EP2764241A2 - Method and device for detecting accumulation of material on a blade of a wind turbine and for determining upwind condition - Google Patents

Method and device for detecting accumulation of material on a blade of a wind turbine and for determining upwind condition

Info

Publication number
EP2764241A2
EP2764241A2 EP12769424.8A EP12769424A EP2764241A2 EP 2764241 A2 EP2764241 A2 EP 2764241A2 EP 12769424 A EP12769424 A EP 12769424A EP 2764241 A2 EP2764241 A2 EP 2764241A2
Authority
EP
European Patent Office
Prior art keywords
blade
wind turbine
blades
accumulation
optical
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP12769424.8A
Other languages
German (de)
French (fr)
Inventor
Stellan WICKSTRÖM
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Windvector AB
Original Assignee
Windvector AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Windvector AB filed Critical Windvector AB
Publication of EP2764241A2 publication Critical patent/EP2764241A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D17/00—Monitoring or testing of wind motors, e.g. diagnostics
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/04—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness specially adapted for measuring length or width of objects while moving
    • G01B11/046—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness specially adapted for measuring length or width of objects while moving for measuring width
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D15/00—De-icing or preventing icing on exterior surfaces of aircraft
    • B64D15/20—Means for detecting icing or initiating de-icing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D17/00—Monitoring or testing of wind motors, e.g. diagnostics
    • F03D17/001—Inspection
    • F03D17/003—Inspection characterised by using optical devices, e.g. lidar or cameras
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D17/00—Monitoring or testing of wind motors, e.g. diagnostics
    • F03D17/027—Monitoring or testing of wind motors, e.g. diagnostics characterised by the component being monitored or tested
    • F03D17/028—Blades
    • F03D17/0285—Surfaces thereof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D80/00—Details, components or accessories not provided for in groups F03D1/00 - F03D17/00
    • F03D80/40—Ice detection; De-icing means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D80/00—Details, components or accessories not provided for in groups F03D1/00 - F03D17/00
    • F03D80/40—Ice detection; De-icing means
    • F03D80/405—Ice detection
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/80—Diagnostics
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/82—Forecasts
    • F05B2260/821—Parameter estimation or prediction
    • F05B2260/8211—Parameter estimation or prediction of the weather
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/80—Devices generating input signals, e.g. transducers, sensors, cameras or strain gauges
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/80—Devices generating input signals, e.g. transducers, sensors, cameras or strain gauges
    • F05B2270/804—Optical devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/80—Devices generating input signals, e.g. transducers, sensors, cameras or strain gauges
    • F05B2270/804—Optical devices
    • F05B2270/8042—Lidar systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction

Definitions

  • the present invention relates to the field of wind turbines, and more specifically to a device for instantaneously detecting accumulation of material on a blade of a wind turbine.
  • the invention also relates to a corresponding method for detecting accumulation of material on the blade.
  • the present invention further relates to a Light Detection and Ranging (LIDAR) system arranged to determine wind speed and wind direction from a remote location.
  • LIDAR Light Detection and Ranging
  • a number of parameters are important for optimizing energy efficiency. This can, for example, be the positioning of the wind turbines, size of the blades, height of the wind turbine nacelle above ground, knowledge of wind condition, etc. Furthermore, it is also important to control the condition of the blades of the wind turbine such that the wind turbine is able to work at an approximately optimal efficiency. It is hence important to continuously control the blades such that they are intact and free from accumulated material, such as for instance ice.
  • the wind turbine When the blades are accumulated with material, such as ice, the wind turbine can be subjected to serious unintended loads which can cause overloads and stresses to the blades as well as to the entire drive train of the wind turbine. Also, if one blade is accumulated with more material than another blade, the wind turbine may be subjected to an unbalanced situation, which may reduce the energy efficiency as well as damage interior parts of the wind turbine.
  • WO201 1/009 459 A2 discloses a device for detecting surface conditions such as ice formation on the blades of a wind turbine.
  • the blades of the wind turbine are being subjected to light from a radiation emitter; reflected light is thereafter evaluated based on the amount of diffuse reflected and mirror reflected radiation reflected from the blade in order to determine if ice is present on the blade.
  • the device/system described in WO201 1/009 459 A2 may thus detect the presence of ice on the blades, but appears to lack the ability to determine the quantity of accumulated material on the blades. There is hence a need to be able to determine the amount of accumulated material on the blades during operation.
  • an object of the present invention is thus to provide an improved method and device for detecting accumulated material on the blade of a wind turbine.
  • To detect the amount of accumulated material on the blade of the wind turbine is advantageous since it can reduce the need of maintenance and thereby enable for e.g. improved energy efficiency.
  • detection of accumulated material on the blade is beneficial in a durability aspect, since the wind turbine may be prevented from being exposed to overloads and fatigue.
  • a method for detecting accumulation of material on a blade of a wind turbine comprising the steps of: transmitting a light beam towards the blades of the wind turbine; receiving reflected light from the blades;
  • determining a width of the blade based on a detected intensity variation over time of the reflected light determining a width of the blade based on a detected intensity variation over time of the reflected light; and providing a signal indicating accumulation of material on the blade if the width of the blade determined based on the detected intensity variation over time is larger than a known width of the blade without accumulation of material.
