at least one optical characteristic. Further, a wind turbine, a rotor blade and a device as well as a computer program product and a computer readable medium are suggested for performing said method.

Description

Determining a structural condition of a rotor blade of a wind turbine

The invention relates to a method, a wind turbine, a rotor blade and to a device for determining a structural condition of a rotor blade of a wind turbine. In addition, an according computer program product and a computer readable medium are suggested.

Monitoring and/or determining a structural condition or structural health of rotor blades of a wind turbine like, e.g., detection of damages at the rotor blade is a challeng- ing task due to specific requirements related to costs and robustness of such kind of monitoring systems.

Damages like, e.g., cracks being present on a surface or skin of a rotor blade of a wind turbine may lead to severe damage of the rotor blade - in worst case a total loss of the rotor blade may be the consequence.

Detection of such kind of damages may be based on a visible inspection by service personal which is time- and cost- intensive.

Another approach for damage detection may be based on monitoring changes in the natural frequencies of the blade struc^¬ ture ("frequency response solution") in order to detect de- veloping damage. Thereby, one challenge is that it takes a significant amount of damage to change the frequency response of a blade. As a consequence, frequency response solutions might not detect damages before total loss of the rotor blade .

Damage detection of rotor blades may be also based on captur^¬ ing acoustic emissions by using several microphones distrib^¬ uted inside the blade and being arranged to detect sound of cracking structure ("acoustic damage detection") . As a poten^¬ tial drawback, a crack of a certain magnitude has to develop before being detected by acoustic damage detection. As a fur^¬ ther disadvantage, cracks propagating in fatigue may not be detected by microphones as they do not generate significant noise emission.

The object is thus to overcome the aforementioned disad^¬ vantages and in particular to provide an improved approach for monitoring and/or determining structural condition of a rotor blade of a wind turbine.

This problem is solved according to the features of the inde^¬ pendent claims. Further embodiments result from the depending claims.

In order to overcome this problem, a method is provided for determining a structural condition of a rotor blade of a wind turbine, comprising,

- monitoring at least one optical characteristic inside at least a part of the rotor blade,

determining the structural condition of the rotor blade based on the monitored at least one optical characteris^¬ tic.

Determining a structural condition of a rotor blade may be, e.g., determining or monitoring structural health of a rotor blade like, e.g., detecting any kind of damage of the rotor blade, in particular at the surface or shell of the rotor blade. Based on the proposed solution, any kind of damage comprising one or more holes or cracks at the surface or shell of the rotor blade causing any kind of light or optical radiation or brightness passing through the damage towards an interior of the rotor blade can be determined.

Optical characteristic may be any kind of characteristic which may be captured by an optical sensor. As an example, intensity of light may be captured by the optical sensor. Examples of optical sensors are:

- photo resistors

- photodiodes

- any other kinds of electro-optical sensors

The monitoring of the optical characteristic may be limited to or may focus on a specific part of the wind turbine. Al^¬ ternatively the monitoring may focus on the whole structure of the rotor blade. Thereby, a number of optical sensors may be distributed in the rotor blade structure, e.g., along a main shear web of the rotor blade depending on the sensitivity of the sensors and dependent on the desired degree of structure monitoring.

Monitoring an optical characteristic may be capturing an op^¬ tical characteristic, e.g., by use of an optical sensor. Mon^¬ itoring may also comprise measuring the captured optical characteristic like, e.g., measuring an amount or value of the optical characteristic, e.g., an amount or value of cap^¬ tured intensity of light. The resulting amount or value of the optical characteristic may be processed further on being the basis of a respective control of the wind turbine. The captured and/or measured optical characteristic may be converted into information representing the captured and/or measured optical characteristic.

The information may be interpreted as a condition and/or a change of the condition in the rotor blade structure.

The information may be established as a signal suitable to be provided via any kind of transmission medium. The information may be an analog or digital information.

Signal may be an electrical or optical signal or a wireless signal . In an embodiment, the structural condition is determined based on a change of at least one of the monitored at least one optical characteristic inside the rotor blade.

In another embodiment, the at least one optical characteris^¬ tic is monitored by using at least one optical sensor located inside the rotor blade capturing and/or measuring the at least one optical characteristic and converting the captured and/or measured at least one optical characteristic into at least one information representing the captured and/or measured at least one optical characteristic wherein the at least one information is provided via at least one transmission me^¬ dium .

Examples of a transmission medium may be an electrical or op^¬ tical line or a wireless transmission medium.

The at least one information may be provided or forwarded via the transmission medium to a central control unit (also re^¬ ferred as "interrogator") comprising a processing unit processing or analyzing the received at least one information. Based on the outcome of the analysis, the structural condi^¬ tion of the respective rotor blade may be determined by the control unit.

In a further embodiment,

- the at least one optical characteristic is a light intensi^¬ ty, and

- the information provided is representing an amount or value of the light intensity captured and/or measured by the at least one optical sensor.

