Individual blade noise measurement system and method for wind turbines

A method for configuring blades of a wind turbine for low noise generation. The method includes providing at least one noise measuring device. The noise measuring device is arranged and disposed in a position to measure noise of the blades during rotation. The wind turbine is configured to include a rotational trigger, the rotational trigger being arranged to provide a signal at a predetermined rotational position of the wind turbine blades. One or more of the blades is configured with an aerodynamic modifying device. Noise level is measured with the noise measuring device during wind turbine operation. The noise produced by each of the blades is determined. The blades are configured in response to the noise determined for each of the blades. A method for measuring the noise level generated by an individual blade and a wind turbine configured for desired noise level are also disclosed.

FIELD OF THE INVENTION

The present invention is directed to methods for installing and/or configuring wind turbines. In particular, the present invention is directed to measuring, analyzing and configuring wind turbines for operation based upon noise level generated by the wind turbine blades.

BACKGROUND OF THE INVENTION

Recently, wind turbines have received increased attention as environmentally safe and relatively inexpensive alternative energy sources. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient.

Generally, a wind turbine includes a rotor having multiple blades. The rotor is mounted to a housing or nacelle, which is positioned on top of a truss or tubular tower. Utility grade wind turbines (i.e., wind turbines designed to provide electrical power to a utility grid) can have large rotors (e.g., 30 or more meters in length). In addition, the wind turbines are typically mounted on towers that are at least 60 meters in height. Blades on these rotors transform wind energy into a rotational torque or force that drives one or more generators. As the blades are rotated by the wind, noise is inherently generated.

International standards exist to measure noise level produced by wind turbines. The existing system and standards measure an overall noise level produced by the wind turbine, typically from a fixed point. This overall noise level is utilized to configure the wind turbine with noise reduction equipment. Configuring of wind turbine blades for noise levels requires long and costly steps including outfitting of the blades, evaluating the blade set over a testing period wherein the process is then repeated for new blade arrangement. Such steps require multiple iterations, each iteration requires rigging of all of the blades. The rigging of these blades may require lifting equipment, personnel and time. Wind turbine blades and associated equipment may be large or heavy, requiring specialized equipment that is expensive to operate. Further, wind turbines may be installed on uneven terrain and/or on very high towers (e.g., towers that are at least 60 meters in height) that are inaccessible to mobile land-based cranes. The installation, servicing and configuration may be very expensive and time consuming.

What is needed is a method and system for configuring and/or analyzing wind turbine blade noise level that permits configuration of the wind turbine and provides individual blade noise levels for configuration and operation of the wind turbine, wherein the process does not require the expensive and labor-intensive processes of the known noise level measurement and configuration systems.

SUMMARY OF THE INVENTION

One aspect of the present invention includes a method for configuring blades of a wind turbine for low noise level generation. The method includes providing at least one noise measuring device. The noise measuring device is arranged and disposed in a position to measure noise of the blades during rotation. The wind turbine is configured to include a rotational trigger, the rotational trigger being arranged to provide a signal at a predetermined rotational position of the wind turbine blades. One or more of the blades is configured with an aerodynamic modifying device. Noise level is measured with the noise measuring device during wind turbine operation. The noise level produced by each of the blades is determined. The blades are configured in response to the noise level determined for each of the blades.

Another aspect of the present disclosure includes a method for determining the noise level generated by a wind turbine blade. The method includes providing at least one noise measuring device and arranging and disposing the noise measuring device in a position to measure noise level of the blades during rotation. The wind turbine is configured to include a rotational trigger, the rotational trigger being arranged to provide a signal at a predetermined rotational position. Noise level is measured with the noise measuring device during wind turbine operation. Time between signals generated by the rotational trigger is measured. The noise level measured by the noise measuring device is correlated to the time between signals to determine the noise level generated by each blade during operation. The noise level produced by each of the blades is thereby determined.

Still another aspect of the present disclosure includes a wind turbine configured for desired noise production. The wind turbine includes a plurality of wind turbine blades. In addition, a rotational trigger is arranged and disposed to provide a signal at a predetermined rotational position of the blades. Each of the blades is individually configured for noise reduction and the configuration including one or more the blades having aerodynamic modification devices, the arrangement of the aerodynamic modification devices is determined in response to noise level measured on each individual blade.

Advantages to an embodiment of the disclosure include the ability for different noise reduction measures to be tested simultaneously at one turbine. In addition, the noise measurement and analysis procedure permit the determination of individual noise level and noise level spectra of wind turbine blades.

The ability to measure noise level at individual blades allows time and cost reduction due to fewer measurements, crane actions and reduced blade preparation. Furthermore, the method of the present disclosure has lower uncertainty and greater noise level measurement detail than standard International Standard measurements.

