EP4792024A1 - Wind turbine with operation mode change to prevent bird collision - Google Patents

Abstract

A method for deterring airborne animals to prevent collision between the airborne animal and a wind turbine. The method comprises providing data (PD) from at least one data source regarding at least one parameter relevant for an airspace of 5 the wind turbine. Next, analyzing said data (AD) according to an algorithm to determine presence of any one or more airborne animals in the airspace. In case it is determined that airborne animals are present, then changing (C_O) one or more parameters of operation of a rotor of the wind turbine, so as to cause the wind turbine to invoke an air pressure and/or wind velocity variation at a distance 10 of the wind turbine, e.g. upstream of downstream of the wind turbine, to deter the airborne animal from approaching the wind turbine. This may be a static increase or decrease in air pressure and/or wind velocity, or an increase in audible noise generated by the wind turbine, e.g. caused by pitching rotor blade(s) to generate more aerodynamic noise. Finally, returning (RNO) to a normal mode of 15 operation of the wind turbine after having caused the wind turbine to invoke the air pressure and/or wind velocity variation.

Description

WIND TURBINE WITH OPERATION MODE CHANGE TO PREVENT BIRD COLLISION

FIELD OF THE INVENTION

The present invention relates to the field of wind turbines, more specifically the invention relates to a wind turbine capable of changing mode of operation for preventing airborne animal (bird, bat) collision with wind turbine.

BACKGROUND OF THE INVENTION

Bird or bat collision with wind turbines is a known problem. Animals are often killed by a collision, and it may further cause operational disturbance or even permanent damage of the wind turbine.

Various measures for deterring birds or bats from approaching a wind turbine, e.g. use of sound or light, can have an effect to deter the animals away from the wind turbine. Further, various means for detecting approaching birds or bats are known, and thus sound or light effects can be initiated when animals are detected.

However, separate components are required to generate light and noise effects to deter the animals away from a wind turbine, and for a windfarm with many wind turbines, individual components are required for each wind turbine to ensure local deterrence effect for each wind turbine.

SUMMARY OF THE INVENTION

Thus, according to the above description, it is an object of the present invention to provide a method for effectively preventing bird or bat collision with a wind turbine, preferably with a minimal need for extra components.

In a first aspect, the invention provides a method for deterring airborne animals to prevent collision between the airborne animal and a wind turbine, said method comprising :

- providing data from at least one data source regarding at least one parameter relevant for an airspace of the wind turbine, - analyzing said data according to an algorithm to determine presence of any one or more airborne animals in the airspace,

- in case it is determined that airborne animals are present, changing one or more parameters of operation of a rotor of the wind turbine, so as to cause the wind turbine to invoke an air pressure variation at a distance from the wind turbine, such as upstream or downstream of the wind turbine, to deter the airborne animal from approaching the wind turbine, and

- returning to a normal mode of operation of the wind turbine after having caused the wind turbine to invoke the air pressure variation.

Such method is advantageous, since it has proven possible to change operation of a wind turbine, e.g. blade pitch, yaw, and/or rotor rotation speed, so as to invoke an air pressure variation upstream of the wind turbine. It has been found that a static, a sudden, or a cyclic slowly or more rapidly variation in air pressure will cause attention of approaching airborne animals, and in response they will be deterred and change direction of flight, thus avoiding collision with the wind turbine. The use of the wind turbine itself, especially operation of its rotor, to cause a bird deterrence effect, eliminates the need for extra components, such as loudspeakers or laser light and the like, for preventing bird collision.

Since birds are sensitive to even small changes in static air pressure, changes in the air pressure will cause attention of approaching birds and e.g. cause the birds to change flying altitude accordingly. E.g. an air pressure increase may cause the birds to increase flying altitude and thereby fly above the wind turbine. A rapid air pressure variation in the form of audible noise, i.e. noise audible for the airborne animal, will also cause attention of the birds and deter them from a flight path that may cause collision.

Further, since the rotor blade(s) of the wind turbine can be used to generate aerodynamic noise to deter the birds, it is the most likely collision object itself which is the noise source assumed to deter the birds. This helps to increase the chance of a successful deterrence effect compared to a noise signal device located at a distance away from the wind turbine itself and at a different height. This is crucial for a large wind turbine with a large rotor diameter, e.g. larger than 100m. It has been realized that changing one or more parameters of operation of a rotor of the wind turbine may not only generate an air pressure variation but may also generate a wind velocity variation at a distance from the wind turbine such as upstream, downstream or sideways of the wind turbine or rotor.

Similarly, to the air pressure, the wind velocity can be affected by modifying blade pitch and/or rotor speed.

