Knowledge centre

Spinner anemometry

Wind measurements at the nacelle are conventionally performed using cup anemometry, wind vanes or ultrasonic sensors. This devices have the disadvantage to be disturbed by the rotor and nacelle itself, which can result in data different from the actual wind affecting the turbine. Spinner anemometry does measure the wind where it hits the rotor first. By using the flow over the spinner surface in conjunction with the rotor azimuth it is possible to measure almost undisturbed wind speed, relative wind direction and flow inclination at any time during operation.

Measuring wind quantities directly at the rotor offers possibilities conventional nacelle measurement equipment does not have. Beside horizontal wind speed measurement yaw misalignment and flow inclination can be directly derived. Additionally turbulence intensity as well as wind shear can be extracted. Together with air temperature and air pressure data each individual turbine can be enhanced to be virtual met mast.

We are permanently working to achieve more and better insights in this topic. If you are interested in a combined project for further validation, we look forward to hear from you. We also invite you to start a dialogue and to contribute your questions and experiences, to broaden your and our horizon.

Pdf Icon Introducing the spinner anemometer iSpin

videoWebinar: Increase AEP by 2% With Improved Wind Measurement

Pdf Icon iSpin sensor datasheet

Pdf Icon DNV GL: Review of the spinner anemometer iSpin from ROMO Wind (report)

Pdf Icon GL Garrad Hassan: Technology review of the ROMO Wind spinner anemometer (report)

Pdf Icon Spinner anemometry – an innovative wind measurement concept, by Risø National Laboratory (scientific paper)

Pdf Icon Aerodynamics and Characteristics of a Spinner Anemometer, by T. F. Pedersen, N. Sørensen and P. Enevoldsen (scientific paper)

Pdf Icon Calibration of a spinner anemometer for yaw misalignment (scientific paper)

Yaw misalignment

Yaw misalignment describes the deviation between the wind direction and the direction the nacelle is pointing to. Because the wind direction is constantly changing, a turbine cannot always point correctly into the wind. However, on average the yaw misalignment should always be close to zero degrees in order to fully extract the wind energy as well as be subjected to minimal loads.

Detecting and decreasing yaw misalignment can help to reduce production losses as well as to reduce loads. When referring to yaw misalignment it can be distinguished between the average yaw misalignment, called “static yaw misalignment”, and the variation around the “static yaw misalignment”, called “dynamic yaw misalignment”. Whereas static yaw misalignment can be corrected by changing yaw offset values, dynamic yaw misalignment is depending on the yaw control algorithm. Using spinner anemometry helps to detect and correct static yaw misalignment as well as identifying optimization potential for the turbine yaw control.

We are permanently working to achieve more and better insights in this topic. If you are interested in a combined project for further validation, we look forward to hear from you. We also invite you to start a dialogue and to contribute your questions and experiences, to broaden your and our horizon.

Click here to get more and detailed insides on Yaw misalignment distribution in several wind turbine types

Pdf Icon GL Garrad Hassan: Yaw misalignments and loads (report)

Pdf Icon Calibration of a spinner anemometer for yaw misalignment (scientific paper) 

Flow inclination

Flow inclination describes the angle between the horizontal plane and the direction of wind hitting the turbine. Coming from below, e.g. up-hill it is considered to be a positive, from down-hill to be negative angle. Flow inclination angles are related to the position of the wind turbine, the tilt angle and the RIX factor or slopes of nearby ground. The inclination angles can be measured by spinner anemometry due to its position on the hub. The influence in energy production has the same importance than yaw misalignment.

Besides comparing existing site evaluation reports with measured wind data, flow inclination data in connection with nacelle direction data could be used to perform sector wise power curve and load evaluations.

We are permanently working to achieve more and better insights in this topic. If you are interested in a combined project for further validation, we look forward to hear from you. We also invite you to start a dialogue and to contribute your questions and experiences, to broaden your and our horizon.

Pdf Icon Measurement of rotor centre flow direction and turbulence in wind farm environment (scientific paper)

Turbulence intensity

Turbulence intensity quantifies how much the wind varies typically within a given average time, which is normally 10 minute. Because the fatigue loads of a number of major components in a wind turbine are mainly caused by turbulence, the knowledge of site specific turbulence characteristic is of crucial importance. Normally the wind speed increases with increasing height. In flat terrain the wind speed increases logarithmically with height. In complex terrain the wind profile is not a simple increase and additionally a separation of the flow might occur, leading to heavily increased turbulence.

Measuring the turbulence intensity directly at the turbine rotor offers a variety of applications. Besides comparing existing site evaluation reports with measured wind data, turbulence intensity information in connection with nacelle direction data could be used to perform sector wise power curve and load evaluations. Another possibility could be the usage of sector wise turbulence intensity information for advanced turbine control.

We are permanently working to achieve more and better insights in this topic. If you are interested in a combined project for further validation, we look forward to hear from you. We also invite you to start a dialogue and to contribute your questions and experiences, to broaden your and our horizon.