The method also allows consistent and reliable noise level measurements at various dissimilar locations substantially independent of the environmental and site conditions.

DETAILED DESCRIPTION OF THE INVENTION

As shown inFIG. 1, a wind turbine100generally comprises a nacelle102housing a generator (not shown inFIG. 1). Nacelle102is a housing mounted atop a tower104, only a portion of which is shown inFIG. 1. The height of tower104is selected based upon factors and conditions known in the art, and may extend to heights up to 60 meters or more. The wind turbine100may be installed on any terrain providing access to areas having desirable wind conditions. The terrain may vary greatly and may include, but is not limited to, mountainous terrain or off-shore locations. Wind turbine100also comprises a rotor106that includes one or more rotor blades108attached to a rotating hub110. Although wind turbine100illustrated inFIG. 1includes three rotor blades108, there are no specific limits on the number of rotor blades108required by the present invention. As the blades108rotate, noise is generated. “Noise level”, “noise” and grammatical variations thereof, as utilized herein includes a unit of measure of sound pressure level or sound power level measured in decibels or other sound pressure level units.

FIG. 2shows a wind turbine100having a first blade201, a second blade203, and a third blade205rotatable in direction207. A noise measuring device209is arranged at a location disposed to measure noise from individual blades. The noise measuring device209may be any device capable of measuring noise or sound pressure level, including, but not limited to a microphone, acoustical camera, laser doppler vibrometer or other sound measuring or detection device, including devices that directly measure sound pressure level or indirectly via contact-less measurements. The noise-measuring device209is positioned in a location suitable for measuring the noise generated from a single blade108, while noise generated by the other blades in minimized to reduce interference with the noise measurements of the individual blades. For example, the noise-sensing device may be disposed below the down stroke of the blades108. However, the positioning is not so limited and may include any location in which the magnitude of the noise generated by one blade is distinguishable from the noise generated by the other blades108.

FIG. 2includes first blade201in a 12 o'clock or zero degree position (i.e., a vertical position above the hub110). In one embodiment, a rotational trigger is activated by the position of first blade201. As the blades108rotate in direction207, the time required for the first blade201to rotate and return to the zero degree position is measured by measuring the time between signals from the rotational trigger. The time is correlated to a rotational position (i.e., degrees from 0° to 360°) so that the measured sound power level may be further correlated to the blade108position. The rotational trigger may be any device that permits the recording of a position of one or more blades108. For example, the rotational trigger may be activated at a single position during a single rotation of the blades108or may be at several or continuously along the rotation of the blades108. In one embodiment, the rotational trigger is a mechanical feature, such as a protrusion, indentation, feature or lug on the shaft about which the hub110and blades108rotate. As the mechanical feature passes a predetermined point during rotation, a signal is produced and time is recorded. In other embodiment, the rotational trigger is an electrical switch that sends a signal when the shaft rotates past a predetermined location. In addition, the time between activation of the rotational trigger is also measured. During the rotation, noise level is measured with a noise measuring device209. The rotational position of the first blade201is determined by correlating a rotational position over time between signals from the rotational trigger. By “correlating”, it is meant that the time for a single rotation is measured and compared or plotted against the noise level magnitudes for this same period of time. Correlating the noise level measured by the noise measuring device includes normalizing the time between two trigger signals to 0° to 360° degree (rounded) to reduce or eliminate the dependency of rotor speed. Such correlation permits the identification and magnitude of the noise levels for the particular blades108(see e.g.,FIG. 5). For example, inFIG. 2, the first blade201or reference blade, is in the zero degree position, wherein the rotational trigger is activated. As the blades108rotate in direction207, the time required for the first blade201to rotate and return to the zero degree position is measured by measuring the time between signals from the rotational trigger.

FIG. 3shows the first blade201in a rotated position, wherein the first blade201has rotated in a direction207toward the noise-measuring device209. A noise level at or near a maximum noise level may be measured at noise measuring device209when first blade201is in the position shown inFIG. 4. As the blades108rotate, the noise measuring device209obtains continuous measurements of levels of noise detected from the blades108of the wind turbine100. As can be seen inFIG. 5, several maximums in noise level may occur, the maximums being associated with each of the blades108.