Variations in wind velocity comprises variations in wind speed and/or wind direction. Thus, the wind velocity field, i.e. distributions of wind speed and/or direction may be modified by changing one or more parameters of operation of a rotor of the wind turbine such as changing blade pitch and/or rotor speed.

The one or more parameters of operation of the rotor may be changed to generate an air pressure variation or a wind velocity variation, a variation of both at the same time or successive variations of air pressure and wind velocity.

Similarly to air pressure variations, variations in the wind velocity may have a deterrent effect on approaching flying objects such birds or bats.

Throughout the description, when an example or embodiment refers to air pressure variations generated by modifications of rotor operation parameters, it is understood the modifications of rotor operation parameters could equally be used for generating wind velocity variations. Thus, any example or embodiment referring to solutions and effects relating to air pressure variations applies equally to solutions and effects relating to wind velocity variations.

Especially, it is possible to operate one or more rotor blades to generate noise especially at a specific angular position of the rotor. This can be done to more specifically target the noise towards the area where it is estimated that an airborne animal will approach the wind turbine and thus more efficiently nudge the animal to change direction of flight away from the wind turbine. An estimation of the flight path of an approaching airborne animal can be based on input of data from e.g. a radar, a camera, microphones or the like, and thus such estimated flight path can be used to determine the specific operation of the wind turbine to obtain an optimal deterrence effect.

Even though the change in operation of the wind turbine to deter airborne animals may cause the wind turbine to produce less energy than optimal, the special collision preventing mode of operation can be limited only to the time when airborne animals approach the wind turbine, and as soon as it is detected that the animal(s) have passed, the wind turbine can return to a normal mode of operation. Thus, the reduced energy production is limited only to the period where the deterrence effect is needed.

The invention can for example be implemented in software on existing wind turbine controllers. Especially, a sensor, e.g. a radar, a lidar, a camera or the like can provide said data, especially data that indicate flight direction of incoming airborne animals.

In the following, preferred features and embodiments will be described.

By 'airspace of the wind turbine' is understood a space covering up to such as 20 m, 50 m, 100 m or 500 m measured from the rotor plane of the wind turbine. Most preferably, the airspace covers at least an upstream or downstream airspace at a distance from the wind turbine. The airspace may be delimited upwards, downwards and/or sideways relative to the upwind or pointing direction of the wind turbine rotor and e.g. according to horizontal and/or vertical angular spans. Alternatively, if the data from the data source involves data from a sensor located externally from the wind turbine, the airspace may be defined according to the scanning space of the sensor and the location of the sensor, e.g. defined by horizontal and/or vertical angular scanning spans of the sensor.

By 'to determine presence of any one or more airborne animals in the airspace' is to be understood to cover: that an airborne animal is near the wind turbine, or that a detected airborne animal is still at a long distance from the wind turbine, but that is determined to have an expected flight path or trajectory toward the wind turbine. By 'at a distance from the wind turbine' is understood any distance where it is realistic to invoke an air pressure that can be detected by the animals and thus cause a deterrence effect to cause the animals to change flight path and thus avoid collision with the wind turbine. Thus, the air pressure and/or wind velocity variation generated at a distance from the wind turbine covers such variations at locations in an airspace of the wind turbine such as locations in upwards, downwards and/or sideways directions relative to the pointing direction of the wind turbine rotor. The upwards and downwards directions may equally be termed upwind and downwind directions or upstream and downstream, respectively.

In preferred embodiments, the method comprises changing the one or more parameters of operation of the rotor of the wind turbine so as to provide an increase or decrease in air pressure upstream of the wind turbine to deter the airborne animals. Especially, the wind turbine rotor may be controlled to provide a static or a sudden increase of decrease in air pressure, and/or the wind turbine rotor may be controlled to provide a cyclic air pressure variation upstream of the wind turbine to deter the airborne animals.

In preferred embodiments, the method comprises changing pitch of at least one rotor blade of the wind turbine to invoke the air pressure variation. Especially, the pitch of the at least one rotor blade of the wind turbine may be controlled to generate increased noise to deter the airborne animals, such as tonal noise. Here, by 'noise' is understood noise which is audible to the airborne animals.

Specifically, the pitch of at least one rotor blade made be controlled to change in a cyclic manner to cause the wind turbine to generate noise to deter the airborne animals. This is efficient, since airborne animals are sensitive to noise within the frequency range 1-4 kHz, and noise in this frequency range can easily be generated by the operation of the rotor (e.g. pitch, rotor speed, yaw angle).