  • the present invention is based on the realization that the blades of the wind turbine during revolution will cover the light beam, which is transmitted from an optical transmitter preferably arranged on the wind turbine nacelle, every time they pass the light beam, and hence a reflected light beam will be provided to an optical receiver. Based on a detected intensity variation over time of the reflected light beam, a current width of the blade may be determined.
  • Advantages of the present invention include, for example, that small amount of accumulated material on the blade of the wind turbine can be detected with high accuracy and reliability. Also, by providing a method that detects accumulation of material on the blade of the wind turbine and provides a signal if accumulated material is detected may reduce
  • the presence of accumulated material may be continuously detected.
  • the detection of accumulated material on the blades may be provided approximately instantaneously to an operator of the wind turbine.
  • the light beam may be a coherent laser beam.
  • the accumulated material may comprise snow or ice.
  • the transmitting of a light beam and receiving of reflected light may be executed by a light detection and ranging (LIDAR) system.
  • LIDAR light detection and ranging
  • a LIDAR system is well known and can be provided in a suitable size to fit the wind turbine nacelle.
  • the LIDAR system since the LIDAR system has the benefits of being able to transmit and receive a light beam, the number of parts for detecting accumulated material on the blade of the wind turbine may be reduced.
  • the LIDAR system may be connected to the control system of the wind turbine such that it can measure the speed of revolution of the blades. By measuring the speed of revolution of the blades and having knowledge of the width of the blades without accumulation of material, it may be possible to further improve the accuracy of detecting accumulated material on the blades. This may be executed by measuring an increase of the time period for receiving reflected light, i.e. the time period when the blade passes the transmitted light beam, and at the same time detect the speed of revolution of the blades.
  • a device arranged to detect accumulation of material on a blade of a wind turbine, wherein the device comprises an optical transmitter arranged to transmit a light beam towards the blades of the wind turbine, an optical receiver arranged to receive a reflected light beam from the blades of the wind turbine, processing circuitry arranged to determine a width of the blade based on a detected intensity variation over time of the reflected light beam, and to provide a signal indicating accumulated material on the blade if the width of the blade determined based on the detected intensity over time is larger than a known width of the blade without accumulation of material.
  • the light beam is a coherent laser beam.
  • a wind turbine having the above described device for detecting accumulation of material on the blades of the wind turbine, wherein the device is preferably arranged on the wind turbine nacelle.
  • the device may also be arranged to detect wind speed and direction at a remote location from the wind turbine.
  • a light detecting and ranging (LIDAR) system for determining wind speed and direction at a remote location, comprising a coherent laser for providing a transmission beam and a reference beam, an optical system for focusing the transmission beam at the remote location, where the transmission beam is reflected and frequency shifted depending on the wind speed so that a frequency shifted reflected beam is returned towards the optical system, a mixer device for mixing the frequency shifted reflected beam and the reference beam to provide a combined signal indicative of a frequency difference between the reflected beam and the reference beam, an optical switch arranged between the coherent laser and the optical system, the optical switch being controllable to change a position of incidence of the transmission beam on the optical system resulting in a change in focusing position at the remote location, and processing circuitry connected to the mixer and the optical switch, and further configured to control the optical switch to successively change the position of incidence of the transmission beam on the optical system and to determine the wind speed and direction at the remote location based on the combined signal for the different focusing
  • LIDAR light detecting and ranging
  • the wind turbine may then change the direction of the blades in order to continuously direct them in an essentially upwind direction.
  • sudden changes in wind speed which can be critical for the blades and their durability, can be detected at an early stage, which may improve the durability of the wind turbine.
  • the wind turbine can, for example, reduce the speed of the blades to be more prepared to the sudden change in wind speed.
  • the wind turbine may be controlled to determine at which time it may be suitable to change direction of the blades, in order to optimize the wind turbine in respect to wind utilization.
  • the transmission beam When the transmission beam hits the wind particles at the remote location, it is reflected back to the LIDAR system.
  • the reflected beam is frequency shifted due to the Doppler effect, and the wind speed can thereby be determined by calculating the change in frequency between the frequency shifted reflected beam and the reference beam.
  • the LIDAR system may further be arranged to detect accumulation of material on the blades of the wind turbine.
  • the LIDAR system may further be arranged to provide a plurality of positions of incidence of the transmission beam, such that each transmission beam is configured to be focused on a respective measuring point at the remote location.
  • the optical system may comprise an optical lens.
  • the plurality of positions of incidence of the transmission beam may be provided through the optical lens, wherein the optical lens may further be arranged to direct the transmission beam on a respective focusing position at the remote location.
  • the optical lens may further be arranged to direct the transmission beam on a respective focusing position at the remote location.
  • the plurality of position of incidence may provide the transmission beams to be oriented in a generally vertical or horizontal plane.
  • the wind speed and direction can be determined in the generally vertical or horizontal direction, or in a 2D-configuration such as a matrix.
