LiDAR-based turbine performance verification

Case study: Static Yaw Misalignment Influenced by Wind Speed Intensity.

Campaign details
Alt Objective:
Assess the performance of a turbine using a 4-beam LiDAR
Alt Wind turbine:
Enercon E82
2.3MW
Rotor 82m
Alt Commissioning year:
2013
Alt Campaign duration:
37 days
Alt Campaign outcome:
YM depends on wind speed ranges, high TI in SE sector, slightly overestimation of SCADA PC, rated power not reached
Campaign objectives

1) Yaw misalignment (YM) detection

2) Quick turbulence intensity (TI) profile

3) Quick power curve (PC) verification

Key benefits of a LiDAR-based performance verification:

Measurement principle and set-up

A 4-beam LiDAR is temporarily mounted on top of the nacelle, together with a number of calibrated instruments, and a data collection and communication unit in the nacelle. Every second, the LiDAR measures the horizontal wind speed and directionat hub height in front of the turbine at 10 simulatenous measurement ranges, between 50m to 400m. Compared to met mast-mounted cup anemometers, sufficient data to evaluate the wind turbine power performance can be collected much faster by the nacelle-based LiDAR.

Yaw misalignment

The average relative wind direction and wind speed (at hub height) are computed every 10 minutes from several measurement ranges in front of the turbine. These measurements are validated or discarded based on standard or more advanced criteria, such as cut-in & rated wind speed, low data quality, etc.

Results:

Conclusion:

Wind speed [m/s]
2.5-5.0
5.0-7.5
7.5-10.0
10.0-12.5
12.5-14.0*
14.0-25.0
Yaw error [°]
-0.88
2.26
2.08
6.19
6.41
3.96
Data points [#]
903
1137
673
375
131
139
Tab. 1: Yaw error per wind speed
Alt
Fig. 1: Wind speed vs. Yaw error
Turbulence intensity and wake effect

Turbulence intensity results are based on wind reconstructions calculated at a distance closest to 2.5 times the diameter of the rotor, which in this case is 200m. The blocked sectors are calculated according to the requirements from IEC 61400-12-1 2017, Annex A.

Alt
Fig. 2: TI at 200m
Alt
Fig. 3: Farm layout
Alt
Fig. 4: Wind rose

Results:

Conclusion:

Alt
Fig. 5: Relative wind direction
Power curve

Turbulence intensity results are based on wind reconstructions calculated at a distance closest to 2.5 times the diameter of the rotor, which in this case is 200m. The blocked sectors are calculated according to the requirements from IEC 61400-12-1 2017, Annex A.

Results:

Conclusion:

Alt
Fig. 6: Power curve
Alt
Fig. 7: Wind speed comparison