In some embodiments, the method comprises changing a torque of an electric generator of the wind turbine to generate increased noise to deter the airborne animals, especially tonal noise. Electric generator torque would be equivalent of electric generator current or power and this is known as capable of generating noise. The use of torque changes may be used as an alternative to pitch variations or in addition to pitch variations, e.g. so that pitch and torque variations are used simultaneously. Tonal noise can be generated where a frequency of a frequency converter is changed again and again. One or more frequencies at the same time may be changed, and in this way it is possible to generate dis-harmonic frequencies.

In some embodiments, the method comprises changing a pitch of at least one rotor blade dependent on an angular position of the at least one rotor blade during a rotor rotation, so as to cause the at least one rotor blade to generate increased noise at a predetermined angular position of the rotor. Specifically, said data may comprise data indicative of a position or direction relative to a rotor plane of the wind turbine of approaching airborne animals, and wherein said angular position of the rotor may be selected to generate increased noise in response to said position or direction of approaching airborne animals. The method may comprise estimating an area, such as estimating an area selected between upper, lower, left, right and center, of a rotor plane of the wind turbine where possible collision of the airborne animals with the wind turbine will occur, and determining the way to change operation of the wind turbine in response thereto, e.g. pitching rotor blade(s) to generate noise corresponding to the area of the rotor plane where it is estimated that the animal(s) will arrive. If direction of arrival of airborne animal(s) is estimated, then a change of yaw of the wind turbine accordingly may be initiated to increase or decrease air pressure towards the approaching airborne animals.

In some embodiments, the wind turbine is controlled to change the one or more parameters of operation of a rotor of the wind turbine, e.g. rotor blade pitching, in a cyclic manner to cause the wind turbine to generate a time varying noise to deter the airborne animals. Noise varying in a cyclic manner has proven to create more awareness by the airborne animals and thus helps to provide an increased deterrence effect. The cyclic manner can be selected in a way the noise is generated by each blade passing a given position/area of the rotor e.g. generate noise when each blade passes by the tower.

In some embodiment operation of the wind turbine rotor is controlled to generate a cyclic air pressure variation, in the sense that it may be assumed that airborne animals (birds) react on static pressure and therefore also likely react on "quasistatic" pressure variations, e.g. pulses at a frequency lower than the audible frequency range.

In some embodiments, operation of the wind turbine rotor is controlled to generate pressure variations within an audible frequency range.

In some embodiments, operation of the wind turbine rotor is controlled to generate pressure variations in a cyclic manner to cause the appearance from outside that the noise originates from one area of the rotor.

In preferred embodiments, the wind turbine is controlled to change at least one of: rotation speed of the rotor, and yaw of the wind turbine, so as to generate extra noise. By 'extra noise' is understood noise with a higher level or with an extra spectral component compared to noise generated by the wind turbine in a normal mode of operation, thus creating a deterrence effect.

Especially, extra noise may be generated by changing pitch of one or more rotor blade(s), but change of rotor blade pitch may be combined with change of yaw and/or increasing rotor speed.

Extra noise may be generated by activating a device in or on one or more rotor blade of the wind turbine so as to generate extra noise, such as a device activating vibration in or on one or more rotor blade to cause the rotor blade to emit audible noise, such as activating a fan or a pump of the wind turbine to cause one or more rotor blade to emit audible noise.

Extra noise may be generated in a root of one or more rotor blade, so as to cause blade resonation to generate a loudspeaker effect. Such noise may be generated by a loudspeaker, a vibration source, a mechanical actuator such as a hammer released by a magnet or similar.

Extra noise generation may especially be generated by activating one or more flaps of one or more rotor blade of the wind turbine to cause extra aerodynamic noise and/or extra mechanical noise by the flap activation, if the wind turbine is equipped with active flaps.

In preferred embodiments, the method comprise determining a direction of airborne animals approaching the wind turbine and changing said at least one parameter of operation of the rotor of the wind turbine in response thereto.

Preferably, said data comprises data from one or more sensors, such as a lidar, such as a radar, such as a camera, such as a microphone. Such data can be used to estimate flight path and time of arrival at the wind turbine. The sensor(s) may be mounted on the wind turbine or mounted in a mast or on the ground or on another wind turbine.

Said data may alternatively or additionally comprise data from a source external to the wind turbine, such as data comprising meteorological data. Said data may alternatively or additionally comprise clock data, such as a time of day, such as a day of year. Weather and time are known parameters influencing flight of birds and bats and can thus be used as a simple flight detection estimator, or as additional information to supplement data from on-site sensors.