  • the optical switch may further be arranged to change configuration of the transmission beams from the generally vertical plane orientation to the generally horizontal plane
  • wind speed and direction can always be detected and measured, independent of its direction.
  • Fig. 1 is a perspective view illustrating a wind turbine provided with a device for detecting accumulation of material according to an embodiment of the present invention
  • Fig. 2 is a perspective view illustrating the embodiment of Fig. 1 on top of the nacelle of the wind turbine;
  • Fig. 3 is a diagram schematically illustrating the time periods when the blades of the wind turbine are covered with the coherent laser beam
  • Fig. 4 is a flow chart schematically illustrating an embodiment of a method for detecting accumulation of material on the blade of the wind turbine.
  • Fig. 5 is a flow chart schematically illustrating an embodiment for detecting wind speed and direction at a remote location from the wind turbine.
  • the present invention is described with reference to a device and corresponding method for detecting accumulation of material on a blade of a wind turbine, by using a coherent laser beam which is positioned behind the blades in an upwind direction.
  • ice detection device The device for detecting accumulation of material will therefore be referred to as an ice detection device.
  • the accumulated material on the blades is not restricted to ice, since this is just an example.
  • the accumulated material may also be, for example, snow or dust particles, etc. Therefore, the wording ice detection device referred to in the following should not be interpreted as a device only arranged to detect ice, but as a device arranged to detect any accumulated material that may adhere to the blades during revolution.
  • Fig. 1 is a perspective view illustrating a wind turbine 100.
  • the wind turbine 100 comprises a nacelle 104 and three turbine blades 108a - c, hereinafter just referred to as blades.
  • the nacelle 104 is mounted on top of a supporting structure, here in the form of a frame 102, of the wind turbine 100.
  • the ice detection device 106 comprises a light detection and ranging (LIDAR) system having an optical transmitter, an optical receiver and processing circuitry.
  • LIDAR light detection and ranging
  • the optical transmitter is arranged to continuously transmit a coherent laser beam in a direction from the ice detection device 106 towards the blades 108a -c of the wind turbine 100.
  • the processing circuitry is arranged to
  • the processing circuitry may also be arranged to determine the speed of revolution of the blades 108a - c during operation, in order to improve the accuracy of detecting accumulated material.
  • FIG. 2 illustrates, from behind, the ice detection device 106 arranged on top of the nacelle 104, as well as one of the rotating blades 108a of the wind turbine 104.
  • the blade 108a is, in the illustrated embodiment, partly covered with accumulation of material 201 , i.e. the width of the blade 108a is larger than the width of the blade 108a without
  • FIG. 3 illustrates a diagram of the revolution of the blades 108a - c.
  • One revolution of the wind turbine 100 is illustrated as T, where each of the blades 108a - c are covered by the coherent laser beam during a time interval At.
  • Fig. 4 is a flow chart schematically illustrating an embodiment of a method for detecting accumulation of material on the blades 108a - c of the wind turbine 100.
  • the ice detection device 106 continuously transmits the coherent laser beam from the optical transmitter of the LIDAR system, during revolution of the blades 108a - c.
  • the blades 108a - c rotate, they will cover the transmitted coherent laser beam each time they pass the upper part of the nacelle 104.
  • the three blades 108a - c in the described embodiment will cover the transmitted coherent laser beam once, as illustrated in Fig. 3.
  • the blade 108a is covered by the coherent laser beam and the laser beam is reflected back towards the ice detection device 106 and received by the optical receiver of the LIDAR system.
  • the processing circuitry of the LIDAR system can, by determining the detected intensity over time, i.e. of the time interval At of the reflected light beam, determine the width of the blade 108a.
  • the determined width may thereafter, or continuously, be compared to a known width of the blade 108a without accumulation of material 201 , in order to determine if the blade 108 is provided with
  • the processing circuitry may also be arranged to detect the speed of revolution of the blades 108a - c, and thereby determine a current width of the blade 108a. Furthermore, if the ice detection device 106 detects that the width of the blade 108a is larger than a known width of the blade 108a without accumulation of material, the ice detection device 106 can provide a signal to e.g. an operator of the wind turbine 100. The wind turbine 100 can then be shut off such that the accumulated material 201 can removed before the wind turbine 100 ones again is operated.
  • the signal system of the LIDAR system may however also be configured to provide a signal if a sufficient
  • predetermined amount of accumulated material 201 is detected on the blades 108a - c of the wind turbine 100.
  • the operator of the wind turbine 100 can decide to shut off the wind turbine 100 on a less frequent basis, i.e. when he or she finds the amount of accumulated material 201 on the blades 108a - c to be critical for the functioning of the wind turbine 100.
  • Fig. 5 illustrates a flow chart for detecting wind speed and direction at a remote location R from the wind turbine 100.
  • Fig. 1 illustrates a flow chart for detecting wind speed and direction at a remote location R from the wind turbine 100.
  • Fig. 1 illustrates a flow chart for detecting wind speed and direction at a remote location R from the wind turbine 100.
