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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Sarah Barber Fraunhofer IWES, Germany
Co-authors:
Sarah Barber (1) F Sebastian Mechler (1) Oliver Maas (1)
(1) Fraunhofer IWES, Bremerhaven, Germany

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Sarah Barber has been Group Manager of the Application Center for Wind Energy Field Measurements at Fraunhofer IWES since April 2014. She studied mechanical engineering with aerodynamics at Cambridge University (UK) and MIT (USA), followed by a PhD in the field of applied aerodynamics. She has been working in wind energy since 2007, building up a research group in the area of wind turbine wake measurements as postdoc and lecturer at ETH Zurich (Switzerland), undertaking wind resource assessments at an electricity company and leading the development department of the Swiss Start-up Agile Wind Power AG as Chief Technology Officer in 2012.


Poster

Poster Download poster (7.87 MB)

Abstract

Assessment of the added value of two alternative approaches for obtaining wind conditions for mechanical load measurement campaigns

Introduction

Characteristic mechanical loads of the main components of a wind turbine are generally measured in the field according to the technical specification IEC 61400-13 for a range of applications including certification of prototype wind turbines, validation of numerical models, assessment of the effect of new mechanical components and evaluation of effects of neighbouring wind turbines. For these measurements, these loads are usually measured with strain gauges attached to the blade root, on the main shaft and at several locations on the tower. Additionally, several operational parameters as well as wind conditions are measured. The results are analysed for valid wind directions according to wind speed and turbulence intensity bins. For this analysis, the wind velocity and direction must be obtained with a cup anemometer and wind vane mounted on a met mast at hub height according to IEC 61400-12.

The installation of a met mast for this purpose increases the cost and complexity of a measurement campaign enormously and can be severely detrimental to the success of a project. Therefore alternative approaches may improve the overall effectiveness and success of a project significantly. Two alternative approaches for obtaining wind conditions for real applications of mechanical load measurements are considered and assessed in this work. The total added value of these approaches is assessed in terms of the measurement results, measurement quality, measurement uncertainty, project quality and project costs.


Approach

The first approach is using a LiDAR instead of a met mast to measure the wind velocity and direction and the second approach is using SCADA data from neighbouring wind turbines. Assessements of these approaches are discussed in the next section.

Main body of abstract

The LiDAR approach has the advantage of lower costs and installation effort as well as the possibility of measuring the wind shear across the entire rotor diameter additionally. The main disadvantage is that the turbulence intensity cannot be accurately obtained. In this work, this approach is assessed for a measurement campaign in which the effects of neighbouring wind turbines on the fatigue damage of a measured 1.65-MW wind turbine are evaluated. The damage equivalent loads are calculated for wake as well as non-wake operation and the results are weighted for frequency in order to quantify the effect of the neighbouring wind turbines on the fatigue damage. Damage equivalent loads are then calculated separately for a range of shear and turbulence intensity conditions using wind data based on met mast and based on LiDAR measurements. Comparisons are made in order to assess the quality and accuracy of the calculated fatigue damage.

The SCADE approach has the advantage of being extremely low-cost and having zero installation effort; however the disadvantage of not enabling high-quality real inflow conditions to be obtained. In this work, this approach is assessed for a measurement campaign in which the effects of a mechanical change to the blades on the mechanical loads and dynamic properties of a 1.5-MW wind turbine are evaluated. As well as measuring the mechanical loads before and after the mechanical change to the blades, wind velocity, wind direction and power measurements are taken from the SCADA data of the modified wind turbine and of a neighbouring wind turbine. Power curves are calculated for both wind turbines and the results used as a basis for establishing equivalent wind conditions. Comparisons are made in order to assess the quality and accuracy of the calculated fatigue damage.


Conclusion

The advantages of two different approaches using LiDAR measurements and SCADA data as an alternative to met mast measurements have been assessed and quantified for two separate measurement campaigns. It has been shown that both of these methods have the potential to increase the overall quality and effectiveness of field measurement campaigns.


Learning objectives
To understand two alternative approaches for increasing the overall effectiveness of mechanical load measurement campaigns of wind turbines by applying alternative approaches to the installation of a met mast for obtaining the required wind data.