It may be preferred that the method involves calculating or estimating, according to an algorithm, a loss of energy generation of the wind turbine caused by the changing of one or more parameters of operation of the rotor of the wind turbine to provide the collision preventing effect.

The method may comprise determining a risk of collision by detected airborne animals, and determining said changing of one or more parameters of operation of the rotor of the wind turbine accordingly. Especially, the method may involve selecting between a plurality of different sets of changing one or more parameters of operation of the rotor of the wind turbine in response to said risk. More specifically, the method may involve applying a weighting function between said risk and a measure of loss of energy calculated for a plurality of different sets of changing one or more parameters of operation of the rotor of the wind turbine. The changing of one or more parameters of operation of a rotor the wind turbine may be performed in response to a learning algorithm, such as an Artificial Intelligence algorithm. Especially, the learning algorithm may be configured to learn behavior of the airborne animals in response to said changing of one or more parameters of operation of a rotor the wind turbine, and to adapt the changing of one or more parameters of operation of a rotor the wind turbine accordingly, so as to improve airborne animal deterrence effect of said changes. Especially, the method may involve estimating a flight path of approaching airborne animal(s) based on the available data, and a learning algorithm may be used to improve such flight path estimation based on actual flight paths observed.

In preferred embodiments, the wind turbine is controlled to generate increased noise, especially aerodynamic noise, for deterring the airborne animals. This can be achieved in many ways. In normal operation, the dominant noise generation mechanism is trailing edge noise, and in the literature trailing edge noise is described as scaling with the fifth power of Mach number. Thus, rotor noise can be increased significantly with a small increase in rotor speed. Further, it is possible to change pitch of one or more blades to "pitch-in" the blade(s) to change an angle of attack which can increase noise generation. Even further, the rotor can be yawed to create cyclic changes in both flow speed and angle of attack via skewed inflow. This can increase noise in a cyclic manner, however, it has a load impact that may not be acceptable and must be evaluated an individual basis depending on the wind turbine, controller settings, site conditions, etc. Still further, stall promotion is another, but less preferred mechanism to temporarily promote noise. Basically, the blade pitch and/or rotor speed can be modified to change angle of attack and create what is known as separation noise or stall noise. Similarly, it is possible to promote stall in case of yawing the turbine to generate skewed inflow. Promoting stall can increase loads, but it is an efficient way of generating a high noise level for airborne animal deterrence.

In some embodiments, the method comprises controlling the wind turbine to change a pitch of at least one rotor blade during a rotor rotation, so as to cause the at least one rotor blade to generate increased noise at a predetermined angular position of the rotor. In some embodiments, the data comprises data indicative of a height of approaching airborne animals, and wherein the wind turbine is controlled to generate increased noise at an angular position of its rotor, e.g. by pitching one or more rotor blades, in response to said height of approaching airborne animals, especially corresponding to the height of approaching airborne animals so as to obtain a maximum deterrence effect on the animal(s).

In some embodiments, the method comprises estimating a flight path of the approaching airborne animals according to a flight path algorithm in response to the data regarding the airspace of the wind turbine. Especially, the data may comprise radar and/or video data, e.g. data provided by one or more radar devices and/or one or more cameras located at or near the windfarm, e.g. radar devices and/or cameras mounted on the wind turbine. Data for the flight path algorithm may further involve a clock input, since e.g. time of year and time of day are known to influence bird or bat behavior, and further a weather forecast may be provided as well.

Specifically, a flight path algorithm may comprise a learning algorithm, such as comprising an Artificial Intelligence algorithm, serving to train and thus improved the flight path algorithm in estimating the flight path of incoming airborne animals in response to the data, such as sensor data comprising video recordings.

The method may comprise detecting an actual flight path of airborne animals arriving to the windfarm, so as to learn actual behavior of airborne animals in response to activated collision preventing actions with the purpose of improving an algorithm determining the way to operate the wind turbine to provide the most efficient preventing mode of operation.

In preferred embodiments, the method comprises individually controlling operation of two or more wind turbines of a wind farm according to a determined collision preventing strategy. Especially, the method may involve individually controlling operation of rotors of the two or more wind turbines, so as to deter the airborne animals to fly outside the windfarm, e.g. by controlling parameters of operation to increase noise generation from the two or more wind turbines. Especially, the method may involve individually controlling operation of rotors of the two or more wind turbines, so as to nudge the airborne animals to enter a specific flight corridor through the windfarm, e.g. by controlling parameters of operation to increase noise generation from the two or more wind turbines. Especially, the generation of the flight corridor may involve curtailing, such as slowing down or stopping rotors, of the two or more wind turbines along the specific flight corridor through the windfarm, so as to provide a safe flight corridor for the airborne animals.