  • the system for detecting wind speed and direction is, in the illustrated embodiment, a light detecting and ranging (LIDAR) system 500 preferably arranged on top of the nacelle 104 as is illustrated in Fig. 1 .
  • LIDAR light detecting and ranging
  • the LIDAR system 500 comprises a coherent laser beam 502, beam splitters 504a, 504b, an optical system 514, a mixer device 506, an optical switch 512, a detector 508, such as a PIN diode, and processing circuitry 510.
  • the coherent laser beam 502 is arranged to provide a transmission beam and a reference beam with equal frequency.
  • the transmission beam is provided through the optical switch 512, via each of the beam splitters 504a - b, and further into the optical system 514, here illustrated having an optical lens. In the illustrated embodiment, when the transmission beam is provided to the optical switch 512, it can be arranged at three different positions of incidence.
  • the transmission beam is provided through the optical system 514, i.e.
  • the optical switch 512 may arrange the transmission beam to more than three different positions of incidence and choice of three is hence just for illustrative purposes.
  • the laser beam is reflected back to the optical system 514 of the LIDAR system 500. Due to the Doppler effect, the reflected light beams are frequency shifted in relation to the transmission beam.
  • the frequency shifted reflected beam is provided to the mixer device 506 of the LIDAR system 500, where it is mixed with the reference beam to provide a combined signal indicative of a frequency difference between the reflected beam and the reference beam.
  • the combined signal is thereafter provided from the mixer device 506 to the detector 508 such that a signal indicative of the wind speed and direction at the remote location R can be provided to the processing circuitry 510.
  • the processing circuitry 510 is further arranged to control the optical switch 512, such that the position of incidence can be continuously changed.
  • the focusing position can be changed such that LIDAR system 500 focuses on the desired position.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Optical Radar Systems And Details Thereof (AREA)
  • Wind Motors (AREA)
  • Testing Of Devices, Machine Parts, Or Other Structures Thereof (AREA)

Abstract

The present invention relates to a method for detecting accumulation of material (201) on a blade (108a) of a wind turbine (104), said method comprising the steps of: transmitting (S1) a light beam towards the blades (108a - 108c) of said wind turbine (104); receiving (S2) reflected light from the blades (108a - 108c) of said wind turbine(104); determining (S3) an instant width of said blade (108a) based on a detected intensity variation over time of the reflected light; and providing (S4) a signal indicating accumulation of material (201) on said blade (108a) if said determined width of the blade (108a) based on the detected intensity over time is larger than a known width of the blade (108a) without accumulation of material (201).

Description

METHOD AND DEVICE FOR DETECTING ACCUMULATION OF MATERIAL
ON A BLADE OF A WIND TURBINE AND FOR DETERMINING UPWIND
CONDITION
Technical field
The present invention relates to the field of wind turbines, and more specifically to a device for instantaneously detecting accumulation of material on a blade of a wind turbine. The invention also relates to a corresponding method for detecting accumulation of material on the blade.
Moreover, the present invention further relates to a Light Detection and Ranging (LIDAR) system arranged to determine wind speed and wind direction from a remote location. Background
In the field of wind turbines, a number of parameters are important for optimizing energy efficiency. This can, for example, be the positioning of the wind turbines, size of the blades, height of the wind turbine nacelle above ground, knowledge of wind condition, etc. Furthermore, it is also important to control the condition of the blades of the wind turbine such that the wind turbine is able to work at an approximately optimal efficiency. It is hence important to continuously control the blades such that they are intact and free from accumulated material, such as for instance ice.
When the blades are accumulated with material, such as ice, the wind turbine can be subjected to serious unintended loads which can cause overloads and stresses to the blades as well as to the entire drive train of the wind turbine. Also, if one blade is accumulated with more material than another blade, the wind turbine may be subjected to an unbalanced situation, which may reduce the energy efficiency as well as damage interior parts of the wind turbine.
The field of wind power is an increasingly growing market and development has been made in an attempt to efficiently and reliably control the blades of the wind turbine.
WO201 1/009 459 A2 discloses a device for detecting surface conditions such as ice formation on the blades of a wind turbine. The blades of the wind turbine are being subjected to light from a radiation emitter; reflected light is thereafter evaluated based on the amount of diffuse reflected and mirror reflected radiation reflected from the blade in order to determine if ice is present on the blade. The device/system described in WO201 1/009 459 A2 may thus detect the presence of ice on the blades, but appears to lack the ability to determine the quantity of accumulated material on the blades. There is hence a need to be able to determine the amount of accumulated material on the blades during operation.
Furthermore, to provide the wind turbine with approximately optimum conditions, in order to produce as much energy as possible, it would also be desirable to be able to predict the speed and direction of the wind
approaching the wind turbine.
Summary of the invention
In view of the above mentioned and other drawbacks of the prior art, an object of the present invention is thus to provide an improved method and device for detecting accumulated material on the blade of a wind turbine. To detect the amount of accumulated material on the blade of the wind turbine is advantageous since it can reduce the need of maintenance and thereby enable for e.g. improved energy efficiency. Also, detection of accumulated material on the blade is beneficial in a durability aspect, since the wind turbine may be prevented from being exposed to overloads and fatigue.
