Seasonal effects in the long-term correction of short-term wind measurements using reanalysis data

<p>Measure–correlate–predict (MCP) approaches are often used to correct wind measurements to the long-term wind conditions on-site. This paper investigates systematic errors in MCP-based long-term corrections which occur if the measurement on-site covers only a few months (seasonal biases). In...

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Autores principales:	A. Basse, D. Callies, A. Grötzner, L. Pauscher
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Renewable energy sources TJ807-830
Acceso en línea:	https://doaj.org/article/bc7775ee1e2d4c98927c8d47be5b4fe8
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spelling	oai:doaj.org-article:bc7775ee1e2d4c98927c8d47be5b4fe82021-11-16T05:14:08ZSeasonal effects in the long-term correction of short-term wind measurements using reanalysis data10.5194/wes-6-1473-20212366-74432366-7451https://doaj.org/article/bc7775ee1e2d4c98927c8d47be5b4fe82021-11-01T00:00:00Zhttps://wes.copernicus.org/articles/6/1473/2021/wes-6-1473-2021.pdfhttps://doaj.org/toc/2366-7443https://doaj.org/toc/2366-7451<p>Measure–correlate–predict (MCP) approaches are often used to correct wind measurements to the long-term wind conditions on-site. This paper investigates systematic errors in MCP-based long-term corrections which occur if the measurement on-site covers only a few months (seasonal biases). In this context, two common linear MCP methods are tested and compared with regard to accuracy in mean, variance, and turbine energy production – namely, variance ratio (VR) and linear regression with residuals (LR). Wind measurement data from 18 sites with different terrain complexity in Germany are used (measurement heights between 100 and 140 m). Six different reanalysis data sets serve as the reference (long-term) wind data in the MCP calculations. All these reanalysis data sets showed an overpronounced annual course of wind speed (i.e., wind speeds too high in winter and too low in summer). However, despite the mathematical similarity of the two MCP methods, these errors in the data resulted in very different seasonal biases when either the VR or LR methods were used for the MCP calculations. In general, the VR method produced overestimations of the mean wind speed when measuring in summer and underestimations in the case of winter measurements. The LR method, in contrast, predominantly led to opposite results. An analysis of the bias in variance did not show such a clear seasonal variation. Overall, the variance error plays only a minor role for the accuracy in energy compared to the error in mean wind speed. Besides the experimental analysis, a theoretical framework is presented which explains these phenomena. This framework enables us to trace the seasonal biases to the mechanics of the methods and the properties of the reanalysis data sets. In summary, three aspects are identified as the main influential factors for the seasonal biases in mean wind speed: (1) the (dis-)similarity of the real wind conditions on-site in correlation and correction period (representativeness of the measurement period), (2) the capability of the reference data to reproduce the seasonal course of wind speed, and (3) the regression parameter <span class="inline-formula"><i>β</i><sub>1</sub></span> (slope) of the linear MCP method. This theoretical framework can also be considered valid for different measurement durations, other reference data sets, and other regions of the world.</p>A. BasseA. BasseD. CalliesD. CalliesA. GrötznerL. PauscherCopernicus PublicationsarticleRenewable energy sourcesTJ807-830ENWind Energy Science, Vol 6, Pp 1473-1490 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Renewable energy sources TJ807-830
spellingShingle	Renewable energy sources TJ807-830 A. Basse A. Basse D. Callies D. Callies A. Grötzner L. Pauscher Seasonal effects in the long-term correction of short-term wind measurements using reanalysis data
description	<p>Measure–correlate–predict (MCP) approaches are often used to correct wind measurements to the long-term wind conditions on-site. This paper investigates systematic errors in MCP-based long-term corrections which occur if the measurement on-site covers only a few months (seasonal biases). In this context, two common linear MCP methods are tested and compared with regard to accuracy in mean, variance, and turbine energy production – namely, variance ratio (VR) and linear regression with residuals (LR). Wind measurement data from 18 sites with different terrain complexity in Germany are used (measurement heights between 100 and 140 m). Six different reanalysis data sets serve as the reference (long-term) wind data in the MCP calculations. All these reanalysis data sets showed an overpronounced annual course of wind speed (i.e., wind speeds too high in winter and too low in summer). However, despite the mathematical similarity of the two MCP methods, these errors in the data resulted in very different seasonal biases when either the VR or LR methods were used for the MCP calculations. In general, the VR method produced overestimations of the mean wind speed when measuring in summer and underestimations in the case of winter measurements. The LR method, in contrast, predominantly led to opposite results. An analysis of the bias in variance did not show such a clear seasonal variation. Overall, the variance error plays only a minor role for the accuracy in energy compared to the error in mean wind speed. Besides the experimental analysis, a theoretical framework is presented which explains these phenomena. This framework enables us to trace the seasonal biases to the mechanics of the methods and the properties of the reanalysis data sets. In summary, three aspects are identified as the main influential factors for the seasonal biases in mean wind speed: (1) the (dis-)similarity of the real wind conditions on-site in correlation and correction period (representativeness of the measurement period), (2) the capability of the reference data to reproduce the seasonal course of wind speed, and (3) the regression parameter <span class="inline-formula"><i>β</i><sub>1</sub></span> (slope) of the linear MCP method. This theoretical framework can also be considered valid for different measurement durations, other reference data sets, and other regions of the world.</p>
format	article
author	A. Basse A. Basse D. Callies D. Callies A. Grötzner L. Pauscher
author_facet	A. Basse A. Basse D. Callies D. Callies A. Grötzner L. Pauscher
author_sort	A. Basse
title	Seasonal effects in the long-term correction of short-term wind measurements using reanalysis data
title_short	Seasonal effects in the long-term correction of short-term wind measurements using reanalysis data
title_full	Seasonal effects in the long-term correction of short-term wind measurements using reanalysis data
title_fullStr	Seasonal effects in the long-term correction of short-term wind measurements using reanalysis data
title_full_unstemmed	Seasonal effects in the long-term correction of short-term wind measurements using reanalysis data
title_sort	seasonal effects in the long-term correction of short-term wind measurements using reanalysis data
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/bc7775ee1e2d4c98927c8d47be5b4fe8
work_keys_str_mv	AT abasse seasonaleffectsinthelongtermcorrectionofshorttermwindmeasurementsusingreanalysisdata AT abasse seasonaleffectsinthelongtermcorrectionofshorttermwindmeasurementsusingreanalysisdata AT dcallies seasonaleffectsinthelongtermcorrectionofshorttermwindmeasurementsusingreanalysisdata AT dcallies seasonaleffectsinthelongtermcorrectionofshorttermwindmeasurementsusingreanalysisdata AT agrotzner seasonaleffectsinthelongtermcorrectionofshorttermwindmeasurementsusingreanalysisdata AT lpauscher seasonaleffectsinthelongtermcorrectionofshorttermwindmeasurementsusingreanalysisdata
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Seasonal effects in the long-term correction of short-term wind measurements using reanalysis data

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