Preferred embodiments comprise controlling operation of a rotor of the wind turbine, such as controlling pitch and/or rotor speed of one or more rotor blades of the one or more wind turbines, so as to increase generation of noise to deter or nudge the airborne animals. Specifically, the method may comprise individually controlling operation of rotors of two or more of the plurality of wind turbines position at a periphery of the windfarm so as to increase generation of noise, such as controlling pitch and/or rotor speed, in order to deter the airborne animals to fly outside the windfarm. Specifically, the method may comprise individually controlling operation of rotors of two or more wind turbines position at a periphery of the windfarm so as to increase generation of noise, such as controlling pitch and/or rotor speed, in order to deter the airborne animals to fly at a higher altitude to fly above the windfarm.

In some embodiments, the method comprises estimating a horizontal flight angle relative to the wind turbine of the airborne animal(s) when reaching the wind turbine, and determining how to operate the wind turbine to provide an optimal deterrence effect dependent on the horizontal flight angle. Especially, the deterrence operation of the wind turbine may be determined dependent on the horizontal flight angle, and e.g. also dependent on the area of the rotor of the wind turbine. In some cases, a deterrence operation of deterring the airborne animals to fly away from the wind turbine is selected, but in some cases a curtailment operation of slowing down or stopping the rotor of the wind turbine may be selected, e.g. if the airborne animal(s) are heading towards a central part of the rotor plane of the wind turbine.

In case the wind turbine forms part of a windfarm with a plurality of other wind turbines, the method may comprise determining a coordinated operation of a plurality of wind turbines to nudge the airborne animals to follow a flight path with a minimal risk of collision with any wind turbine of the windfarm.

Especially, the method may comprise determining different collision preventing strategies for a plurality of wind turbines to nudge the airborne animals to a flight path with a minimal impact with wind turbines of the windfarm.

Especially, the method may comprise estimating a flight path, such as a horizontal flight path and/or flight height, of the airborne animals in response to a selected collision preventing strategy for the first wind turbine, so as to determine which neighbor wind turbine the airborne animals will approach after the first wind turbine, thus enabling collision preventing control of the neighbor wind turbine. In this way it is possible to provide a coordinated individual control of a plurality of wind turbines to ensure a collective collision preventing strategy.

According to some embodiments, the step of analyzing data may be omitted or may be limited to simple processing of predefined data protocols. For example, the data source may comprise an external sensor capable of detecting presence of airborne animals in an airspace of the wind turbine and configured to transmit data indicating presence or non-presence of airborne animals. Thus, the step of analyzing data may be performed by a controller of the wind turbine, or it may be performed externally and just communicated to the wind turbine as a simple command.

In some embodiments, the method comprises steering wake (using calibrated yaw error and/or cyclic pitch control) to influence the flight path of an airborne animal approaching from downstream.

In some embodiments, the method comprises taking into account an operating state of the wind turbine in a collision path and use a neighbor wind turbine to generate noise if airborne animal is at risk of colliding with the wind turbine, if the wind turbine is stopped, e.g. due to planned or unplanned maintenance, and therefore can not use its own rotor noise or wake to deter the airborne animal. In some embodiments, the method comprises taking into account an operating status of a neighbor wind turbine when determining an optimal collision preventing strategy. This is advantageous e.g. if some wind turbines of a windfarm are down to planned or unplanned maintenance, since it might then make sense to include these in a safe flight corridor.

In some embodiments, the method comprises identifying an airborne animal species based on sensor data and performing a species-specific collision preventing control of operation of the wind turbine. In this way, an optimized deterrence or nudging effect may be obtained. E.g. for some species extra noise generation may be most effective, while for some species increase or decrease of air pressure may be most effective.

In some embodiments, the method comprises adding a feedback loop to recalculate an estimated flight path and update the collision preventing strategy accordingly based on an actual airborne animal flight path observed by sensors.

In some embodiments, the method comprises determining a collision preventing strategy dependent on a site-specific noise requirement and measured and/or simulated noise level. For example, it may be preferred to choose to curtail at night time instead of causing the wind turbine to generate extra noise, if at a specific site the noise requirements is stricter at night and that a noise-based collision preventing strategy would exceed night time noise limits.

In some embodiments, the method comprises choosing an optimal collision preventing strategy based on simulated or measured wind turbine loads. E.g. this may allow a louder and thus more effective response on the airborne animal, such as to operate the wind turbine to generate stall noise when operating loads permit this.