FIG. 5shows an example of the noise level measured at the noise-measuring device209during the rotation of the blades108. The graph illustrates noise level in decibels, but any other sound pressure level units may be utilized. As shown in the graph, the noise level is shown with respect to position in radial degrees. As the first blade201passes a zero degree mark (i.e., vertically oriented above the hub110), the rotational trigger is activated and signal corresponding to the position of the first blade201is recorded. While, the rotational trigger is illustrated as a signal corresponding to the zero degree position, the rotational trigger may be activated at any suitable position or at multiple positions. As the first blade201rotates, the position of the first blade201is determined by measuring noise level at the noise-measuring device209continuously over time until the rotational trigger is activated again, marking the completion of the rotation of the first blade201. The rotational positioning over time is correlated to the noise level measured at the noise-measuring device209and the magnitudes are shown inFIG. 5over an entire single rotation. The data for the single rotations may be stored for later analysis or may be utilized to aggregate data for multiple rotations. As can be seen inFIG. 5, peaks appear in the noise levels between the activation of the trigger. As the first blade201activates the rotational trigger, the second blade203is in a position wherein the noise level produced by the second blade203is near a maximum (e.g., about 120° of rotation). This is shown as the first peak501. Likewise, second peak503corresponds to the first blade201and the third peak505corresponds to the third blade205.

As the individual blade108noise level measurements are determinable by the noise-measuring device209correlated to blade position between rotational trigger activations, these magnitudes may be compared to determine the blade108and the blade configuration that is creating, for example, the greatest amount of noise.

FIG. 6illustrates a method for configuring a wind turbine100for a desired noise level according to an embodiment of the present disclosure. The method includes measuring sound pressure level or noise level with noise measuring device209during wind turbine100operation. A wind turbine100is configured with blades108having few or no aerodynamic modification devices (i.e., bare blades), step601. Noise level is measured as a function of power, rpm and/or pitch of the blades108, step603. As discussed more fully above, the noise level of the individual blades108is measured by recording the rotational position using time between activation of the rotational trigger with respect to the noise level measured at the noise measuring device209and observing the absolute peaks of the noise level measured. The noise level is then averaged using suitable averaging calculations against stable operating conditions to determine the absolute noise level and optimum noise levels for the individual blades, step605. The data obtained is compared for each blade with respect to each other, step607. The data is analyzed to determine the stability of the data and to determine whether the stability is sufficient to determine the absolute noise level desired by the individual blades108, step609. While not so limited, stable data may include a predetermined minimum number of data values per blade and wind bin, distributed over a turbine operational range. For example, each wind bin (e.g., 5.5 to 6.5 m/s) may be filled with at least 36 valid and undisturbed data points. If there is not sufficient stable data, steps603-609, the process is repeated with measuring the noise of the individual blades108at step603. If sufficient stable data exists, then a blade108is selected as a reference blade, step611. While not so limited, the reference blade may be selected as the blade having the least value for noise level.

At least one of the blades108, preferably two, are removed from the wind turbine and outfitted with noise reduction devices, step613. Noise reduction devices may include, but are not limited to aerodynamic modification devices. Aerodynamic modification devices may be arranged and disposed on the blades108. In other embodiments, blades108configured with differing aerodynamic profiles (e.g., varied airfoil geometries) may also be substituted for the blades108to determine the noise generated. The aerodynamic modification devices may include, but are not limited to turbulator holes, zig-zag (ZZ) turbulator tape, stall strips, vortex generators, Gurney flaps, acoustical flaps, any combinations thereof, or any other device or configuration capable of manipulating the aeorodynamic flow over the blade108. The arrangement of noise reduction devices selected may be based on any criteria. For example, the arrangement may be a random arrangement, a preselected arrangement or an arrangement in response to historical data of configurations for a particular wind turbine or environment. Noise level is measured as a function of power, rpm and/or pitch of the blades108, step615. The noise level is then averaged against stable operating conditions to determine the absolute noise level and optimum noise levels for the individual blades, step615. The data obtained in compared for each blade with respect to each other, step615. The data is analyzed to determine the stability of the data and to determine whether the stability is sufficient to determine the absolute noise level desired by the individual blades108, step615. Thereafter, a determination is made whether all of the desired combinations of configurations of blades has been measured, step617. If the combinations are insufficient, the blades108are reconfigured and the measurements are continued in step615. However, if all of the combinations have been measured and recorded, the noise levels desired are determined and the configuration associated with the desired noise level is determined, step619. While not so limited, the desired noise levels may be a minimum amount of noise, may be a noise level established by local ordinance or statute, or may be an optimal noise level with respect to cost or turbine efficiency. The blades108are provided with the configuration associated with the desired noise level and the wind turbine is permitted to operate, step621.

In order to determine the optimal configurations of noise reduction devices, the present method of measuring noise level permits the analyzing of many different wind turbine parameters, including, but not limited to wind speed, turbine output, rpm, pitch of the blades108or a variety of other wind turbine parameters. For example,FIG. 7shows noise levels with upwind measurements (LUV) over a period of time with respect to wind speed. Utilizing the data obtained at the noise measuring device209, the optimum or desired configuration of blade108may be obtained with respect to a variety of wind speeds. Additional data manipulation may also be provided, wherein comparisons with respect to any of the wind turbine parameters may be accomplished in order to determine the desired or optimum configuration for noise levels generated by the wind turbine100.