According to a first aspect of the present invention there is provided a method for detecting accumulation of material on a blade of a wind turbine, the method comprising the steps of: transmitting a light beam towards the blades of the wind turbine; receiving reflected light from the blades;
determining a width of the blade based on a detected intensity variation over time of the reflected light; and providing a signal indicating accumulation of material on the blade if the width of the blade determined based on the detected intensity variation over time is larger than a known width of the blade without accumulation of material.
The present invention is based on the realization that the blades of the wind turbine during revolution will cover the light beam, which is transmitted from an optical transmitter preferably arranged on the wind turbine nacelle, every time they pass the light beam, and hence a reflected light beam will be provided to an optical receiver. Based on a detected intensity variation over time of the reflected light beam, a current width of the blade may be determined. Advantages of the present invention include, for example, that small amount of accumulated material on the blade of the wind turbine can be detected with high accuracy and reliability. Also, by providing a method that detects accumulation of material on the blade of the wind turbine and provides a signal if accumulated material is detected may reduce
maintenance time, since the need of an operator to check the current status of the blades is less necessary. Moreover, to measure the amount of accumulated material on the blade may also be beneficial in terms of production efficiency, since a small amount of accumulated material on the blades may be accepted in respect of e.g. durability of the wind turbine, prior to performing maintenance. Hereby, an operator of the wind turbine may decide to turn off the wind turbine in order to remove the accumulated material when the accumulated material has exceeded an acceptable level. The wind turbine may thus be able to produce energy to an essentially optimal time level. It should thus be noted that the above wording "width without accumulation of material" does not necessarily have to exclude any material on the blade since a small amount of accumulated material on the blade may be accepted.
According to an embodiment of the present invention, the presence of accumulated material may be continuously detected. Hereby, the detection of accumulated material on the blades may be provided approximately instantaneously to an operator of the wind turbine.
Furthermore, the light beam may be a coherent laser beam. According to an example, the accumulated material may comprise snow or ice.
According to a further embodiment of the present invention, the transmitting of a light beam and receiving of reflected light may be executed by a light detection and ranging (LIDAR) system. A LIDAR system is well known and can be provided in a suitable size to fit the wind turbine nacelle. Moreover, since the LIDAR system has the benefits of being able to transmit and receive a light beam, the number of parts for detecting accumulated material on the blade of the wind turbine may be reduced. Also, the LIDAR system may be connected to the control system of the wind turbine such that it can measure the speed of revolution of the blades. By measuring the speed of revolution of the blades and having knowledge of the width of the blades without accumulation of material, it may be possible to further improve the accuracy of detecting accumulated material on the blades. This may be executed by measuring an increase of the time period for receiving reflected light, i.e. the time period when the blade passes the transmitted light beam, and at the same time detect the speed of revolution of the blades.
According to a second aspect of the present invention there is provided a device arranged to detect accumulation of material on a blade of a wind turbine, wherein the device comprises an optical transmitter arranged to transmit a light beam towards the blades of the wind turbine, an optical receiver arranged to receive a reflected light beam from the blades of the wind turbine, processing circuitry arranged to determine a width of the blade based on a detected intensity variation over time of the reflected light beam, and to provide a signal indicating accumulated material on the blade if the width of the blade determined based on the detected intensity over time is larger than a known width of the blade without accumulation of material.
According to an embodiment, the light beam is a coherent laser beam.
According to an embodiment, there is provided a wind turbine having the above described device for detecting accumulation of material on the blades of the wind turbine, wherein the device is preferably arranged on the wind turbine nacelle.
According to a still further aspect, the device may also be arranged to detect wind speed and direction at a remote location from the wind turbine.
Effects and features of this second aspect are largely analogous to those described in relation to the above mentioned first aspect of the present invention.
According to a third aspect of the present invention there is provided a light detecting and ranging (LIDAR) system for determining wind speed and direction at a remote location, comprising a coherent laser for providing a transmission beam and a reference beam, an optical system for focusing the transmission beam at the remote location, where the transmission beam is reflected and frequency shifted depending on the wind speed so that a frequency shifted reflected beam is returned towards the optical system, a mixer device for mixing the frequency shifted reflected beam and the reference beam to provide a combined signal indicative of a frequency difference between the reflected beam and the reference beam, an optical switch arranged between the coherent laser and the optical system, the optical switch being controllable to change a position of incidence of the transmission beam on the optical system resulting in a change in focusing position at the remote location, and processing circuitry connected to the mixer and the optical switch, and further configured to control the optical switch to successively change the position of incidence of the transmission beam on the optical system and to determine the wind speed and direction at the remote location based on the combined signal for the different focusing positions at the remote location.