In some embodiments, the method comprises using a noise generating mechanism to deter farm pests which have been detected in the airspace of wind turbine or on ground within an area near the wind turbine.

In a second aspect, the invention provides a wind turbine comprising

- a rotor comprising a plurality of rotor blades,

- an electric generator coupled to the rotor, and - a controller for controlling operation of the wind turbine, wherein the controller comprises a processor, and wherein the controller is arranged

- to receive data from at least one data source regarding at least one parameter relevant for an airspace of the wind turbine, such as metrological data, such as one or more sensed parameters for the airspace of the wind turbine,

- to analyze said data according to an algorithm to determine presence of any airborne animals,

- to change one or more parameters of operation of the rotor of the wind turbine, so as to cause the wind turbine to invoke an air pressure variation at a distance from the wind turbine, such as upstream or downstream of the wind turbine, to deter the airborne animals from approaching the wind turbine, in case it is determined that airborne animals are present, and

- to return to a normal mode of operation of the wind turbine after having caused the wind turbine to invoke the air pressure variation.

In preferred embodiments, the wind turbine comprises a tower, a nacelle in which the electric generator is arranged, and wherein the rotor comprises three rotor blades. Especially, the wind turbine may be configured to produce at least 1 MW electric power, such as 1-10 MW, or more than 10 MW of electric power.

According to an embodiment, the controller is arranged to receive data from at least one data source wherein the data indicates presence or non-presence of any airborne animals. For example, the data source may be an external sensor capable of detecting presence of airborne animals in an airspace of the wind turbine. In this case, the step of analyzing data may be omitted or may be limited to simple processing of predefined data protocols from the external sensor.

Furthermore, it is to be understood that the functions defined for the controller for controlling operation of the wind turbine may be partly or fully performed by a controller for controlling operation of the windfarm. Especially, the steps of receiving data, analyzing data, controlling operation, and returning to normal operation, may all be, or at least partly be, performed a windfarm controller, and the collision preventing operational control changes and/or the return to normal operation may be determined from the windfarm controller and communicated to the wind turbine controller as simple commands.

In a third aspect, the invention provides a wind farm comprising a plurality of wind turbines according to the second aspect.

Especially, the windfarm may comprise:

-a windfarm controller comprising a processor, wherein the windfarm controller is configured

- to estimate a flight path of the approaching airborne animals, such as flight height and/or horizontal flight path in relation to the windfarm of airborne animals approaching the windfarm, in case it is determined that airborne animals are approaching the windfarm,

- to determine a collision preventing strategy in response to said estimated flight path,

- to send a control signal to control operation of one or more selected wind turbines of the plurality of wind turbines of the windfarm according to the determined collision preventing strategy as a measure of preventing collision between the wind turbines of the windfarm, and

- to send a control signal so as to cause the one or more wind turbines to return to a normal operation.

Especially, such windfarm can utilize the capability of the wind turbines to deter airborne animals by means of generating noise, and depending on the estimated flight path, deterrence effect can be controlled in a coordinated manner between a series of neighbor wind turbines to deter the airborne animals away from the windfarm or to nudge the airborne animals to follow a safe flight corridor of curtailed or stopped wind turbines through the windfarm.

It is to be understood that the same advantages and preferred embodiments and features described for the first aspect apply as well for the second and third aspects, and the aspects may be mixed in any way. BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described in more detail with regard to the accompanying figures of which

FIG. 1 illustrates a wind turbine embodiment,

FIG. 2 illustrates a possible division of a rotor plane of a wind turbine which is used in the estimation of possible arrival of airborne animal(s) in order to influence which collision preventing mode of operation to follow, and

FIG. 3 illustrates steps of a method embodiment.

The figures illustrate specific ways of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an example of a wind turbine according to the invention with typically two or three rotor blades BL which serve to drive an electric generator GN located inside the nacelle NC on top of a tower. Such wind turbine may generate an electric power of at least 1 MW, such as 2-10 MW, or more.

The wind turbine has a controller CL with a processor. The controller serves to control operation of the wind turbine, such as rotor speed RS, pitch PT of the blades BL and yaw YW of the nacelle NC. According to the invention the controller CL is arranged to receive data from at least one data source, such as a sensor SN which is capable of detecting airborne animals B, such as birds of bats, in the airspace of the wind turbine, especially upstream of the wind turbine.

