Calibration of GFS Solar Irradiation Forecasts: A Case Study in Romania

Sergiu-Mihai Hategan, Nicoleta Stefu () and Marius Paulescu
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Sergiu-Mihai Hategan: Faculty of Physics, West University of Timisoara, V. Parvan 4, 300223 Timisoara, Romania
Nicoleta Stefu: Faculty of Physics, West University of Timisoara, V. Parvan 4, 300223 Timisoara, Romania
Marius Paulescu: Faculty of Physics, West University of Timisoara, V. Parvan 4, 300223 Timisoara, Romania

Energies, 2023, vol. 16, issue 11, 1-11

Abstract: Models based on Numerical Weather Prediction (NWP) are widely used for the day-ahead forecast of solar resources. This study is focused on the calibration of the hourly global solar irradiation forecasts provided by the Global Forecast System (GFS), a model from the NWP class. Since the evaluation of GFS raw forecasts sometimes shows a high degree of uncertainty (the relative error exceeding 100%), a procedure for reducing the errors is needed as a prerequisite for engineering applications. In this study, a deep analysis of the error sources in relation to the state of the atmosphere is reported. Of special note is the use of sky imagery in the identification process. Generally, it has been found that the largest errors are determined by the underestimation of cloud coverage. For calibration, a new ensemble forecast is proposed. It combines two machine learning approaches, Support Vector Regression and Multi-Layer Perceptron. In contrast to a typical calibration, the objective function is constructed based on the absolute error instead of the traditional root mean squared error. In terms of normalized root mean squared error, the calibration roughly reduces the uncertainty in hourly global solar irradiation by 16%. The study was conducted with high-quality ground-measured data from the Solar Platform of the West University of Timisoara, Romania. To ensure high accessibility, all the parameters required to run the proposed calibration procedures are provided.

Keywords: solar irradiation; GFS forecast; machine learning; sky imager; calibration (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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