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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Real world power curves: A new era for wind resource assessments?' taking place on Tuesday, 11 March 2014 at 14:15-15:45. The meet-the-authors will take place in the poster area.

Jørgen Højstrup ROMO Wind, Denmark
Co-authors:
Jørgen Højstrup (1) F P
(1) ROMO Wind, Aarhus N, Denmark (2) Højstrup Wind Energy, Aarhus, Denmark

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Abstract

Power curve verification with the spinner anemometer

Introduction

Traditional power curve verification according to IEC 61400-12-1 is time consuming and expensive, and in complex terrain only possible if you made a site calibration before you installed the turbine. You can also use the nacelle anemometer according to IEC 61400-12-2 instead, which in principle is easier and less expensive, but the crucial difficulty is the requirement for “site-similar” verification of the transfer function from the free wind to the nacelle wind measurement.

Approach

The Spinner Anemometer presents an alternative method for power curve verification which at the same time is simpler and less expensive, and makes the need for site calibration obsolete because of the positioning of the measurement in front of the turbine on the spinner in combination with an instrument with an angular response much better than any mast mounted anemometer. The spinner anemometer can be used for wind speed measurements according to IEC 61400-12-2.

Main body of abstract

The patented Spinner Anemometer which has been used now for a couple of years to directly measure yaw misalignment on wind turbines. This misalignment can then subsequently be corrected to achieve a higher production from the wind turbine. Since the Spinner Anemometer is measuring the complete wind vector (i.e. speed, direction and deviation from horizontal flow), it is obvious to also use it for power curve verification. In order to do this it is of course necessary to document that the wind speed measurements can be performed with sufficiently high accuracy with the Spinner Anemometer. A number of field tests have been done to show that this is actually the case. We have earlier demonstrated that power curve improvements can be measured with high accuracy, and now we have also documented the use of the Spinner Anemometer for absolute power curve measurements. The Spinner Anemometer needs to be calibrated for each type of wind turbine (not for each individual turbine). We show methods for this calibration of the Spinner Anemometer (using nacelle mounted Lidar or a mast measurement if available), derivation of uncertainty estimates, and we show results from power curve measurements in different types of terrain, directly compared with traditional IEC power curves. An important part of the process has been to show that site calibration or site specific transfer functions are not needed for the Spinner Anemometer.

Conclusion

The spinner anemometer is well suited for power curve verification. The resulting uncertainty of the power curves is comparable to a mast based IEC measurement. There is no need for site calibration, which means that the power curve verification can be performed for any turbine in a wind farm, in any type of terrain. The power curve verification with the spinner anemometer is less expensive and less time consuming than the traditional method.


Learning objectives
The power curve measurement suitability of the Spinner Anemometer has now been documented. We have shown that the Spinner Anemometer is an excellent alternative to the expensive and time consuming process of the erection of tall masts for site calibration and subsequent power curve measurements. With the Spinner Anemometer you can check the power performance of any (or all) of your turbines at any time, and additionally optimize their energy output.