The controller CL then analyzes data from the sensor SN according to an algorithm to determine presence of any airborne animal B. In case airborne animals B are detected and estimated to be heading towards the wind turbine, the controller CL is configured to change one or more parameters PT, YW, RS of operation of the rotor of the wind turbine, so as to cause the wind turbine to invoke an air pressure variation APV, e.g. upstream of the wind turbine, to deter the airborne animals B from approaching the wind turbine. Preferably, the air pressure variation APV may include an increased noise level, especially an increased noise level in the frequency range including 1-4 kHz where birds are sensitive to noise and thus a maximum deterrence effect can be obtained to deter the animals B away from the wind turbine. This can especially be done by changing pitch PT of one or more of the blades BL to produce an increased aerodynamic noise. To further increase deterrence effect, the extra noise may be provided in a cyclic manner, e.g. by varying pitch PT with a frequency of 0.1-2 Hz, thus causing a cyclic variation in noise from the blades BL.

However, the wind turbine rotor may also be controlled to provide a static air pressure increase or decrease APV which can also have a deterrence effect on the airborne animals B, since they are sensitive with respect to static air pressure.

Preferably, the controller CL can detect, when airborne animals B have passed the wind turbine, and then the controller is configured to return to a normal mode of operation of the wind turbine.

The controller CL may especially be configured for a remote control of the deterrence effect, e.g. by a windfarm controller being configured to trigger the deterrence effect by transmitting a control signal to cause the controller CL to enter one or more deterrence modes of operation to deter airborne animals B. In this way, if the wind turbine is part of a windfarm, a plurality of wind turbines can cooperate in a coordinated manner to more effectively deter airborne animals B away from the windfarm to prevent collision.

Especially, the wind turbine of the present invention is suited for forming part of a windfarm, and the wind turbine may be controlled with respect to its operation in accordance with an external windfarm controller, especially the windfarm controller may be configured to determine a collision preventing strategy involving controlling operational conditions of two or more wind turbines of the windfarm and then controlling operational conditions of the two or more wind turbines accordingly. The use of light or sound signals to deter airborne animals may be used in addition, but it has been found that such measures may be eliminated, since operation of the wind turbine can be very efficient in deterring or nudging the animal(s) since it is possible to generate noise by the wind turbine, even rotor angle specific noise and/or temporally varying noise which may have a significant impact of the animal(s).

FIG. 2 illustrates a rotor plane of a wind turbine, and the area of the rotor plane is shown as divided in different zones or area, here shown as: upper area U_A, left area L_A, right area R_A, lower area LW_A, and center area C_A.

In preferred embodiments, the wind turbine controller can estimate which of these areas of the wind turbine where it is most likely that incoming airborne animal(s) will arrive. This is found to be important to determine how to most efficiently control the mode of operation of the rotor of the wind turbine for optimal deterrence effect. This can be utilized e.g. to control extra noise generation of the wind turbine to be most pronounced at the angular position of a rotor blade corresponding to the expected area of arrival of the animal(s) to maximize the deterrence effect, e.g. by controlling the pitch of one or more blades to cause this effect. Especially, it may be determined to curtail or completely stop the wind turbine in case animal(s) are estimated to fly towards the center area C_A of the rotor. If animal(s) are estimated to fly towards other areas L_A, R_A, U_A, LW_A of the rotor, a deterrence strategy may be chosen.

To supplement deterrence at long distances from the first wind turbine, laser light ultraviolet light may be used to supplement the operation of the wind turbine itself.

FIG. 3 illustrates steps of a method embodiment, i.e. a method for deterring airborne animal(s) to prevent collision between airborne animal(s) and a wind turbine. The method comprises providing data PD from at least one data source regarding at least one parameter relevant for an airspace of the wind turbine. This may involve receiving data from a radar, a lidar or a camera or other sensor capable of detecting birds in the airspace of the wind turbine. Next, analyzing said data AD according to an algorithm to determine presence of any one or more airborne animals in the airspace. In case it is determined that airborne animals are present, then the method involves entering a deterrence mode of operation which comprises changing C_O one or more parameters of operation of a rotor of the wind turbine, e.g. blade pitch, so as to cause the wind turbine to invoke an air pressure variation at a distance from the wind turbine to deter the airborne animal from approaching the wind turbine. Especially, this may involved generating extra noise by pitching one or more rotor blades to increase aerodynamic noise. Finally, returning RNO to a normal mode of operation of the wind turbine after having caused the wind turbine to invoke the air pressure variation.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is to be interpreted in the light of the accompanying claim set. In the context of the claims, the terms "including" or "includes" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

1. A method for deterring airborne animals to prevent collision between the airborne animal and a wind turbine, said method comprising:

- providing data (PD) from at least one data source regarding at least one parameter relevant for an airspace of the wind turbine,

- analyzing said data (AD) according to an algorithm to determine presence of any one or more airborne animals in the airspace,

- in case it is determined that airborne animals are present, changing (C_O) one or more parameters of operation of a rotor of the wind turbine, so as to cause the wind turbine to invoke an air pressure and/or wind velocity variation at a distance from the wind turbine, such as upstream or downstream of the wind turbine, to deter the airborne animal from approaching the wind turbine, and

- returning (RNO) to a normal mode of operation of the wind turbine after having caused the wind turbine to invoke the air pressure and/or wind velocity variation.