It has been realized that particles in the wind travel at approximately the same speed and direction as the wind itself. Hereby, it may be possible to determine the wind speed and direction of these particles, i.e. the wind, at a remote location from the wind turbine by comparing the frequency of the reflected beam with the frequency of the reference beam. When changing position of incidence of the transmission beam at the remote location, a vector profile of the wind, i.e. a wind direction and wind speed, may be provided. An advantage of this third aspect is thus that the wind speed and wind direction may be determined in advance, before the wind has
approached the wind turbine. This is especially beneficial since the wind turbine may then change the direction of the blades in order to continuously direct them in an essentially upwind direction. Also, sudden changes in wind speed, which can be critical for the blades and their durability, can be detected at an early stage, which may improve the durability of the wind turbine. The wind turbine can, for example, reduce the speed of the blades to be more prepared to the sudden change in wind speed. Moreover, since the speed of the wind is detected, the wind turbine may be controlled to determine at which time it may be suitable to change direction of the blades, in order to optimize the wind turbine in respect to wind utilization.
The wording "remote location" should be interpreted as any location or position within some kilometers from the wind turbine. The skilled person will however realize that the exact location is dependent on several factors, for instance, current wind speed, the wind turbine ability to change direction of the blades, etc.
When the transmission beam hits the wind particles at the remote location, it is reflected back to the LIDAR system. The reflected beam is frequency shifted due to the Doppler effect, and the wind speed can thereby be determined by calculating the change in frequency between the frequency shifted reflected beam and the reference beam.
According to an embodiment, the LIDAR system may further be arranged to detect accumulation of material on the blades of the wind turbine.
According to an embodiment, the LIDAR system may further be arranged to provide a plurality of positions of incidence of the transmission beam, such that each transmission beam is configured to be focused on a respective measuring point at the remote location.
According to an embodiment, the optical system may comprise an optical lens.
Furthermore, the plurality of positions of incidence of the transmission beam may be provided through the optical lens, wherein the optical lens may further be arranged to direct the transmission beam on a respective focusing position at the remote location. By providing a lens to direct the transmission beam to a respective focusing position may be advantageous since it reduces the number of parts of the LIDAR system compared to providing an individual lens for each focusing position of the transmission beam. Hereby, a less bulky and cost efficient system may be provided.
Still further, the plurality of position of incidence may provide the transmission beams to be oriented in a generally vertical or horizontal plane. Hereby, the wind speed and direction can be determined in the generally vertical or horizontal direction, or in a 2D-configuration such as a matrix.
According to an embodiment, the optical switch may further be arranged to change configuration of the transmission beams from the generally vertical plane orientation to the generally horizontal plane
orientation, or vice versa. This may be advantageous when it is desired to change from detecting wind speed and direction in the generally vertical plane to detect wind speed and direction in the generally horizontal plane, or vice versa. Hereby, the wind speed and direction can always be detected and measured, independent of its direction.
Brief description of the drawings
These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing example embodiments of the invention, wherein:
Fig. 1 is a perspective view illustrating a wind turbine provided with a device for detecting accumulation of material according to an embodiment of the present invention;
Fig. 2 is a perspective view illustrating the embodiment of Fig. 1 on top of the nacelle of the wind turbine;
Fig. 3 is a diagram schematically illustrating the time periods when the blades of the wind turbine are covered with the coherent laser beam; Fig. 4 is a flow chart schematically illustrating an embodiment of a method for detecting accumulation of material on the blade of the wind turbine; and
Fig. 5 is a flow chart schematically illustrating an embodiment for detecting wind speed and direction at a remote location from the wind turbine.
Detailed description of example embodiments of the present invention
In the following description, the present invention is described with reference to a device and corresponding method for detecting accumulation of material on a blade of a wind turbine, by using a coherent laser beam which is positioned behind the blades in an upwind direction. The
accumulated material will in the following be described as ice, since this is one, of many, materials that may adhere to the blades during operation. The device for detecting accumulation of material will therefore be referred to as an ice detection device.
It should be noted that this by no means limits the scope of the present invention, which is equally applicable with other light transmission means than a coherent light beam. Also, the accumulated material on the blades is not restricted to ice, since this is just an example. The accumulated material may also be, for example, snow or dust particles, etc. Therefore, the wording ice detection device referred to in the following should not be interpreted as a device only arranged to detect ice, but as a device arranged to detect any accumulated material that may adhere to the blades during revolution.
Fig. 1 is a perspective view illustrating a wind turbine 100. The wind turbine 100 comprises a nacelle 104 and three turbine blades 108a - c, hereinafter just referred to as blades. The nacelle 104 is mounted on top of a supporting structure, here in the form of a frame 102, of the wind turbine 100. On top of the nacelle 104, behind the blades 108a - c, is mounted an ice detection device 106 for detecting accumulation of material, e.g. ice, on the blades 108a - c of the wind turbine 100 during operation. In the illustrated embodiment, the ice detection device 106 comprises a light detection and ranging (LIDAR) system having an optical transmitter, an optical receiver and processing circuitry. The optical transmitter is arranged to continuously transmit a coherent laser beam in a direction from the ice detection device 106 towards the blades 108a -c of the wind turbine 100. When the blades 108a - c, during revolution, cover the coherent laser beam, the transmitted light is reflected towards the ice detection device 106 and received by the optical receiver. Furthermore, the processing circuitry is arranged to
determine if accumulated material is present on the blades 108a - c based on a detected intensity variation over time of the reflected light. Moreover, the processing circuitry may also be arranged to determine the speed of revolution of the blades 108a - c during operation, in order to improve the accuracy of detecting accumulated material.
