Power curves - use of spinner anemometry Troels Friis Pedersen DTU Wind Energy Professor
Spinner anemometry using the airflow over the spinner to measure wind speed, yaw misalignment and flow inclination angle 2 Yaw error versus wind speed (all sonic sensors) 1 Yaw error (deg) 1-1 1 2 2 Spinner anemometer wind speed (m/s) Flow inclination angle versus wind speed (all sonic sensors) 2 Flow inclination angle (deg) 1 1 - -1-1 1 1 2 2 Spinner anemometer wind speed (m/s)
Spinner anemometry can be used on all types of spinners Semi-spherical Parabolic Pointed Flat (not experienced yet) 3
Why use of spinner anemometry? A spinner anemometer has the advantage of measurements being performed in front of the rotor without flow distortions disturbing the sensor Due to rotation a spinner anemometer measure flow angles without mounting and adjustment errors profiled blade induced flow Environmental parameters: other wind turbines terrain roughness terrain obstacles RIX number upsteam rotor induced flow Wind: turbulence yaw error flow inclination angle air density blade root vortex anemometer type and class aviation lights mounting height mounting structure swirl induced flow mounting position blade root wake safety railings nacelle induced flow control system software version control parameters operational mode - rpm & pitch 4
Measurements on Vestas V8 2MW (Horns Rev I type) Tjæreborg site Met mast at distance 1.D Cup and vane at hub height 6m
Calibration of two spinner anemometer constants k1 and k2 Calibration for angular measurements kα = k2/k1 Spinner anemometer yaw misalignment (deg) Yaw misalignment calibration 1 8 6 4 y = -1,227x + 247, 2-2 -4-6 -8-1 14 16 18 2 22 24 26 28 3 32 34 Turbine yaw direction (deg) Yaw direction (deg) 34 32 3 28 26 24 22 2 18 16 14 Calibration for yaw misalignment measurement "Nacelle direction" Yaw misalignment SA Time (sec) 6
Calibration of k1 constant and extraction of induction function Determination of Nacelle Transfer Function (NTF IEC614-12-2) Induction: a = ( U U )/ U cup spin cup Spinner anemometer wind speed (m/s) 2 18 16 14 12 1 8 6 4 2 Mast versus spinner wind speed free wind sector Extracting induction function Induction (Cup-Spin)/Cup (m/s),24,22,2,18,16,14,12,1,8,6,4,2 Induction as function of spinner anem wind speed 2 4 6 8 1 12 14 16 18 2 Mast cup anemometer wind speed (m/s), 2 4 6 8 1 12 14 16 18 2 Mast cup wind speed (m/s) 7
Wind speed standard deviation of spinner anemometer is equal to that of the mast cup anemometer Turbulence is measured correctly by the spinner anemometer when the wind speed is corrected for the induction Spinner anemometer Ti Spinner versus mast Ti free wind sector,2,18,16,14,12 slope=1,11,1,8,6,4,2,,,2,4,6,8,1,12,14,16,18,2 Mast cup anemometer Ti Correction for induction Induction (Cup-Spin)/Cup (m/s) Induction as function of spinner anem wind speed,24,22,2,18,16,14,12,1,8,6,4,2, 2 4 6 8 1 12 14 16 18 2 Mast cup wind speed (m/s) Spinner anemometer Ti Spinner Ti corrected for induction,2,18,16,14,12 slope=1,,1,8,6,4,2,,,2,4,6,8,1,12,14,16,18,2 Mast cup anemometer Ti 8
Measurement of yaw misalignment and flow inclination angle 2 Yaw misalignment for all directions 2 Flow inclination angle for all directions 2 2 Yaw misalignment (deg) 1 1 - -1-1 Flow inclination angle (deg) 1 1 - -1-1 -2-2 -2 2 4 6 8 1 12 14 16 18 2 Free wind speed (m/s) -2 2 4 6 8 1 12 14 16 18 2 Free wind speed (m/s) 9