In a next embodiment, a damage of the rotor blade is detected in case of an increase of the provided amount or value of the light intensity. It is also an embodiment that the wind turbine is operated dependent on the determined structural condition of the rotor blade . As an example, in case of a change of the monitored optical characteristic, i.e. in case of a detected damage of the ro^¬ tor blade, the power production of the wind turbine might be reduced or a complete shutdown of the wind turbine will be initiated. Further, the damage may be reported, e.g., to a service station of a wind farm or to a control station con^¬ trolling remotely the respective wind turbine.

The problem stated above is also solved by a wind turbine comprising

- at least one rotor blade comprising at least one optical sensor located inside the rotor blade,

- the at least one sensor is arranged to capture and/or measure at least one optical characteristic inside at least a part of the rotor blade,

- a processing unit that is arranged for

- monitoring the at least one captured and/or measured op^¬ tical characteristic inside the rotor blade,

- determining the structural condition of the rotor blade based on the monitored at least one optical characteris^¬ tic.

The problem stated above is also solved by a rotor blade suitable for being used in a wind turbine as described here^¬ in, comprising

- at least one optical sensor located inside the rotor blade, wherein the at least one sensor is arranged to capture and/or measure at least one optical characteristic inside at least a part of the rotor blade,

- at least one transmission medium for providing information generated by the at least one optical sensor.

The problem stated above is also solved by a device compris^¬ ing and/or being associated with a processing unit and/or hard-wired circuit and/or a logic device that is arranged such that the method as described herein is executable there^¬ on . Said processing unit may comprise at least one of the follow^¬ ing: a processor, a microcontroller, a hard-wired circuit, an ASIC, an FPGA, a logic device.

The solution provided herein further comprises a computer program product directly loadable into a memory of a digital computer, comprising software code portions for performing the steps of the method as described herein.

In addition, the problem stated above is solved by a comput- er-readable medium, e.g., storage of any kind, having comput^¬ er-executable instructions adapted to cause a computer system to perform the method as described herein.

Embodiments of the invention are shown and illustrated in the following figures:

Fig.l shows in an exemplary scenario a schematically cross- sectional view of a rotor blade including an exempla^¬ ry embodiment of the inventive structural condition monitoring of a rotor blade;

Fig.2 shows an advanced exemplary embodiment of the solu^¬ tion invented wherein a number of optical sensors are distributed inside the rotor blade;

Fig.3 shows the same exemplary scenario of Fig.2 wherein, different to Fig.2, a damage or crack has been devel^¬ oped through the rotor blade shell. Fig.l shows a schematically cross-sectional view of a rotor blade 100 of a wind turbine comprising a rotor blade shell 110 supported by a main shear web 115 following the shape of the shell 110 in longitudinal direction of the rotor blade 100. According to the exemplary embodiment of Fig.l the web 115 comprises a holding 120 with an optical sensor 130 being fixed to each end of the holding 120. It should be noted that different numbers and embodiments of the holding 120 are possible as well as the number and design of the sensors 130 fixed to the holding 120 may vary.

The optical sensors 130 are arranged for capturing at least one optical characteristic within an interior 111 of the ro^¬ tor blade 110. As an example, the optical sensors 130 may be adapted to capture light within the interior 111 of the rotor blade 100 and to measure the intensity of the captured light. Following the exemplary scenario of Fig.l, a damage in the form of a crack 140 has been developed through the rotor blade shell 110, e.g., by breaching one or more sandwich lay^¬ ers in the blade shell 110 and/or monolithic laminate. There^¬ by, light 150 emitted by a sun 105 is passing through the crack 140 into the interior 111 of the rotor blade 100.

The light 150 inside the rotor blade will be captured by at least one of the optical sensors 130 thereby measuring the intensity of the light and converting the measured light in- tensity ("measurement result") into information representing the measurement result.

The information may be established as a signal suitable to be provided by any kind of transmission medium.

The information may be an analog or digital information.

Signal may be an electrical or optical signal or a wireless signal .

An electrical signal representing the aforementioned infor^¬ mation may comprise at least one out of - an electrical voltage

- an electrical current

- an electrical resistant Examples of a transmission medium may be an electrical or op^¬ tical line or a wireless transmission medium.

Exemplary embodiments of the optical sensors 130 may be - photo resistors,

- photodiodes or

- any other kinds of electro-optical sensors

As already mentioned above, a number of optical sensors may be distributed inside the rotor blade 100, e.g. along the main shear web 115 as indicated in Fig.2.

