Abstract: Improvements Relating to Wind Turbines A wind turbine apparatus and a method of operating said wind turbine to maintain the load on the rotor blade below a predetermined threshold level is provided. The method comprises: measuring load at a root end of the rotor blade; measuring an acceleration at a location on the rotor blade outboard from the root end, the acceleration being caused by transient loads acting on the rotor blade; and controlling the wind turbine based upon the measured load and the measured acceleration to maintain the load on the rotor blade below a predetermined threshold level.

Abstract: A system for identifying the likelihood of a wind turbine rotor blade striking a wind turbine tower comprises a device for sensing bending of a wind turbine rotor blade and a device for sensing bending of a wind turbine tower. In a preferred embodiment Long Period Grating (LPG) sensors are used to measure bending of the tower. Preferably a plurality of LPG sensors is provided along the length of the blade. In one embodiment at least one of the LPG sensors comprises two sensing elements arranged to sense in perpendicular directions. In another embodiment a plurality of LPG sensors are provided each on different sides of the wind turbine tower. A processor uses the sensed blade and tower bending to determine whether the distance between the blade and the tower will be below a predetermined minimum value.

Abstract: The present invention relates to a method and to a wind turbine for determining the tip angle of a blade of a wind turbine rotor during rotation of the rotor. The method comprising: (a) transmitting a light signal from a first blade of the wind turbine rotor towards a second blade of the rotor; (b) receiving the light signal at the second blade of the rotor; and (c) calculating the tip angle of the first or second blade based upon characteristics of the received light signal.

Abstract: Improvements Relating to Wind Turbine Sensors A sensor apparatus for a wind turbine is described. The apparatus comprises a sensor and a heating system. The heating system comprises an optical fibre arranged to transmit electromagnetic radiation from a light source to the sensor. The sensor is irradiated by the electromagnetic radiation thereby heating the sensor and preventing or reducing ice accretion.

Abstract: A system and method of detecting damage to a wind turbine blade uses one or more fluorescent optical fibers comprising a fluorescent material having an excitation wavelength that is selected such that the material fluoresces upon exposure to ambient radiation at the wind turbine blade, wherein the one or more optical fibers are operatively mounted within the wind turbine blade such that upon damage to the wind turbine blade at least a part of the optical fiber is exposed at the surface of the blade causing the optical fiber to fluoresce; a light detector for receiving a light signal from one or from both ends of the one or more optical fibers upon excitation of the fluorescent material and outputting a signal based on the light signal; and a controller coupled to the light detector to receive the signal.

Abstract: The invention comprises a wind turbine optical wind sensor 10 mounted on the rotor 4 of a wind turbine, either on the blades 5 or on the hub 5. The sensor comprises a plurality of light sources, each generating respective sensor beams made up of at least two individual parallel component sensor beams. Transit times for particulate matter carried in the wind breaking the at least two component sensor beams are used to provide one or more of an indication of wind speed and/or a component of vertical wind speed. The data received from the sensor can be used in control processes for the operation of the wind turbine, particularly for temporarily pitching the rotor blades in adverse wind conditions, such as when vertical wind gusts are detected.

Abstract: To identify abnormal behavior in a turbine blade, a failure detection system generates a “fingerprint” for each blade on a turbine. The fingerprint may be a grouping a dynamic, physical characteristics of the blade such as its mass, strain ratio, damping ratio, and the like. While the turbine is operating, the failure detection system receives updated sensor information that is used to determine the current characteristics of the blade. If the current characteristics deviate from the characteristics in the blade's fingerprint, the failure detection system may compare the characteristics of the blade that deviates from the fingerprint to characteristics of another blade on the turbine. If the current characteristics of the blade are different from the characteristics of the other blade, the failure detection system may change the operational mode of the turbine such as disconnecting the turbine from the utility grid or stopping the rotor.

Abstract: The invention provides a method and system of monitoring bending strain on a wind turbine blade. The method in one aspect comprises: locating at least three strain sensors on the turbine blade, in use each strain sensor providing a strain measurement, the strain sensors located such that edgewise and flapwise bending can be determined from the strain measurements; calculating a plurality of resultant bending strains using the strain measurements; calculating an average resultant bending strain from the plurality of resultant bending strains; and calculating a confidence value for a first sensor based on a comparison of resultant bending strains derived from the strain measurement from the first sensor with the average resultant bending strain.

Abstract: The invention relates to an optical detector for determining the relative wind direction (attack angle) relative to a rotating or stationary wind turbine rotor. The optical detector comprises an output part which transmits distinguishable light beams out from a rotor blade in different predetermined directions. The beams may be distinguishable by light color, by the time the individual beams are emitted and/or by different amplitude modulation frequencies or other modulations of the individual beams. By determining pulse times of scattered light from wind borne particles moving in or through the different distinguishable beams, or determining the number of pulses within a period, it is possible to determine the relative wind direction or angle of attach as the predetermined direction of a beam which has the longest pulse times or the fewest number of pulses within a given period of time.

Abstract: The rotor blades of a wind turbine each have a plurality of fibre-optic pressure variation sensors which can detect the onset of a stall condition. The output of the stall condition sensors is input to a stall count circuit which increases a stall count signal each time a stall indication is received. The stall count signal is decayed exponentially over time and the current signal is summed with the decayed signal from a previous sampling period to form a value from which a stall margin is determined. An ?:? curve of tip speed to wind speed ratio ? against pitch angle reference ? is then determined from the stall margin.