Spinner anemometry Measurement of yaw misalignment versus flow inclination angle from different sectors in wind farm, 3sec averages Yaw misalignment versus flow inclination angle high roughness, wake-free sector 2 2 2 2 1 1 Flow inclination angle (deg) Flow inclination angle (deg) Yaw misalignment versus flow inclination angle low roughness, wake-free sector 1 - -1-1 -2 - -1-1 -2-2 -2-1 -1 - Yaw misalignment (deg) 1 1 2 2-2 Yaw misalignment versus flow inclination angle in wake behind turbine 3,2D -2-1 -1 - Yaw misalignment (deg) 1 1 2 2 Wake swirl from upfront wind turbine 2 2 2 2 1 Flow inclination angle (deg) Flow inclination angle (deg) -2-2 1 - -1-1 -2 1 1 - -1-1 -2-2 -2 1 1-2 -1-1 - Yaw misalignment (deg) 1 1 2 2-2 17 18 18 19 19 2 2 Mast wind direction (deg) 21 21 22
Energy loss due to yaw misalignment Re. www.romowind.com Figures re. J.Højstrup 11
Measurement of nacelle power curve according to IEC614-12-2 (NPC) 2.4 Power versus wind speed 2.4 Power versus wind speed Electric power (kw) 2.2 2. 1.8 1.6 1.4 1.2 1. 8 6 4 2 Cup Spinner 2 4 6 8 1 12 14 16 18 2 Wind speed (m/s) Induction (Cup-Spin)/Cup (m/s) Correction for induction Induction as function of spinner anem wind speed,24,22,2,18,16,14,12,1,8,6,4,2, 2 4 6 8 1 12 14 16 18 2 Mast cup wind speed (m/s) Electric power (kw) 2.2 2. 1.8 1.6 1.4 1.2 1. 8 6 4 2 Cup Spinner 2 4 6 8 1 12 14 16 18 2 Free wind speed (m/s) 12
Measurement of rotor power curve (RPC) A normalized power curve for horizontal (or axial) flow wind speed: Corrected for induction Normalized for air density Normalized for yaw misalignment by cos^2 relation Normalized for flow inclination angle by cos^2 relation Could additionally be normalized for turbulence intensity Electric power (kw) 2.4 2.2 2. 1.8 1.6 1.4 1.2 1. 8 6 4 2 Power versus wind speed, dir normalized Cup Spinner 2 4 6 8 1 12 14 16 18 2 Wind speed (m/s) Induction correction and normalization Induction (Cup-Spin)/Cup (m/s) Induction as function of spinner anem wind speed,24,22,2,18,16,14,12,1,8,6,4,2, 2 4 6 8 1 12 14 16 18 2 Mast cup wind speed (m/s) Electric power (kw) 2.4 2.2 2. 1.8 1.6 1.4 1.2 1. 8 6 4 2 Power versus wind speed, dir normalized Cup Spinner 2 4 6 8 1 12 14 16 18 2 Free wind speed (m/s) 13
Measurement of rotor power curve (RPC) - Compared to IEC standard power curve Standard IEC power curves Rotor power curve 2.4 Power versus wind speed 2.4 Power versus wind speed, dir normalized 2.2 2.2 2. 2. 1.8 1.8 Electric power (kw) 1.6 1.4 1.2 1. 8 6 Cup Spinner Electric power (kw) 1.6 1.4 1.2 1. 8 6 Cup Spinner 4 4 2 2 2 4 6 8 1 12 14 16 18 2 Wind speed (m/s) 2 4 6 8 1 12 14 16 18 2 Wind speed (m/s) 14
Conclusions Spinner anemometer measures horizontal wind speed, yaw misalignment and flow inclination angle Calibration of angular measurements by yawing turbine in and out of the wind Calibration of wind speed measurements by measurements during operation and relating wind speed to met mast or lidar Calibration gives k1 and k2 spinner anemometer constants and induction function By correction for induction function the spinner anemometer measures turbulence intensity correctly By correction for induction the spinner anemometer measures power curves according to IEC614-12-2 (NPC) A proposed generic rotor power curve (RPC), corrected for induction, and normalized for air density, yaw misalignment and flow inclination angle reduces scatter and increase power curve 1