2. The method according to claim 1, comprising changing the one or more parameters of operation of the rotor of the wind turbine so as to provide an increase or decrease in air pressure and/or wind velocity upstream or downstream of the wind turbine to deter the airborne animals, such as a static or sudden increase or decrease in air pressure and/or wind velocity or an oscillating air pressure and/or wind velocity variation.

3. The method according to any of the preceding claims, comprising changing pitch of at least one rotor blade of the wind turbine to invoke the air pressure and/or wind velocity variation.

4. The method according to claim 3, comprising changing the pitch of the at least one rotor blade of the wind turbine to generate increased noise to deter the airborne animals, such as tonal noise.

5. The method according to claim 4, comprising changing the pitch of at least one rotor blade in a cyclic manner to cause the wind turbine to generate noise to deter the airborne animals.

6. The method according to claim 5, comprising changing a pitch of at least one rotor blade dependent on an angular position of the at least one rotor blade during a rotor rotation, so as to cause the at least one rotor blade to generate increased noise at a predetermined angular position of the rotor.

7. The method according to claim 6, wherein said data comprises data indicative of a position or direction relative to a rotor plane of the wind turbine of approaching airborne animals, and wherein said angular position of the rotor is selected to generate increased noise in response to said position or direction of approaching airborne animals.

8. The method according to any of the preceding claims, comprising changing the one or more parameters of operation of a rotor of the wind turbine the at least one rotor blade in a cyclic manner to cause the wind turbine to generate a time varying noise to deter the airborne animals.

9. The method according to any of the preceding claims, comprising changing at least one of: rotation speed of the rotor, yaw of the wind turbine, and a torque of an electric generator coupled to the rotor, so as to generate extra noise.

10. The method according to any of the preceding claims, comprising activating a device in or on one or more rotor blades of the wind turbine so as to generate extra noise, such as activating a flap on one or more rotor blade to generate extra aerodynamic noise, such as a device activating vibration in or on one or more rotor blade to cause the rotor blade to emit audible noise, such as activating a fan or a pump of the wind turbine to cause one or more rotor blade to emit audible noise.

11. The method according to any of the preceding claims, comprising determining a direction of airborne animals approaching the wind turbine and changing said at least one parameter of operation of the rotor of the wind turbine in response thereto.

12. The method according to any of the preceding claims, comprising providing said data from one or more sensors, such as a lidar, such as a radar, such as a camera.

13. The method according to any of the preceding claims, comprising providing said data from a source external to the wind turbine, such as data comprising meteorological data.

14. The method according to any of the preceding claims, comprising determining a risk of collision by detected airborne animals, and determining said changing of one or more parameters of operation of the rotor of the wind turbine accordingly.

15. The method according to any of the preceding claims, wherein said changing of one or more parameters of operation of a rotor the wind turbine is performed in response to a learning algorithm, such as an Artificial Intelligence algorithm, wherein the learning algorithm is configured to learn behavior of the airborne animals in response to said changing of one or more parameters of operation of a rotor the wind turbine, and to adapt the changing of one or more parameters of operation of a rotor the wind turbine accordingly, so as to improve airborne animal deterrence effect of said changes.

16. A wind turbine comprising

- a rotor comprising a plurality of rotor blades (BL),

- an electric generator (GN) coupled to the rotor, and

- a controller (CL) for controlling operation of the wind turbine, wherein the controller comprises a processor, and wherein the controller is arranged - to receive data from at least one data source (SN) regarding at least one parameter relevant for an airspace of the wind turbine, such as metrological data, such as one or more sensed parameters for the airspace of the wind turbine,

- to analyze said data according to an algorithm to determine presence of any airborne animals,

- to change one or more parameters of operation of the rotor of the wind turbine, so as to cause the wind turbine to invoke an air pressure and/or wind velocity variation at a distance from the wind turbine, such as upstream or downstream of the wind turbine, to deter the airborne animals from approaching the wind turbine, in case it is determined that airborne animals are present, and

- to return to a normal mode of operation of the wind turbine after having caused the wind turbine to invoke the air pressure and/or wind velocity variation.