Abstract: A wind turbine includes an optical sensor system comprising one or more optical sensors comprising: a sensor membrane; a light source for illuminating a surface of the sensor membrane; an optical dispersive element arranged to disperse the light from the light source; and a light detector for receiving a portion of the dispersed light beam after reflection from the surface of the sensor membrane and dispersion of the light beam by the optical dispersive element. The wavelength of the light received at the light detector varies as a function of the displacement of the sensor membrane and the light detector operatively provides an output based on changes in the wavelength of the received light. The wind turbine is operable based on an input to a wind turbine control system received from the optical sensor system.

Abstract: A system and method of detecting damage to a wind turbine blade uses one or more fluorescent optical fibres comprising a fluorescent material having an excitation wavelength that is selected such that the material fluoresces upon exposure to ambient radiation at the wind turbine blade, wherein the one or more optical fibres are operatively mounted within the wind turbine blade such that upon damage to the wind turbine blade at least a part of the optical fibre is exposed at the surface of the blade causing the optical fibre to fluoresce; a light detector for receiving a light signal from one or from both ends of the one or more optical fibres upon excitation of the fluorescent material and outputting a signal based on the light signal; and a controller coupled to the light detector to receive the signal.

Abstract: The invention comprises a wind turbine having an optical wind sensor 10. The optical wind sensor generates one or more multiple beams of light 42, each of which forms a sensor beam pointing along a sensor axis. Where more than one sensor beam is used the beams are arranged so that the different sensor axes lie at least partly orthogonal to each other, allowing the wind direction 40 to be detected for any direction of wind. Each multiple sensor beam comprises at least two individual sensor beams having different respective wavelengths of light. The different color of the individual light beams allows the sensor system to detect which of the light beams is triggered first when matter in the wind passes through the beam and reflects light back to light collecting device.

Abstract: The invention comprises a wind turbine optical wind sensor 10 mounted on the rotor 4 of a wind turbine, either on the blades 5 or on the hub 5. The sensor comprises a plurality of light sources, each generating respective sensor beams made up of at least two individual parallel component sensor beams. Transit times for particulate matter carried in the wind breaking the at least two component sensor beams are used to provide one or more of an indication of wind speed and/or a component of vertical wind speed. The data received from the sensor can be used in control processes for the operation of the wind turbine, particularly for temporarily pitching the rotor blades in adverse wind conditions, such as when vertical wind gusts are detected.

Abstract: A wind turbine includes an optical sensor system comprising one or more optical sensors comprising: a sensor membrane; a light source for illuminating a surface of the sensor membrane; an optical dispersive element arranged to disperse the light from the light source; and a light detector for receiving a portion of the dispersed light beam after reflection from the surface of the sensor membrane and dispersion of the light beam by the optical dispersive element. The wavelength of the light received at the light detector varies as a function of the displacement of the sensor membrane and the light detector operatively provides an output based on changes in the wavelength of the received light. The wind turbine is operable based on an input to a wind turbine control system received from the optical sensor system.

Abstract: A system for identifying the likelihood of a wind turbine rotor blade striking a wind turbine tower comprises a device for sensing bending of a wind turbine rotor blade and a device for sensing bending of a wind turbine tower. In a preferred embodiment Long Period Grating (LPG) sensors are used to measure bending of the tower. Preferably a plurality of LPG sensors is provided along the length of the blade. In one embodiment at least one of the LPG sensors comprises two sensing elements arranged to sense in perpendicular directions. In another embodiment a plurality of LPG sensors are provided each on different sides of the wind turbine tower. A processor uses the sensed blade and tower bending to determine whether the distance between the blade and the tower will be below a predetermined minimum value.

Abstract: A sensor system for measuring an operating parameter of a wind turbine component is described. The fibre optic sensor system comprises a light source for outputting light in a predetermined range of wavelengths, and an optical fibre comprising a long Fibre Bragg Grating, extending continuously over a length of the optical fibre to provide a continuous measurement region in the optical fibre. The optical fibre is coupled to the wind turbine component such that the continuous measurement region is located at a region of the wind turbine component to be sensed, and such that the grating period at each location in the continuous measurement period is dependent upon the value of the operating parameter at that location. A light detector receives light from the optical fibre, and provides an output signal to the controller indicating the intensity of the received light; based on the detected light, a value for the operating parameter is determined.

Abstract: The invention provides a method and system of detecting ice or other foreign matter on a wind turbine blade or damage to a wind turbine blade. The method in one aspect comprises: measuring twisting torque on the blade about its longitudinal axis to provide a detected torque signal; comparing a value based on the detected torque signal with a comparison value, the comparison value derived from one or more measured parameters having a predetermined relationship with the twisting torque about the longitudinal axis of the blade when the blade is operating under normal operating conditions; and determining that ice or other foreign matter is on the blade or that the blade is damaged if the value based on the detected torque signal differs from the comparison value by more than a predetermined amount. Wind turbine blades are designed such that any change in the shape of the blade reduces twisting torque on the blades significantly.

Abstract: The invention provides a method and system of monitoring bending strain on a wind turbine blade.

Abstract: The invention provides a wind turbine blade comprising a first shell, having a first bonding region, and a second shell having a second bonding region, wherein the second bonding region of the second shell is bonded to the first bonding region of the first shell; and a temperature sensor positioned between the first bonding region and the second bonding region. Having a temperature sensor positioned within the turbine blade, in the region at which the two shells of the turbine blade are bonded together, allows for accurate determination and control of the temperature of the critical bonding regions during blade manufacture. The temperature sensor may be used during the service life of the wind turbine blade to detect delamination of the wind turbine blade.