Measurement of rotor centre flow direction and turbulence in wind farm environment

Pedersen, Troels; Demurtas, Giorgio; Sommer, Anders; Højstrup, Jørgen

doi:10.1088/1742-6596/524/1/012167

Cited by 7 publications

(8 citation statements)

References 3 publications

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“…The authors (Mamidipudi et al, 2011;Fleming et al, 2014;Scholbrock et al, 2015;Brown and Oldroyd, 2015) propose using an upwind-looking nacelle-mounted lidar. Pedersen et al (2008Pedersen et al ( , 2014Pedersen et al ( , 2015 and Demurtas et al (2016) present a method to measure the free wind speed, direction and turbulence intensity with three rotating sonic anemometers on the spinner nose. Bottasso and Riboldi (2014) estimate yaw misalignment and vertical shear from cyclic blade loads.…”

Section: Introductionmentioning

confidence: 99%

Determination of optimal wind turbine alignment into the wind and detection of alignment changes with SCADA data

Mittelmeier

Kühn

2018

Wind Energ. Sci.

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Abstract. Upwind horizontal axis wind turbines need to be aligned with the main wind direction to maximize energy yield. Attempts have been made to improve the yaw alignment with advanced measurement equipment but most of these techniques introduce additional costs and rely on alignment tolerances with the rotor axis or the true north.Turbines that are well aligned after commissioning may suffer an alignment degradation during their operational lifetime. Such changes need to be detected as soon as possible to minimize power losses. The objective of this paper is to propose a three-step methodology to improve turbine alignment and detect changes during operational lifetime with standard nacelle metrology (met) mast instruments (here: two cup anemometer and one wind vane).In step one, a reference turbine and an external undisturbed reference wind signal, e.g., met mast or lidar are used to determine flow corrections for the nacelle wind direction instruments to obtain a turbine alignment with optimal power production. Secondly a nacelle wind speed correction enables the application of the previous step without additional external measurement equipment.Step three is a monitoring application and allows the detection of alignment changes on the wind direction measurement device by means of a flow equilibrium between the two anemometers behind the rotor.The three steps are demonstrated at two 2 MW turbines together with a ground-based lidar. A first-order multilinear regression model gives sufficient correction of the flow distortion behind the rotor for our purposes and two wind vane alignment changes are detected with an accuracy of ±1.4 • within 3 days of operation after the change is introduced.We show that standard turbine equipment is able to align a turbine with sufficient accuracy and changes to its alignment can be detected in a reasonably short time, which helps to minimize power losses.

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Section: Introductionmentioning

confidence: 99%

Determination of optimal wind turbine alignment into the wind and detection of alignment changes with SCADA data

Mittelmeier

Kühn

2018

Wind Energ. Sci.

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“…This condition of negligible induction was not reached by our stall‐regulated wind turbine, for the available measurements (up to U m m =19 ms −1 ). A modern pitch‐regulated turbine however might have a negligible induction at lower wind speeds than a stall‐regulated turbine, as experienced in the literature .…”

Section: Discussionmentioning

confidence: 97%

“…This flow distortion is normally corrected for in the wind turbine control system. However, corrections in the controller might not take all situations into account, for example, when the wake swirl from upstream wind turbines introduces upwards and downwards flow on the nacelle . Such corrections are not required for a spinner anemometer, which is not affected by blade wakes since it measures the wind upstream of the rotor (Figure ).…”

Section: Introductionmentioning

confidence: 99%

Calibration of a spinner anemometer for wind speed measurements

2016

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The power curve of a wind turbine can be measured, according to IEC 61400-12-2 with a nacelle mounted anemometer. Typically, a sonic anemometer or a cup anemometer and a wind vane are mounted on the back of the nacelle roof. Another option to measure the wind experienced by the wind turbine is to use a spinner anemometer. The measurement principle of the spinner anemometer is based on the flow distortion caused by the wind turbine spinner. The flow on the spinner surface is measured by means of three 1D sonic sensors mounted on the spinner and a conversion algorithm to convert the wind velocity components measured by the three sonic sensors to: horizontal wind speed, yaw misalignment and flow inclination angle. The algorithm utilizes two calibration constants that are specific to the spinner shape, blade root design and to the mounting positions of the sonic sensors on the spinner. The present analysis describes methods to determine the calibration constant related to wind speed measurements. The first and preferred method is based on the definition of the calibration constant and uses wind speed measurements during the stopped condition of the wind turbine. In addition to this preferred method, two alternative methods that did not require the turbine to be stopped were investigated: one used relatively high wind speed measurements during normal operation of the wind turbine, while the other one used a CFD simulation of the flow over the spinner. The method that entails stopping the turbine in good wind conditions showed the best results and is recommended for the stall regulated wind turbine we have tested. The evaluation of uncertainty was not included in the present analysis.

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“…The measurement of the flow inclination angle by the spinner anemometer might in this case be very helpful as an additional parameter for correction or normalization of the power curve. The spinner anemometer might be well suited to measure in the wake of other wind turbines as turbulence and large flow inclination angles can be measured with reasonably good accuracy (Pedersen et al, 2014). However, it has to be kept in mind that the spinner anemometer is a point measurement, compared to the rotor swept area.…”

Section: Discussionmentioning

confidence: 99%

“…15 shows that the u U is basically only a function of U . A typical average inflow angle to a wind turbine is smaller than 5 • , as presented in Pedersen et al (2014). The uncertainty in the wind speed is typically a function of the wind speed only.…”

Section: Combination Of Uncertainties Through the Spinner Anemometer mentioning

confidence: 99%

Nacelle power curve measurement with spinner anemometer and uncertainty evaluation

2017

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Abstract. The objective of this investigation was to verify the feasibility of using the spinner anemometer calibration and nacelle transfer function determined on one reference wind turbine, in order to assess the power performance of a second identical turbine. An experiment was set up with a met mast in a position suitable to measure the power curve of the two wind turbines, both equipped with a spinner anemometer. An IEC 61400-12-1-compliant power curve was then measured for both wind turbines using the met mast. The NTF (nacelle transfer function) was measured on the reference wind turbine and then applied to both turbines to calculate the free wind speed. For each of the two wind turbines, the power curve (PC) was measured with the met mast and the nacelle power curve (NPC) with the spinner anemometer. Four power curves (two PCs and two NPCs) were compared in terms of AEP (annual energy production) for a Rayleigh wind speed probability distribution. For each wind turbine, the NPC agreed with the corresponding PC within 0.10 % of AEP for the reference wind turbine and within 0.38 % for the second wind turbine, for a mean wind speed of 8 m s −1 .

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Measurement of rotor centre flow direction and turbulence in wind farm environment

Cited by 7 publications

References 3 publications

Determination of optimal wind turbine alignment into the wind and detection of alignment changes with SCADA data

Determination of optimal wind turbine alignment into the wind and detection of alignment changes with SCADA data

Calibration of a spinner anemometer for wind speed measurements

Nacelle power curve measurement with spinner anemometer and uncertainty evaluation

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