Pdf Icon Measurement of rotor centre flow direction and turbulence in wind farm environment (scientific paper)

 

Performance monitoring

The performance of wind turbines is defined as power versus wind speed taking into account additional constraints like turbulence intensity, wind shear, slope and air density. Whereas the power output at a turbine can be measured precisely, the actual wind as input quantity for the turbine is difficult to meter. Commonly nacelle transfer functions (NTFs) which describe the relationship between met mast and conventional nacelle anemometry measurements are used to correct the nacelle anemometer output. These NTFs are normally established under free flow conditions and can lead to inaccurate wind speed results when it comes to application at actual sites.

With spinner anemometry wind quantities, like wind speed, turbulence intensity, inflow angles or wind shear can be measured. Due to its unique position at the spinner the nacelle transfer function (NTF) is considered to be much more robust compared to those of conventional nacelle anemometry. Together with air density derived from air pressure and air temperature measurements for the first time precise relative power curve measurements at the turbines can be performed. Besides verifying yaw misalignment correction improvements the relative power curve measurement can also be used to verify other production relevant improvement measures, like e.g. Vortex generators or further blade modifications. Especially for those improvement measures which do affect the nacelle transfer function (NTF) for the conventional nacelle anemometry the relative power curve measurement using iSpin can provide much more objective and transparent results to the client.

We are permanently working to achieve more and better insights in this topic. If you are interested in a combined project for further validation, we look forward to hear from you. We also invite you to start a dialogue and to contribute your questions and experiences, to broaden your and our horizon.

 

Open Data

ROMO Wind and Vattenfall hereby offer you the opportunity to analyse and evaluate, in detail, the results of a comprehensive performance measurement project. Supported by the Danish EUDP program, the project was conducted from 1 November 2014 to 17 December 2015 in the Nørrekær Enge wind farm in Northern Denmark together with the wind farm owner, Vattenfall and DTU Wind Energy. It comprised a direct comparison between different wind turbine nacelle based wind measurement instruments as well as a correlation to an IEC certified met mast raised in front of one of the turbines in the wind farm. Data, collected from the met-mast, a nacelle lidar, the nacelle anemometer and the iSpin spinner anemometer was combined with power measurement and relevant meteorological data. In addition, iSpin power curves and other wind measurements were also recorded from all other wind turbines in the wind farm.

The entire wind farm performance data set is now available for free to European and US parties in return for signing a data sharing agreement. In exchange for the data set, the data receiver will simply agree to analyse the data and provide written feedback to Vattenfall and ROMO Wind within a pre-agreed timeframe and not to distribute to other parties.

The Nørrekær Enge wind farm, commissioned in 2009, consists of 13 Siemens SWT 2.3-93 wind turbines at 80 m hub height. The layout of the park is shown below together with the IEC compliant met mast:

Two complete data packages are available

Two complete data packages are available:

1. A data package from 1 November 2014 to 21 January 2015 for turbine no.4. During this period, data is available from the turbine nacelle anemometer SCADA data, from a WindIris nacelle lidar (placed on the nacelle roof), from the met-mast and from iSpin also including power measurement data as well as air density, air pressure and nacelle position.

2. A data package from 24 September 2015 to 17 December 2015 containing iSpin and power measurement data for all 13 turbines as well as the met-mast data. Included within the data packages is a description of the various signals, wind tunnel calibration certificates, photos of the iSpin sensor installations, videos and other information useful for the verification of the data.

In summary ROMO Wind and Vattenfall when analysing the data reached the following conclusions:

• iSpin measured the power curve with approx. 30% less scatter than the nacelle lidar and the met-mast.

• When measuring the wind simultaneously in all wind sectors around all wind turbines, i.e. also in disturbed wind conditions such as in wake of other turbines, iSpin was still able to measure the power curves (see figure below) as well as yaw misalignment with high precision. This was done using the same calibration factors obtained from the reference turbine no.4, demonstrating that the factors are transferable to other turbines and stable even when the wind turbines are in the wake of other turbines.

When measuring the wind simultaneously

• When measuring the wind simultaneously in all wind sectors around all wind turbines, nacelle lidar provided a highly variable power curve as well as yaw misalignment results when in the wake of other turbines.

• When measuring the wind simultaneously in all wind sectors, eliminating one outlier wind turbine NKE01 and a turbine with yaw misalignment NKE13, the remaining eight wind turbine power curves varied only 0.3% in Annual Energy Production (95% confidence level); “7, 8 and 9 are always in de-rated noise mode and not considered for this result”. Consequently, iSpin can be used to monitor the performance of the entire wind farm with very high precision.

Lidar turbulence intensity measurements

• Lidar turbulence intensity measurements correlated poorly with the met-mast, whereas iSpin measurements correlated well.

If you are interested in receiving our data please fill out the below form and a member of our sales team will get back to you shortly enabling you to sign the data sharing agreement with Vattenfall and ROMO Wind.