Reference is now made to Figs. 2 to 4 in order to describe the invention in yet more detail. Fig. 2 illustrates, from behind, the ice detection device 106 arranged on top of the nacelle 104, as well as one of the rotating blades 108a of the wind turbine 104. The blade 108a is, in the illustrated embodiment, partly covered with accumulation of material 201 , i.e. the width of the blade 108a is larger than the width of the blade 108a without
accumulated material 201 . Fig. 3 illustrates a diagram of the revolution of the blades 108a - c. One revolution of the wind turbine 100 is illustrated as T, where each of the blades 108a - c are covered by the coherent laser beam during a time interval At. Furthermore, Fig. 4 is a flow chart schematically illustrating an embodiment of a method for detecting accumulation of material on the blades 108a - c of the wind turbine 100.
According to Fig. 2, the ice detection device 106 continuously transmits the coherent laser beam from the optical transmitter of the LIDAR system, during revolution of the blades 108a - c. As the blades 108a - c rotate, they will cover the transmitted coherent laser beam each time they pass the upper part of the nacelle 104. During one revolution T of the wind turbine 100, the three blades 108a - c in the described embodiment will cover the transmitted coherent laser beam once, as illustrated in Fig. 3. During the time interval At, the blade 108a is covered by the coherent laser beam and the laser beam is reflected back towards the ice detection device 106 and received by the optical receiver of the LIDAR system. Thereafter, the processing circuitry of the LIDAR system can, by determining the detected intensity over time, i.e. of the time interval At of the reflected light beam, determine the width of the blade 108a. The determined width may thereafter, or continuously, be compared to a known width of the blade 108a without accumulation of material 201 , in order to determine if the blade 108 is provided with
accumulation of material 201 , such as e.g. ice. In one embodiment, the processing circuitry may also be arranged to detect the speed of revolution of the blades 108a - c, and thereby determine a current width of the blade 108a. Furthermore, if the ice detection device 106 detects that the width of the blade 108a is larger than a known width of the blade 108a without accumulation of material, the ice detection device 106 can provide a signal to e.g. an operator of the wind turbine 100. The wind turbine 100 can then be shut off such that the accumulated material 201 can removed before the wind turbine 100 ones again is operated. The signal system of the LIDAR system may however also be configured to provide a signal if a sufficient
predetermined amount of accumulated material 201 is detected on the blades 108a - c of the wind turbine 100. Hereby, the operator of the wind turbine 100 can decide to shut off the wind turbine 100 on a less frequent basis, i.e. when he or she finds the amount of accumulated material 201 on the blades 108a - c to be critical for the functioning of the wind turbine 100.
Although the above ice detection device 106 as described in relation to Figs. 1 to 4 is described with reference to a LIDAR system, the skilled person realizes that other suitable systems which can transmit and receive a light beam is equally applicable to be incorporate in the above ice detection device 106.
Reference is now made to Fig. 5, which illustrates a flow chart for detecting wind speed and direction at a remote location R from the wind turbine 100. In the exemplary embodiment, reference is also made to the wind turbine 100 illustrated in Fig. 1 .
The system for detecting wind speed and direction is, in the illustrated embodiment, a light detecting and ranging (LIDAR) system 500 preferably arranged on top of the nacelle 104 as is illustrated in Fig. 1 .
The LIDAR system 500 comprises a coherent laser beam 502, beam splitters 504a, 504b, an optical system 514, a mixer device 506, an optical switch 512, a detector 508, such as a PIN diode, and processing circuitry 510. The coherent laser beam 502 is arranged to provide a transmission beam and a reference beam with equal frequency. The transmission beam is provided through the optical switch 512, via each of the beam splitters 504a - b, and further into the optical system 514, here illustrated having an optical lens. In the illustrated embodiment, when the transmission beam is provided to the optical switch 512, it can be arranged at three different positions of incidence. The transmission beam is provided through the optical system 514, i.e. the lens, in order to be focused on the wind particles on a respective focusing position at the remote location R, depending on the specific instant position of incidence. It should thus be noted that the optical switch 512 may arrange the transmission beam to more than three different positions of incidence and choice of three is hence just for illustrative purposes.
When each of the transmission beams hits the particles at their respective remote location R, the laser beam is reflected back to the optical system 514 of the LIDAR system 500. Due to the Doppler effect, the reflected light beams are frequency shifted in relation to the transmission beam. The frequency shifted reflected beam is provided to the mixer device 506 of the LIDAR system 500, where it is mixed with the reference beam to provide a combined signal indicative of a frequency difference between the reflected beam and the reference beam. The combined signal is thereafter provided from the mixer device 506 to the detector 508 such that a signal indicative of the wind speed and direction at the remote location R can be provided to the processing circuitry 510.