Fig.2 shows an advanced exemplary embodiment of the solution invented. Thereby, a number of optical sensors 230 (e.g., be- ing the same type of optical sensors 130 as visualized in Fig.l) are distributed within an interior 211 of the rotor blade 211. The sensors 230 are interconnected by an electri^¬ cal wiring 220 being linked to a central processing unit 240 (also referred to as "interrogator") which might be located in a root section of the rotor blade 200 or in a rotor hub of the wind turbine. Alternatively, the interrogator 240 may be located centrally, e.g., in a nacelle being part of the wind turbine . Light intensity, i.e. an electrical signal 245 representing an amount or value of the light intensity measured by the re^¬ spective sensor 230 is provided by the respective sensor 230 to the processing unit 240 via the electrical wiring 220. According to the scenario of Fig.2, no crack is breaching the surface of the rotor blade 200. Thus, no light intensity or an extreme low amount or value of light intensity is measured by the respective sensors 230 forwarding the corresponding signal or information 245 to interrogator 240. Consequently, based on the provided information (i.e. due to the absence of light inside the rotor blade) , no damage or crack is detected by the interrogator 240. Based on that the operation of the wind turbine is controlled accordingly.

Fig.3 shows nearly the same exemplary scenario of Fig.2, thereby using the same reference numbers. As a difference to Fig.2 a damage or crack 340 has been de^¬ veloped through the shell of the rotor blade 200 as shown in Fig.3. As a consequence, light 350, e.g., emitted by the sun is passing through the crack 340 into the interior 211 of the rotor blade 200 which will be captured by at least one of the optical sensors 230. As a further consequence, a change of the captured light intensity, i.e. an increase of the meas^¬ ured light intensity is determined by the interrogator 240. Consequently, a damage of the rotor blade 200 is detected by the interrogator 240 based on the provided information 245. The damage may be reported, e.g., from the interrogator 240 to a service station of a wind farm or to a control station controlling remotely the respective wind turbine.

In case of a further development of the crack 340, more light will pass through the damage 340 into the interior 211 of the rotor blade 200. Consequently, a higher amount of light in^¬ tensity will be measured by at least one of the optical sen^¬ sors 230 providing the respective information 245 to the in^¬ terrogator 240.

Different types of optical sensors might be used for imple^¬ menting the proposed solution. Dependent on the type of opti^¬ cal sensors used inside the rotor blade the proposed struc^¬ tural condition monitoring system may need to be protected, e.g., against electrical current caused by possible lightning strikes . The proposed solution allows a monitoring of the structural condition of the rotor blade. The use of electro optical sen^¬ sors enables a cheap, robust and simple implementation of a damage detection system without the need of complex and ad- vanced algorithms to monitor the signals or information pro^¬ vided by the sensors.

Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and varia^¬ tions could be made thereto without departing from the scope of the invention.

For the sake of clarity, it is to be understood that the use of "a" or "an" throughout this application does not exclude plurality, and "comprising" does not exclude other steps or elements. The mention of a "unit" or a "module" does not pre elude the use of more than one unit or module.

Claims

1. Method for determining a structural condition of a rotor blade (100) of a wind turbine, comprising,

- monitoring at least one optical characteristic inside at least a part of the rotor blade (100),

- determining the structural condition of the rotor

blade (100) based on the monitored at least one opti^¬ cal characteristic.

2. The method according to claim 1, comprising

determining the structural condition based on a change of at least one of the monitored at least one optical characteristic inside the rotor blade (100).

3. The method according to any of the preceding claims, wherein

the at least one optical characteristic is monitored by using at least one optical sensor (130) located inside (111) the rotor blade (110) capturing and/or measuring the at least one optical characteristic and converting the captured and/or measured at least one optical char^¬ acteristic into at least one information (245) repre^¬ senting the captured and/or measured at least one opti^¬ cal characteristic wherein the at least one information (245) is provided via at least one transmission medium (220) .

4. The method according to any of the preceding claims, wherein

- the at least one optical characteristic is a light in^¬ tensity, and

The method according to claim 4, wherein

a damage of the rotor blade is detected in case of an increase of the provided amount or value of the light intensity .

The method according to any of the preceding claims, comprising

operating the wind turbine dependent on the determined structural condition of the rotor blade.

A wind turbine, comprising

- at least one rotor blade (100) comprising at least one optical sensor (130) located inside the rotor blade (100) ,

- the at least one sensor (130) is arranged to capture and/or measure at least one optical characteristic inside at least a part of the rotor blade (100),

- a processing unit that (240) is arranged for

- monitoring the at least one captured and/or meas^¬ ured optical characteristic inside the rotor blade,

- determining the structural condition of the rotor blade based on the monitored at least one optical characteristic .

A rotor blade suitable for being used in a wind turbine according to claim 7, comprising

- at least one optical sensor located inside the rotor blade, wherein the at least one sensor is arranged to capture and/or measure at least one optical character^¬ istic inside at least a part of the rotor blade,

A device comprising and/or being associated with a processor unit and/or hard-wired circuit and/or a logic de vice that is arranged such that the method according to any of the preceding claims 1 to 6 is executable there^¬ on .

10. A computer program product directly loadable into a

memory of a digital computer, comprising software code portions for performing the steps of the method accord^¬ ing to any of the claims 1 to 6.

11. A computer readable medium, having computer-executable instructions adapted to cause a computer system to per^¬ form the steps of the method according to any of the claims 1 to 6.