DOI: 10.13020/1etn-1q17
title: Rich Data for Wind Turbine Power Performance Analysis 

description: As the trend towards larger wind turbines continues, there is a growing need to refine and update the methods used for evaluating their performance. Variation in the input conditions over the vertical extent of the rotor leads to considerable uncertainty in the results of performance tests which appears as unwanted dispersion in the traditional power curve scatterplot. Measures to reduce this dispersion would therefore be beneficial. This project examines the effects traditional filtering criteria. It finds that these filters reject data from the centre of the distribution rather than the periphery, and therefore lead to a relative increase in data dispersion. Alternative criteria based on stationarity, intermittency, isotropy and normality show similar effects to those using turbulence intensity and shear, but do not lead to any significant improvement. A high-dimensional dataset representing over 700 factors is prepared and progressively narrowed through correlation analysis and global sensitivity analysis. The eFAST method is applied to an artificial neural network trained with quality-controlled time series data. The eFAST method represents input parameters as synthetic periodic signals so that their relative influence can be determined by applying a Fourier transform to the model output. The sensitivity of the model to a factor is reflected in the amplitude of its corresponding spectral peak. The main contribution of this work is the identification through this process of 16 meteorological factors shown to have an influence on power production. They include previously-known factors as well as others related to turbulence and atmospheric stability. A limitation of the approach is that identifying pairwise interactions it not possible. This is a major limitation of this project, and is recommended as a topic for future research.
description: The post-installation verification of wind turbine performance is an essential part of a wind energy project. Data collected from meteorological instruments and from the turbine is analysed to produce an estimate of the annual energy production (AEP) which is compared against expectations. However, turbine warranties can impose very strict data filtering criteria which can lead to high rates of data loss. As a consequence, measurement campaigns may last longer than expected and incur additional costs for the development.
This project aims to investigate the extent of the problem and the potential of alternative data filtering strategies with respect to data loss, AEP estimates and the dispersion of points in the power curve scatter plot. In doing so, it targets a wide range of meteorological parameters with theoretical relationships to wind turbine power production with particular interest in those not accounted for in the current standard. The identification of viable filtering strategies with lower data loss would provide significant benefits to wind energy development projects in terms of greater control over timescales and reduced costs.
Data from a sample of power performance tests is analysed to explore the range and severity of the problem of data loss. It confirms the wide variation in warranty conditions, demonstrates the extent and likelihood of data losses and quantifies the financial implications within the limits of commercial sensitivity. When indirect costs are taken into consideration, the impact of extended measurement campaigns can theoretically reach tens of millions of pounds.
A new, high-fidelity dataset is then compiled so that the effects of alternative filtering strategies can be examined. The dataset covers the whole of 2017 and consists of over 700 parameters of which 74 are selected for investigation here. The eFAST method of global sensitivity analysis is used in combination with correlation analysis to reduce this number to 11 parameters which are then used to define alternative filtering criteria.
Similar AEP estimates are obtained by application of conventional and experimental criteria to the research dataset. In the case of the experimental filters, however, the data loss was 11% compared to 63% data loss with conventional filters. Conventional filters were also shown to increase the dispersion in the power curve scatter plot by over 10%, while dispersion did not increase significantly with the experimental filters.
description: This dataset was created in order to support comparative analyses concerning the relationships between meteorological parameters and wind turbine power output. It addresses some of the limitations of existing datasets such as those compiled for commercial power performance testing (PPT) according to the international standard (IEC, 2017) and those created by micrometeorological research projects. In particular, it includes
•	A wide range of statistical measures for the base parameters
•	Alternative measures of wind shear, wind veer and turbulence
•	Multiple indicators of atmospheric stability
•	Estimates of vertical kinematic fluxes of sensible heat and horizontal momentum
•	Solar geometric parameters
The dataset is in tab-delimited format and comprises ten-minute average (TMA) records for the calendar year 2017. Meteorological and turbine SCADA data comes from the Eolos Wind Research Station operated by the University of Minnesota (http://eolos.umn.edu/facilities/eolos-wind-research-station)  and is primarily based on the measurements taken by sonic anemometers. The installation includes a 2.5 MW Clipper Liberty turbine with an associated 130 m met mast which spans the entire vertical diameter of the turbine rotor. Figure 1 illustrates the main turbine geometry and the disposition of the sonic instruments. 
The flux calculations rely on the rotation of the coordinate frame which requires knowledge of the local horizontal gradients of pressure and temperature. These are provided by the Automated Surface Observing Systems (ASOS) network of meteorological measurement stations maintained by US government agencies (http://mesonet.agron.iastate.edu/ASOS). Solar parameters are calculated based on local sunrise and sunset times from timeanddate.com (https://www.timeanddate.com/sun/usa/minneapolis).

Limitations of the dataset include:
•	Incomplete coverage of SCADA parameters
•	Wind speed and direction are based solely on sonic measurements
•	Flux calculations use a ten-minute averaging period rather than the standard 30 minutes
•	Significant turbine curtailment, especially early in the year
•	Instrument problems concerning the anemometer at the rotor top-tip height
The dataset was compiled as part of the author’s PhD at Edinburgh Napier University (www.napier.ac.uk/) using bespoke Python code. Documentation regarding the interpretation of the columns in the file is provided in the form of an csv spreadsheet. For further details please contact the author by email at b.davison@napier.ac.uk.