Moreover, as the wind speed and direction change, the processing circuitry 510 is further arranged to control the optical switch 512, such that the position of incidence can be continuously changed. Hereby, depending on the present wind direction, i.e. the position and direction of the remote location R, the focusing position can be changed such that LIDAR system 500 focuses on the desired position.
In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Claims

1 . A method for detecting accumulation of material (201 ) on a blade (108a) of a wind turbine (100), said method comprising the steps of:
- transmitting (S1 ) a light beam towards the blades (108a - 108c) of said wind turbine (100);
- receiving (S2) reflected light from said blade (108a);
- determining (S3) a width of said blade (108a) based on a detected intensity variation over time of the reflected light; and
- providing (S4) a signal indicating accumulation of material (201 ) on said blade (108a) if said width of the blade (108a) determined based on the detected intensity over time is larger than a known width of the blade (108) without accumulation of material (201 ).
2. The method according to claim 1 , wherein said light beam is a coherent laser beam.
3. The method according to claim 1 or 2, wherein said material comprises snow or ice.
4. The method according to any one of the preceding claims, further arranged to detect wind speed and direction at a remote distance from said wind turbine (100).
5. The method according to any one of the preceding claims, wherein said transmitting of a light beam and receiving of reflected light is executed by a light detection and ranging (LIDAR) system.
6. A device (106) arranged to detect accumulation of material (102) on a blade (108a) of a wind turbine (100), wherein said device (106) comprises:
- an optical transmitter arranged to transmit a light beam towards the blades (108a - 108c) of said wind turbine (100),
- an optical receiver arranged to receive a reflected light beam from the blades (108a - 108c) of said wind turbine (100),
- processing circuitry arranged to determine a width of said blade (108a) based on a detected intensity variation over time of said reflected light beam, and to provide a signal indicating accumulated material (201 ) on said blade (108a) if the determined width of said blade (108a) based on the detected intensity over time is larger than a known width of the blade (108a) without accumulation of material (201 ).
7. The device (106) according to claim 5, wherein said light beam is a coherent laser beam.
8. A wind turbine (100) comprising the device (106) as claimed in claim 6 or 7, arranged on a nacelle (104) of the wind turbine (100).
9. A LIDAR system (500) for determining wind speed and direction at a remote location (R), comprising:
- a coherent laser (502) for providing a transmission beam and a reference beam;
- an optical system (514) for focusing the transmission beam at the remote location (R), where the transmission beam is reflected and frequency shifted depending on the wind speed so that a frequency shifted reflected beam is returned towards the optical system (514);
- a mixer device (506) for mixing the frequency shifted reflected beam and the reference beam to provide a combined signal indicative of a frequency difference between the reflected beam and the reference beam;
- an optical switch (512) arranged between the coherent laser (502) and the optical system (514), the optical switch (512) being controllable to change a position of incidence of the transmission beam on the optical system (514) resulting in a change in focusing position at the remote location (R); and
- processing circuitry (510) connected to the mixer (506) and the optical switch (512), and further configured to control the optical switch (512) to successively change the position of incidence of the transmission beam on the optical system (514) and to determine the wind speed and direction at the remote location (R) based on the combined signal for the different focusing positions at the remote location (R).
10. The LIDAR system (500) according to claim 9, further arranged to detect accumulation of material (201 ) on the blades (108a - 108c) of a wind turbine (100).
1 1 . The LIDAR system (500) according to claim 8 or 9, and further arranged to provide a plurality of positions of incidence of the transmission beam, such that each transmission beam is configured to be focused on a respective measuring point at the remote location (R).
12. The LIDAR system (500) according to any one of claims 8 to 1 1 , wherein the optical system (514) comprises an optical lens.
13. The LIDAR system (500) according to claim 1 1 , wherein said transmission beam is provided through the optical lens, said optical lens is further arranged to direct said transmission beam on a respective focusing position at the remote location (R).
14. The LIDAR system (500) according to claim 12 or 13, wherein the plurality of positions of incidence provide said transmission beams to be oriented in a generally vertical or horizontal plane.
15. The LIDAR system (500) according to claim 14, wherein the optical switch (512) is further arranged to change configuration of the transmission beams from the generally vertical plane orientation to the generally horizontal plane orientation, or vice versa.
EP12769424.8A 2011-10-05 2012-10-04 Method and device for detecting accumulation of material on a blade of a wind turbine and for determining upwind condition Withdrawn EP2764241A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1150921A SE1150921A1 (en) 2011-10-05 2011-10-05 Method and apparatus for detecting the accumulation of material on the blade of a wind turbine and for determining the incoming wind conditions
PCT/EP2012/069640 WO2013050485A2 (en) 2011-10-05 2012-10-04 Method and device for detecting accumulation of material on a blade of a wind turbine and for determining upwind condition

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US9606234B2 (en) 2013-10-18 2017-03-28 Tramontane Technologies, Inc. Amplified optical circuit
JP6429723B2 (en) * 2015-05-11 2018-11-28 三菱電機株式会社 Laser radar apparatus and observation method
CN106569290A (en) * 2016-11-11 2017-04-19 天津中新安德科技有限公司 Meteorological data acquisition system
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