All sky imager (ASI) based nowcasting system can provide spatially and temporally highly resolved solar irradiance information for the next minutes ahead. Nowcasts, which capture the intra-hour variability of the incoming downward shortwave solar irradiance, have the potential to optimize the operation of solar power plants as well as electrical grids. Such automatized optimizations require a deep understanding of the accuracy in the nowcasting system at any given moment. State of the art validation procedures of ASI based nowcasting systems use scalar error metrics without regards to the actual weather conditions. Yet, the performance of nowcasting systems varies strongly with the prevailing weather conditions. Deviations increase for more complex and variable conditions, for which it is more challenging to detect and model the clouds in the sky. Thus, depending on the used data set such validation results may not be meaningful to describe the expected accuracy in realistic and individual optimization situations. A novel validation procedure is presented in this work, which discretizes the validation data set in distinct temporal DNI variability classes. Individual error metrics are determined as function of the lead time and DNI variability class. This approach is applied for a two ASI based nowcasting system as operated on five distinct sites distributed in Spain, Portugal and Germany, over a combined period of more than 4.5 years. The obtained validation results emphasize that the novel classification method enables a comparison in nowcast performance between the sites despite of distinct local meteorological conditions. The presented method allows the estimation of the overall accuracy of nowcasting systems at a new site if DNI data in 1 min resolution are available.
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11 December 2020
SOLARPACES 2019: International Conference on Concentrating Solar Power and Chemical Energy Systems
1–4 October 2019
Daegu, South Korea
Research Article|
December 11 2020
Evaluation of an all sky imager based nowcasting system for distinct conditions and five sites
Bijan Nouri;
Bijan Nouri
a)
1
German Aerospace Center (DLR), Institute of Solar Research
, Ctra de Senes s/n km 4, 04200 Tabernas, Spain
a)Corresponding author: bijan.nouri@dlr.de
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Stefan Wilbert;
Stefan Wilbert
1
German Aerospace Center (DLR), Institute of Solar Research
, Ctra de Senes s/n km 4, 04200 Tabernas, Spain
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Niklas Blum;
Niklas Blum
1
German Aerospace Center (DLR), Institute of Solar Research
, Ctra de Senes s/n km 4, 04200 Tabernas, Spain
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Pascal Kuhn;
Pascal Kuhn
1
German Aerospace Center (DLR), Institute of Solar Research
, Ctra de Senes s/n km 4, 04200 Tabernas, Spain
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Thomas Schmidt;
Thomas Schmidt
2
CSP Services GmbH
, Friedrich-Ebert-Ufer 30, 51143 Cologne, Germany
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Zeyad Yasser;
Zeyad Yasser
3
TSK Flagsol Engineering GmbH
, Anna-Schneider-Steig 10, 50678 Cologne, Germany
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Thomas Schmidt;
Thomas Schmidt
4
DLR, Institute of Networked Energy Systems
, Carl-von-Ossietzky-Straße 15, 26129 Oldenburg, Germany
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Luis F. Zarzalejo;
Luis F. Zarzalejo
5
CIEMAT Energy Department – Renewable Energy Division
, Avda. Complutense 40, 28040 Madrid, Spain
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Francisco M. Lopes;
Francisco M. Lopes
6
Renewable Energy Chair, University of Évora
, Nossa Sra. da Tourega, 7000-083 Valverde, Évora, Portugal
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Hugo G. Silva;
Hugo G. Silva
6
Renewable Energy Chair, University of Évora
, Nossa Sra. da Tourega, 7000-083 Valverde, Évora, Portugal
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Marion Schroedter-Homscheidt;
Marion Schroedter-Homscheidt
4
DLR, Institute of Networked Energy Systems
, Carl-von-Ossietzky-Straße 15, 26129 Oldenburg, Germany
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Andreas Kazantzidis;
Andreas Kazantzidis
7
Laboratory of Atmospheric Physics, Department of Physics, University of Patras
, 26500 Patras, Greece
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Christian Raeder;
Christian Raeder
8
DLR, Institute of Solar Research
, Prof.-Rehm-Str. 1, 52428 Jülich, Germany
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Philippe Blanc;
Philippe Blanc
9
MINES ParisTech
, 06904 Sophia Antipolis CEDEX, France
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Robert Pitz-Paal
Robert Pitz-Paal
10
DLR, Institute of Solar Research
, Linder Höhe, 51147 Cologne, Germany
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a)Corresponding author: bijan.nouri@dlr.de
AIP Conf. Proc. 2303, 180006 (2020)
Citation
Bijan Nouri, Stefan Wilbert, Niklas Blum, Pascal Kuhn, Thomas Schmidt, Zeyad Yasser, Thomas Schmidt, Luis F. Zarzalejo, Francisco M. Lopes, Hugo G. Silva, Marion Schroedter-Homscheidt, Andreas Kazantzidis, Christian Raeder, Philippe Blanc, Robert Pitz-Paal; Evaluation of an all sky imager based nowcasting system for distinct conditions and five sites. AIP Conf. Proc. 11 December 2020; 2303 (1): 180006. https://doi.org/10.1063/5.0028670
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